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

Abstract

A medical image processing device according to an embodiment comprises: a first image acquisition unit that acquires a first image captured in a first stage; a second image acquisition unit that acquires a second image captured in a second stage and having a narrower imaging range than the first image; a 3D-3D positioning execution unit that aligns the position of the second image with the position of the first image; an image synthesis unit that generates a synthesized image by using, as the pixel values of the pixels of the second image, the pixel values of the pixels of the first image in a region that does not overlap the position-adjusted second image; a DRR generation unit that generates a two-dimensional DRR image from the synthesized image; a third image acquisition unit that acquires a third image captured in the second stage; and a display device that displays the DRR image and the third image.

Description

Medical Image Processing Apparatus, Treatment System, Medical Image Processing Method, Program, and Recording Medium

[0001] Embodiments of the present invention relate to a medical image processing apparatus, a treatment system, a medical image processing method, a program, and a recording medium. This application claims priority based on Japanese Patent Application No. 2024-193975 filed in Japan on November 5, 2024, the content of which is incorporated herein by reference.

[0002] Radiation therapy is a treatment method that destroys a lesion in a patient's body by irradiating the lesion with radiation. At this time, the radiation needs to be accurately irradiated to the position of the lesion. This is because if the normal tissue in the patient's body is irradiated with radiation, it may affect the normal tissue. Therefore, when performing radiation therapy, the position of the lesion in the patient's body is grasped three-dimensionally at the treatment planning stage. To perform this grasping, a three-dimensional fluoroscopic image of the patient is taken. A CT image obtained by Computed Tomography (CT) is an example of a three-dimensional fluoroscopic image. Based on the grasped position of the lesion, the direction of radiation irradiation and the intensity of the irradiated radiation are planned so as to reduce the irradiation to normal tissue. Then, at the treatment stage, the radiation is irradiated to the lesion according to the planned irradiation direction and irradiation intensity with the patient's position adjusted to the position of the patient at the treatment planning stage.

[0003] In the patient alignment at the treatment stage, a three-dimensional fluoroscopic image is virtually placed in the treatment room, and the position of the patient actually lying on the mobile bed in the treatment room is adjusted so as to coincide with the position of the three-dimensional fluoroscopic image.

[0004] Japanese Patent Publication No. 2018-507073

[0005] Here, a three-dimensional fluoroscopic image may also be taken immediately before irradiating the lesion with radiation. When taking a three-dimensional fluoroscopic image, it is required to reduce the patient's exposure dose.

[0006] This invention has been made in consideration of these circumstances and aims to provide a medical image processing device, a treatment system, a medical image processing method, a program, and a recording medium that can reduce the amount of radiation exposure to patients when acquiring three-dimensional fluoroscopic images.

[0007] The medical image processing apparatus of the embodiment includes: a first image acquisition unit that acquires a first image, which is a three-dimensional fluoroscopic image of a patient taken in a first stage; a second image acquisition unit that acquires a second image, which is a three-dimensional fluoroscopic image of the patient taken in a second stage after the first stage, and which has a narrower shooting range than the first image; a 3D-3D positioning execution unit that aligns the position of the second image with the position of the first image based on the pixel values ​​of the first image and the second image; an image synthesis unit that generates a composite image by using the pixel values ​​of pixels in the second image in a region that does not overlap with the second image whose position has been adjusted by the 3D-3D positioning execution unit as the pixel values ​​of pixels in the second image; a DRR generation unit that generates a two-dimensional DRR image from the composite image; a third image acquisition unit that acquires a third image, which is a two-dimensional fluoroscopic image of the patient taken in a second stage; and a display device that displays the DRR image and the third image.

[0008] According to embodiments of the present invention, the amount of radiation exposure to the patient when acquiring three-dimensional fluoroscopic images in the second stage can be reduced.

[0009] A block diagram showing the schematic configuration of a treatment system equipped with the medical image processing device of the embodiment. A block diagram showing the schematic configuration of the treatment system equipped with the medical image processing device of the embodiment, viewed from a different angle than Figure 1. A block diagram focusing on the schematic configuration of the medical image processing device of the embodiment. An example of a first image. An example of a second image. An example of a composite image. A flowchart showing an example of the processing flow executed by the medical image processing device of the embodiment.

[0010] The medical image processing apparatus, treatment system, medical image processing method, and program of the embodiment will be described below with reference to the drawings.

[0011] [Overall Configuration] Figure 1 is a block diagram showing the schematic configuration of a treatment system 1 equipped with a medical image processing device 100 of an embodiment. The treatment system 1 includes, for example, a treatment device 10, a medical image processing device 100, and a display device 200. The treatment device 10 includes, for example, a patient bed 12, a patient bed control unit 14, a treatment beam irradiation gate 18 (irradiation unit), and a first imaging device D1. In Figure 1, a computed tomography (CT) device 16 (hereinafter referred to as "CT imaging device 16") is shown as an example of the first imaging device D1.

[0012] The treatment table 12 is a movable treatment table that fixes a patient P (subject) receiving radiation therapy in a lying position, for example, using a restraint device. The treatment table 12 moves with the patient P fixed inside the annular CT scanner 16 having an opening, according to the control from the treatment table control unit 14. The treatment table control unit 14 controls the translational mechanism and rotational mechanism provided on the treatment table 12 in order to position the patient P fixed to the treatment table 12 according to the movement amount signal output by the medical image processing device 100. The translational mechanism can drive the treatment table 12 in three axial directions (X axis, Y axis, Z axis). The rotational mechanism can rotate the treatment table 12 around three axes. In other words, the treatment table control unit 14 moves the treatment table 12 with six degrees of freedom by controlling, for example, the translational mechanism and rotational mechanism of the treatment table 12. The bed control unit 14 has six degrees of freedom to control the bed 12, but may have fewer than six degrees of freedom (for example, four degrees of freedom) or more than six degrees of freedom (for example, eight degrees of freedom). The bed 12 is installed so as to be movable to both positions when the position where imaging by the CT scanner 16 is performed and the position where the treatment beam B is irradiated by the treatment beam irradiation gate 18 are different.

[0013] The CT scanner 16 performs three-dimensional computed tomography. The CT scanner 16 has multiple radiation sources arranged inside the annular (gantry) opening. Each of the multiple radiation sources emits radiation to visualize the inside of the patient P's body. In other words, the CT scanner 16 emits radiation from multiple locations around the patient P. In the CT scanner 16, the radiation emitted from each of the multiple radiation sources is, for example, X-rays. The CT scanner 16 has multiple radiation detectors arranged inside the annular opening. Each of the multiple radiation detectors detects radiation emitted from the corresponding radiation source and that has passed through the patient P's body. The CT scanner 16 generates a CT image of the inside of the patient P's body based on the magnitude of the radiation energy detected by each of the multiple radiation detectors. The CT image of patient P generated by the CT scanner 16 is a three-dimensional digital image. The three-dimensional digital image represents the magnitude of the degree of radiation attenuation at each of the multiple locations inside the body as a digital value. The CT scanner 16 outputs the generated CT image to the medical image processing device 100. The imaging of the inside of the patient P's body in the CT scanner 16, that is, the generation of a CT image based on the irradiation of radiation from each of the multiple radiation sources and the radiation detected by each of the multiple radiation detectors, is controlled, for example, by an imaging control unit (not shown).

[0014] The treatment beam irradiation gate 18 irradiates the patient P with radiation as treatment beam B to destroy the tumor (lesion), which is the target area for treatment, located within the patient P's body. Treatment beam B can be, for example, X-rays, gamma rays, proton beams, neutron beams, or heavy ion beams. Treatment beam B is irradiated linearly from the treatment beam irradiation gate 18 to the patient P (more specifically, the tumor inside the patient P's body). The irradiation of treatment beam B at the treatment beam irradiation gate 18 is controlled, for example, by a treatment beam irradiation control unit (not shown). In the illustrated treatment system 1, the treatment beam irradiation gate 18 is an example of an "irradiation unit".

[0015] In radiation therapy, the irradiation direction and intensity of the treatment beam B are planned by simulating the patient P being placed on the treatment table 12 in the treatment room. This stage of planning the treatment is called the "treatment planning stage." The treatment planning stage is an example of the "first stage." After the first stage, the second stage is performed. Here, the "second stage" is a concept that includes not only the period during which the treatment beam B is actually irradiated to the patient P, but also the period immediately before and after that.

[0016] In the treatment planning stage, the physician specifically identifies the areas to be irradiated from the CT image and determines the irradiation angle of the treatment beam. For this reason, the CT image in the treatment planning stage is accompanied by supplementary information such as parameters representing the angle of the treatment table 12 in the treatment room and the patient's position (lying on their back or stomach). The supplementary information may also include information such as the location of the tumor and the location of organs at risk that should be avoided from radiation exposure. The supplementary information may also include parameters assigned to each pixel of the CT image for coloring the location of the tumor, the location of organs at risk, etc. The CT image taken inside the patient P's body by the CT scanner 16 does not have supplementary information attached. Therefore, supplementary information may be added to the CT image taken inside the patient P's body by the CT scanner 16 by comparing it with a CT image that has supplementary information, such as the CT image in the treatment planning stage. For example, the pixel value of the tumor image region in the CT image with supplementary information may be used as a reference, and compared with the pixel value of the CT image without supplementary information, and the location where the difference in pixel value is small may be used as the tumor location in the CT image without supplementary information. This treatment can be applied not only to tumors but also to organs at risk.

[0017] Figure 1 shows a CT scanner 16 as an example of the first imaging device D1. However, the first imaging device D1 can be any device that generates three-dimensional images of the inside of the patient P's body, such as a cone-beam (CB) CT scanner, a magnetic resonance imaging (MRI) scanner, or an ultrasound diagnostic device.

[0018] In the second stage, the medical image processing device 100 outputs a movement amount signal to the bed control unit 14 to move the bed 12 in order to position the patient P in the same position as in the treatment planning stage. In other words, the medical image processing device 100 outputs a movement amount signal to the bed control unit 14 to move the patient P so that the treatment beam B can be appropriately irradiated to the tumor or tissue to be treated in radiotherapy. The movement amount signal is determined based on the first displacement amount and the second displacement amount, etc., which will be described later.

[0019] In the second stage, the display device 200 displays images to present various information in the treatment system 1 to the radiation therapist (such as a doctor) using the treatment system 1, including information obtained during the patient P positioning process in the medical image processing device 100. The display device 200 displays various images, such as CT images and X-ray fluoroscopy images output by the medical image processing device 100, or images on which various information is superimposed. Here, various information includes, for example, patient information (age, sex, height, weight, etc.), image acquisition conditions (acquisition site, presence or absence of contrast agent, tube voltage, tube current, etc.), date and time of acquisition, or patient position (head supine, feet prone, etc.). The display device 200 includes, for example, a device such as a liquid crystal display (LCD). The radiation therapist can obtain information for performing radiation therapy using the treatment system 1 by visually confirming the images displayed on the display device 200. The treatment system 1 may be configured to include a user interface, such as an operating unit (not shown), which is operated by the person performing the radiation therapy, and to allow manual operation of various functions performed by the treatment system 1.

[0020] Figure 2 is a schematic diagram of the treatment system 1, viewed from a different angle than Figure 1. Figure 2 is a block diagram showing the schematic configuration of the treatment system. As shown in Figure 2, the treatment system 1 includes a second imaging device D2. The second imaging device D2 has, for example, two radiation sources 20 (radiation source 20-1 and radiation source 20-2) and two radiation detectors 30 (radiation detector 30-1 and radiation detector 30-2). However, the second imaging device D2 may be, for example, an ultrasound diagnostic device.

[0021] Radiation source 20-1 irradiates patient P with radiation r-1 at a predetermined angle for fluoroscopy of the patient's body. Radiation source 20-2 irradiates patient P with radiation r-2 at a predetermined angle different from that of radiation source 20-1 for fluoroscopy of the patient's body. Radiation r-1 and radiation r-2 are, for example, X-rays. Figure 2 shows a case where X-ray imaging is performed from two directions on patient P, who is fixed on a bed 12. Note that in Figure 2, the control unit that controls the irradiation of radiation r-1 and r-2 by radiation source 20 is omitted. In the following description, radiation r-1 and r-2 may be simply referred to as radiation r.

[0022] Radiation detector 30-1 detects radiation r-1 that has been irradiated from radiation source 20-1 and passed through the body of patient P, and generates an X-ray fluoroscopic image of the inside of patient P corresponding to the energy magnitude of the detected radiation r-1. Radiation detector 30-2 detects radiation r-2 that has been irradiated from radiation source 20-2 and passed through the body of patient P, and generates an X-ray fluoroscopic image of the inside of patient P corresponding to the energy magnitude of the detected radiation r-2. In radiation detector 30, multiple X-ray detectors are arranged in a two-dimensional array. Radiation detector 30 generates a digital image as an X-ray fluoroscopic image, which represents the energy magnitude of the radiation r that has reached each of the multiple X-ray detectors as a digital value. This X-ray fluoroscopic image is an example of a "third image". The third image is a two-dimensional fluoroscopic image of patient P taken immediately before radiation therapy (i.e., in the second stage). The third image may also be an echo image generated by an ultrasound diagnostic device.

[0023] The radiation detector 30 is, for example, a flat panel detector (FPD), an image intensifier, or a color image intensifier. The following describes the case where each of the multiple radiation detectors 30 is an FPD. Each radiation detector 30 (FPD) outputs the generated X-ray fluoroscopic image to the medical image processing device 100. Note that in Figure 2, the control unit that controls the generation of X-ray fluoroscopic images by the radiation detectors 30 is omitted from the diagram.

[0024] The specific configuration of the second imaging device D2 may be changed. For example, the second imaging device D2 may be equipped with three or more sets of radiation sources 20 and radiation detectors 30. Alternatively, the second imaging device D2 may be equipped with only one set of radiation sources 20 and radiation detectors 30. Hereinafter, the combination of radiation sources 20 and radiation detectors 30 may be referred to as an "X-ray imaging device".

[0025] The various components shown in Figures 1 and 2 may be connected to each other by wires, or they may be connected wirelessly, for example, by a LAN (Local Area Network) or a WAN (Wide Area Network).

[0026] [Medical Image Processing Device] The medical image processing device 100 of the embodiment will be described below. Figure 3 is a block diagram mainly showing the schematic configuration of the medical image processing device 100 of the embodiment. The medical image processing device 100 includes, for example, a first image acquisition unit 110, a second image acquisition unit 120, a 3D-3D positioning execution unit 130, an image synthesis unit 140, a DRR generation unit 150, a third image acquisition unit 160, a 2D-3D positioning execution unit 170, and a display control unit 180.

[0027] Some or all of the components of the medical image processing device 100 are realized, for example, by a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or GPU (Graphics Processing Unit), or by the cooperation of software and hardware. Some or all of the functions of these components may be realized by a dedicated LSI. The program may be stored in advance in a storage device (a storage device equipped with a non-transient recording medium) such as ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), or flash memory provided by the medical image processing device 100. The program may also be stored in a removable recording medium (a non-transient recording medium) such as a DVD or CD-ROM, and installed in the HDD or flash memory of the medical image processing device 100 when the recording medium is inserted into the drive device provided by the medical image processing device 100. The program may also be downloaded from another computer device via a network and installed in the HDD or flash memory of the medical image processing device 100.

[0028] The first image acquisition unit 110 acquires a first image IM1 of patient P during the treatment planning stage (first stage) and associated information attached to the first image IM1. The first image IM1 is a three-dimensional CT image representing the three-dimensional shape of the patient P's body, for example, taken by a CT scanner 16 during the treatment planning stage. The first image IM1 is used to determine the direction (path including inclination and distance, etc.) and intensity of the treatment beam B irradiated onto patient P during radiation therapy. The first image IM1 may also be an MRI image taken by an MRI scanner during the treatment planning stage. The first image IM1 may include the aforementioned associated information. The first image acquisition unit 110 may acquire multiple first images IM1 taken at different timings within the respiratory cycle of the same patient P.

[0029] The second image acquisition unit 120 acquires a second image IM2 of patient P immediately before the start of radiation therapy (i.e., the second stage), and associated information attached to the second image IM2. The second image IM2 is a three-dimensional CT image representing the three-dimensional shape of the inside of patient P's body, taken, for example, by a CT scanner 16, in order to adjust the position of patient P when irradiating with the treatment beam B during radiation therapy (i.e., positioning). In other words, the second image IM2 is an image taken by the CT scanner 16 immediately before irradiating with the treatment beam B from the treatment beam irradiation gate 18. In this case, the time at which the first image IM1 is acquired and the time at which the second image IM2 is acquired are different, but the method of acquiring the first image is the same as the method of acquiring the second image. The second image IM2 may also be an MRI image taken by an MRI scanner in the second stage. The second image acquisition unit 120 may acquire multiple second images IM2 taken at different timings within the respiratory cycle of the same patient P.

[0030] In this embodiment, the imaging range of the second image IM2 is narrower than that of the first image IM1. For example, Figure 4 is an example of the first image IM1, and Figure 5 is an example of the second image IM2. In the example shown in Figure 4, the imaging range of the first image IM1 is almost the entire head of patient P. In contrast, in the example shown in Figure 5, the imaging range of the second image IM2 is only the area around the maxilla of patient P. The second image IM2 may include, for example, a tumor or lesion to be irradiated with the treatment beam B. By acquiring a three-dimensional image of the area to be irradiated with the treatment beam B not only in the first stage (treatment planning stage) but also in the second stage, it becomes possible to reflect the condition of patient P immediately before treatment in the treatment. Furthermore, by making the imaging range of the second image IM2 narrower than that of the first image IM1, the amount of radiation exposure to patient P when acquiring the second image IM2 can be reduced. In addition, the time required in the second stage can be shortened, reducing the burden on patient P. In this embodiment, in the vertical direction (first direction) of the images shown in Figures 4 and 5, the length of the second image IM2 is shorter than the length of the first image IM1. The meaning of the phrase "narrow shooting range" is not limited to the examples shown in Figures 4 and 5. For example, in the horizontal direction (second direction intersecting the first direction) of the image, the length of the second image IM2 may be shorter than the length of the first image IM1.

[0031] The 3D-3D positioning execution unit 130 performs 3D-3D positioning processing to align the position of patient P when performing radiation therapy, based on the first image IM1 acquired by the first image acquisition unit 110 and the second image IM2 acquired by the second image acquisition unit 120. More specifically, for example, the medical image processing device 100 calculates a three-dimensional displacement amount (hereinafter sometimes referred to as the "first displacement amount") between the first image IM1 acquired by the first image acquisition unit 110 and the second image IM2 acquired by the second image acquisition unit 120, for example, expressed as rotation and translation around the XYZ axes in three-dimensional space, and aligns the positions between the first image IM1 and the second image IM2 by moving the second image IM2 by the calculated first displacement amount.

[0032] In the second stage, the medical image processing device 100 may output a movement amount signal to the bed control unit 14 to move the bed 12 on which the patient is placed and fixed by a first displacement amount, and the bed control unit 14 may move the bed 12 by the first displacement amount. Also, if the CT scanning device 16 and the treatment beam irradiation gate 18 are installed at separate locations, the medical image processing device 100 may output a movement amount signal to the bed control unit 14 to move the bed 12 by the distance between the CT scanning position and the irradiation position plus the first displacement amount. The bed control unit 14 may move the bed 12 by the distance between the CT scanning position and the irradiation position plus the first displacement amount.

[0033] The image synthesis unit 140 generates a composite image IMc using the first image IM1 and the second image IM2. Since the first image IM1 and the second image IM2 are three-dimensional images, the composite image IMc is also a three-dimensional image. Figure 6 shows an example of a composite image IMc generated by combining the first image IM1 shown in Figure 4 and the second image IM2 shown in Figure 5. In the example shown in Figure 6, the composite image IMc has a first region A1 corresponding to the first image IM1 and a second region A2 corresponding to the second image IM2. To generate such a composite image IMc, the image synthesis unit 140 generates the composite image IMc by, for example, using the pixel values ​​of pixels in the first image IM1 in a region that does not overlap with the second image IM2 whose position has been adjusted by the 3D-3D positioning execution unit 130 as the pixel values ​​of pixels in the second image IM2.

[0034] If the first image IM1 and the second image IM2 overlap with fractional pixel precision, the image synthesis unit 140 may use a weighted average of the pixel values ​​corresponding to the degree of overlap as the pixel values ​​of the synthesized image IMc in that region. The synthesized image IMc may also be given supplementary information that was included in the first image IM1 or the second image IM2 by copying that information.

[0035] The DRR generation unit 150 generates a two-dimensional DRR image based on the three-dimensional composite image IMc. A DRR (Digitally Reconstructed Radiograph) image is a digitally reconstructed X-ray photograph obtained by virtually reconstructing an X-ray fluoroscopic image from a three-dimensional image (for example, a CT image).

[0036] In the second stage, the third image acquisition unit 160 acquires the two-dimensional fluoroscopic image captured by the second imaging device D2 as the third image. Alternatively, the first image acquisition unit 110, the second image acquisition unit 120, and the third image acquisition unit 160 may acquire the first image, the second image, and the third image by reading data from the storage device provided by the medical image processing device 100.

[0037] The 2D-3D positioning execution unit 170 compares the third image acquired by the third image acquisition unit 160 with the DRR image generated by the DRR generation unit 150 and performs 2D-3D positioning processing. More specifically, the 2D-3D positioning execution unit 170 calculates the amount of three-dimensional displacement (hereinafter sometimes referred to as the "second displacement") between the patient's fluoroscopic image (third image) taken after moving the patient's bed 12, on which the patient P is placed and fixed, by a first displacement amount. The radiation therapist approves the positioning, for example, if the calculated second displacement is less than a threshold. On the other hand, if the calculated second displacement is greater than or equal to the threshold, the bed control unit 14 moves the bed 12 by the calculated second displacement amount, takes another fluoroscopic image of the patient, and the 2D-3D positioning execution unit 170 performs 2D-3D positioning processing again using the captured fluoroscopic image. The above process is repeated until the positioning is finally approved by the radiation therapist.

[0038] The 2D-3D positioning execution unit 170 may align the third image and the DRR image by normalized cross-correlation. In this case, the range for correlation is a small area, such as 3x3, centered on the pixels to be calculated.

[0039] The display control unit 180 displays various information processed by the medical image processing device 100 on the display device 200. For example, the display control unit 180 may display the composite image IMc and the third image on the display device 200. Alternatively, for example, the display control unit 180 may display the results of 3D-3D positioning processing or the results of 2D-3D positioning processing on the display device 200.

[0040] Next, with reference to Figure 7, the processing flow performed by the medical image processing device 100 will be described. Figure 7 is a flowchart showing an example of the processing flow performed by the medical image processing device 100.

[0041] First, the first image acquisition unit 110 acquires a three-dimensional fluoroscopic image (e.g., a CT image) that was previously taken during the treatment planning stage as the first image IM1 (step S100). Next, the medical image processing device 100 moves the bed 12 on which the patient P is fixed to a position where it can be photographed by the first imaging device D1 (e.g., a CT scanner 16) (step S102). Specifically, the medical image processing device 100 outputs a movement amount signal to the bed control unit 14. The bed control unit 14 controls the translation mechanism and the like provided on the bed 12. Next, the first imaging device D1 takes a three-dimensional fluoroscopic image (e.g., a CT image) of the patient P (step S104). Next, the second image acquisition unit 120 acquires the three-dimensional fluoroscopic image taken in step S104 as the second image IM2 (step S106).

[0042] Next, the 3D-3D positioning execution unit 130 performs 3D-3D positioning processing based on the first image IM1 acquired by the first image acquisition unit 110 and the second image IM2 acquired by the second image acquisition unit 120, and calculates the first displacement amount (step S108). Next, the image synthesis unit 140 generates a synthesized image IMc based on the first image IM1 and the second image IM2 aligned using the first displacement amount (step S110). Next, the DRR generation unit 150 generates a DRR image based on the synthesized image IMc (step S112). Next, the bed control unit 14 corrects the position of the bed 12 based on the first displacement amount identified by the 3D-3D positioning processing (step S114). In step S114, if necessary, the position of the bed 12 may be moved to a position where the patient P can be treated by the treatment beam irradiation gate 18.

[0043] Next, the second imaging device D2 captures a two-dimensional fluoroscopic image (e.g., an X-ray image) of the patient P (step S116). Next, the third image acquisition unit 160 acquires the two-dimensional fluoroscopic image captured in step S116 as the third image. Next, the 2D-3D positioning execution unit 170 executes 2D-3D positioning processing and calculates the second deviation amount (step S120). Next, the medical image processing apparatus 100 determines whether or not the positioning has been approved by the operator of the radiation therapy (step S122). More specifically, the medical image processing apparatus 100 may determine whether or not the positioning has been manually approved by the operator of the radiation therapy through the interface on the display device 200. The medical image processing apparatus 100 may automatically determine the approval of the positioning by determining whether or not the second deviation amount is within the threshold value.

[0044] If it is determined in step S122 that the positioning has been approved, the medical image processing apparatus 100 determines the positioning and ends the processing of this flowchart. On the other hand, if it is not determined in step S122 that the positioning has been approved, the bed control unit 14 moves the bed 12 by the second deviation amount specified by the 2D-3D positioning processing (step S124) and returns the processing to step S116 again. Through the processing of such a flowchart, the state of the patient P immediately before the radiation therapy (the second image IM2) can be reflected in the treatment. Therefore, more accurate treatment can be performed than when only the first image IM1 captured in the first stage is used.

[0045] Note that the medical image processing apparatus 100 may not include the 2D-3D positioning execution unit 170. The medical image processing apparatus 100 only needs to include the first image acquisition unit 110, the second image acquisition unit 120, the 3D-3D positioning execution unit 130, the image synthesis unit 140, the DRR generation unit 150, and the third image acquisition unit 160. Even in this case, the medical image processing apparatus 100 can generate the composite image IMc based on the first image IM1 and the second image IM2. Furthermore, it is possible to generate a DRR from the composite image IMc and compare the DRR with the third image in the same image area. Note that the medical image processing apparatus 100 may execute processing different from the flowchart shown in FIG. 7.

[0046] As described above, the medical image processing apparatus 100 according to the embodiment includes a first image acquisition unit 110 that acquires a first image IM1, which is a three-dimensional fluoroscopic image of the patient P taken in the first stage; a second image acquisition unit 120 that acquires a second image IM2, which is a three-dimensional fluoroscopic image of the patient P taken in a second stage after the first stage and has a smaller imaging range than the first image IM1; a 3D-3D positioning execution unit 130 that aligns the position of the second image IM2 with the position of the first image IM1 based on the pixel values of the first image IM1 and the second image IM2; an image synthesis unit 140 that generates a composite image IMc by setting the pixel values of the pixels of the first image IM1 in a region that does not overlap with the second image IM2 whose position has been adjusted by the 3D-3D positioning execution unit 130 (for example, the region A1 shown in FIG. 6) to the pixel values of the pixels of the second image IM2; a DRR generation unit 150 that generates a two-dimensional DRR image from the composite image IMc; a third image acquisition unit 160 that acquires a third image, which is a two-dimensional fluoroscopic image of the patient taken in the second stage; and a display device 200 that displays the composite image IMc.

[0047] According to such a medical image processing apparatus 100, a composite image IMc is generated based on the first image IM1 and the second image IM2. The second image IM2 has a smaller imaging range than the first image IM1. Therefore, the radiation dose to the patient P can be suppressed. Also, since the time required to take the second image IM2 is reduced, the burden on the patient P can be reduced.

[0048] Further, the medical image processing apparatus 100 may include a 2D-3D positioning execution unit 170 that aligns the DRR image and the third image. In this case, by performing 2D-3D positioning using the DRR image generated from the composite image IMc, the position of the hospital bed 12 on which the patient P is placed can be controlled more accurately, and the treatment beam B can be irradiated to the target position.

[0049] Further, the image synthesis unit 140 may generate the composite image IMc by setting only the pixel values of the bone part pixels of the first image IM1 included in the region (for example, the region A1 shown in FIG. 6) to the pixel values of the pixels of the second image IM2.

[0050] Furthermore, supplementary information may be attached to the first image IM1. Supplementary information may also be attached to the composite image IMc by copying some or all of the supplementary information attached to the first image IM1. The display device 200 may display the supplementary information attached to the composite image IMc. In this case, the supplementary information of the first image IM1 taken during the treatment planning stage (for example, the location of the tumor or the location of risk organs that should be avoided from radiation exposure) can also be displayed on the composite image IMc, thereby improving convenience for the person performing the radiation therapy.

[0051] Furthermore, the 2D-3D positioning execution unit 170 may align the DRR image and the third image by normalized cross-correlation.

[0052] Furthermore, the 3D-3D positioning execution unit 130 may compare two or more first images IM1 with one or more second images IM2, select a pair of first images IM1 and second images IM2 with high similarity based on pixel values, and perform alignment using the selected pair. Here, "two or more first images IM1" refers, for example, to multiple CT images taken at different timings within the respiratory cycle. The position of a tumor may change depending on the respiratory cycle, and by using a pair of first images IM1 and second images IM2 with high similarity, a composite image IMc can be generated with reduced deviation due to the respiratory cycle.

[0053] Furthermore, the treatment system 1 of this embodiment comprises a medical image processing device 100 and a treatment device 10. The treatment device 10 includes an irradiation unit (treatment beam irradiation gate 18) for irradiating the patient P with radiation, a first imaging device D1 for capturing a second image IM2, a bed 12 for placing and fixing the patient P, and a bed control unit 14 for controlling the movement of the bed 12. With this treatment system 1, it becomes possible to treat the patient P after performing positional alignment using a composite image IMc.

[0054] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These embodiments can be carried out in a variety of other forms, 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 claims and their equivalents.

[0055] 1...Treatment system 10...Treatment device 12...Treatment table 14...Treatment table control unit 100...Medical image processing device 110...First image acquisition unit 120...Second image acquisition unit 130...3D-3D positioning execution unit 140...Image synthesis unit 150...DRR generation unit 160...Third image acquisition unit 170...2D-3D positioning execution unit 200...Display device A1...Region D1...First imaging device IM1...First image IM2...Second image IMc...Synthesized image P...Patient

Claims

1. A medical image processing device comprising: a first image acquisition unit that acquires a first image, which is a three-dimensional fluoroscopic image of the patient taken in a first stage; a second image acquisition unit that acquires a second image, which is a three-dimensional fluoroscopic image of the patient taken in a second stage after the first stage, and which has a narrower shooting range than the first image; a 3D-3D positioning execution unit that aligns the position of the second image with the position of the first image based on the pixel values ​​of the first image and the second image; an image synthesis unit that generates a composite image by using the pixel values ​​of pixels in the second image in a region that does not overlap with the second image whose position has been adjusted by the 3D-3D positioning execution unit as the pixel values ​​of pixels in the second image; a DRR generation unit that generates a two-dimensional DRR image from the composite image; a third image acquisition unit that acquires a third image, which is a two-dimensional fluoroscopic image of the patient taken in a second stage; and a display device that displays the DRR image and the third image.

2. A medical image processing apparatus according to claim 1, comprising: a 2D-3D positioning execution unit for aligning the DRR image and the third image.

3. The medical image processing apparatus according to claim 1, wherein the image synthesis unit generates the synthesized image by using only the pixel values ​​of the pixels of the bone portion of the first image included in the region as the pixel values ​​of the pixels of the second image.

4. The medical image processing apparatus according to claim 1, wherein the display device displays only the pixels of the bone portion of the composite image.

5. The medical image processing apparatus according to claim 1, wherein the first image is provided with supplementary information, the composite image is provided with at least a portion of the supplementary information, and the display device displays the supplementary information provided with the composite image.

6. The medical image processing apparatus according to claim 2, wherein the DRR generation unit generates the DRR image from only the pixels of the bone portion.

7. The medical image processing apparatus according to claim 1, wherein the 3D-3D positioning execution unit compares two or more first images with one or more second images, selects a pair of first and second images with a high similarity based on pixel values, and performs alignment using the selected pair.

8. A treatment system comprising: a medical image processing device according to any one of claims 1 to 7; an irradiation unit for irradiating the patient with radiation; a first imaging device for capturing the second image; a bed for placing and fixing the patient; and a bed control unit for controlling the movement of the bed.

9. A medical image processing method comprising: a computer acquiring a first image, which is a three-dimensional fluoroscopic image of a patient taken in a first stage; acquiring a second image, which is a three-dimensional fluoroscopic image of the patient taken in a second stage after the first stage, and which has a narrower imaging range than the first image; performing 3D-3D positioning to align the position of the second image with the position of the first image based on the pixel values ​​of the first image and the second image; generating a composite image by using the pixel values ​​of pixels in the second image in a region that does not overlap with the second image whose position has been adjusted by the 3D-3D positioning execution unit as the pixel values ​​of pixels in the second image; generating a two-dimensional DRR image from the composite image; acquiring a third image, which is a two-dimensional fluoroscopic image of the patient taken in the second stage; and displaying the DRR image and the third image on a display device.

10. A program that causes a computer to acquire a first image, which is a three-dimensional fluoroscopic image of the patient taken in the first stage; acquire a second image, which is a three-dimensional fluoroscopic image of the patient taken in the second stage after the first stage, and which has a narrower shooting range than the first image; perform 3D-3D positioning to align the position of the second image with the position of the first image based on the pixel values ​​of the first and second images; generate a composite image by using the pixel values ​​of pixels in the second image in a region that does not overlap with the second image whose position has been adjusted by the 3D-3D positioning execution unit as the pixel values ​​of pixels in the second image; generate a two-dimensional DRR image from the composite image; acquire a third image, which is a two-dimensional fluoroscopic image of the patient taken in the second stage; and display the DRR image and the third image on a display device.

11. A recording medium on which a program is recorded, wherein the program causes a computer to: acquire a first image, which is a three-dimensional fluoroscopic image of a patient taken in a first stage; acquire a second image, which is a three-dimensional fluoroscopic image of the patient taken in a second stage after the first stage, and which has a narrower shooting range than the first image; perform 3D-3D positioning to align the position of the second image with the position of the first image based on the pixel values ​​of the first image and the second image; generate a composite image by using the pixel values ​​of pixels in the second image in a region that does not overlap with the second image whose position has been adjusted by the 3D-3D positioning execution unit as the pixel values ​​of pixels in the second image; generate a two-dimensional DRR image from the composite image; acquire a third image, which is a two-dimensional fluoroscopic image of the patient taken in a second stage; and display the DRR image and the third image on a display device.

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