Image constituting system and image constituting method

Abstract

To provide a highly versatile system for constituting an accurate cross-sectional image.SOLUTION: An image constituting system includes: a radiation source for emitting a radiation ray to an imaging object from different angles by rotating around the imaging object; a detector for detecting the distribution of the radiation ray transmitted through the imaging object as a detection image; and a control device for reconstituting a cross-sectional image of the imaging object using the detection image. The control device acquires a plurality of detection images having different angles and radiation intensities by switching the radiation intensity while rotating the radiation source, extracts an effective region for each of the plurality of detection images, generates a complementary detection image by complementing a region that is not the effective region using an effective region of another detection image for each of the plurality of detection images, and reconstitutes the cross-sectional image from the plurality of complementary detection images.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image construction system and an image construction method. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 2016-000118 (Patent Document 1) describes a conventional technology for measuring the internal condition of a treatment target. This publication states that "a beam irradiation target confirmation device 1 includes an X-ray switching irradiation processing unit 6a that irradiates at least two types of X-rays from a vertical X-ray irradiator 13 using an energy switching unit 11, a vertical X-ray detection unit 14 that detects the X-rays irradiated from the vertical X-ray irradiator 13, a pretreatment confirmation image creation processing unit 7 that creates pretreatment confirmation images 20B and 20C based on detection information of the at least two types of X-rays acquired by the vertical X-ray detection unit 14, a reference image acquisition unit 3 that acquires a reference image 20A obtained in the treatment planning stage, a comparison processing unit 8a that compares the pretreatment confirmation images 20B and 20C with the reference image 20A, and a result output unit 4 that outputs the comparison result acquired by the comparison processing unit 8a." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-000118 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses that a two-dimensional image of the stopping power ratio is calculated from X-ray images obtained using two X-ray energies. In CBCT (Cone Beam Computed Tomography), the irradiated X-ray dose must be increased to image the thick central region of the subject with a good signal-to-noise ratio (SN). However, if the irradiated X-ray dose is high, the amount of X-rays that penetrates the thin peripheral regions of the subject will be high, causing the detector pixels to saturate and preventing accurate measurements from being obtained. This makes it difficult to image both the central and peripheral regions well, which can cause errors in the reconstructed cross-sectional images. In CBCT, a conventional technique for capturing good images of the central and peripheral areas involves placing a metal object called a Bowtie filter between the X-ray source and the subject. Bowtie filters are thin in the central region and become thicker towards the periphery. As a result, the irradiated X-rays generated from the X-ray source are transmitted more in the central region of the filter, making them stronger toward the central part of the subject. On the other hand, the amount transmitted in the peripheral region of the filter is reduced, making them weaker toward the peripheral part of the subject. This makes it possible to improve the signal-to-noise ratio in the central part of the subject while suppressing saturation in the peripheral region. However, because the characteristics of the Bowtie filter are determined by its shape, they cannot be flexibly changed, limiting its applications. Therefore, an object of the present invention is to realize a highly versatile system for constructing highly accurate cross-sectional images. [Means for solving the problem]

[0005] In order to achieve the above object, one representative image construction system of the present invention includes a radiation source that rotates around an object to be imaged and irradiates the object with radiation from different angles, a detector that detects the distribution of radiation that has passed through the object to be imaged as detected images, and a control device that reconstructs a cross-sectional image of the object to be imaged using the detected images, wherein the control device obtains a plurality of detected images with different angles and radiation intensities by switching the radiation intensities while rotating the radiation source, extracts an effective area for each of the plurality of detected images, complements an area that is not an effective area for each of the plurality of detected images using the effective areas of other detected images to generate a complementary detected image, and reconstructs the cross-sectional image from the plurality of complementary detected images. Furthermore, one representative image construction method of the present invention is an image construction method using an image construction system including: a radiation source that rotates around an object to be imaged and irradiates the object with radiation from different angles; a detector that detects the intensity distribution of the radiation that has passed through the object to be imaged as a detected image; and a control device that reconstructs a cross-sectional image of the object to be imaged using the detected images, wherein the control device includes the steps of: acquiring a plurality of detected images with different angles and radiation intensities by switching the radiation intensities while rotating the radiation source; extracting an effective area for each of the plurality of detected images; complementing an area that is not an effective area for each of the plurality of detected images with the effective areas of other detected images to generate a complementary detected image; and reconstructing the cross-sectional image from the plurality of complementary detected images. [Effects of the Invention]

[0006] According to the present invention, a highly versatile system for constructing highly accurate cross-sectional images can be realized. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is an explanatory diagram of the operation of the image composition system according to the first embodiment. [Figure 2] FIG. 1 is a diagram illustrating the configuration of an image composition system. [Figure 3] An explanatory diagram of switching the X-ray intensity. [Figure 4] 10 is a flowchart showing a processing procedure of the image construction system. [Figure 5] 10 is a flowchart showing details of a complementation process. [Figure 6] A variation of the strength change. [Figure 7] Four intensity switching variants. [Figure 8] Block diagram of a radiation therapy system. [Figure 9] FIG. 1 is a perspective view of a radiation therapy device. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment will be described with reference to the drawings. [Example]

[0009] FIG. 1 is an explanatory diagram of the operation of the image composition system according to the first embodiment. In the image construction system of the first embodiment, a radiation source R1 and a detector D1 are provided in a gantry 11, which is an annular frame. A person to be imaged is placed inside the gantry 11 while lying on a bed.

[0010] The radiation source R1 emits a cone beam of X-rays toward the imaging target. The detector D1 faces the radiation source R1 across the imaging target and detects the distribution of radiation that has passed through the imaging target as a detected image. The radiation source R1 and the detector D1 rotate simultaneously in the same direction by driving the gantry 11. This allows radiation to be irradiated onto the imaging subject from different angles, and detection images at those angles can be obtained.

[0011] The control device 20, which will be described later, switches the X-ray intensity while rotating the radiation source R1. In FIG. 1, for convenience, the rotation angle when the radiation source R1 irradiates X-rays from directly above the subject is set to "0.0 degrees," and X-rays are irradiated in increments of 0.5 degrees. The X-ray intensity is repeatedly switched between "strong" and "weak." Therefore, the X-ray intensity at "0.0 degrees" is "strong," the X-ray intensity at "0.5 degrees" is "weak," the X-ray intensity at "1.0 degrees" is "strong," the X-ray intensity at "1.5 degrees" is "weak," the X-ray intensity at "2.0 degrees" is "strong," and the X-ray intensity at "2.5 degrees" is "weak."

[0012] The control device 20 obtains the detection results of the detector D1 at each angle, that is, the detected images at each angle. The control device 20 extracts an effective area for each detection image. Specifically, the control device 20 excludes saturated regions where pixel values ​​are saturated from the effective area for detection images acquired at angles where X-ray intensity is "strong," and excludes low SN regions where pixel values ​​are below a predetermined value from the effective area for detection images acquired at angles where X-ray intensity is "weak." For example, a saturation threshold for identifying saturated regions and a low SN threshold for identifying low SN regions may be prepared, and regions where pixel values ​​are below the saturation threshold may be defined as effective regions for detection images acquired at angles where X-ray intensity is "strong," and regions where pixel values ​​are above the low SN threshold may be defined as effective regions for detection images acquired at angles where X-ray intensity is "weak." Alternatively, regions where pixel values ​​are above the low SN threshold and below the saturation threshold may be defined as effective regions for detection images at all angles, regardless of X-ray intensity.

[0013] The control device 20 generates a complementary detected image by complementing an ineffective area (hereinafter referred to as a defective area) of each of the plurality of detected images using the effective areas of the other detected images, thereby obtaining a complementary detected image without a defective area for each angle. The control device 20 reconstructs a cross-sectional image of the imaging target using a plurality of complementary detected images. In this way, by reconstructing a cross-sectional image after complementing the defective region, a highly versatile system that can generate highly accurate cross-sectional images can be obtained.

[0014] FIG. 2 is a diagram showing the configuration of the image composition system. The image processing system is equipped with radiation sources R1 and R2 mounted on a gantry 11, which is a ring-shaped frame. Radiation source R2 is positioned approximately perpendicular to radiation source R1. In other words, when radiation source R1 irradiates X-rays at "0 degrees," radiation source R2 irradiates X-rays at "90 degrees."

[0015] The image processing system also includes a detector D1 and a detector D2 on the gantry 11. Detector D1 faces radiation source R1, and detector D2 faces radiation source R2.

[0016] The image processing system also includes a control device 20. The control device 20 has a gantry driving unit 21, an X-ray irradiation control unit 22, an image processing unit 23, and a display unit 24.

[0017] The gantry driving unit 21 is a processing unit that controls the driving of the gantry 11. When the gantry 11 is driven, the radiation source R1, the radiation source R2, the detector D1, and the detector D2 rotate simultaneously in the same direction. Therefore, even when the gantry 11 is driven, the relative positional relationship between the radiation source R1, the radiation source R2, the detector D1, and the detector D2 is maintained.

[0018] The X-ray irradiation control unit 22 controls the X-ray irradiation by the radiation source R1 and the radiation source R2. The X-ray irradiation control unit 22 can individually control the X-ray intensity of the radiation source R1 and the X-ray intensity of the radiation source R2. As an example, the X-ray irradiation control unit 22 switches the X-ray intensity by changing the time (pulse width) for irradiating X-rays. Alternatively, the X-ray intensity may be switched by controlling the tube current or tube voltage of the radiation source.

[0019] The image processing unit 23 acquires detected images from the detector D1 and the detector D2. Furthermore, the image processing unit 23 acquires the driving state of the gantry 11 from the gantry driving unit 21. Therefore, the image processing unit 23 can identify the angle at which the acquired detected image is detected. Furthermore, the image processing unit 23 acquires the control state of the X-ray irradiation from the X-ray irradiation control unit 22. Therefore, the image processing unit 23 can identify the X-ray intensity of the acquired detected image.

[0020] The image processing unit 23 extracts a valid area from each of the plurality of detected images, complements pixel values ​​of the defective area using other detected images, and generates a plurality of complementary detected images, and then reconstructs a cross-sectional image of the imaging target from the complementary detected images.

[0021] To reconstruct a cross-sectional image of the subject, all that is required is complementary detected images covering 180 degrees. In the configuration shown in FIG. 2, radiation source R1 and radiation source R2 are arranged at a substantially right angle. Therefore, by rotating the gantry 11 by 90 degrees, complementary detected images covering 180 degrees can be obtained. Alternatively, the gantry 11 may be rotated 180 degrees and a cross-sectional image reconstructed using complementary detected images covering 360 degrees. Reconstructing a cross-sectional image from complementary detected images covering 360 degrees can provide a more accurate cross-sectional image than reconstructing a cross-sectional image from complementary detected images covering 180 degrees.

[0022] The display unit 24 is, for example, a liquid crystal display. The display unit 24 displays the cross-sectional image generated by the image processing unit 23. The display unit 24 can also display a detected image and a complementary detected image. The display unit 24 can also display information related to the control of the gantry 11 and the control of the radiation sources R1 and R2.

[0023] 3 is an explanatory diagram of switching of X-ray intensity. The X-ray irradiation control unit 22 switches the X-ray intensity by changing the time (pulse width) for irradiating X-rays. In Figure 3, when the rotation angle is "0.0 degrees," the irradiation time is long, i.e., the pulse width is wide. As a result, the X-ray intensity is "strong." Also, when the rotation angle is "0.5 degrees," the irradiation time is short, i.e., the pulse width is narrow. As a result, the X-ray intensity is "weak." By switching in the same way, the X-ray intensity at "1.0 degrees" is "strong," at "1.5 degrees" is "weak," at "2.0 degrees" is "strong," at "2.5 degrees" is "weak," and at "3.0 degrees" is "strong."

[0024] FIG. 4 is a flowchart showing the processing procedure of the image construction system. The image construction system sequentially executes the following steps S101 to S107. Step S101 The gantry driving unit 21 controls the driving of the gantry 11. Specifically, the gantry driving unit 21 starts the rotation of the gantry 11, and the process proceeds to step S102. The rotation of the gantry 11 continues at a constant speed until it reaches a predetermined rotation angle. Step S102 The X-ray irradiation control unit 22 starts control of irradiating X-rays while switching the X-ray intensity, and proceeds to step S103. The control of irradiating X-rays while switching the X-ray intensity is performed for both the radiation source R1 and the radiation source R2. The control of irradiating X-rays while switching the X-ray intensity continues until the rotation of the gantry 11 reaches a predetermined rotation angle.

[0025] Step S103 The image processing unit 23 acquires detected images from the detectors D1 and D2, and stores the detected images in association with the angle and the X-ray intensity. The acquisition of detected images continues until the rotation of the gantry 11 reaches a predetermined rotation angle. Then, the process proceeds to step S104. Step S104 The image processing unit 23 sets an angle range. When generating a complementary detection image at a certain angle, the image processing unit 23 uses detection images at other angles. However, the accuracy decreases as the angle of the detection image used for complementation deviates from the angle of the complementary detection image to be generated. Therefore, by setting an angle range centered on the angle of the complementary detection image and using detection images within that range, a highly accurate complementary detection image can be obtained. After setting the angle range, the process proceeds to step S105.

[0026] Step S105 The image processing unit 23 performs a complementation process to generate a complemented detected image using the detected images in the set angle range. The complementation process will be described in detail later. After the complementation process, the process proceeds to step S106.

[0027] Step S106 The image processing unit 23 reconstructs a cross-sectional image of the imaging target using the multiple complementary detected images, and then proceeds to step S107. Step S107 The display unit 24 displays the cross-sectional image of the imaging target, and the process ends.

[0028] FIG. 5 is a flowchart showing the details of the complementation process. FIG. 5 illustrates an example in which a complementary detected image at an angle α is generated. Step S201 The image processing unit 23 reads out the detected images within a predetermined range before and after the angle α. For example, if three images are used before and after the angle α and the detected images are acquired in increments of 0.5 degrees, the angle range is from "α-1.5" degrees to "α+1.5" degrees. In FIG. 5, step S201(n) reads out the detected images at the angle α. Also, with β=0.5, step S201(n-1) reads out the detected images at the angle (α-β). Similarly, step S201(n+1) reads out the detected images at the angle (α+β). After the detected images are read out, the process proceeds to step S202.

[0029] Step S202 The image processing unit 23 extracts a valid area for each detected image using a threshold value. For example, a region where the pixel value is equal to or greater than the low SN threshold and less than the saturation threshold may be extracted as the valid area. Then, the process proceeds to step S203. Step S203 The image processing unit 23 divides the pixel values ​​of the effective area of ​​each detected image by the pulse width. As a result, the detected image is normalized by the radiation intensity. Then, the process proceeds to step S204.

[0030] Step S204 The image processing unit 23 projects the detection image included in a predetermined angle range onto a complementary detection image at angle α. This projection is a process for obtaining a mapping that reflects the difference in angle. Thereafter, the image processing unit 23 performs the processes of steps S205 to S207 for each pixel of the complementary detection image at angle α, thereby generating a complementary detection image.

[0031] Step S205 The image processing unit 23 selects a detection image and determines whether the pixel of the projected detection image is a pixel in the valid area. If it is not a pixel in the valid area, another unselected detection image is selected and step S205 is repeated. If it is a pixel in the valid area, the process proceeds to step S206. If all detection images have been selected, the process proceeds to step S207. Step S206 The image processing unit 23 integrates the pixel values ​​and increments the count. Thereafter, another unselected detected image is selected, and the process proceeds to step S205. If all detected images have been selected, the process proceeds to step S207.

[0032] Step S207 The image processing unit 23 divides the integrated pixel value by the count number to obtain the pixel value of the complemented detected image. The integrated pixel value is the sum of the pixel values ​​of the projected effective area. The count number is the number of integrated effective areas. Therefore, the result of dividing the integrated pixel value by the count number is the average value of the pixel values ​​of the detected image present in the effective area.

[0033] Next, a modified example of switching the X-ray intensity will be described. When the angular range for irradiation from radiation source R1 overlaps with the angular range for irradiation from radiation source R2, control device 20 can control the X-ray intensities of radiation source R1 and radiation source R2 to be different when irradiated from the same angle.

[0034] FIG. 6 shows a modified example of switching between strong and weak sounds. The radiation source R1 irradiates in the order of "strong" and "weak" at rotation angles from "0.0 degrees" to "179.5 degrees" in increments of 0.5 degrees. Radiation source R2 irradiates in the order of "weak" and "strong" at rotation angles from "90.0 degrees" to "269.5 degrees" in 0.5 degree increments. In this case, the rotation angles from 90.0 degrees to 179.5 degrees overlap, and the X-ray intensities of radiation sources R1 and R2 are reversed when irradiating from the same angle. For example, when irradiating at a rotation angle of 90.0 degrees, the X-ray intensity of radiation source R1 is "strong" and the X-ray intensity of radiation source R2 is "weak." In this way, by reversing the intensity when irradiating from the same angle, the accuracy of the cross-sectional image is improved.

[0035] FIG. 7 shows a modification of the four intensity switching modes. The radiation source R1 irradiates by switching between radiation source intensity "P1" and radiation intensity "P2" in increments of 0.5 degrees from the rotation angle "0.0 degrees" to "89.5 degrees." Furthermore, the radiation source R1 irradiates by switching between radiation source intensity "P3" and radiation intensity "P4" in increments of 0.5 degrees from the rotation angle "90.0 degrees" to "179.5 degrees." The radiation source R2 irradiates by switching between radiation source intensity "P1" and radiation intensity "P2" in increments of 0.5 degrees from the rotation angle "90.0 degrees" to "179.5 degrees." In addition, the radiation source R2 irradiates by switching between the radiation source intensity "P3" and the radiation intensity "P4" in increments of 0.5 degrees from the rotation angle "180.0 degrees" to "269.5 degrees." In this way, by using detected images taken at four different X-ray intensities, the accuracy of the cross-sectional image is improved. Furthermore, when radiation source R1 rotates from a rotation angle of 0.0 degrees to 89.5 degrees, and radiation source R2 rotates from a rotation angle of 90.0 degrees to 179.5 degrees, radiation sources R1 and R2 irradiate radiation at radiation source intensities P1 and P2. This makes it possible to reconstruct cross-sectional images with a 90-degree rotation.

[0036] As described above, the image construction system disclosed in the embodiments includes an annular frame (gantry 11) on which an object to be imaged can be placed, radiation sources R1 and R2 that rotate on the frame and irradiate the object to be imaged with radiation from different angles, detectors D1 and D2 that detect the distribution of radiation that has passed through the object to be imaged as detected images, and a control device 20 that reconstructs a cross-sectional image of the object to be imaged using the detected images. The control device 20 obtains a plurality of detected images with different angles and radiation intensities by rotating the radiation source and switching the radiation intensities, extracts an effective area for each of the plurality of detected images, complements areas that are not effective areas for each of the plurality of detected images using effective areas of other detected images to generate a complementary detected image, and reconstructs the cross-sectional image from the plurality of complementary detected images. This makes it possible to realize a highly versatile system that generates highly accurate cross-sectional images. In more detail, by alternately irradiating strong and weak radiation and capturing detected images, it is possible to obtain, within one rotation, a detected image with a high signal-to-noise ratio in the thick region at the center of the subject, and a detected image that can depict the contours of the subject without saturation in the thin region at the periphery of the subject, without increasing the imaging time. In detected images taken with strong radiation, pixel values ​​saturate and become constant in the peripheral areas of the subject, and do not provide accurate measurement values ​​that represent the structure of the subject. Therefore, if reconstruction processing is performed in this state, the structure of the subject will disappear or artifacts will occur in the reconstructed image that includes the saturated areas. Therefore, by performing reconstruction processing by replacing pixel values ​​in the saturated region with pixel values ​​in a detected image captured with weak radiation, the structure of the saturated region can be compensated for.

[0037] The control device 20 repeatedly switches between a first radiation intensity and a second radiation intensity that is weaker than the first radiation intensity. Then, the control device 20 excludes from the effective area areas where pixel values ​​are saturated for the first detected image obtained by irradiating radiation of the first radiation intensity, and excludes from the effective area areas where pixel values ​​are less than a predetermined value for the second detected image obtained by irradiating radiation of the second radiation intensity. Therefore, saturated regions in the detection image of the first radiation intensity can be complemented with the detection image of the second radiation intensity, and low SN regions in the detection image of the second radiation intensity can be complemented with the detection image of the first radiation intensity.

[0038] Furthermore, the control device 20 changes the radiation intensity by changing the time for which the radiation is irradiated. Therefore, the radiation intensity can be easily switched.

[0039] The control device 20 also generates one complementary detected image from a plurality of detected images acquired within a predetermined angle range. That is, a defective area in a detected image at a certain angle is complemented by a valid area in another detected image at a similar angle, thereby reducing complementation errors and enabling the acquisition of accurate cross-sectional images.

[0040] Specifically, the control device 20 normalizes the multiple detection images by the radiation intensity and projects them onto the one complementary detection image, and sets the average value of the pixel values ​​of the detection images present in the effective area as the pixel value in the one complementary detection image. Therefore, the detected image can be complemented by simple processing.

[0041] The system also includes two radiation sources R1, R2 arranged on the frame in a substantially perpendicular positional relationship, and two detectors D1, D2 corresponding to the two radiation sources R1, R2. The control device 20 switches the radiation intensities of the two radiation sources while rotating the two radiation sources in the same direction, acquires detected images from the two detectors, generates a first complementary detected image from the detected image acquired from the first detector of the two detectors, generates a second complementary detected image from the detected image acquired from the second detector, and reconstructs the cross-sectional image using the first complementary detected image and the second complementary detected image. This allows cross-sectional images to be generated quickly with a 90-degree rotation.

[0042] Furthermore, when the angle range for irradiation from the first radiation source and the angle range for irradiation from the second radiation source overlap, the control device 20 controls the radiation intensities of the first radiation source and the second radiation source to be different when irradiated from the same angle. Therefore, two radiation sources can be used to improve the accuracy of cross-sectional images.

[0043] <Radiation therapy system configuration> Next, the device configuration of a radiotherapy system incorporating the image construction system of the present invention will be described. As shown in FIG. 8, the radiation therapy system 100 includes a treatment planning device 111, a treatment control device 112, and a radiation therapy device 120.

[0044] The treatment planning device 111 receives three-dimensional image data of patient B, the treatment target, captured in advance by the image construction system of the present invention, and creates a treatment plan that defines the properties of radiation to be irradiated to patient B (such as the dose, time, angle, position, and irradiation area of ​​the radiation to be irradiated to patient B) according to the content of the radiation therapy. Furthermore, in order to irradiate radiation according to the dose, time, angle, and other parameters of the radiation treatment plan, the treatment planning device 111 outputs control parameter values, such as the tilt angle of the radiation source swing mechanism 301 (described below), the rotation angle of the rotating ring 122 relative to the ring frame 121, the rotation axis 125, and the irradiation timing of the radiation irradiator 124, to the treatment control device 112. Long-term treatment plans can also be created. In long-term plans, the overall treatment plan is configured by combining schedules and individual treatment plans, such as the date and treatment plan for the first irradiation treatment, the date and treatment plan for the second irradiation treatment, and so on.

[0045] The treatment control device 112 has the function of the control device 20 of the image construction system and the function of controlling the irradiation of therapeutic radiation. The treatment control device 112 operates in the same manner as the control device 20 described above, and transmits three-dimensional image data to the treatment planning device 111 . The treatment control device 112 also controls the operation of the radiation therapy device 120 based on the control parameter values ​​(irradiation plan) received from the treatment planning device 111. The treatment control device 112 is configured with a CPU and memory, and the CPU reads and executes a program pre-stored in the memory, thereby performing control operations by software.

[0046] FIG. 9 is a perspective view showing a schematic configuration of the radiotherapy device 120. As shown in FIG.

[0047] As shown in Fig. 9, the radiation therapy apparatus 120 includes a radiation irradiator 124, a gantry 11, a couch 128, and a swaying mechanism 301. The gantry 11 supports the radiation irradiator 124 and rotates the radiation irradiator 124 around an isocenter C0. The couch 128 positions the treatment target area of ​​the patient at the isocenter C0. The swaying mechanism 301 is disposed between the radiation irradiator 124 and the gantry 11, and oscillates the radiation irradiator 124 to oscillate the irradiation axis of the radiation irradiated by the radiation irradiator 124.

[0048] The gantry 11 is a rotation mechanism that includes a ring frame 121 and a rotation ring 122 . The ring frame 121 is disposed so that its central axis C1 faces substantially horizontally. The outer peripheral surface of the rotatable ring 122 is supported by the inner peripheral surface of the ring frame 121, and is structured so as to be rotatable along the inner peripheral surface of the ring frame 121. The rotatable ring 122 is driven by a rotation drive mechanism (not shown) and rotates around the rotation central axis C1.

[0049] A rotating shaft 125 extending downward is integrally formed on the outer peripheral surface of the lower end portion 121a of the ring frame 121, and this rotating shaft 125 is supported on a base (not shown) in a state in which it can rotate (swivel) around its vertical central axis (swivel axis) C2. A swivel drive mechanism (not shown) rotates the ring frame 121 around the swivel axis C2.

[0050] The radiation irradiation device 124 is mounted on a gimbal-structured swing mechanism 301 and is supported by the rotating ring 122 via the swing mechanism 301 .

[0051] When the oscillating mechanism 301 is not operating, the radiation Sr emitted from the radiation irradiation device 124 is adjusted to pass through the isocenter C0, which is the intersection of the central axis C1 of the rotating ring 122 and the rotation axis C2 of the ring frame 121.

[0052] The radiation therapy device 120 further includes a sensor array 123. The sensor array 123 receives radiation that is emitted by the radiation irradiation device 124 and passes through a subject around the isocenter C0, and generates a transmission image of the subject. The sensor array 123 may be an EPID (Electronic Portal Imaging Device), an FPD (Flat Panel Detector), an X-ray II (Image Intensifier), or the like.

[0053] The radiation therapy device 120 also includes radiation sources R1 and R2, which are imaging X-ray sources, and detectors D1 and D2, which are sensor arrays. The radiation sources R1 and R2 and the detectors D1 and D2 are disposed on the inner periphery of the rotating ring 122 and supported by the rotating ring 122. The radiation sources R1 and R2 are directed to emit imaging X-rays toward the isocenter C0. The imaging X-rays are cone-shaped. The detectors D1 and D2 are disposed opposite the radiation sources R1 and R2 across the isocenter C0, and receive the imaging X-rays emitted from the radiation sources R1 and R2 and transmitted through the subject around the isocenter C0 to generate a transmission image of the subject. The detectors D1 and D2 can be, for example, FPDs, X-ray IIs, etc.

[0054] The couch drive device 129 is controlled by the treatment control device 112 and is capable of moving the couch 128 at least parallel to the central axis of rotation C1.

[0055] The oscillating mechanism 301 has a gimbal structure on which the radiation irradiation device 124 is mounted, and can tilt the radiation irradiation device 124 around two axes, a pan axis 301a and a tilt axis 301b. The pan axis 301a is an axis perpendicular to both the rotation center axis C1 and the swivel center axis C2. The tilt axis 301b is an axis parallel to the rotation center axis C1.

[0056] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, not only can the configurations be deleted, but also replacements and additions of configurations are possible. For example, a cross-sectional image may be reconstructed by rotating one radiation source by 180 degrees. Also, other radiations may be used instead of X-rays. In addition, in the examples, a configuration has been described in which a gantry, which is a ring-shaped frame, is provided and the radiation source rotates on a track formed by the frame, but the ring-shaped frame is not essential, and any configuration may be used as long as the radiation source can irradiate radiation from different angles to the imaging subject. [Explanation of symbols]

[0057] 11: Gantry, 20: Control device, 21: Gantry drive unit, 22: X-ray irradiation control unit, 23: Image processing unit, 24: Display unit, D1: Detector, D2: Detector, R1: Radiation source, R2: Radiation source

Claims

1. a radiation source that rotates around an object to be imaged and irradiates the object with radiation from different angles; a detector that detects a distribution of radiation that has passed through the object to be imaged as a detected image; a control device that reconstructs a cross-sectional image of the object using the detected image, The control device acquiring a plurality of detection images with different angles and radiation intensities by switching the radiation intensity while rotating the radiation source; extracting an effective area for each of the plurality of detected images; generating a complementary detected image by complementing an area that is not an effective area of ​​each of the plurality of detected images using an effective area of ​​another detected image; The cross-sectional image is reconstructed from a plurality of complementary detected images. An image construction system comprising:

2. 10. The image construction system of claim 1, The image construction system, wherein the control device repeatedly switches between a first radiation intensity and a second radiation intensity that is weaker than the first radiation intensity.

3. 3. The image construction system of claim 2, the control device excludes from the effective area an area in which pixel values ​​are saturated for a first detected image obtained by irradiating radiation of the first radiation intensity, and excludes from the effective area an area in which pixel values ​​are less than a predetermined value for a second detected image obtained by irradiating radiation of the second radiation intensity.

4. 10. The image construction system of claim 1, The image construction system is characterized in that the control device switches the radiation intensity by changing the time for which the radiation is irradiated.

5. 10. The image construction system of claim 1, The image construction system is characterized in that the control device generates one complementary detected image from a plurality of detected images acquired within a predetermined angle range.

6. 6. The image construction system of claim 5, The control device normalizing the plurality of detected images by the radiation intensity and projecting the normalized detected images onto the single complementary detected image; An image construction system, characterized in that an average value of pixel values ​​of detected images existing in an effective area is set as a pixel value in said one complementary detected image.

7. 10. The image construction system of claim 1, an annular frame on which the subject to be photographed can be placed; two radiation sources disposed on the frame in a substantially perpendicular positional relationship, each irradiating the imaging subject with radiation; two detectors corresponding to the two radiation sources; The control device rotating the two radiation sources in the same direction while switching the radiation intensities of the two radiation sources; Acquiring detected images from the two detectors, respectively; generating a first complementary detected image from a detected image acquired from a first detector of the two detectors, and generating a second complementary detected image from a detected image acquired from a second detector; The cross-sectional image is reconstructed using the first complementary detected image and the second complementary detected image. An image construction system comprising:

8. 8. The image construction system of claim 7, The control device When the angle range in which irradiation from the first radiation source is performed and the angle range in which irradiation from the second radiation source is performed overlap, An image construction system, characterized by controlling the radiation intensities of the first radiation source and the second radiation source to be different when irradiated from the same angle.

9. 1. An image construction method using an image construction system including: a radiation source that rotates around an object to be photographed and irradiates the object with radiation from different angles; a detector that detects, as a detected image, an intensity distribution of the radiation that has passed through the object to be photographed; and a control device that reconstructs a cross-sectional image of the object to be photographed using the detected image, The control device acquiring a plurality of detection images with different angles and radiation intensities by rotating the radiation source and switching the radiation intensities; extracting an effective area for each of the plurality of detected images; a step of generating a complementary detected image by complementing an area that is not an effective area of ​​each of the plurality of detected images using an effective area of ​​another detected image; reconstructing the cross-sectional image from a plurality of complementary detected images; 10. An image construction method comprising:

10. a therapeutic radiation source that rotates around the treatment target and irradiates the treatment target with therapeutic radiation from different angles; an imaging radiation source that rotates around the treatment target and irradiates the treatment target with imaging radiation from different angles; a detector that detects a distribution of radiation for imaging that has passed through the treatment target as a detected image; a control device that reconstructs a cross-sectional image of the treatment target using the detected image and controls the therapeutic radiation source based on the reconstructed cross-sectional image; Equipped with The control device acquiring a plurality of detection images with different angles and radiation intensities by rotating the imaging radiation source and switching the radiation intensities; extracting an effective area for each of the plurality of detected images; generating a complementary detected image by complementing an area that is not an effective area of ​​each of the plurality of detected images using an effective area of ​​another detected image; The cross-sectional image is reconstructed from a plurality of complementary detected images. A radiation therapy system characterized by:

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