X-ray imaging apparatus and device position detection method using x-ray image

Abstract

The invention provides an X-ray imaging apparatus and a method for detecting the position of a device using an X-ray image, which can reduce the influence of non-periodic motion generated in an interventional imaging process and monitor the three-dimensional position of the device with high precision. In interventional imaging, in order to monitor the position of a device, the position of the device is calculated by finding a combination of X-ray images in which the influence of body movement is minimized from among a plurality of X-ray images acquired at different imaging positions. At this time, the orientation of feature points extracted from the plurality of X-ray images is analyzed, the orientation of body movement occurring during the imaging process is classified, a combination of X-ray images for calculating the position of the device is selected on the basis of the classification result, and the position of the device is calculated.

Description

Technical Field

[0001] This invention relates to an X-ray imaging device, and more particularly to a technique for controlling the three-dimensional position of a treatment device inserted into the object of examination during interventional surgery, in which images of the object to be treated are obtained while the treatment is being performed. Background Technology

[0002] X-ray imaging devices can capture the characteristic structures of a subject in real time and are widely used in imaging procedures such as surgery (interventional radiography). During imaging, determining the device's position relative to the subject is extremely important. While X-ray imaging devices can capture the device's position within the projection plane in real time from the X-ray image, it is difficult to determine the position or structure along the projection direction.

[0003] In cone-beam computed tomography (CBCT), which acquires three-dimensional images by rotating the X-ray source and detector around the subject, the three-dimensional position of the device can be determined from the three-dimensional images. However, compared with X-ray imaging devices, CBCT has the following problems: acquiring one image takes time, and if there is movement of the subject during rotation, the positional accuracy of the device decreases.

[0004] In response, an X-ray imaging device is proposed that uses an X-ray source and an X-ray detector that are oscillatingly indicated, and uses X-ray images acquired at different perspective angles to calculate the depth of the device based on the positional relationship of the device in these X-ray images (Patent Document 1) or a technique for calculating the three-dimensional position (Patent Document 2).

[0005] Patent Document 1: Japanese Patent No. 5587861

[0006] Patent Document 2: Japanese Patent Application Publication No. 2022-91427

[0007] When using methods described in prior art and employing multiple image calculation devices to determine the target position, a problem arises because the imaging times of the multiple images differ: if the subject moves during the acquisition of multiple X-ray images, the accuracy of the position calculation deteriorates. In the technology described in Patent Document 2, to reduce the influence of body movement, a parameter representing the degree of influence of body movement is calculated in the combination of multiple images, and the three-dimensional position is calculated using the combination where the degree of influence of body movement is minimized, thereby preventing accuracy degradation. In this technology, for periodic movements such as breathing, a combination of images with approximately equal phases of body movement can be used, thus enabling the calculation of a highly accurate three-dimensional position.

[0008] However, sometimes unexpected movements may occur in the subject, such as physiological reflexes that differ from periodic movements like breathing (hereinafter referred to as non-periodic movements). If such non-periodic movements occur during the imaging process, especially during the monitoring of the device's position, even the technology described in Patent Document 2 may sometimes struggle to maintain the accuracy of position calculations. Summary of the Invention

[0009] The objective of this invention is to provide a technique for high-precision monitoring of the three-dimensional position of a device by reducing the influence of non-periodic motion that occurs during imaging, and to provide an X-ray imaging device that can accurately display the position of the device while continuously imaging.

[0010] In the interventional imaging of this invention, in order to monitor the device position, the combination of X-ray images with the least influence of body motion is determined from multiple X-ray images acquired at different shooting positions to calculate the device position. At this time, the movement of feature points extracted from multiple X-ray images is analyzed, the movement of body motion occurring during the shooting process is classified, and a combination of X-ray images for calculating the device position is selected based on the classification results.

[0011] That is, the X-ray imaging apparatus of the present invention comprises: an imaging unit having an X-ray source that irradiates X-rays and an X-ray detector disposed facing the X-ray source across the object to be inspected, and generating an X-ray image of the object to be inspected based on the X-rays transmitted through the object and detected by the X-ray detector; and a processor (computation unit) that analyzes multiple X-ray images taken at different irradiation angles to the object to be inspected, and calculates the three-dimensional position of the device inserted into the object to be inspected. The processor (computation unit) classifies the movement of the object to be inspected from the multiple X-ray images taken at different positions, selects a combination of two or more X-ray images with different irradiation angles from the multiple X-ray images according to the type of body movement classified, and uses the selected combination to calculate the three-dimensional position of the device.

[0012] Furthermore, the device position detection method using X-ray images of the present invention is a method for detecting the three-dimensional position of a device reflected in the X-ray images by using multiple X-ray images taken at different X-ray irradiation angles. The device position detection method is characterized by including the following steps: extracting feature points from each of the multiple X-ray images and calculating the movement vector of the feature points between the images; classifying the movement of the photographed object that occurs during the acquisition of the multiple X-ray images based on the movement vector; and selecting, based on the classified movement, a group of images acquired when no non-periodic movement occurs from the multiple X-ray images, and using the selected group of images to calculate the three-dimensional position of the device.

[0013] Additionally, in this specification, "different imaging positions" includes situations where the angle of X-rays irradiating the subject from the X-ray source is different, or has the same meaning, and may use "irradiation angle" or the opposite of it when "imaging position" is described.

[0014] Invention Effects

[0015] According to the present invention, based on the movement trajectory of a predetermined shape (feature point) reflected in the X-ray image, the type of body movement that occurs during the acquisition of multiple X-ray images with different irradiation angles for detecting the position of the device is determined, and the combination of X-ray images used for device position detection is adjusted according to whether the body movement is periodic or non-periodic. Thus, even in the case of non-periodic body movement, the influence of body movement can be eliminated to calculate the three-dimensional position of the device with high accuracy. Attached Figure Description

[0016] Figure 1 This is a diagram showing an overall outline of the X-ray imaging apparatus to which the present invention is applied.

[0017] Figure 2 This figure shows an example of an X-ray imaging apparatus to which the present invention is applied.

[0018] Figure 3 This is a diagram illustrating another example of an X-ray imaging apparatus to which the present invention is applied.

[0019] Figure 4 This is a functional block diagram of the processor in Implementation Method 1.

[0020] Figure 5 This is a diagram illustrating the processing flow of the processor based on Implementation Method 1.

[0021] Figure 6 It is a diagram representing images taken from different angles of illumination.

[0022] Figure 7 This is a diagram showing an example of feature points extracted from an X-ray image.

[0023] Figure 8 This diagram illustrates the determination of the types of bodily movements based on the bodily movement classification.

[0024] Figure 9 It is a diagram representing the types of bodily movement.

[0025] Figure 10 It is a diagram representing a group of images acquired in one type of bodily movement (Example 1).

[0026] Figure 11 This is a diagram representing a group of images acquired in another type of bodily movement (Example 2).

[0027] Figure 12 This is a diagram representing an example of a combination of images used to calculate parameters.

[0028] Figure 13 It is a diagram illustrating how the parameters are calculated.

[0029] Figure 14 This is a functional block diagram of the arithmetic unit in Embodiment 2.

[0030] Figure 15 This is a diagram illustrating the processing flow of the processor based on Implementation Method 2.

[0031] Figure 16 This is a diagram illustrating the position correction in Implementation Method 2.

[0032] Symbol Explanation

[0033] 1-X-ray imaging device, 10-Imaging unit, 20-Processor, 21-Control unit, 22-Calculation unit, 30-Display device, 40-Endoscope, 41-Guide wire (equipment), 50-Examinee, 211-Imaging control unit, 213-Display control unit, 221-Motion classification unit, 222-Feature extraction unit, 223-Image selection unit, 224-Position correction unit, 225-Equipment position calculation unit, 226-Parameter calculation unit, 227-Three-dimensional position calculation unit. Detailed Implementation

[0034] Hereinafter, embodiments of the X-ray imaging apparatus of the present invention will be described.

[0035] like Figure 1 As shown, the X-ray imaging apparatus 1 of this embodiment includes: an imaging unit 10, which includes an X-ray source 11 and an X-ray detector 12; a processor 20, which functions as a control unit 21 for controlling the entire apparatus including the imaging unit 10 and an arithmetic unit 22 for processing image data generated using X-rays detected by the X-ray detector 12; and a display device 30 for displaying X-ray images, etc. Furthermore, although not shown, it may also include an input device for the user to input instructions or data required by the control unit 21 or the arithmetic unit 22, and a storage device for storing data required for processing or pre-acquired three-dimensional images of the subject 50, etc.

[0036] As the X-ray source 11, an X-ray tube is typically used, which is connected to a high-voltage generating device (not shown). Furthermore, the X-ray detector 12 is not limited in scope; for example, an FPD (flat panel detector) can be used.

[0037] The imaging unit 10 also includes: a drive unit 13 for driving the X-ray source 11; and a data collection unit 14 for inputting an electrical signal equivalent to the transmitted X-rays output from the X-ray detector 12, and collecting data as two-dimensional image data at each imaging time. The drive unit 13 drives the mechanism supporting the X-ray source 11 and the X-ray detector 12 (e.g., Figure 2 The support mechanism 15) is composed of a motor or other drive source, or a power supply unit for driving the X-ray source 11. The image data collected by the data collection unit 14 is displayed as an X-ray image on the display device 30, and is used for position detection and other processing in the calculation unit 22 as needed.

[0038] In the X-ray imaging apparatus 1, different types of devices exist depending on the support structure of the X-ray source 11 and the X-ray detector 12, or the position of the X-ray source 11, etc. However, this embodiment can be applied to any type as long as it has a structure suitable for interventional surgery and can change the position of the X-ray source 11 relative to the subject (the irradiation angle of the X-ray). For example, it can be applied to such... Figure 2 The X-ray imaging device 1A shown is called a sheath tube type fluoroscopy device, such as Figure 3 The C-arm X-ray imaging device 1B shown is shown.

[0039] exist Figure 2 In the X-ray imaging apparatus 1A shown, an X-ray source 11 is disposed above a bed 16 on which the subject lies, and a detector panel constituting an X-ray detector 12 is disposed on the inner side of the bed 16. In this X-ray imaging apparatus 1A, the X-ray source 11 is fixed to a support platform 17 via a support mechanism 15, which includes a support column 151 supporting the X-ray source 11 and a support arm 152 that rotatably supports the support column 151 relative to the support platform 17. The bed 16, which houses the X-ray detector 12, is supported by the support arm 152, allowing it to move horizontally or vertically.

[0040] In this X-ray imaging device 1A, by rotating the support column 151 relative to the support table 17, the position of the X-ray source 11 can be changed from such a position as... Figure 2 The vertical position shown in (A) is changed to, as shown in, Figure 2 The position shown in (B) allows for changing the angle of X-ray exposure to the subject lying on the bed 16. Furthermore, although not shown, it is sometimes also equipped to allow the support column 151 to move along with... Figure 2 The mechanism moves the X-ray source 11 (X-ray tube) orthogonally to the plane of the paper or rotates the X-ray source 11 fixed to the support column 151. In this case, the X-ray irradiation angle can be varied not only in two dimensions but also in three dimensions. In this specification, the phrase "different irradiation angles" refers to different irradiation angles in two dimensions and three dimensions.

[0041] in addition, Figure 2 The diagram shows a tube-type fluoroscopy device that irradiates X-rays from the upper side of the subject, but the same applies to a lower tube-type fluoroscopy device that places the X-ray source on the lower side of the bed.

[0042] Figure 3 An X-ray imaging device 1B is a structure in which an X-ray source 11 and an X-ray detector 12 are supported by a C-arm 18. A bed 16 for the subject to lie on is arranged in the space between the X-ray source 11 and the X-ray detector 12. The C-arm 18 is fixed to a support platform 17 via a support arm 19, and the position of the C-arm 18 supported by the support arm 19 can be changed, thereby allowing for... Figure 3 As shown in (A), the X-ray source 11 can change from a position directly above the bed 16 to the position shown in (A). Figure 3 The tilted position shown in (B) changes the X-ray irradiation angle. Furthermore, the support arm 19 can rotate about axis P relative to the support platform 17, thereby allowing the X-ray source 11 and the X-ray detector 12 to rotate in a plane orthogonal to the paper to change the X-ray irradiation angle.

[0043] like Figure 4 As shown, the processor 20 includes a control unit 21 and a processing unit 22. The control unit 21 includes an image control unit 211 that controls the operation of the camera unit 10 to control the movement of the X-ray source 11 based on the drive unit 13 or the X-ray irradiation from the X-ray source 11, and a display control unit 213 that controls the display of the display device 30. For example, the image control unit 211 controls the camera unit 10 to collect multiple X-ray images with different imaging times and positions in order to detect the position of the device inserted into the subject during X-ray imaging.

[0044] The computing unit 22 includes: a motion classification unit 221, which analyzes image data (i.e., multiple X-ray images) collected by the data collection unit 14 within a specified time and classifies the types of motion of the subject; and a device position calculation unit 225, which calculates the device position based on the motion classification by the motion classification unit 221. Figure 4 In the illustrated embodiment, the motion classification unit 221 extracts feature points contained in the X-ray images (feature extraction unit 222) to detect motion from the X-ray images, and classifies the motion based on the movement state of the feature points in multiple X-ray images taken from different positions. The device position calculation unit 225 selects multiple combinations from the multiple X-ray images, calculates parameters (parameter calculation unit 226) for each combination that serve as an indicator of the degree of influence of the motion, determines the combination for calculating the device position based on the calculated parameters, and calculates the three-dimensional position of the device using the determined combination (3D position calculation unit 227).

[0045] In addition, Figure 1In this specification, processor 20 is represented by a single box. However, the processor may include, for example, a CPU or GPU, memory, and various computer and ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), programmable IC, and other hardware whose functions are implemented through software. The functions of each part included in the processor can be implemented by one or more processors. For example, control unit 21 and arithmetic unit 22 can implement part or all of the functions of their respective sub-units individually or in combination through the aforementioned software or hardware.

[0046] The X-ray imaging apparatus of this embodiment is characterized by using the X-ray imaging apparatus as an interventional radiography mechanism to detect the position of a device inserted into the object being examined by a processor 20. The device position detection is based on a technique that uses multiple X-ray images acquired by the imaging unit 10 at different shooting positions to detect the three-dimensional position of the device. Then, the body movements of the subject occurring during the acquisition of multiple X-ray images are analyzed, the body movements are classified, and based on the type of body movement, a combination of images from the multiple X-ray images used to calculate the three-dimensional position is determined. The combination with the least influence from the body movements is selected from the combination of multiple images to calculate the three-dimensional position. The specific methods for classifying body movements and calculating the three-dimensional position are described in detail in the following embodiments.

[0047] According to the X-ray imaging apparatus of this embodiment, before calculating the device position, body motion is classified, and in particular, the range of the image used for device position calculation is determined based on whether the body motion is periodic or non-periodic. In this way, in the presence of body motion, especially non-periodic motion, the accuracy of three-dimensional position calculation is prevented from decreasing, thereby enabling high-precision position detection.

[0048] <Implementation Method 1>

[0049] In this embodiment, the three-dimensional position of the device is detected using X-ray images acquired by the camera unit 10 at multiple irradiation angles within a specified angular range, which are used as multiple X-ray images.

[0050] Furthermore, in this embodiment, in order to classify the movement of the subject during the acquisition of X-ray images, the calculation unit 22 extracts feature points of the device or the subject from multiple X-ray images with different irradiation angles, and determines whether the movement of the subject near the device is periodic or non-periodic based on the change in the position of these feature points. Based on this determination result, multiple X-ray images (image set) for calculating the three-dimensional position are determined. Figure 4As shown, the motion classification unit 221 may include an image selection unit 223 as a functional unit for selecting image groups. When the image selection unit 223 divides multiple images into one or more image groups according to the type of motion, it uses a predetermined reference for subsequent device position calculation processing, that is, parameter calculation for calculating the three-dimensional position.

[0051] The following is for reference. Figure 5 The flowchart shown explains the operation of the X-ray imaging device of this embodiment, mainly the operation of the processor.

[0052] <Camera recording steps: S11>

[0053] The imaging unit 10 begins to capture images while rotating the X-ray source 11 and X-ray detector 12 within a preset angle range, acquiring X-ray images at multiple irradiation angles. The specified angle is not particularly limited as long as it is within the movable range of the X-ray imaging device. For example, when the initial position of the X-ray source 11 and X-ray detector 12 is set to zero degrees, it can be ±10 degrees (angle range of 20 degrees). Figure 6 The diagram shows an example of acquiring X-ray images within a 20-degree angular range. Furthermore, imaging can be performed once at each of the multiple irradiation angles within the set angular range, or it can be performed repeatedly at the specified irradiation angles, acquiring multiple X-ray images for each irradiation angle. In the case of acquiring multiple X-ray images for each irradiation angle, imaging can be performed repeatedly within the specified angular range, or multiple imaging sessions can be conducted at each irradiation angle. Moreover, the imaging method can be progressive; in the case of the X-ray source 11 or a C-arm X-ray imaging device, continuous imaging can be performed while continuously rotating the X-ray source 11 and the X-ray detector 12. In the latter case, imaging within the specified angular range is repeated to acquire multiple X-ray images at the same irradiation angle.

[0054] The object of the camera is the area including the examination site of the subject. In this embodiment, the object is the camera when an interventional procedure is performed with a device such as a catheter equipped with a guide wire inserted toward the examination site. The examination site and part of the moving device are reflected in the X-ray image.

[0055] <Steps for classifying physical movements: S12>

[0056] The calculation unit 22 uses the multiple X-ray images obtained through the above-described imaging to determine whether the subject has movement and to classify the type of movement. Therefore, the feature extraction unit 222 first extracts feature points of a specified part of the device or the subject from each X-ray image. The feature points are feature points of the shape of tissue or object that can be detected in the X-ray image. There are no particular limitations as long as they are parts that clearly show a change in brightness on the X-ray image. They can be feature points of the tissue of the subject or feature points of the device. However, in order to determine the movement related to the device, it is preferable to track the feature points of the device.

[0057] An example of a feature point when the device is an endoscope 40 equipped with a guidewire 41 is shown below. Figure 7 .like Figure 7 As shown, feature points can be detected at the end 45a of the guidewire 41 on the endoscope 40 side, the end 45b in the direction of movement, the boundary point 45c between the permeable and non-permeable parts of the guidewire 41, and the mark 45d (a mark made of a material that does not transmit X-rays) provided on the catheter. The feature extraction unit 222 extracts these feature points of brightness variation using general image processing techniques and determines the position coordinates of the feature points in the image. The feature points are used for the analysis of body motion and the calculation of the three-dimensional position of the device, which will be described later. The number of feature points extracted can be one or more, but when calculating the three-dimensional position of the device, by using the positions of multiple feature points, information about the position of the device, which has a length or size, can be obtained.

[0058] The motion classification unit 221 calculates the changes in the position of feature points based on the coordinates of feature points in each X-ray image and classifies the motion of the subject. Specifically, the changes in the position of feature points are calculated by measuring the distance or vector of movement between adjacent images, the trajectory (movement vector) of feature points from the first image to the last image across multiple images, the average of the movement vectors, and the sum of the movement vectors. Based on the calculated changes in the position of feature points, the motion is classified as, for example, periodic motion or non-periodic motion. As a basis for classification, a combination of movement vectors, the average of movement vectors, and the sum of movement vectors can be used, or only one of them can be used. In either case, a predetermined threshold is set, and periodic motion and non-periodic motion are determined and classified based on whether the displacement of the feature points over time is within or exceeds the threshold.

[0059] In addition, the classification can be divided not only into periodic motion and non-periodic motion, but also into non-body motion, periodic motion (motion within a specified range), non-periodic motion 1 (motion with large positional changes exceeding the specified range, but returning to the original position), and non-periodic motion 2 (motion with large positional changes and not returning to the original position), etc.

[0060] Figure 8 An example of classifying body movement into periodic movement and aperiodic movement is shown. This example is an example of tracking the end 45b of the guide wire 41 as a feature point, showing the state where the feature point moves from the number 1 surrounded by a circle to the number 4 surrounded by a circle, and classifying periodic movement and aperiodic movement based on the movement vector of the feature point or its average. In the case of classifying based on the movement vector, for example, when the average of the movement vectors falls within the range (prescribed threshold range) 800 of the periodic movement represented by the dashed line, it is determined as periodic movement, and when it exceeds the range 800 and is outside, it is determined as aperiodic movement.

[0061] In addition, regarding obtaining the period of the vector (in Figure 8 it is obtaining the period of the vectors of 4 points), for example, the shortest is set to the projection image acquisition interval, and based on this, it is determined that the period of the body movement depends on the type of body movement. For example, in the case of body movement with a short period such as pulsation, it can be set to 1 second / time, and in the case of respiratory movement, it can be set to 3 - 5 seconds / time.

[0062] Also, regarding the range 800 of the periodic movement, if it is respiratory movement or pulsation, the range (displacement amount) of the movement tendency of the surrounding tissues accompanying these is known. For example, if it is pulsation, it is about 10 mm, and if it is respiratory movement, it is about 20 mm, so it can be set according to this displacement amount. The average of the movement vectors of the feature points converges approximately to zero over time in the case of periodic movement, but does not converge to zero and becomes a larger value in the case of aperiodic movement. Therefore, when the average or sum of the movement vectors is close to zero, it is determined as periodic movement, and when it exceeds the threshold (TH), it is determined as aperiodic movement.

[0063] <Determination of X-ray image group: S13>

[0064] The body movement classification unit 221 (image selection unit 223) determines an image group for three-dimensional position detection based on the classification result (type of body movement) of the body movement that occurs during the acquisition of a plurality of images within a prescribed angular range. The types of body movement that may occur during the acquisition of a plurality of images are diverse. For example, as Figure 9 shown, there may be the following situations: when all X-ray images are acquired in a state of no body movement or body movement classified as periodic movement (case 1), when at the beginning of shooting, it is in a state of no body movement or body movement classified as periodic movement, but non-periodic movement occurs at a certain point, and then returns to periodic movement at the displaced position (case 2), when non-periodic movement continues for a certain period of time after periodic movement (case 3), etc. In addition, Figure 9 the vertical axis of represents the magnitude of the average or sum of the movement vectors, but it can also represent the displacement amount of the body movement. "TH" is the threshold.

[0065] The image selection unit 223 determines the image group for calculating the three-dimensional position based on the classification of body motion, the classification of X-ray images based on this, and the type corresponding to the occurrence of body motion. As a criterion for determining the image group, the number of images belonging to the image group, the priority of the image group, etc., can be used. When multiple criterions exist, the priority of the applicable criterion can be preset.

[0066] Figure 10 and Figure 11 Examples of images obtained with different types of body movement are shown in the image. Figure 10 As in Example 1 above, there is no body movement within the specified angular range, or the displacement range of the equipment is a finite periodic motion. In this case, all X-ray images obtained within the specified angular range are used for equipment position calculation.

[0067] Figure 11 Example 2 above illustrates this: Within the X-ray irradiation angle range (Θmin~Θmax), the body motion is periodic up to the irradiation angle Θk. Conversely, within a specified range between or between the irradiation angle Θk and Θk+1, body motion classified as non-periodic occurs, and the device position returns to periodic motion from its initial position displacement. Here, based on the classification of body motion, multiple images are divided into an image group for the irradiation angle (Θmin~Θk-1), an image group for the irradiation angle (Θk~Θk+1) acquired during non-periodic motion, and a subsequent image group (Θk+2~Θmax). In this case, for example, in Example 2 above, if the acquired X-ray images include a first image group and a second image group, the image group with the larger number of images is used for three-dimensional position calculation. Alternatively, if the number of images belonging to the first image group is more than a specified number, the first image group is determined; if it is less than the specified number, it is designated as the second image group. Furthermore, the image group with the larger angular widths of Θmin~Θk-1 and Θk+2~Θmax can be used as the image group for calculating the three-dimensional position.

[0068] Although not illustrated, but in such Figure 9 In the case shown in Example 3, an image set acquired during periodic motion is selected. Furthermore, if the image set acquired during periodic motion contains a small number of images, making it impossible to obtain images sufficient to ensure the accuracy of 3D position detection, the acquired image data can be discarded, and imaging can be performed again within a specified angle range. That is, the classification result is transmitted from the motion classification unit 221 to the control unit 21, and the camera control unit 211 controls the camera unit 10 to re-encode the image.

[0069] <<Equipment Location Detection>>

[0070] <Parameter Calculation: S14>

[0071] The parameter calculation unit 226 uses multiple X-ray images belonging to the defined image group to calculate parameters that represent the influence of body motion in multiple combinations of X-ray images taken from different positions. The combination of X-ray images is not limited; for example, ... Figure 12 As shown, when multiple (N) X-ray images are obtained from multiple (M) shooting positions (angle range (Θj1~ΘjM)), the X-ray images of each irradiation angle 1~N are cyclically combined with X-ray images of different irradiation angles and set as an M×N combination.

[0072] As a parameter, the distance between two lines (the distance between two lines) can be used, determined by the position of the X-ray source 11 when acquiring each X-ray image and the position of the feature point on the image. In the two X-ray images being compared, if there is no body movement and the position of the feature point does not change, these two lines intersect, and the feature point is determined as a coordinate. However, if the feature point is misaligned due to body movement, the two lines do not intersect, and their distance changes according to the magnitude of the misalignment. That is, the magnitude of the effect of body movement is reflected in the distance between the two lines.

[0073] In addition to the distance between two lines, the perimeter or area of ​​a polygon generated by connecting the midpoints of line segments representing the distance between two lines using three or more X-ray images as disclosed in Patent Document 2 can also be used as a parameter. For simplicity, the calculation of the distance between two lines will be explained below.

[0074] The parameter calculation unit 226 calculates the distance between two straight lines as follows. For example... Figure 13 As shown, the position of the X-ray source 11 in the first imaging position is designated as S1, the position in the second imaging position is designated as S2, and the positions of the devices on the X-ray detector 12 in the first and second imaging positions are designated as P1 and P2, respectively. The positions P1 and P2 of the devices in the X-ray detector 12 can be calculated based on the geometric configuration of the X-ray source 11 and the X-ray detector 12, and the positions of the devices in the X-ray images I1 and I2 acquired at each position. Here, if vector v1 represents the straight line connecting S1 and P1, and vector v2 represents the straight line connecting S2 and P2, the line segment Q1-Q2 (vector u) with the shortest distance between these two straight lines can be obtained by the following formula.

[0075] [Formula 1]

[0076] Q1=P1+(D1-D2*Dv) / (1-Dv*Dv)*v1

[0077] Q2=P2+(D2-D1*DV) / (Dv*Dv-1)*v2

[0078] Where, D1=(P2-P1)·v1

[0079] D2=(P2-P1)·v2

[0080] Dv = v1·v2

[0081] ("*" represents the vector dot product, and "·" represents the scalar product or the product of a scalar and a vector)

[0082] The parameter calculation unit 226 calculates the length D (distance between Q1 and Q2) of the line segment, which is the distance between two straight lines, for a combination of all X-ray images belonging to the image group selected by the image selection unit 223.

[0083] <Optimal Combination Selection and 3D Position Calculation: S15>

[0084] After the parameter calculation unit 226 calculates the parameters for all combinations, the three-dimensional position calculation unit 227 uses the combination in which the parameter is minimized to calculate the three-dimensional position of the feature points of the device. As described above, the combination in which the parameter (here, the distance between two straight lines) is minimized is the combination of X-ray images that minimizes the influence of body motion and the displacement difference. Therefore, by using such a combination, the device position can be calculated with high precision. Regarding the three-dimensional position of the device, when the parameter is the distance between two straight lines, it can be calculated as the midpoint of the line segment that determines it. That is, the three-dimensional position calculation unit 227 uses specific values ​​Q1 and Q2 of the parameter (reference...) Figure 13 And Equation 1) and calculate the device position (coordinates of feature points) using the following formula.

[0085] [Formula 2]

[0086] Q = (Q1 + Q2) / 2

[0087] When the parameters are calculated based on a graphic obtained using three or more X-ray images, the centroid or center of the graphic can be used as the feature point location (device location) for calculation. Furthermore, when multiple feature points are extracted, the location of each feature point is calculated.

[0088] The device position calculated by the three-dimensional position calculation unit 227 is transmitted to the display control unit 213, and mapped onto a pre-acquired three-dimensional image of the subject and displayed on the display device 30.

[0089] During the interventional procedure, whenever the device position changes or the above steps of calculating the device position from the camera within a specified angle range (S11 to S15) are repeated at a specified cycle, the mapping result is updated and displayed on the display device 30 each time.

[0090] According to this embodiment, body movements are classified based on the trajectory on the X-ray image of the device (feature point), and the X-ray image used for three-dimensional position detection processing, including subsequent parameter calculation and device position calculation, is selected according to the type of body movement. This enables high-precision three-dimensional position detection and improves the effectiveness of the X-ray imaging device as an interventional imaging mechanism. In particular, it avoids the influence of non-periodic body movements that occur when acquiring multiple X-ray images at different shooting positions, i.e., at different times, for position detection, thereby improving the accuracy of position detection.

[0091] Furthermore, according to this embodiment, when the three-dimensional position is determined by calculating parameters based on a combination of multiple X-ray images, image data with non-periodic body movement can be removed from the calculation, thereby reducing the load on the computation unit based on parameter calculation.

[0092] Furthermore, in the above description, the case in which the classification of body movements and the selection of image groups based on their types are automatically performed in the calculation unit 22 has been described. However, it is also possible to prompt the user about the intermediate process or to intervene in the user's judgment or selection. Such variations are also included in the present invention.

[0093] <Implementation Method 2>

[0094] This embodiment is an implementation method corresponding to the situation where the position of an object on an image changes according to the illumination angle. Its feature is that it has the function of responding to changes in the position of feature points in motion classification.

[0095] In this embodiment, the process of acquiring multiple X-ray images by taking pictures within a specified irradiation angle range of the X-ray source, classifying the body movements that occur during the acquisition of these multiple X-ray images, and using a combination of X-ray images with different irradiation angles from the multiple X-ray images to calculate parameters and the three-dimensional position of the device is the same as in Embodiment 1.

[0096] Hereinafter, this embodiment will be described focusing on the differences from Embodiment 1. In the following description, the same content as Embodiment 1 refers to the drawings used in the description of Embodiment 1, and repeated descriptions are omitted.

[0097] The function of the arithmetic unit 22 in this embodiment is shown below. Figure 14 The processing flow of the arithmetic unit 22 is shown below. Figure 15 .like Figure 14 As shown, the motion classification unit 221 of this embodiment, in addition to the feature extraction unit 222 and image selection unit 223 provided in Embodiment 1, also includes a position correction unit 224. Figure 15As shown in S11-2, the position correction unit 224 corrects the coordinates (positions) of the feature points extracted by the feature extraction unit 222 from each X-ray image.

[0098] To illustrate the function of the position correction unit 224, refer to... Figure 16 This describes the positional changes of points of interest (e.g., feature points) on the image based on the illumination angle.

[0099] In an X-ray imaging device where the X-ray detector 12 is fixed to a bed containing the subject, such as... Figure 16 As shown, regarding the object located between the X-ray source 11 and the X-ray detector 12 and projected onto the X-ray image (in... Figure 16 In the image, the position of a point (represented as the point of interest) differs when the X-ray source 11 is at an illumination angle ang1 and when it moves an angle Θ from the source to an illumination angle ang2, as shown on the left side of the image. That is, even if the point of interest has no movement, by changing the illumination angle, it appears to move on the image. Furthermore, the illumination angle of the X-ray source 11 typically changes within a plane intersecting the X-ray detector 12, thus the position of the point of interest varies in one direction of the X-ray image (in...). Figure 16 (The middle part moves vertically)

[0100] Here, if the position of the point of interest at the illumination angle ang1 is set as P1, and the position of the point of interest at the illumination angle ang2 is set as P2, then the amount of movement of the point of interest (P2-P1) based on the illumination angle can be expressed by the following formula.

[0101] [Formula 3]

[0102] P2-P1=h*L*sinΘ / (L*cosΘ-h)=ΔP(Θ) (3)

[0103] In the formula, L is the distance from X-ray source 11 to X-ray detector 12, and h is the distance from X-ray detector 12 (e.g., the upper surface of a flat panel detector) to the point of interest.

[0104] For example, since the distance from the bed surface to the X-ray detector 12 is known, and the distance from the bed surface to the specified organ of the subject to which the device is inserted is a known statistical value, these values ​​can be used to calculate the distance h from the X-ray detector 12 to the point of interest. Thus, the displacement at each irradiation angle, i.e., the displacement correction ΔP(Θ), can be calculated according to equation (3).

[0105] The position correction unit 224 uses the correction amount ΔP(Θ) to correct the coordinates P' of the feature points actually extracted by the feature extraction unit 222 at each illumination angle, and uses it as the position P of the feature point at each illumination angle (P = P' + ΔP or P = P' - ΔP. The sign of ΔP depends on the sign of Θ relative to the illumination angle that serves as the reference).

[0106] The subsequent processing is the same as in Implementation Method 1. The motion classification unit 221 uses the positions of the feature points corrected by the position correction unit 224 to calculate the movement vectors of the feature points within a specified angle range, classifies the motion (S12), and selects multiple X-ray images (image sets) for device position calculation based on the classification. The device position calculation unit 225 uses the selected image set to calculate parameters based on the combination of various X-ray images, and calculates the three-dimensional position of the device based on the combination of images with parameters that have the least influence on motion (S13-S15).

[0107] According to this embodiment, in addition to the same effects as in Embodiment 1, for X-ray imaging devices where the irradiation angle of the X-ray detector changes, the positional changes of feature points in images with different irradiation angles are corrected, thereby enabling high-precision body motion classification. Thus, not only periodic body motion, but also non-periodic body motion can be detected, and the three-dimensional position of the device, unaffected by such motion, can be detected.

[0108] Furthermore, according to this embodiment, images from multiple directions can be acquired while continuously changing angles to align the position. Therefore, considering body movement, three-dimensional position can be acquired as quickly and accurately as possible. That is, when taking pictures at fixed angles to acquire periodic amounts of data, if there is non-periodic body movement during the movement between angles, the accuracy of position detection will decrease. However, according to this embodiment, since images are acquired continuously, it is possible to determine if there is non-periodic body movement during that period, thereby improving the temporal resolution of judgment and position detection, and shortening the acquisition time.

[0109] The embodiments of the present invention have been described above. However, embodiments in which known structures or functions are added or in which structures or functions that can be omitted in the present invention are also included in the present invention.

Claims

1. An X-ray imaging device, characterized in that, have: The imaging unit includes an X-ray source that irradiates X-rays and an X-ray detector that is positioned opposite to the X-ray source and separated from the object to be examined, and generates an X-ray image of the object to be examined from the X-rays that are transmitted through the object to be examined and detected by the X-ray detector; and The processor analyzes multiple X-ray images taken at different X-ray irradiation angles targeting the object being inspected, and calculates the three-dimensional position of the device inserted into or mounted on the object being inspected. The processor performs the following processing: classifies the movement of the object under inspection based on multiple X-ray images taken from different positions, and selects a combination of two or more X-ray images with different irradiation angles from the multiple X-ray images according to the type of body movement classified, and uses the selected combination to calculate the three-dimensional position of the device.

2. The X-ray imaging device according to claim 1, characterized in that, The processor performs the following processing: extracting feature points from at least one of the inspected object and the device in the plurality of X-ray images, and classifying body movement based on the trajectory of the extracted feature points in the plurality of X-ray images.

3. The X-ray imaging device according to claim 1, characterized in that, The processor performs the following processing: extracting feature points of at least one of the inspected object and the device from the plurality of X-ray images, and classifying body motion based on the movement vectors of the feature points in the plurality of images.

4. The X-ray imaging device according to claim 3, characterized in that, The processor performs the following processing: when the movement vector or its average is within a preset threshold, the movement of the object being inspected is determined to be a periodic movement; when it exceeds the preset threshold, the movement of the object being inspected is determined to be a non-periodic movement.

5. The X-ray imaging device according to claim 4, characterized in that, The processor performs the following processing: in the case that the plurality of X-ray images include X-ray images acquired when the movement of the object under inspection is non-periodic, the processor selects a group of images from the plurality of X-ray images that excludes X-ray images acquired when there is non-periodic movement, and uses the selected group of images to calculate the three-dimensional position of the device.

6. The X-ray imaging device according to claim 4, characterized in that, The processor performs the following processing: in the case that the multiple X-ray images include multiple image groups acquired before and after a non-periodic motion or when there is a periodic motion, the processor selects the image group containing more images and uses the selected image group to calculate the three-dimensional position of the device.

7. The X-ray imaging device according to claim 1, characterized in that, The processor performs the following processing: for multiple combinations consisting of two or more X-ray images contained in the plurality of X-ray images, it calculates parameters that serve as indicators of body motion influence; and selects the combination of X-ray images with the least body motion influence based on the parameters, and calculates the three-dimensional position of the device.

8. The X-ray imaging device according to claim 1, characterized in that, The processor performs the following processing: For each of the plurality of X-ray images, a straight line connecting the X-ray source to a feature point in the X-ray image is calculated, and the distance between two straight lines is calculated from the plurality of straight lines calculated for each X-ray image; and The three-dimensional position of the device is calculated by using the combination of X-ray images with different irradiation angles to find the combination of the two straight lines with the shortest distance.

9. The X-ray imaging apparatus according to claim 2, wherein the X-ray irradiation angle is changed by moving the position of the X-ray source relative to the object being examined and the X-ray detector, characterized in that... The processor includes a position correction unit that corrects the position of the feature point according to the irradiation angle of the X-ray source, and classifies body motion based on the trajectory of the feature point after the position is corrected.

10. A device position detection method, comprising detecting the three-dimensional position of a device reflected in the X-ray images by taking multiple X-ray images at different X-ray irradiation angles, the device position detection method being characterized by performing the following processing: Feature points are extracted from each of the plurality of X-ray images, and the movement vector of the feature points between the images is calculated; Based on the movement vector, the movement of the camera object during the acquisition of the plurality of X-ray images is classified; Based on the classified movement, select from the plurality of X-ray images a group of images acquired when no non-periodic movement occurs; and The three-dimensional position of the device is calculated using the selected set of images.

Images