Medical image processing device, treatment system, medical image processing method, and storage medium

Abstract

The medical image processing apparatus of this embodiment includes a first image acquisition unit, a second image acquisition unit, a direction acquisition unit, and a motion calculation unit. The first image acquisition unit acquires a first three-dimensional image of the patient's body. The second image acquisition unit acquires a second three-dimensional image of the patient's body, captured at a different time than the first image. The direction acquisition unit acquires information related to the irradiation direction of radiation irradiated onto the patient in the treatment room. The motion calculation unit outputs a motion signal based on the path of the radiation set for the first image and information related to the irradiation direction. This motion signal represents the amount of movement of the second image to align the position of the patient projected in the second image with the position of the patient projected in the first image.

Description

Technical Field

[0001] The embodiments of the present invention relate to medical image processing apparatus, treatment system, medical image processing method and program. Background Technology

[0002] Radiation therapy is a treatment method that destroys tumors (lesions) by irradiating them with radiation. Because irradiating normal tissues can sometimes even damage them, precise targeting of the tumor is crucial in radiation therapy. Therefore, during the treatment planning phase, for example, a computed tomography (CT) scan is performed beforehand to determine the three-dimensional location of the tumor within the patient's body. Then, based on this tumor location, the direction and intensity of the radiation are planned. Finally, during the treatment phase, the patient's position is aligned with the planned position, and radiation is delivered to the tumor according to the planned direction and intensity.

[0003] During patient alignment in the treatment phase, just before treatment begins, a digitally reconstructed radiograph (DRR) image is obtained by comparing a fluoroscopic image of the patient's body taken with the patient lying on the examination table with a 3D CT image virtually reconstructed from the fluoroscopic image taken according to the treatment plan. The offset of the patient's position between these images is determined. Then, the examination table is moved based on the determined offset to align the positions of tumors, bones, etc., within the patient's body with their positions according to the treatment plan.

[0004] The patient's positional shift is determined by searching for locations within CT images in order to reconstruct a DRR image that most closely resembles the fluoroscopic image. Previously, many methods have been proposed to automate the search for the patient's position using computers. However, in the past, users (doctors, etc.) have verified the results of the automated search by comparing the fluoroscopic image with the DRR image.

[0005] At this point, it can be difficult to visually confirm the location of the tumor on fluoroscopic images. This is because tumors have higher X-ray transmittance compared to bones, so they are not clearly visible on fluoroscopic images. Therefore, CT scans are sometimes taken instead of fluoroscopic images to confirm the tumor's location during treatment. In this case, the patient's positional shift is determined by comparing CT images taken during treatment planning with those taken during treatment itself—that is, by comparing the CT images one by one.

[0006] In image comparison of CT images, the position of one CT image is moved while the position of the other CT image is determined. As an example of a method for image comparison of CT images, the method disclosed in Patent Document 1 is provided. In the method disclosed in Patent Document 1, an image of the area surrounding the tumor included in a CT image taken during treatment planning is prepared as a template. The location of the most similar image is searched as the location of the tumor by performing template matching on CT images taken during treatment. Furthermore, based on the searched location, the patient's positional offset is determined, and the examination table is moved according to the offset, similarly to the above, so that the patient's position conforms to the same posture as in the treatment plan. In the method disclosed in Patent Document 1, in addition to scanning the prepared template in three dimensions, a search method is also mentioned that involves changing the posture of the template, such as tilting it, to perform the scan.

[0007] However, the method disclosed in Patent Document 1 focuses on aligning the location of the area surrounding the tumor with a CT image of the area surrounding the tumor prepared as a template. Therefore, in the method disclosed in Patent Document 1, the location of the patient's internal tissues, even outside the tumor's periphery, is not necessarily precisely aligned. That is, even when aligning the patient's position using the method disclosed in Patent Document 1, even if the irradiated radiation reaches the tumor, sometimes the planned radiation energy cannot be delivered to the tumor due to tissues within the patient's body located along the radiation path.

[0008] It should be noted that radiation used in radiotherapy loses energy as it passes through matter. Therefore, in traditional treatment planning, the method of radiation exposure was determined by virtually calculating the energy loss of the irradiated radiation based on captured CT images. Considering this, it is crucial that the patient's tissues are aligned with the path of the irradiated radiation during treatment.

[0009] As an example of a method for comparing CT images with each other, focusing on this point, there is a method disclosed in Patent Document 2. In the method disclosed in Patent Document 2, CT images are compared using CT images that have been transformed by calculating the arrival energy of radiation per pixel. However, in the method disclosed in Patent Document 2, DRR images reconstructed from the transformed CT images are also used for image comparison. That is, in the method disclosed in Patent Document 2, the images used for image comparison are also in a state that has lost the three-dimensional image information possessed by the CT images.

[0010] Furthermore, a method combining the method disclosed in Patent Document 2 with that disclosed in Patent Document 1, using modified CT images for template matching to align the patient, could be considered. However, since the method for calculating the energy of arrival varies depending on the direction of the irradiated radiation, if the posture of the template used in template matching is changed, the energy of arrival needs to be recalculated each time. Therefore, even when the method disclosed in Patent Document 2 is combined with that disclosed in Patent Document 1, if the need to prepare many templates in advance according to the posture and focus on the periphery of the tumor for alignment is considered, alignment, including the patient's internal tissues along the path of radiation, cannot be easily performed.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent No. 5693388

[0014] Patent Document 2: U.S. Patent Application Publication No. 2011 / 0058750 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] The problem this invention aims to solve is to provide a medical image processing apparatus, treatment system, medical image processing method, and program that can properly perform three-dimensional image comparison to align the patient's position.

[0017] Methods for solving problems

[0018] One embodiment of the medical image processing apparatus includes a first image acquisition unit, a second image acquisition unit, a direction acquisition unit, and a motion calculation unit. The first image acquisition unit acquires a first three-dimensional image of the patient's body. The second image acquisition unit acquires a second three-dimensional image of the patient's body, captured at a different time than the first image. The direction acquisition unit acquires information related to the irradiation direction of radiation irradiated onto the patient in the treatment room. The motion calculation unit outputs a motion signal based on the path of the radiation set for the first image and information related to the irradiation direction. This motion signal represents the amount of movement of the second image to align the position of the patient projected in the second image with the position of the patient projected in the first image.

[0019] Invention Effects

[0020] Based on the above method, a medical image processing device, treatment system, medical image processing method, and program can be provided that can perform high-speed and high-precision image comparison of CT images taken during treatment planning and treatment phases to align the patient's position. Attached Figure Description

[0021] Figure 1 This is a block diagram illustrating a simplified structure of a treatment system equipped with the medical image processing apparatus of the first embodiment.

[0022] Figure 2 This is a block diagram showing a simplified structure of the medical image processing apparatus according to the first embodiment.

[0023] Figure 3 This is a flowchart illustrating the process of calculating the movement of the examination bed in the medical image processing apparatus of the first embodiment.

[0024] Figure 4 This is a block diagram showing a simplified structure of the medical image processing apparatus according to the second embodiment.

[0025] Figure 5 This diagram illustrates an example of the relationship between radiation emission and the radiation target in a treatment system equipped with the medical image processing apparatus of the second embodiment.

[0026] Figure 6 This diagram illustrates another example of the relationship between radiation emission and the object irradiated by radiation in a treatment system equipped with the medical image processing apparatus of the second embodiment.

[0027] Figure 7 This is a block diagram illustrating a simplified structure of the medical image processing apparatus according to the third embodiment.

[0028] Figure 8 This is a block diagram illustrating a simplified structure of the medical image processing apparatus according to the fourth embodiment.

[0029] Figure 9 This is a diagram showing an example of a display screen displayed by a display device caused by the user interface section of the medical image processing apparatus of the fourth embodiment. Detailed Implementation

[0030] Hereinafter, the medical image processing apparatus, treatment system, medical image processing method, and program according to the embodiments will be described with reference to the accompanying drawings.

[0031] (First Embodiment)

[0032] Figure 1This is a block diagram illustrating a simplified structure of a treatment system equipped with the medical image processing apparatus of the first embodiment. The treatment system 1 includes, for example, a treatment device 10 and a medical image processing apparatus 100. The treatment device 10 includes, for example, an examination bed 12, an examination bed control unit 14, a computed tomography (CT) device 16 (hereinafter referred to as "CT imaging device 16"), and a treatment beam irradiation gate 18.

[0033] The examination table 12 is a movable treatment table in which the patient (P) receiving radiation therapy is fixed in a lying position, for example, by means of a fixation device. The examination table 12, with the patient P fixed in place, moves into a ring-shaped CT imaging device 16 having an opening, under the control of the examination table control unit 14. The examination table control unit 14 controls the lateral movement mechanism and the rotation mechanism provided on the examination table 12 to change the direction of the irradiation treatment beam B to the patient P fixed on the examination table 12, based on the movement amount signal output from the medical image processing device 100. The lateral movement mechanism can drive the examination table 12 in three-axis directions, and the rotation mechanism can drive the examination table 12 around the three axes. Therefore, the examination table control unit 14 controls, for example, the lateral movement mechanism and the rotation mechanism of the examination table 12 to move the examination table 12 in six degrees of freedom. The degrees of freedom controlled by the examination table control unit 14 can also be less than six degrees of freedom (e.g., four degrees of freedom) or more than six degrees of freedom (e.g., eight degrees of freedom).

[0034] The CT imaging device 16 is an imaging device for performing three-dimensional computed tomography (CT) imaging. The CT imaging device 16 has multiple radiation sources arranged inside a circular opening, from which radiation is irradiated to visualize the body of patient P. That is, the CT imaging device 16 irradiates radiation from multiple locations around patient P. The radiation irradiated from each radiation source in the CT imaging device 16 is, for example, X-rays. The CT imaging device 16 detects the radiation irradiated from the corresponding radiation sources and reaching the body of patient P by means of multiple radiation detectors arranged inside the circular opening. The CT imaging device 16 generates a CT image of the body of patient P based on the energy of the radiation detected by each radiation detector. The CT image of patient P generated by the CT imaging device 16 is a three-dimensional digital image in which the energy of the radiation is represented by digital values. The CT imaging device 16 outputs the generated CT image to a medical image processing device 100. The three-dimensional imaging of the patient P in the CT imaging device 16, namely the irradiation of radiation from various radiation sources, and the generation of CT images based on radiation detected by various radiation detectors, are controlled, for example, by the imaging control unit (not shown).

[0035] The therapeutic beam irradiation gate 18 irradiates a therapeutic beam B, which is used to destroy the tumor (lesion) present in the body of patient P. The therapeutic beam B can be, for example, X-rays, gamma rays, electron beams, proton beams, neutron beams, heavy ion beams, etc. The therapeutic beam B is irradiated in a straight line from the therapeutic beam irradiation gate 18 to patient P (more specifically, the tumor within patient P's body). The irradiation of the therapeutic beam B in the therapeutic beam irradiation gate 18 is controlled, for example, by a therapeutic beam irradiation control unit (not shown). In the treatment system 1, the therapeutic beam irradiation gate 18 is an example of an "irradiation unit" in this disclosure.

[0036] In the treatment room equipped with treatment system 1, there are pre-set... Figure 1 The reference position is defined by three-dimensional coordinates. Furthermore, in the treatment room where the therapeutic beam B is irradiated onto patient P, the position of the irradiation gate 18, the direction of irradiation of the therapeutic beam B (irradiation direction), the position of the examination bed 12, the position of the CT imaging device 16, and the position for capturing CT images of patient P's body are determined based on the three-dimensional coordinates of the pre-set reference position. In the following description, the three-dimensional coordinate system of the pre-set reference position in the treatment room will be defined as the "room coordinate system." Furthermore, in the following description, "position" refers to the coordinates of the three axes (three dimensions) involved in the parallel mechanism of the examination bed 12, expressed according to the room coordinate system, and "posture" refers to the rotation angle around the three axes involved in the rotation mechanism of the examination bed 12, expressed according to the room coordinate system. For example, the position of the examination bed 12 refers to the position of a predetermined point contained within the examination bed 12 expressed in three-dimensional coordinates, and the posture of the examination bed 12 refers to the rotation angle of the examination bed 12 expressed in terms of yaw, tilt, and pitch.

[0037] In radiotherapy, a treatment plan is developed under conditions simulating a treatment room. That is, during radiotherapy, the direction and intensity of the treatment beam B are planned to be irradiated onto patient P, simulating the patient P being placed on the examination table 12 in the treatment room. Therefore, CT images at the treatment planning stage (treatment planning phase) are assigned parameters indicating the position and orientation of the examination table 12 within the treatment room. This is also true for CT images taken before radiotherapy and CT images taken during previous radiotherapy sessions. In other words, CT images obtained by the CT imaging device 16 within patient P's body are assigned parameters indicating the position and orientation of the examination table 12 during imaging.

[0038] exist Figure 1The diagram illustrates a treatment device 10 comprising a CT imaging unit 16 and a fixed treatment beam irradiation gate 18, but the configuration of the treatment device 10 is not limited to the above-described configuration. For example, the treatment device 10 may also be a CT imaging unit, cone-beam (CB) CT unit, magnetic resonance imaging (MRI) unit, ultrasound diagnostic unit, or other imaging device that generates three-dimensional images of the patient P's body, replacing the CT imaging unit 16 with a set of radiation sources and radiation detectors rotating inside an annular opening. For example, the treatment device 10 may also be configured with multiple treatment beam irradiation gates, such as a treatment beam irradiation gate that irradiates the treatment beam towards the patient P from a horizontal direction. For example, the treatment device 10 may be... Figure 1 A therapeutic beam irradiation gate 18 is shown relative to Figure 1 The configuration shown involves rotating the horizontal axis X by 360 degrees, thereby irradiating the patient P from various directions by rotating around the periphery of the patient P. For example, the treatment device 10 can be an alternative to the CT imaging device 16, comprising one or more imaging devices consisting of a radiation source and a radiation detector, and the imaging device is used to irradiate the patient P from various directions. Figure 1 The horizontal axis X is rotated 360 degrees to capture images of the patient P's internal structure from various directions. Such a configuration is called a rotating gantry-type treatment device. In this case, for example, it could be... Figure 1 The diagram shows a configuration in which a therapeutic beam irradiation gate 18 and an imaging device rotate simultaneously on the same axis of rotation.

[0039] The medical image processing apparatus 100 performs processing to align the position of patient P during radiotherapy based on CT images output by the CT imaging apparatus 16. More specifically, the medical image processing apparatus 100 performs processing to align the position of tumors and tissues present in patient P based on CT images of patient P taken before radiotherapy, such as during the treatment planning stage, and current CT images of patient P taken by the CT imaging apparatus 16 during the treatment stage (treatment stage) of radiotherapy. Furthermore, the medical image processing apparatus 100 outputs a movement amount signal to the examination bed control unit 14 to align the irradiation direction of the treatment beam B irradiated from the treatment beam irradiation gate 18 with the direction set in the treatment planning stage. That is, the medical image processing apparatus 100 outputs a movement amount signal to the examination bed control unit 14 to move patient P in the direction in which the treatment beam B is properly irradiated during radiotherapy.

[0040] The medical image processing device 100 and the treatment device 10 can be connected via wired connection to the examination bed control unit 14 and CT imaging device 16, or via wireless connection such as LAN (Local Area Network) or WAN (Wide Area Network).

[0041] The medical image processing apparatus 100 of the first embodiment will be described below. Figure 2 This is a block diagram showing a simplified structure of the medical image processing apparatus 100 according to the first embodiment. The medical image processing apparatus 100 includes, for example, a first image acquisition unit 102, a second image acquisition unit 104, a direction acquisition unit 106, and a motion calculation unit 120. The motion calculation unit 120 includes, for example, an approximate image calculation unit 122 and a registration unit 124.

[0042] Some or all of the components of the medical image processing device 100 can be implemented by executing programs (software) through hardware processors such as CPUs (Central Processing Units). Some or all of these components can be implemented by hardware (circuit unit; including circuitry) such as LSIs (Large Scale Integration), ASICs (Application Specific Integrated Circuits), FPGAs (Field-Programmable Gate Arrays), and GPUs (Graphics Processing Units), or through the cooperation of software and hardware. Some or all of the functions of these components can also be implemented by dedicated LSIs. The program can be pre-stored in storage devices such as ROMs (Read Only Memory), RAMs (Random Access Memory), HDDs (Hard Disk Drives), and flash memory (storage devices with non-transitory storage media) of the medical image processing device 100, or it can be stored in removable storage media such as DVDs and CD-ROMs (non-transitory storage media) and installed in the HDDs and flash memory of the medical image processing device 100 by placing the storage media into the drive device of the medical image processing device 100. The program can also be downloaded from other computer devices via the network and installed on the HDD or flash memory of the medical image processing device 100.

[0043] The first image acquisition unit 102 acquires a first image related to the patient P before treatment, and parameters representing the position and posture at the time the first image was captured. The first image is a three-dimensional CT image representing the three-dimensional shape of the patient P's body, captured, for example, by the CT imaging device 16 during the treatment planning stage of radiotherapy. The first image is used to determine the direction (including path such as tilt and distance) and intensity of the treatment beam B irradiated to the patient P during radiotherapy. The determined direction (irradiation direction) and intensity of the treatment beam B are set for the first image. The first image is captured while the position and posture (hereinafter referred to as "position") of the patient P are maintained constant by fixing it to the examination table 12. The parameters representing the position of the patient P when the first image was captured can be the position and posture (imaging direction, magnification) of the CT imaging device 16 when the first image was captured, for example, the position and posture of the examination table 12 when the first image was captured, i.e., the setting values ​​set for the parallel mechanism and rotation mechanism provided on the examination table 12 to maintain the patient P's position constant. The first image acquisition unit 102 outputs the acquired first image and parameters to the motion calculation unit 120. The first image can be any image taken before radiotherapy, such as an image taken in the treatment room just before treatment or an image taken during a previous radiotherapy. The first image acquisition unit 102 may have an interface for connecting to the CT imaging device 16 of the treatment device 10.

[0044] The second image acquisition unit 104 acquires a second image relating to the patient P before the start of radiotherapy, and parameters representing the position and posture at the time the second image was taken. The second image is a three-dimensional CT image representing the three-dimensional shape of the patient P's body, captured, for example, by the CT imaging device 16 to align the patient P's body position during radiotherapy irradiation with the treatment beam B. That is, the second image is captured by the CT imaging device 16 in a state where the treatment beam B is not being irradiated from the treatment beam irradiation gate 18. In other words, the second image is a CT image captured at a time different from the time the first image was captured. In this case, although the first and second images were captured at different times, the methods used to capture each image are the same. Therefore, the second image is captured in a position close to the same as when the first image was captured. The parameters indicating the patient P's position when the second image was captured can be the position and orientation (shooting direction, magnification) of the CT scanner 16 when the second image was captured. For example, it can be the position and orientation of the examination table 12 when the second image was captured, i.e., the settings set for the parallel and rotating mechanisms provided on the examination table 12 to make the patient P's position close to the same position as when the first image was captured. The second image acquisition unit 104 outputs the acquired second image and parameters to the movement calculation unit 120. The second image acquisition unit 104 may have an interface for connecting to the CT scanner 16 provided in the treatment device 10. This interface may be an interface shared with the interface provided in the first image acquisition unit 102.

[0045] The second image is not limited to a CT image captured by the CT imaging device 16. For example, it can also be a three-dimensional image captured by an imaging device different from the CT imaging device 16, such as a CBCT device, an MRI device, or an ultrasound diagnostic device. For example, the first image can be a CT image, and the second image can be a three-dimensional image captured by an MRI device. Conversely, the first image can be a three-dimensional image captured by an MRI device, and the second image can be a CT image.

[0046] The direction acquisition unit 106 acquires information related to the direction within the treatment room (hereinafter referred to as "direction information"). The direction information is represented by a pre-set room coordinate system. The direction information includes, for example, information indicating the irradiation direction of the treatment beam B and information indicating the movement direction of the examination bed 12.

[0047] The information indicating the irradiation direction of the therapeutic beam B indicates the direction in which the therapeutic beam B is irradiated from the therapeutic beam irradiation door 18 in the treatment room towards the patient P. Although the treatment device 10 sometimes also... Figure 1The diagram shows a configuration where the treatment beam irradiation gate 18 is fixed. However, as described above, configurations that allow the treatment beam B to be irradiated from both vertical and horizontal directions, or configurations where the treatment beam irradiation gate 18 can rotate simultaneously with the imaging device around the same axis of rotation to irradiate the treatment beam B from various directions, are also possible. Furthermore, sometimes the treatment beam B is irradiated onto the area (range) of a tumor present in the patient P's body using a scanning (raster scanning) radiation beam or by irradiating a planar area of ​​a predetermined size. That is, regarding the irradiation direction of the treatment beam B, there may sometimes be multiple paths through which the tumor in the patient P's body is actually irradiated. In these cases, the direction acquisition unit 106 acquires all irradiation directions (including multiple paths) within the treatment chamber that allow the treatment beam B to be irradiated as information indicating the irradiation direction of the treatment beam B.

[0048] The information indicating the direction of movement of the examination bed 12 is information indicating the direction in which the patient P, who is fixed during the irradiation of the treatment beam B, can be moved by the examination bed 12 located in the treatment room. The information indicating the direction of movement of the examination bed 12 also includes information indicating the angle at which the patient P's position can be changed by the examination bed 12. For example, as described above, the examination bed 12 can be moved in position and posture with six degrees of freedom via a lateral movement mechanism and a rotation mechanism. Therefore, the information indicating the direction of movement of the examination bed 12 can also be information indicating the direction of the six degrees of freedom within the examination bed 12. The information indicating the direction of movement of the examination bed 12 can also be information indicating the range of set values ​​that can be set for the lateral movement mechanism and the rotation mechanism. As described above, when the examination bed 12 moves with fewer degrees of freedom than six (e.g., four degrees of freedom), the direction acquisition unit 106 acquires information corresponding to the degree of freedom of movement of the examination bed 12. It is also possible that the movement of the examination bed 12 is based on a unique coordinate system different from the room coordinate system pre-set in the treatment room. In this case, the direction acquisition unit 106 can acquire information about the direction of movement in the unique coordinate system on which the examination bed 12 is based, as information representing the direction of movement of the examination bed 12.

[0049] The direction acquisition unit 106 outputs information indicating the irradiation direction of the acquired treatment beam B and information indicating the movement direction of the examination bed 12 as direction information to the movement calculation unit 120.

[0050] The movement calculation unit 120 determines the amount of movement of the examination bed 12 to align the position of patient P as shown in the second image output by the second image acquisition unit 104 with the position of patient P as shown in the first image, based on the first image output by the first image acquisition unit 102 and the direction information output by the direction acquisition unit 106. Thus, the movement calculation unit 120 determines the amount of movement of the examination bed 12 to align the current position of patient P with the position of patient P in the treatment planning phase, in a manner that the energy imparted to the tumor in patient P by the irradiated treatment beam B is close to the energy planned in the treatment planning phase. The movement calculation unit 120 outputs a movement amount signal SM, representing the determined movement amount of the examination bed 12, to the examination bed control unit 14 included in the treatment device 10. The examination bed control unit 14 then moves the examination bed 12 according to the movement amount signal SM output by the movement calculation unit 120, so that the current position of patient P is close to the position of patient P in the treatment planning phase.

[0051] The approximate image calculation unit 122 calculates an approximate image that has slightly shifted the first image based on the first image output by the first image acquisition unit 102, parameters representing the position and orientation of the first image, and direction information output by the direction acquisition unit 106. More specifically, the approximate image calculation unit 122 first independently calculates the image that has slightly shifted the first image in the room coordinate space for one or more coordinate axes represented by the direction information. For example, it calculates six images that have been shifted by a predetermined amount in each of the six degrees of freedom of movement of the examination bed. Next, it calculates six difference images between these six images and the image before the shift, and calculates an approximate image obtained by multiplying each difference image by the reciprocal of the predetermined amount. The approximate image calculation unit 122 outputs the calculated approximate image to the registration unit 124. The approximate image calculation unit 122 calculates an approximate image for the moved first image based on information indicating that there is an offset between the first image and the second image that has been moved according to the amount of movement output by the registration unit 124 (or information about the offset between the first image and the second image). The calculated approximate image is then output to the registration unit 124 again.

[0052] The registration unit 124 calculates the position and posture offset between the first image and the second image based on the approximate image output by the approximate image calculation unit 122, the second image output by the second image acquisition unit 104, and parameters representing the position and posture of the second image. When the approximate image calculation unit 122 calculates an approximate image generated by moving a predetermined amount in each direction (degree of freedom) according to the change in the patient P's position as shown in the first image, the registration unit 124 calculates the position and posture offset between the first image and the second image in each direction. Based on the calculated offset, the registration unit 124 determines the amount of movement of the examination bed 12 to align the current position of the patient P shown in the second image with the position of the patient P in the treatment planning stage shown in the first image, and outputs a movement amount signal SM representing the determined amount of movement of the examination bed 12 to the examination bed control unit 14.

[0053] In the movement calculation unit 120, the calculation of the approximate image involved in the approximate image calculation unit 122, the calculation of the offset involved in the registration unit 124, and the determination of the movement amount of the examination bed 12 are repeatedly performed until it is determined that the current position of the patient P is consistent with the position of the patient P in the treatment plan stage. This determination is performed by the registration unit 124. This determination can also be performed by a determination unit (not shown) included in the movement calculation unit 120. In the movement calculation unit 120, when the registration unit 124 determines that the current position of the patient P is consistent with the position of the patient P in the treatment plan stage, a movement amount signal SM representing the determined final movement amount of the examination bed 12 (including tilt, distance, etc.) is output to the examination bed control unit 14. As a result, the examination bed control unit 14 controls the parallel mechanism and the rotation mechanism to move the examination bed 12 according to the movement amount signal SM output by the movement calculation unit 120, and the position of the patient P fixed on the examination bed 12 is actually moved. Thus, in the treatment system 1 equipped with the medical image processing device 100, the current position of the patient P can be aligned with the state in which the therapeutic beam B with energy planned in the treatment planning stage can be irradiated into the tumor in the patient P's body to perform radiotherapy.

[0054] The following describes the process in the medical image processing device 100 for determining the amount of movement (movement amount calculation process) of the examination bed 12 to be moved so that the current position of patient P is aligned with the position of patient P in the treatment planning stage. Figure 3This is a flowchart illustrating the process of calculating the movement of the examination bed 12 in the medical image processing apparatus 100 of the first embodiment. Before the medical image processing apparatus 100 performs the movement calculation, i.e., before radiotherapy (for example, about one week prior), a treatment plan is formulated based on a first image. Furthermore, just before the medical image processing apparatus 100 is about to perform the movement calculation, i.e., just before radiotherapy begins, a second image is captured. In radiotherapy, to treat the same patient P, irradiation with the treatment beam B is sometimes performed multiple times (including on different days). Therefore, when the radiotherapy for the same patient P is for the second or subsequent treatments, the second image, after the patient P's position was aligned during the previous treatment, can be used as the first image to further formulate other treatment plans.

[0055] Since this invention primarily focuses on the process of aligning the patient P's position during radiotherapy in the treatment system 1, more detailed descriptions related to the processing of capturing the individual images (here, CT images) of the first and second images are omitted. Furthermore, in the following description, it is stated that the treatment plan based on the first image has been completed and the capture of the second image in the treatment system 1 has been completed.

[0056] First, if the medical image processing device 100 starts motion calculation processing, the first image acquisition unit 102 acquires a first image and parameters indicating the position and orientation of the first image, and then acquires a second image and parameters indicating the position and orientation of the second image (step S100). The first image acquisition unit 102 outputs the acquired first image and its parameters to the approximate image calculation unit 122 included in the motion calculation unit 120. The second image acquisition unit 104 outputs the acquired second image and its parameters to the registration unit 124.

[0057] Next, the direction acquisition unit 106 acquires the direction information within the treatment room (step S102). The direction acquisition unit 106 outputs the acquired direction information to the approximate image calculation unit 122 of the movement calculation unit 120.

[0058] Next, the approximate image calculation unit 122 calculates an approximate image of the first image based on the first image output by the first image acquisition unit 102 and the direction information output by the direction acquisition unit 106, which represents the position and pose of the first image (step S104). The approximate image calculation unit 122 outputs the calculated approximate image to the registration unit 124.

[0059] Next, the registration unit 124 calculates the position and pose offset between the first image and the second image based on the approximate image output by the approximate image calculation unit 122, the second image output by the second image acquisition unit 104, and the parameters of the second image (step S106).

[0060] Next, the registration unit 124 determines whether the calculated offsets in position and pose between the first and second images are within an offset that would allow for the determination that there is no offset between the first and second images (step S108). In other words, the registration unit 124 determines whether the current position of patient P is consistent with the position of patient P in the treatment planning stage. Consistency between the current position of patient P and the position of patient P in the treatment planning stage means, for example, that the calculated offset between the first and second images is within a predetermined threshold representing an allowable range of offset.

[0061] If the determination in step S108 indicates that there is an offset between the first image and the second image, the registration unit 124 outputs information indicating that there is an offset between the calculated first image and the second image to the approximate image calculation unit 122. As a result, the motion calculation processing in the medical image processing apparatus 100 returns to step S104, and the processing in steps S104 to S108 is repeated. That is, in the motion calculation processing of the medical image processing apparatus 100, the calculation of the approximate image of the first image by the approximate image calculation unit 122, the calculation of the offset between the first image and the second image by the registration unit 124, and the determination of the calculated offset are repeatedly performed.

[0062] On the other hand, if the determination in step S108 results in the determination that there is no offset between the first image and the second image, the registration unit 124 determines the amount of movement of the examination bed 12 based on the calculated offset between the first image and the second image. Furthermore, the registration unit 124 outputs a movement amount signal SM, representing the determined amount of movement of the examination bed 12, to the examination bed control unit 14 (step S110).

[0063] Thus, in the treatment system 1, the examination bed control unit 14 moves the examination bed 12 based on the movement signal SM output by the medical image processing device 100 (more specifically, the registration unit 124 provided by the movement calculation unit 120), and the position of the patient P is actually moved.

[0064] Next, an example of a processing (processing method) performed on the constituent elements of the medical image processing apparatus 100 during the motion calculation processing of the medical image processing apparatus 100 will be described.

[0065] First, the treatment plan performed before the motion calculation processing in the medical image processing device 100 will be explained. The treatment plan determines the energy, direction, shape of the irradiation area, and dose distribution if the treatment beam B is irradiated multiple times to the patient P. More specifically, the treatment planner (doctor, etc.) first specifies the boundaries between the tumor (lesion) and normal tissue areas, and the boundaries between the tumor and surrounding vital organs, based on the first image taken during the treatment planning stage (e.g., a CT image taken by the CT imaging device 16). Furthermore, the treatment plan determines the direction (pathway of the treatment beam B), intensity, etc., of the irradiation treatment beam B based on the depth from the patient P's body surface to the tumor location and the size of the tumor, calculated according to the tumor-related information specified by the treatment planner (doctor, etc.).

[0066] The designation of the boundary between the tumor region and the normal tissue region is equivalent to designating the location and volume of the tumor. The volume of the tumor is referred to as the Gross Tumor Volume (GTV), Clinical Target Volume (CTV), Internal Target Volume (ITV), Planning Target Volume (PTV), etc. GTV is the volume of the tumor that can be visually confirmed from an image, and is the volume of the treatment beam B that requires a sufficient radiation dose during radiotherapy. CTV is the volume that includes GTV and the potential tumor to be treated. ITV is the volume to which a predetermined margin (extra volume) is added to CTV, taking into account the movement of the predicted physiological patient P, etc. PTV is the volume to which an extra volume is added to ITV, taking into account the error in the alignment of patient P during treatment. In these volumes, the following relationship (1) holds.

[0067] Formula 1

[0068]

[0069] On the other hand, the volume of a vital organ located around a tumor that is highly sensitive to radiation and whose radiation dose has a strong effect is called an organ at risk (OAR). The planned organ at risk volume (PRV) is designated as the volume of radiation to which a predetermined allowance (surplus) is added. The PRV is designated as the volume (area) to which radiation is to be avoided by the OAR that the patient does not want to be damaged by radiation. The following relationship exists among these volumes: (2).

[0070] Formula 2

[0071]

[0072] During the treatment planning phase, the direction (path) and intensity of the treatment beam B (radiation) irradiated to patient P are determined based on a margin of error that may occur in actual treatment.

[0073] Then, during the radiotherapy treatment phase, when the medical image processing device 100 performs motion calculation processing, firstly, the first image acquisition unit 102 acquires a first image and parameters indicating the position and posture of the first image, and outputs it to the approximate image calculation unit 122 included in the motion calculation unit 120. The second image acquisition unit 104 acquires a second image of the patient P before treatment begins, and parameters indicating the position and posture of the second image, and outputs it to the registration unit 124 included in the motion calculation unit 120. The direction acquisition unit 106 acquires direction information within the treatment room and outputs it to the approximate image calculation unit 122 included in the motion calculation unit 120.

[0074] As described above, both the first and second images are three-dimensional CT images. Furthermore, when taking the second image, the patient P's position was positioned approximately the same as when the first image was taken. However, it is difficult to capture the second image with the patient P in the exact same position as when the first image was taken. That is, it is difficult to suppress changes in the patient P's internal state, and even with fixation devices, it is difficult to maintain the same position. Therefore, even if the first and second images are hypothetically configured identically within a specified three-dimensional space, a slight (e.g., a few millimeters) shift occurs, making it difficult to reproduce the patient P's position as when the first image was taken solely by capturing the second image. Therefore, in the medical image processing apparatus 100, during the motion calculation process, the approximate image calculation unit 122 of the motion calculation unit 120 calculates an approximate image of the first image, and the registration unit 124 calculates the position and posture offset between the first image and the second image, to determine the amount of movement of the examination bed 12 used to align the position of the patient P projected in the first image with the position of the patient P projected in the second image. That is, the medical image processing apparatus 100 determines the amount of movement of the examination bed 12 used to reproduce the position of the patient P when the first image was captured through motion calculation processing. The defined three-dimensional space refers to the space of the room coordinate system pre-set in the treatment room.

[0075] (Method for calculating movement)

[0076] Next, the calculation method for the amount of movement that causes the examination bed 12 to move will be explained in the movement calculation processing of the medical image processing apparatus 100. First, the calculation method for the approximate image in the approximate image calculation unit 122 of the movement calculation unit 120 will be explained.

[0077] In the following description, the pixels (voxels) included in the first image, which will be virtually configured in a three-dimensional space according to the room coordinate system, will be denoted as Ii(V). In pixel Ii(V), equation (3) represents the three-dimensional position in the room coordinate system, and V represents the vector of position and pose when the first image is configured in the specified three-dimensional space. Vector V is a vector with the same number of axes as the direction information output from the direction acquisition unit 106, for example, a six-dimensional vector in the case of the above six degrees of freedom.

[0078]

Formula 3

[0079]

[0080] Vector V can also be a vector with fewer dimensions, corresponding to the directions of the degrees of freedom when controlling the movement of the examination bed 12 as described above. For example, if the directions of the degrees of freedom controlling the movement of the examination bed 12 are four degrees of freedom, vector V can be a four-dimensional vector. On the other hand, vector V can also increase its dimension by adding the irradiation direction of the treatment beam B to the movement direction of the examination bed 12 based on the direction information output by the direction acquisition unit 106. For example, if the irradiation direction of the treatment beam B included in the direction information is the vertical and horizontal directions, and the movement direction of the examination bed 12 is a six-degree-of-freedom direction, vector V can be a vector with a total of eight dimensions.

[0081] The approximate image calculation unit 122 calculates an approximate image that has been moved (and rotated) by a small amount of displacement ΔV. Here, the displacement ΔV is a small amount of displacement that is preset as a parameter. The approximate image calculation unit 122 calculates (approximately) each pixel Ii(V+ΔV) in the approximate image corresponding to each pixel Ii(V) in the first image using the following formula (4) and Taylor expansion.

[0082]

Formula 4

[0083]

[0084] In equation (4) above, the ε of the third term on the right is a term that uniformly represents the second degree of the pixel Ii(V+ΔV). ▽i(V) is the value of the first derivative of the vector that changes with respect to each degree of freedom of the three-dimensional space stretched by vector V. ▽i(V) is represented by a vector of the same dimension as the vector V representing the change in the pixel value (e.g., CT value) of the corresponding pixel, located at the same position i in the room coordinate system in the first image before movement (approximately before) and the approximate image after slight movement. For example, in the case where the direction of movement of the examination bed 12 is a six-degree-of-freedom direction, the six-dimensional vector ▽i(V) corresponding to the pixel Ii(V) located at the center i of the room coordinate system in the first image is represented by equation (5).

[0085]

Formula 5

[0086]

[0087] In equation (5) above, Δθx, Δθy, and Δθz represent rotation angles centered on each axis when the three axes in the room coordinate system are set as the x-axis, y-axis, and z-axis, and Δtx, Δty, and Δtz represent the amount of movement along each axis. The elements on the right side of equation (5) above represent the pixel value at position i in the room coordinate system of the first image. For example, the first element "equation (6)" on the right side of equation (5) above is the pixel value when pixel Ii (V) of the first image at position i in the room coordinate system is rotated around the x-axis by a rotation angle Δθx. Equation (7) in this case is represented by equation (8) below. The other elements on the right side of equation (5) above can also be represented in the same way, but detailed explanations related to each element are omitted.

[0088]

Formula 6

[0089]

[0090]

Formula 7

[0091]

[0092]

Form 8

[0093]

[0094] The approximate image calculation unit 122 outputs an approximate image to the registration unit 124 after calculating a small displacement ΔV that moves (advances and rotates) the first image as described above. When the registration unit 124 outputs information indicating an offset between the first and second images, the approximate image calculation unit 122 similarly calculates a new approximate image that further moves (advances and rotates) the first image by a small displacement ΔV, and outputs the calculated new approximate image to the registration unit 124.

[0095] Next, the calculation method of the registration unit 124 of the motion calculation unit 120 calculating the position and posture offset of the first image and the second image in the motion calculation processing of the medical image processing device 100 will be described.

[0096] Here, if the registration unit 124 wants to obtain the offset of position and orientation between the first image and the second image as a movement amount ΔV, then the offset can be obtained using the following formula (9). The following formula (9) is an example of a formula for obtaining the offset (movement amount ΔV) based on the idea (algorithm) of the optimization method of the Lucas-Kanade method (LK method).

[0097]

Form 9

[0098]

[0099] In equation (9) above, Ω is the set of positions i of pixels Ii (V) encompassing the entire region where the first and second images overlap in the room coordinate system. The set Ω can also be a set of positions representing clinically meaningful spatial regions when the treatment beam B is irradiated onto the tumor area, as specified by the treatment planner (doctor, etc.). Alternatively, the set Ω can be a set of positions representing spatial regions (spheres, cubes, histograms) of a predetermined size centered on the beam irradiation position in the room coordinate system. The predetermined size is set based on the size of the patient P or the average human body size. Alternatively, the set Ω can be a set of positions extending the range of the PTV and GTV by a predetermined scale.

[0100] The registration unit 124 uses the cost function E(ΔV, Ω) on the right side of equation (9) above to compare the first image with the second image. The cost function E(ΔV, Ω) is represented by equation (10) below.

[0101]

Formula 10

[0102]

[0103] In equation (10) above, Ti(V) represents the pixel value (e.g., CT value) of each pixel in the second image of vector V at position i in the room coordinate system.

[0104] The cost function E(ΔV, Ω) used by the registration unit 124 to compare the first image with the second image can also be a cost function set in two unconnected spaces, as expressed by the following formula (11).

[0105]

Formula 11

[0106]

[0107] The cost function E(ΔV, Ω) used by the registration unit 124 to compare the first image with the second image can also be a cost function expressed as shown in equation (13) below, using a function formula (12) that specifies the weights corresponding to the position i in the room coordinate system.

[0108]

Formula 12

[0109]

[0110]

Formula 13

[0111]

[0112] In function expression (12), w(i) is a function that returns a value corresponding to the path of position i and the irradiated therapeutic beam B. For example, function w(i) might return a value of 2, such as "1" if position i is on the path traversed by the therapeutic beam B, and "0" if it is not. Function w(i) could also be a function that returns a higher value the closer the distance between position i and the path traversed by the therapeutic beam B.

[0113] The function w(i) could, for example, return a value corresponding to the set of locations representing clinically significant spatial regions when the treatment beam B (PTV, GTV, OAR, etc.) is irradiated onto the tumor area, as specified by the treatment planner (doctor, etc.). The function w(i) could also be a function that returns a value of 2, such as "1" if location i is part of the set of locations representing spatial regions, and "0" if location i is not part of the set. Furthermore, the function w(i) could be a function that returns a higher value the closer the location i is to the spatial region.

[0114] Based on the approximate image output by the approximate image calculation unit 122, the above equation (9) can be rewritten as in the following equation (14).

[0115]

Formula 14

[0116]

[0117] In the above equation (14), the ε of the third term on the right side of the above equation (4) for the representation pixel Ii(V+ΔV) of the approximate image output by the approximate image calculation unit 122 is ignored. This is because since the ε, which is uniformly expressed after the second time in the above equation (4), is a very small value, even if it is ignored, it will not have a significant impact on subsequent processing.

[0118] If the right side of the above equation (14) is differentiated into 0 by the movement ΔV in order to find the minimum value of the movement ΔV, then the movement ΔV is represented by the following equation (15).

[0119]

Formula 15

[0120]

[0121] Here, H on the right side of the above equation (15) is the same as in the below equation (16).

[0122]

Formula 16

[0123]

[0124] The registration unit 124 uses the movement amount ΔV obtained by the above equation (15) to update the vector V of the position and pose of the first image as shown in the following equation (17).

[0125]

Formula 17

[0126]

[0127] In the above equation (17), the vector V of the updated position and pose of the first image is taken as vector V1.

[0128] The registration unit 124 repeatedly calculates the movement amount ΔV involved in the above equation (15) until the change in vector V1 of the updated first image becomes less. The change in vector V1 becomes less when the norm of the movement amount ΔV, i.e., the offset between the position and posture of the first and second images, becomes below a predetermined threshold. In other words, it is determined that the position of patient P reflected in the second image is consistent with the position of patient P in the treatment planning stage reflected in the first image. The norm of the movement amount ΔV can be any vector norm, such as any one of the l0 norm, l1 norm, or l2 norm.

[0129] In the case where the set Ω is a region of PTV and GTV as described above, if the position and pose of the first image are updated, the elements of the set Ω also need to be updated. That is, this is because the set Ω is a set of coordinate positions in the room coordinate system, and its position changes as the first image moves within the room coordinate system. To avoid such updates, it is desirable that the first image, in which the position and pose are updated, does not contain the region of the defined set Ω. For example, the CT image taken before the treatment (the previous second image) can be replaced with the first image, and the CT image including treatment plan information (the previous first image) can be replaced with the second image.

[0130] The registration unit 124 can repeatedly calculate the movement amount ΔV until a preset number of repetitions is exceeded. In this case, the time required for the registration unit 124 to calculate the movement amount ΔV can be shortened. However, in this case, the registration unit 124 ends the calculation of the movement amount ΔV at the moment when the preset number of repetitions is exceeded, but the norm of the movement amount ΔV may not be below a predetermined threshold. In other words, it can be considered that the possibility of the alignment calculation of patient P failing is high. In this case, the registration unit 124 may output a warning signal indicating that the calculation of the movement amount ΔV has ended, for example, to a warning unit (not shown) provided by the medical image processing device 100 or the treatment system 1, because the preset number of repetitions has been exceeded. Thus, the warning unit (not shown) can notify the doctor or other practitioner of radiotherapy, i.e., the user of the treatment system 1, of the possibility that the alignment calculation of patient P has failed.

[0131] The registration unit 124 calculates the movement amount ΔV, i.e., the position and posture offset between the first image and the second image, according to each degree of freedom in formula (5) above. Furthermore, the registration unit 124 determines the movement amount (parallel movement and rotation amount) of the examination bed 12 based on the calculated offsets for each degree of freedom. At this time, the registration unit 124, for example, sums the movement amount ΔV that was moved when calculating the approximate image based on the first image, according to each degree of freedom. Furthermore, the registration unit 124 determines the movement amount of the examination bed 12, which is the sum of the movement amounts that move the current patient P's position, according to each degree of freedom. Moreover, the registration unit 124 outputs a movement amount signal SM, representing the determined movement amount of the examination bed 12, to the examination bed control unit 14.

[0132] Through this processing, in the movement calculation processing of the medical image processing device 100, the approximate image calculation unit 122 calculates an approximate image based on the first image, and the registration unit 124 calculates the offset between the patient P's position in the treatment planning stage and the current patient P's position based on the approximate image and the second image. That is, in the movement calculation processing of the medical image processing device 100, the offset of the irradiation direction (path) of the treatment beam B is determined based on the approximate image and the second image. In the movement calculation processing of the medical image processing device 100, the calculation of the approximate image and the offset are repeatedly performed. Moreover, in the movement calculation processing of the medical image processing device 100, if the offset calculated between the approximate image and the second image is below a predetermined threshold, the movement amount of the examination bed 12 is determined based on the sum of the offsets calculated up to this point to align the current patient P's position with the patient P's position in the treatment planning stage, and the movement amount signal SM representing the determined movement amount of the examination bed 12 is output to the examination bed control unit 14. In other words, during the movement calculation processing of the medical image processing device 100, the movement amount of the examination bed 12 is determined to align the current position of patient P with the position of patient P in the treatment planning stage, in a manner that allows the treatment beam B, which provides energy close to that planned in the treatment planning stage, to be directed to the tumor within patient P's body. The movement amount signal SM is then output to the examination bed control unit 14. Thus, in the treatment system 1 equipped with the medical image processing device 100, patient P is actually moved according to the movement amount of the examination bed 12 determined by the movement calculation processing of the medical image processing device 100, enabling the tumor to be irradiated with the treatment beam B, which provides the energy planned in the treatment plan, and allowing radiation therapy to be performed as planned.

[0133] As described above, in the motion calculation processing of the medical image processing device 100, the approximate image calculation unit 122 calculates an approximate image by moving (and rotating) the first image by a small amount of motion ΔV based on the vector corresponding to the degree of freedom of the examination bed control unit 14 in controlling the movement direction of the examination bed 12 (refer to the above formula (5)). Furthermore, in the motion calculation processing of the medical image processing device 100, the registration unit 124 calculates the position and orientation offset between the approximate image and the second image. Therefore, in the medical image processing device 100, compared to directly using the first and second images for patient P alignment as in the past, the alignment of patient P involving image comparison of three-dimensional CT images can be performed more quickly. Furthermore, since the approximate image used for comparison in the medical image processing device 100 is an image by moving the first image by a small amount of motion ΔV, the accuracy of patient P alignment becomes high, corresponding to the amount of motion ΔV.

[0134] In the motion calculation process of the medical image processing apparatus 100, when the calculation of the approximate image and the offset are repeatedly performed, a new approximate image that has moved (advanced and rotated) the first image is calculated. In other words, in the motion calculation process of the medical image processing apparatus 100, the approximate image is recreated through repeated calculations of the approximate image and the offset. Therefore, in the medical image processing apparatus 100 or the treatment system 1 equipped with the medical image processing apparatus 100, making the image size of the original image (here, the first image) used to calculate the approximate image smaller than the reference image (here, the second image) used to calculate the offset can reduce the load of the repeated approximate image calculation, that is, shorten the approximate image calculation time.

[0135] As described above, in the medical image processing apparatus 100, the first image acquisition unit 102 acquires a first image of the patient P taken before treatment, and parameters indicating the position and posture when the first image was taken. The second image acquisition unit 104 acquires a second image of the patient P taken just before treatment begins, and parameters indicating the position and posture when the second image was taken. In the medical image processing apparatus 100, the direction acquisition unit 106 acquires information related to the direction within the treatment room. Furthermore, in the medical image processing apparatus 100, the approximate image calculation unit 122, included in the motion calculation unit 120, calculates an approximate image that transforms (approximates) the first image based on the first image, the parameters indicating the position and posture of the first image, and the direction information. Additionally, in the medical image processing apparatus 100, the registration unit 124, included in the motion calculation unit 120, calculates the position and posture offset between the first image and the second image based on the approximate image, the second image, and the parameters indicating the position and posture of the second image. Furthermore, in the medical image processing apparatus 100, when the registration unit 124 determines that the calculated offset matches the current position of patient P reflected in the second image and the position of patient P in the treatment planning stage reflected in the first image, it determines the movement amount of the examination bed 12, i.e., the final movement amount of patient P, based on the calculated offset, and outputs a movement amount signal SM representing the determined movement amount of the examination bed 12 to the examination bed control unit 14. Thus, in the treatment system 1 equipped with the medical image processing apparatus 100, the examination bed 12 is moved by the examination bed control unit 14 based on the movement amount signal SM, thereby actually moving the position of patient P. Therefore, in the treatment system 1 equipped with the medical image processing apparatus 100, the current position of patient P can be aligned with a treatment beam B that can irradiate the tumor within patient P with an energy level close to that determined in the treatment planning stage, and radiation therapy can be performed according to plan.

[0136] As described above, the medical image processing apparatus 100 includes: a first image acquisition unit 102 that acquires a first image of three dimensions inside the body of patient P; a second image acquisition unit 104 that acquires a second image of three dimensions inside the body of patient P captured at a different time than the first image; a direction acquisition unit 106 that acquires direction information in the treatment room related to the irradiation direction of the treatment beam B directed toward patient P; and a movement amount calculation unit 120 that outputs a movement amount signal SM representing the movement amount of the second image that is moved to make the position of patient P reflected in the second image consistent with the position of patient P reflected in the first image, based on the path of the treatment beam B set for the first image and the direction information related to the irradiation direction. Therefore, the medical image processing device 100 can calculate the offset between the position of the patient P in the treatment planning stage and the current position of the patient P based on the first image acquired by the first image acquisition unit 102, the second image acquired by the second image acquisition unit 104, and the direction information acquired by the direction acquisition unit 106, and determine the amount of movement to align the current position of the patient P with the position when the first image was taken in the treatment planning stage.

[0137] As described above, the motion calculation unit 120 may include: an approximate image calculation unit 122, which calculates an approximate image generated (transformed (approximate)) by shifting the first image by a predetermined amount (e.g., a small amount of movement) for each degree of freedom according to the change in the patient P's position based on the path of the treatment beam B and directional information related to the irradiation direction; and a registration unit 124, which uses the approximate image to calculate the offset between the first image and the second image, determines the motion amount based on the calculated offset, and outputs a motion amount signal SM representing the determined motion amount. As described above, the motion calculation unit 120 may include: an approximate image calculation unit 122, which calculates a two-dimensional approximate image that maps the first image onto a plane based on the path of the treatment beam B and directional information related to the irradiation direction; and a registration unit 124, which uses the approximate image to calculate the offset between the first image and the second image, determines the motion amount based on the calculated offset, and outputs a motion amount signal SM representing the determined motion amount. Thus, the medical image processing device 100 can calculate an approximate image that approximates the first image, calculate the offset of the position and posture between the approximate image (in other words, the first image) and the second image, determine the amount of movement of the examination bed 12 to align the current position of the patient P reflected in the second image with the position of the patient P in the treatment planning stage reflected in the first image based on the calculated offset, and output a movement amount signal SM representing the determined amount of movement of the examination bed 12.

[0138] (Second Implementation)

[0139] The second embodiment will now be described. In the first embodiment, a method for calculating the movement of the examination table 12 was described, in which the images of the first and second images are virtually arranged in a defined three-dimensional space (room coordinate system), and the difference in pixel values ​​at the same spatial position i in each of the first and second images is reduced. However, in this calculation method, although the difference in pixel values ​​in each of the first and second images is reduced, it is not necessarily calculated to be consistent with the radiation dose distribution of the treatment beam B for the tumor specified by the person who formulates the treatment plan (doctor, etc.), which is important in radiotherapy. Since radiation (here, treatment beam B) loses energy when passing through matter, the irradiation method can be determined by calculating the amount of energy loss of the virtually irradiated radiation using CT images in the treatment plan. Considering this, when aligning the position of the patient P during the treatment phase, it is important that the tissues in the patient P's body present along the path of the irradiated treatment beam B are also consistent. In view of this, in the second embodiment, it is proposed to determine the composition and calculation method of the amount of movement of the examination bed 12 to align the current position of patient P with the position of patient P in the treatment planning stage, so that the energy imparted to the tumor in patient P's body by the irradiated treatment beam B is closer to the energy planned in the treatment planning stage.

[0140] The treatment system equipped with the medical image processing device of the second embodiment is configured in the following way: Figure 1 In the configuration of the treatment system 1 shown, which includes the medical image processing device 100 of the first embodiment, the medical image processing device 100 is replaced by the medical image processing device 200 of the second embodiment. In the following description, the treatment system including the medical image processing device 200 will be referred to as "treatment system 2".

[0141] In the following description, in the components of the treatment system 2 equipped with the medical image processing device 200, the same reference numerals are given to the components that are the same as those of the treatment system 1 equipped with the medical image processing device 100 of the first embodiment. Detailed descriptions related to each component are omitted, and the description focuses on the differences.

[0142] Similar to the medical image processing apparatus 100 of the first embodiment, the medical image processing apparatus 200 performs processing to align the position of the patient P during radiotherapy based on the CT image output by the CT imaging apparatus 16. It outputs a movement amount signal SM to the examination bed 12 to align the irradiation direction of the treatment beam B irradiated from the treatment beam irradiation gate 18 with the direction set in the treatment planning stage. In the medical image processing apparatus 200, compared to the medical image processing apparatus 100 of the first embodiment, it is possible to determine the amount of movement of the examination bed 12 such that the energy imparted to the tumor in the patient P by the irradiated treatment beam B is closer to the energy planned in the treatment planning stage.

[0143] The following describes the configuration of the medical image processing device 200 that constitutes the treatment system 2. Figure 4 This is a block diagram illustrating a simplified structure of the medical image processing apparatus 200 according to the second embodiment. The medical image processing apparatus 200 includes, for example, a first image acquisition unit 102, a second image acquisition unit 104, a direction acquisition unit 106, and a motion calculation unit 220. The motion calculation unit 220 includes, for example, an integral image calculation unit 221, an approximate image calculation unit 222, and a registration unit 124. The integral image calculation unit 221 includes, for example, a first integral image calculation unit 221-1 and a second integral image calculation unit 221-2.

[0144] The integral image calculation unit 221 calculates integral images corresponding to the first image output by the first image acquisition unit 102 (hereinafter referred to as the "first integral image") and integral images corresponding to the second image output by the second image acquisition unit 104 (hereinafter referred to as the "second integral image"). The integral image calculation unit 221 outputs the first integral image to the approximate image calculation unit 222 and outputs the second integral image to the registration unit 124. The integral image is an image in which pixel values ​​are integrated along the irradiation path of the therapeutic beam B within the image.

[0145] The first integral image calculation unit 221-1 calculates a first integral image based on the first image output by the first image acquisition unit 102, parameters representing the position and orientation of the first image, and direction information output by the direction acquisition unit 106, by integrating the pixel values ​​(CT values) of pixels (voxels) present along the path of the treatment beam B in the first image. The first integral image calculation unit 221-1 outputs the calculated first integral image to the approximate image calculation unit 222. At this time, the first integral image calculation unit 221-1 may also output the parameters representing the position and orientation of the first image together with the first integral image to the approximate image calculation unit 222.

[0146] The second integral image calculation unit 221-2 calculates a second integral image based on the second image output from the second image acquisition unit 104, parameters representing the position and orientation of the second image, and direction information output from the direction acquisition unit 106. This second integral image integrates the pixel values ​​(CT values) of pixels (voxels) present along the path of the treatment beam B within the second image. The second integral image calculation unit 221-2 outputs the calculated second integral image to the registration unit 124. At this time, the second integral image calculation unit 221-2 may also output the parameters representing the position and orientation of the second image along with the second integral image to the registration unit 124.

[0147] The approximate image calculation unit 222 calculates an approximate image that has been transformed (approximated) from the first integral image output by the first integral image calculation unit 221-1 of the integral image calculation unit 221. The approximate image calculation unit 222 outputs the calculated approximate image to the registration unit 124. The method for calculating the approximate image in the approximate image calculation unit 222 can be considered in the same way as the method for calculating the approximate image in the approximate image calculation unit 122 of the motion calculation unit 120 in the medical image processing apparatus 100 of the first embodiment.

[0148] Here, taking the first integral image calculation unit 221-1, which calculates the first integral image corresponding to the first image, as an example, we will explain the general outline of the integral image calculation method involved in the integral image calculation unit 221. In the calculation of the first integral image involved in the first integral image calculation unit 221-1, pixels located on the path through which the treatment beam B passes are first extracted from the pixels contained in the first image output by the first image acquisition unit 102. For the path through which the treatment beam B passes, the three-dimensional coordinates of the path through which the treatment beam B irradiates from the treatment beam irradiation gate 18 passes through the patient P can be obtained as room coordinates based on the irradiation direction of the treatment beam B contained in the direction information output by the direction acquisition unit 106. The path through which the treatment beam B passes can also be obtained as a three-dimensional vector with the position of the treatment beam irradiation gate 18, represented by the three-dimensional coordinates of the room coordinate system, as the starting point.

[0149] The irradiation direction of the therapeutic beam B irradiated from the therapeutic beam irradiation gate 18 will be explained below. In the following explanation, the path of the therapeutic beam B is assumed to be a three-dimensional vector. Figure 5 This is a diagram illustrating an example of the relationship between the emission of radiation (therapeutic beam B) in the treatment system 2 of the medical image processing apparatus 200 of the second embodiment and the irradiated target TG (a tumor present in the body of patient P). Figure 5The diagram shows an example of the path from the therapeutic beam B irradiated by the therapeutic beam irradiation gate 18 to the area (range) of the tumor present in the body of the patient P who is the irradiation target TG. Figure 5 This is an example of a configuration in which a therapeutic beam B is emitted from a therapeutic beam irradiation gate 18.

[0150] In the case where the treatment beam irradiation gate 18 emits the treatment beam B, the treatment beam irradiation gate 18 is as follows: Figure 5 As shown, it has a planar exit port. The treatment beam B emitted from the treatment beam irradiation gate 18 reaches the tumor of the irradiated target TG via the collimator 18-1. That is, only the treatment beam B' of the treatment beam B emitted from the treatment beam irradiation gate 18 that passes through the collimator 18-1 reaches the tumor of the irradiated target TG. The collimator 18-1 is a metal device used to cut off unnecessary treatment beam B'. For the collimator 18-1, in order to prevent the treatment beam B from irradiating areas other than the tumor existing in the patient P's body, the area through which the treatment beam B passes is adjusted, for example, according to the shape of the tumor of the irradiated target TG. The collimator 18-1 can be, for example, a multi-leaf collimator that can mechanically change the area where unnecessary treatment beam B' is cut off. Figure 5 The diagram schematically illustrates an example of irradiating a tumor of the target TG within the first image FI with a treatment beam B' passing through collimator 18-1. In this case, the starting point in the path of the treatment beam B' is the position of the exit point of the treatment beam B' located within the planar exit area of ​​the treatment beam irradiation gate 18. The three-dimensional position of the treatment beam irradiation gate 18 is, for example, the position (coordinates) of the center of the plane of the exit area.

[0151] The direction acquisition unit 106 outputs direction information, including the irradiation direction of the treatment beam B', as information representing the irradiation direction of the treatment beam B to the first integral image calculation unit 221-1. The first integral image calculation unit 221-1 takes the path of the treatment beam B' until it reaches the tumor of the irradiated object TG within the first image FI as the path of the treatment beam B' irradiating into the defined three-dimensional space. Here, the position i in the room coordinate system represents the position of the tumor of the irradiated object TG, and the path b(i) of the treatment beam B' reaching that position can be discretely represented by a set of three-dimensional vectors as shown in the following equation (18).

[0152]

Formula 18

[0153]

[0154] The starting point of each path, i.e., the starting point of the three-dimensional vector b(i), is the position of the exit point of the treatment beam B' from which each path b(i) reaches the tumor of the irradiated target TG. The three-dimensional position of this starting point is represented by S. In addition, Ω is defined in the same way as in the above equation (9) in the first embodiment, and is the set of the tumor positions of the irradiated target TG, i.e., the positions of PTV and GTV in the room coordinate system.

[0155] Figure 6 This is a diagram illustrating another example of the relationship between the emission of radiation (therapeutic beam B) in the treatment system 2 of the medical image processing apparatus 200 of the second embodiment and the irradiated target TG (a tumor present in the body of patient P). Figure 6 The diagram also shows an example of the path from the therapeutic beam B irradiated by the therapeutic beam irradiation gate 18 to the area (range) of the tumor present in the body of the patient P who is the irradiation target TG. Figure 6 This is an example of a configuration where the treatment beam irradiation gate 18 is used to scan the emitted treatment beam B. In this configuration, the treatment beam irradiation gate 18... Figure 6 As shown, it does not have a collimator 18-1 and has a firing port. The treatment beam B emitted from one firing port of the treatment beam irradiation gate 18 is irradiated to the tumor of the irradiation target TG by, for example, being bent in a direction by a magnet or the like, thereby scanning in a way that fills (scans) the entire area of ​​the tumor of the irradiation target TG. Figure 6 The diagram illustrates an example of a case where the irradiation direction of the therapeutic beam B is scanned to irradiate the tumor of the irradiated object TG within the first image FI. In this case, the starting point of each path of the scanned therapeutic beam B is the position of the exit point of the therapeutic beam irradiation gate 18. The three-dimensional position of the therapeutic beam irradiation gate 18 is the position (coordinates) of an exit point. In this case, the path b(i) of the therapeutic beam B to a position i in the room coordinate system can be discretely represented in the same way as in equation (18) above.

[0156] The direction acquisition unit 106 outputs direction information, including the irradiation direction of the scanned treatment beam B, as information representing the irradiation direction of the treatment beam B, to the first integral image calculation unit 221-1. The first integral image calculation unit 221-1 takes the path b(i) from the scanned treatment beam B to the coordinate i in the room coordinate system representing the position of the tumor of the irradiated object TG in the first image FI as the path of the treatment beam B irradiating into the specified three-dimensional space. In this case, the path of the treatment beam B can also be discretely represented by a set of three-dimensional vectors as in the above equation (18). The starting point of each path, that is, the starting point of the three-dimensional vector b(i), is the position of the exit point of the treatment beam irradiation gate 18.

[0157] (Methods for generating integral images)

[0158] Next, the method by which the integral image calculation unit 221 calculates each integral image will be described. In the following description, the position i of a certain point in a defined three-dimensional space (room coordinate system) is denoted as point i. Furthermore, the pixel value of the three-dimensional pixel corresponding to point i contained in the first image, which is virtually arranged in the defined three-dimensional space, is denoted as Ii(V). Similarly, the pixel value of the three-dimensional pixel corresponding to point i contained in the second image, which is virtually arranged in the defined three-dimensional space, is denoted as Ti(V). The pixel value is "0" if there is no pixel corresponding to point i in the first or second image. V is a parameter of the vector V representing the position and orientation of the first or second image in the defined three-dimensional space.

[0159] The vector of the therapeutic beam B from the position of the exit point of the therapeutic beam irradiation gate 18, i.e. the starting point S, to the point i can be represented by the following equation (19).

[0160]

Formula 19

[0161]

[0162] In this case, the first integral image calculation unit 221-1 can calculate the pixel value (hereinafter referred to as "integrated pixel value") of the pixels contained in the first integral image by accumulating the pixel values ​​of each pixel located on the path of the treatment beam B up to point i in the first image using the following formula (21).

[0163]

Formula 20

[0164]

[0165]

Formula 21

[0166]

[0167] Similarly, the second integral image calculation unit 221-2 can calculate the integral pixel value formula (22) of the pixels contained in the second integral image, which is obtained by accumulating the pixel values ​​of each pixel located on the path of the treatment beam B up to point i in the second image, by the following formula (23).

[0168]

Formula 22

[0169]

[0170]

Formula 23

[0171]

[0172] In equations (21) and (23) above, t is the mediating variable, and f(x) is a function that transforms the pixel values ​​(CT values) of the CT image. The function f(x) is, for example, a function that follows a transformation table to convert the energy loss of radiation into the equivalent thickness of water. As mentioned above, radiation loses energy when passing through matter. The amount of energy lost by radiation is the same as the energy corresponding to the CT value of the CT image. That is, the energy loss of radiation is not uniform, but varies depending on the tissues in patient P's body, such as bone and fat. The equivalent thickness of water is a value that represents the thickness of the same substance (water) for each tissue (matter), and can be converted based on the CT value. For example, when the CT value represents the value of bone, the equivalent thickness of water is large because radiation loses more energy when passing through bone. For example, when the CT value represents the value of fat, the equivalent thickness of water is small because radiation loses less energy when passing through fat. For example, when CT values ​​represent air values, the equivalent thickness of water is "0" because radiation loses little energy when passing through air. By transforming the individual CT values ​​contained in a CT image into equivalent water thicknesses, the energy loss involved in each pixel along the path of the therapeutic beam B can be represented on the same basis. As a transformation formula for converting CT values ​​into equivalent water thicknesses, a regression formula based on experimentally derived nonlinear conversion data can be used. Various publications have documented experimentally derived nonlinear conversion data. The function f(x) can also be, for example, a function used for identity mapping.

[0173] The first integral image calculation unit 221-1 outputs the first integral image, which corresponds to the integral pixel value formula (20) of the first image, to the registration unit 124. The second integral image calculation unit 221-2 outputs the second integral image, which corresponds to the integral pixel value formula (22) of the second image, to the registration unit 124.

[0174] Therefore, the registration unit 124 uses the cost function E(ΔV, Ω) represented by the following formula (24), which is based on the same idea as the above formula (10) shown in the first embodiment, to calculate the offset of position and posture between the first image and the second image, that is, the amount of movement ΔV.

[0175]

Formula 24

[0176]

[0177] Furthermore, the registration unit 124 determines the movement amount (parallel movement and rotation amount) of the examination bed 12 based on the movement amount ΔV calculated using the cost function E(ΔV, Ω) of the above formula (24), and outputs the movement amount signal SM, which represents the determined movement amount of the examination bed 12, to the examination bed control unit 14.

[0178] The motion calculation and processing in the medical image processing device 200 only needs to be performed in Figure 3 The motion calculation processing of the medical image processing apparatus 100 of the first embodiment shown can be supplemented with the processing involving the integral image calculation unit 221. More specifically, in Figure 3 In the motion calculation process of the medical image processing apparatus 100 of the first embodiment shown, it is sufficient to add the process of calculating each integral image in the integral image calculation unit 221 before step S104. Therefore, detailed descriptions related to the motion calculation process in the medical image processing apparatus 200 are omitted.

[0179] Based on this configuration and operation, the medical image processing device 200 calculates a first integral image based on a first image and a second integral image based on a second image during the motion calculation processing. Furthermore, similarly to the medical image processing device 100 of the first embodiment, the approximate image calculation unit 222 calculates an approximate image based on the first integral image, and the registration unit 124 calculates the offset of the irradiation direction (path) of the treatment beam B, i.e., the offset between the patient P's position during the treatment planning stage and the current patient P's position, based on the approximate image and the second integral image. In the motion calculation processing of the medical image processing device 200, similarly to the motion calculation processing of the medical image processing device 100 of the first embodiment, the calculation of the approximate image and the offset are repeatedly performed. The amount of motion to move the examination bed 12 is determined based on the offset when the offset between the approximate image and the second integral image becomes below a predetermined threshold, and a motion signal SM representing the determined amount of motion of the examination bed 12 is output to the examination bed control unit 14. Therefore, in the treatment system 2 equipped with the medical image processing device 200, similarly to the treatment system 1 equipped with the medical image processing device 100 of the first embodiment, the patient P is actually moved according to the amount of movement of the examination bed 12 determined by the movement amount calculation and processing of the medical image processing device 200, so that the therapeutic beam B with the energy amount planned in the treatment plan can be irradiated to the tumor, and radiation therapy can be performed as planned.

[0180] Furthermore, in the medical image processing apparatus 200, the integral image calculation unit 221 calculates the first integral image corresponding to the first image and the second integral image corresponding to the second image using a predetermined nonlinear transformation (nonlinear conversion data obtained through experiments). Therefore, in the medical image processing apparatus 200, the amount of movement of the examination bed 12 can be determined so that the radiation dose distribution of the treatment beam B relative to the tumor, which is a concern in the medical image processing apparatus 100 of the first embodiment, is also consistent. That is, in the medical image processing apparatus 200, the amount of movement of the examination bed 12 can be determined in a state where the tissues within the patient P, which are important in radiotherapy and exist along the path of the treatment beam B irradiating the tumor, are also consistent.

[0181] In the medical image processing apparatus 200, the approximate image used for offset calculation in the motion calculation process is based on the first integral image. Therefore, when the registration unit 124 calculates the approximate image and offset (i.e., the motion ΔV) and updates the vector V1 of the first integral image, the first integral image calculation unit 221-1 also needs to calculate (reconstruct) a new first integral image along with the calculation (reconstruction) of the new approximate image. That is, the first integral image calculation unit 221-1 needs to recalculate the first integral image by integrating the pixel values ​​(CT values) of the pixels (voxels) present on the new path through which the treatment beam B passes in the first image. For example, if the movement direction of the examination table 12 is a six-degree-of-freedom direction, the first integral image calculation unit 221-1 needs to recalculate the first integral image of the six paths corresponding to each degree of freedom in the six-dimensional vector ▽i(V) represented by the above equation (5). That is, the first integral image calculation unit 221-1 performs the calculation of the first integral image 6 times again. The recalculation of the first integral image in the first integral image calculation unit 221-1 can be considered a significant factor increasing the computation time. Therefore, in the medical image processing apparatus 200, after calculating the offset and aligning the patient P using the cost function E(ΔV, Ω) shown in equation (10), equation (11), or equation (13) above in the first embodiment, the cost function E(ΔV, Ω) shown in equation (24) above can be used to calculate the offset and align the patient P. Thus, in the medical image processing apparatus 200, when the approximate image calculation and offset calculation are repeatedly performed in the motion calculation processing, the number of times the first integral image needs to be recalculated can be reduced. The overall computation time required for the motion calculation processing is shortened.

[0182] As described above, in the medical image processing apparatus 200, similar to the medical image processing apparatus 100 of the first embodiment, the first image acquisition unit 102 acquires a first image of the patient P taken before treatment, and parameters indicating the position and posture at the time the first image was taken; the second image acquisition unit 104 acquires a second image of the patient P taken just before treatment begins, and parameters indicating the position and posture at the time the second image was taken. Furthermore, in the medical image processing apparatus 200, the direction acquisition unit 106 also acquires information related to the direction within the treatment room. Moreover, in the medical image processing apparatus 200, the integral image calculation unit 221 of the movement calculation unit 220 calculates integral images corresponding to both the first and second images, and the approximate image calculation unit 222 calculates an approximate image that has been transformed (approximated) from the first image based on the first integral image. Then, in the medical image processing apparatus 200, similarly to the medical image processing apparatus 100 of the first embodiment, the registration unit 124 calculates the position and posture offsets of the first and second images based on the approximate image and the second integral image corresponding to the second image. Based on the calculated offsets, it determines the movement amount of the examination bed 12, i.e., the final movement amount of the patient P, and outputs a movement amount signal SM representing the determined movement amount of the examination bed 12 to the examination bed control unit 14. Thus, in the treatment system 2 equipped with the medical image processing apparatus 200, similarly to the treatment system 1 equipped with the medical image processing apparatus 100 of the first embodiment, the examination bed control unit 14 actually moves the position of the patient P by moving the examination bed 12 based on the movement amount signal SM. Therefore, in the treatment system 2 equipped with the medical image processing device 200, similarly to the treatment system 1 equipped with the medical image processing device 100 of the first embodiment, the current position of the patient P is aligned with a state in which a therapeutic beam B with an energy level close to that determined in the treatment planning stage is irradiated into the tumor within the patient P's body, enabling radiotherapy to be performed as planned. Furthermore, in the treatment system 2 equipped with the medical image processing device 200, since the amount of movement of the examination table 12 can be determined while ensuring that the tissues within the patient P's body that are present along the path of the therapeutic beam B irradiating the tumor are also consistent, compared to the treatment system 1 equipped with the medical image processing device 100 of the first embodiment, it is possible to irradiate the tumor within the patient P's body with a therapeutic beam B with an energy level closer to that determined in the treatment planning stage for radiotherapy.

[0183] As described above, in the medical image processing apparatus 200, the motion calculation unit 220 further includes an integral image calculation unit 221, which calculates a first integral image by integrating the pixel value (CT value) of a first pixel (voxel) in three dimensions that is contained in the first image and passes through the path of the treatment beam B, and a second integral image by integrating the pixel value (CT value) of a second pixel (voxel) in three dimensions that is contained in the second image and passes through the treatment beam B irradiated from the irradiation direction. The approximate image calculation unit 222 calculates an approximate image based on the first integral image, and the registration unit 124 outputs a motion signal SM based on the offset between the second integral image and the approximate image. Therefore, the medical image processing device 200 calculates the offset between the position of the patient P in the treatment planning stage and the current position of the patient P based on the first integrated image, which integrates the CT values ​​of the voxels contained in the first image, and the first integrated image, which integrates the CT values ​​of the voxels contained in the second image, and can determine the amount of movement used to align the current position of the patient P with the position when the first image was taken in the treatment planning stage.

[0184] As explained above, the integral image calculation unit 221 can also perform integration on the pixel values ​​(CT values) of the first pixel (voxel) located on the path of the treatment beam B and the pixel values ​​(CT values) of the second pixel (voxel) located on the path through which the treatment beam B irradiates from the irradiation direction passes, after transforming them respectively through a prescribed nonlinear transformation (nonlinear conversion data obtained experimentally), to calculate the first integral image and the second integral image respectively. Therefore, the medical image processing apparatus 200 can determine the amount of movement used to align the current position of the patient P with the position when the first image was captured during the treatment planning phase, based on the first integral image and the second integral image, which are obtained by integrating the CT values ​​of the voxels contained in the first image and the CT values ​​of the voxels contained in the second image through a regression transformation based on experimentally obtained nonlinear conversion data.

[0185] As explained above, the integral image calculation unit 221 can transform the pixel value (CT value) of the first pixel (voxel) located on the path of the treatment beam B and the pixel value (CT value) of the second pixel (voxel) located on the path through which the treatment beam B irradiates from the irradiation direction passes into values ​​representing the arrival energy (e.g., water equivalent thickness) of the treatment beam B reaching each pixel (voxel) through a nonlinear transformation (nonlinear conversion data obtained experimentally). Thus, the medical image processing apparatus 200 can determine the amount of movement used to align the current position of the patient P with the position when the first image was captured during the treatment planning phase, based on the first integral image and the second integral image, which integrate the CT values ​​of the voxels contained in the first image and the CT values ​​of the voxels contained in the second image, for example, after conversion to water equivalent thickness.

[0186] As explained above, the integral image calculation unit 221 can integrate the value of the energy loss (water equivalent thickness) obtained by transforming the pixel value (CT value) of the first pixel (voxel) on the path of the treatment beam B, which is located in the interval from the arrival of the treatment beam B to the region (tumor) of the irradiated target, and the pixel value (CT value) of the second pixel (voxel) on the path of the treatment beam B irradiated from the irradiation direction, which is located in the interval from the arrival of the irradiated target region (tumor). This allows the medical image processing apparatus 200 to reduce the amount of processing (computational load) required to generate the first integral image and the second integral image.

[0187] (Third implementation)

[0188] The third embodiment will now be described. In a radiotherapy treatment plan, as described above, the treatment planner (doctor, etc.) specifies the boundaries between the tumor (lesion) and normal tissue areas, and the boundaries between the tumor and surrounding vital organs, etc., based on the first image taken during the treatment planning phase (e.g., a CT image taken by the CT imaging device 16). That is, in the treatment plan, information such as the tumor location and OAR (Occurrence Area) is specified for each patient P to determine the direction, intensity, etc., of the treatment beam B to be irradiated. Specifying this information in the treatment plan requires a certain amount of time. Therefore, for the second image of patient P just before treatment begins, information such as the tumor location and OAR, as in the treatment planning phase, is generally not input. Therefore, in conventional radiotherapy, treatment is performed assuming that the location of the tumor in patient P before treatment begins is the same as in the treatment plan. Therefore, in conventional radiotherapy, it is difficult to address the temporal changes in the location of tumors that are highly likely to occur during treatment. In view of this, the following configuration and calculation method are proposed in the third embodiment: for the second image of the patient P before the start of treatment, the part of the image graphic similar to the tumor specified in the first image in the treatment plan is identified, thereby focusing on the local part where the tumor exists, so that the determination of the amount of movement of the examination bed 12 in order to align the current position of the patient P with the position of the patient P in the treatment plan stage corresponds to the time-varying position of the tumor.

[0189] The treatment system equipped with the medical image processing device of the third embodiment is configured to have... Figure 1 The medical image processing apparatus 100 of the first embodiment shown in the diagram is configured such that the medical image processing apparatus 100 is replaced by the medical image processing apparatus 300 of the third embodiment. In the following description, the treatment system equipped with the medical image processing apparatus 300 will be referred to as "treatment system 3".

[0190] In the following description, the same reference numerals are given to the constituent elements of the treatment system 3 equipped with the medical image processing device 300 that are the same as the constituent elements of the treatment system 1 equipped with the medical image processing device 100 of the first embodiment. Detailed descriptions related to each constituent element are omitted, and the description focuses on the differences.

[0191] Similar to the medical image processing apparatus 100 of the first embodiment, the medical image processing apparatus 300 performs processing based on the CT images output by the CT imaging apparatus 16 to align the position of the patient P during radiotherapy. It outputs a movement amount signal SM to the examination bed control unit 14 to align the irradiation direction of the treatment beam B irradiated from the treatment beam irradiation gate 18 with the direction set in the treatment planning phase. In the medical image processing apparatus 300, it is possible to focus on the local portion of the tumor within the patient P's body and determine the movement amount of the examination bed 12 such that the energy imparted to the tumor by the irradiated treatment beam B is close to the energy planned in the treatment planning phase.

[0192] The following describes the configuration of the medical image processing device 300 that constitutes the treatment system 3. Figure 7 This is a block diagram showing a simplified structure of the medical image processing apparatus 300 according to the third embodiment. The medical image processing apparatus 300 includes a first image acquisition unit 102, a second image acquisition unit 104, a direction acquisition unit 106, a region acquisition unit 308, and a motion calculation unit 320. The motion calculation unit 320 includes an approximate image calculation unit 122, a motion inference unit 323, and a registration unit 324.

[0193] The region acquisition unit 308 acquires information about the tumor-related region specified in the first image for patient P during the treatment planning phase. The region acquisition unit 308 acquires information such as the tumor location, PTV, OAR, etc., as tumor-related region information (hereinafter referred to as "region information"). The image used by the region acquisition unit 308 to acquire the region information is not limited to the first image; it can be any image whose tumor-related region was specified during the treatment planning phase, such as the second image or images inferred from previous radiotherapy images. The region acquisition unit 308 outputs the acquired region information to the motion calculation unit 320, and more specifically, to the motion inference unit 323.

[0194] The motion inference unit 323 copies regions such as tumors, PTVs, and OARs contained in the first image to the second image based on the first image output by the first image acquisition unit 102, the second image output by the second image acquisition unit 104, and the region information output by the region acquisition unit 308. The motion inference unit 323 generates a motion model that infers changes (motions) in the position of the tumor and other regions in the second image based on the regions copied to the second image. The motion inference unit 323 outputs the generated motion model to the registration unit 324.

[0195] The registration unit 324 calculates the position and posture offset between the first image and the second image, including the motion of the tumor, based on the approximate image of the first image output by the approximate image calculation unit 122, the second image output by the second image acquisition unit 104, and the motion model output by the motion inference unit 323. Based on the calculated offset, the registration unit 324 determines the amount of movement of the examination bed 12 to align the current position of the patient P shown in the second image with the position of the patient P in the treatment planning stage shown in the first image, and outputs a movement amount signal SM representing the determined amount of movement of the examination bed 12 to the examination bed control unit 14.

[0196] (Inference methods for motion models)

[0197] Next, the method by which the motion inference unit 323 infers the motion model will be explained. In the following explanation, a motion inference method will be described that infers the motion model for determining the location of a tumor in the second image based on a region related to the tumor specified in the first image represented by the region information output by the region acquisition unit 308.

[0198] In the motion model inference of the motion inference unit 323, the motion of a region in a second image that is similar to an image within the region of the tumor specified for the first image is determined. As a method, the motion inference unit 323 employs, for example, a template matching technique. More specifically, the motion inference unit 323 searches for the location of the most similar image as the location of the tumor in the second image by using an image representing the region of the tumor specified for the first image as a template and performing template matching on the second image. Furthermore, the motion inference unit 323 calculates the motion vector of the tumor location in the searched second image and uses all the calculated motion vectors as the motion model. The motion inference unit 323 can also segment the tumor region used as a template into multiple smaller regions (hereinafter referred to as "small regions"), using images representing each segmented small region as individual templates. In this case, the motion inference unit 323 performs template matching according to the templates of each small region, searching for the location of the most similar tumor in the second image according to each small region. Furthermore, the motion inference unit 323 calculates the motion vector of the tumor location in the second image corresponding to each searched small region and uses all the calculated motion vectors as the motion model. The motion inference unit 323 can use the average vector, median vector, etc. of the calculated motion vectors as motion models.

[0199] The motion inference unit 323 can also calculate the motion of a region in a second image that is similar to the distribution of pixel values ​​within the tumor region specified in the first image. As a method, the motion inference unit 323 can, for example, utilize techniques such as mean shift or center shift to track objects by searching for histogram-like positions of pixel values. In this case, the motion inference unit 323 generates a motion model using the distribution of histograms of pixel values ​​calculated using all pixel values ​​within the tumor region specified in the first image. The motion inference unit 323 can divide the tumor region specified in the first image into multiple smaller regions, and for each smaller region, generate a motion model corresponding to that smaller region using the distribution of histograms of pixel values ​​calculated using the pixel values ​​within that region. In this case, the motion inference unit 323 can group the multiple motion models corresponding to each smaller region into a motion model group, or it can use the average vector, median vector, etc., of the motion model group as the motion model.

[0200] The motion inference unit 323 outputs the motion model generated in this way to the registration unit 324.

[0201] Therefore, the registration unit 324 includes the movement of the tumor within the scope of the calculation of the position and pose offset between the first image and the second image as described above. At this time, the registration unit 324 uses the cost function E(ΔV, Ω) represented by the following formula (25) to include the movement of the tumor within the scope of the calculation of the position and pose offset between the first image and the second image, that is, the movement amount ΔV.

[0202]

Formula 25

[0203]

[0204] In equation (25) above, Ω is the set of locations within the region associated with the tumor specified for the first image, acquired by the region acquisition unit 308. Equation (26) is a function of the transformed location of the region associated with the tumor specified for the first image through a motion model. In the case where the motion model is, for example, a motion model modeled as the average vector of all motion vectors of the tumor location in the second image, the function equation (26) represents the parallel movement of the tumor location.

[0205]

Formula 26

[0206]

[0207] Furthermore, the registration unit 324 determines the movement amount (parallel movement and rotation amount) of the examination bed 12 based on the movement amount ΔV calculated using the cost function E(ΔV, Ω) of the above formula (25), and outputs the movement amount signal SM, which represents the determined movement amount of the examination bed 12, to the examination bed control unit 14.

[0208] The motion calculation and processing in the medical image processing device 300 only needs to be performed in Figure 3 The motion calculation processing of the medical image processing apparatus 100 of the first embodiment shown can be performed by adding the processing involved in the region acquisition unit 308 and the processing involved in the motion inference unit 323. More specifically, in Figure 3 In the motion calculation process of the medical image processing apparatus 100 of the first embodiment shown, it is sufficient to add, for example, a process after step S102 to obtain region information of a tumor specified in the first image in the region acquisition unit 308, and a process before step S106 to infer the motion of the tumor position in the second image and generate a motion model by inferring motion such as the position of the tumor in the second image in the motion inference unit 323. Therefore, a detailed description of the motion calculation process in the medical image processing apparatus 300 is omitted.

[0209] Through this configuration and operation, the medical image processing apparatus 300 obtains region information of the tumor specified in the first image during motion calculation processing. Based on the obtained region information, it copies the tumor region to the second image to generate a motion model that infers the changes (motions) in the position of the tumor in the second image. Furthermore, in the medical image processing apparatus 300, similar to the medical image processing apparatus 100 of the first embodiment, the approximate image calculation unit 122 calculates an approximate image based on the first image. Then, the registration unit 324 calculates the position and posture offset between the first and second images, including the tumor's movement, based on the approximate image, the second image, and the motion model; that is, the offset between the patient P's position during the treatment planning stage and the current patient P's position. In the motion calculation processing of the medical image processing device 300, similar to the motion calculation processing of the medical image processing device 100 in the first embodiment, the calculation of the approximate image and the calculation of the offset are repeatedly performed. Based on the offset when the offset between the approximate image and the second image becomes below a predetermined threshold, the motion amount of the examination bed 12 is determined, and the motion amount signal SM representing the determined motion amount of the examination bed 12 is output to the examination bed control unit 14. Thus, in the treatment system 3 equipped with the medical image processing device 300, similar to the treatment system 1 equipped with the medical image processing device 100 in the first embodiment, the patient P is actually moved according to the motion amount of the examination bed 12 determined by the motion calculation processing of the medical image processing device 300, and the therapeutic beam B with the planned energy amount in the treatment plan can be irradiated to the tumor, so that radiotherapy can be performed as planned.

[0210] Furthermore, in the medical image processing apparatus 300, by configuring the region acquisition unit 308, the motion inference unit 323, and the registration unit 324, focus is placed on the local portion where the tumor exists as specified in the first image of patient P during the treatment planning phase, including the movement of the tumor, and calculating the offset between the current position of patient P and the position of patient P during the treatment planning phase. Thus, in the medical image processing apparatus 300, alignment of patient P corresponding to temporal changes in the location of tumors that are highly likely to occur during radiotherapy treatment is possible.

[0211] As described above, in the medical image processing apparatus 300, similar to the medical image processing apparatus 100 of the first embodiment, the first image acquisition unit 102 acquires a first image of the patient P taken before treatment, and parameters indicating the position and posture at the time the first image was taken. The second image acquisition unit 104 acquires a second image of the patient P taken just before treatment begins, and parameters indicating the position and posture at the time the second image was taken. Furthermore, in the medical image processing apparatus 300, the direction acquisition unit 106 also acquires information related to the direction within the treatment room. Moreover, in the medical image processing apparatus 300, the approximate image calculation unit 122, included in the movement calculation unit 320, also calculates an approximate image that transforms (approximates) the first image. Furthermore, in the medical image processing apparatus 300, the region acquisition unit 308 acquires region information related to the tumor region specified in the first image for patient P during the treatment planning stage, and the motion inference unit 323 of the motion calculation unit 320 generates a motion model that infers the changes (motions) of the tumor position, etc., in the second image. Then, in the medical image processing apparatus 300, the registration unit 324 of the motion calculation unit 320 calculates the position and posture offset between the first image and the second image based on the approximate image, the second image, and the motion model, including the tumor movement. Based on the calculated offset, the motion amount of the examination bed 12, i.e., the final motion amount of patient P, is determined, and the motion amount signal SM representing the determined motion amount of the examination bed 12 is output to the examination bed control unit 14. Thus, in the treatment system 3 equipped with the medical image processing apparatus 300, similarly to the treatment system 1 equipped with the medical image processing apparatus 100 of the first embodiment, the position of patient P is actually moved by moving the examination bed 12 based on the motion amount signal SM by the examination bed control unit 14. Therefore, in the treatment system 3 equipped with the medical image processing device 300, similarly to the treatment system 1 equipped with the medical image processing device 100 of the first embodiment, the current position of the patient P can be aligned with a treatment beam B that can irradiate the tumor in the patient P's body with an energy level close to that determined in the treatment planning stage, so as to perform radiotherapy according to plan. Furthermore, in the treatment system 3 equipped with the medical image processing device 300, since the movement of the examination bed 12 can be determined internally, including the movement of the tumor in the patient P's body, compared with the treatment system 1 equipped with the medical image processing device 100 of the first embodiment, a treatment beam B with an energy level closer to that determined in the treatment planning stage can be irradiated into the tumor in the patient P's body for radiotherapy.

[0212] In the medical image processing device 300, the following is shown: Figure 2The medical image processing apparatus 100 of the first embodiment shown has been modified by adding or replacing components related to the inference of tumor movement. More specifically, in the medical image processing apparatus 300, a configuration is shown in which a region acquisition unit 308 is added to the medical image processing apparatus 100 of the first embodiment, a motion inference unit 323 is added to the motion calculation unit 120 of the medical image processing apparatus 100, and a registration unit 324 is replaced by a registration unit 324. For Figure 4 The configuration of the medical image processing apparatus 200 of the second embodiment shown can also be modified in the same way to change the constituent elements related to the inference of tumor movement. In this case, the configuration, operation, processing, and calculation method only need to be configured to be equivalent to the configuration, operation, processing, and calculation method of the medical image processing apparatus 300 described above. Therefore, detailed descriptions related to the configuration, operation, processing, and calculation method for making the medical image processing apparatus 200 of the second embodiment capable of inferring tumor movement are omitted.

[0213] As described above, in the medical image processing apparatus 300, the region acquisition unit 308 acquires region information related to the tumor region specified in the first image for the patient P during the treatment planning stage, and the motion inference unit 323 of the motion calculation unit 320 generates a motion model that infers the changes (motions) of the tumor's position, etc., in the second image. Then, in the medical image processing apparatus 300, the registration unit 324 of the motion calculation unit 320 calculates the position and posture offset between the first and second images, including the tumor's motion, based on the approximate image, the second image, and the motion model. Based on the calculated offset, it determines the movement of the examination bed 12, i.e., the final movement of the patient P, and outputs a movement amount signal SM representing the determined movement of the examination bed 12 to the examination bed control unit 14. Thus, in the treatment system 3 equipped with the medical image processing apparatus 300, similarly to the treatment system 1 equipped with the medical image processing apparatus 100 of the first embodiment, the position of the patient P is actually moved by moving the examination bed 12 based on the movement amount signal SM by the examination bed control unit 14. Therefore, in the treatment system 3 equipped with the medical image processing device 300, similarly to the treatment system 1 equipped with the medical image processing device 100 of the first embodiment, the current position of the patient P can be aligned with the state of the treatment beam B, which can irradiate the tumor in the patient P's body with an energy level close to that determined in the treatment planning stage, so as to perform radiotherapy according to plan. Furthermore, in the treatment system 3 equipped with the medical image processing device 300, since the movement of the tumor in the patient P's body can be included in determining the amount of movement of the examination bed 12, compared with the treatment system 1 equipped with the medical image processing device 100 of the first embodiment, the treatment beam B with an energy level closer to that determined in the treatment planning stage can be irradiated into the tumor in the patient P's body to perform radiotherapy.

[0214] As described above, the medical image processing apparatus 300 further includes a region acquisition unit 308 that acquires region information related to the region of the tumor within the patient P's body based on information about the treatment plan for the patient P. The motion calculation unit 320 also includes a motion inference unit 323 that infers the movement of the tumor based on the first image, the second image, and the region information. The registration unit 324 outputs a motion signal SM based on the offset, including the tumor movement inferred by the motion inference unit 323. Thus, the medical image processing apparatus 300 calculates the offset between the patient P's position during the treatment planning stage and the current position of the patient P, based on the first image, the second image, orientation information, and region information, including changes (movement) in the tumor. It can then determine the motion amount used to align the current position of the patient P with the position when the first image was captured during the treatment planning stage.

[0215] As explained above, regional information may include at least the region of the tumor (lesion) and the region of the organ at risk (OAR) surrounding the tumor (lesion).

[0216] (Fourth implementation)

[0217] The fourth embodiment will now be described. It is also possible that after the alignment of patient P is performed using the medical image processing apparatus of the first to third embodiments, the practitioner of radiotherapy, i.e., the doctor using the treatment system, confirms the alignment result and further fine-tunes the position and posture of patient P. Therefore, in the fourth embodiment, the confirmation of the alignment result of patient P performed using the medical image processing apparatus, the configuration for fine-tuning, and the position and posture of patient P will be described. In the following description, ... Figure 2 The medical image processing apparatus 100 of the first embodiment shown is a representative example, and the configuration for confirming the alignment result of patient P and making fine adjustments will be described. In the following description, the medical image processing apparatus 100a of the fourth embodiment will be referred to as "medical image processing apparatus 100a", and the treatment system equipped with medical image processing apparatus 100a will be referred to as "treatment system 1a".

[0218] Figure 8 This is a block diagram illustrating a simplified structure of the medical image processing apparatus 100a according to the fourth embodiment. The medical image processing apparatus 100a includes, for example, a first image acquisition unit 102, a second image acquisition unit 104, a direction acquisition unit 106, a motion calculation unit 120, and a user interface unit 130. The motion calculation unit 120 includes, for example, an approximate image calculation unit 122 and a registration unit 124. The medical image processing apparatus 100a is a configuration of the medical image processing apparatus 100a of the first embodiment with the addition of the user interface unit 130.

[0219] The second image acquisition unit 104 outputs the acquired second image to the user interface unit 130. The approximate image calculation unit 122, which is included in the motion calculation unit 120, outputs the calculated approximate image to the user interface unit 130. Alternatively, or on this basis, the first image acquisition unit 102 outputs the acquired first image to the user interface unit 130.

[0220] The user interface unit 130 includes: a display device for displaying the alignment result of patient P to the user (doctor, etc.) of the treatment system 1a equipped with the medical image processing device 100a; and an input device for accepting input from the user (hereinafter referred to as "user") for various operations. The display device included in the user interface unit 130 is, for example, a liquid crystal display (LCD). The user interface unit 130 generates, for example, an image that overlaps the approximate image output by the approximate image calculation unit 122 (or the first image output by the first image acquisition unit 102) with the second image output by the second image acquisition unit 104, and displays the generated image as the alignment result of patient P on the display device.

[0221] The user interface unit 130 includes input devices such as keyboards, pointers such as mice or styluses, and operating devices such as buttons or switches. The user interface unit 130 receives user input device operations, more specifically, fine-tuning of the patient P's position and posture, and outputs the information represented by the received operation to the registration unit 124 of the movement calculation unit 120. Operations received by the user interface unit 130 may include setting parameters for a specified area in three-dimensional space or setting parameters in a cost function. Operations received by the user interface unit 130 may also include setting the direction within the treatment room obtained by the direction acquisition unit 106. In this case, the user interface unit 130 outputs the information represented by the received operation to the direction acquisition unit 106.

[0222] The user interface unit 130 includes a pressure sensor as an input device and can be configured as a touch panel combined with a display device. In this case, the user interface unit 130 detects and accepts various touch operations (clicks or pats, etc.) performed by the user on the image displayed on the display device using the pressure sensor, and outputs the information represented by the accepted user input operation to the registration unit 124 (or the direction acquisition unit 106).

[0223] Here, the display of images and the input of operations in the user interface unit 130 will be explained. Since the approximate image (which may also be the first image) and the second image are three-dimensional images, they cannot be directly displayed by a two-dimensional display device. Therefore, the user interface unit 130 generates one or more cross-sectional images corresponding to each of the approximate image and the second image and displays them on the display device. At this time, the user interface unit 130 displays difference images of each cross-sectional image to facilitate visual comparison between the approximate image and the second image. The user interface unit 130 may also display color maps based on the magnitude of the differences between the various cross-sectional images. The user interface unit 130 may also overlay the outlines of PTV, PRV, etc. The user interface unit 130 may display the cost function value of each PTV and PRV as information. Thus, the user can confirm the various cross-sectional images of the approximate image and the second image displayed on the display device, determine the offset between the approximate image and the second image, and determine whether to fine-tune the position and posture of the patient P. If the user operates the input device to fine-tune the position and posture of patient P, the user interface unit 130 outputs information representing the adjustment value input through the input device to the registration unit 124. The registration unit 124 then outputs a movement amount signal SM reflecting the adjustment value input by the user interface unit 130 to the examination bed control unit 14. The examination bed control unit 14 moves the examination bed 12 according to the movement amount signal SM output by the registration unit 124, which is included in the movement amount calculation unit 120, so that the current position of patient P becomes the position fine-tuned by the user.

[0224] An example of an image displayed by the display device caused by the user interface section 130 will be described. Figure 9 This is a diagram showing an example of a display screen displayed by a display device via a user interface section 130 provided by the medical image processing apparatus 100a of the fourth embodiment. Figure 9 The image shown is an example of a screen IM of a display device where the user interface section 130 displays an image. Figure 9 In this method, the left and right sides of the image IM are displayed as images IML and IMR, showing the patient's position from different directions (e.g., left and right of the patient P). Image IML and IMR are images formed by overlaying cross-sectional images PI1 (an approximate image) and PI2 (a second image). The tumor F, viewed from the corresponding direction, is also overlaid in both images IML and IMR. Furthermore, the offset between the patient P's current position and the position during the treatment planning stage is emphasized in both images IML and IMR by coloring the areas where cross-sectional images PI1 and PI2 are offset (i.e., the offset areas of the patient P's body surface and the outline of the internal tissues).

[0225] By observing the images IML and IMR on the screen IM, the user can easily confirm the deviation between the patient P's current position and the position during the treatment plan. Furthermore, the user can visually confirm the deviation between the patient P's current position and the position during the treatment plan, and simultaneously fine-tune the patient P's position and posture using the input device, based on the images IML and IMR. At this time, the user interface unit 130 can generate new images that virtually reflect the user's fine-tuning operations onto the images IML and IMR, and sequentially update the currently displayed images IML and IMR. That is, the user interface unit 130 can sequentially display the results of the fine-tuning performed by the user. Thus, the user can perform fine-tuning operations while sequentially confirming how the offset areas of the emphasized (prominent) cross-sectional images PI1 and PI2 in the images IML and IMR are gradually eliminated through fine-tuning. Moreover, the user can perform radiation therapy by irradiating the tumor in the patient P's body with the treatment beam B when the offset areas of cross-sectional images PI1 and PI2 disappear or fall within an acceptable range.

[0226] The motion calculation and processing in the medical image processing device 100a differs from that in the user interface unit 130 in that it includes display and input. Figure 3 The motion calculation process is the same as that in the medical image processing apparatus 100 of the first embodiment shown. Therefore, detailed descriptions of the motion calculation process in the medical image processing apparatus 100a are omitted.

[0227] Through this configuration and operation, the medical image processing device 100a displays the alignment result of the patient P's position during the treatment planning phase and the current position of the patient P on the display device provided with the user interface 130, and provides prompts to the user (doctor, etc.) of the treatment system 1a equipped with the medical image processing device 100a. Thus, the user of the treatment system 1a equipped with the medical image processing device 100a can visually confirm the offset between the patient P's position during the treatment planning phase and the current position of the patient P, and determine whether to fine-tune the current position of the patient P. Furthermore, if the user determines that the patient P's position needs fine-tuning, they can visually confirm the offset of the patient P's position displayed on the display device while operating the input device constituting the user interface 130 to perform fine-tuning operations on the approximate image and the various cross-sectional images of the second image displayed on the display device. Moreover, the medical image processing device 100a outputs a final movement signal SM reflecting the adjustment value fine-tuned by the user to the examination bed control unit 14. Therefore, the examination bed control unit 14 moves the examination bed 12 according to the movement signal SM output by the medical image processing device 100a so that the current position of the patient P is the position fine-tuned by the user. That is, in the treatment system 1a equipped with the medical image processing device 100a, when the patient P's position is suitable for radiotherapy, the treatment beam B with the planned energy amount in the treatment plan can be irradiated to the tumor, and radiotherapy can be performed as planned.

[0228] As described above, in the medical image processing apparatus 100a of the fourth embodiment, similar to the medical image processing apparatus 100a of the first embodiment, a movement amount signal SM representing the movement amount of the examination bed 12 is output to the examination bed control unit 14. Furthermore, in the medical image processing apparatus 100a of the fourth embodiment, the user is prompted with the alignment result of the patient P, and the user is allowed to make fine adjustments to the position of the patient P. Moreover, in the medical image processing apparatus 100a of the fourth embodiment, a movement amount signal SM reflecting the fine adjustments input by the user is output to the examination bed control unit 14. Thus, in the treatment system 1a equipped with the medical image processing apparatus 100a, the examination bed 12 is moved by the examination bed control unit 14 based on the movement amount signal SM, thereby actually moving the position of the patient P to a position reflecting the fine adjustments made by the user. Thus, in the treatment system 1a equipped with the medical image processing device 100a, the current position of the patient P can be actually moved to a position desired by the user suitable for radiotherapy, so as to irradiate the tumor with the therapeutic beam B of the planned energy in the treatment plan, and perform radiotherapy as planned.

[0229] In the medical image processing device 100a, it is shown that... Figure 2The medical image processing apparatus 100 of the first embodiment shown includes a user interface section 130. However, the configuration is not limited to the medical image processing apparatus 100 of the first embodiment having the user interface section 130 installed; it could also be installed in the medical image processing apparatus 200 of the second embodiment or the medical image processing apparatus 300 of the third embodiment. Furthermore, the configuration is not limited to having the user interface section 130 as a component of the medical image processing apparatus; it could also be a configuration possessed by a treatment system, i.e., a configuration installed externally to the medical image processing apparatus. In such cases, the configuration, operation, processing, and calculation methods need only be configured to be equivalent to the configuration, operation, processing, and calculation methods of the medical image processing apparatus 100a described above. Therefore, detailed descriptions related to the configuration, operation, processing, and calculation methods of other medical image processing apparatuses with the user interface section 130, or treatment systems with medical image processing apparatuses, are omitted.

[0230] As described above, the medical image processing apparatus 100a also includes a user interface unit 130, which has a display device for displaying an image used to confirm the offset calculated by the registration unit 124. Thus, the medical image processing apparatus 100a can provide the user (doctor, etc.) of the treatment system 1a equipped with the medical image processing apparatus 100a with the result of the alignment between the position of the patient P during the treatment planning phase and the current position of the patient P.

[0231] As described above, in the medical image processing apparatus 100a, the user interface unit 130 further includes an input device that inputs an adjustment value for adjusting a movement amount set based on an image displayed on a display device. The registration unit 124 can output a movement amount signal SM that adjusts the movement amount based on the adjustment value input to the input device. Thus, the medical image processing apparatus 100a can output a movement amount signal SM that reflects the adjustment value input by the user (doctor, etc.) of the treatment system 1a equipped with the medical image processing apparatus 100a.

[0232] In the second, third, and fourth embodiments, the configuration of the medical image processing apparatus 100 of the first embodiment with the addition of the constituent elements characteristic of each embodiment has been described. However, the constituent elements characteristic of each embodiment are not exclusive and can coexist. For example, the integral image calculation unit 221 of the medical image processing apparatus 200 of the second embodiment, the region acquisition unit 308 and motion inference unit 323 of the medical image processing apparatus 300 of the third embodiment, and the user interface unit 130 of the medical image processing apparatus 100a of the fourth embodiment can be equipped in one medical image processing apparatus. In this case, by appropriately changing the other constituent elements of the medical image processing apparatus, the functions corresponding to each constituent element can be realized.

[0233] In each embodiment, the case where the original image used by the approximate image calculation unit 122 (or approximate image calculation unit 222) to calculate the approximate image is the first image (or the first integral image corresponding to the first image) has been described. In other words, the case where the reference image used by the registration unit 124 (or registration unit 324) to calculate the offset is the second image (or the second integral image corresponding to the second image) has been described. However, the original image used to calculate the approximate image and the reference image used to calculate the offset can be interchanged. That is, the approximate image calculation unit 122 (or approximate image calculation unit 222) can calculate an approximate image that moves (and rotates) the second image (or the second integral image corresponding to the second image), and the registration unit 124 (or registration unit 324) can calculate the offset using the first image (or the first integral image corresponding to the first image) as a reference. In this case, the configuration, operation, processing, and calculation methods of the medical image processing apparatus in each embodiment can be configured to be equivalent to the configuration, operation, processing, and calculation methods of the medical image processing apparatus 100 in each embodiment described above.

[0234] In each embodiment, the configuration of the medical image processing device and the treatment device 10 as separate devices has been described. However, it is not limited to the configuration of the medical image processing device and the treatment device 10 as separate devices; they may also be configured as a single unit.

[0235] As described above, for example, the medical image processing method executed by the medical image processing apparatus 100 is a medical image processing method in which a computer (processor, etc.) performs the following processing: acquiring a first three-dimensional image (e.g., a CT image) of the patient P's body, and acquiring a second three-dimensional image (e.g., a CT image) of the patient P's body taken at a different time than the first image; acquiring directional information in the treatment room related to the irradiation direction of the treatment beam B irradiated to the patient P; and, based on the path of the treatment beam B set for the first image and the directional information related to the irradiation direction, outputting a movement amount signal SM that represents the amount of movement of the second image that is moved to align the position of the patient P reflected in the second image with the position of the patient P reflected in the first image.

[0236] As described above, for example, the program executed by the medical image processing device 100 is a program that causes a computer (processor, etc.) to perform the following processing: acquiring a first three-dimensional image (e.g., a CT image) of the patient P's body, acquiring a second three-dimensional image (e.g., a CT image) of the patient P's body taken at a different time than the first image, acquiring directional information in the treatment room related to the irradiation direction of the treatment beam B irradiating the patient P, and outputting a movement amount signal SM representing the amount of movement of the second image that is moved to align the position of the patient P reflected in the second image with the position of the patient P reflected in the first image, based on the path of the treatment beam B set for the first image and the directional information related to the irradiation direction.

[0237] According to at least one embodiment described above, by having: a first image acquisition unit (102) that acquires a first image of three dimensions inside the patient (P); a second image acquisition unit (104) that acquires a second image of three dimensions inside the patient (P) taken at a different time than the first image; a direction acquisition unit (106) that acquires information (direction information) related to the irradiation direction of the radiation (therapeutic beam B) irradiating the patient (P) in the treatment room; and a movement amount calculation unit (120) that outputs a movement amount signal (SM) representing the movement amount of the second image that moves to align the position of the patient (P) shown in the second image with the position of the patient (P) shown in the first image, based on the path of the radiation (therapeutic beam B) set for the first image and the information (direction information) related to the irradiation direction, the patient (P) fixed on the examination table (12) can be moved to irradiate the tumor (lesion) with the amount of radiation (therapeutic beam B) planned in the treatment plan.

[0238] Several embodiments of the present invention have been described, but these embodiments are merely illustrative and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention as well as in the invention described in this disclosure and its equivalents.

Claims

1. A medical image processing device, characterized in that, have: The first image acquisition unit acquires a first three-dimensional image of the patient's body. The second image acquisition unit acquires a second three-dimensional image of the patient's body taken at a different time than the first image; The direction acquisition unit acquires information related to the direction of radiation irradiated toward the patient in the treatment room; as well as The motion calculation unit outputs a motion signal based on the path of the radiation set for the first image and information related to the irradiation direction. This motion signal represents the amount of movement of the second image to align the position of the patient shown in the second image with the position of the patient shown in the first image. The movement calculation unit includes: An approximate image calculation unit, based on the path of the radiation and information related to the irradiation direction, calculates an approximate image generated by shifting the first image by a predetermined amount in each degree of freedom according to the patient's position; and The registration unit uses the approximate image to calculate the offset between the first image and the second image, determines the amount of movement based on the calculated offset, and outputs a movement signal representing the determined amount of movement.

2. The medical image processing device according to claim 1, characterized in that, The movement calculation unit further includes an integral image calculation unit, which calculates a first integral image and a second integral image. The first integral image is an integral image that integrates the pixel values ​​of a first pixel in the three dimensions through which the radiation passes along the path of the radiation. The second integral image is an integral image that integrates the pixel values ​​of a second pixel in the three dimensions through which the radiation, irradiated from the irradiation direction, passes along the path of the radiation. The approximate image calculation unit calculates the approximate image based on the first integral image. The registration unit outputs a movement signal based on the offset between the second integral image and the approximate image.

3. The medical image processing device according to claim 2, characterized in that, The integral image calculation unit performs integral transformation on the pixel value of the first pixel located on the path of the radiation and the pixel value of the second pixel located on the path through which the radiation from the irradiation direction passes, after applying a predetermined nonlinear transformation, to calculate the first integral image and the second integral image respectively.

4. The medical image processing device according to claim 3, characterized in that, The integral image calculation unit transforms the pixel value of the first pixel located on the path of the radiation and the pixel value of the second pixel located on the path traversed by the radiation from the irradiation direction into values ​​representing the arrival energy of the radiation reaching each pixel through the nonlinear transformation.

5. The medical image processing device according to claim 4, characterized in that, The integral image calculation unit integrates the energy loss values ​​obtained by transforming the pixel value of the first pixel on the path of the radiation in the interval from the radiation to the area of ​​the irradiated object and the pixel value of the second pixel on the path of the radiation from the irradiation direction in the interval from the area of ​​the irradiated object to the area of ​​the irradiated object, respectively, to calculate the first integral image and the second integral image.

6. The medical image processing device according to claim 1, characterized in that, It also includes a region acquisition unit that acquires region information related to the region of the tumor in the patient's body based on information about the patient's treatment plan. The motion calculation unit further includes a motion inference unit, which infers the motion of the tumor based on the first image, the second image, and the region information. The registration unit outputs a movement signal based on the offset, including the movement of the tumor inferred by the motion inference unit.

7. The medical image processing device according to claim 6, characterized in that, The regional information includes at least the region of the tumor and the region of organs at risk located around the tumor.

8. The medical image processing device according to claim 1, characterized in that, It also includes a user interface section with a display device that displays at least an image for confirming the offset calculated by the registration section.

9. The medical image processing device according to claim 8, characterized in that, The user interface unit also includes an input device for inputting an adjustment value, which is used to adjust the amount of movement set based on the image displayed on the display device. The registration unit outputs a movement signal that adjusts the movement amount using the adjustment value input to the input device.

10. The medical image processing device according to claim 1, characterized in that, The movement signal is output to the examination bed control unit, which controls the examination bed of the treatment device.

11. The medical image processing device according to claim 1, characterized in that, The area targeted by the radiation is the region of a tumor present in the patient's body. The path of the radiation includes the region of the tumor.

12. The medical image processing device according to claim 1, characterized in that, When the second image is moved by the amount of movement represented by the movement signal output by the movement calculation unit, the path traversed by the radiation irradiated from the irradiation direction includes an area that avoids the irradiation of the radiation.

13. A treatment system, characterized in that, have: The medical image processing apparatus according to any one of claims 1 to 12; and The treatment device includes an irradiation unit that irradiates the patient with radiation, an imaging device that captures the first image and the second image, an examination bed that places and fixes the patient, and an examination bed control unit that controls the movement of the examination bed according to the movement signal.

14. A medical image processing device, characterized in that, have: The first image acquisition unit acquires a first three-dimensional image of the patient's body. The second image acquisition unit acquires a second three-dimensional image of the patient's body taken at a different time than the first image; The direction acquisition unit acquires information related to the direction of radiation irradiated toward the patient in the treatment room; as well as The motion calculation unit outputs a motion signal based on the path of the radiation set for the first image and information related to the irradiation direction. This motion signal represents the amount of movement of the second image to align the position of the patient shown in the second image with the position of the patient shown in the first image. The movement calculation unit includes: An approximate image calculation unit calculates a two-dimensional approximate image that maps the first image onto a plane, based on the path of the radiation and information related to the direction of illumination; and The registration unit uses the approximate image to calculate the offset between the first image and the second image, determines the amount of movement based on the calculated offset, and outputs a movement signal representing the determined amount of movement.

15. A medical image processing method, characterized in that, The computer performs the following actions: The first three-dimensional image of the patient's body was obtained. Obtain a second three-dimensional image of the patient's body taken at a different time than the first image. Information relating to the direction of radiation irradiation directed at the patient in the treatment room is obtained. Based on the path of the radiation rays defined in the first image and information related to the irradiation direction, a motion signal is output. This motion signal represents the amount of movement of the second image to align the position of the patient projected in the second image with the position of the patient projected in the first image. The computer also performs the following actions: Based on the path of the radiation and information related to the direction of irradiation, an approximate image is calculated by shifting the first image by a predetermined amount in each degree of freedom according to the patient's changing position. The approximate image is used to calculate the offset between the first image and the second image, the calculated offset is used to determine the amount of movement, and the amount of movement signal representing the determined amount of movement is output.

16. A storage medium storing a program, characterized in that, The program causes the computer to perform the following actions: The first three-dimensional image of the patient's body was obtained. Obtain a second three-dimensional image of the patient's body taken at a different time than the first image. Information relating to the direction of radiation irradiation directed at the patient in the treatment room is obtained. Based on the path of the radiation rays defined in the first image and information related to the irradiation direction, a motion signal is output. This motion signal represents the amount of movement of the second image to align the position of the patient projected in the second image with the position of the patient projected in the first image. The program also causes the computer to perform the following actions: Based on the path of the radiation and information related to the direction of irradiation, an approximate image is calculated by shifting the first image by a predetermined amount in each degree of freedom according to the patient's changing position. The approximate image is used to calculate the offset between the first image and the second image, the calculated offset is used to determine the amount of movement, and the amount of movement signal representing the determined amount of movement is output.

Images