Image processing device, image processing method, and image processing program

Abstract

This image processing device generates a plurality of first partial-angle reconstructed images on the basis of projection data obtained by irradiating a subject with radiation from a first position, generates a plurality of second partial-angle reconstructed images on the basis of projection data obtained by irradiating the subject with radiation from a second position facing the first position across the subject, generates motion information representing motion of the subject, using the plurality of first partial-angle reconstructed images and the plurality of second partial-angle reconstructed images, and generates a CT image in which the motion of the subject is corrected, using the projection data and the motion information.

Description

Image processing device, image processing method, and image processing program

[0001] The present disclosure relates to an image processing device, an image processing method, and an image processing program.

[0002] Japanese Patent Application Laid-Open No. 2022-162956 discloses a technique for generating a plurality of partial angle reconstruction images based on scan data created by scanning a subject with a computed tomography apparatus.

[0003] During imaging by a CT (Computed Tomography) device, the body part of the imaging target may move due to the subject's heartbeat, breathing, etc. In this case, the image quality of the CT image may be degraded.

[0004] The present disclosure has been made in consideration of the above circumstances, and aims to provide an image processing device, an image processing method, and an image processing program that can suppress degradation of image quality of CT images caused by movement of the subject.

[0005] A first aspect of the image processing device is an image processing device that has at least one processor and performs processing on images obtained by a CT device, wherein the processor generates a plurality of first partial angle reconstructed images corresponding to a plurality of positions along the body axis direction of the subject based on projection data obtained by irradiating radiation toward the subject from a first position, generates a plurality of second partial angle reconstructed images corresponding to the plurality of positions based on projection data obtained by irradiating radiation toward the subject from a second position opposite the first position across the subject, generates motion information representing the motion of the subject using the plurality of first partial angle reconstructed images and the plurality of second partial angle reconstructed images, and generates a CT image corrected for the motion of the subject using the projection data and motion information obtained by the CT device.

[0006] The image processing device of the second aspect is the image processing device of the first aspect, wherein the processor generates motion information by aligning a plurality of first partial angle reconstructed images with a plurality of second partial angle reconstructed images.

[0007] The image processing device of the third aspect is the image processing device of the first or second aspect, in which the processor determines the conditions for generating the first partial angle reconstructed image and the second partial angle reconstructed image depending on the part of the subject being imaged by the CT device.

[0008] In a fourth aspect of the image processing device, in the third aspect, the generation conditions include the number of first partial angle reconstructed images and the second partial angle reconstructed images to be generated and a generation range.

[0009] In a fifth aspect of the image processing device, in the image processing device of the fourth aspect, the processor generates a greater number of images per unit length in the body axis direction when the part to be photographed is set as a part having movement in the body axis direction than when the part to be photographed is not set as a part having movement in the body axis direction.

[0010] In the image processing device of the sixth aspect, in the image processing device of the fourth or fifth aspect, when the part to be imaged is a part set as having movement in the body axis direction, the processor widens the range of the body axis direction used to generate the first partial angle reconstructed image and the second partial angle reconstructed image in the projection data obtained by irradiating radiation from one position compared to when the part to be imaged is a part not set as having movement in the body axis direction.

[0011] An image processing device of a seventh aspect is the image processing device of any one of the third to sixth aspects, wherein the processor determines the generation conditions based on a scout image.

[0012] An image processing device of an eighth aspect is an image processing device of any one of the first to seventh aspects, in which the processor controls to display in an identifiable manner the parts of the CT image that have changed due to correction of the movement of the subject.

[0013] A ninth aspect of the image processing method includes at least one processor, and the processor of the image processing device that processes images obtained by a CT device generates a plurality of first partial angle reconstructed images corresponding to a plurality of positions along the body axis direction of the subject based on projection data obtained by irradiating radiation toward the subject from a first position, generates a plurality of second partial angle reconstructed images corresponding to the plurality of positions based on projection data obtained by irradiating radiation toward the subject from a second position opposite the first position across the subject, generates motion information representing the motion of the subject using the plurality of first partial angle reconstructed images and the plurality of second partial angle reconstructed images, and performs processing to generate a CT image corrected for the motion of the subject using the projection data and motion information obtained by the CT device.

[0014] The image processing program of the tenth aspect has at least one processor, and causes the processor of an image processing device that processes images obtained by a CT device to perform the following processes: generate a plurality of first partial angle reconstructed images corresponding to a plurality of positions along the body axis of the subject based on projection data obtained by irradiating radiation toward the subject from a first position; generate a plurality of second partial angle reconstructed images corresponding to the plurality of positions based on projection data obtained by irradiating radiation toward the subject from a second position opposite the first position across the subject; generate motion information representing the motion of the subject using the plurality of first partial angle reconstructed images and the plurality of second partial angle reconstructed images; and generate a CT image corrected for the motion of the subject using the projection data and motion information obtained by the CT device.

[0015] According to the present disclosure, it is possible to suppress degradation of image quality of CT images caused by movement of a subject.

[0016] FIG. 1 is a schematic front view showing an example of the configuration of a tomographic imaging system. FIG. 2 is a schematic side view for explaining a multi-slice CT apparatus. FIG. 3 is a block diagram showing an example of the hardware configuration of a console. FIG. 4 is a diagram for explaining a determination model. FIG. 5 is a diagram for explaining degradation of image quality of a CT image. FIG. 6 is a block diagram showing an example of the functional configuration of a console. FIG. 7 is a schematic side view for explaining generation processing of a partial angle reconstruction image. FIG. 8 is a diagram for explaining generation conditions of a partial angle reconstruction image. FIG. 9 is a diagram for explaining the generation range of a partial angle reconstruction image. FIG. 10 is a diagram for explaining the generation range of a partial angle reconstruction image. FIG. 11 is a diagram showing an example of an estimation result of the movement of a subject according to the breath-holding state of the subject. FIG. 12 is a flowchart showing an example of tomographic image generation processing.

[0017] Hereinafter, examples of embodiments for carrying out the technology of the present disclosure will be described in detail with reference to the drawings.

[0018] First, the configuration of a tomography system 10 according to this embodiment will be described with reference to Fig. 1. As shown in Fig. 1, the tomography system 10 includes a CT device 11 and a console 12. The console 12 is an example of an image processing device that processes images obtained by the CT device 11.

[0019] The CT device 11 obtains a tomographic image of the subject H by capturing an image of the subject H using X-rays, an example of radiation. The CT device 11 includes a gantry 18 and a bed device 19. FIG. 1 is a front view of the gantry 18 and the bed device 19. The bed device 19 includes a tabletop 19A on which the subject H can be placed in a supine position. In the following description, the body axis direction of the subject H (i.e., the longitudinal direction of the tabletop 19A) is defined as the Z-axis direction, the width direction of the subject H perpendicular to the Z-axis direction (i.e., the lateral direction of the tabletop 19A) is defined as the X-axis direction, and the height direction of the subject H (i.e., the vertical direction) is defined as the Y-axis direction. The tabletop 19A can move in the Z-axis direction while remaining horizontal. The gantry 18 has an overall annular shape, and a circular opening 18A having a diameter greater than the width of the tabletop 19A is formed in the center. During imaging, the tabletop 19A on which the subject H is placed moves in the Z-axis direction relative to the gantry 18, thereby entering the opening 18A. Imaging is performed while the tabletop 19A is moving relative to the gantry 18.

[0020] A radiation source 21, a radiation detector 22, and a frame 23 are arranged inside the gantry 18. The radiation source 21 irradiates radiation toward the subject H. The radiation detector 22 detects the radiation that has passed through the subject H. The radiation that has passed through the subject H is attenuated by interaction with structures such as organs and bones inside the subject H (for example, absorption and scattering of radiation). Each structure has its own unique attenuation coefficient for radiation, and the radiation that has passed through a structure carries information reflecting the physical properties of the structure. The radiation detector 22 detects radiation that reflects the physical properties of the structures inside the subject H. The radiation detector 22 has a detection surface on which detection elements are arranged two-dimensionally, and outputs a detection signal for each detection element. Therefore, the radiation detector 22 can detect radiation at each transmission position where it passes through the structure of the subject H. Furthermore, the radiation detector 22 has a substantially arc-shaped configuration in accordance with the curvature of the gantry 18, and the detection surface is also curved.

[0021] The radiation source 21 and the radiation detector 22 are disposed in opposing positions within the gantry 18, and rotate around the Z-axis while maintaining their opposing orientation. The frame 23 is annular and rotatably supports the radiation source 21 and the radiation detector 22. During imaging, the gantry 18 rotates the radiation source 21 and the radiation detector 22 around the subject H on the tabletop 19A, and acquires detection signals from the radiation detector 22 at a plurality of positions in the circumferential direction around the Z-axis, which corresponds to the body axis of the subject H. During imaging, the tabletop 19A also moves in the Z-axis direction in synchronization with the rotation of the radiation source 21 and the radiation detector 22.

[0022] The DAS (Data Acquisition System) 25 collects detection signals output by the radiation detector 22, generates projection data for each position around the Z axis based on the collected detection signals, and outputs the generated projection data to the console 12. In this way, the console 12 acquires radiation projection data for each position around the body axis of the subject H.

[0023] An irradiation field limiter 24 (also called a collimator) that limits the radiation irradiation field is disposed in front of the radiation source 21 in the irradiation direction. The irradiation field limiter 24 has an irradiation aperture whose outline is defined by a plurality of shielding plates that block radiation, and the size of the irradiation aperture can be changed by moving the shielding plates. A voltage is supplied to the radiation source 21 from a high-voltage generator 26. The radiation source 21 and the radiation detector 22 are electrically connected to the frame 23, for example, by a slip ring system, and power supply and data transmission / reception are performed via the slip ring. The slip ring system connection enables helical scan imaging, in which the radiation source 21 and the radiation detector 22 are rotated in one direction without reversing the rotation direction.

[0024] The console 12 controls the radiation source 21 and the radiation detector 22 via a control device (not shown) provided in the gantry 18. Imaging conditions of the CT device 11 are set by operations from the console 12. The imaging conditions include the radiation irradiation conditions of the radiation source 21 and the imaging range, etc. The radiation irradiation conditions include the tube voltage (unit: kV), tube current (unit: mA), and radiation irradiation time (unit: msec) applied to the radiation source 21. The imaging range is adjusted, for example, in the X-Z plane by changing the size of the irradiation opening of the irradiation field limiter 24, and in the Z-axis direction by changing the movement range of the tabletop 19A.

[0025] As shown in Fig. 2, the radiation detector 22 according to this embodiment has a plurality of detector elements arranged along the Z-axis direction. Therefore, based on projection data obtained by irradiating radiation from the radiation source 21 at one position, i.e., by a single radiation irradiation, a plurality of tomographic images representing a plurality of cross sections corresponding to a plurality of different positions along the Z-axis direction can be obtained. Such a CT device is called a multi-slice CT device. In this embodiment, an example will be described in which a tomographic image representing an axial cross section is used as the tomographic image.

[0026] The hardware configuration of the console 12 according to this embodiment will be described with reference to FIG. 3 . Examples of the console 12 include a computer such as a personal computer or a server computer. As shown in FIG. 3 , the console 12 includes a CPU (Central Processing Unit) 31, a memory 32 serving as a temporary storage area, and a non-volatile storage unit 33. The console 12 also includes a display 34 such as a liquid crystal display, an input device 35 such as a keyboard and a mouse, and a network I / F (Interface) 36 connected to the CT device 11. The CPU 31, the memory 32, the storage unit 33, the display 34, the input device 35, and the network I / F 36 are connected to a bus 37. The CPU 31 is an example of a processor according to the disclosed technology.

[0027] The storage unit 33 is realized by a hard disk drive (HDD), a solid state drive (SSD), a flash memory, or the like. The storage unit 33 serves as a storage medium and stores an image processing program 40. The CPU 31 reads the image processing program 40 from the storage unit 33, loads it into the memory 32, and executes the loaded image processing program 40.

[0028] The storage unit 33 also stores a determination model 42 used for determining whether the breath-holding state of the subject H when the CT image is taken is poor. As shown in FIG. 4 , the determination model 42 is a model that receives motion information representing the motion of the subject H as input and outputs the breath-holding state of the subject H. The determination model 42 is a trained model obtained in advance by machine learning using the motion information as learning data and labels representing the breath-holding state of the subject H. In this embodiment, an example will be described in which three states, "good," "poor 1," and "poor 2," are applied as the breath-holding state of the subject H. "Poor 2" means that the breath-holding state of the subject H is worse than "poor 1." Specifically, "good" represents a state in which the CT image can be interpreted without correction, "poor 1" represents a state in which the CT image can be interpreted if corrected, and "poor 2" represents a state in which interpretation is difficult even if the CT image is corrected. The breath-holding state of the subject H is not limited to three stages, but may be two stages, good and bad, or may be four or more stages.

[0029] Incidentally, as shown in Fig. 5 as an example, if the breath-holding state of subject H is poor, the image quality of the CT image may be degraded. Fig. 5 shows an example in which the vicinity of the diaphragm is blurred and the structure around the diaphragm is unclear as a result of subject H not holding his breath properly in a chest CT image. Therefore, the console 12 according to this embodiment has a function of determining whether the breath-holding state of subject H is poor or not, and correcting the CT image based on the determination result.

[0030] Next, the functional configuration of the console 12 will be described with reference to Fig. 6. As shown in Fig. 6, the console 12 includes a first imaging control unit 50, a recognition unit 52, a condition setting unit 54, a second imaging control unit 56, a first reconstructor 58, a generation unit 60, a determination unit 62, a second reconstructor 64, and a display control unit 66. When the CPU 31 executes the image processing program 40, the console 12 functions as the first imaging control unit 50, the recognition unit 52, the condition setting unit 54, the second imaging control unit 56, the first reconstructor 58, the generation unit 60, the determination unit 62, the second reconstructor 64, and the display control unit 66.

[0031] The first imaging control unit 50 controls the radiation source 21 and the radiation detector 22 to capture a scout image. For example, the first imaging control unit 50 controls the position of the radiation source 21 to a position directly facing the subject H, and controls the radiation to be irradiated in one direction toward the subject H. The radiation detector 22 detects the radiation that has passed through the subject H, and outputs a two-dimensional radiographic image. This radiographic image is called a scout image.

[0032] The recognition unit 52 performs organ recognition processing on the scout image obtained under the control of the first imaging control unit 50, depending on the body part of the subject to be imaged. For example, when the body part of the subject to be imaged is the chest or abdomen, the recognition unit 52 recognizes the positions of the chest, abdomen, heart, etc. in the scout image. Examples of organ recognition processing include processing using a known organ recognition algorithm and processing using a trained model obtained by machine learning such as deep learning.

[0033] The condition setting unit 54 sets scan conditions including the above-mentioned imaging conditions, the movement pitch of the bed device 19, and the size of the irradiation opening of the irradiation field limiter 24, based on the body part to be imaged, the imaging purpose, and the organ recognition results by the recognition unit 52.

[0034] The second imaging control unit 56 captures CT images by helical scanning by controlling the movement of the tabletop 19A, the radiation source 21, and the radiation detector 22 in accordance with the scan conditions set by the condition setting unit 54. Through this control, radiation projection data for each position around the body axis of the subject H is obtained.

[0035] As shown in FIG. 7 , the first reconstruction unit 58 generates a plurality of first partial angle reconstructed images G1 corresponding to a plurality of positions along the body axis direction of the subject H (i.e., the Z-axis direction) based on projection data obtained by irradiating radiation from a first position toward the subject H. The plurality of first partial angle reconstructed images G1 are tomographic images representing cross sections at a plurality of positions along the body axis direction, and can therefore be treated as three-dimensional images. The first positions are, for example, points P1, P2, and P3 shown in FIG. 7 . To generate the CT images, projection data obtained by irradiating radiation from the radiation source 21 at a plurality of positions within an angular range of 180° or more, such as 270° or 360° around the Z-axis, is used. To generate the first partial angle reconstructed image G1, projection data obtained by irradiating radiation from the radiation source 21 at a plurality of positions within a partial angular range of less than 180° around the Z-axis is used. In the example of Figure 7, the range of positions of the radiation source 21 when the projection data used to generate the first partial angle reconstruction image G1 was obtained is indicated by arrow Y1, and is shown to be within a range of 60° around the Z axis.

[0036] The first reconstruction unit 58 generates a plurality of second partial angle reconstructed images G2 corresponding to a plurality of positions along the body axis direction of the subject H, based on projection data obtained by irradiating the subject H with radiation from a second position opposite the first position across the subject H. The plurality of second partial angle reconstructed images G2 are tomographic images representing cross sections at a plurality of positions along the body axis direction, and can therefore be treated as three-dimensional images. The second positions are, for example, points P4, P5, and P6 shown in FIG. 7 . Points P4, P5, and P6 are opposite points P1, P2, and P3, respectively, across the subject H. As with the generation of the first partial angle reconstructed image G1, the generation of the second partial angle reconstructed image G2 uses projection data obtained by irradiating radiation from the radiation source 21 at a plurality of positions within a partial angular range of less than 180° around the Z axis. In the example of Figure 7, the range of positions of the radiation source 21 when the projection data used to generate the second partial angle reconstruction image G2 was obtained is indicated by arrow Y2, and is shown to be within a range of 60 degrees around the Z axis.

[0037] The first reconstruction unit 58 generates a first partial angle reconstructed image G1 and a second partial angle reconstructed image G2 by reconstructing images based on the projection data. The reconstruction of images based on the projection data is performed, for example, by filtered back projection.

[0038] As described above, since the first position and the second position are opposite each other across the subject H, the edges of the first partial angle reconstructed image G1 and the edges of the second partial angle reconstructed image G2 are oriented in the same direction.

[0039] The first reconstructor 58 may determine the generation conditions for the first partial angle reconstructed image G1 and the second partial angle reconstructed image G2 based on the scout image. In this case, for example, the first reconstructor 58 may determine the generation conditions according to the organ recognition result for the scout image by the recognition unit 52.

[0040] The conditions for generating the first partial angle reconstructed image G1 and the second partial angle reconstructed image G2 may include the number of images to be generated and the generation range of the first partial angle reconstructed image G1 and the second partial angle reconstructed image G2. The number of images to be generated here may be the number of images to be generated per unit length in the body axis direction of the subject H. Furthermore, the generation range here may be the range in the body axis direction of the subject H used to generate the first partial angle reconstructed image G1 and the second partial angle reconstructed image in projection data obtained by irradiating radiation from one position.

[0041] Furthermore, the first reconstructor 58 may determine the conditions for generating the first partial angle reconstructed image G1 and the second partial angle reconstructed image G2 according to the region of the subject imaged by the CT device 11 .

[0042] In this case, as shown in Figure 8 as an example, when the part to be imaged is a part that has been set as having movement in the body axis direction, the first reconstruction unit 58 may generate a larger number of images per unit length in the body axis direction than when the part to be imaged is a part that has not been set as having movement in the body axis direction.

[0043] In this case, as shown in FIG. 8 as an example, when the part to be imaged is a part that has been set as having movement in the body axis direction, the first reconstruction unit 58 may use a wider range of the body axis direction to generate the first partial angle reconstructed image G1 and the second partial angle reconstructed image G2 in the projection data obtained by irradiating radiation from one position, compared to when the part to be imaged is a part that has not been set as having movement in the body axis direction.

[0044] The example of Fig. 8 shows an example of the number of images generated and the generation range when the chest including the heart and the abdomen including the diaphragm are set as regions having movement in the body axis direction, and regions other than the chest and abdomen, such as the head and feet, are not set as regions having movement in the body axis direction. In the example of Fig. 8, the number of first partial angle reconstructed images G1 and second partial angle reconstructed images generated per unit length in the body axis direction is greater for the chest and abdomen than for the head and feet. Also, in the example of Fig. 8, the range of the body axis direction used to generate the first partial angle reconstructed image G1 and the second partial angle reconstructed image in projection data obtained by irradiating radiation from one position is wider for the chest and abdomen than for the head and feet.

[0045] The range of the body axis direction used to generate the first partial angle reconstructed image G1 and the second partial angle reconstructed image in the projection data obtained by irradiating radiation from one position is controlled, for example, by the range of the body axis direction among the group of detection elements possessed by the radiation detector 22.

[0046] As an example, as shown in FIG. 9 , when the region of the imaged subject is set as a region having movement in the body axis direction, the first reconstruction unit 58 generates a first partial angle reconstructed image G1 and a second partial angle reconstructed image G2 based on projection data detected by the detection elements of the radiation detector 22 in the entire range in the body axis direction.

[0047] 10 , for a region of the imaging target that is not set as a region having movement in the body axis direction, the first reconstruction unit 58 generates a first partial angle reconstructed image G1 and a second partial angle reconstructed image G2 based on projection data detected by detection elements in a partial range in the body axis direction of the radiation detector 22. In this case, the partial range may be a range based on the center of the body axis direction of the radiation detector 22. In other words, the partial range in this case may be a range excluding the ends of the body axis direction of the radiation detector 22. This makes it possible to reduce the calculation cost for a region of the imaging target that is not set as a region having movement in the body axis direction.

[0048] The generation unit 60 generates motion information representing the motion of the subject H using the plurality of first partial angle reconstructed images G1 and the plurality of second partial angle reconstructed images G2 generated by the first reconstruction unit 58. Specifically, the generation unit 60 generates the motion information by aligning the plurality of first partial angle reconstructed images G1 with the plurality of second partial angle reconstructed images G2. The motion information according to this embodiment is a group of vectors including a direction and a movement amount representing which pixel in the first partial angle reconstructed image G1 is located at which pixel in the second partial angle reconstructed image G2.

[0049] The determination unit 62 performs an inadequate breath-holding determination, using the plurality of first partial angle reconstructed images G1 and the plurality of second partial angle reconstructed images G2, to determine whether the breath-holding state of the subject H is poor. In this embodiment, the determination unit 62 performs an inadequate breath-holding determination, using movement information generated by the generation unit 60 based on the plurality of first partial angle reconstructed images G1 and the plurality of second partial angle reconstructed images G2.

[0050] Specifically, the determination unit 62 inputs movement information to the determination model 42. The determination model 42 outputs one of "good," "poor 1," and "poor 2" as the degree of breath-holding of the subject H according to the input movement information. As a result, the determination unit 62 performs a poor breath-holding determination based on the movement information representing the movement of the subject and the determination model 42. That is, the determination unit 62 determines the degree of breath-holding of the subject H as a poor breath-holding determination. Note that the determination unit 62 may also determine whether the subject H is holding his breath.

[0051] Furthermore, the determination model 42 may receive as input at least one of motion information representing the motion of the subject, a plurality of first partial angle reconstructed images G1 and a plurality of second partial angle reconstructed images G2, and CT images that have not yet been subjected to processing for correcting the motion of the subject based on the motion information and CT images that have been subjected to processing executed by the second reconstruction unit 64 described below. That is, the determination unit 62 may perform a breath-holding insufficiency determination based on at least one of these and the determination model 42.

[0052] The second reconstruction unit 64 generates a CT image in which the movement of the subject H has been corrected, using the projection data obtained by the CT device 11 and the motion information generated by the generation unit 60. The projection data obtained by the CT device 11 here refers to projection data obtained by irradiating radiation from all positions around the Z axis set when capturing the CT image. A known correction algorithm or a trained model obtained by machine learning is used in the process of correcting the movement of the subject H. The second reconstruction unit 64 generates a CT image in which the movement of the subject H has been corrected, by reconstructing an image based on the projection data and then correcting the movement using the motion information. The reconstruction of an image based on the projection data is performed, for example, by filtered back projection.

[0053] As an example, as shown in FIG. 11 , the estimated motion of subject H varies depending on the breath-holding state of subject H. In the example of FIG. 11 , the darker the color, the greater the movement of subject H. When the breath-holding state corresponds to “good,” the movement of subject H is relatively small. When the breath-holding state corresponds to “poor 1,” the movement of subject H is relatively large, but interpretation is often possible by correcting the CT image. When the breath-holding state corresponds to “poor 2,” the movement of subject H is too large or the movement trend changes suddenly, mainly due to poor breath-holding, resulting in unnatural parts in the estimated motion of subject H. In this case, the CT image cannot be properly corrected, and image quality may be degraded. In the example of FIG. 11 , discontinuous parts occur in the estimated motion due to poor breath-holding, and erroneous correction results in a degradation of image quality. Therefore, the second reconstruction unit 64 according to this embodiment generates CT images by performing different image processing depending on the result of the poor breath-holding determination by the determination unit 62. For example, if the result of the poor breath-holding assessment is "good," the second reconstructor 64 generates a CT image by reconstructing an image based on the projection data without performing correction using the motion information. Furthermore, for example, if the result of the poor breath-holding assessment is "poor 1," the second reconstructor 64 generates a CT image in which the motion of the subject H has been corrected using the motion information. Furthermore, for example, if the result of the poor breath-holding assessment is "poor 2," the second reconstructor 64 narrows the range of the body axis direction of the projection data used to generate the CT image compared to the case of "poor 1," corrects the motion of the subject H, and generates a CT image that has been subjected to noise reduction processing.

[0054] The display control unit 66 controls the display so that portions of the CT image that have changed due to the correction of the movement of the subject H are identifiable. In the present embodiment, when the second reconstruction unit 64 generates a CT image in which the movement of the subject H has been corrected, the display control unit 66 controls the display 34 to display the CT image before correction, the CT image after correction, and a difference image between the CT images before and after correction. This allows the user to understand the portions of the CT image that have been transformed by the correction. The display control unit 66 may also control the display to highlight portions of the CT image that have changed due to the correction of the movement of the subject H.

[0055] The display control unit 66 may perform control to display the result of the poor breath-holding judgment on the display 34. Furthermore, when the part of the imaging target is a part set as a part having movement in the body axis direction, the display control unit 66 may perform control to display the CT image on the display 34 regardless of whether a display instruction is input from the user. In this case, when the part of the imaging target is a part not set as a part having movement in the body axis direction, the display control unit 66 may perform control to display the CT image on the display 34 when a display instruction is received from the user.

[0056] Next, the operation of the console 12 will be described with reference to Fig. 12. The CPU 31 executes the image processing program 40, thereby carrying out the tomographic image generating process shown in Fig. 12.

[0057] 12, the first imaging control unit 50 controls the radiation source 21 and the radiation detector 22 to capture a scout image. In step S12, the recognition unit 52 performs organ recognition processing on the scout image obtained by the control of step S10, depending on the body part of the imaging target. In step S14, the condition setting unit 54 sets scan conditions, including the imaging conditions, the movement pitch of the bed device 19, and the size of the irradiation opening of the irradiation field limiter 24, based on the body part of the imaging target, the imaging purpose, and the organ recognition result of step S12.

[0058] In step S16, the second imaging control unit 56 captures CT images by helical scanning in accordance with the scan conditions set in step S14 by controlling the movement of the tabletop 19A, the radiation source 21, and the radiation detector 22. In step S18, the first reconstruction unit 58 generates a plurality of first partial angle reconstruction images G1 corresponding to a plurality of positions along the body axis direction of the subject H, based on the projection data obtained by irradiating radiation from the first position toward the subject H through the processing of step S16.

[0059] In step S20, the first reconstruction unit 58 generates a plurality of second partial angle reconstructed images G2 corresponding to a plurality of positions along the body axis direction of the subject H, based on the projection data obtained by the processing of step S16 by irradiating radiation toward the subject H from a second position opposite the first position across the subject H. In step S22, the generation unit 60 generates motion information representing the motion of the subject H, using the plurality of first partial angle reconstructed images G1 and the plurality of second partial angle reconstructed images G2 generated in steps S18 and S20.

[0060] In step S24, the determination unit 62 performs a poor breath-holding determination based on the movement information generated in step S22 and the determination model 42. In step S26, the determination unit 62 determines whether the determination result in step S24 is "good." If this determination is positive, the process proceeds to step S28. In step S28, the second reconstruction unit 64 generates a CT image by reconstructing an image based on the projection data without performing correction using the movement information. In step S30, the display control unit 66 controls the display of the CT image generated in step S28 on the display 34. When the process of step S30 ends, the tomographic image generation process ends.

[0061] If the determination in step S26 is negative, the process proceeds to step S32. In step S32, the determination unit 62 determines whether the determination result in step S24 is "Fail 1." If this determination is positive, the process proceeds to step S34. In step S34, the second reconstruction unit 64 generates a CT image in which the movement of the subject H has been corrected using the movement information. When the process of step S34 is completed, the process proceeds to step S38.

[0062] If the determination result in step S24 is "Fail 2," the determination in step S32 becomes negative, and the process proceeds to step S36. In step S36, the second reconstruction unit 64 narrows the range of the body axis direction of the projection data used to generate the CT image compared to the case of "Fail 1," corrects the movement of the subject H, and generates a CT image that has been subjected to noise reduction processing. When the process of step S36 ends, the process proceeds to step S38.

[0063] In step S38, the display control unit 66 controls the display of the pre-correction CT image, the post-correction CT image, and the difference image between the pre-correction and post-correction CT images on the display 34. The pre-correction CT image and the post-correction CT image are generated in step S34 or step S36. When the processing of step S38 ends, the tomographic image generation processing ends.

[0064] As described above, according to this embodiment, it is possible to accurately determine whether or not the breath-holding state of the subject H is poor. Furthermore, according to this embodiment, it is possible to suppress degradation of the image quality of the CT image caused by the movement of the subject H.

[0065] In the above embodiment, the determination unit 62 may determine whether or not the subject H has difficulty holding their breath based on the subject information about the subject H. For example, the determination unit 62 may determine that the subject H has difficulty holding their breath when the age of the subject H included in the subject information is equal to or greater than the age set as the lower limit for elderly people. Furthermore, for example, the determination unit 62 may determine that the subject H has difficulty holding their breath when the age of the subject H included in the subject information is equal to or less than the age set as the upper limit for children. Furthermore, for example, the determination unit 62 may determine that the subject H has difficulty holding their breath when the state of the subject H included in the subject information is unconscious. If the determination unit 62 determines that the subject H has difficulty holding their breath, it may perform a breath-holding insufficiency determination, but if it determines that the subject H does not have difficulty holding their breath, it may not be necessary to perform a breath-holding insufficiency determination.

[0066] Furthermore, in the above embodiment, the second reconstructor 64 may not generate a CT image when the result of the poor breath-holding judgment is "Poor 2." In this case, the display controller 66 may perform control to display, on the display 34, information indicating that a CT image could not be generated because the breath-holding condition of the subject H was poor. Furthermore, when the result of the poor breath-holding judgment is "Good," the second reconstructor 64 may generate a CT image in which the movement of the subject H has been corrected using the movement information, as in the case when the result of the poor breath-holding judgment is "Poor 1."

[0067] Furthermore, the disclosed technology may be applied to correcting head movement, abdominal movement, and limb movement in addition to correcting movement based on poor breath-holding.

[0068] Furthermore, at least one of the functional units included in the console 12 in the above embodiment may be included in another device such as a control device included in the gantry 18 .

[0069] Furthermore, in the above embodiment, the following various processors can be used as the hardware structure of a processing unit that executes various processes, such as each functional unit of the console 12. As described above, the various processors include a CPU, which is a general-purpose processor that executes software (programs) and functions as various processing units, as well as dedicated electrical circuits, such as a programmable logic device (PLD), which is a processor whose circuit configuration can be changed after manufacture, such as an FPGA, and an application specific integrated circuit (ASIC), which is a processor with a circuit configuration designed specifically for executing specific processes.

[0070] A single processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same or different types (for example, a combination of multiple FPGAs, or a combination of a CPU and an FPGA). Also, multiple processing units may be configured with a single processor.

[0071] Examples of configuring multiple processing units with a single processor include: first, a form in which one processor is configured with a combination of one or more CPUs and software, as typified by computers such as client and server computers, and this processor functions as multiple processing units; second, a form in which a processor is used to realize the functions of an entire system including multiple processing units with a single IC (Integrated Circuit) chip, as typified by systems on chips (SoCs); in this way, various processing units are configured using one or more of the above-mentioned various processors as a hardware structure.

[0072] Furthermore, more specifically, the hardware structure of these various processors can be an electric circuit that combines circuit elements such as semiconductor elements.

[0073] In the above embodiment, the image processing program 40 is pre-stored (installed) in the storage unit 33, but this is not limiting. The image processing program 40 may be provided in a form recorded on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or a USB (Universal Serial Bus) memory. The image processing program 40 may also be downloaded from an external device via a network. The image processing program 40 can also be provided as a program product. The program product includes any type of product for providing a program. For example, the program product includes a program provided via a network such as the Internet, and a non-transitory computer-readable recording medium such as a CD-ROM or DVD on which the program is stored.

[0074] The disclosure of Japanese Patent Application No. 2024-153483, filed on September 5, 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. An image processing device having at least one processor for processing images obtained by a CT device, wherein the processor: generates a plurality of first partial angle reconstructed images corresponding to a plurality of positions along the body axis direction of the subject based on projection data obtained by irradiating the subject with radiation from a first position; generates a plurality of second partial angle reconstructed images corresponding to the plurality of positions based on projection data obtained by irradiating the subject with radiation from a second position opposite the first position across the subject; generates motion information representing the motion of the subject using the plurality of first partial angle reconstructed images and the plurality of second partial angle reconstructed images; and generates a CT image with the motion of the subject corrected using the projection data and motion information obtained by the CT device.

2. The image processing device according to claim 1, wherein the processor generates the motion information by aligning the plurality of first partial angle reconstructed images with the plurality of second partial angle reconstructed images.

3. An image processing device as described in claim 1 or claim 2, wherein the processor determines the conditions for generating the first partial angle reconstructed image and the second partial angle reconstructed image depending on the part of the subject being imaged by the CT device.

4. The image processing device according to claim 3, wherein the generation conditions include the number of the first partial angle reconstructed images and the second partial angle reconstructed images to be generated and a generation range.

5. The image processing device described in claim 4, wherein the processor generates a larger number of images per unit length in the body axis direction when the part of the subject to be imaged is set as a part having movement in the body axis direction than when the part of the subject to be imaged is not set as a part having movement in the body axis direction.

6. The image processing device described in claim 4, wherein the processor, when the part of the subject to be imaged is a part set as having movement in the body axis direction, widens the range of the body axis direction used to generate the first partial angle reconstructed image and the second partial angle reconstructed image in the projection data obtained by irradiating radiation from one position, compared to when the part of the subject to be imaged is a part not set as having movement in the body axis direction.

7. The image processing device according to claim 3, wherein the processor determines the generation conditions based on a scout image.

8. An image processing device according to claim 1 or claim 2, wherein the processor performs control to display in an identifiable manner portions of the CT image that have changed as a result of correcting the movement of the subject.

9. An image processing method comprising at least one processor, the processor of an image processing device that processes images obtained by a CT device, generating a plurality of first partial angle reconstructed images corresponding to a plurality of positions along the body axis of the subject based on projection data obtained by irradiating the subject with radiation from a first position, generating a plurality of second partial angle reconstructed images corresponding to the plurality of positions based on projection data obtained by irradiating the subject with radiation from a second position opposite the first position across the subject, generating motion information representing the motion of the subject using the plurality of first partial angle reconstructed images and the plurality of second partial angle reconstructed images, and using the projection data obtained by the CT device and the motion information to generate a CT image in which the motion of the subject has been corrected.

10. An image processing program for causing the processor of an image processing device, which has at least one processor and processes images obtained by a CT device, to execute the following processes: generate a plurality of first partial angle reconstructed images corresponding to a plurality of positions along the body axis of the subject based on projection data obtained by irradiating the subject with radiation from a first position; generate a plurality of second partial angle reconstructed images corresponding to the plurality of positions based on projection data obtained by irradiating the subject with radiation from a second position opposite the first position across the subject; generate motion information representing the motion of the subject using the plurality of first partial angle reconstructed images and the plurality of second partial angle reconstructed images; and generate a CT image in which the motion of the subject has been corrected using the projection data and motion information obtained by the CT device.

Images