Radiation Treatment Planning Device

Abstract

To provide an appropriate radiation therapy plan while suppressing damage to a normal tissue region.SOLUTION: A radiation therapy planning device 3 includes: a region extraction unit 111 for extracting a tumor region and a normal tissue region included in a medical image; an irradiation plan creation unit 112 for acquiring reference information indicating a durable dose of the normal tissue region according to a lethal dose of the tumor region, a threshold of a dose rate at which the normal tissue region acquires an irradiation effect related to FLASH (ultra-high dose rate short time radiation irradiation), and a dose rate of a radioactive ray radiated to the normal tissue region, and creating an irradiation plan for the radioactive ray radiated to the tumor region and the normal tissue region on the basis of the reference information; and an information output unit 113 for outputting information based on the created irradiation plan.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The embodiments disclosed in this specification and the drawings relate to a radiation therapy planning system. [Background technology]

[0002] In recent years, a radiation therapy technique called FLASH (Flash-Activated Radiation Therapy) has been attracting attention. FLASH treats tumor sites by irradiating them with radiation at a dose rate (e.g., 40 Gy / s or higher) much higher than that used in conventional radiation therapy (e.g., about 0.03 Gy / s) for a short period of time (e.g., less than one second).

[0003] According to FLASH, normal tissues tend to be protected (not damaged) even when irradiated with a dose of radiation equivalent to that which would damage normal tissues in conventional radiation therapy. In other words, FLASH tends to protect normal tissues while maintaining the therapeutic effect on tumor sites, and is expected to reduce the side effects of radiation therapy. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2004-532671 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-78750 [Patent Document 3] Special Publication No. 2013-524956 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to minimize damage to normal tissue and provide an appropriate radiation therapy plan. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be considered as other problems. [Means for solving the problem]

[0006] The radiation therapy planning device of the embodiment includes: a site extraction unit that extracts a tumor site and a normal tissue site contained in a medical image; an irradiation plan creation unit that acquires reference information representing the lethal dose of the tumor site, the dose rate threshold at which the normal tissue site will obtain the irradiation effect related to FLASH (ultra-high dose rate short-duration radiation exposure), and the tolerable dose of the normal tissue site according to the dose rate of radiation irradiated to the normal tissue site, and creates an irradiation plan for radiation to be irradiated to the tumor site and the normal tissue site based on the acquired reference information; and an information output unit that outputs information based on the created irradiation plan. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a block diagram showing the configuration of a radiation therapy system according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the configuration of the radiation therapy planning device shown in FIG. [Figure 3] FIG. 3 is a diagram showing the configuration of a lethal dose table stored in a storage unit shown in FIG. 2. [Figure 4] 1(a) is a diagram showing the configuration of a tolerable dose table (FLASH) stored in the memory unit shown in Fig. 2. FIG. 1(b) is a diagram showing the configuration of a tolerable dose table (general radiation therapy) stored in the memory unit shown in Fig. 2. [Figure 5] FIG. 1 is a diagram showing radiation attenuation rate data. [Figure 6] 3 is a flowchart showing a process executed by the radiation therapy planning device shown in FIG. 2. [Figure 7](a) is a schematic diagram showing a tumor site included in a medical image, and (b) is a schematic diagram showing the radiation irradiation path. [Figure 8] FIG. 10 is a block diagram showing the configuration of a radiation therapy planning apparatus according to a second embodiment. [Figure 9] 9 is a flowchart showing a process executed by the radiation therapy planning device shown in FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Embodiment 1) The configuration of a radiation therapy system according to one embodiment will be described below with reference to the drawings. As shown in Fig. 1, the radiation therapy system 1 includes a medical image diagnostic apparatus 2, a radiation therapy planning apparatus 3, and a radiation therapy apparatus 4. The medical image diagnostic apparatus 2, the radiation therapy planning apparatus 3, and the radiation therapy apparatus 4 are connected to each other via a network so as to be able to communicate with each other.

[0009] The medical image diagnostic device 2 generates medical images for use in radiation therapy planning for a patient who is a radiation therapy target. The medical images may be two-dimensional images composed of two-dimensionally arranged pixels, or three-dimensional images composed of three-dimensionally arranged voxels. The medical image diagnostic device 2 may be any modality device capable of generating medical images. Examples of modality devices include an X-ray computed tomography (CT) device, a magnetic resonance imaging (MRI) device, a cone-beam CT device, and a nuclear medicine diagnostic device (PET: positron emission tomography, SPECT: single photon emission computed tomography).

[0010] The radiation therapy device 4 treats the patient by irradiating the patient with radiation in accordance with the radiation therapy plan created by the radiation therapy planning device 3. The radiation therapy device 4 is installed in a treatment room and has a treatment gantry and a treatment couch. The treatment couch moves its top plate so that the patient's treatment area (tumor area) is approximately aligned with the isocenter. The treatment gantry supports an irradiation head unit that is rotatable around a rotation axis. The irradiation head unit irradiates radiation in accordance with the treatment plan. Specifically, the irradiation head unit forms the radiation irradiation range using a multi-leaf collimator.

[0011] The radiation therapy planning device 3 creates a radiation therapy plan using medical images generated by the medical image diagnostic device 2. The radiation therapy planning device 3 provides the created radiation therapy plan to the radiation therapy device 4. The radiation therapy planning device 3 may store the created radiation therapy plan in a storage device (such as a server) on a network. In this case, the radiation therapy device 4 receives the radiation therapy plan created by the radiation therapy planning device 3 from the storage device. As shown in FIG. 2 , the radiation therapy planning device 3 includes a processing unit 11, a storage unit 12, a communication unit 13, an operation unit 14, and a display unit 15.

[0012] The communication unit 13 is composed of a communication interface device that performs communication via a network, such as a NIC (Network Interface Card). The communication unit 13 receives medical images transmitted from the medical image diagnostic apparatus 2 and supplies them to the processing unit 11. The communication unit 13 also transmits the radiation therapy plan received from the processing unit 11 to the radiation therapy apparatus 4.

[0013] The operation unit 14 is composed of an input interface device, such as a mouse, keyboard, trackball, switch, button, joystick, touchpad, touch panel display, etc. The operation unit 14 accepts various input operations by the user and supplies electrical signals corresponding to the accepted input operations to the processing unit 11.

[0014] The display unit 15 is configured with a display device such as a liquid crystal display (LCD), a cathode ray tube (CRT) display, an organic electroluminescence display (OLED), etc. The display unit 15 displays various information under the control of the processing unit 11.

[0015] The storage unit 12 is configured by a storage device such as a ROM (Read Only Memory), an HDD (Hard Disk Drive), an SSD (Solid State Drive), etc. The storage unit 12 also stores various programs and various data.

[0016] A lethal dose table is stored in the memory unit 12. As shown in FIG. 3, the lethal dose table shows the dose required to eliminate a tumor (lethal dose) for each type of tumor. The lethal dose is, for example, shown as a dose per unit volume. The lethal dose is also a measure of the tumor's radiosensitivity, and indicates, for example, a dose that will eliminate the tumor site with a probability of 95% or more. For example, if the tumor site to be treated is "lung cancer," the processing unit 11 refers to the lethal dose table and sets a dose (dose rate, irradiation time) that is equal to or greater than the lethal dose corresponding to "lung cancer."

[0017] The memory unit 12 also stores a tolerable dose table. The tolerable dose table indicates, for each organ, the radiation dose that a normal tissue site can withstand (tolerable dose). The tolerable dose is, for example, the dose per unit volume. The tolerable dose is a measure of the radiation sensitivity of a normal tissue site, and indicates the dose at which the irradiated radiation does not cause serious adverse events. Normal tissue sites also include risk organs whose survival rate decreases when radiation infiltrates the site. As shown in Figures 4(a) and 4(b), the tolerable dose table includes tables for FLASH and general radiotherapy.

[0018] The tolerable dose table for general radiation therapy shows the tolerable dose for each organ. On the other hand, the tolerable dose table for FLASH shows the radiation dose rate, tolerable irradiation time, and tolerable dose for each organ. FLASH tends to protect (not damage) normal tissue even when the normal tissue is irradiated with a dose of radiation equivalent to the dose (tolerable dose) that would damage the normal tissue in general radiation therapy (general radiation therapy). In other words, in FLASH radiation therapy, the risk of damage to the normal tissue varies depending on the radiation dose rate. In the tolerable dose table for FLASH, the tolerable dose for the normal tissue is set to a higher value as the dose rate increases. The tolerable irradiation time is determined based on the dose rate and the tolerable dose.

[0019] Furthermore, various data for determining the distribution of dose rates in a radiation irradiation path (beam path) are stored in the storage unit 12. For example, the storage unit 12 stores radiation absorption coefficient data, radiation attenuation rate data, penumbra region data, etc.

[0020] The radiation absorption coefficient data is data showing the radiation absorption coefficient, which indicates the proportion of energy absorbed by biological tissue per unit volume or unit length of the radiation that enters the tissue, for each biological tissue. The radiation attenuation rate data is data showing the relationship between the radiation irradiation depth and the attenuation rate of the dose. For example, as shown in FIG. 5, the dose of radiation such as electron beams attenuates depending on the depth inside the body to which the radiation is irradiated. In other words, the radiation irradiation effect differs because the dose rate changes between the position where the radiation enters the patient and the position where it exits. The penumbra is a region irradiated by radiation that passes through the peripheral portion of the aperture of a multi-leaf collimator in the radiation therapy device 4, and the dose rate is lower than that of radiation that passes through the center of the aperture. The penumbra data is data showing the relationship between the position and size of the aperture and the attenuation rate of radiation attenuated by the penumbra formed at the peripheral portion of the aperture.

[0021] The processing unit 11 is composed of processors such as a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). The processing unit 11 controls each unit of the radiation therapy planning device 3, thereby controlling the entire radiation therapy planning device 3. The processing unit 11 also functions as a site extraction unit 111, an irradiation plan creation unit 112, and an information output unit 113 by executing a program stored in the storage unit 12. Note that some or all of the functions 111 to 113 may be composed of an integrated circuit such as an ASIC (Application Specific Integrated Circuit).

[0022] The processing operations performed by the radiation therapy planning device 3 configured as above will be described below with reference to FIGS.

[0023] The region extraction unit 111 acquires a medical image generated by the medical image diagnostic device 2 (step ST1). The medical image is, for example, a three-dimensional CT image generated by an X-ray computed tomography device (CT device) here, but may be various medical images generated by a magnetic resonance imaging device (MRI), a cone-beam CT device, a nuclear medicine diagnostic device (PET, SPECT), etc. The region extraction unit 111 extracts a tumor region and a normal tissue region included in the medical image by performing a segmentation process on the acquired medical image (step ST2). Note that the region extraction unit 111 may extract the tumor region and the normal tissue region in response to a user operation via the operation unit 14.

[0024] The irradiation plan creation unit 112 acquires reference information representing the lethal dose of the tumor site, the dose rate threshold at which a normal tissue site achieves the irradiation effect related to FLASH (ultra-high dose rate short-time irradiation), and the tolerable dose of the normal tissue site according to the dose rate of radiation irradiated to the normal tissue site.The irradiation plan creation unit 112 creates an irradiation plan for radiation to be irradiated to the tumor site and the normal tissue site based on the acquired reference information.In this embodiment, an example will be described in which the irradiation plan creation unit 112 creates an irradiation plan using a forward planning method.The irradiation plan creation unit 112 includes an irradiation condition setting unit 112a and an irradiation condition evaluation unit 112b.

[0025] The irradiation condition setting unit 112a sets irradiation conditions for FLASH for the tumor site and normal tissue site extracted by the site extraction unit 111 (step ST3). For example, as shown in FIG. 7(a), the user checks the positional relationship between the tumor site and normal tissue site included in the medical image displayed on the display unit 15, and sets irradiation conditions for FLASH by referring to the lethal dose table and tolerable dose table displayed on the display unit 15. In response to the user's operation via the operation unit 14, the irradiation condition setting unit 112a sets, for example, the dose rate of radiation irradiated from the irradiation head unit of the radiotherapy device 4, the irradiation time, the incident position and incident direction (beam angle) of the radiation (beam), the aperture of a multi-leaf collimator (MLC), and the like, as shown in FIG. 7(b).

[0026] The irradiation condition evaluation unit 112b determines the dose of radiation to be irradiated to the tumor site and the dose rate and dose of radiation to be irradiated to the normal tissue site based on the irradiation conditions set by the irradiation condition setting unit 112a. The irradiation condition evaluation unit 112b also creates a radiation irradiation plan based on reference information representing the lethal dose of the tumor site, the dose rate threshold at which the normal tissue site achieves the irradiation effect related to FLASH (ultra-high dose rate short-time radiation exposure), and the tolerable dose of the normal tissue site according to the dose rate of radiation to be irradiated to the normal tissue site, the dose of radiation to be irradiated to the tumor site, and the dose rate and dose of radiation to be irradiated to the normal tissue site.

[0027] Specifically, the irradiation condition evaluation unit 112b determines the irradiation path (beam path) of radiation based on the irradiation conditions set by the irradiation condition setting unit 112a, and acquires the distribution of dose rates in the irradiation path (step ST4). The irradiation condition evaluation unit 112b reads various data such as radiation absorption coefficient data, radiation attenuation rate data, and penumbra region data stored in the storage unit 12, and determines the attenuation rate of radiation in the irradiation path based on the read various data, the acquired medical image, and the set irradiation conditions, and acquires the distribution of dose rates in the irradiation path based on the attenuation rate of radiation. The irradiation condition evaluation unit 112b acquires the distribution of dose rates per unit volume.

[0028] Specifically, the irradiation condition evaluation unit 112b determines the attenuation rate of radiation according to the irradiation depth of the irradiation path by referring to the radiation attenuation rate data. Furthermore, the irradiation condition evaluation unit 112b identifies biological tissues such as tumor sites and normal tissue sites in the radiation irradiation path. The irradiation condition evaluation unit 112b determines the attenuation rate of radiation according to the radiation absorption coefficient of the biological tissue identified in the irradiation path by referring to the radiation absorption coefficient data. Note that the attenuation rate of radiation according to the radiation absorption coefficient of the biological tissue is determined taking into account the size (volume, length) of the biological tissue included in the irradiation path. Furthermore, the irradiation condition evaluation unit 112b determines the penumbra region corresponding to the peripheral portion of the opening of the multi-leaf collimator of the radiation therapy device 4. The irradiation condition evaluation unit 112b determines the attenuation rate of radiation according to the penumbra region in the irradiation path by referring to the penumbra region data.

[0029] The irradiation condition evaluation unit 112b integrates the radiation attenuation rates corresponding to the irradiation depth, radiation absorption coefficient, and penumbra region, and acquires the dose rate distribution in the irradiation path based on the integrated attenuation rate. Note that the irradiation condition evaluation unit 112b may calculate the dose rate distribution in the radiation irradiation path based on various data such as radiation absorption coefficient data, radiation attenuation rate data, and penumbra region data, the acquired medical image, the set irradiation conditions, and a predetermined dose calculation algorithm. Examples of the predetermined dose calculation algorithm include the Monte Carlo method, the equivalent Tissue-Air Ratio (TAR) method, the differential scattered air dose ratio method, the microvolume method, and the convolution method.

[0030] The irradiation condition evaluation unit 112b may also use a trained model that has been subjected to machine learning so as to output a dose rate distribution in a radiation irradiation path in response to input of a medical image and irradiation conditions. In this case, the irradiation condition evaluation unit 112b may read out the trained model stored in the storage unit 12 and input the medical image and radiation irradiation conditions into the trained model to obtain the dose rate distribution in a radiation irradiation path output from the trained model.

[0031] Based on the distribution of dose rates in the irradiation path thus obtained (information obtained based on the irradiation conditions), the irradiation condition evaluation unit 112b determines the dose of radiation to be irradiated to the tumor site, and the dose rate and dose of radiation to be irradiated to the normal tissue site.

[0032] The irradiation condition evaluation unit 112b calculates the dose of radiation to be irradiated to the tumor site and evaluates the irradiation effect on the tumor site (step ST5). Specifically, the irradiation condition evaluation unit 112b acquires the distribution of dose rates at the tumor site included in the irradiation path from the distribution of dose rates acquired in step ST4. The irradiation condition evaluation unit 112b also acquires the irradiation time for irradiating the tumor site based on the radiation irradiation conditions set in step ST3. The irradiation condition evaluation unit 112b calculates the distribution of doses to be irradiated to the tumor site from the distribution of dose rates at the tumor site and the irradiation time. The irradiation condition evaluation unit 112b reads the lethal dose table shown in FIG. 3 from the storage unit 12 and identifies whether the irradiation dose exceeds the lethal dose associated with the type of tumor site.

[0033] The irradiation condition evaluation unit 112b distinguishes between regions where the radiation dose irradiated to the tumor site exceeds the lethal dose and regions where the radiation dose is equal to or less than the lethal dose, based on the distribution of the radiation dose irradiated to the tumor site. The irradiation condition evaluation unit 112b assigns identification information indicating that the radiation dose is sufficient to regions where the radiation dose exceeds the lethal dose, and assigns identification information indicating that the radiation dose is insufficient to regions where the radiation dose is equal to or less than the lethal dose.

[0034] The irradiation condition evaluation unit 112b may superimpose information on the medical image, for example, by surrounding an area showing a distribution exceeding the lethal dose with a blue line, to visually indicate that the irradiation dose in that area is sufficient, and display the superimposed information on the display unit 15. The irradiation condition evaluation unit 112b may superimpose information on the medical image, for example, by surrounding an area showing a distribution below the lethal dose with a purple line, to visually indicate that the irradiation dose in that area is insufficient, and display the superimposed information on the medical image, for example, by surrounding an area showing a distribution below the lethal dose with a purple line. Note that the lethal dose table shown in FIG. 3 may also indicate the lethal dose and lethal irradiation time according to the dose rate. The irradiation condition evaluation unit 112b assigns identification information indicating that the irradiation dose is sufficient to areas showing a distribution below the lethal dose that correspond to each dose rate shown in the distribution of the tumor site, and assigns identification information indicating that the irradiation is insufficient to areas showing a distribution below the lethal dose. In this way, the irradiation effect on the tumor site is evaluated.

[0035] As another method for assigning identification information, the irradiation condition evaluation unit 112b may calculate the ratio of the area of ​​the tumor site where the dose exceeds the lethal dose to the area where the dose is below the lethal dose, and assign identification information to the tumor site that identifies whether the dose exceeds the lethal dose or not, based on that ratio.

[0036] The irradiation condition evaluation unit 112b also calculates the dose rate and dose of radiation to be irradiated to the normal tissue site, and evaluates the irradiation effect on the normal tissue site. Specifically, the irradiation condition evaluation unit 112b acquires the dose rate and irradiation time of radiation to be irradiated to the normal tissue site included in the irradiation path (step ST6). If the irradiation path includes multiple normal tissue sites, the irradiation condition evaluation unit 112b selects one normal tissue site from the multiple normal tissue sites. The irradiation condition evaluation unit 112b acquires the distribution of the dose rate of the selected normal tissue site. The irradiation condition evaluation unit 112b also acquires the irradiation time for irradiation to the selected normal tissue site based on the radiation irradiation conditions set in step ST3.

[0037] The irradiation condition evaluation unit 112b determines whether the dose rate of radiation irradiated to the selected normal tissue region is equal to or greater than a threshold value for achieving the FLASH irradiation effect, based on the distribution of the dose rate (step ST7). It is known that the effect of FLASH can be achieved at a high dose rate, for example, 40 Gy / s or greater. If radiation below this dose rate is irradiated to the normal tissue region, the normal tissue region may not be protected (may be damaged). The irradiation condition evaluation unit 112b distinguishes between regions of the selected normal tissue region that show a distribution of dose rates below a threshold value (for example, 40 Gy / s) (regions where the FLASH effect is not achieved) and regions that show a distribution of dose rates above the threshold value (regions where the FLASH effect is achieved).

[0038] The irradiation condition evaluation unit 112b also determines whether the tolerable dose of the selected normal tissue region is exceeded based on the dose rate distribution and irradiation time of the selected normal tissue region (step ST8). Specifically, the irradiation condition evaluation unit 112b reads the tolerable dose table shown in FIG. 4(a) from the storage unit 12. In FLASH radiation therapy, the risk of damage to the normal tissue region varies depending on the radiation dose rate. That is, even if radiation is irradiated at a dose rate equal to or higher than a threshold value (e.g., 40 Gy / s) in step ST6, it is necessary to determine whether the radiation dose rate and irradiation time exceed the tolerable dose of the normal tissue region corresponding to the dose rate. The irradiation condition evaluation unit 112b distinguishes between regions of the normal tissue region that can withstand FLASH irradiation and regions that cannot withstand FLASH irradiation based on the dose rate and irradiation time of the radiation irradiated to the selected normal tissue region and the tolerable dose corresponding to the dose rate.

[0039] The irradiation condition evaluation unit 112b evaluates the irradiation effect on the normal tissue site selected in step ST6 based on the identification results of steps ST7 and ST8. Specifically, the irradiation condition evaluation unit 112b assigns identification information (e.g., information indicating a low risk of irradiation) identifying that irradiation of radiation related to FLASH can be performed normally to a region of the selected normal tissue site that is identified as a region where the effect of FLASH can be obtained and that can withstand FLASH irradiation (step ST7; Yes, step ST8; No) (step ST9). The irradiation condition evaluation unit 112b may superimpose visually identifiable information indicating that the region can be irradiated on the medical image on the display unit 15, for example by surrounding the region of the normal tissue site with a green line.

[0040] On the other hand, for a region of the selected normal tissue site that is identified as not being effective with FLASH or as being unable to withstand FLASH irradiation (step ST7; No, step ST8; Yes), the irradiation condition evaluation unit 112b assigns identification information (e.g., information indicating a high risk of irradiation) that identifies that radiation related to FLASH cannot be normally irradiated (step ST10). The irradiation condition evaluation unit 112b may superimpose visually identifiable information that the region cannot be irradiated on the medical image, for example by surrounding the region of the normal tissue site with a red line, and display the superimposed information on the display unit 15. In this way, the irradiation effect on the normal tissue site selected in step ST6 is evaluated.

[0041] In addition, the irradiation condition evaluation unit 112b may calculate the ratio of areas with low irradiation risk to areas with high irradiation risk in a normal tissue area, and output, in an identifiable manner, whether or not radiation related to FLASH can be normally irradiated to the normal tissue area based on that ratio.

[0042] Thereafter, the irradiation condition evaluation unit 112b determines whether or not there are other normal tissue areas in the irradiation path (step ST11), and if it determines that there are, selects the other normal tissue areas and performs the processing of steps ST6 to ST10 again (step ST11; Yes).

[0043] Through the above process, the irradiation conditions set in step ST3 are evaluated. The irradiation plan creation unit 112 displays information representing the evaluation result of the irradiation conditions by the irradiation condition evaluation unit 112b on the display unit 15. Based on this information, the user checks whether there are any areas in the normal tissue region where the FLASH effect is not obtained, any areas that cannot withstand the FLASH irradiation, or any areas where the dose to the tumor region is insufficient, and determines whether it is necessary to set other irradiation conditions. When the irradiation plan creation unit 112 determines that it is necessary to set other irradiation conditions in response to the user's operation via the operation unit 14, the process returns to step ST3 and resets the irradiation conditions (step ST12; Yes).

[0044] On the other hand, when the irradiation plan creation unit 112 determines that setting of other irradiation conditions is not necessary in response to the user's operation via the operation unit 14, it creates a radiation irradiation plan based on the irradiation conditions evaluated by the irradiation condition evaluation unit 112b (step ST13). The information output unit 113 outputs information based on the irradiation plan created by the irradiation plan creation unit 112 to the storage unit 12 and the display unit 15. Furthermore, the information output unit 113 outputs information based on the irradiation plan created by the irradiation plan creation unit 112 to the radiation therapy apparatus 4 via the communication unit 13 in response to the user's operation via the operation unit 14.

[0045] According to the above processing operations, the radiation therapy planning device 3 can distinguishably display the irradiation effects on the tumor site and the irradiation effects on the normal tissue site based on the set irradiation conditions, thereby providing an appropriate radiation therapy plan. In particular, with regard to the irradiation effects on the normal tissue site, it is possible to distinguish between areas in the normal tissue site where the FLASH effect can be achieved and areas where the FLASH effect cannot be achieved based on the distribution of the dose rate of the radiation irradiated to the normal tissue site. Furthermore, taking into account the risk of damage to the normal tissue site depending on the radiation dose rate, it is possible to distinguish between areas that can withstand FLASH irradiation and areas that cannot withstand FLASH irradiation based on the dose rate and irradiation time of the radiation irradiated to the normal tissue site and the tolerable dose corresponding to the dose rate.

[0046] In the above embodiment, in steps ST9 and ST10, an example was described in which identification information identifying whether radiation related to FLASH can be irradiated normally is assigned to a normal tissue area. However, the irradiation condition evaluation unit 112b may assign identification information identifying whether the dose rate is above a threshold (information identifying whether the effect of FLASH can be obtained) and identification information identifying whether the dose rate exceeds the tolerable dose of the normal tissue area (information identifying whether the normal tissue area can withstand FLASH irradiation) individually to the corresponding area of ​​the normal tissue area or the normal tissue area.

[0047] In the above embodiment, an example has been described in which it is determined in step ST12 whether or not setting of other irradiation conditions is necessary in response to a user operation. However, the irradiation plan creation unit 112 may automatically confirm the irradiation conditions set in step ST3 in response to the evaluation result of the irradiation conditions by the irradiation condition evaluation unit 112b, and may display a notification to that effect on the display unit 15. Furthermore, the irradiation plan creation unit 112 may display a notification on the display unit 15 prompting the user to reset the irradiation conditions set in step ST3 in response to the evaluation result of the irradiation conditions by the irradiation condition evaluation unit 112b. For example, when the irradiation condition evaluation unit 112b identifies an area in the normal tissue region where the FLASH effect cannot be obtained or an area that cannot withstand FLASH irradiation (step ST7; No or step ST8; Yes), the irradiation condition evaluation unit 112b may return to step ST3 and display a notification on the display unit 15 prompting the user to reset the irradiation conditions. In this case, in step ST12, the user confirms that the FLASH effect can be obtained in all areas of the normal tissue region. Even in this case, the irradiation plan creation unit 112 may accept a user operation via the operation unit 14 and determine whether or not it is necessary to set other irradiation conditions in accordance with the user operation.

[0048] In the above embodiment, an example in which the irradiation conditions for FLASH are reset as other irradiation conditions has been described. However, instead of the irradiation conditions for FLASH, irradiation conditions for general radiation therapy (general radiation therapy) may be set. In this case, the irradiation condition setting unit 112a creates irradiation conditions (irradiation plan) for general radiation therapy, as in the conventional method, so as to minimize the radiation dose irradiated to normal tissues and irradiate the tumor site with radiation. The irradiation condition evaluation unit 112b acquires the dose distribution in the radiation irradiation path (beam path) based on the set irradiation conditions and calculates the radiation dose irradiated to the tumor site and normal tissues. The irradiation condition evaluation unit 112b reads the lethal dose table for the tumor site from the storage unit 12 and determines whether the radiation dose irradiated to the tumor site exceeds the lethal dose. The irradiation condition evaluation unit 112b also reads the tolerable dose table shown in FIG. 4(b) from the storage unit 12 and determines whether the radiation dose irradiated to the normal tissue site exceeds the tolerable dose. The irradiation plan creation unit 112 displays on the display unit 15 information indicating the evaluation result of the irradiation conditions related to general radiotherapy by the irradiation condition evaluation unit 112b.

[0049] Furthermore, the irradiation plan creation unit 112 may automatically reset the irradiation conditions set in step ST3 and evaluate the reset irradiation conditions (or may simulate the irradiation effect) depending on the evaluation results of the irradiation conditions by the irradiation condition evaluation unit 112b.

[0050] In addition, in the above embodiment, for the sake of convenience of explanation, the number of irradiations and the number of incident directions are not mentioned, but irradiation conditions including the number of irradiations and the number of incident directions may be set in step ST3. In this case, the irradiation plan creation unit 112 acquires irradiation information representing the distribution of the dose rate and irradiation time of the radiation irradiated to the normal tissue site, taking into account the number of treatments and the number of incident directions.

[0051] In the above embodiment, the dose rate threshold for obtaining the FLASH irradiation effect is set uniformly (40 Gy / s), but the dose rate threshold for obtaining the FLASH irradiation effect may be set for each organ. In this case, the irradiation condition evaluation unit 112b distinguishes, based on the threshold corresponding to the organ represented by the selected normal tissue site, a region showing a distribution of dose rates below the threshold (a region where the FLASH effect is not obtained) from a region showing a distribution of dose rates equal to or greater than the threshold (a region where the FLASH effect is obtained).

[0052] Furthermore, although the example in which the irradiation condition evaluation unit 112b uses the tolerable dose table related to FLASH shown in FIG. 4(a) has been described, the tolerable dose and tolerable irradiation time corresponding to a dose rate may be obtained by interpolating the tolerable dose and tolerable irradiation time by calculation for a dose rate not shown in the tolerable dose table.

[0053] Moreover, the irradiation plan creation unit 112 may create an irradiation plan for FLASH and an irradiation plan for general radiotherapy separately and display them on the display unit 15. For example, by displaying an irradiation plan for FLASH and an irradiation plan for general radiotherapy side by side on the display unit 15, the user can easily compare the irradiation plan for FLASH with the irradiation plan for general radiotherapy.

[0054] Furthermore, the irradiation plan creation unit 112 may create an irradiation plan that combines FLASH-related irradiation with general radiotherapy-related irradiation, or an irradiation plan that combines multiple FLASH-related irradiations. For example, the irradiation plan creation unit 112 may create an irradiation plan that combines a low FLASH irradiation plan based on a dose rate (e.g., about 50 Gy / s) close to the threshold dose rate for obtaining the FLASH-related irradiation effect, and a high FLASH irradiation plan based on a dose rate (e.g., about 500 Gy / s) far exceeding the threshold dose rate for obtaining the FLASH-related irradiation effect.

[0055] (Embodiment 2) In the first embodiment, the irradiation plan creation unit 112 sets the irradiation conditions related to FLASH in response to the user's operation via the operation unit 14, and creates an irradiation plan by the forward planning method. However, in the present embodiment, an example will be described in which an irradiation plan is automatically created by the inverse planning method.

[0056] For example, as shown in FIG. 8, the processing unit 11 executes a program stored in the storage unit 12 to function as a region extraction unit 111, an irradiation plan creation unit 112, and an information output unit 113.

[0057] Hereinafter, the processing operations performed by the radiation therapy planning device 3 will be described with reference to FIG.

[0058] The region extraction unit 111 acquires a medical image generated by the medical image diagnostic device 2 (step ST21), and extracts a tumor region and a normal tissue region included in the medical image (step ST22).

[0059] The irradiation plan creation unit 112 acquires reference information representing the lethal dose of the tumor site, the dose rate threshold (e.g., 40 Gy / s) at which a normal tissue site achieves the irradiation effect related to FLASH (ultra-high dose rate short-time radiation exposure), and the tolerable dose of the normal tissue site according to the dose rate of radiation irradiated to the normal tissue site. Based on the acquired reference information, the irradiation plan creation unit 112 creates an irradiation plan for radiation to be irradiated to the tumor site and the normal tissue site.

[0060] Specifically, the irradiation plan creation unit 112 reads out the lethal dose table shown in Figure 3 from the memory unit 12, obtains the lethal dose associated with the type of tumor site extracted in step ST22, and sets a target dose (first standard) equal to or greater than the lethal dose for the tumor site (step ST23).

[0061] In addition, the irradiation plan creation unit 112 sets the target dose rate (second standard) of radiation to be irradiated to the normal tissue area extracted in step ST22 to a dose rate threshold value (e.g., 40 Gy / s) or higher that achieves the irradiation effect related to FLASH (step ST24).

[0062] Furthermore, the irradiation plan creation unit 112 sets the target dose (third criterion) for the normal tissue site extracted in step ST22 to a value equal to or less than the tolerable dose corresponding to the dose rate of the radiation irradiated to the normal tissue site (step ST25). Note that, if there are multiple normal tissue sites extracted in step ST22, the irradiation plan creation unit 112 sets the target dose (third criterion) for each normal tissue site.

[0063] The irradiation plan creating unit 112 creates irradiation conditions (irradiation plan) for FLASH that satisfy the set first to third criteria (step ST26). For example, the irradiation plan creating unit 112 sets a plurality of irradiation conditions, simulates the irradiation effect for FLASH for each set irradiation condition, and, as a result, determines optimal irradiation conditions (irradiation plan) that satisfy the first to third criteria. As a result, the irradiation plan creating unit 112 can obtain radiation irradiation conditions (irradiation plan) such that the dose of radiation irradiated to the tumor site is equal to or greater than the lethal dose for the tumor site, the dose rate of radiation irradiated to normal tissue sites is equal to or greater than the dose rate threshold (40 Gy / s) for achieving the irradiation effect for FLASH, and the dose of radiation irradiated to normal tissue sites is equal to or less than the tolerable dose corresponding to the dose rate of radiation irradiated to the normal tissue sites.

[0064] The information output unit 113 outputs information based on the irradiation plan created by the irradiation plan creation unit 112 to the storage unit 12 and the display unit 15. Specifically, the information output unit 113 superimposes identification information for identifying the irradiation effect on the tumor site and the normal tissue site (identification information indicating that the tumor site is sufficiently irradiated, identification information indicating that the risk of irradiation on the normal tissue site is low, etc.) on the medical image and displays it on the display unit 15. Furthermore, the information output unit 113 may output information based on the irradiation plan created by the irradiation plan creation unit 112 to the radiation therapy apparatus 4 via the communication unit 13 in response to a user operation via the operation unit 14.

[0065] The irradiation plan creation unit 112 may use a trained model that has been subjected to machine learning so as to output FLASH-related irradiation conditions (irradiation plan) that satisfy the first to third criteria by inputting the tumor site and normal tissue site. In this case, the irradiation plan creation unit 112 may read out the trained model stored in the storage unit 12, and input the tumor site and normal tissue site extracted from the medical image to the trained model, thereby setting the FLASH-related irradiation conditions output from the trained model.

[0066] The irradiation plan creation unit 112 may create a plurality of irradiation conditions (irradiation plans) that satisfy the first to third criteria. In this case, the information output unit 113 outputs a list of irradiation conditions to the display unit 15. The information output unit 113 selects one irradiation condition (irradiation plan) from the list in response to a user operation via the operation unit 14, and determines the irradiation plan.

[0067] Furthermore, the region extraction unit 111 may specify at least one of the tumor region and the normal tissue region based on a user operation via the operation unit 14. The irradiation plan creation unit 112 may acquire irradiation conditions related to FLASH that satisfy the first to third criteria for the tumor region or the normal tissue region specified based on the operation.

[0068] Alternatively, the irradiation plan creation unit 112 may create a treatment plan for general radiation therapy (general radiation therapy). In this case, the irradiation plan creation unit 112 creates irradiation conditions (irradiation plan) for general radiation therapy so that the dose of radiation irradiated to normal tissue sites is minimized and radiation is irradiated to the tumor site, as in the conventional case.

[0069] Moreover, the irradiation plan creation unit 112 may create an irradiation plan for FLASH and an irradiation plan for general radiotherapy separately and display them on the display unit 15. For example, by displaying an irradiation plan for FLASH and an irradiation plan for general radiotherapy side by side on the display unit 15, the user can easily compare the irradiation plan for FLASH with the irradiation plan for general radiotherapy.

[0070] Furthermore, the irradiation plan creation unit 112 may create an irradiation plan that combines FLASH-related irradiation with general radiotherapy-related irradiation, or an irradiation plan that combines multiple FLASH-related irradiations. For example, the irradiation plan creation unit 112 may create an irradiation plan that combines a low FLASH irradiation plan based on a dose rate (e.g., about 50 Gy / s) close to the threshold dose rate for obtaining the FLASH-related irradiation effect, and a high FLASH irradiation plan based on a dose rate (e.g., about 500 Gy / s) far exceeding the threshold dose rate for obtaining the FLASH-related irradiation effect.

[0071] According to at least one of the embodiments described above, it is possible to provide a radiation therapy plan that can suppress damage to normal tissue sites and obtain an appropriate irradiation effect.

[0072] The term "processor" used in the above description refers to a circuit such as a CPU, a GPU, an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). A processor realizes its functions by reading and executing a program stored in a memory circuit. Note that instead of storing a program in a memory circuit, the processor may be configured so that the program is directly embedded in the circuit. In this case, the processor realizes its functions by reading and executing the program embedded in the circuit. Furthermore, instead of executing a program, a function corresponding to the program may be realized by a combination of logic circuits. Note that each processor in this embodiment is not limited to being configured as a single circuit for each processor, but may also be configured as a single processor by combining multiple independent circuits to realize its functions.

[0073] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations of embodiments can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0074] 1. Radiation therapy system 2 Medical imaging diagnostic equipment 3 Radiation treatment planning device 4 Radiation therapy equipment 11 Processing section 111 Part extraction part 112 Irradiation Planning Department 112a Irradiation condition setting section 112b Irradiation condition evaluation section 113 Information output section 12 Storage section 13 Communications Department 14 Control section 15 Display section

Claims

1. a region extraction unit that extracts tumor regions and normal tissue regions included in a medical image; an irradiation plan creation unit that acquires reference information that represents a lethal dose of the tumor site, a dose rate threshold at which the normal tissue site achieves an irradiation effect related to FLASH (ultra-high dose rate short-time irradiation), and a tolerable dose of the normal tissue site according to the dose rate of radiation irradiated to the normal tissue site, and creates an irradiation plan for radiation to be irradiated to the tumor site and the normal tissue site based on the acquired reference information; An information output unit that outputs information based on the created irradiation plan, Radiation treatment planning equipment.

2. The irradiation plan creation unit an irradiation condition setting unit that sets irradiation conditions for FLASH for the tumor site and the normal tissue site extracted by the site extraction unit; an irradiation condition evaluation unit that calculates a dose of radiation to be irradiated to the tumor site and a dose rate and a dose of radiation to be irradiated to the normal tissue site based on the irradiation conditions set by the irradiation condition setting unit, the irradiation condition evaluation unit creates the irradiation plan based on the reference information, the dose of radiation to be irradiated to the tumor site, and the dose rate and dose of radiation to be irradiated to the normal tissue site. The radiation therapy planning system of claim 1 .

3. the irradiation condition evaluation unit identifies whether a tolerable dose or a tolerable irradiation time corresponding to the dose rate is exceeded based on the dose rate distribution and the irradiation time. The radiation therapy planning system according to claim 2 .

4. the irradiation condition evaluation unit identifies whether or not a dose rate included in the irradiation information is equal to or greater than a dose rate at which the effect of FLASH can be obtained; The radiation therapy planning system according to claim 2 .

5. the irradiation condition evaluation unit determines an irradiation path of the radiation based on the irradiation conditions and acquires a distribution of dose rates in the irradiation path. The radiation therapy planning system according to any one of claims 2 to 4.

6. the irradiation condition evaluation unit calculates an attenuation rate of the radiation in the irradiation path, and acquires a dose rate distribution in the irradiation path based on the attenuation rate of the radiation. The radiation therapy planning system according to claim 5 .

7. the irradiation condition evaluation unit calculates an attenuation rate of radiation according to the irradiation depth of the irradiation path. The radiation therapy planning system according to claim 5 .

8. the irradiation condition evaluation unit calculates an attenuation rate of radiation according to a radiation absorption coefficient of living tissue in the irradiation path. The radiation therapy planning system according to claim 5 .

9. the irradiation condition evaluation unit calculates an attenuation rate of radiation according to a penumbra region in the irradiation path. The radiation therapy planning system according to claim 5 .

10. the irradiation condition evaluation unit determines a plurality of the irradiation conditions; the information output unit outputs a list of the plurality of irradiation conditions. The radiation therapy planning system according to any one of claims 2 to 9.

11. the region extraction unit extracts at least one of the tumor region and the normal tissue region based on a user operation; The radiation therapy planning system according to any one of claims 1 to 10.

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