JP2023033183A - Radiation treatment planning device - Google Patents

Abstract

To provide radiation treatment planning capable of suppressing a damage to normal tissue and enabling an appropriate irradiation effect to be obtained.SOLUTION: A radiation treatment planning device according to an embodiment includes a dose rate distribution information acquisition unit and an irradiation effect identification information acquisition unit. The dose rate distribution information acquisition unit acquires dose rate distribution information representing distribution of dose rates on an irradiation path of radiation on the basis of an irradiation condition of the radiation. The irradiation effect identification information acquisition unit acquires irradiation effect identification information that identifies a radiation irradiation effect in the irradiation path on the basis of the acquired dose rate distribution information.SELECTED DRAWING: Figure 2

Description

The embodiments disclosed in the specification and drawings relate to radiation therapy planning apparatus.

In radiation therapy, high dose rate irradiation (hereinafter referred to as FLASH irradiation) in which a much higher dose rate (e.g., 40 Gy/sec or more) is applied in a short time compared to the conventional dose rate (e.g., about 0.03 Gy/sec) ) is known. FLASH irradiation has the effect of suppressing damage to normal tissue while treating the target tumor (hereinafter referred to as the FLASH effect), so side effects are suppressed more than before, leading to safer radiotherapy. is expected.

On the other hand, radiation such as electron beams (MeV) attenuates according to the depth inside the body where the radiation is irradiated. Failure to do so may result in damage to normal tissue.

Japanese Patent Publication No. 2020-533123

One of the problems to be solved by the embodiments disclosed in the present specification and drawings is to provide a radiotherapy plan that suppresses damage to normal tissue and provides an appropriate irradiation effect. However, the problems to be solved by the embodiments disclosed in this specification and drawings are not limited to the above problems. A problem corresponding to each effect of each configuration shown in the embodiments described later can be positioned as another problem.

A radiotherapy planning apparatus according to an embodiment includes a dose rate distribution information acquisition unit and an irradiation effect identification information acquisition unit. The dose rate distribution information acquisition unit acquires dose rate distribution information representing the distribution of the dose rate in the irradiation route of the radiation based on the irradiation conditions of the radiation. The irradiation effect identification information acquisition unit acquires irradiation effect identification information for identifying an irradiation effect of radiation in the irradiation route based on the acquired dose rate distribution information.

FIG. 1 is a diagram showing a configuration example of a radiotherapy system according to one embodiment. FIG. 2 is a diagram showing a configuration example of a radiotherapy planning apparatus according to one embodiment. FIG. 3 is a schematic diagram for explaining the FLASH irradiation table and the normal irradiation table. FIG. 4 is a diagram showing the depth at which the X-ray attenuation divides the FLASH area and the non-FLASH area. FIG. 5 is a diagram showing a typical flow of treatment planning processing by a radiotherapy planning apparatus. FIG. 6 is a diagram showing a display example in which a FLASH area and a non-FLASH area are superimposed on a medical image. FIG. 7 is a schematic diagram for explaining the FLASH area and the non-FLASH area in FIG. FIG. 8 is a schematic diagram for supplementary explanation of the FLASH area and the non-FLASH area in FIG. FIG. 9 is a diagram showing an example of dose rate distribution in the depth direction corresponding to attenuation of radiation applicable to the radiotherapy planning apparatus according to the first modification of the embodiment. FIG. 10 is a diagram showing the depth at which the electron beam attenuation in FIG. 9 separates the FLASH region and the non-FLASH region. FIG. 11 is a diagram showing the depth at which the proton beam Bragg peak in FIG. 9 separates the FLASH region and the non-FLASH region. FIG. 12 is a diagram showing a display example in which a FLASH area and a non-FLASH area are superimposed on a medical image in the second modification of one embodiment.

The configuration of a radiotherapy system according to one embodiment will be described below with reference to the drawings. As shown in FIG. 1 , the radiation therapy system 1 has a medical image diagnostic device 2 , a radiation therapy planning device 3 and a radiation therapy device 4 . The medical image diagnostic apparatus 2, the radiotherapy planning apparatus 3, and the radiotherapy apparatus 4 are communicably connected to each other via a network. The radiotherapy system 1 is a system that draws up a treatment plan for radiotherapy of a patient and executes radiotherapy according to the treatment plan.

The medical image diagnostic apparatus 2 performs medical imaging on a patient to be treated and generates a medical image used for treatment planning. The medical image may be a two-dimensional image composed of two-dimensionally arranged pixels, or a three-dimensional image composed of three-dimensionally arranged voxels. The medical image diagnostic device 2 may be any modality device capable of generating medical images. Modality devices include, for example, an X-ray computed tomography device, a magnetic resonance imaging device, a cone beam CT device, a nuclear medicine diagnosis device, and the like.

The radiotherapy planning apparatus 3 uses the medical images generated by the medical image diagnostic apparatus 2 to create a radiotherapy plan.

The radiotherapy apparatus 4 treats the patient by irradiating the patient with radiation according to the treatment plan created by the radiotherapy planning apparatus 3 . The radiotherapy apparatus 4 is installed in a treatment room and has a treatment platform and a treatment bed. The treatment couch moves the top plate so that the treatment site of the patient substantially coincides with the isocenter. The treatment platform supports the irradiation head part rotatably around the rotation axis. The irradiation head unit irradiates radiation according to a treatment plan. Specifically, the irradiation head unit forms an irradiation field with a multi-divided diaphragm (multi-leaf collimator), and suppresses irradiation of normal tissues by the irradiation field. By irradiating the treatment area with radiation, the treatment area disappears or shrinks.

Next, the configuration of the radiotherapy planning apparatus 3 shown in FIG. 1 will be described with reference to FIG. The radiotherapy planning apparatus 3 has a processing circuit 31 , a storage device 32 , a display device 33 , an input device 34 and a communication device 35 .

The storage device 32 is composed of a storage device such as a ROM (Read Only Memory), HDD (Hard Disk Drive), SSD (Solid State Drive), or the like. The storage device 32 stores various programs and various data. For example, as shown in FIG. 3, the storage device 32 stores a FLASH irradiation table 321 and a normal irradiation table 322 . The FLASH irradiation table 321 describes, for each organ, an organ name and a tolerable dose in FLASH irradiation in association with each other. The normal irradiation table 322 describes, for each organ, an organ name and a tolerable dose in normal irradiation in association with each other. The storage device 32 may also store an attenuation rate table that describes the attenuation rate of radiation in the direction of depth from the body surface for each direction of irradiation of radiation to the human body.

The display device 33 includes a display device such as a liquid crystal display (LCD), a CRT (Cathode Ray Tube) display, an organic EL display (OELD: Organic Electro Luminescence Display), or the like. The display device 33 displays various information under the control of the processing circuit 31 . The display device 33 is an example of a display unit.

The input device 34 is composed of an input interface device such as a mouse, keyboard, trackball, switch, button, joystick, touch pad, and touch panel display. The input device 34 receives various input operations by the user and supplies electrical signals corresponding to the received input operations to the processing circuit 31 .

The communication device 35 is composed of a communication interface device such as a NIC (Network Interface Card) that performs network communication. The communication device 35 receives medical images supplied from the medical image diagnostic apparatus 2 . Also, the communication device 35 transmits the treatment plan to the radiotherapy apparatus 4 .

The processing circuit 31 has a processor including a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), and the like. The processing circuit 31 controls the radiotherapy planning apparatus 3 as a whole by controlling each part of the radiotherapy planning apparatus 3 . Further, the processing circuit 31 executes a program stored in the storage device 32 to perform a dose rate distribution information acquisition function 311, an irradiation effect identification information acquisition function 312, a notification function 313, a determination function 314, and a display control function 315. come true. The dose rate distribution information acquisition function 311 and the processing circuit 31 are an example of a dose rate distribution information acquisition unit. The irradiation effect identification information acquisition function 312 and the processing circuit 31 are an example of the irradiation effect identification information acquisition unit. The notification function 313 and the processing circuit 31 are an example of a notification unit. The determination function 314 and the processing circuit 31 are examples of a determination unit. The display control function 315 and processing circuit 31 are an example of a display control unit. It should be noted that each of the functions 311-315 may be partially or wholly composed of an integrated circuit such as an ASIC (Application Specific Integrated Circuit).

The radiotherapy planning apparatus 3 configured as described above creates a radiotherapy plan. Here, in radiation therapy, high dose rate irradiation (hereinafter referred to as , FLASH irradiation) are known. FLASH irradiation has the effect of suppressing damage to normal tissue while treating the target tumor (hereinafter referred to as the FLASH effect), so side effects are suppressed more than before, leading to safer radiotherapy. is expected.

On the other hand, radiation such as electron beams (MeV) attenuates according to the depth inside the body where the radiation is irradiated. Failure to maintain the high dose rate required for normal tissue damage can result. Based on the set irradiation conditions, the radiotherapy planning system 3 identifies areas where the FLASH effect can be obtained (hereinafter referred to as FLASH area) and areas where the FLASH effect cannot be obtained (hereinafter referred to as non-FLASH area) on the irradiation path. and displays the specified area in an identifiable manner. Note that the FLASH area is an example of the first area. The non-FLASH area is an example of the second area.

Here, the FLASH area and the non-FLASH area will be explained with reference to FIG. FIG. 4 is a diagram showing an example of dose rate distribution in the depth direction corresponding to attenuation of X-rays, showing a depth D41 where the attenuation of X-rays separates the FLASH area FA and the non-FLASH area NFA. The vertical axis is the relative dose [%]. The horizontal axis is the irradiation depth of radiation, specifically, the depth [cm] from the radiation incident position (body surface). The relative dose varies according to the radiation attenuation (eg, attenuation rate) along the depth direction.

In FIG. 4, the higher the energy of the X-ray, the deeper the dose peak reaches. Since the X-rays shown in FIG. 4 are attenuated in different ways in the body depending on the direction of irradiation, the depth at which the FLASH effect can be obtained differs among the plurality of directions of irradiation. As described above, FLASH irradiation is to irradiate radiation at a high dose rate (for example, 40 Gy/sec or more) in a short period of time. The FLASH effect is an irradiation effect (therapeutic effect) obtained by FLASH irradiation, and is an effect of selectively damaging tumors while suppressing damage to normal tissues. In the present embodiment, attenuation is used to identify FLASH areas where the FLASH effect is obtained and non-FLASH areas where the FLASH effect is not obtained. In addition, in this embodiment, considering that attenuation increases with depth from the incident position, it is possible to specify a non-FLASH region where the FLASH effect cannot be obtained according to the depth or attenuation.

For example, FIG. 4 shows a depth D41 at which X-ray attenuation separates the FLASH area FA and the non-FLASH area NFA in a certain irradiation direction. The depth D41 can be determined based on the relative dose value (eg, 70%). Along with this, the FLASH area FA and the non-FLASH area NFA may be specified based on the depth D41 from the incident position of the X-ray, and the dose attenuation from the incident position (attenuation rate or relative dose value ).

A region deeper than the depth D41 shown in FIG. 4 has a dose rate lower than the dose rate of the FLASH irradiation, so the FLASH effect cannot be obtained and it becomes a non-FLASH region NFA. Such non-FLASH region NFAs may fail to reduce damage to normal tissue.

Next, an operation example of the radiotherapy planning apparatus 3 will be described. In the following description, medical images are assumed to be three-dimensional CT images acquired by an X-ray computed tomography apparatus.

FIG. 5 is a diagram showing a typical flow of treatment planning processing by the radiotherapy planning apparatus 3. As shown in FIG. The processing circuit 31 acquires a patient's medical image (step ST1). For example, the processing circuit 31 acquires medical image data received from the medical image diagnostic apparatus 2 . The patient's anatomical structure is depicted in the medical image acquired in step ST1.

When step ST1 is performed, the processing circuit 31 identifies a tumor and normal tissue other than the tumor from the medical image acquired in step ST1 (step ST2). The tumor is subject to radiotherapy. Normal tissues other than tumors are usually normal tissues and organs at risk. At-risk organs are organs that are particularly radiosensitive among normal tissues. For example, if the tumor is prostate cancer, the risk organs are the rectum, bladder, and the like. Usually normal tissue is normal tissue other than at-risk organs. An arbitrary method may be used as the identification method. For example, it may be done manually by the user. Specifically, the procedure is as follows. First, the processing circuit 31 displays the medical image on the display device 33 . A user draws a contour enclosing each of the tumor, normal normal tissue, and risk organ depicted in the medical image via an input device 34 such as a mouse or tablet pen. Processing circuitry 31 identifies the delineated image region as a tumor, normal normal tissue, or an organ at risk. Tumors, normal normal tissue and organs at risk each, if multiple, are identified separately. As the tumor outline, for example, regions of gross tumor volume GTV and clinical target volume CTV may be drawn. A tumor may also be identified as an area of the internal target volume ITV, which is the clinical target volume CTV plus an internal margin IM such as respiratory movement and peristalsis. A tumor may also be identified as a region of a planning target volume PTV, which is the in vivo target volume ITV plus a set up margin SM. Similarly, the organ at risk may also be identified as a region of the internal target volume ITV or the planned target volume PTV. In this case, the risk organs may be referred to as planning organs at risk volume PRV.

Note that the specifying method is not limited to the above method, and may be automatically performed by image processing. For example, the processing circuit 31 can perform thresholding or image recognition processing on the medical image to identify tumors, normal tissue, and organs at risk. The processing circuitry 31 may also store information representing the relationship between the irradiation depth of radiation and the attenuation rate of the radiation in the storage device 32 . For example, the processing circuit 31 obtains an attenuation rate table describing the attenuation rate of radiation in the depth direction for each irradiation direction of radiation to the human body, and stores it in the storage device 32 . The irradiation direction in the attenuation rate table may be, for example, every 1 degree, every 5 degrees, every 10 degrees, or every other interval. It should be noted that the attenuation rate in the irradiation direction that is not described in the attenuation rate table can be calculated by interpolation. The attenuation rate in the depth direction in the attenuation rate table may be described for each 1 mm depth, for each 0.5 mm depth, or for other intervals. The attenuation rate may be actually measured using a phantom, detector, or the like, or may be obtained by computer simulation. However, since the attenuation rate varies depending on the internal structure of the human body, a more accurate value is obtained based on the actual patient's human body structure, as in the case of determining from the patient's three-dimensional CT image. For example, when a 3D CT image (3D volume data) of a patient is acquired, the attenuation rate can be calculated from the integrated value of the X-ray CT values in the 3D volume data.

When step ST2 is performed, the processing circuit 31 sets irradiation conditions (provisional version) for FLASH irradiation (high dose rate irradiation) of radiation (step ST3). In step ST3, the processing circuit 31 sets an irradiation field, an irradiation direction, a dose, and a dose rate as irradiation conditions. An irradiation field is a region irradiated with radiation, and is set at least in a medical image. The irradiation direction is the direction in which radiation is irradiated. The irradiation direction is defined by the angle around the rotation center axis of the treatment platform of the radiotherapy apparatus 4 . Dose is defined as the total dose of radiation delivered during radiotherapy over multiple days. Dose rate is defined as the dose of radiation per unit time. In the case of FLASH irradiation, the dose rate is set to be much higher (for example, 40 Gy/sec or higher) than the conventional dose rate (for example, about 0.03 Gy/sec). Dose may be referred to as exposure dose and dose rate may be referred to as exposure dose rate. Dose and dose rate may be referred to as exposure dose index values.

In step ST3, the processing circuit 31 obtains the radiation attenuation rate in the depth direction based on the set irradiation conditions. For example, the processing circuit 31 searches the attenuation rate table in the storage device 32 based on the set irradiation direction to obtain the attenuation rate in the depth direction. It should be noted that attenuation factors in irradiation directions not described in the attenuation factor table are calculated by interpolation.

Also, in step ST3, the processing circuit 31 obtains the positions of the normal normal tissue, the risk organ, and the tumor on the irradiation path of the radiation in the three-dimensional CT image based on the once set irradiation conditions. In addition, the processing circuit 31 adjusts the irradiation direction and the number of beams so as to avoid risk organs and reduce the dose attenuation to the tumor. Since attenuation may be large even if the distance on the irradiation path is short, such as when there is a bone on the irradiation path, in step ST3, the irradiation direction and the number of beams are determined based on the attenuation rate instead of the distance. adjusting. After this adjustment, step ST3 ends.

When step ST3 is performed, the processing circuit 31 performs dose rate distribution calculation for acquiring dose rate distribution information representing the distribution of the dose rate in the irradiation route of the radiation based on the irradiation conditions set in step ST3 (step ST4). In step ST4, the processing circuit 31 may acquire dose rate distribution information, for example, based on radiation irradiation conditions and information representing the relationship between the irradiation depth of the radiation and the attenuation rate of the radiation. Further, in step ST4, the processing circuit 31 may generate a spatial distribution of predicted dose rates (dose rate distribution information) according to an arbitrary dose calculation algorithm based on the irradiation conditions and the medical image. The predicted dose rate is calculated as the predicted value of the administered dose rate for a single FLASH exposure. As a dose calculation algorithm, for example, an equivalent TAR (tissue-air ratio) method, a differential scattering air dose ratio method, a microvolume method, a Monte Carlo method, a convolution method, or the like can be used. In addition, the processing circuit 31 may use a learned model subjected to machine learning so as to output dose rate distribution information representing the distribution of the dose rate in the irradiation route of the radiation in response to the input of the radiation irradiation conditions. good. In this case, the processing circuit 31 may read the learned model from the storage device 32 and acquire the dose rate distribution information by operating the learned model. Alternatively, the processing circuit 31 may acquire dose rate distribution information by a configuration in which a learned model is incorporated in a processor circuit, such as ASIC or FPGA. The learned model is, for example, a learned machine learning model generated by having the machine learning model perform machine learning based on learning data.

When step ST4 is performed, the processing circuit 31 acquires irradiation effect identification information for identifying the irradiation effect of radiation in the irradiation route based on the acquired dose rate distribution information (step ST5). Specifically, for example, the processing circuit 31 may acquire the irradiation effect identification information based on a comparison between the dose rate represented by the acquired dose rate distribution information and a predetermined threshold value. Here, the irradiation effect identification information is information for identifying the irradiation effect of radiation with a high dose rate for a short period of time. For example, the irradiation effect identification information may be information for identifying, in the irradiation path, the FLASH area FA where the irradiation effect of radiation is obtained and the non-FLASH area NFA where the irradiation effect is not obtained. Note that the FLASH area FA and the non-FLASH area NFA constitute a radiation irradiation path. An irradiation path may be referred to as a beam path. Supplementally, the irradiation path can be either a FLASH region or a non-FLASH region at any depth within the body. For example, when irradiating X-rays, the irradiation path is followed by a FLASH area along the depth direction inside the body, and becomes a non-FLASH area from the depth where the dose rate is attenuated below the threshold. Such an irradiation route is the same even when gamma rays or electron beams are used instead of X-rays. When proton beams or carbon beams are used instead of X-rays, the irradiation path has a region where the dose increases along the depth direction of the body, and only the portion where the dose rate exceeds the threshold becomes the FLASH region. .

When step ST5 is performed, the processing circuit 31 superimposes the dose rate distribution calculation result and the irradiation effect identification information identifying the FLASH area FA and the non-FLASH area NFA on the medical image g1 of the subject, as shown in FIG. and display it on the display device 33 (step ST6). Here, the dose rate distribution calculation results within the FLASH area FA are indicated by dark shading corresponding to relatively high dose rates, and the dose rate distribution calculation results within the non-FLASH area NFA are relatively low. It is indicated by light shading according to the dose rate. Such dose rate distribution calculation results are actually displayed in different colors according to the dose rate distribution. In FIG. 6, the irradiation effect identification information includes a solid-line frame for identifying the FLASH area FA and a dashed-line frame for identifying the non-FLASH area NFA. In addition, the illumination effect identification information may include arrows within FLASH areas FA and arrows identifying non-FLASH areas NFA. The two arrows may be color coded to each other. The irradiation paths composed of the FLASH area FA and the non-FLASH area NFA in FIG. 6 are distributed in a substantially cross shape as shown in FIG. In FIG. 7, the substantially central portion of the medical image g1 is a FLASH area ( FA+FA) in the figure. Supplementally, as shown in FIG. 8, if the irradiation path of the irradiation direction "270 degrees" is shifted in the depth direction from the irradiation path of the irradiation direction "0 degrees", the FLASH area FA and the non-FLASH area A region A1 (FA+NFA in the figure) that overlaps with the NFA is generated. This area A1 becomes a non-FLASH area due to the influence of the non-FLASH area NFA in one irradiation path, and a sufficient FLASH effect cannot be obtained. Along with this, if there is an area where the FLASH area of one irradiation path and the non-FLASH area of the other irradiation path overlap among a plurality of irradiation paths with different irradiation directions, the processing circuit 31 may be identified as non-FLASH regions where no FLASH effect is obtained. Also, the irradiation effect identification information for identifying the FLASH area and the non-FLASH area may be displayed superimposed on another image. For example, the processing circuit 31 may superimpose the irradiation effect identification information on the phantom image or computer simulation image instead of the medical image g1. That is, the processing circuit 31 may cause the display device 33 to display the irradiation effect identification information superimposed on the phantom image or the computer simulation image.

When step ST6 is performed, the processing circuit 31 determines whether there is normal tissue (normal normal tissue and/or risk organ) at the position corresponding to the non-FLASH area NFA identified in the irradiation effect identification information of step ST5. (Step ST7) If the result of the determination is NO (no normal tissue is located), the processing circuit 31 proceeds to step ST11.

On the other hand, if the result of determination in step ST7 is that there is normal tissue in the position corresponding to the non-FLASH area NFA, the processing circuit 31 causes the display device 33 to display a warning prompting a change in irradiation conditions (step ST8). Warnings, for example, highlighting of normal tissue and warning messages are available as appropriate. For the highlighting of the normal tissue, for example, color-changing display, blinking display, etc. can be used as appropriate. The warning message may be, for example, a sentence prompting a change in irradiation conditions, such as "Risk organs are present in non-FLASH area NFA" or "Normal normal tissue is present in non-FLASH area NFA". Alternatively, the warning message may be a word such as "warning" that prompts the user to change the irradiation conditions. However, in the case of a word warning message, from the viewpoint of clearly showing the warning target, it is usually preferable to use it together with the highlighting of the normal tissue and/or the risk organ.

When step ST8 is performed, the processing circuit 31 determines whether or not the radiation dose exceeds the tolerable dose of the normal tissue if there is normal tissue at the position corresponding to the non-FLASH region (step ST9). For example, the processing circuit 31 may refer to the FLASH irradiation table 321 in the storage device 32 and perform the determination based on the tolerable dose corresponding to the organ name of the risk organ. As a result of the determination, if the dose exceeds the tolerable dose, the processing circuit 31 proceeds to step ST10.

In the above example, the tolerable dose is used as an index of the dose to the risk organ, but a DVH (Dose Volume Histogram) index that is generally used in treatment planning may also be used.

As a result of the determination in step ST9, if the tolerable dose is exceeded, the processing circuit 31 notifies the user of information based on the determination result, and sets new irradiation conditions (step ST10). That is, the processing circuit 31 causes the display device 33 to display a warning to the effect that the tolerable dose is exceeded, and according to the user's instruction via the input device 34 or according to a predetermined algorithm, the irradiation field, irradiation direction, dose, dose rate, etc. change the conditions. When changing the dose rate (Gy/sec), the value of the dose rate may be changed directly, or the value of the dose rate may be changed indirectly by changing the irradiation time (sec). The processing circuit 31 may change the irradiation direction, the number of beams, and the irradiation time, for example, as shown in (a) or (b) below. That is, the processing circuit 31 (a) changes the irradiation direction, the number of beams, or the irradiation time (step ST10), and updates the dose rate distribution calculation result and the irradiation effect identification information (steps ST4, ST5). Alternatively, when the (b) area from which the FLASH area FA is to be obtained is specified by the input device 34, the processing circuit 31 updates the beam direction, the number of beams, and the irradiation time according to the specified contents (step ST10). In any case, after step ST10 is completed, the processing circuit 31 executes steps ST4 to ST9 in the same manner as described above based on the changed irradiation conditions. The loop from step ST10 to ST10 via ST4-ST9 is repeatedly executed until it is determined in step ST7 that there is no normal tissue or until it is determined in step ST9 that the dose is below the tolerable dose. be.

As a result of the determination in step ST7, if it is determined that normal tissue is not located, or if it is determined that the dose is below the tolerable dose in step ST9, the processing circuit 31 sets the latest irradiation conditions set in step ST3 or ST10. is set as the final version (step ST11).

As described above, the processing circuit 31 can search for irradiation conditions for appropriate FLASH irradiation by executing steps ST3 to ST11. The final plate irradiation conditions are stored in the storage device 32 . After that, the processing circuit 31 creates radiotherapy plan data and transmits the radiotherapy plan data to the radiotherapy apparatus 4 . The radiotherapy plan data includes, for example, the superimposed image data displayed in step ST6 and the irradiation conditions set in step ST11.

When the radiotherapy planning data is transmitted, the radiotherapy planning process by the radiotherapy planning apparatus 3 ends. After that, the radiation therapy apparatus 4 irradiates the patient with radiation according to the data of this radiation therapy plan, and performs radiation therapy.

As described above, according to one embodiment, based on the radiation irradiation conditions, the dose rate distribution information representing the distribution of the dose rate in the irradiation route of the radiation is acquired, and based on the acquired dose rate distribution information, irradiation Acquire irradiation effect identification information that identifies the irradiation effect of the radiation in the path. Therefore, it is possible to clearly identify the irradiation effect of radiation in the irradiation path and prepare a radiation treatment plan. As a result, it is possible to provide a radiotherapy plan that suppresses damage to normal tissue and provides an appropriate irradiation effect.

Further, according to one embodiment, dose rate distribution information may be acquired based on radiation irradiation conditions and information representing the relationship between the irradiation depth of the radiation and the attenuation rate of the radiation. In this case, in addition to the effects described above, dose rate distribution information can be obtained more easily.

Further, according to one embodiment, the acquired irradiation effect identification information may be information for identifying the irradiation effect of radiation with a high dose rate for a short period of time. In this case, in addition to the effects described above, it is possible to acquire irradiation effect identification information for identifying the effects of FLASH irradiation.

Further, according to one embodiment, irradiation effect identification information may be acquired based on a comparison between the dose rate represented by the acquired dose rate distribution information and a predetermined threshold value. In this case, in addition to the effects described above, the irradiation effect identification information can be acquired according to the dose rate threshold.

Further, according to one embodiment, the acquired irradiation effect identification information is information for identifying, in the irradiation path, the first region where the radiation irradiation effect can be obtained and the second region where the radiation irradiation effect cannot be obtained. good too. In this case, in addition to the effects described above, it is possible to clearly distinguish between the first area where the irradiation effect is obtained and the second area where the irradiation effect is not obtained in the irradiation path.

Further, according to one embodiment, when there is normal tissue at a position corresponding to the second region, it may be possible to prompt the user to change the irradiation conditions. In this case, in addition to the effects described above, it is possible to change the irradiation conditions so as to exclude normal tissue from the second region where no irradiation effect can be obtained.

Further, according to one embodiment, when there is normal tissue at a position corresponding to the second region, it is determined whether or not the radiation dose exceeds the tolerable dose of the normal tissue, and information based on the determination result is obtained. You may make it notify. In this case, in addition to the effects described above, it can be confirmed that the normal tissue does not exceed the tolerable dose. In addition, it is possible to prevent normal tissue from exceeding the tolerable dose and entering the second region.

Further, according to one embodiment, the acquired irradiation effect identification information may be superimposed on the medical image of the subject and displayed on the display unit. In this case, in addition to the effects described above, the irradiation effect of radiation can be identified and displayed on the medical image.

Further, according to one embodiment, when the in-vivo target volume ITV of the tumor is specified from the medical image and the irradiation conditions are set, confirming whether the in-vivo target volume ITV of the tumor is located within the first region. becomes possible. In addition, since the in-vivo target volume ITV of the tumor includes a margin for in-vivo organ movement such as respiratory movement and peristalsis, it becomes possible to eliminate the need for control (gating) corresponding to body movement and respiratory movement.

Further, according to one embodiment, when there is a region in which a first region of one irradiation route and a second region of the other irradiation route overlap among a plurality of irradiation routes having different irradiation directions, the overlapping region A region may be identified as a second region where no irradiation effect is obtained. In this case, in addition to the effects described above, it is possible to prevent an error in identifying an area where the first area and the second area overlap as the first area.

In addition, you may implement one embodiment mentioned above like each of the following modifications.

[First modification of one embodiment]
A first modification of one embodiment is, as shown in FIGS. 9 to 11, a mode in which radiation other than the X-rays shown in FIG. 4 is irradiated. Specifically, one embodiment may be modified to a first modification of the configuration in which gamma rays, electron beams, proton beams, or carbon beams (not shown) are applied instead of X-rays.

FIG. 9 is a diagram showing an example of dose rate distribution in the depth direction corresponding to attenuation of radiation applicable to the radiotherapy planning apparatus 3 according to the first modified example of one embodiment. Of the radiation shown in FIG. 9, X-rays and gamma rays are electromagnetic waves, and electron beams and proton beams are particle beams. Carbon beams (not shown) may be applied as particle beams. In FIG. 9, the vertical axis is the relative dose [%]. The horizontal axis is the irradiation depth of radiation, specifically, the depth [cm] from the radiation incident position (body surface). The relative dose varies depending on the radiation attenuation (for example, attenuation rate) along the depth direction for each irradiation direction.

In FIG. 9, the higher the energy of X-rays and gamma rays, the deeper the dose peak reaches. Although the peak of the dose of electron beams reaches deeper as the energy is higher, unlike X-rays and gamma rays, they only reach a certain depth. A proton beam gives a high dose at the end of its range and exhibits a so-called Bragg peak. Since the various types of radiation shown in FIG. 9 are attenuated differently in the body, the depth at which the FLASH effect is obtained differs, as shown in FIGS. 10 and 11 .

For example, FIG. 10 shows depths D61 and D62 where the FLASH area FA and non-FLASH area NFA are separated by the attenuation of the 14 MeV electron beam and the 8 MeV electron beam in FIG. Depths D61 and D62 can be determined based on relative dose values (eg, 70%). Along with this, the FLASH area FA and the non-FLASH area NFA may be identified based on the depths D61 and D62 from the electron beam incident position, and the dose attenuation from the incident position (attenuation rate or relative dose value).

FIG. 11 shows depths D71 and D72 where the proton beam Bragg peak in FIG. 9 divides the FLASH area FA and the non-FLASH area NFA. Depths D71 and D72 can be determined based on relative dose values (eg, 70%).

In this case, both the region shallower than the depth D71 and the region deeper than the depth D72 are non-FLASH regions NFA. In other words, in FIG. 11, FLASH area FA is an area between depth D71 and depth D72.

Along with this, the FLASH area FA and the non-FLASH area NFA may be specified based on the depths D71 and D72 from the incident position of the proton beam, and are not limited to the depth of the Bragg peak. It may also be determined based on dose decay (decay rate or relative dose value).

Areas deeper than the depths D61 and D62 shown in FIG. 10 have dose rates lower than the dose rate of the FLASH irradiation, so the FLASH effect cannot be obtained and they become non-FLASH areas NFA. Such non-FLASH region NFAs may fail to reduce damage to normal tissue.

According to the first modification of the embodiment as described above, the same effect as that of the embodiment can be obtained even with the configuration for irradiating radiation other than the X-rays shown in FIG. 4 .

[Second modification of one embodiment]
A second modification of one embodiment is, as shown in FIG. 12, a form of irradiating X-rays in one irradiation direction.

Specifically, in step ST6, as shown in FIG. 12, the processing circuit 31 superimposes the dose rate distribution calculation result and the irradiation effect identification information identifying the FLASH area FA and the non-FLASH area NFA on the medical image g1. is displayed on the display device 33. In FIG. 12, in the substantially central portion of the medical image g1, the FLASH area FA is distributed from the body surface and the non-FLASH area NFA is distributed in a portion deeper than the FLASH area FA in the irradiation path of the irradiation direction "0 degree". . It is also possible to irradiate X-rays in three or more irradiation directions without being limited to the example shown in FIG.

According to the second modification of one embodiment as described above, even if the configuration is such that X-rays are emitted in one irradiation direction, the same effects as those of the first embodiment can be obtained. Note that the second modification may be combined with the first modification. That is, even if radiation other than X-rays is irradiated in one irradiation direction, the same effects as in the first embodiment can be obtained.

[Third modification of one embodiment]
A third modified example of one embodiment specifies the penumbra area in the irradiation path as the non-FLASH area NFA, and specifies the area other than the penumbra area (non-penumbra area) in the irradiation path as the FLASH area FA. The penumbra is radiation that has passed through an aperture that limits the irradiation field, and the aperture reduces the dose rate, so the FLASH effect cannot be obtained.

As an example of the third modified example, the processing circuit 31 specifies a penumbra area and a non-penumbra area by area designation by the operator for the irradiation path in the medical image. As another example, the processing circuit 31 identifies a penumbra area by area designation by the operator for the irradiation path in the medical image, and identifies areas other than the penumbra area in the irradiation path as the non-penumbra area. As another example, the processing circuit 31 identifies a non-penumbra area by the operator's area specification for the irradiation path in the medical image, and identifies areas other than the non-penumbra area in the irradiation path as the penumbra area. As another example, the processing circuitry 31 may identify a penumbra region and a non-penumbra region from within a predetermined region of the medical image based on parameters that define the irradiation field. Such a processing circuit 31 is an example of an irradiation effect identification information acquisition unit.

According to the third modified example of the embodiment as described above, the penumbra area in the irradiation path may be specified as the non-FLASH area NFA, and the area other than the penumbra area in the irradiation path may be specified as the FLASH area FA. , effects similar to those of one embodiment can be obtained. In addition to this, since the area other than the penumbra area in the irradiation path is specified as the FLASH area FA, the accuracy of specifying the FLASH area FA can be improved by removing the penumbra area.

[Fourth modification of one embodiment]
A fourth modification of one embodiment is based on at least one of the irradiation depth of radiation in the irradiation path, the radiation absorption characteristics of the tissue in the irradiation path, and the penumbra in the irradiation path. It is a form that specifies FA.

Specifically, the processing circuit 31 identifies a penumbra region and a non-penumbra region by area designation by the operator with respect to the irradiation path in the medical image. As another example, the processing circuit 31 identifies a penumbra area by area designation by the operator for the irradiation path in the medical image, and identifies areas other than the penumbra area in the irradiation path as the non-penumbra area. As another example, the processing circuit 31 identifies a non-penumbra area by the operator's area specification for the irradiation path in the medical image, and identifies areas other than the non-penumbra area in the irradiation path as the penumbra area. As another example, the processing circuit 31 may identify the penumbra region and the non-penumbra region in the irradiation path of the medical image based on the parameters that define the irradiation field.

Processing circuitry 31 then calculates a predicted dose rate for each pixel in the irradiation path based on the irradiation conditions. At this time, the processing circuit 31 calculates the predicted dose rate for the penumbra area by taking into consideration radiation attenuation according to the penumbra. Further, the processing circuit 31 calculates the predicted dose rate by considering at least one of the radiation attenuation rate according to the irradiation depth of the radiation in the irradiation path and the radiation attenuation rate according to the radiation absorption characteristics of the tissue. Depending on the irradiation depth, experimentally determined values may be used for the radiation attenuation rate and the radiation absorption characteristics of the tissue, or values obtained by predictive calculation may be used. The processing circuitry 31 identifies areas where the predicted dose rate is below the FLASH effect threshold as non-FLASH areas NFA, and identifies areas where the predicted dose rate is above the FLASH effect threshold as FLASH areas FA. The FLASH effect threshold is defined as the dose rate at which the FLASH effect is obtained. Such a processing circuit 31 is an example of an irradiation effect identification information acquisition unit.

According to the fourth modification of one embodiment as described above, based on at least one of the irradiation depth of the radiation in the irradiation path, the radiation absorption characteristics of the tissue in the irradiation path, and the penumbra in the irradiation path, the non- Even with a configuration that specifies the FLASH area NFA and the FLASH area FA, it is possible to obtain the same effects as in the embodiment. In addition, the accuracy of identifying non-FLASH areas NFA and FLASH areas FA can be improved depending on considerations of irradiation depth, radiation absorption properties of tissue, and penumbra.

[Fifth Modification of One Embodiment]
In a fifth modification of one embodiment, when transferring from step ST9 to ST11 shown in FIG. In this mode, the optimum irradiation condition is set as a definitive version from among the condition candidates.

Specifically, when the tolerable dose is not exceeded as a result of determination in step ST9, the processing circuit 31 acquires the latest irradiation condition set in step ST3 or ST10 as an irradiation condition candidate. Subsequently, the processing circuit 31 proceeds to step ST10, sets new irradiation conditions in the same manner as described above, and executes steps ST4 to ST9 in the same manner as described above based on the changed irradiation conditions. The loop from step ST10 through ST4 to ST9 and back to ST10 is repeatedly executed until a predetermined number of irradiation condition candidates are acquired.

If a predetermined number of irradiation condition candidates are acquired as a result of the determination in step ST9, the processing circuit 31 proceeds to step ST11 to select the optimum irradiation condition from among the predetermined number of irradiation condition candidates. confirm. As an optimum irradiation condition, for example, an irradiation condition that provides the lowest dose can be used.

According to the fifth modification of the embodiment as described above, the optimum irradiation condition is obtained from a predetermined number of irradiation condition candidates. can be obtained.

According to at least one embodiment described above, it is possible to provide a radiotherapy plan that suppresses damage to normal tissue and provides an appropriate irradiation effect.

The term "processor" used in the above description includes, for example, CPU, GPU, or Application Specific Integrated Circuit (ASIC), programmable logic device (for example, Simple Programmable Logic Device: SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). The processor realizes its functions by reading and executing the programs stored in the memory circuit. It should be noted that instead of storing the program in the memory circuit, the program may be directly installed in the circuit of the processor. In this case, the processor implements its functions by reading and executing the program embedded in the circuit. Also, functions corresponding to the program may be realized by combining logic circuits instead of executing the program. Note that each processor of the present embodiment is not limited to being configured as a single circuit for each processor, and may be configured as one processor by combining a plurality of independent circuits to realize its function. good. Furthermore, a plurality of components in FIGS. 1 and 2 may be integrated into one processor to realize its functions.

While several embodiments have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations of embodiments can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

1 Radiation therapy system 2 Medical image diagnosis device 3 Radiation therapy planning device 4 Radiation therapy device 31 Processing circuit 32 Storage device 33 Display device 34 Input device 35 Communication device 311 Dose rate distribution information acquisition function 312 Irradiation effect identification information acquisition function 313 Notification function 314 discrimination function 315 display control function

Claims (10)

A dose rate distribution information acquisition unit that acquires dose rate distribution information representing the distribution of the dose rate in the irradiation route of the radiation based on the irradiation conditions of the radiation;
an irradiation effect identification information acquisition unit that acquires irradiation effect identification information that identifies the irradiation effect of radiation in the irradiation route based on the acquired dose rate distribution information;
A radiotherapy planning device comprising: The dose rate distribution information acquisition unit acquires the dose rate distribution information based on the irradiation conditions of the radiation and information representing the relationship between the irradiation depth of the radiation and the attenuation rate of the radiation.
A radiotherapy planning apparatus according to claim 1 . The irradiation effect identification information acquired by the irradiation effect identification information acquisition unit is information that identifies the irradiation effect of radiation due to a high dose rate for a short time.
A radiotherapy planning apparatus according to claim 1 or 2. The irradiation effect identification information acquisition unit acquires the irradiation effect identification information based on a comparison between the dose rate represented by the acquired dose rate distribution information and a predetermined threshold,
A radiotherapy planning apparatus according to claim 1 or 2. The irradiation effect identification information acquired by the irradiation effect identification information acquisition unit is information for identifying, in the irradiation route, a first region where the irradiation effect of the radiation is obtained and a second region where the irradiation effect is not obtained. be,
A radiotherapy planning apparatus according to claim 1 or 2. A notification unit prompting a change of the irradiation condition when there is normal tissue at a position corresponding to the second region,
A radiotherapy planning apparatus according to claim 5 . a determination unit that determines, when there is normal tissue at a position corresponding to the second region, whether or not irradiation of the radiation exceeds a tolerable dose of the normal tissue;
A notification unit that notifies information based on the determined result,
A radiotherapy planning apparatus according to claim 5 . a display control unit that superimposes the irradiation effect identification information acquired by the irradiation effect identification information acquisition unit on a medical image of the subject and displays the information on a display unit;
A radiotherapy planning apparatus according to claim 1 or 2. 6. The irradiation effect identification information acquisition unit according to claim 5, wherein the penumbra region in the irradiation path is specified as the second region, and the region other than the penumbra region in the irradiation route is specified as the first region. Radiotherapy planning equipment. The irradiation effect identification information acquisition unit acquires the first region and the 6. A radiotherapy planning apparatus according to claim 5, wherein said second region is specified.

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