Fluoroscope

Abstract

To provide a fluoroscope capable of searching for a marker accurately and quickly by appropriately setting a search area for each of X-ray fluoroscopic images acquired continuously.SOLUTION: A fluoroscope includes: a search area setting unit 22 for setting a search area S for each of X-ray fluoroscopic images P; a marker detection unit 21 for searching the inside of the search area S for detecting a marker 10; and a detection object determination unit 23 for determining a detection object F detected as the marker 10. When it is determined that the detection object F in a predetermined first X-ray fluoroscopic image is the marker 10, the search area S is set to a second X-ray fluoroscopic image generated thereafter on the basis of the position of the detection object F. When it is determined that the detection object F of the first X-ray fluoroscopic image is a similar object R, the search area S is set to the second X-ray fluoroscopic image on the basis of the detection object F of a third X-ray fluoroscopic image generated before the first X-ray fluoroscopic image for which it is determined that the detection object is the marker 10.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an X-ray imaging apparatus.

[0002] In medical practice, radiation therapy may be performed by irradiating an affected area, such as a tumor, with radiation, such as X-rays or electron beams. In this case, it is necessary to accurately irradiate the affected area with relatively strong therapeutic radiation. However, the affected area may move due to the subject's breathing or pulsation. In order to accurately irradiate radiation even if the affected area moves, a radiation therapy system has been proposed that uses a marker to track the moving body. In this radiation therapy system, a marker, such as a metal ball, is placed on the tumor or in the vicinity of the tumor, and the position of the marker is identified by an X-ray fluoroscopy device. If the distance between the identified marker position and the coordinates of the treatment plan is within an allowable range, control is performed to irradiate the subject with therapeutic radiation from the radiation therapy device (for example, Patent Document 1).

[0003] An X-ray fluoroscope used in such a radiation therapy system includes a first imaging system including a first X-ray tube and a first X-ray detector, and a second imaging system including a second X-ray tube and a second X-ray detector. The first imaging system and the second imaging system are configured to irradiate X-rays from different directions.

[0004] When calculating the three-dimensional position of a marker, a first imaging system and a second imaging system are used to obtain two-dimensional X-ray fluoroscopic images showing the marker placed inside the subject's body. Then, the marker is searched for in each X-ray fluoroscopic image to obtain two-dimensional position information of the marker. By using the two-dimensional position information of the marker obtained in the X-ray fluoroscopic images taken from different directions, the three-dimensional position information of the marker can be calculated. By continuously performing X-ray fluoroscopy using the first imaging system and the second imaging system, the three-dimensional position of the marker placed in the affected area, which moves, can be detected in real time with high accuracy. The frame rate of the X-ray fluoroscopic image can be 15 frames or 30 frames per second.

[0005] As a method for searching for a marker in a two-dimensional X-ray fluoroscopic image, a method for performing image recognition by template matching using a template image of the marker or machine learning using a classifier has been proposed. In addition, as a method for shortening the time required to detect the two-dimensional position of a marker, a method for setting a search area inside the X-ray fluoroscopic image and searching for the marker within the search area has been proposed.

[0006] That is, when the position of a marker is detected in an X-ray fluoroscopic image, for example, a predetermined range centered on the position of the marker is determined as a search area. Then, the determined search area is set in the X-ray fluoroscopic image acquired in the next frame. By performing a search within the set search area, the position of the marker can be quickly detected in the X-ray fluoroscopic image of the next frame. Then, the position information of the detected marker is reflected in the search area in the next frame. In this way, while continuously acquiring X-ray fluoroscopic images, the position of the search area is successively updated for each X-ray fluoroscopic image. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-170884 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the conventional example having such a configuration has the following problems.

[0009] When a search area is set in an X-ray fluoroscopic image and the search for a marker is limited to within that search area, there is a concern that as more and more X-ray fluoroscopic images are acquired, the search area will no longer be set in an appropriate position, making it difficult to detect the position of the marker.

[0010] The causes of such problems are considered to be as follows. That is, in addition to the true marker to be tracked, an X-ray fluoroscopic image may show an object similar to the marker but different from the tracked object (hereinafter referred to as a "similar object"). Then, among the X-ray fluoroscopic images acquired continuously, the similar object may be detected as the marker instead of the true marker in the X-ray fluoroscopic image of a predetermined frame.

[0011] When a similar object is detected as a marker instead of a genuine marker, a search area is set in an inappropriate range based on the position of the similar object in the X-ray fluoroscopic image related to the next frame of the specified frame. In other words, when a search area is set based on the position of a similar object, the position of the search area is set so as to track the similar object in the X-ray fluoroscopic images acquired continuously thereafter, so that the possibility that the genuine marker is located outside the search area gradually increases. As a result, the genuine marker is no longer included in the search area in the X-ray fluoroscopic images related to the subsequent frames, making it difficult to search for the genuine marker.

[0012] The present invention has been made in consideration of the above circumstances, and aims to provide an X-ray fluoroscopy device that can accurately and quickly search for markers by appropriately setting a search area for each of the continuously acquired X-ray fluoroscopy images. [Means for solving the problem]

[0013] In order to achieve the above object, the present invention has the following configuration. That is, a first aspect of the present invention includes an X-ray tube which irradiates an object with X-rays, an X-ray detector which detects the X-rays which have passed through the object, an image generating unit which generates a plurality of X-ray fluoroscopic images including a marker placed inside the object or a specific portion of the object using a detection signal output by the X-ray detector, a search area setting unit which sets a search area for each of the plurality of X-ray fluoroscopic images, a tracking target detection unit which detects the marker or the specific portion as a tracking target by searching inside the search area set in each of the X-ray fluoroscopic images, and a detection target determination unit which determines whether a detection target detected as the tracking target by the tracking target detection unit in each of the plurality of X-ray fluoroscopic images is the tracking target or a target different from the tracking target, the X-ray fluoroscopy images include a first X-ray fluoroscopy image, a second X-ray fluoroscopy image generated at a time later than the first X-ray fluoroscopy image, and a third X-ray fluoroscopy image generated at a time earlier than the first X-ray fluoroscopy image and in which the detection target determination unit has determined that the detection target is the tracking target, and the search area setting unit sets the search area in the second X-ray fluoroscopy image based on position information of the detection target in the first X-ray fluoroscopy image when the detection target determination unit has determined that the detection target in the first X-ray fluoroscopy image is the tracking target, and sets the search area in the second X-ray fluoroscopy image based on position information of the detection target in the third X-ray fluoroscopy image when the detection target determination unit has determined that the detection target in the first X-ray fluoroscopy image is an object different from the tracking target.

[0014] A second aspect of the present invention includes an X-ray tube which irradiates an object with X-rays, an X-ray detector which detects X-rays transmitted through the object, an image generating unit which generates a plurality of X-ray fluoroscopic images using a detection signal output by the X-ray detector, a search area setting unit which sets a search area for each of the plurality of X-ray fluoroscopic images, a tracking target detecting unit which detects a marker placed inside the body of the object or a specific portion of the object as a tracking target by searching inside the search area set in each of the X-ray fluoroscopic images, and The present invention relates to an X-ray fluoroscopy device comprising: a frame-out detection unit that detects the occurrence of a frame-out state, in which the tracked target is located outside an X-ray fluoroscopy image; and a tracked target return detection unit that detects the occurrence of a tracked target return state, in which the tracked target returns from outside the X-ray fluoroscopy image to the inside, wherein when the frame-out state is detected, the search area setting unit sets the search area based on position information of the tracked target detected in the X-ray fluoroscopy image generated at the time the frame-out state was detected, until the tracked target return state is detected. Effect of the Invention

[0015] In the X-ray fluoroscopy apparatus according to the first aspect of the present invention, the tracking target detection unit detects a marker or a specific portion, which is a tracking target, from the X-ray fluoroscopy image by searching inside a search area. The detection target determination unit determines whether a detection target detected as a tracking target by the tracking target detection unit in each of a plurality of X-ray fluoroscopy images is a tracking target or an object different from the tracking target. When the detection target determination unit determines that the detection target in the first X-ray fluoroscopy image is a tracking target, the search area setting unit sets a search area for a second X-ray fluoroscopy image generated at a time later than the first X-ray fluoroscopy image based on position information of the detection target in the first X-ray fluoroscopy image. When the detection target determination unit determines that the detection target in the first X-ray fluoroscopy image is an object different from the tracking target, the search area setting unit sets the search area for the second X-ray fluoroscopy image based on position information of the detection target in the third X-ray fluoroscopy image. The third X-ray fluoroscopy image is an image generated at a time earlier than the first X-ray fluoroscopy image and in which the detection target is determined to be a tracking target. With this configuration, even if the tracking target detection unit detects an object other than the tracking target, it is possible to avoid updating the search area to track the non-tracking target. Therefore, it is possible to appropriately set the search area according to the position of the tracking target without being affected by the non-tracking target, and to accurately track the tracking target, e.g., a marker.

[0016] The X-ray fluoroscopy apparatus according to the second aspect of the present invention includes a frame-out detection unit that detects the occurrence of a frame-out state in which a part of a search area set in an X-ray fluoroscopy image is located outside the X-ray fluoroscopy image, and a marker return detection unit that detects the occurrence of a tracked target return state in which the tracked target returns from the outside to the inside of the X-ray fluoroscopy image. When the frame-out state is detected, the search area is set based on the position information of the tracked target detected from the X-ray fluoroscopy image generated at the time when the frame-out state is detected until the tracked target return state is detected. With this configuration, when the marker moves outside the X-ray fluoroscopy image, the occurrence of the frame-out state is quickly detected and the area is shifted to a fixed state. Therefore, it is possible to prevent a non-tracked target from being detected as a tracked target due to the marker moving outside the X-ray fluoroscopy image and a search area from being set at an inappropriate position based on the position of the non-tracked target. Therefore, even if the marker temporarily moves outside the X-ray fluoroscopy image due to the subject's body movement or the like, it is possible to appropriately set the search area and accurately track the tracked target, e.g., the marker. [Brief description of the drawings]

[0017] [Figure 1] 1 is a perspective view illustrating an overall configuration of an X-ray fluoroscope according to a first embodiment. [Diagram 2] 1 is a functional block diagram illustrating a configuration of an X-ray fluoroscope according to a first embodiment. [Diagram 3] 4 is a flowchart illustrating a basic operation of the X-ray fluoroscope according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating step S1 according to the first embodiment. [Diagram 5] FIG. 11 is a diagram illustrating step S2 according to the first embodiment. [Figure 6] FIG. 11 is a diagram illustrating step S3 according to the first embodiment. [Figure 7] 1A to 1C are diagrams illustrating a state in which a similar object is detected from an X-ray fluoroscopic image. [Figure 8]FIG. 13 is a diagram showing a state in which a search area is updated based on a similar object in a conventional configuration. [Figure 9] 11 is a flowchart illustrating details of step S5 according to the first embodiment. [Figure 10] FIG. 11 is a diagram illustrating step S501 according to the first embodiment. [Figure 11] FIG. 11 is a diagram illustrating step S502 according to the first embodiment. [Figure 12] FIG. 11 is a diagram illustrating step S503 according to the first embodiment. [Figure 13] FIG. 11 is a diagram illustrating step S504 according to the first embodiment. [Figure 14] FIG. 13 is a diagram illustrating a trajectory along which a marker moves. [Figure 15] 11 is a flowchart illustrating details of step S4 according to the first embodiment. [Figure 16] 4A to 4C are diagrams illustrating a moving distance and a moving vector of a detection object in the first embodiment. [Figure 17] 13A to 13C are diagrams illustrating a case where the detection object is determined to be a marker in step S404 according to the first embodiment. [Figure 18] 13A to 13C are diagrams illustrating a case where a detection target is determined to be a similar target in step S404 according to the first embodiment. [Figure 19] 13A to 13C are diagrams illustrating a case where the detection object is determined to be a marker in step S405 according to the first embodiment. [Figure 20] 13A to 13C are diagrams illustrating a case where a detection target is determined to be a similar target in step S405 according to the first embodiment. [Figure 21] FIG. 13 is a diagram showing a state in which a search area is expanded and updated in step S5 according to the first embodiment. [Figure 22] FIG. 11 is a functional block diagram illustrating the configuration of an X-ray fluoroscope according to a second embodiment. [Diagram 23] 10 is a flowchart illustrating a basic operation of the X-ray fluoroscope according to the second embodiment. [Figure 24]10 is a flowchart illustrating details of step S4 according to the second embodiment. [Diagram 25] 10 is a flowchart illustrating details of step S5 according to the second embodiment. [Figure 26] FIG. 11 is a diagram illustrating a state in which a part of a search area is set outside an X-ray fluoroscopic image in the second embodiment. [Figure 27] FIG. 1 is a diagram for explaining problems in a conventional configuration. [Figure 28] FIG. 1 is a diagram for explaining problems in a conventional configuration. [Figure 29] FIG. 11 is a diagram illustrating an area fixed state in the second embodiment. [Diagram 30] 13A and 13B are diagrams illustrating a modified example of the area fixed state in the second embodiment. [Diagram 31] 13A and 13B are diagrams illustrating a modified example of the area fixed state in the second embodiment. [Diagram 32] FIG. 11 is a diagram illustrating step S5 in the second embodiment. [Diagram 33] 13 is a diagram for explaining the relationship between the position of a marker moving to the outside of an X-ray fluoroscopic image and the position of a marker moving to the inside of the X-ray fluoroscopic image in the second embodiment. FIG. [Diagram 34] FIG. 1 is a functional block diagram illustrating a configuration of an X-ray fluoroscope having configurations according to a first embodiment and a second embodiment. [Diagram 35] 10 is a flowchart illustrating a basic operation of an X-ray fluoroscope according to a modified embodiment. [Diagram 36] 11 is a flowchart illustrating step S405 in the first embodiment. [Figure 37] 13 is a flowchart illustrating step S406 in the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [First embodiment] A first embodiment of the present invention will now be described with reference to the drawings. An X-ray fluoroscope 1 according to the first embodiment constitutes a radiation therapy system together with a therapeutic radiation irradiation device (not shown).

[0019] <Overall configuration> 1, the X-ray fluoroscope 1 according to the first embodiment includes a tabletop 3, a base 4, a first X-ray tube 5, a first X-ray detector 6, a second X-ray tube 7, and a second X-ray detector 8. The tabletop 3 is for placing a subject M thereon, and is supported by a base 4 arranged on a floor surface. The base 4 is configured to be movable up and down, and the position of the tabletop 3 in the z direction is adjusted by the base 4 moving up and down. The tabletop 3 is also configured to be horizontally movable in the x direction (the long side direction of the tabletop 3) and the y direction (the short side direction of the tabletop 3) by a tabletop drive unit (not shown).

[0020] The first X-ray tube 5 and the second X-ray tube 7 irradiate the subject M with X-rays from different directions. The first X-ray detector 6 is disposed facing the first X-ray tube 5 across the top plate 3. The first X-ray detector 6 detects the X-rays irradiated from the first X-ray tube 5 and converts them into an electrical signal. The first X-ray tube 5 and the first X-ray detector 6 constitute a first imaging system L1. The second X-ray detector 8 is disposed facing the second X-ray tube 7 across the top plate 3. The second X-ray detector 8 detects the X-rays irradiated from the second X-ray tube 7 and converts them into an electrical signal. The second X-ray tube 7 and the second X-ray detector 8 constitute a second imaging system L2. An example of the first X-ray detector 6 and the second X-ray detector 8 is an FPD (Flat Panel Detector).

[0021] A marker 10 is placed in advance inside the body of the subject M. The marker 10 is made of an X-ray opaque material such as metal, for example, and is placed in the affected area or near the affected area of ​​the subject M. In this embodiment, various processes are performed with the marker 10 as a tracking target.

[0022] 2, the X-ray fluoroscope 1 further includes a main controller 9, a display unit 11, an input unit 13, and a storage unit 15. The main controller 9 includes information processing means such as a central processing unit (CPU) and generally controls various components in the X-ray fluoroscope 1. The main controller 9 is connected to each component such as a first imaging system L1 and a second imaging system L2.

[0023] As shown in Figure 2, the main control unit 9 includes an X-ray irradiation control unit 17, an image generation unit 19, a marker detection unit 21, a search area setting unit 22, a detection target determination unit 23, a search area update unit 25, a marker position calculation unit 26, a movement vector calculation unit 27, an average distance calculation unit 28, and a movement state determination unit 29.

[0024] The X-ray irradiation control unit 17 is configured to independently control each of the first X-ray tube 5 and the second X-ray tube 7. The X-ray irradiation control unit 17 is configured to output a high voltage to each of the first X-ray tube 5 and the second X-ray tube 7. Based on the high voltage output output under the control of the X-ray irradiation control unit 17, the amount of X-rays irradiated by each of the first X-ray tube 5 and the second X-ray tube 7 and the timing of irradiating X-rays are controlled.

[0025] The image generating unit 19 performs various image processing based on the X-ray detection signals output from each of the first X-ray detector 6 and the second X-ray detector 8 to generate an X-ray fluoroscopic image P. The image generating unit 19 continuously generates a plurality of X-ray fluoroscopic images P in accordance with the timing at which X-rays are continuously emitted from each of the first X-ray tube 5 and the second X-ray tube 7.

[0026] Among the multiple X-ray fluoroscopic images P that are successively generated, the first X-ray fluoroscopic image generated in each imaging system is designated as X-ray fluoroscopic image P1, and the m-th X-ray fluoroscopic image generated in each imaging system is designated as X-ray fluoroscopic image P m In this embodiment, the most recently generated X-ray fluoroscopic image is referred to as "X-ray fluoroscopic image P n" In other words, the X-ray fluoroscopic image P n The most recently generated X-ray fluoroscopic image is called "X-ray fluoroscopic image P n-1 " and X-ray fluoroscopic image P n-1 The most recently generated X-ray fluoroscopic image is called "X-ray fluoroscopic image P n-2 " And the X-ray fluoroscopic image P n The next X-ray fluoroscopic image to be generated is called "X-ray fluoroscopic image P n+1 " shall be marked with the symbol "

[0027] The marker detection unit 21 detects the marker 10 reflected in the X-ray fluoroscopic image P by scanning the X-ray fluoroscopic image P. In this embodiment, the marker detection unit 21 searches for the marker 10 by a template matching method. That is, an image of the marker 10 is acquired in advance as a template image Tp. The marker detection unit 21 searches the X-ray fluoroscopic image P by referring to the image of the marker 10 reflected in the template image Tp. Then, the marker detection unit 21 detects from the X-ray fluoroscopic image P an object having the highest similarity (matching score) to the marker 10 in the template image Tp.

[0028] Here, the target detected by the marker detection unit 21 as the marker 10 from each of the X-ray fluoroscopic images P is referred to as a "detection target F." m Regarding the detection target F detected by the marker detection unit 21, m " to distinguish it from the detection target F detected from another X-ray fluoroscopic image P. Note that the method by which the marker detection unit 21 detects the marker 10 from the X-ray fluoroscopic image P is not limited to template matching, and any appropriate method such as a machine learning method using a classifier may be used.

[0029] In addition, when the marker detection unit 21 detects the detection target F, the marker detection unit 21 obtains information on the position of the detection target F as the detection target position B. m The detection target F detected from m For the position information of the detection target position B m" to distinguish it from detection target position B in another fluoroscopic X-ray image P. In this embodiment, the marker detection unit 21 corresponds to a tracking target detection unit.

[0030] The search area setting unit 22 sets a search area S in each of the X-ray fluoroscopic images P, as shown in FIG. 5 and other figures. The search area S is set as a range in the X-ray fluoroscopic image P within which the marker 10 may move. The marker detection unit 21 scans the internal region of the search area S in the X-ray fluoroscopic image P. By limiting the region scanned by the marker detection unit 21 to the inside of the search area S, rather than the entire X-ray fluoroscopic image P, the detection process for the marker 10 can be shortened. Note that in the m-th generated X-ray fluoroscopic image P m For the search area S set in m " to distinguish it from the search area S detected from other X-ray fluoroscopic images P.

[0031] The detection target determination unit 23 determines whether a detection target F detected by scanning the X-ray fluoroscopic image P is a genuine marker 10 or a similar target R. The similar target R is an object that is similar to the marker 10 but different from the marker 10. In other words, the genuine marker 10 is a tracked target, whereas the similar target R is a non-tracked target. Examples of the similar target R include a metal object different from the marker 10, or noise. The process by which the detection target determination unit 23 determines each of the detection targets F will be described later. The detection target determination unit 23 determines whether the detection target F is a genuine marker 10 or a similar target R. n When the X-ray fluoroscopic image P n The detection target F detected from n It is determined whether the marker 10 is a genuine marker or a similar object R.

[0032] The search area update unit 25 updates information on the search area S set in the X-ray fluoroscopic image P based on the result of the detection target determination unit 23's determination on the detection target F. Examples of the information on the search area S updated by the search area update unit 25 include position information on the search area S in the X-ray fluoroscopic image P and information on the size of the search area S. The search area setting unit 22 sets the search area S for the X-ray fluoroscopic image P to be generated subsequently based on the information updated by the search area update unit 25. The information on the search area S updated by the search area update unit 25 is stored in a search area storage unit 34 described later.

[0033] The marker position calculation unit 26 calculates the position of the marker 10 in three-dimensional space using the first X-ray fluoroscopic image P acquired by the first imaging system L1 and the second X-ray fluoroscopic image P acquired by the second imaging system L2. The first X-ray fluoroscopic image P and the second X-ray fluoroscopic image P have different X-ray irradiation directions. Therefore, based on the position information of the marker 10 in the two two-dimensional images, three-dimensional position information of the marker 10 in the subject M can be obtained.

[0034] The motion vector calculation unit 27 acquires information on the movement distance G and the movement direction H of the detection target F for each of the X-ray fluoroscopic images P. The motion vector calculation unit 27 also calculates a motion vector V of the detection target F in the X-ray fluoroscopic image P from the information on the movement distance G and the information on the movement direction H in the X-ray fluoroscopic image P. m Detection target F m The moving distance G, moving direction H, and moving vector V of m ”, “Movement direction H m ", "Movement vector V m " to distinguish it from the moving distance G, moving direction H, and moving vector V of the other detection target F.

[0035] A motion vector V of the detection object F in the X-ray fluoroscopic image P is calculated based on a moving distance G and a moving direction H of the detection object F between two X-ray fluoroscopic images P. In other words, the motion vector V is calculated based on a moving distance and a moving direction of the detection object F between a predetermined frame.

[0036] As an example, X-ray fluoroscopy image P m Detection target F m Distance traveled by G m X-ray fluoroscopic image P m and the X-ray fluoroscopic image P m X-ray fluoroscopic image P generated at an earlier time m-a This corresponds to the distance that the detection target F has moved between the X-ray fluoroscopic image P m-a is the detection target F m-a is the X-ray fluoroscopic image P that is determined to be a genuine marker 10.

[0037] Detection target F m-1 is determined to be a marker 10 by the detection object determination unit 23, the X-ray fluoroscopic image P m-1 and X-ray fluoroscopic image P m The distance that the detection target F moved between m Distance traveled by G m In this case, the detection target F m Distance traveled by G m is an X-ray fluoroscopic image P m-1 Detection target F m-1 Position and X-ray fluoroscopic image P m Detection target F m This corresponds to the distance between the position of

[0038] In addition, the detection target F m-1 is judged to be a similar target R, while the detected target F m-2 When it is determined that the marker 10 is a marker, the X-ray fluoroscopic image P m-2 and X-ray fluoroscopic image P m The distance that the detection target F moved between m Distance traveled by G m In this case, the detection target F m Distance traveled by Gm is the detection target F m-2 Position of and detection target F m This corresponds to the distance between the position of

[0039] The average distance calculation unit 28 calculates the average value of the movement distance of the marker 10 in the recent past as the average movement distance G av The average distance calculation unit 28 selects a predetermined number of pieces of data on the moving distance G from among the pieces of data on the moving distance G that have already been calculated. Then, the average value of the data on the selected moving distance G is calculated as the average moving distance G. av The number of pieces of data of the moving distance G selected by the average distance calculation unit 28 may be changed as appropriate. In this embodiment, the average moving distance G is calculated from the data of four moving distances G. av As an example, the detection object F m Distance traveled by G m The average travel distance G corresponding to av When calculating, the distance traveled G, which corresponds to the distance traveled in the recent past, m-1 ~G m-4 It is preferable to select data of 100 to 150 and calculate the average value.

[0040] The data of the moving distance G selected by the average distance calculation unit 28 is limited to the moving distance of the detection object F that is determined to be the marker 10. m-1 ~F m-3 When all of the detection objects F are determined to be markers 10 by the detection object determination unit 23, m-2 From detection target F m-1 Distance traveled to G m-1 , and the detection target F m-3 From detection target F m-2 Distance traveled to G m-2 The data corresponds to the distance traveled by the marker 10. Therefore, the travel distance G m-1 and the travel distance G m-2 This data becomes a selection target for the average distance calculation unit 28.

[0041] On the other hand, the detection target F m-3 is determined to be a similar object R by the detection object determination unit 23, the detection object Fm-3 From detection target F m-2 Distance traveled to G m-2 Since the data does not correspond to the distance traveled by the marker 10, it is not selected by the average distance calculation unit 28. By selecting the travel distance G between the detection objects F determined to be the marker 10 in this way and calculating the average, the average distance calculation unit 28 calculates the average travel distance G of the marker 10. av can be calculated.

[0042] The movement state determination unit 29 determines the movement state of the detection target F shown in the X-ray fluoroscopic image P. That is, the movement state determination unit 29 determines whether the detection target F shown in the X-ray fluoroscopic image P is in a high-speed movement state or a low-speed movement state based on the information of the movement distance G acquired by the movement vector calculation unit 27. Details of the criteria and steps by which the movement state determination unit 29 determines the movement state of the detection target F will be described later. In this embodiment, the similar target determination unit is configured to change the criteria for determining the detection target F depending on the result of the determination by the movement state determination unit 29.

[0043] The display unit 11 displays various information related to the X-ray fluoroscopy apparatus 1, various parameter information related to X-ray fluoroscopy, or the X-ray fluoroscopic image P generated by the image processing unit 19. Examples of the display unit 11 include a liquid crystal monitor or a high-precision display.

[0044] The input unit 13 is used to input instructions from an operator regarding the operation of the X-ray fluoroscope 1, and the main control unit 9 performs various controls according to the instructions input by the surgeon to the input unit 13. Examples of operation devices disposed in the input unit 13 include a keyboard input panel, a touch input panel, a mouse, and a switch.

[0045] The storage unit 15 stores the X-ray fluoroscopic image P generated by the image generation unit 19, information related to image processing by the image processing unit 19, various information related to the operation of the X-ray fluoroscopy apparatus 1, and the like. The stored information is read out as needed and output to the display unit 11 and the like via the main control unit 9. The storage unit 15 is composed of a storage medium such as a non-volatile memory.

[0046] 2, the storage unit 15 includes a template storage unit 31, a genuine marker storage unit 33, and a search area storage unit 34. The template storage unit 31 stores in advance a template image Tp which is a basic image in which the marker 10 appears.

[0047] The authentic marker storage unit 33 stores the position information of the detection object F that was most recently determined to be an authentic marker according to the determination result of the detection object determination unit 23. n When the detection object determination unit 23 determines that the marker 10 is a genuine marker, the position information stored in the genuine marker storage unit 33 is the detection object F n The position information of the detection target position B n The latest detection target F n When the detection target determination unit 23 determines that the target is a similar target, the information of the detection target position B stored in the genuine marker storage unit 33 is maintained without being updated.

[0048] The information on the detection target position B stored in the genuine marker storage unit 33 is used as information on the reference position of the search area S set by the search area setting unit 22. The reference position is used as a reference for determining the position of the search area S in the X-ray fluoroscopic image P. In this embodiment, the search area update unit 25 updates the information on the search area S to be set next, with the range centered on the reference position.

[0049] The search area storage unit 34 stores information on the search area S to be set next. Examples of the stored information on the search area S include information on the shape and size of the search area S, or information on the position of the search area S in the X-ray fluoroscopic image P. The information on the search area S stored in the search area storage unit 34 is updated by the search area update unit 25. Furthermore, the search area setting unit 22 uses the information on the search area S stored in the search area storage unit 34 to set the search area S in the X-ray fluoroscopic image P to be generated subsequently.

[0050] <Explanation of basic operation> Here, a basic operation of the X-ray fluoroscopy apparatus 1 according to the first embodiment will be described. In this embodiment, the marker 10 is tracked by performing X-ray fluoroscopy using the X-ray fluoroscopy apparatus 1. FIG. 3 is a flowchart showing an outline of the process of tracking the marker 10 using the X-ray fluoroscopy apparatus 1 according to the first embodiment. In summary, in X-ray fluoroscopy, X-ray fluoroscopy images P are continuously acquired at a frame rate of about 30 fps, for example, and steps S1 to S6 are repeated every time an X-ray fluoroscopy image P is acquired, thereby intermittently identifying the position of the marker 10. Here, steps S1 to S6 are repeated (n-1) times, and a case where the nth step is executed will be described as an example.

[0051] Step S1 (Generation of X-ray fluoroscopic images) First, the subject M, in whom the marker 10 has been placed beforehand, is placed on the tabletop 3, and X-ray fluoroscopy is performed using the first imaging system L1 and the second imaging system L2. Two X-ray fluoroscopic images P, which are taken from different directions by the two imaging systems with different X-ray irradiation directions, are generated by the image generating unit 19. Fig. 4 is a schematic diagram showing the X-ray fluoroscopic image P acquired in step S1. It is assumed that the X-ray fluoroscopic image P includes the marker 10, which is the tracking target, as well as a similar target R, which is not to be tracked.

[0052] When the X-ray fluoroscopic image P is generated, the following steps S2 to S6 are performed for each of the two newly generated X-ray fluoroscopic images P. In the following description, the X-ray fluoroscopic image P generated by the first imaging system L1 is described. In this case, X-ray fluoroscopy is performed n times, and the nth X-ray fluoroscopic image P n The following description will be given as an example of the case where the most recently generated X-ray fluoroscopic image P1 is the first generated X-ray fluoroscopic image. n-1 Assume that all of the detection targets F detected by the marker detection unit 21 are genuine markers 10. In this case, the most recent X-ray fluoroscopic image P n-1 The detected object F n-1 Position of detection target position B n-1) corresponds to the most recent position of the marker 10. Therefore, the true marker memory unit 33 stores the detection target position B n-1 The search area storage unit 34 stores information on the detection target position B n-1 Information on a search area S centered on is stored.

[0053] Step S2 (Setting the search area) When a new fluoroscopic X-ray image P is generated, a search area S is set for the latest fluoroscopic X-ray image P. When step S2 starts, the search area setting unit 22 sets a search area S for the fluoroscopic X-ray image P based on the information stored in the search area storage unit 34. Here, the latest fluoroscopic X-ray image P is the fluoroscopic X-ray image P. n Therefore, the search area setting unit 22 sets the X-ray fluoroscopic image P n Search Area S n Set.

[0054] The search area setting unit 22 sets a search area S based on the most recently acquired position information of the marker 10. n X-ray fluoroscopic image P generated before n In the detection target F n-1 It has been determined that the marker 10 is genuine. Therefore, the position information of the detection target F that was most recently determined to be a genuine marker 10 is the detection target position B n-1 Since the information is n-1 The information is stored in the genuine marker storage unit 33. The search area storage unit 34 stores the detection target position B n-1 The information of the next search area to be set is stored with this as the reference position.

[0055] In this embodiment, the search area S stored in the search area storage unit 34 is a rectangular area centered on the position of the most recently acquired marker 10. n The search area S is set to n As shown in Figure 5, the detection target position B n-1It should be noted that the width W and height Q of the search area S are appropriately set according to, for example, the maximum movement distance of the marker 10 during one frame. In this case, the search area S is set as a range within which the marker 10 may move during one frame.

[0056] Step S3 (Search for marker) When the search area S is set in the X-ray fluoroscopic image P, the marker detection unit 21 searches for the marker 10 in the X-ray fluoroscopic image P. In this embodiment, the marker detection unit 21 searches for the marker 10 using a template matching method. That is, the marker detection unit 21 refers to the image of the marker 10 reflected in the template image Tp and scans the inside of the search area S in the X-ray fluoroscopic image P. Then, the marker detection unit 21 searches for an object having a high similarity to the marker 10 in the template image Tp in the search area S. Then, by searching for the marker 10 in the search area S, the marker detection unit 21 detects an object determined to have the highest similarity to the marker 10. That is, the marker detection unit 21 scans the inside of the search area S to detect the detection object F.

[0057] When detecting the detection target F, the marker detection unit 21 acquires information on the position of the detection target F as the detection target position B. In this case, the marker detection unit 21 acquires information on the position of the detection target F as the detection target position B. n Search area S set to n By scanning the detection object F n is detected and the detection target position B n When detecting the detection target F, information on the similarity between the marker 10 in the template image Tp and the detection target F is stored in the storage unit 15 as a matching score C. That is, the similarity between the marker 10 in the template image Tp and the detection target F is n The similarity information with the matching score C n is stored in the storage unit 15.

[0058] Step S4 (detection target determination) In many cases, the detection target F detected by the marker detection unit 21 as the marker 10 from the X-ray fluoroscopic image P is actually the genuine marker 10. When the detection target F is the genuine marker 10, the tracking of the marker 10 can be appropriately continued by setting a search area S in the X-ray fluoroscopic image P of the next frame with the detection target F as a reference (here, the center). However, on the other hand, as shown in Fig. 7, the marker detection unit 21 may detect a similar target R as the marker 10. That is, the detection target F detected by the marker detection unit 21 may actually be the similar target R and not the marker 10.

[0059] Detection target F n If R is a similar object, the next generated X-ray fluoroscopic image P n+1 For detection target F n Search area S centered on n+1 When you set the search area S as shown in Figure 8. n+1 is set with the similar object R at the center. In this case, the X-ray fluoroscopic image P n+1 In the search area S, the genuine marker 10 n+1 If the marker 10 moves out of the search area S, the X-ray fluoroscopic image P n+1 Therefore, the frequency with which the similar target R is detected by the marker detection unit 21 increases, and as a result, it becomes difficult to appropriately track the marker 10 in the subsequently acquired X-ray fluoroscopic image P. In this way, if the detection target F detected by a technique such as template matching is used as it is as the reference position of the search area S to be set next, there is a concern that the tracking accuracy of the marker 10 may decrease because the detection target F is the similar target R.

[0060] Therefore, in this embodiment, when the marker detection unit 21 detects the detection target F from the X-ray fluoroscopic image P, step S4 is started and the detection target determination unit 23 determines the detection target F. The detection target determination unit 23 determines whether the detection target F corresponds to the genuine marker 10 or the similar target R. The detection target determination unit 23 determines the detection target F based on the movement mode of the detection target F. Details of the criteria and method used by the detection target determination unit 23 to determine the detection target F will be described later. Information obtained by the determination of the detection target determination unit 23, regarding whether the detection target F corresponds to the genuine marker 10 or the similar target R, is transmitted to the search area update unit 25.

[0061] Step S5 (update search area) When the detection target F is determined by the detection target determination unit 23, the information of the search area S is updated based on the result of the determination. That is, the search area update unit 25 updates the information of the next generated X-ray fluoroscopic image P n+1 The search area S set for n+1 Determine the information.

[0062] 9 is a flowchart for explaining the details of step S5. When step S5 is started, the operation of the search area update unit 25 and the like is branched (branch Q1) depending on the result of the detection target F judged by the detection target judgement unit 23 in step S4. That is, the process of step S5 branches depending on the judgment result as to whether the detection target F is the marker 10, which is a tracked target, or a similar target R, which is a non-tracked target.

[0063] 10 and 11 are diagrams for explaining step S5 in the case where the detection object F is determined to be a genuine marker 10. As shown in the upper diagram of FIG. n If the genuine marker 10 is detected by the marker detection unit 21, the detection object determination unit 23 determines the detection object F in step S4. n It is determined that the marker 10 is genuine. n Detection target F nis determined to be a genuine marker 10, the latest position information of the marker 10 is the detection target position B n Therefore, as shown in the lower diagram of FIG. 10, the information stored in the genuine marker storage unit 33 is the detection target position B n-1 to detection target position B n (Step S501). n is an X-ray fluoroscopic image P n In the detection target F n This corresponds to the position where (Marker 10) is shown.

[0064] The search area update unit 25 determines the position and size of the search area S to be set in the next generated X-ray fluoroscopic image P, using the information on the detection target position B stored in the genuine marker storage unit 33 as the reference position. n If it is determined that the marker 10 is genuine, the information stored in the genuine marker memory unit 33 is the detection target position B n Therefore, the search area update unit 25 updates the detection target position B n The information of the next search area S is updated with the reference position. That is, the X-ray fluoroscopic image P n+1 The search area set in is the detection target position B n-1 Search area S centered on n From the detection target position B n Search area S centered on n+1 As a result, the information stored in the search area storage unit 34 is updated to the search area S n From search area S n+1 (Step S502). The process of step S5 is completed when the information of the search area S is updated. n corresponds to the first X-ray fluoroscopy image, and the X-ray fluoroscopy image P n+1 corresponds to the second X-ray fluoroscopic image.

[0065] 12 and 13 are diagrams for explaining step S5 in the case where the detection target F is determined to be a similar target R. As shown in the upper diagram of FIG. nWhen a similar object R is detected from the target object F, the detection object determination unit 23 n is judged to be a similar object R. X-ray fluoroscopic image P n Detection target F n is determined to be a similar target R, the position information of the most recently detected marker 10 is the detected target position B n Detection target position B n-1 Therefore, as shown in the lower diagram of FIG. 12, the information stored in the genuine marker storage unit 33 is the detection target position B n-1 (step S503).

[0066] In this case, the search area update unit 25 updates the detection target position B n-1 The next search area S is set as the reference position. n+1 That is, as shown in FIG. 13, the next generated X-ray fluoroscopic image P n+1 The search area S is set to n+1 The position of the detection target position B n-1 Search area S centered on n As a result, the information stored in the search area storage unit 34 is not updated, and the search area S n The information is maintained as above (step S504).

[0067] In this way, the detection target F n If it is determined to be a similar object R, the detected object position B n The position information of the detection target F that was most recently determined to be a genuine marker 10 (here, the detection target position B n-1 ), the information of the next search area S to be set is updated. That is, the detection target F n is determined to be a similar object R, the position of the search area S does not change before and after the update. In this case, the position information of the similar object R does not affect the update of the search area S, so it is possible to avoid a situation in which the genuine marker 10 falls outside the updated search area S due to the position of the search area S being updated to track the similar object R. The process of step S5 ends when the information of the search area S is updated.

[0068] Step S6 (calculation of three-dimensional position) The process of steps S1 to S5 is performed for each of the X-ray fluoroscopic images P acquired by the first imaging system L1 and the X-ray fluoroscopic images P acquired by the second imaging system L2. When the detection object F is determined to be a genuine marker 10, the position of the marker 10 is identified in each of the X-ray fluoroscopic images P.

[0069] When the position of the marker 10 is identified in the X-ray fluoroscopic image P, the three-dimensional position of the marker 10 is calculated. That is, the marker position calculation unit 26 calculates the three-dimensional position of the marker 10 using the two X-ray fluoroscopic images P acquired by the first imaging system L1 and the second imaging system L2. Since the two X-ray fluoroscopic images P have different X-ray irradiation directions, the three-dimensional position information of the marker 10 can be acquired from the two-dimensional position information of the marker 10 in each X-ray fluoroscopic image P. Note that the process of step S6 is not limited to being performed after step S5, and may be performed before step S5.

[0070] If the distance between the calculated three-dimensional position of the marker 10 and the three-dimensional coordinates determined by the prior treatment plan is within an acceptable range, therapeutic radiation is irradiated to the subject M from a treatment device provided in a therapeutic radiation irradiation apparatus (not shown).

[0071] Through steps S1 to S6, the X-ray fluoroscopic image P n A series of steps for tracking the marker 10 is then completed. After that, steps S1 to S6 are performed again, and the X-ray fluoroscopic image P n+1 In other words, in the n-th step S5, the search area S n+1 After the (n+1)th step S1 is started, and the X-ray fluoroscopic image P n+1 Then, the X-ray fluoroscopic image P n+1 When the (n+1)th step S2 is started, the previously updated search area S n+1 Based on the information of X-ray fluoroscopy image P n+1 Search Area Sn+1 Thereafter, the process of steps S1 to S6 is appropriately repeated, and the fluoroscopic X-ray images P are continuously acquired to track the marker 10, while performing treatment using therapeutic radiation.

[0072] <Details of the similar object determination process> Here, the details of the process in step S4 in which the detection target determination unit 23 determines the detection target F will be described. The detection target determination unit 23 determines whether the detection target F, which is a candidate for the marker 10, is a genuine marker 10, based on information on the movement pattern of the detection target F. The movement pattern of the detection target F is specified by the pattern in which the position of the detection target F changes between frames of the X-ray fluoroscopic image P.

[0073] Through intensive research by the inventors, it has been found that information on the movement pattern of the detection target F can be used when determining whether the detection target F is a genuine marker 10. That is, the marker 10 placed in the body of the subject M moves mainly due to the breathing or pulsation of the subject M. Both breathing and pulsation are periodic actions. Therefore, the marker 10 placed in the body of the subject M generally moves periodically along a predetermined trajectory. In other words, if the detection target F is a genuine marker 10, the position of the detection target F should change along the periodic trajectory in the continuously acquired X-ray fluoroscopic images P. In other words, if the detection target F detected from the X-ray fluoroscopic images P is located at a position significantly deviated from the periodic trajectory, it can be determined that the detection target F is not the marker 10 but a similar target R.

[0074] The trajectory of the marker 10 may be a linear trajectory K1 as shown in the left diagram of Fig. 14, or an elliptical trajectory K2 as shown in the right diagram of Fig. 14. In the former case, the marker 10 moves back and forth between the terminals N1 and N2 along the linear trajectory K1 extending in the x1 direction. In the latter case, the marker 10 moves along the elliptical trajectory K2 with the x1 direction as the major axis direction, alternately passing through the terminals N3 and N4.

[0075] Furthermore, as a result of the study, the inventors found that the manner in which the marker 10 moves along a periodic trajectory such as the trajectory K1 or the trajectory K2 is divided into two types of patterns depending on the position of the marker on the trajectory. That is, as a first movement pattern, when the marker 10 moves along the center part Ce of the trajectory K1 or the trajectory K2, the movement speed of the marker 10 is relatively high, but the possibility of the marker 10 changing its movement direction is low. And as a second movement pattern, when the marker 10 moves along the end part Ed of the trajectory K1 or the trajectory K2, the possibility of the marker 10 changing its movement direction is relatively high, but the movement speed of the marker 10 is relatively low. Also, when the marker 10 moves along the end part Ed, the change in the movement speed of the marker 10 is small.

[0076] In this embodiment, the detection target F is classified into two patterns according to the moving speed between frames. Then, for each pattern, it is determined whether the moving manner of the detection target F is close to that of the marker 10, thereby determining whether the detection target F is a genuine marker 10. Details of step S4 will be described below with reference to the flowchart shown in FIG.

[0077] Step S401 (calculation of travel distance) When step S4 is started, the moving distance G of the detection target F is calculated. n Detection target F n Distance traveled by G n When calculating, the X-ray fluoroscopic image P and the X-ray fluoroscopic image P n The distance that the detection target F has moved between n Hereinafter, the X-ray fluoroscopic image P that serves as the base point of the movement is referred to as the "base image."

[0078] In this embodiment, the moving distance G is calculated based on an X-ray fluoroscopic image P (here, the X-ray fluoroscopic image P n) and in which the detection object F is determined to be the marker 10 is selected as the base image. In order to more accurately determine the movement mode of the detection object, it is preferable to select as the base image an X-ray fluoroscopic image P generated closer to the time of generation of the X-ray fluoroscopic image P that is the subject of calculation of the movement distance G.

[0079] Here, the X-ray fluoroscopic image P n X-ray fluoroscopic images P1 to P2 generated at an earlier time n-1 In this case, all of the detection objects F are determined to be genuine markers 10. n The X-ray fluoroscopic image P generated most recently n-1 is selected as the base image. That is, the X-ray fluoroscopic image P n Detection target F n Distance traveled by G n is an X-ray fluoroscopic image P n-1 Detection target F n-1 Position and X-ray fluoroscopic image P n Detection target F n This corresponds to the distance between the position of

[0080] That is, the motion vector calculation unit 27 calculates the X-ray fluoroscopic image P n Detection target F n Position B n and the X-ray fluoroscopic image P that is determined to be the marker 10 immediately before that. n-1 Detection target F n-1 Based on the position of the detection target F n Distance traveled by G n As shown in FIG. 16, the detection object F n-1 From the position of the detection target F n The distance to the position of the detection target F n Distance traveled by G n Equivalent to the travel distance G n The information is appropriately stored in the storage unit 15. In this description, the X-ray fluoroscopic image P n-1 corresponds to the third X-ray fluoroscopic image.

[0081] At this point, the detection target F n-1 and detection target F n-2 Since it is determined that the marker 10 is the detection target F in FIG. n-1 and detection target F n-2 is shown in the same shape as the marker 10. n Since it is unclear whether the detected object F is a marker 10 or a similar object R, in FIG. n is shown as a black circle.

[0082] The information on the past movement distance G of the detection target F is stored by the step S401 performed in the past. n-2 From detection target F n-1 The distance to is the travel distance G n-1 and the detection target F n-3 From detection target F n-2 The distance to is the travel distance G n-2 It is remembered as.

[0083] Step S402 (Calculation of movement vector) The motion vector calculation unit 27 calculates the movement distance G of the detection target F and also calculates the motion vector V of the detection target F. The motion vector V of the detection target F can be calculated by specifying the movement direction H of the detection target F in addition to the movement distance G. The movement direction H of the detection target F is the direction in which the detection target F moves between the X-ray fluoroscopic image P, which is the object of calculation of the movement direction H, and the base image. In other words, the motion vector calculation unit 27 calculates the movement distance G of the detection target F and the motion vector V of the detection target F. n-1 From detection target F n As the direction toward the detection target F n Movement direction H n can be identified.

[0084] Distance traveled G n and the moving direction H n By obtaining this information, the movement vector calculation unit 27 calculates the X-ray fluoroscopic image P n-1 X-ray fluoroscopic image P n Detection target F during one frame n The movement vector V nIn this manner, information on the movement vector V is obtained for each of the generated fluoroscopic X-ray images P. Each piece of information on the movement vector V obtained is stored in the storage unit 15 one by one.

[0085] Step S403 (Calculation of average movement distance) Currently generated X-ray fluoroscopic image P n In the detection target F n Distance traveled by G n and the movement vector V n After the calculation, the current detection target F n The average movement distance G of the marker 10 is used to determine the movement state of the av Here, since all past detection targets F have been determined to be genuine markers 10, the most recently calculated movement distance G n The information on multiple travel distances G is obtained by going back from the beginning, and the average of the multiple travel distances G obtained is calculated as the average travel distance G av The average travel distance G av The number of moving distances G used in the calculation may be changed as appropriate.

[0086] In this embodiment, the average movement distance G is calculated by calculating the movement distance G from four frames going back from the current time. av That is, the current travel distance G is the travel distance G n If so, the travel distance G n-1 , travel distance G n-2 , travel distance G n-3 , and the travel distance G n-4 The average value of the average travel distance G av The distance traveled is calculated as follows: n-1 is an X-ray fluoroscopic image P n-2 X-ray fluoroscopic image P n-1 The distance traveled by the detection target F from n-2 From the position of the detection target F n-1 The distance to the position is stored in the storage unit 15. Similarly, the moving distance G n-2 is the detection target F n-3 From detection target F n-2The moving state determination unit 29 reads out information on the moving distance G of the detection object F that was previously calculated from the storage unit 15, and calculates the average moving distance G av Calculate.

[0087] Step S404 (determination of moving state) Detection target F n Distance traveled by G n , and the average movement distance of marker 10 in the recent past G av After the information is acquired, the detection target F n The moving state determination unit 29 determines the moving state of the moving distance G n and the average travel distance G av The value of the moving distance G is compared with a predetermined value T1. n and the average travel distance G av In response to the result of comparing the detected object F with the predetermined value T1, the moving state determination unit 29 determines the moving state of the detected object F at the current time, i.e., n The moving state of the detection object F is then determined. n Depending on the result of the determination of the moving state, the subsequent steps are branched (branch Q2).

[0088] Detection target F n Distance traveled by G n and the average movement distance G of marker 10 av If both values ​​are equal to or greater than the predetermined value T1, the moving state determination unit 29 detects the object F n is judged to be in a high-speed moving state. n and the average travel distance G av If at least one of the above is less than the predetermined value T1, the moving state determination unit 29 detects the detection object F n It is determined that the object F is moving at a low speed. n If it is determined that the detection target F is moving at high speed, the process proceeds from step S404 to step S405. n If it is determined that the current X-ray fluoroscopic image P is in a low-speed moving state, the process proceeds from step S404 to step S406. The detection object determination unit 23 applies different determination conditions depending on the determination result of the moving state determination unit 29, and n Detection target F detected fromn is judged to be either a genuine marker 10 or a similar object R. Note that the predetermined value T1 is determined, for example, based on data previously obtained as the distance that the marker 10 moves during one frame.

[0089] Step S405 (Determine the inner product of vectors) Current detection target F n If the moving state determination unit 29 determines that the detection target F is in a high speed moving state, the detection target determination unit 23 calculates the inner product of the movement vector V of the detection target F at the current time and the movement vector of the marker 10 in the base image.

[0090] The most recent movement vector of the marker 10 is calculated based on the distance and direction that the marker 10 moved during one frame in the most recent past. n-1 , F n-2 ... are all determined to be genuine markers 10, so the X-ray fluoroscopic image P n-1 Therefore, the movement vector of the marker 10 in the base image is n-1 Detection target F n-1 The movement vector V n-1 The detection target F n-1 The movement vector V n-1 is the detection target F n-2 From detection target F n-1 The distance traveled and the direction of travel are calculated.

[0091] That is, the current detection target F is the detection target F n If so, the detection object determination unit 23 determines in step S405 that the detection object F n The movement vector V n and the movement vector V n-1 Then, depending on the value of the inner product, the detection object determination unit 23 determines whether the detection object F n is a genuine marker 10 or is a detection target F n Determine whether is a similar object R.

[0092] Current detection target F n When the detection target F is in a high-speed moving state, i.e., moving at a relatively high speed, n If the marker 10 is a genuine marker 10, the moving direction H of the detection target F should not change significantly between successive frames. This is because the timing at which the marker 10 moves at a relatively high speed on the trajectory K1 or P2 along which the genuine marker 10 moves is the timing at which the marker 10 moves through the center Ce of the trajectory. It is considered that the moving direction of the marker 10 does not change significantly at the timing at which the marker 10 moves through the center Ce. In other words, n When the detection target F is moving at high speed, n Movement direction H n is significantly different from the movement direction of the marker 10 in the recent past, the detection target F detected at the present time n It can be determined that the marker 10 is not a genuine marker but a similar object R.

[0093] The detection target determination unit 23 detects the current movement vector V n and the most recent movement vector V n-1 The information of and is read, and the dot product of the two movement vectors V (V n ·V n-1 ) is calculated. Then, as shown in FIG. n ·V n-1 ) depending on the value of the detection target F n Determine whether or not the answer is yes (branch Q3).

[0094] Movement vector V n and the movement vector V n-1 The dot product with (V n ·V n-1 ) is a value equal to or greater than 0, the detection target determination unit 23 determines the current detection target F n is judged to be the genuine marker 10 (judgment A1). n ·V n-1 ) is 0 or more, the current detection target F n The movement vector V n and the nearest marker 10, the detection target F n-1 The movement vector V n-1The angle between is less than 90 degrees. That is, the inner product (V n ·V n-1 ) is 0 or more, the detection target F n-2 , detection target F n-1 , and the detection target F n The positional relationship of the X-ray fluoroscopic image P n-2 X-ray fluoroscopy images P n During the time from the time of the image capture to the time of the image capture, the detection target F moves at a relatively high speed, but the movement direction H of the detection target F does not change significantly. This movement mode of the detection target F is the same as the movement mode of the marker 10 that moves in the center part Ce of the periodic trajectory. Therefore, the inner product (V n ·V n-1 ) is 0 or more, the detection target F n It can be determined that the marker 10 is a genuine marker. In FIG. 17, depending on the determination result, the detection object F n is shown in the same shape as the marker 10.

[0095] On the other hand, the movement vector V n and the movement vector V n-1 The dot product with (V n ·V n-1 ) is a negative value, the detection object determination unit 23 determines the current detection object F n is judged to be a similar object R (judgment A2). The inner product (V n ·V n-1 ) is negative, the current detection target F n Movement direction H n and the detection target F at the previous frame n-1 Movement direction H n-1 The angle between is more than 90 degrees. That is, the dot product (V n ·V n-1 ) is less than 0, the detection target F n-2 , detection target F n-1 , and the detection target F n The positional relationship of the movement vector V n and the movement vector V n-1 The angle θ between n exceeds 90 degrees.

[0096] In other words, the inner product (V n ·V n-1 ) is negative, the X-ray fluoroscopic image P n-2 X-ray fluoroscopy images P n During the short period from the time of the image capture to the time of the image capture, the detection target F continues to move at a relatively high speed, while the movement direction H changes significantly. This movement mode of the detection target F is significantly different from the movement mode of the marker 10 that moves in the center part Ce of the periodic trajectory. Therefore, the inner product (V n ·V n-1 ) is negative, the detection target F n It can be determined that the marker 10 is not a genuine marker 10 but a similar object R. In FIG. 18, depending on the determination result, n is shown in the same figure as the similar object R.

[0097] In this way, the current detection target F n If it is determined that the detection target F is moving at high speed, n Movement direction H n The detection target F is determined based on the judgment condition of whether or not the direction of movement H has changed significantly from the most recent direction. n As an example of a method for determining a change in the moving direction H, in this embodiment, the current moving vector V n and the most recent movement vector V n-1 Calculate the inner product with n Determine the following.

[0098] Step S406 (determine deviation in travel distance) Next, the current detection target F n The following describes the conditions for determining whether the current detection target F is moving at a low speed. n When the moving state determination unit 29 determines that the marker 10 is moving at a low speed, the detection target determination unit 23 calculates the average moving distance G av Based on the deviation rate of the moving distance G of the detection target F at the current time with respect to the average moving distance G, the detection target determination unit 23 determines whether the detection target F at the current time is a genuine marker 10. av Distance traveled G nBased on the deviation rate, the detection target F n Determine whether or not is a genuine marker 10.

[0099] In this embodiment, the detection target F n Distance traveled by G n The value of the average movement distance G of the detection target F during the most recent four frame period av The average travel distance G is calculated by dividing it by the value of av Distance traveled G n The deviation rate of (G n / G av ) value. Then, the deviation rate (G n / G av By comparing the value of F) with a predetermined value T2, the detection object determination unit 23 determines whether F n is a genuine marker 10 or is a detection target F n Determine whether is a similar object R.

[0100] The predetermined value T2 is a value determined based on data on the deviation rate of the movement distance previously obtained for the marker 10. av If the value of is extremely close to zero, the deviation rate (G n / G av ) becomes significantly large, making it difficult to properly determine the movement state of the detection target F. av If the value of is less than or equal to the threshold J, the average movement distance G av It is preferable to calculate the deviation rate assuming that the value of is the threshold value J. In this case, the deviation rate (G n / G av )=(G n / J), where the threshold value J is determined in advance as a predetermined positive number.

[0101] Deviation rate (G n / G av If the value of F ) is less than T2, the detection object determination unit 23 determines whether the current detection object F n It is judged that the marker 10 is genuine (judgment A3). n / G av) is less than T2, the detection object F in the X-ray fluoroscopic image P n-5 , detection target F n-4 , detection target F n-3 , detection target F n-2 , detection target F n-1 , and the detection target F n The positional relationship of the X-ray fluoroscopic image P n-5 X-ray fluoroscopy images P n While the detection target F moves at a relatively slow speed during the period from the time of the image capture to the time of the image capture, the movement distance G of the detection target F does not change significantly between frames. This movement mode of the detection target F is the same as the movement mode of the marker 10 that moves along the end Ed of the periodic trajectory. Therefore, the deviation rate (G n / G av If the value of F ) is less than T2, the detection object determination unit 23 determines whether the current detection object F n It can be determined that the marker 10 is genuine.

[0102] On the other hand, the deviation rate (G n / G av ) is equal to or greater than T2, the detection object determination unit 23 detects the current detection object F n is judged to be a similar object R (judgment A4). n / G av ) is equal to or greater than T2, the detection target position B n-5 Or detection target position B n The positional relationship of is as shown in Figure 20. In this case, the travel distance G n-4 Or travel distance G n-1 Compared to the current travel distance G n This means that there is a large discrepancy.

[0103] In other words, the deviation rate (G n / G av ) is equal to or greater than a predetermined value T2, the X-ray fluoroscopic image P n-1 Even though the moving distance G is constant until the time of taking the X-ray fluoroscopy image P n-1 X-ray fluoroscopy images P n During the short period leading up to the shooting of the target Fn Distance traveled by G n This means that the detection target F n The movement of the marker 10 at the end Ed of the periodic trajectory is significantly different from the movement of the marker 10 at the end Ed of the periodic trajectory. n / G av ) is equal to or greater than a predetermined value T2, n It can be determined that the marker 10 is not a genuine marker but a similar object R.

[0104] In this way, the current detection target F n When it is determined that the detection target F is moving at a low speed, n Distance traveled by G n Based on the judgment condition of whether the distance moved significantly from the most recent distance G, the detection target F n As an example of a method for determining the deviation of the moving distance G, in this embodiment, the average moving distance G in the most recent few frames is av The distance traveled in the current frame G n Based on the deviation rate of the detection target F n Determine the following.

[0105] In step S405 or S406, the detection object F n When the result of the determination is obtained, the series of steps related to step S4 is completed. n If the detection object determination unit 23 determines that the marker 10 is a genuine marker 10, the search area update unit 25 updates the detection object F in step S5. n The information in the search area storage unit 34 is updated based on the position information of the detection object F. n Search area with the position of as the reference position n+1 will be overwritten with the information.

[0106] Detection target F n When the detection target determination unit 23 determines that the detection target F is a similar target R, the search area update unit 25 updates the detection target F nThe information in the search area storage unit 34 is determined using the position information of the detection object F that was most recently determined to be the marker 10, without using the position information of the detection object F in step S4. n If it is determined that the detected object F is a similar object R, the information in the search area storage unit 34 is not changed in step S5. n is determined to be a similar object R, the position information of the search area stored in the search area storage unit 34 does not change. As a result, the position of the search area S set in the X-ray fluoroscopic image P in the next step S2 does not change.

[0107] If it is determined in step S405 that the detection target F is a similar target R, it is preferable that the search area update unit 25 performs an update to expand the search area S in step S5. That is, as shown in FIG. 21, the search area update unit 25 updates the information stored in the search area storage unit 34 to the search area S. n From search area S nA The search area before the update is S n and the updated search area S nA are all detection target positions B n-1 That is, before and after step S5, the information on the reference position stored in the genuine marker storage unit 33 is the detection target position B n-1 On the other hand, the updated search area S nA As shown in the upper part of Figure 21, the search area S before the update n The range is expanded compared to Search Area S. n Search area S for nA The magnification factor N may be changed as appropriate according to conditions such as the moving speed of the marker 10 in one frame. In this case, the X-ray fluoroscopic image P n The X-ray fluoroscopic image P generated after n+1 The search area S set for n+1 is the expanded search area S nA It becomes.

[0108] If the process branches to step S405, it is determined that the detection target F is moving at high speed. In other words, the average moving distance G av is equal to or greater than the predetermined value T1. This means that the moving speed of the genuine marker 10 is relatively high not only in the past few frames but also at the present time. Therefore, the current X-ray fluoroscopic image P n The position of the marker 10 in the next acquired X-ray fluoroscopic image P n+1 The distance between the position of the marker 10 in the search area S n+1 Search area S before updating n When the width of the X-ray fluoroscopy image is set to the same as that of the n+1 The position of the marker 10 shown in the X-ray fluoroscopic image P n+1 The search area S is set to n+1 There is concern that it may fall outside of this range.

[0109] Therefore, if it is determined in step S405 that the detection target F is a similar target R, the search area update unit 25 updates the search area S in step S5. n Expand the search area S n+1 In other words, for the search area S, the reference position is the detection target position B n-1 While maintaining the state, the area is updated to be enlarged. In this case, the position information stored in the genuine marker storage unit 33 is the detection target position B n-1 On the other hand, the search area information stored in the search area storage unit 34 is not changed from the search area S n From search area S nA will be updated.

[0110] In this way, when the detection target F is determined to be a similar target R while moving at high speed, the information of the search area S to be set next is changed to expand its size while maintaining the reference position. With this configuration, the reference position of the search area S is not changed, so that it is possible to avoid the search area S being set at a position that tracks the similar target R in the X-ray fluoroscopic image P generated later. On the other hand, because the size of the search area S to be set next is expanded, it is possible to set the search area S so that the genuine marker 10 is more reliably included inside the search area S in the X-ray fluoroscopic image P generated later.

[0111] Here, for each of the determination results in step S4 for the nth time, the determination process performed in step S4 for the next (n+1)th time will be described in detail. First, the detection object F detected in step S3 for the nth time will be n If it is determined in step S4 for the nth time that the marker 10 is a genuine marker 10, then in step S4 for the (n+1)th time, the detection target F n+1 The process for determining the above is as follows: In step S401, the detection object F n Position B n Starting from the detection target F n+1 Distance traveled by G n+1 That is, the X-ray fluoroscopic image P n Using the base image, X-ray fluoroscopic image P n+1 Detection target F n+1 Distance traveled by G n+1 As a result, the detection target F n Position B n From detection target F n+1 Position B n+1 The distance to the detection target F n+1 Distance traveled by G n+1 In step S402, the detection object F n Position B n From detection target F n+1 Position B n+1 Based on the distance and direction to the detected object F n+1 The movement vector V n+1 Calculate.

[0112] In step S403, the current (latest) X-ray fluoroscopic image P n+1 Average movement distance G from the movement distance G for the last four frames av In step S403 for the (n+1)th time, the current moving distance G is calculated based on the X-ray fluoroscopic image P n+1 Detection target F n+1 Distance traveled by G n+1 Therefore, in step S403, the moving distance G n , travel distance G n-1 , travel distance G n-2 , and the travel distance G n-3 The average value of the average travel distance G av The calculation is as follows: n Since it is determined to be a genuine marker 10 in the n-th step S4, the movement vector V n is the detection target F n-1 From detection target F n The vector V is the distance traveled by n is the detection target F n-1 From detection target F n This corresponds to the distance traveled G to the target.

[0113] In step S404 for the (n+1)th time, the detection object F n From detection target F n+1 Distance traveled to G n+1 and the travel distance G n-3 ~G n Average travel distance of G av Based on this, the detection target F n+1 The moving state of the detection target F is judged. n+1 If it is determined that the object F is moving at high speed, the process proceeds to step S405. n+1 The movement vector V n+1 and detection target F n The movement vector V n The dot product with (V n+1 ·V n ) based on the detection target F n+1 A determination is made.

[0114] Detection target F n+1If it is determined that the object F is moving at a low speed, the process proceeds to step S406. n+1 Distance traveled by G n+1 and the average moving distance G calculated in step S403 for the (n+1)th time av Deviation rate from (G n+1 / G av ) is compared with a predetermined value T2 to detect the object F n+1 As described above, in step S4 for the nth time, the detection object F n If it is determined that the marker 10 is genuine, the detection target F is detected in step S4 for the (n+1)th time. n+1 In the process of determining the detection target F n Position B n and detection target F n+1 Position B n+1 Based on this information, the detection target F n+1 Distance traveled by G n+1 and the movement vector V n+1 Then, calculate the travel distance G n+1 and the movement vector V n+1 Using this, the (n+1)th detected object F n+1 It is possible to make a determination.

[0115] Next, the detection target F detected in step S3 for the nth time n If it is determined to be a similar target R in the nth step S4, then the detected target F is determined to be a similar target R in the (n+1)th step S4. n+1 The process for determining the detection target F is as follows. n+1 FIG. 37 shows the case where the detection target F is moving at high speed. n+1 This shows the case where the detection target F is moving at a low speed. n If R is a similar object, then F is a detected object. n From detection target F n+1 The movement direction H and the movement distance G from the target F to the target F deviate from the movement of the genuine marker 10. n Position of and detection target F n+1 Based on the position of the detection target F n+1 The movement vector V n+1 and the travel distance Gn+1 Calculating the detection target F n+1 The accuracy of the judgment decreases.

[0116] Therefore, the detection target F n If it is determined that the similar object R is a similar object, in step S401 for the (n+1)th time, the detection object F most recently determined to be a genuine marker 10 is n-1 Starting from the detection target F n+1 Distance traveled by G n+1 That is, the X-ray fluoroscopic image P n-1 Using the base image, X-ray fluoroscopic image P n+1 Detection target F n+1 Distance traveled by G n+1 As a result, the detection target F n-1 Position B n-1 From detection target F n+1 Position B n+1 The distance to the detection target F n+1 Distance traveled by G n+1 Similarly, in step S402, the detection object F n-1 Position B n-1 From detection target F n+1 Position B n+1 Based on the distance and direction to the detected object F n+1 The movement vector V n+1 In this case, the X-ray fluoroscopic image P n+1 corresponds to the first X-ray fluoroscopy image, and the X-ray fluoroscopy image P n-1 corresponds to the third X-ray fluoroscopic image. X-ray fluoroscopic image P n+1 X-ray fluoroscopic image P generated later n+2 etc. corresponds to the second X-ray fluoroscopic image.

[0117] In this case, the movement vector V n+1 corresponds to a motion vector V for two frames, but since the time of one frame is short, the amount of change in the motion direction H and the motion distance G during one frame is small. Therefore, even if a motion vector V for two frames is used, n+1 This can avoid a decrease in the accuracy of the determination.

[0118] In step S403 for the (n+1)th time, the average movement distance G of the marker 10 in the most recent past is calculated from the movement distance G of the most recent four frames. av Calculate the average moving distance G av The moving distance G used in calculating the moving distance is the moving distance G when the detection target F in two consecutive frames is both a genuine marker 10. p If R is a similar object, then F is a detected object. p-1 From detection target F p Data on the distance traveled to the target F p Detection target p+1 The data of the distance traveled to the target point (G) is the average distance traveled by marker 10 in the most recent past (G) av It is not used in the calculation of

[0119] Here, the detection target F n Since is a similar object R, the detection object F n-1 From detection target F n The data of the moving distance G to the detection target F is not used. n-2 From detection target F n-1 Distance traveled to G n-1 , detection target F n-3 From detection target F n-2 Distance traveled to G n-2 , detection target F n-4 From detection target F n-3 Distance traveled to G n-3 , and the detection target F n-5 From detection target F n-4 Distance traveled to G n-4 The average travel distance G was calculated using the data of these four travel distances G. av Calculate.

[0120] In step S404, the moving distance G n-1 ~G n-4 Average travel distance of G av , and the detection target F n-1 From detection target F n+1 Movement vector V to n+1 Using the detection target F n+1 The moving state of the object is determined.

[0121] Detection target F n+1 If it is determined that the detection target F is moving at high speed, the process proceeds to step S405. Then, the inner product of the current movement vector V of the detection target F and the most recent movement vector of the marker 10 is calculated. The current movement vector V is calculated as n-1 From detection target F n+1 Movement vector V to n+1 Since the detection target F is a similar target R, n-1 From detection target F n The motion vector V up to the current time point cannot be used as the motion vector of the marker 10 in the near future. n-1 and detection target F n-2 All of the markers 10 are determined to be genuine. n-2 From detection target F n-1 Movement vector V to n-1 is used as the movement vector of the marker 10 in the immediate vicinity.

[0122] That is, the detection object determination unit 23 detects the detection object F n-1 From detection target F n+1 Movement vector V to n+1 and detection target F n-2 From detection target F n-1 Movement vector V to n-1 The dot product with (V n+1 ·V n-1 ) based on the detection target F n+1 The inner product (V n+1 ·V n-1 ) is 0 or more, the detection target F n+1 is determined to be the genuine marker 10. The inner product (V n+1 ·V n-1 ) is negative, F is the detection target n+1 is determined to be a similar object R.

[0123] Detection target F n+1If it is determined that the marker 10 is moving at a low speed, the process proceeds to step S406. Then, the detection object determination unit 23 calculates the current moving distance G of the detection object F and the most recent average moving distance G of the marker 10. av That is, the detection object determination unit 23 determines the detection object F at the current time based on the deviation rate from the detection object F. n+1 Distance traveled by G n+1 and the detection target F that was most recently determined to be marker 10. n-1 ~F n-5 Average travel distance of G av The ratio of the deviation rate (G n+1 / G av ) and the deviation rate (G n+1 / G av ) is compared with a predetermined value T2, the current detection target F n+1 It is determined whether the marker 10 is a genuine marker or a similar object R.

[0124] In this way, when the detection target F is determined to be a similar target R in a given frame, the detection target F determined to be a similar target R can be excluded from the calculation of the movement vector V and the movement distance G, thereby making it possible to determine the detection target F in the subsequent frames. Note that, if the detection target F continues to be determined to be a similar target R over multiple frames, it becomes difficult to determine the detection target F using the inner product of the movement vector V or the deviation rate of the movement distance G.

[0125] Therefore, if the detection target F continues to be determined to be a similar target R over a predetermined number of frames, the range of the search area S is updated to a predetermined range BF. The range BF is a range that is determined in advance in a treatment plan so that irradiation of therapeutic radiation is permitted when the marker 10 is located in the range BF. Note that the value of the predetermined number N may be any number equal to or greater than 2. In other words, if the detection target F continues to be determined to be a similar target R over N frames, the operation of tracking the marker 10 is interrupted, and the search area S is temporarily fixed to the range BF. In other words, the search area update unit 25 changes the information in the search area storage unit 34 to the range BF, and maintains the information.

[0126] The process of restarting the update of the search area S after the search area S is fixed to the range BF will be described. While the search area S is fixed to the range BF, the marker detection unit 21 searches the inside of the range BF to detect the detection target F. Then, the X-ray fluoroscopic image P j In the detection target F j Matching score C j When the threshold T4 is reached or exceeded, the detection object F j The search area update unit 25 determines that the marker 10 is highly likely to be the marker 10, and resumes the tracking process of the detection target F. j Update the location information.

[0127] The search area update unit 25 also updates the detection area F j The information in the search area storage unit 34 is updated based on the position information of the detection object F. j Search area S centered on the position j+1 As a result, the information on the X-ray fluoroscopic image P j The next generated X-ray fluoroscopic image P j+1 The detection target F j Search area S centered on the position j+1 is set, so the X-ray fluoroscopy image P j+1 A search area S is set in the subsequent X-ray fluoroscopic images P to track the detection target F.

[0128] The X-ray fluoroscopy apparatus 1 according to the first embodiment includes a detection target determination unit 23 that determines whether a detection target F detected by the marker detection unit 21 from an X-ray fluoroscopic image P corresponds to a genuine marker 10 or a similar target R. The marker detection unit 21 detects the detection target F by determining whether an object shown in the X-ray fluoroscopic image P is a marker 10 based on the shape of the object, using a method such as template matching. On the other hand, the detection target determination unit 23 determines whether the detection target F is a marker 10 based on the movement mode of the detection target F. In other words, the detection target determination unit 23 identifies the marker 10 using a different criterion from that of the marker detection unit 21, and therefore the detection accuracy of the marker 10 can be further improved by providing the marker detection unit 21 and the detection target determination unit 23.

[0129] Furthermore, the X-ray fluoroscope 1 according to the first embodiment includes a movement state determination unit 29 that determines whether the movement state of the detection target F is a high-speed movement state or a low-speed movement state. The detection target determination unit 23 determines whether the detection target F is the marker 10 by using different determination criteria for each of the cases where the detection target F is in a high-speed movement state and a low-speed movement state.

[0130] The inventors have noticed that the movement of the marker 10 caused by the breathing of the subject M is periodic, and that the periodic movement has two types of movement patterns depending on the moving speed of the marker 10. That is, when the marker 10 is in a high-speed moving state, the moving direction is constant, and when the marker 10 is in a low-speed moving state, the moving distance is constant. Therefore, when the detection target F detected by the marker detection unit 21 is in a high-speed moving state, the accuracy of the determination of the detection target F can be improved by applying a judgment criterion of whether the moving direction H of the detection target F has changed significantly from the most recent moving direction H. Also, when the detection target F detected by the marker detection unit 21 is in a low-speed moving state, the accuracy of the determination of the detection target F can be improved by applying a judgment criterion of whether the moving distance G of the detection target F is significantly deviated from the average moving distance of the marker 10 in the low-speed moving state.

[0131] [Second embodiment] Next, an X-ray fluoroscopy apparatus 101 according to the second embodiment will be described. Unlike the first embodiment that includes the detection target determination unit 23, the second embodiment includes a frame-out detection unit 103 (to be described later) and the like. Note that, in the X-ray fluoroscopy apparatus 101 according to the second embodiment, components similar to those of the X-ray fluoroscopy apparatus 1 according to the first embodiment are simply assigned the same reference numerals, and description thereof will be omitted.

[0132] 22 is a functional block diagram of an X-ray fluoroscopy apparatus 101 according to the second embodiment. In the second embodiment, the control unit 9 includes a frame-out detection unit 103, a score acquisition unit 105, a marker return detection unit 107, and an update state switching unit 108. In the second embodiment, the storage unit 15 includes a reference position storage unit 109. The frame-out detection unit 103 detects the presence or absence of a frame-out state based on the positional relationship between the search area S set by the search area setting unit 22 and the outer edge of the X-ray fluoroscopic image P. In this embodiment, the frame-out state refers to a state in which the position of the marker 10 is expected to move from within the imaging range of the X-ray fluoroscopic image P to outside the imaging range.

[0133] In this embodiment, the frame-out state is determined when the detection target F is moving at high speed and a part of the search area S is set outside the X-ray fluoroscopic image P. Note that the frame-out state also includes a state in which the detection target F is moving at high speed and the boundary line of the search area S is in contact with the outer periphery of the X-ray fluoroscopic image P. The process of determining the occurrence of the frame-out state will be described in detail later.

[0134] The score acquiring unit 105 appropriately acquires information on the matching score C calculated for each detection target F. In this embodiment, the matching score C means the similarity between the marker 10 in the template image Tp and the detection target F in the X-ray fluoroscopic image P. The score acquiring unit 105 also compares the matching score C of the most recently detected detection target F with the matching scores C of detection targets F detected in the past, to determine the most recently detected detection target F.

[0135] The marker return detection unit 107 detects whether or not a marker return state has occurred. In this embodiment, the marker return state refers to a state in which the position of the marker 10, which is the tracking target, has returned from outside the imaging range of the X-ray fluoroscopic image P to within the imaging range of the X-ray fluoroscopic image P. In this embodiment, the occurrence of the marker return state is detected based on information on the matching score C and the movement vector V. In this embodiment, the marker return detection unit 107 corresponds to a tracking target return detection unit.

[0136] The update state switching unit 108 switches the search area update unit 25 between a normal state and an area fixed state. The reference position storage unit 109 stores position information corresponding to the reference position of the search area S. In this embodiment, the search area update unit 25 updates the information of the search area S to be set in the next X-ray fluoroscopic image, with the range centered on the reference position.

[0137] The manner in which the reference position information stored in the reference position storage unit 109 is updated varies depending on the state of the search area update unit 25. When the search area update unit 25 is in the normal state, the detection target position B of the most recently detected detection target F is stored as the reference position. In other words, when the search area update unit 25 is in the normal state, the reference position information is updated every time an X-ray fluoroscopic image P is generated.

[0138] When the search area update unit 25 is in the area fixed state, the reference position information stored in the reference position storage unit 109 is maintained at the reference position at the time when the search area update unit 25 is switched to the area fixed state. That is, the reference position information does not change while the search area update unit 25 is in the area fixed state. The manner in which the state of the search area update unit 25 is switched will be described later in detail.

[0139] <Basic operation under normal conditions> Here, the basic operation of the X-ray fluoroscope 101 according to the second embodiment will be described. Fig. 23 is a flowchart showing an outline of the process of tracking the marker 10 using the X-ray fluoroscope 101 according to the second embodiment. Note that detailed description of the same processes as those in the first embodiment shown in Fig. 3 will be omitted. Note that it is assumed here that the search area update unit 25 is in a normal state at the start of step S1. That is, here, the basic operation of the X-ray fluoroscope 101 when the search area update unit 25 is in a normal state will be described.

[0140] Step S1 (Generation of X-ray fluoroscopic images) The process of step S1 in the second embodiment is the same as step S1 in the first embodiment. That is, X-ray fluoroscopy is performed using the first imaging system L1 and the second imaging system L2, and two X-ray fluoroscopic images P taken from different directions are generated. In addition, the latest X-ray fluoroscopic image P is generated as the X-ray fluoroscopic image P. n is generated.

[0141] Step S2 (Setting the search area) When a new fluoroscopic X-ray image P is generated, a search area S is set for the latest fluoroscopic X-ray image P. In the second embodiment, the search area setting unit 22 reads out information on the reference position stored in the reference position storage unit 109, and sets a search area S centered on the reference position.

[0142] When the search area update unit 25 is in the normal state, the position information of the most recently detected detection target F is stored in the reference position storage unit 109. At the start of step S2, the "most recently detected detection target F" is the position information of the most recently generated X-ray fluoroscopic image P n-1 The detection target F detected by the marker detection unit 21 n-1 Therefore, the search area setting unit 22 sets the latest X-ray fluoroscopic image P n For detection target position B n-1 The range centered on is the search area S n When the search area update unit 25 is in the normal state, the X-ray fluoroscopic image P nThe search area S is set to n The position and size of the second embodiment are the same as those of the first embodiment, as shown in FIG.

[0143] Step S3 (Search for marker) The process of step S3 in the second embodiment is the same as step S3 in the first embodiment. n Search Area S n When the marker detection unit 21 is set, the marker detection unit 21 refers to the image of the marker 10 reflected in the template image Tp and detects the X-ray fluoroscopic image P n Within search area S n Then, the marker detection unit 21 detects an object that is determined to have the highest similarity (matching score) with the marker 10. That is, the marker detection unit 21 detects the object in the X-ray fluoroscopic image P n From detection target F n Detect object F n The information regarding the matching score is stored in the storage unit 15.

[0144] Step S4 (update search area) The X-ray fluoroscope 101 according to the second embodiment does not have a detection object determination unit 23. Therefore, unlike the first embodiment, the step of determining the detection object F by the detection object determination unit 23 is omitted. Therefore, when step S3 is completed and the detection object F is detected from the X-ray fluoroscopic image P, an operation of updating the search area S is started in step S4. Fig. 24 is a flowchart showing the process of step S4 according to the second embodiment.

[0145] When step S4 is started, the process branches depending on the state of the search area update unit 25 (branch Q5). If the search area update unit 25 is in the normal state, the process proceeds to step S4A. On the other hand, if the search area update unit 25 is in the area fixed state, the process proceeds to step S4C. Here, the case where the search area update unit 25 is in the normal state is described, so the process of step S4A is started.

[0146] When step S4A is started, the reference information is updated. That is, the detection object F detected in step S3 is n Position information of detection target position B n The information) is overwritten and stored in the reference position storage unit 109. That is, when the search area update unit 25 is in the normal state, the X-ray fluoroscopic image P n From detection target F n By detecting the position, the reference position stored in the reference position storage unit 109 becomes the detection target position. n-1 to detection target position B n When the information on the reference position has been updated, the process of step S4A is completed.

[0147] When step S4A is completed, the process proceeds to step S4B. In step S4B, the search area S set in the next generated X-ray fluoroscopic image P is updated based on the information on the reference position. In this embodiment, the reference position is the center position of the search area S. When the search area update unit 25 is in the normal state, the reference position is the detection target position n-1 to detection target position B n Therefore, the search area update unit 25 updates the information of the next search area S to the detection target position. n-1 Search area S centered on n to detection target position n Search area S centered on n+1 (See FIG. 11). When the search area update unit 25 is in the normal state, the size of the search area does not change before and after the update. That is, in this case, the search area S before the update n and the updated search area S n+1 The area of ​​the search area S is the same as that of the search area S. The process of step S4 is completed by updating the search area S.

[0148] Step S5 (Determining update status) In the second embodiment, when the process of step S4 of updating the search area S is completed, the update state is determined in step S5. That is, the update state switching unit 108 determines the update state of the search area update unit 25 based on the presence or absence of a frame-out state, etc. Then, the update state switching unit 108 switches the update state of the search area update unit 25 to a normal state or an area fixed state according to the determination result.

[0149] The frame-out state is a state in which the position of the marker 10 is expected to move from within the imaging range of the X-ray fluoroscopic image P to outside the imaging range. The marker 10 placed on the subject M is displaced due to the breathing of the subject M, etc. As a result, the marker 10 may move outside the imaging range of the X-ray fluoroscopic image P. If a search for the marker 10 based on the matching score is performed in a state in which the marker 10 has moved outside the imaging range of the X-ray fluoroscopic image P, the marker detection unit 21 will detect the similar object R as the marker 10. That is, a situation occurs in which the detection object F is actually the similar object R and not the marker 10.

[0150] When the search area update unit 25 is in a normal state, the position of the search area S is updated every time an X-ray fluoroscopic image P is generated, centered on the position of the latest detection target F. However, if the search area S is updated with the position of the latest detection target F as the reference position in a state in which the marker 10 has moved outside the shooting range of the X-ray fluoroscopic image P, the position of the search area S is updated with the position of the detection target F, which is a similar target R, as the center. In this case, there is a high possibility that the genuine marker 10 will be located outside the search area S in the X-ray fluoroscopic image P generated thereafter. As a result, there is a concern that the detection accuracy of the marker 10 in the subsequent X-ray fluoroscopic images P will decrease.

[0151] Therefore, in the second embodiment, when a frame-out state occurs, the search area update unit 25 is controlled to switch from the normal state to the area fixed state. When the search area update unit 25 enters the area fixed state, the reference position information stored in the reference position storage unit 109 is maintained until the area fixed state is released. That is, while the search area update unit 25 is in the area fixed state, the position of the search area S is fixed. Also, in the second embodiment, when a marker return state in which the marker 10 has returned from the outside to the inside of the X-ray fluoroscopic image P is detected, the update state switching unit 108 releases the area fixed state and controls the search area update unit 25 to switch to the normal state. Details of the criteria and methods for detecting the frame-out state and the marker return state will be described later.

[0152] Step S6 (calculation of three-dimensional position) The process of step S6 according to the second embodiment is the same as step S6 according to the first embodiment. That is, the marker position calculation unit 26 calculates the three-dimensional position of the marker 10 using two X-ray fluoroscopic images P acquired by the first imaging system L1 and the second imaging system L2. If the distance between the calculated three-dimensional position of the marker 10 and the three-dimensional coordinates determined by the advance treatment plan is within an allowable range, therapeutic radiation is irradiated to the subject M from a treatment device provided in a therapeutic radiation irradiation device (not shown). Thereafter, the process of steps S1 to S6 is appropriately repeated to continuously acquire X-ray fluoroscopic images P and track the marker 10, while performing treatment using therapeutic radiation.

[0153] <Details on determining update status> Here, the details of the process of determining the update state of the search area update unit 25 in step S5 of the second embodiment will be described. Fig. 25 is a flowchart showing the details of step S5 in the second embodiment. Step S5 branches depending on whether the search area update unit 25 is in the normal state or the area fixed state at the start point (branch Q6).

[0154] If the search area update unit 25 is in the normal state at the start of step S5, the process proceeds to step S501. On the other hand, if the search area update unit 25 is in the area fixed state, the process proceeds to step S504.

[0155] First, an overview of step S5 when the search area update unit 25 is in the normal state will be described. When the search area update unit 25 is in the normal state, in step S5 it is determined whether or not to switch the search area update unit 25 from the normal state to the area fixed state. That is, the presence or absence of a frame-out state is determined by the process of steps S5A to S5C. If a frame-out state is not detected, the search area update unit 25 is maintained in the normal state (decision A5). If a frame-out state is detected, the search area update unit 25 is switched from the normal state to the area fixed state (decision A6). Details of steps S5A to S5C will be described below.

[0156] Step S5A (calculation of travel distance) When the search area update unit 25 is in the normal state, it is first determined whether the currently detected detection target F is moving at high speed. To this end, the movement distance G of the detection target F detected from the currently obtained X-ray fluoroscopic image P is calculated. That is, the movement vector calculation unit 27 calculates the movement distance G of the currently detected detection target F from the currently obtained X-ray fluoroscopic image P. n Detection target position B n and the X-ray fluoroscopic image P n X-ray fluoroscopic image P generated at an earlier time n-1 Detection target position B n-1 Based on this, the detection target F n Distance traveled by G n Calculate the travel distance G n This information is stored in the storage unit 15 as appropriate.

[0157] Step S5B (Calculation of average movement distance) Latest X-ray fluoroscopic image P n In the detection target F n Distance traveled by G n After calculating, the average movement distance G of the marker 10 in the past few frames is calculated. avIn the second embodiment that does not include the detection object determination unit 23, the average movement distance G av When calculating the average distance, the average distance calculation unit 28 assumes that the detection object F detected from each X-ray fluoroscopic image P is a genuine marker 10, and calculates the average distance from the X-ray fluoroscopic image P n In the second embodiment, the average moving distance G av When calculating the most recently calculated travel distance G n The information on multiple travel distances G is obtained by going back from the beginning, and the average of the multiple travel distances G obtained is calculated as the average travel distance G av Here, the movement distance G for four frames is calculated as n-4 ~G n-1 The average value of the average travel distance G av It is calculated as follows.

[0158] Current detection target F n Distance traveled by G n , and the average distance traveled by marker 10 in the past G av After the information is acquired, the moving state determination unit 29 detects the detection object F n The criteria for determining the moving state are the same as those in the first embodiment. n and the average travel distance G av If all of the values ​​are equal to or greater than the predetermined value T1, the current detection target F n is determined to be in a high-speed moving state. n and the average travel distance G av If at least one of the values ​​is less than the predetermined value T1, the current detection target F n is determined to be in a low-speed moving state.

[0159] After steps S5A and S5B are completed, the detection target F n The process branches depending on the movement state of the current detection target F (branch Q7). nIf the movement state determination unit 29 determines that the search area update unit 25 is in a low-speed movement state, the update state switching unit 108 determines that the frame-out state condition is not satisfied. Then, the update state switching unit 108 causes the search area update unit 25 to maintain the normal state, and ends step S5 (determination A5).

[0160] On the other hand, the current detection target F n If the moving state determination unit 29 determines that the object is in a high speed moving state, the update state switching unit 108 determines that the first condition for the frame-out state is satisfied. In this case, the process proceeds to step S5C.

[0161] Step S5C (Determining the frame-out state) When step S5C is started, the frame-out detection unit 103 judges whether or not the search area S has reached the outside of the range of the X-ray fluoroscopic image P. That is, the search area S updated in the most recent step S4 n+1 When the search area S abuts against or intersects with the outer edge PL of the X-ray fluoroscopic image P, it is determined that the search area S has reached the outside of the range of the X-ray fluoroscopic image P. n The search area S is set based on the position of n+1 intersects with the outer edge PL of the X-ray fluoroscopic image P.

[0162] As shown in Figure 26, the detection target F n is moving at high speed and the search area S n+1 When the detection object F intersects with the outer edge PL of the X-ray fluoroscopic image P, the following situation is expected. n Search area S centered on n does not intersect with the outer edge PL of the X-ray fluoroscopic image P, while the detection target F n Search area S centered on n+1 intersects with the outer edge PL of the X-ray fluoroscopic image P. n In the detection target F n That is, the marker 10 is n It is considered that the object to be detected is moving closer to the outer edge PL of the object to be detected. nis in a high speed moving state, the marker 10 is considered to be moving toward the outside of the X-ray fluoroscopic image P at high speed.

[0163] By continuing this movement pattern, the X-ray fluoroscopic image P n+t In the X-ray fluoroscopic image P n+t The marker 10 is expected to move to a position indicated by a reference symbol U1, which corresponds to the outside of the imaging range of the X-ray fluoroscopic image P. n+t When the marker detection unit 21 searches for the marker 10 by template matching in a state where the marker 10 has moved outside the imaging range of the marker 10, the marker detection unit 21 detects a similar object R, which is an object different from the marker 10. Then, the search area setting unit 22 sets a search area S based on the position of the similar object R. As a result, the X-ray fluoroscopic image P n+t In the X-ray fluoroscopic image P acquired thereafter, the search area S continues to be set so as to track the similar object R.

[0164] In this case, as shown in Fig. 28, even if the marker 10 later returns to the inside of the X-ray fluoroscopic image P and moves to the position indicated by the symbol U2, the search area S is set to track a similar target R located away from the returned marker 10. Therefore, the returned marker 10 is likely to fall outside the search area S. As a result, the genuine marker 10 is excluded from the search target of the marker detection unit 21, and therefore the marker 10 will not be detected by the marker detection unit 21 even if it returns to the image. In this way, a problem occurs in that the detection accuracy of the marker 10 decreases thereafter due to the marker 10 moving out of the range of the X-ray fluoroscopic image P.

[0165] Therefore, in the second embodiment, a state in which the position of the marker 10 is expected to move from within the imaging range of the X-ray fluoroscopic image P to outside the imaging range is detected as a frame-out state. When the frame-out state is detected, the search area update unit 25 is switched to an area fixed state to interrupt updating of information in the search area storage unit 34. In other words, by switching the search area update unit 25 to the area fixed state, the position of the search area S set by the search area setting unit 22 is fixed in the X-ray fluoroscopic image P generated thereafter.

[0166] After step S5C is completed, the process branches according to the most recently updated search area S (branch Q8). n+1 If the entire region is included within the shooting range of the X-ray fluoroscopic image P, the second condition for the frame-out state is not satisfied, so the frame-out detection unit 103 does not detect the frame-out state. If the frame-out state is not detected, the update state switching unit 108 maintains the search area update unit 25 in the normal state and ends step S5 (decision A5).

[0167] On the other hand, the current detection target F n is in high speed movement state and the updated search area S n+1 reaches outside the range of the X-ray fluoroscopic image P, both of the conditions for the frame-out state are satisfied. Therefore, the frame-out detection unit 103 detects the occurrence of the frame-out state. When the frame-out detection unit 103 detects the frame-out state, the update state switching unit 108 switches the search area update unit 25 from the normal state to the area fixed state, and ends step S5 (decision A6). Then, when step S6 is completed, the process returns to step S1 again, and steps S1 to S6 are performed with the search area update unit 25 in the area fixed state.

[0168] When the search area update unit 25 is switched to the area fixed state, the search area update unit 25 continues to update the search area S based on the position of the detection target F detected at the time when the frame-out state was detected. In other words, when the (n+1)th steps S1 to S6 are repeated in a state in which the search area update unit 25 is switched to the area fixed state in the nth step S5, the position of the detection target F detected by the marker detection unit 21 in the (n+1)th step S3 is n+1 The position information is not stored in the reference position storage unit 109. That is, at the time when the (n+1)th step S4 is started, the information on the reference position stored in the reference position storage unit 109 is the detection target position B n+1 The position of the detection target B stored at the time the frame-out state was detected is not overwritten. n As a result, the information stored in the search area storage unit 34 is the detection target position B n Search area S with reference position n+1 (see FIG. 24, step S4D).

[0169] The reference position is detection target position B n By maintaining the above, the detection target F detected in the (n+1)th step S3 n+1 Regardless of the position of the detection target position B, the search area update unit 25 updates the detection target position B in the (n+1)th step S4. n The search area S is updated with the reference position. While the search area update unit 25 is in the area fixed state, the information of the reference position stored in the reference position storage unit 109 is not changed. As a result, until the area fixed state is released, the search area setting unit 22 updates the search area S with the reference position P n+1 , P n+2 , P n+3 For example, the most recently updated search area at the time the frame-out state was detected n+1 In other words, the position of the search area S set in the fluoroscopic X-ray image P is fixed until the area fixing state is released.

[0170] A specific example of the area fixed state is shown in FIG. 29. X-ray fluoroscopic image P generated after t frames n+t When updating the search area S for the X-ray fluoroscopic image P, the marker 10 n+t Even though you have moved outside the search area n+1 The search area S is updated to be the same position as n+t Since the search area update unit 25 is in the area fixed state, the X-ray fluoroscopic image P n+t Even if a similar object R is captured in the image, the search area S is based on the similar object R. n+t Therefore, it is possible to prevent a decrease in the detection accuracy of the marker 10 in the subsequently generated fluoroscopic X-ray image P due to the marker 10 moving out of the shooting range of the fluoroscopic X-ray image P.

[0171] When the search area update unit 25 is switched to the area fixed state, it is preferable that the search area update unit 25 switches to the area fixed state in a state in which the most recently updated search area S is enlarged and corrected, and updated to the enlarged and corrected search area S. Furthermore, when the most recently updated search area S intersects with the outer edge PL of the X-ray fluoroscopic image P, it is even more preferable to perform a correction to move the position of the most recently updated search area S to a position where it abuts against the outer edge PL of the X-ray fluoroscopic image P, and transition to the area fixed state in a state in which the search area S with the corrected position is updated.

[0172] Figure 30 shows the most recently updated search area S n+1 The search area S with the position and size corrected n+1A That is, the search area S n+1A is the search area S n+1 The search area S is enlarged by a specified magnification ratio. n+1A The center position of the search area S n+1 Center position of the detection target F n The position of the search area S is corrected. n+1A The direction and distance to correct the center position of the search area S n+1AThe search area S can be appropriately set so that the search area S abuts on the outer edge PL of the X-ray fluoroscopic image P. The search area update unit 25 updates the information of the search area S n+1 From search area S n+1A Once the area is updated, the area transitions to a fixed state.

[0173] When such a correction is performed, the detection object F n The movement state of the detection target F n Search area S with reference position n+1 After a frame-out condition is detected, the search area S n+1 Correct the position and size of the search area S n+1A The information stored in the search area storage unit 34 is calculated based on the search area S n+1A In the state where the search area is updated to the area S, the update state switching unit 108 switches the search area update unit 25 to the area fixed state. As a result, until the area fixed state is released, each of the generated X-ray fluoroscopic images P includes the search area S. n+1A will continue to be set.

[0174] Search Area S Search Area S n+1A By fixing the marker 10 in the enlarged and corrected state, even if the marker 10 returns to the imaging range of the X-ray fluoroscopic image P along an elliptical orbit K2 as shown in FIG. 31, the marker 10 that has returned to the imaging range can be more reliably located within the search area S. n+1A In other words, even if the position of the marker 10 when it moves outside the X-ray fluoroscopic image P differs from the position of the marker 10 when it returns to the inside of the X-ray fluoroscopic image P, the returning marker 10 can be reliably included within the search area S. n+1A In this way, by fixing the search area S in an enlarged and corrected state, the detection accuracy of the marker 10 can be improved. Also, by correcting the position so that the entire search area S is included in the X-ray fluoroscopic image P, the range of the search area S in the X-ray fluoroscopic image P becomes wider. As a result, the detection accuracy of the marker 10 can be further improved.

[0175] Next, an overview of step S5 when the search area update unit 25 is in the area fixed state will be described. When the search area update unit 25 is in the area fixed state, in step S5, it is determined whether or not to switch the search area update unit 25 from the area fixed state to the normal state. That is, the presence or absence of the marker return state is determined by the processes of steps S5D to S5F. The marker return state is a state in which the marker 10 has returned from outside the range of the X-ray fluoroscopic image P to within the range. That is, as shown in FIG. 27, since the detection target F (marker 10) generally moves along a periodic orbit K2, even if it moves outside the range of the X-ray fluoroscopic image P (see arrow W1), it will return again to the range of the X-ray fluoroscopic image P after a time has passed (see arrow W2).

[0176] When the marker return state is not detected, the search area update unit 25 maintains the area fixed state (determination A7). When the marker return state is detected, the search area update unit 25 switches from the area fixed state to the normal state (determination A8). Details of steps S5D to S5F will be described below. Note that, here, the X-ray fluoroscopic image P n After the frame-out state is detected in, the newest X-ray fluoroscopic image P is the X-ray fluoroscopic image P k is assumed to have been generated.

[0177] Step S5D (calculation of movement vector) When the search area update unit 25 is in the area fixed state, the process proceeds to step S5D when step S5 is started. In step S5D, the motion vector V of the detection target F at the current time and the motion vector V of the detection target F at the time when the frame-out state was detected are calculated. That is, the motion vector calculation unit 27 calculates the motion vector V of the detection target F at the current time and the motion vector V of the detection target F at the time when the frame-out state was detected. n The movement vector V n and detection target F k The movement vector V k The method for calculating the movement vector V is the same as that in the first embodiment. n is the detection target F n-1 Location information and detection target F nThe movement vector V k is the detection target F k-1 Location information and detection target F k The position information of the detection object F can be used to calculate the position information of the detection object F. n-1 , detection target F n , detection target F k-1 , and the detection target F k 1 shows an example of the position of

[0178] Step S5E (Getting the score) Movement vector V n and the movement vector V k After calculating the matching score C of the detection target F at the current time and the matching score C of the detection target F at the time when the frame-out state was detected. n Matching score C n Information on the detection target F k Matching score C k The matching score C is calculated in step S3 in which the marker detection unit 21 detects the detection target F from the X-ray fluoroscopic image P, and is stored in the storage unit 15. The score acquisition unit 105 reads out and acquires the information on the matching score C from the storage unit 15.

[0179] Step S5F (determining marker return conditions) When the information of the movement vector V and the matching score C is acquired, the information of the movement vector V and the matching score C is used to detect the current detection target F k If the marker return condition is satisfied for two consecutive frames, the marker return detection unit 107 detects the occurrence of a marker return state.

[0180] In this embodiment, it is determined that the marker return condition is met when the following two conditions are met. The first condition in the marker return condition is that the current movement vector V and the movement vector V at the time when the frame-out state was detected are in opposite directions. That is, the movement vector Vn and the movement vector V k The dot product with (V n ·V k ) satisfies the formula (1) using the value of the predetermined value D1, it is determined that the first condition is met. -1≦(V n ·V k )≦D1 ……(1)

[0181] The predetermined value D1 is a predetermined negative number close to -1, and for example, a value of about -0.7 to -0.8 is used. n ·V k ) is close to (-1), the motion vector V of the detection target F detected at the time the frame-out state was detected n and the current detection target F k The movement vector V k and the angle formed is determined to be close to 180°. The marker 10 generally moves along a periodic orbit due to breathing of the subject M, etc. Therefore, the angle between the movement direction of the marker 10 returning from the outside to the inside of the X-ray fluoroscopic image P and the movement direction of the marker 10 moving from the inside to the outside of the X-ray fluoroscopic image P is considered to be close to 180°. Therefore, the inner product (V n ·V k ) satisfies the formula (1), it can be determined that the first condition in the marker return conditions is satisfied.

[0182] The second condition in the marker return condition is that the current matching score C and the matching score C at the time when the frame-out state was detected are close to each other. That is, the current matching score C n and the matching score C when the frame-out state is detected. k The score ratio (C n / C k ) satisfies the formula (2) using the value of the predetermined value D2, it is determined that the second condition is met. D2≦(C n / C k )≦1 ……(2)

[0183] The predetermined value D2 is a predetermined positive number close to 1, and an example of the predetermined value D2 is a value of about 0.7 to 0.9. n / C k ) satisfies condition (2), the detection target F detected after the frame-out state k is the detection target F detected before moving outside the X-ray fluoroscopic image P. n Similarly, the matching score C is high. Therefore, the detection target F k It can be determined that there is a high possibility that the marker 10 is not a similar object R but a genuine marker 10.

[0184] The marker return detection unit 107 calculates the inner product (V n ·V k ) satisfies the condition in (1) and the score ratio (C n / C k ) satisfies the condition (2), the kth acquired X-ray fluoroscopic image P k In the detection target F k It is determined that the frame return condition is satisfied.

[0185] However, even if the frame return condition is satisfied in one X-ray fluoroscopic image P, it is not sufficient to determine that a frame return state in which the marker 10 returns to the inside of the X-ray fluoroscopic image P has definitely occurred. k The movement vector V k However, the detection target F, which happened to be marker 10, n The movement vector V n Therefore, in order to eliminate the possibility that an object other than the marker 10 accidentally satisfied the frame return condition, it is preferable to check the frame return condition in a plurality of consecutive X-ray fluoroscopic images P.

[0186] In this embodiment, when the frame return condition is satisfied in two X-ray fluoroscopic images P acquired consecutively after the search area update unit 25 is switched to the area fixed state, the frame return state detects the occurrence of the frame return state. kIf the frame return condition is satisfied in step S5, the marker return detection unit 107 detects the X-ray fluoroscopic image P k+1 It is determined whether the frame return condition is satisfied.

[0187] That is, when the (k+1)th step S5 is started, the process proceeds to step S5D in the same manner as the kth step S5. Then, the motion vector calculation unit 27 calculates the motion vector of the detection object F k Location information and detection target F k+1 Based on the position information of the detection target F k+1 The movement vector V k+1 After step S5D is completed, the process proceeds to step S5E, in which the score acquisition unit 105 calculates the detection object F k+1 Matching score C k+1 The data is read and acquired.

[0188] Movement vector V k+1 and the matching score C k+1 When the information on the detection target F is acquired, the process proceeds to step S5F. n The movement vector V n and detection target F k+1 The movement vector V k+1 The dot product with (V n ·V k+1 ) and the detection target F n and detection target F k+1 Score ratio with (C n / C k+1 ) is calculated. If the following conditional expressions (3) and (4) are satisfied, the marker return detection unit 107 determines that the marker return condition has been satisfied twice consecutively. -1≦(V n ·V k+1 ) <D1 ……(3) D2<(C n / C k+1 )≦1 ……(4)

[0189] After step S5F is completed, the process branches depending on whether the marker return condition is satisfied twice consecutively (branch Q9). If the marker return condition is satisfied twice consecutively, the marker return detection unit 107 detects the occurrence of the marker return state. In other words, if the marker return condition is satisfied in each of two X-ray fluoroscopic images P generated consecutively, the marker return detection unit 107 detects the occurrence of the marker return state. If the marker return condition is not satisfied in the current step S5, or if the marker return condition is satisfied at the current time but not satisfied in the previous step S5, the marker return detection unit 107 does not detect the marker return state. If the marker return detection unit 107 does not detect the marker return state, the update state switching unit 108 maintains the search area update unit 25 in the area fixed state and ends step S5 (decision A7).

[0190] On the other hand, if the occurrence of the marker return state is detected, the update state switching unit 108 switches the search area update unit 25 from the area fixed state to the normal state and ends step S5 (decision A8). By switching the search area update unit 25 to the normal state, it becomes possible to update the reference position information stored in the reference position storage unit 109 in the process of steps S1 to S6 that is performed next time. As a result, in step S4 that is performed next time, the search area S is updated to a new position centered on the detection target F detected in step S3.

[0191] In this way, in the second embodiment, the presence or absence of a frame-out state and a marker return state is detected in step S5. Then, in response to the occurrence of the frame-out state or the marker return state, the search area update unit 25 is appropriately switched between the normal state and the area fixed state.

[0192] When the frame-out state is detected, the search area update unit 25 transitions from the normal state to the area fixed state. When the search area update unit 25 is in the area fixed state, the reference position of the search area S is not updated even if a new X-ray fluoroscopic image P is generated. When the frame-out state is detected, it is assumed that the marker 10 will move outside the X-ray fluoroscopic image P thereafter. Therefore, even if the marker 10 moves outside the X-ray fluoroscopic image P after the frame-out state occurs, the search area S is fixed to the position at the time of the frame-out state occurrence. Therefore, it is possible to avoid a situation where a similar object R is detected by searching an X-ray fluoroscopic image P in which the marker 10 is not reflected, and the search area S is set to an inappropriate position based on the similar object R.

[0193] When a marker return state is detected after a frame-out state is detected, the search area update unit 25 transitions from the area fixed state to the normal state. When the search area update unit 25 enters the normal state, updating of the reference position is resumed. That is, the reference position of the search area S is updated according to the position of the detection target F detected by the marker detection unit 21 from the latest fluoroscopic X-ray image P. When the marker 10 returns to the inside of the fluoroscopic X-ray image P, the marker detection unit 21 can accurately detect the marker 10 from the fluoroscopic X-ray image P. Therefore, by switching the search area update unit 25 to the normal state, the process of tracking the marker 10 shown in the new fluoroscopic X-ray image P can be resumed.

[0194] The marker 10 placed inside the body of the subject M moves mainly due to the breathing or pulsation of the subject M. That is, the marker 10 generally moves periodically along a linear or elliptical trajectory with a small ellipticity. Therefore, as shown in FIG. 33, when the marker 10 temporarily moves outside the X-ray fluoroscopic image P, the marker 10A moving outside the X-ray fluoroscopic image P intersects with the outer edge PL of the X-ray fluoroscopic image P at a position F. out is a position F at which the marker 10B returning to the inside of the X-ray fluoroscopic image P intersects with the outer edge PL of the X-ray fluoroscopic image P. inThe position of the search area S is fixed at the position at the time when the frame-out state was detected until the marker return state is detected. Therefore, the marker 10 returning to the inside of the X-ray fluoroscopic image P is more reliably included within the search area S whose position is fixed. Therefore, it is possible to quickly and accurately track the marker 10 that has returned to the inside of the X-ray fluoroscopic image P.

[0195] <Effects of the configuration of the embodiment> (Item 1) An X-ray fluoroscopy apparatus 1 according to the first embodiment includes an X-ray tube (5, 7) that irradiates an object M with X-rays, an X-ray detector (6, 8) that detects X-rays transmitted through the object M, an image generating unit 19 that uses a detection signal output by the X-ray detector (6, 8) to continuously generate a plurality of X-ray fluoroscopic images P including a marker 10 placed inside the body of the object M or a specific portion of the object M, a search area setting unit 22 that sets a search area S for each of the plurality of X-ray fluoroscopic images P, a tracked object detection unit 21 that detects the marker 10 or the specific portion as a tracked object by searching inside the search area S set in each of the X-ray fluoroscopic images P, and a detection object determination unit 23 that determines whether a detection object F detected as a tracked object by the tracked object detection unit 21 in each of the plurality of X-ray fluoroscopic images P is a tracked object or a similar object R, and the plurality of X-ray fluoroscopic images P generated by the image generating unit are a first X-ray fluoroscopic image (P n ) and a second X-ray fluoroscopy image (P n+1 ), and a third X-ray fluoroscopic image (P n-1 ), and the search area setting unit 22 is configured such that the detection target determination unit 23 determines whether the first X-ray fluoroscopic image (P n ) in the detection target (F n ) is determined to be the tracking target, the first X-ray fluoroscopy image (P n ) detection target (F n ) based on the position information of the second X-ray fluoroscopy image (P n+1 ) to the search area (S n+1 ), and the detection target determination unit 23 detects the first X-ray fluoroscopic image (P n) detection target (F n ) is judged to be a similar object R, the third X-ray fluoroscopic image (P n-1 ) in the detection target (F n-1 ) based on the position information of the second X-ray fluoroscopy image (P n+1 ) to the search area (S n+1 ) to set the

[0196] According to the X-ray fluoroscopy device described in paragraph 1, the device includes a detection target determination unit 23 that determines whether a detection target F detected by a tracking target detection unit in a first X-ray fluoroscopy image is a tracking target or a similar target R. When the detection target determination unit 23 determines that the detection target F is a tracking target, the search area setting unit sets a search area in a second X-ray fluoroscopy image generated at a time later than the first X-ray fluoroscopy image, based on position information of the detection target in the first X-ray fluoroscopy image. When the detection target determination unit 23 determines that the detection target F is a similar target R, the search area setting unit sets a search area in the second X-ray fluoroscopy image, based on position information of the detection target in a third X-ray fluoroscopy image. The third X-ray fluoroscopy image is an X-ray fluoroscopy image that is generated at a time earlier than the first X-ray fluoroscopy image and in which the detection target determination unit 23 determines that the detection target F is a tracking target. With this configuration, even if the tracking target detection unit 21 detects a similar target R that is a non-tracking target in the first X-ray fluoroscopic image, it is possible to avoid updating the search area S in the second X-ray fluoroscopic image generated after the first X-ray fluoroscopic image so as to track the similar target R in the first X-ray fluoroscopic image. Therefore, it is possible to continue to set the search area S with high accuracy according to the position of the tracking target without being affected by the similar target R.

[0197] (Item 2) The X-ray fluoroscopy device described in item 1 further includes a motion vector calculation unit 27 that calculates the movement distance G and motion vector V of the detection target F in the first X-ray fluoroscopy image based on the distance and direction of movement of the detection target F between the first X-ray fluoroscopy image and the third X-ray fluoroscopy image, and a motion state determination unit 29 that determines whether the detection target in the first X-ray fluoroscopy image is in a high-speed or low-speed moving state based on the motion vector information, and the detection target determination unit 23 is configured so that the criteria for determining whether the detection target F in the first X-ray fluoroscopy image is a tracked target or a similar target R are different when the detection target in the first X-ray fluoroscopy image is determined to be in a high-speed moving state and when it is determined to be in a low-speed moving state.

[0198] According to the X-ray fluoroscopy apparatus described in the second aspect, the motion vector calculation unit 27 calculates the motion vector V of the detection target F in the first X-ray fluoroscopy image. The motion state determination unit 29 determines whether the detection target F in the first X-ray fluoroscopy image is in a high-speed or low-speed motion state based on information on the motion vector V of the detection target F. A tracking target, such as the marker 10, has two types of motion patterns, a high-speed motion state and a low-speed motion state, and the aspects of the motion distance or motion direction are different in each motion pattern. Therefore, by determining whether the detection target F is in a high-speed or low-speed motion state and applying different determination criteria when the detection target F is determined to be in a high-speed motion state and when the detection target F is determined to be in a low-speed motion state, the detection target F can be determined with higher accuracy.

[0199] (Item 3) In the X-ray fluoroscopy device according to item 2, the first X-ray fluoroscopy image P n A plurality of X-ray fluoroscopic images P that have been generated before and in which the detection target is determined to be a tracking target by the detection target determination unit n-1 ~P n-4 The average moving distance G of the detection target F in av The moving state determination unit 29 includes an average distance calculation unit 28 that calculates an average distance between the first X-ray fluoroscopic image P n Detection target F n Distance traveled by G nand the average distance G calculated by the average distance calculation unit 28 av If both of these are equal to or greater than the predetermined value T1, the first X-ray fluoroscopic image P n Detection target F n is judged to be in a high-speed moving state, and the first X-ray fluoroscopic image P n Detection target F n Distance traveled by G n and the average distance G calculated by the average distance calculation unit 28 av is less than a predetermined value T1, the low-speed movement state is determined.

[0200] According to the X-ray fluoroscopy apparatus described in the third aspect, the average distance calculation unit 28 calculates the first X-ray fluoroscopy image P n A plurality of X-ray fluoroscopic images P that have been generated before and in which the detection target is determined to be a tracking target by the detection target determination unit n-1 ~P n-4 The average moving distance G of the detection target F in av That is, the average value G av is the first X-ray fluoroscopic image P n The moving state determination unit 29 calculates the average moving distance G av And the first X-ray fluoroscopic image P n Detection target F n Distance traveled by G n Based on the values ​​of and, the first X-ray fluoroscopic image P n Detection target F n In this case, the latest moving distance G is determined to be a high-speed moving state or a low-speed moving state every time an X-ray fluoroscopy image P is generated by X-ray fluoroscopy. n and the average moving distance of the tracked object G av Since the detection target F can be calculated, n The movement state of the object can be determined more easily and quickly.

[0201] (4) In the X-ray fluoroscopy device according to the second or third aspect, the first X-ray fluoroscopy image P n Detection target F n When the moving state determination unit 29 determines that the object is moving at high speed, the detection object determination unit 23 detects the first X-ray fluoroscopic image P nDetection target F n The movement vector V n and the third X-ray fluoroscopic image P n-1 Detection target F n-1 The movement vector V n-1 The dot product with (V n ·V n-1 ) is equal to or greater than zero, the first X-ray fluoroscopic image P n Detection target F n is determined to be the tracking target, while the inner product (V n ·V n-1 ) is a negative value, the first X-ray fluoroscopic image P n Detection target P in n is a similar object R, and the first X-ray fluoroscopic image P n Detection target P in n When the moving state determination unit 29 determines that the object is moving at a low speed, the detection object determination unit 23 detects the first X-ray fluoroscopic image P n Detection target F n Distance traveled by G n and the average value G calculated by the average distance calculation unit 28 av Deviation rate from (G n / G av ) is less than the predetermined value T2, the first X-ray fluoroscopic image P n Detection target F n is determined to be the tracking target, while the deviation rate (G n / G av ) is equal to or greater than the predetermined value T2, the detection object F n is a similar object R.

[0202] According to the X-ray fluoroscopy apparatus described in the fourth aspect, the first X-ray fluoroscopy image P n Detection target F n is determined to be in a high speed moving state, the first X-ray fluoroscopic image P n Detection target F n The movement vector V n and the third X-ray fluoroscopic image P n-1 Detection target F n-1 The movement vector V n-1 The dot product with (V n ·V n-1), the detection target determination unit 23 makes a determination. n ·V n-1 ) is equal to or greater than zero, the first X-ray fluoroscopic image P n Detection target F n is determined to be a genuine tracking target, while if the inner product is negative, the detection target F n is determined to be a similar object R different from the tracked object. If the inner product is a negative value, the first X-ray fluoroscopic image P n Detection target F n The movement vector V n and the third X-ray fluoroscopic image P n-1 Detection target F n-1 The movement vector V n-1 The angle between the vector and the target object is more than 90°. The direction of movement of the target object does not change significantly when moving at high speed. Therefore, by using the inner product of the motion vector V as the criterion, the detection target F n This makes it possible to more reliably determine whether or not a tracking target is a genuine one.

[0203] In addition, the detection target F n is determined to be in a low-speed moving state, the first X-ray fluoroscopic image P n Detection target F n Distance traveled by G n and the average value G av Deviation rate from (G n / G av The detection target determination unit 23 performs the determination based on the average value G av corresponds to the average moving distance of the tracked object. The moving distance of the genuine tracked object does not change significantly when moving at a low speed. Therefore, when the deviation rate exceeds a predetermined value, the first X-ray fluoroscopic image P n Detection target F n It can be determined that the movement pattern of the target is different from that of the real target. n / G av ) as the criterion for the detection target F n This can improve the accuracy of judgment.

[0204] (Item 5) An X-ray fluoroscopy apparatus 101 according to the second embodiment includes an X-ray tube (5, 7) that irradiates an object with X-rays, an X-ray detector (6, 8) that detects X-rays transmitted through the object, an image generating unit 19 that generates a plurality of X-ray fluoroscopic images P using detection signals output by the X-ray detector (6, 8), a search area setting unit 22 that sets a search area S for each of the plurality of X-ray fluoroscopic images P, a tracking target detection unit 21 that detects a marker 10 placed inside the body of the object M or a specific part of the object as a tracking target by searching inside the search area S set in each of the X-ray fluoroscopic images P, and The apparatus includes a frame-out detection unit 103 that detects the occurrence of a frame-out state in which a part of a search area S set in the X-ray fluoroscopic image P is located outside the X-ray fluoroscopic image P, and a tracked target return detection unit 107 that detects the occurrence of a tracked target return state in which the tracked target returns from the outside to the inside of the X-ray fluoroscopic image P. When a frame-out state is detected, the search area setting unit 22 sets a search area S based on position information of the tracked target detected in the X-ray fluoroscopic image P generated at the time the frame-out state was detected, until the tracked target return state is detected.

[0205] According to the X-ray fluoroscopy device described in the fifth aspect, the device includes a frame-out detection unit 103 that detects the occurrence of a frame-out state in which a part of the search area S is set outside the X-ray fluoroscopic image P, and a tracked target return detection unit 107 that detects the occurrence of a tracked target return state in which the tracked target such as the marker 10 returns from the outside to the inside of the X-ray fluoroscopic image P. When the frame-out state is detected, the search area setting unit 22 sets the search area S based on the position information of the tracked target detected in the X-ray fluoroscopic image P generated at the time when the frame-out state is detected until the tracked target return state is detected. With this configuration, when the tracked target moves outside the X-ray fluoroscopic image P, the occurrence of the frame-out state is quickly detected and the area is shifted to a fixed state. Therefore, it is possible to avoid the tracked target detection unit 21 detecting a similar target R due to the tracked target moving outside the X-ray fluoroscopic image P and setting the search area S at an inappropriate position based on the position of the similar target R. Therefore, even if a tracking target such as the marker 10 temporarily moves outside the X-ray fluoroscopic image P due to the subject's body movement, the search area S is set at an appropriate position, making it possible to track the tracking target with high accuracy.

[0206] (Item 6) In the X-ray fluoroscopy apparatus described in Item 5, the frame-out detection unit 103 is configured to detect the occurrence of a frame-out state when the search area S abuts on or intersects with the outer edge portion PL of the X-ray fluoroscopic image P. In this case, the occurrence of the frame-out state can be more accurately detected by detecting the positional relationship between the search area S and the outer edge portion PL of the X-ray fluoroscopic image P. Therefore, it is possible to more reliably prevent the search area S from being updated to an inappropriate position due to the tracking target moving outside the X-ray fluoroscopic image P.

[0207] (Item 7) In the X-ray fluoroscopy apparatus described in item 5, when the occurrence of a frame-out state is detected, the search area setting unit 22 enlarges the size of the search area S at the time when the frame-out state is detected by a predetermined enlargement rate and sets the search area S in the X-ray fluoroscopy image P to be generated next so that the enlarged search area S abuts on the outer edge part PL of the X-ray fluoroscopy image P. In this case, a correction is performed to enlarge and displace the search area S at the time when the frame-out state is detected. Then, the search area S that has been corrected in enlargement and displacement is set in the X-ray fluoroscopy image P to be generated next. The correction makes the range of the search area S set in the X-ray fluoroscopy image P to be generated later wider. As a result, the tracking target that returns to the inside of the X-ray fluoroscopy image P later can be captured more reliably inside the search area S. Therefore, the detection accuracy of the tracking target can be further improved.

[0208] (Item 8) Furthermore, in the X-ray fluoroscopy device described in Item 5, the search area setting unit 22 is configured, when a frame-out state is detected, to transition to an area fixed state in which the search area S is set based on the position information of the tracking target F detected in the X-ray fluoroscopy image P generated at the time the frame-out state is detected, until the tracking target return state is detected, and to release the area fixed state when the tracking target return state is detected after the frame-out state is detected, and to resume the state in which the search area S is set based on the position information of the tracking target F detected from the latest X-ray fluoroscopy image P.

[0209] According to the X-ray fluoroscopy device described in paragraph 8, when a frame-out state is detected, the state transitions to an area fixed state. In the area fixed state, a search area S is set based on position information of the tracking target F at the time of detection of the frame-out state. By transitioning to the area fixed state, it is possible to avoid setting the search area S at an inappropriate position based on the position of the similar target R even if the tracking target moves outside the X-ray fluoroscopy image P. When a tracking target return state is detected after a frame-out state is detected, the area fixed state is released, and a state in which the search area S is set based on the latest position information of the tracking target F is resumed. When the tracking target return state is detected, the tracking target has returned within the range of the X-ray fluoroscopy image. Therefore, by releasing the area fixed state, the process of tracking the returned tracking target with high accuracy can be quickly resumed.

[0210] (Item 9) The X-ray fluoroscopy device described in Item 5 further includes a score acquisition unit 105 that acquires a matching score C of the detection target F detected as a tracking target by the tracking target detection unit 21 for each X-ray fluoroscopy image P, and a movement vector calculation unit 27 that calculates a movement distance G and a movement vector V of the detection target F in the first X-ray fluoroscopy image based on the distance and direction of movement of the detection target between the first X-ray fluoroscopy image and a second X-ray fluoroscopy image generated at a time earlier than the first X-ray fluoroscopy image, and the tracking target return detection unit 107 is configured to detect the occurrence of a tracking target return state in the first X-ray fluoroscopy image when the movement vector of the detection target F in the first X-ray fluoroscopy image and the movement vector of the detection target calculated when a frame-out state occurs are in opposite directions, and the ratio of the matching score of the detection target in the first X-ray fluoroscopy image to the matching score C calculated when the frame-out state occurs is equal to or greater than a predetermined value D2.

[0211] The X-ray fluoroscopy apparatus described in paragraph 9 includes a score acquisition unit 105 that acquires a matching score C of the detection target F, and a movement vector calculation unit 27 that calculates a movement vector V of the detection target F. The tracking target return detection unit 107 detects the occurrence of a marker return state when the movement vector V of the detection target F at the time of occurrence of the frame-out state and the movement vector V of the detection target F in the first X-ray fluoroscopy image are in opposite directions, and the ratio of the matching score C in the first X-ray fluoroscopy image to the matching score C at the time of occurrence of the frame-out state is equal to or greater than a predetermined value D2. When such conditions are satisfied, the behavior of the detection target F in the first X-ray fluoroscopy image is similar to the behavior of the tracking target returning inside the X-ray fluoroscopy image P, so it can be determined that the tracking target return state has occurred. Therefore, the detection accuracy of the tracking target return state can be improved, and the tracking target return state can be detected more easily.

[0212] <Other Examples> It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention includes the claims, and all modifications within the meaning and scope equivalent to the claims. For example, the present invention can be modified as follows.

[0213] (1) In the above-described X-ray fluoroscopy device, the first embodiment and the second embodiment are not limited to being independent configurations, and the configuration of the first embodiment and the configuration of the second embodiment may be combined. That is, the device may be provided with both the configuration of the first embodiment, which includes the detection object determination unit 23 and the like and determines the detection object F, and the configuration of the second embodiment, which includes the update state switching unit 108 and the like and switches the state of the search area update unit 25 by detecting the frame-out state and the marker return state.

[0214] 34 is a functional block diagram showing an X-ray fluoroscope 201 having the configuration of the first embodiment and the configuration of the second embodiment. In addition to the configuration common to the first and second embodiments, the main control unit 9 of the X-ray fluoroscope 201 according to this modified embodiment is provided with a detection target determination unit 23, which is a configuration characteristic of the first embodiment, and a frame-out detection unit 103, a score acquisition unit 105, a marker return detection unit 107, and an update state switching unit 108, which are configuration characteristic of the second embodiment. Furthermore, the storage unit 15 of the X-ray fluoroscope 201 is provided with a template storage unit 31, a genuine marker storage unit 33, a search area storage unit 34, and a reference position storage unit 109.

[0215] In the X-ray fluoroscope 201 according to the modified embodiment, when the search area update unit 25 is in the normal state, the reference position storage unit 109 stores, as the reference position, the position information of the most recent genuine marker stored in the genuine marker storage unit 33. When the search area update unit 25 is in the area fixed state, even if the position information of the genuine marker stored in the genuine marker storage unit 33 is updated, the reference position storage unit 109 maintains the information of the reference position.

[0216] 35 is a flowchart showing an outline of the process of tracking the marker 10 using the X-ray fluoroscope 201 according to the modified embodiment. In the X-ray fluoroscope 201 according to the modified embodiment, the marker detector 21 judges the detection target F detected as the marker 10 (step S4), and also performs an operation of switching the state of the search area update unit 25 to a normal state or an area fixed state based on the search area S updated by the search area update unit 25 (step S6).

[0217] In the modified embodiment, the detection target F is determined by the detection target determination unit 23 in step S4. Therefore, similar to the first embodiment, even if the marker detection unit 21 detects a similar target R as a marker 10, the position information of the similar target R is not stored in the genuine marker storage unit 33. In other words, the position information of the similar target R is not used as the reference position of the search area S. Therefore, even if the similar target R is erroneously detected, it is possible to avoid updating the search area S to track the similar target R.

[0218] In the modified embodiment, in step S6, the presence or absence of a frame-out state and a marker return state is determined. Then, the update state switching unit 108 switches the search area update unit 25 to a normal state or an area fixed state according to the determination result. Therefore, even if a situation occurs in which the marker 10 moves outside the X-ray fluoroscopic image P, the search area update unit 25 has been switched to the area fixed state by detecting the frame-out state in advance. That is, while the marker 10 is moving outside the X-ray fluoroscopic image P, the position of the search area S is fixed. Therefore, it is possible to avoid a situation in which the similar object R is erroneously detected as the marker 10 due to the fact that the real marker 10 is not reflected in the X-ray fluoroscopic image P, and the search area S is updated to track the similar object R.

[0219] Then, when the marker 10 returns to the inside of the X-ray fluoroscopic image P again, the marker return state is quickly detected and the area fixed state of the search area update unit 25 is released. By releasing the area fixed state, the search area update unit 25 is switched to a normal state in which the search area S is updated based on the position of the marker 10. Therefore, highly accurate position information of the marker 10 can be quickly obtained.

[0220] (2) In the above-mentioned X-ray fluoroscopy device, when determining the moving state of the detection object F, the moving distance G n and the average travel distance G av Each of the values ​​of the current detection object F is compared with the same predetermined value T1, but this is not limited to this, and each value may be compared with a different threshold value.n Distance traveled by G n is equal to or greater than a predetermined value T1, and the average movement distance G av is equal to or greater than a predetermined value M1, n may be determined to be in a high speed moving state.

[0221] (3) In the above-mentioned X-ray fluoroscopy apparatus, the marker 10 is used as the tracking target, but the tracking target is not limited to the marker 10. That is, the steps S1 to S6 may be repeated with the specific site Bc of the subject M as the tracking target. The configuration with the specific site Bc as the tracking target is also called markerless tracking. Examples of the specific site Bc include a tumor or a specific organ. In the case of a modified example with the specific site Bc as the tracking target, an image showing the specific site Bc is used as the template image Tp. The marker detection unit 21 scans the inside of the search area S in the X-ray fluoroscopy image P to detect an object having the highest matching score C with the specific site Bc shown in the template image Tp as the detection target F. When the specific site Bc is used as the tracking target instead of the marker 10, it is not necessary to place the marker 10 inside the subject M, so that the burden on the subject M can be further reduced.

[0222] (4) In the X-ray fluoroscopy apparatus according to the second embodiment described above, the timing for executing the step of detecting the frame-out state is not limited to step S5 and may be changed as appropriate. As an example, the presence or absence of the frame-out state may be detected after completion of step S2 of setting a search area S for the X-ray fluoroscopic image P. In this case, if at least a part of the search area S set for the X-ray fluoroscopic image P abuts or intersects with the outer edge portion PL of the X-ray fluoroscopic image P, it can be determined that the second condition for the frame-out state is satisfied.

[0223] (5) In the X-ray fluoroscopy apparatus according to the second embodiment described above, the first condition for the occurrence of a frame-out state is that the detection target F is in a high-speed moving state, but this is not limiting. In other words, the frame-out state may be determined to have occurred when at least a part of the search area S abuts on or intersects with the outer edge PL of the X-ray fluoroscopy image P without being a necessary condition for the frame-out state that the detection target F is in a high-speed moving state. [Explanation of symbols]

[0224] 1...X-ray fluoroscopy device 3. Top plate 4. Foundation 5...X-ray tube 6...X-ray detector 7...X-ray tube 8...X-ray detector 9 ...Main control unit 10 ... Marker (tracking target) 11...Display section 13 ... Input section 15...Storage section 17 ... X-ray irradiation control unit 19...Image generation section 21 ... Marker detection unit 22 …Search area setting section 23 … Similar object determination section 25 … Search area update section 26 ... Marker position calculation unit 27 ...Movement vector calculation section 28...Average distance calculation section 29 ...Moving state determination unit 31 ... Template memory section 33 ... Genuine marker memory section 34 ... Search area memory section 103 ... Flameout detection unit 105 …Score Acquisition Section 107 ... Marker return detection unit 108 … Update state switching unit 109...Reference position storage unit P … X-ray fluoroscopic image S … Search area F … Detection target R … Similar objects B …Detection target position Tp …Template image

Claims

1. An X-ray tube that irradiates an object with X-rays; an X-ray detector for detecting X-rays transmitted through the subject; an image generating unit that generates a plurality of X-ray fluoroscopic images including a marker placed in the body of the subject or a specific part of the subject, using a detection signal output by the X-ray detector; a search area setting unit that sets a search area for each of the plurality of X-ray fluoroscopic images; a tracking target detection unit that detects the marker or the specific portion that is a tracking target by searching inside the search area that is set in each of the X-ray fluoroscopic images; a detection target determination unit that determines whether a detection target detected as the tracking target by the tracking target detection unit in each of the plurality of X-ray fluoroscopic images is the tracking target or an object different from the tracking target; Equipped with the plurality of X-ray fluoroscopic images generated by the image generating unit include a first X-ray fluoroscopic image, a second X-ray fluoroscopic image generated at a time later than the first X-ray fluoroscopic image, and a third X-ray fluoroscopic image generated at a time earlier than the first X-ray fluoroscopic image and in which the detection target determining unit has determined that the detection target is the tracking target, The search area setting unit is When the detection target determination unit determines that the detection target in the first X-ray fluoroscopic image is the tracking target, the search area is set in the second X-ray fluoroscopic image based on position information of the detection target in the first X-ray fluoroscopic image; An X-ray fluoroscopy device that, when the detection target determination unit determines that the detection target in the first X-ray fluoroscopy image is a target different from the tracking target, sets the search area in the second X-ray fluoroscopy image based on positional information of the detection target in the third X-ray fluoroscopy image.

2. 2. The X-ray fluoroscope according to claim 1, a motion vector calculation unit that calculates a motion distance and a motion vector of the detection object in the first X-ray fluoroscopic image based on a motion distance and a motion direction of the detection object between the first X-ray fluoroscopic image and the third X-ray fluoroscopic image; a movement state determination unit that determines whether the detection object in the first X-ray fluoroscopic image is in a high-speed movement state or a low-speed movement state based on information about the movement vector; Equipped with The detection object determination unit An X-ray fluoroscopy device configured such that the criteria for determining whether the detection object in the first X-ray fluoroscopy image is the tracked object or an object different from the tracked object are different when the detection object in the first X-ray fluoroscopy image is determined to be in the high-speed moving state and when the detection object is determined to be in the low-speed moving state.

3. 3. The X-ray fluoroscope according to claim 2, an average distance calculation unit that calculates an average value of moving distances of the detection target in a plurality of the X-ray fluoroscopic images that have been generated before the first X-ray fluoroscopic image and in which the detection target has been determined to be the tracking target by the detection target determination unit; The moving state determination unit is determining that the detection target in the first X-ray fluoroscopic image is in the high-speed moving state when both the moving distance of the detection target in the first X-ray fluoroscopic image and the average value calculated by the average distance calculation unit are equal to or greater than a predetermined value; An X-ray fluoroscopy device configured to determine that the detection object is in the low-speed movement state when either the movement distance of the detection object in the first X-ray fluoroscopy image or the average value calculated by the average distance calculation unit is less than the predetermined value.

4. The X-ray fluoroscope according to claim 2 or 3, When the moving state determination unit determines that the detection target in the first X-ray fluoroscopic image is in the high-speed moving state, the detection target determination unit is configured to determine that the detection target in the first X-ray fluoroscopic image is the tracking target when an inner product of a movement vector of the detection target in the first X-ray fluoroscopic image and a movement vector of the detection target in the third X-ray fluoroscopic image is equal to or greater than zero, and to determine that the detection target in the first X-ray fluoroscopic image is an object different from the tracking target when the inner product is a negative value; When the moving state determination unit determines that the detection target in the first X-ray fluoroscopic image is in the low-speed moving state, an average distance calculation unit that calculates an average distance between the moving distance of the detection target in the first X-ray fluoroscopy image and the average distance calculated by the average distance calculation unit; and a detection target determination unit that determines that the detection target in the first X-ray fluoroscopy image is the tracking target when a deviation rate between the moving distance of the detection target in the first X-ray fluoroscopy image and the average distance calculated by the average distance calculation unit is less than a second predetermined value, while determining that the detection target is an object different from the tracking target when the deviation rate is equal to or greater than the second predetermined value.

5. An X-ray tube that irradiates an object with X-rays; an X-ray detector for detecting X-rays transmitted through the subject; an image generating unit that generates a plurality of X-ray fluoroscopic images using a detection signal output by the X-ray detector; a search area setting unit that sets a search area for each of the plurality of X-ray fluoroscopic images; a tracking target detection unit that detects a marker placed in the body of the subject or a specific part of the subject as a tracking target by searching inside the search area set in each of the X-ray fluoroscopic images; a frame-out detection unit that detects the occurrence of a frame-out state in which a part of the search area set in the X-ray fluoroscopic image is located outside the X-ray fluoroscopic image; a tracking target return detection unit that detects the occurrence of a tracking target return state in which the tracking target returns from the outside to the inside of the X-ray fluoroscopic image; Equipped with The search area setting unit is When the frame-out state is detected, the search area is set based on position information of the tracking target detected in the X-ray fluoroscopy image generated at the time the frame-out state is detected, until the tracking target return state is detected.

6. 6. The X-ray fluoroscope according to claim 5, The frame-out detection unit is An x-ray fluoroscopy device configured to detect the occurrence of the frame-out condition when the search area abuts or intersects an outer edge of the fluoroscopic image.

7. 6. The X-ray fluoroscope according to claim 5, The search area setting unit is When the occurrence of the frame-out state is detected, an X-ray fluoroscopy device expands the size of the search area at the time the frame-out state was detected by a predetermined magnification rate and sets the search area in the next generated X-ray fluoroscopy image so that the search area abuts the outer edge of the X-ray fluoroscopy image.

8. 6. The X-ray fluoroscope according to claim 5, The search area setting unit is When the frame-out state is detected, a transition is made to an area fixing state in which the search area is set based on position information of the tracking target detected in the X-ray fluoroscopic image generated at the time when the frame-out state is detected until the tracking target return state is detected; An X-ray fluoroscopy device configured to release the area fixed state when the tracking target return state is detected after the frame-out state is detected, and to resume a state in which the search area is set based on position information of the tracking target detected from the latest X-ray fluoroscopy image.

9. 6. The X-ray fluoroscope according to claim 5, a score acquisition unit that acquires a matching score of the detection target detected as the tracking target by the tracking target detection unit for each of the X-ray fluoroscopic images; a motion vector calculation unit that calculates a movement distance and a movement vector of the detection object in the first X-ray fluoroscopic image based on a movement distance and a movement direction of the detection object between the first X-ray fluoroscopic image and the second X-ray fluoroscopic image generated at an earlier time than the first X-ray fluoroscopic image; Equipped with The tracking target return detection unit, An X-ray fluoroscopy device configured to detect occurrence of the tracking target return state in the first X-ray fluoroscopy image when a movement vector of the detection target in the first X-ray fluoroscopy image and a movement vector of the detection target calculated when the frame-out state occurs are in opposite directions, and a ratio of the matching score of the detection target in the first X-ray fluoroscopy image to the matching score calculated when the frame-out state occurs is equal to or greater than a third predetermined value.

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