Method and computing system for computer-implemented radiation therapy planning

Abstract

Embodiments of the present disclosure relate to a method and a computing system for computer-implemented radiation therapy planning. Radiation therapy planning includes: accessing values ​​of parameters, such as the number of beams to be directed into subvolumes in a target, beam directions, and beam energies. Accessing information specifying limitations of the radiation therapy plan. The limitations include limitations on the irradiation time of each subvolume outside the target. Other limitations may include limitations on the irradiation time of each subvolume in the target, limitations on the dose rate of each subvolume in the target, and limitations on the dose rate of each subvolume outside the target. Adjusting the values ​​of the parameters until the irradiation time of each subvolume outside the target meets the maximum limit on the irradiation time.

Description

[0001] This application is a divisional application of an invention patent application with an international filing date of July 19, 2018 (priority date of July 21, 2017), which entered the Chinese national stage on November 27, 2019, and has a Chinese national application number of 201880035174.8 and is named “Dosage Aspects of Radiation Therapy Planning and Treatment”. Technical Field

[0002] The present disclosure relates generally to the mounting and stabilization of components within a digital image capture device (DICD), and more particularly to the mounting and stabilization of an integrated sensor lens assembly (ISLA) and an inertial measurement unit (IMU). Background Art

[0003] The use of radiation therapy to treat cancer is well known. Typically, radiation therapy involves directing a beam of high-energy proton, photon, ion or electron radiation ("therapeutic radiation") into a target or target volume (eg, a tumor or lesion).

[0004] Before a patient is treated with radiation, a treatment plan specific to that patient is developed. The plan defines various aspects of the therapy using simulations and optimization based on past experience. Overall, the goal of the treatment plan is to deliver enough radiation to the target while minimizing exposure of surrounding normal healthy tissue to the radiation.

[0005] The goal of the planner is to find the best solution with respect to multiple clinical goals that may be conflicting in the sense that improvements toward one goal may have an adverse effect on achieving another goal. For example, a treatment plan that spares the liver from receiving a certain dose of radiation may result in the stomach receiving too much radiation. These types of trade-offs lead to an iterative process in which the planner develops different plans to find the one that is best suited to achieve the desired outcome.

[0006] Recent radiation biology studies have demonstrated the utility of delivering a relatively high therapeutic radiation dose to a target in a single, brief period of time. This type of instruction is generally referred to herein as FLASH radiation therapy (FLASH RT). Evidence to date indicates that FLASH RT advantageously protects normal healthy tissue from damage when it is exposed to only a single irradiation for only a very brief period of time. FLASH RT therefore introduces important constraints that are not considered or achieved in conventional radiation therapy plans. Summary of the invention

[0007] In intensity modulated radiation therapy (IMRT), such as intensity modulated particle therapy (IMPT), the beam intensity varies across a treatment region (target) within a patient. Depending on the treatment modality, the degrees of freedom available for intensity modulation include beam shaping (collimation), beam weighting (spot scanning), and angle of incidence (which may be referred to as beam geometry). These degrees of freedom result in a virtually unlimited number of potential treatment plans, and thus the consistent and efficient generation and evaluation of high-quality treatment plans is beyond human capabilities and relies on the use of computing systems, particularly in light of the time constraints associated with the use of radiation therapy to treat ailments like cancer and the large number of patients who are undergoing radiation therapy or who need to undergo radiation therapy during any given period of time.

[0008] According to an embodiment of the present invention, an improved radiation therapy planning method for FLASH radiation therapy (FLASH RT) is provided, as well as an improved radiation therapy based on such a plan. In an embodiment, the value of a parameter is accessed, such as the number of beams to be guided into a subvolume in a target and across a subvolume, the direction of the beam (e.g., a gantry angle relative to a patient or a target, or a nozzle direction relative to a patient or a target), and the beam energy of the beam. The direction is determined to minimize the amount of overlap of the path of the beam outside the target, or to minimize the path of the beam outside the target. The beams may or may not overlap within the target. The beam may be a proton beam, an electron beam, a photon beam, an ion beam, or a nuclear beam (e.g., carbon, helium, and lithium).

[0009] In an embodiment, the radiation therapy plan includes: accessing values ​​of parameters such as the number of beams to be directed into the subvolumes in the target, the beam direction, and the beam energy. Accessing information specifying constraints of the radiation therapy plan. In an embodiment, the constraints are based on a dose threshold and include a maximum limit on the irradiation time of each subvolume outside the target. The dose threshold may depend on the tissue type. Other constraints may include a maximum limit on the irradiation time of each subvolume in the target, a minimum limit on the dose rate of each subvolume in the target, and a minimum limit on the dose rate of each subvolume outside the target. In an embodiment, the values ​​of the parameters are adjusted until the irradiation time of each subvolume outside the target meets the maximum limit on the irradiation time.

[0010] In an embodiment, the portion of each beam within the target is represented as a set of corresponding longitudinal beam regions. Each beam region in each group has a value corresponding to the calculated amount of dose to be delivered by the beam region. For a proton beam or ion beam having a Bragg peak, the value assigned to the beam region corresponding to the Bragg peak of the beam is greater than other values ​​assigned to other beam regions. If two or more beams overlap within the target, one or more subvolumes within the target will receive doses from more than one beam. For each subvolume in the target, the values ​​assigned to the beam regions that overlap in the subvolume are added together to determine the total value of the subvolume; if only one beam region reaches a particular subvolume, the total value is the value of that beam region. Adjust the calculated amount of dose that affects the beam region to be delivered until the total values ​​of the subvolumes are within a specified range of each other or are the same, indicating that the dose to be delivered across the target is satisfactorily uniform.

[0011] In an embodiment, a maximum energy is specified for each beam, and the energy of each of the beam segments in the beam is determined as a percentage (100% or less) or an equivalent fraction of the maximum energy of that beam. In an embodiment, beams having paths that overlap with another beam path outside the target are identified, and the beam intensities of the beam segments of these beams are reduced in the dose calculation. In one or more of these embodiments, the beam intensities of the beam segments of that beam are weighted according to the number of other beams that the overlapping beam overlaps with.

[0012] In an embodiment, when performing a dose calculation for a subvolume outside the target, a value of a dose calculation factor for the subvolume outside the target is accessed. The value of the dose calculation factor is based on the number of beams received by the subvolume outside the target. The value of the dose calculation factor is applied to the dose calculated for the subvolume outside the target to take into account the tissue protection effect of FLASH RT on normal tissue.

[0013] In an embodiment, the number of times (how many times) each beam may be turned on is determined, and the amount of time (how long) that the beam is turned on each time the beam may be turned on is also determined so that the total amount of time that the beam is turned on does not exceed a maximum limit for that beam. In this way, the total amount of time each subvolume external to the target is irradiated by a beam (turned on one or more times) or multiple beams (each beam turned on one or more times) does not exceed the maximum limit, and therefore, the total amount of dose delivered to each subvolume external to the target does not exceed the maximum limit.

[0014] In an embodiment according to the present invention, instead of specifying the conventional approach of the maximum dose rate and the minimum treatment time in the treatment plan, the maximum irradiation time for each subvolume in the target, the maximum irradiation time for each subvolume outside the target, the minimum dose rate for each subvolume in the target, and the minimum dose rate for each subvolume outside the target are specified. As noted above, FLASH RT makes it necessary to deliver a relatively high radiation dose to the target in a short period of time. For example, each beam can deliver at least four grays (Gy) in less than one second, and can deliver up to 20Gy or 50Gy or more in less than one second. In an embodiment, the dose threshold depends on the tissue type.

[0015] Embodiments according to the present invention improve radiation therapy planning and the treatment itself by extending FLASH RT to a wider variety of treatment platforms and target sites (e.g., tumors). By deliberately reducing (if not minimizing) the magnitude of the dose (and in some cases, the overall dose) to normal tissue (outside the target), the treatment plan generated as described herein is superior to conventional techniques in protecting normal tissue from radiation at FLASH dose rates and even non-FLASH dose rates. When used with FLASH dose rates, the management of patient motion is simplified. Treatment planning, while still a complex task, has been simplified relative to conventional plans.

[0016] In summary, embodiments according to the present disclosure relate to generating and implementing a treatment plan that is most effective (relative to other plans) and has the fewest (or most acceptable) side effects (e.g., lowest dose outside the treated area). Thus, embodiments according to the present invention improve the field of radiation treatment planning in particular and radiation therapy in general. Embodiments according to the present invention allow for the rapid generation of the most effective treatment plan. Furthermore, embodiments according to the present invention help improve the operation of computers because, for example, by reducing the complexity of generating a treatment plan, fewer computing resources are required and consumed, which also means freeing up computer resources to perform other tasks.

[0017] In addition to IMRT and IMPT, embodiments according to the present invention may be used for spatially fractionated radiation therapy (including high-dose spatially fractionated grid radiation therapy) and microbeam radiation therapy.

[0018] After reading the following detailed description, those skilled in the art will recognize these and other objects and advantages of embodiments according to the present invention illustrated in the various drawing figures.

[0019] This Summary is provided to introduce some concepts that are further described below in the Detailed Description that follows. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and form a part of this specification and in which like numerals depict like elements, illustrate embodiments of the present disclosure and, together with the detailed description, serve to explain the principles of the present disclosure.

[0021] Figure 1 is a block diagram of an example of a computing system upon which the embodiments described herein may be implemented.

[0022] Figure 2 is a block diagram illustrating an example of an automated radiation therapy treatment planning system in accordance with an embodiment of the present invention.

[0023] Figure 3 A knowledge-based planning system in an embodiment according to the present invention is shown.

[0024] Figure 4A is a block diagram illustrating selected components of a radiation therapy system upon which embodiments of the present invention may be implemented.

[0025] Figure 4B is a block diagram illustrating a non-coplanar arrangement of a gantry and nozzles relative to a patient support in accordance with an embodiment of the present invention.

[0026] Figure 4C is a block diagram illustrating a coplanar arrangement of a gantry and nozzles relative to a patient support in accordance with an embodiment of the present invention.

[0027] Figure 4D is a block diagram illustrating movement of a gantry and nozzles about a patient support in accordance with an embodiment of the present invention.

[0028] Figure 5 is a flow chart of an example of computer-implemented operations for generating a radiation therapy plan in accordance with an embodiment of the present invention.

[0029] Fig. 6A A perspective view showing an example of beam geometry in an embodiment according to the present invention.

[0030] Figure 6B Cross-sectional view showing an example of beam geometry in an embodiment according to the present invention.

[0031] Figure 6C A perspective view showing an example of beam geometry in an embodiment according to the present invention.

[0032] Fig.6D Cross-sectional view showing an example of beam geometry in an embodiment according to the present invention.

[0033] Fig. 7AA field direction view of a beam in an embodiment according to the present invention is shown.

[0034] Figure 7B is a flow chart of an example of computer-implemented operations for weighting beam segments during radiation therapy planning in accordance with an embodiment of the present invention.

[0035] Figure 7C is an example of a depth dose curve for a beam segment in an embodiment according to the present invention.

[0036] Fig.7D A cross-sectional view of a target and a beam including beam segments is shown in an embodiment according to the present invention.

[0037] Fig. 8A is an example of a depth dose curve of a beam in an embodiment according to the present invention.

[0038] Figure 8B , Figure 8C and Fig.8D A beam is shown in a portion of a target according to an embodiment of the present invention.

[0039] Fig. 9 is a flow chart of an example of computer-implemented operations for generating a radiation therapy plan in accordance with an embodiment of the present invention.

[0040] Fig. 10A and Fig. 10B is an example of a dose threshold in an embodiment according to the present invention.

[0041] Fig.11 is a flow chart of an example of computer-implemented operations for radiation therapy planning in accordance with an embodiment of the present invention.

[0042] Fig.12 is a flow chart of an example of computer-implemented operations for radiation therapy planning in accordance with an embodiment of the present invention.

[0043] Fig.13 is a flow chart of an example of computer-implemented operations for calculating dose during radiation therapy planning in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0044] Various embodiments of the present invention will now be referred to in detail, examples of which are shown in the accompanying drawings. Although described in conjunction with these embodiments, it should be understood that they are not intended to limit the present disclosure to these embodiments. On the contrary, the present disclosure is intended to cover alternatives, modifications and equivalents, which may be included in the spirit and scope of the present disclosure as defined by the appended claims. In addition, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it should be understood that the present disclosure can be practiced without these specific details. In other cases, well-known methods, procedures, components and circuits are not described in detail to avoid unnecessary confusion of aspects of the present disclosure.

[0045] Some parts of the following detailed description are presented in terms of procedures, logic blocks, processing, and other symbolic representations of operations on data bits within a computer memory. These descriptions and representations are means by which technicians in the field of data processing most effectively convey the essence of their work to other technicians in the field. In this application, procedures, logic blocks, processes, etc. are conceived as self-consistent sequential steps or instructions that lead to a desired result. These steps are steps that utilize physical manipulations of physical quantities. Typically, although not necessarily, these quantities take the form of electrical or magnetic signals that can be stored, transmitted, combined, compared, and otherwise manipulated in a computing system. It has been shown that it is sometimes convenient to refer to these signals as transactions, bits, values, elements, symbols, characters, samples, pixels, etc., primarily for reasons of general usage.

[0046] However, it should be borne in mind that all of these terms and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise, as will be clear from the following discussion, it should be understood that throughout this disclosure, discussions utilizing terms such as "determine," "access," "direct," "control," "define," "arrange," "generate," "represent," "apply," "add," "multiply," "adjust," "calculate," "predict," "weight," "dispatch," "use," "identify," "reduce," "download," "read," "compute," "store," and the like refer to a computing system or similar electronic computing device or processor (e.g., Figure 1 computing system 100) actions and processes (e.g., Figure 5 , Figure 7B , Fig. 9 , Fig.11 , Fig.12 and Fig.13A computing system or similar electronic computing device manipulates and transforms data represented as physical (electronic) quantities within a computing system memory, register, or other such information storage, transmission, or display device. Terms such as "dose" or "fluence" generally refer to dose or fluence values; the use of such terms will be clear from the context of the surrounding discussion.

[0047] The following detailed description is presented and discussed in terms of the method. Although the drawings (e.g., Figure 5 , Figure 7B , Fig. 9 , Fig.11 , Fig.12 and Fig.13 ) discloses steps and their ordering, but such steps and ordering are exemplary. The embodiments are well suited to perform various other steps or variations of the steps listed in the flowcharts of the figures herein and to perform in a different order than depicted and described herein.

[0048] The embodiments described herein may be discussed in the general context of computer-executable instructions residing on some form of computer-readable storage medium (such as program modules) executed by one or more computers or other devices. By way of example and not limitation, computer-readable storage media may include non-transitory computer storage media and communication media. In general, program modules include routine programs, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functionality of program modules may be combined or distributed as needed.

[0049] Computer storage media include volatile and nonvolatile, removable and non-removable media implemented in any information storage method or technology, such as computer readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other memory technology, compact disk ROM (CD-ROM), digital versatile disk (DVD) or other optical storage devices, magnetic cassettes, magnetic tapes, magnetic disk storage devices or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed to retrieve the information.

[0050] Communication media may embody computer executable instructions, data structures, and program modules, and include any information delivery media. By way of example and not limitation, communication media include wired media (such as a wired network or a direct wired connection) and wireless media (such as acoustic, radio frequency (RF), infrared, and other wireless media). Combinations of any of the above may also be included within the scope of computer-readable media.

[0051] Figure 1 1 is a block diagram of an example of a computing system 100 on which the embodiments described herein may be implemented. In the most basic configuration of system 100, system 100 includes at least one processing unit 102 and memory 104. This most basic configuration is Figure 1 106. The system 100 may also have additional features and / or functionality. For example, the system 100 may also include additional storage devices (removable and / or non-removable), including but not limited to magnetic or optical disks or tapes. Such additional storage devices may be stored in a plurality of storage devices. Figure 1 1 and 120. The system 100 may also include one or more communication connections 122 that allow the device to communicate with other devices, such as in a networking environment using logical connections to one or more remote computers.

[0052] The system 100 further includes one or more input devices 124, such as a keyboard, a mouse, a pen, a voice input device, a touch input device, etc. It also includes one or more output devices 126, such as a display device, a speaker, a printer, etc.

[0053] exist Figure 1 In the example of , the memory 104 includes computer readable instructions, data structures, program modules, etc. associated with an "optimizer" model 150. However, the optimizer model 150 may alternatively reside in any computer storage medium used by the system 100, or may be distributed on some combination of computer storage media, or may be distributed on some combination of networked computers. The functionality of the optimizer model 150 is described below.

[0054] Figure 2 1 is a block diagram illustrating an example of an automated radiation therapy treatment planning system 200 according to an embodiment of the present invention. The system 200 includes an input interface 210 for receiving patient-specific information (data) 201, a data processing component 220 implementing the optimizer model 150, and an output interface 230. The system 200 may be implemented in whole or in part on the computing system 100 ( Figure 1 ) is implemented on / using computing system 100 as a software program, hardware logic, or a combination thereof.

[0055] exist Figure 2 In an example of , the patient-specific information is provided to and processed by the optimizer model 150. The optimizer model 150 generates a prediction result. A treatment plan based on the prediction result can then be generated.

[0056] Figure 3 A knowledge-based planning system 300 is shown in accordance with an embodiment of the present invention. Figure 3In the example of , system 300 includes knowledge base 302 and treatment planning toolset 310. Knowledge base 302 includes patient records 304 (eg, radiation therapy plans), treatment types 306, and statistical models 308. Figure 3 In the example of , the treatment planning toolset 310 includes a current patient record 312 , a treatment type 314 , a medical image processing module 316 , an optimizer model (module) 150 , a dose allocation module 320 , and a final radiation treatment plan 322 .

[0057] Treatment planning toolset 310 searches knowledge base 302 (searches patient records 304) for previous patient records similar to current patient record 312. Statistical model 308 can be used to compare current patient record 312 with predicted outcomes for statistical patients. Using current patient record 312, selected treatment type 306, and selected statistical model 308, toolset 310 generates radiation treatment plan 322.

[0058] More specifically, based on past clinical experience, there may be treatment types that are most commonly used when a patient presents with a particular diagnosis, stage, age, weight, sex, co-morbidities, etc. A first stage treatment type 314 may be selected by selecting a treatment type that the planner has used in the past for similar patients. A medical image processing module 316 provides automatic delineation and automatic segmentation of two-dimensional cross-sectional slides (e.g., from computed tomography or magnetic resonance imaging) to form a three-dimensional (3D) image using the medical images in the current patient record 312. A dose allocation map may be calculated using a dose allocation module 320 of the optimizer model 150.

[0059] In an embodiment according to the invention, the optimizer model 150 uses a dose prediction model to help shape the dose distribution.The optimizer model 150 may provide, for example, a 3D dose distribution, fluence, and an associated dose-volume histogram for the current patient.

[0060] Figure 4A 4 is a block diagram illustrating selected components of a radiation therapy system 400 upon which an embodiment of the present invention may be implemented. Figure 4A In the example of FIG. 4 , system 400 includes a beam system 404 and a nozzle 406 .

[0061] The beam system 404 generates the beam 401 and delivers it to the nozzle 406. The beam 401 can be a proton beam, an electron beam, a photon beam, an ion beam, or a nuclear beam (e.g., carbon, helium, and lithium). In an embodiment, depending on the beam type, the beam system 404 includes a component that guides the beam (e.g., bends, turns, or directs it) in a direction toward and into the nozzle 406. In an embodiment, the radiation therapy system may include one or more multi-leaf collimators (MLCs); each MLC leaf can be independently moved back and forth by the control system 410 to dynamically shape the aperture through which the beam can pass, so as to block or not block part of the beam, and thereby control the beam shape and exposure time. The beam system 404 may also include a component for adjusting (e.g., reducing) the energy of the beam entering the nozzle 406.

[0062] The nozzle 406 is used to aim the beam toward various locations (targets) within a subject (e.g., a patient) supported on a patient support 408 (e.g., a chair or table) in the treatment room. The target may be an organ, a portion of an organ (e.g., a volume or region within an organ), a tumor, diseased tissue, or a patient contour.

[0063] Nozzle 406 can be mounted on the frame ( Figure 4B , Figure 4C and Figure 4D ), the gantry is movable relative to the patient support 408, which is also movable. In an embodiment, the beam system 404 is also mounted on or as part of the gantry; in another embodiment, the beam system is separate from the gantry (but in communication with it).

[0064] Figure 4A The control system 410 receives and implements the prescribed treatment plan. In an embodiment, the control system 410 includes a computer system having a processor, a memory, an input device (e.g., a keyboard), and possibly a display in a well-known manner. The control system 410 can receive data regarding the operation of the system 400. The control system 410 can control parameters of the beam system 404, the nozzle 406, and the patient support device 408 based on the data it receives and based on the prescribed treatment plan, including parameters such as the energy, intensity, direction, size, and / or shape of the beam.

[0065] As noted above, the beam entering the nozzle 406 has a specified energy. Therefore, in an embodiment according to the present disclosure, the nozzle 406 includes one or more components that affect (e.g., reduce, modulate) the beam energy. The term "beam energy adjuster" is used herein as a general term for one or more components that affect the beam energy according to the beam type in order to control the range of the beam (e.g., the degree to which the beam penetrates into the target), control the dose delivered by the beam, and / or control the depth dose curve of the beam. For example, for a proton beam or ion beam having a Bragg peak, the beam energy adjuster can control the position of the Bragg peak in the target. In various embodiments, the beam energy adjuster 407 includes a range modulator, a range shifter, or both a range modulator and a range shifter. That is, when the term "beam energy adjuster" is used, then the element in question can be a range modulator, a range shifter, or both a range modulator and a range shifter. Beam energy modifiers for proton beams and ion beams are disclosed in co-pending patent application (filed), US Application No. 15 / 089,330, entitled "Radiation Therapy Systems and Methods"; however, the present invention is not limited thereto.

[0066] Figure 4B is a block diagram illustrating a non-coplanar arrangement of a gantry 420 and a nozzle 406 relative to a patient support 408 in accordance with an embodiment of the present invention. Figure 4C is a block diagram illustrating a coplanar arrangement of a gantry 420 and a nozzle 406 relative to a patient support 408 and illustrating movement of the gantry and nozzle about the patient support in accordance with an embodiment of the present invention. Figure 4D is a block diagram illustrating movement of the gantry 420 and nozzle 406 about the patient support 408 in accordance with an embodiment of the present invention. This movement may be performed in a non-coplanar arrangement or a coplanar arrangement.

[0067] Figure 5 500 is a flowchart of an example of a computer-implemented operation for generating a radiation therapy plan in accordance with an embodiment of the present invention. Flowchart 500 may be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., Figure 1 Optimizer model 150) (e.g., using Figure 1 computing system 100).

[0068] In intensity modulated radiation therapy (IMRT), such as intensity modulated particle therapy (IMPT), the beam intensity varies across a treatment region (target) within a patient. Depending on the treatment modality, the degrees of freedom available for intensity modulation include beam shaping (collimation), beam weighting (spot scanning), and angle of incidence (which may be referred to as beam geometry). These degrees of freedom result in a virtually unlimited number of potential treatment plans, and thus the consistent and efficient generation and evaluation of high-quality treatment plans is beyond human capabilities and relies on the use of computing systems, particularly in light of the time constraints associated with the use of radiation therapy to treat ailments like cancer and the large number of patients who are undergoing radiation therapy or who need to undergo radiation therapy during any given period of time.

[0069] exist Figure 5 In block 502 of , a prescribed dose to be delivered into and across a target is determined. Each portion of a target may be represented by at least one 3D element called a voxel; a portion may include more than one voxel. A portion or voxel of a target may also be referred to herein as a subvolume; a subvolume may include one or more portions or one or more voxels. As will be described in detail below, each portion or voxel may receive radiation from one or more beams delivered from different directions. The prescribed dose defines, for example, a dose value, or a minimum dose value and a maximum dose value, for each portion or voxel of the target. In an embodiment, the prescribed dose is the same for all portions (subvolumes or voxels) of the target, so that a consistent dose is prescribed for the entire target.

[0070] In block 504, a direction for delivering a beam into a target (e.g., an angle of a gantry relative to a patient or target, or a direction of a nozzle relative to a patient or target) is determined. The beam may be a proton beam, an electron beam, a photon beam, an ion beam, or a nuclear beam. The operation of determining the direction of the beam may include determining the number of beams (the number of directions from which the beam is to be delivered). The paths of the beams may or may not overlap within the target, and may or may not overlap outside the target. In general, when generating a radiation therapy plan, one goal is to determine a beam path that minimizes the irradiation time of each subvolume or voxel of tissue outside the target. Ideally, each subvolume or voxel outside the target is penetrated by at most only a single beam. If a certain degree of overlap between beam paths is allowed, then ideally, each subvolume or voxel outside the target will not be penetrated by more than two beams, and at most only a single beam. In an embodiment, as a means of achieving the above goals, the beam direction is determined so that the total overlap between the paths of the beams outside the target is minimized. In one such embodiment, the directions are determined so that the paths of the beams overlap within the target and so that the total amount of overlap of the paths of the beams outside the target is less than the total amount of overlap of the paths of the beams within the target. In another such embodiment, the directions are determined so that the paths of the beams do not overlap at all outside the target. The paths of the beams may lie in the same plane, or they may lie in different planes. Fig. 6A , Figure 6B , Figure 6C and Fig.6D Provide additional information.

[0071] Any number of other factors may be considered in determining the beam direction. These factors may include the shape and size (e.g., height H and width W, or diameter) of the beam as viewed in the field direction (see Fig. 7A ). These factors may also include, for example, the amount or type of healthy tissue the beam will travel through. That is, if one beam direction travels a shorter distance through healthy tissue relative to another or avoids passing through vital organs, then the one beam direction may be more favorable and may be weighted accordingly.

[0072] exist Figure 5 In block 506 of , a beam energy or intensity is determined for each of the directions (for each of the beams). The beam energy or intensity for each direction is determined so that the predicted or calculated cumulative dose at a location inside the target (e.g., using Figure 1The dose calculated by the optimizer model 150 of FIG. 5 (i) satisfies the prescribed dose as defined in block 502. As noted, the beam paths may or may not overlap in the target; if the paths of the beams overlap in the target, then the beam energy or intensity for each direction is determined such that the predicted or calculated cumulative dose at the location where the paths of the beams overlap inside the target (e.g., using Figure 1 The dose calculated by the optimizer model 150 of the embodiment satisfies the prescribed dose as defined in box 502. In an embodiment, the beam includes several beam segments or beamlets. In one or more such embodiments, a maximum energy of the beam is specified (e.g., 80 MeV), and the energy of each of the beam segments is determined as a percentage (100% or less) or an equivalent fraction of the maximum beam energy. In general, the beams may have the same energy or different energies, and each beam may have a range of energies. Thus, different energies or intensities may be delivered in different directions, and different energies or intensities may be delivered in each direction. In combination Fig. 7A , Figure 7B , Figure 7C and Fig.7D Provide additional information.

[0073] Although Figure 5 The operations in blocks 502, 504, and 506 of are presented as being performed serially and in a certain order, but the invention is not limited thereto. These operations may be performed in a different order and / or in parallel, and they may also be performed in an iterative manner because the number of beams (and, accordingly, the number of directions), beam directions, and beam energies or intensities (and / or beam segment energies or intensities) used to deliver a prescribed dose are interrelated. As noted above, because of the different parameters that need to be considered, the range of values ​​for these parameters, the interrelationships of these parameters, the need to make the treatment plan effective but minimize the risk to the patient, and the need to quickly generate high-quality treatment plans, the use of a computer system that is always on the computing system 100 ( Figure 1 ) to perform radiation therapy planning.

[0074] The following discussion involves beams, targets, doses, and other elements or values. The following discussion is based on the treatment planning toolset 310 and the optimizer model 150 ( Figure 3 ) are background unless otherwise noted or clearly indicated in the Discussion.

[0075] Fig. 6A A perspective view showing an example of beam geometry in accordance with an embodiment of the present invention. Fig. 6AIn the example of, the beam (illustrated by beam 602) is located in the same plane. The beam can be a proton beam, an electron beam, a photon beam, an ion beam, or a nuclear beam. Each beam can deliver a relatively high dose in a relatively short period of time. For example, in an embodiment, each beam can deliver a dose sufficient for FLASH RT in less than one second (e.g., delivering at least four (4) grays (Gy) in less than one second, and delivering up to 20Gy or 50Gy or more in less than one second). In an embodiment, the range is 0.01-500Gy. As described herein, each beam may include one or more beam segments or beamlets. In this example, the paths of the beams overlap only within the target 604 and do not overlap in the surrounding tissue 606 outside the target.

[0076] exist Fig. 6A In the example of , beam 602 (for example) is shown as passing completely through target 604. For beams having a Bragg peak (eg, proton beams and ion beams), the range of the beam can be controlled so that the beam does not pass completely through the target, as will be further described below.

[0077] although Fig. 6A Multiple beams are shown in FIG. 1 , but this does not mean that all beams must be delivered simultaneously or in overlapping time periods, although they can be. The number of beams delivered at any one time depends on the radiation therapy system (e.g., Figure 4A The number of racks or nozzles in the radiation therapy system 400) and the treatment plan.

[0078] Figure 6B A cross-sectional view showing an example of beam geometry in an embodiment according to the present invention. In this example, the beams (exemplified by beams 605 and 606) overlap only within the target and lie in the same plane. This figure depicts the beams in an overlapping manner to show that each portion of the target 604 receives a dose of radiation. The beams can be proton beams, electron beams, photon beams, ion beams, or nuclear beams. In Figure 6B In the example of , the beams are shown as not extending beyond the distal edge of the target 604 (such as is the case with proton or ion beams); however, the invention is not limited in this regard. Each beam can deliver a relatively high dose in a relatively short period of time. For example, each beam can deliver a dose sufficient for FLASH RT.

[0079] If combined Figure 7CAs further discussed, for implementations in which the beam has a Bragg peak (such as a proton beam or an ion beam), the dose delivered by the beam (or beam segment) need not be uniform along the beam path through the entire length of the target 604. Thus, for example, for a proton or ion beam, the dose delivered by the beam 605 at a proximal portion (or edge) 608 of the target 604 may be different from (e.g., less than) the dose delivered by the beam at a distal portion (or edge) 610 of the target (here, the proximal and distal reference beams 605 sources). The same may be said for each proton or ion beam.

[0080] The dose delivered to each portion of target 604 is cumulative, based on the number of beams delivered to and through that portion. For example, the total dose received by the portion of target 604 covered by beams 605 and 606 is the sum of the dose delivered by beam 605 and the dose delivered by beam 606. In an embodiment, the energy of the beams (or beam segments) is accurately determined so that a uniform cumulative dose distribution is achieved within and across target 604 even if the dose along each beam (or beam segment) is not uniform.

[0081] Figure 6C A perspective view showing an example of beam geometry in accordance with an embodiment of the present invention. Figure 6C In the example of , the beams (illustrated by beam 612) are located in different planes. As described herein, each beam may include one or more beam segments or beamlets. In this example, the paths of the beams overlap only within the target 604 and do not overlap outside the target in the surrounding tissue 606. Although multiple beams are shown in this figure, it is not necessary to deliver all beams simultaneously or in overlapping time periods, as mentioned above. The beams can be proton beams, electron beams, photon beams, ion beams, or nuclear beams. Each beam can deliver a relatively high dose in a relatively short period of time. For example, each beam can deliver a dose sufficient for FLASH RT.

[0082] Fig.6DA cross-sectional view of an example of beam geometry in an embodiment according to the present invention is shown. In this example, the beams (illustrated by beams 621, 622, and 623) overlap only within the target and are located in the same plane. Although three beams are shown, the present invention is not limited thereto. As described herein, each beam may include one or more beam segments or beamlets. In this example, the paths of the beams overlap only within the target 604, and do not overlap in the surrounding tissue 606 outside the target. Although multiple beams are shown in this figure, it is not necessary to deliver all beams simultaneously or in overlapping time periods, as mentioned above. The beam may be a proton beam, an electron beam, a photon beam, an ion beam, or a nuclear beam. Each beam may deliver a relatively high dose in a relatively short time period. For example, each beam may deliver a dose sufficient for FLASH RT.

[0083] exist Fig.6D In the example of , beams 621, 622, and 623 intersect at subvolume 630, other subvolumes in target 604 receive doses from both of the beams, other subvolumes in the target receive doses from only one of the beams, and still other subvolumes receive no dose. The direction and / or number of beams may be varied (that is, time-fractionated) over several treatment sessions so that a uniform dose is delivered across the target.

[0084] As mentioned above, for implementations using proton beams or ion beams, the dose delivered by each beam at a corresponding proximal portion (or edge) of the target 604 may be different from (e.g., less than) the dose delivered by the beam at a corresponding distal portion (or edge) of the target (e.g., the source of the previous, proximal and distal reference beams).

[0085] The dose delivered to each portion of target 604 is cumulative, based on the number of beams delivered to and passing through that portion. For simplicity, not all beams are shown in this figure; generally, the number of beams is sufficient to achieve a uniform cumulative dose distribution within target 604.

[0086] In general, the surface of the target can be considered to have several discrete facets. From this perspective, for beams other than photon beams, each incident beam is perpendicular to each facet, so that the beams do not overlap outside the target. In the case of photon beams, each incident beam is parallel to the facet and does not overlap with other beams outside the target.

[0087] Fig. 7A 702 according to an embodiment of the present invention. Fig. 7A A cross section of the beam is shown. Fig. 6A , Figure 6B , Figure 6C and Fig.6DThe beam of is an example of beam 702. Beam 702 is shown as being rectangular in shape, having a height H and a width W. However, the present invention is not limited in this regard, and beam 702 may have virtually any regular or irregular cross-sectional (e.g., BEV) shape. For example, the shape of beam 702 may be defined using an MLC that blocks one or more portions of the beam. Different beams may have different shapes.

[0088] exist Fig. 7A In an embodiment, beam 702 includes several beam segments or beamlets (which may also be referred to as spots), exemplified by beam segments 704, 706, and 708. A maximum energy is specified for beam 702 (e.g., 80 MeV), and an energy level is defined for each of the beam segments as a percentage or fraction of the maximum energy. In essence, each of the beam segments is weighted with respect to its energy level; some beam segments are weighted to have higher energy levels than other beam segments. By weighting the energy of each beam segment, the intensity of each beam segment is also effectively weighted. The energy of each beam segment is defined so that the beam segment will deliver a fraction of the prescribed dose such that, in combination with other beam segments in the beam, and in combination with other beams (and beam segments), a uniform (homogeneous) cumulative dose meeting the prescribed dose will be delivered within and across the volume of the target. The energy of each beam segment may be weighted using Figure 4A The beam energy adjuster 407 achieves a defined energy level or intensity for each beam segment.

[0089] Each beam segment can deliver a relatively high dose in a relatively short period of time. For example, each beam segment can deliver at least 4 Gy in less than one second, and can deliver up to 20 Gy or 50 Gy or more in less than one second. The energy or intensity of each beam segment can be used Figure 4A The beam energy adjuster 407 is used to control the beam segment so that the beam segment has energy sufficient to reach the distal edge of the target.

[0090] In operation, in an embodiment, beam segments are delivered sequentially. For example, beam segment 704 is delivered to a target (turned on) and then turned off, then beam segment 706 is turned on and then turned off, then beam segment 708 is turned on and then turned off, and so on. Each beam segment may be turned on for only a fraction of a second (on the order of milliseconds).

[0091] Figure 7B 750 is a flowchart of an example of a computer-implemented operation for weighting beam segments during radiation therapy planning in accordance with an embodiment of the present invention. Flowchart 750 may be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., Figure 3 Optimizer model 150) (e.g., using Figure 1 computing system 100).

[0092] An embodiment according to the invention introduces a further parameter during the weighting of the beam segments in the beam (also called spot weighting), which depends on whether the beam overlaps with another beam outside the target.

[0093] exist Figure 7B In block 752 of FIG. 1 , a prescribed dose to be delivered into and across the target is determined. The prescribed dose may be delivered using Figure 3 The system 300 is generated.

[0094] exist Figure 7B In block 754 of , the values ​​of parameters such as the number of beams to be directed into the subvolume in the target, the direction of the beams, and the beam energy are accessed. As described above, the paths of the beams overlap within the target. These parameter values ​​can be used Figure 3 The system 300 is generated.

[0095] exist Figure 7B In block 756, any beams that overlap outside the target are identified.

[0096] In block 758, for each beam, a maximum beam energy for the beam is determined.

[0097] In block 760 , for each beam, a beam energy of the beam segment is determined as a percentage of the maximum beam energy of the beam.

[0098] In block 762, for each overlapping beam identified in block 756, the beam energy of the beam segments of these beams is reduced by a corresponding factor. The factor may be increased (to increase the amount of reduction) for beams that intersect more than one other beam. In other words, if normal (healthy) tissue is hit by more than one beam, the penalty is greater. The factor applied to the beam energy of these beam segments is determined so that the cumulative dose delivered to the target meets the prescribed dose. In this way, the beam energy or intensity and associated dose of beams that overlap outside the target are reduced while still allowing the prescribed dose to be delivered to the target.

[0099] Figure 7C is an example of a depth dose curve of a beam section of a beam having a Bragg peak, such as a proton beam or an ion beam, in an embodiment according to the present invention. Figure 7C The example of FIG. 400 shows the calculated dose level of beam 702 or any beam segment in the beam as a function of depth in the target (distance from the beam source). The energy level or intensity of each beam segment can be adjusted using beam energy adjuster 407 ( Figure 4A ) is controlled so that the Bragg peak is located at (adjacent to or close to) a portion at a distal edge of the target, such as Figure 7C shown.

[0100] review Figure 6B , it can be seen (or inferred) that each beam overlaps a greater portion toward the center of the target 604 than at the edges of the target 604, and that more beams overlap at or near the center of the target than at the edges of the target 604. For example, beams 602 and 603 do not overlap at the proximal edge 608 of the target 604, overlap to a greater extent toward the center of the target, overlap completely at or near the center of the target, and overlap partially across the center and at the distal edge 610. All beams overlap at the center of the target 604, but all beams do not overlap at the edges of the target. As mentioned previously herein, the dose contributed by each beam is cumulative, and the target 604 can be represented by 3D elements called voxels or subvolumes. Each voxel or subvolume will receive radiation from one or more beam segments delivered from different directions. The total dose for a voxel is the sum of the doses delivered by each beam segment received by the voxel. By shaping the beam segments, such as Figure 7C As shown in the example of for beams with Bragg peaks (e.g., proton beams and ion beams), portions or voxels or subvolumes in the target 604 that are traversed by fewer beams (beam segments) will receive a larger dose per beam segment because the Bragg peaks of these beam segments coincide with the locations of these portions / voxels / subvolumes, while portions / voxels / subvolumes in the target that are traversed by more beams (beam segments) will receive a smaller dose per beam segment because the Bragg peaks of later beam segments do not coincide with the locations of later portions / voxels. In other words, the Bragg peak of each beam is located at the far edge of the target 604 (at the far edge, there is less overlap between beams), and the dose per beam is less than if the Bragg peak is located at a location inside the target where there is greater overlap between beams. In this way, for embodiments using beams with Bragg peaks, a uniform dose can be delivered within and across the target 604.

[0101] Fig.7D A cross-sectional view in the longitudinal direction of an irregularly shaped target 715 and a beam 720 including four beam segments 721, 722, 723, and 724 in accordance with an embodiment of the present invention is shown. As described above, the energy of each of the beam segments 721, 722, 723, and 724 can be individually defined and individually controlled (e.g., using Figure 4AThe beam energy adjuster 407 is used to adjust the energy of the beam segments 721, 722, 723, and 724 so that the beam segments have enough energy to reach the distal edge of the target 715. In particular, for beams with Bragg peaks like proton beams and ion beams, the energy levels of the beam segments 721, 722, 723, and 724 can be independently controlled using the beam energy adjuster 407 so that the Bragg peak of each beam segment is located at (adjacent to or close to) the portion at the distal edge of the target 715. In this way, the range of the beam 720 can be shaped so that it follows the shape of the target 715 in the longitudinal direction. The cross-sectional size (e.g., height and width, or diameter) of each beam segment can be specified according to the complexity of the shape of the target 715. For example, if the target surface is relatively uniform (e.g., flat), the size of the beam segment can be larger.

[0102] Fig. 8A is an example of a depth dose curve 802 for a beam 804 in accordance with an embodiment of the present invention. Fig. 8A The example of FIG. 8 shows the calculated dose level of beam 804 as a function of depth (distance from the beam source) in target 806. Fig. 8A In the example of , beam 804 is a beam having a Bragg peak (eg, a proton beam or an ion beam). Figure 8B A beam 804 is shown in a portion of a target 806 in accordance with an embodiment of the present invention. The following discussion presents examples in the context of a beam; however, as described above, a beam may include beam segments, and the following examples and discussion may be readily extended to beam segments.

[0103] exist Fig. 8A In the example of , the depth dose curve 802 is divided into a set of regions 802a, 802b, 802c, 802d, and 802e (802a-802e). In a corresponding manner, the beam 804 is divided into a set of longitudinal beam regions 804a, 804b, 804c, 804d, and 804e (804a-804e). Beam regions 804a-804e are aligned with regions 802a-802e. The width of regions 802a-802e (and therefore the length of beam regions 804a-804e) increases in size as the distance from the Bragg peak increases, because that is where the calculated dose is more uniform (the dose curve is relatively flat). At or near the Bragg peak (e.g., regions 802c, 802d, and 802e), the regions are shorter / thinner.

[0104] Each of the beam regions 804a-804e is assigned a value xn (in the described example, n=1, 2, ..., 5) corresponding to the calculated amount of dose for the beam region. Region 804a has a value of x1, region 804b has a value x2, and so on. For example, the value xn may range from one (1) to 100. In an embodiment, the value is generally proportional to the amount of calculated dose. In one or more such embodiments, the value x4 for beam region 804d corresponding to the location 802d of the Bragg peak in the depth dose curve 802 is a maximum value that is greater than other values ​​assigned to other beam regions in beam 804.

[0105] exist Figure 8B 804 is shown as entering the target 806 from a certain direction. If the beam 804 enters the target 806 from a different direction, then the value xn may be different. In other words, the value xn may be different depending on the gantry angle or beam direction associated with the beam 806, even if the beam energy does not change with angle or direction. In an embodiment, the beam regions 804a-804e are assigned values ​​according to both the corresponding dose depth curve 802 and the beam direction.

[0106] Figure 8C A second beam 814 is shown traversing the target along the same path as beam 804 but in the opposite direction, in accordance with an embodiment of the present invention. That is, the paths of beams 804 and 814 overlap, as in Figure 6B In an embodiment of the present invention, beam 814 is a beam having a Bragg peak (eg, a proton beam or an ion beam). Beams 804 and 814 do not have to be delivered simultaneously, although they can be.

[0107] Like beam 804, beam 814 is divided into a set of beam regions 814a, 814b, 814c, 814d, and 814e (814a-814e) that are aligned with regions of a dose depth curve (not shown) for beam 814. Each of beam regions 814a-814e is assigned a value yn (in the described example, n=1, 2, ..., 5) corresponding to the calculated amount of dose for the beam region. The value yn may range from 1 to 100. In an embodiment, the value at the isocenter of beams 804 and 814 is the same.

[0108] When beams overlap in target 806, the subvolume of the target traversed by the beams receives a dose from each beam. Figure 8B and Figure 8C In the example of , the cumulative dose of the subvolume is represented by adding together the values ​​of xn and yn corresponding to the regions of the subvolume traversed by beams 804 and 814. Fig.8DBeams 804 and 814 are shown in an overlapping manner. Fig.8D In the example, subvolume 821 has a cumulative dose represented by x1+y5, subvolume 822 has a cumulative dose represented by x2+y5, subvolume 823 has a cumulative dose represented by x3+y5, subvolume 824 has a cumulative dose represented by x4+y5, subvolume 825 has a cumulative dose represented by x5+y5, subvolume 826 has a cumulative dose represented by x5+y4, subvolume 827 has a cumulative dose represented by x5+y3, subvolume 828 has a cumulative dose represented by x5+y2, and subvolume 829 has a cumulative dose represented by x5+y1.

[0109] like Figure 6B As shown, a subvolume may be traversed by more than two beams, in which case the cumulative dose of the subvolume is represented by adding the appropriate values ​​for each beam that hits the subvolume. That is, for each subvolume in target 806, a total value is determined by adding together the values ​​for each beam region of each beam that hits the subvolume.

[0110] Optimizer Model( Figure 3 ) can adjust parameters that affect the calculated dose delivered to the target 806 to achieve a satisfactorily uniform cumulative dose across the target 806. A satisfactorily uniform cumulative dose is indicated when the total values ​​per subvolume in all of the targets 806 are the same, or when the difference between the total values ​​per subvolume meets a threshold. The threshold can be, for example, a value that specifies the maximum amount of difference between the total values ​​allowed. That is, the parameters that affect the calculated dose to be delivered by the beam region are adjusted until the total values ​​of the subvolumes are all within a specified range of each other or are the same, thereby indicating that the dose to be delivered across the target is satisfactorily uniform.

[0111] Fig. 9 900 is a flowchart of an example of a computer-implemented operation for generating a radiation therapy plan in accordance with an embodiment of the present invention. Flowchart 900 may be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., Figure 3 Optimizer model 150) (e.g., using Figure 1 computing system 100).

[0112] exist Fig. 9 In block 902 of , values ​​of parameters such as the number of beams to be directed into and across the subvolumes in the target, the directions of the beams, and the beam energies of the beams are accessed. These parameter values ​​may be used Figure 3 The system 300 generates and can be stored in Figure 1 in the memory of the computing system 100.

[0113] exist Fig. 9 In block 904 of FIG. 1 , each portion of the beam in the target is represented as a set of corresponding longitudinal beam regions. Figure 8B and discussion thereof.

[0114] In block 906, the amount of dose to be delivered for each of the beam zones is calculated, and a value corresponding to the calculated amount of dose for each beam zone is assigned to the beam zone. Figure 8B and Figure 8C and discussion thereof.

[0115] exist Fig. 9 In block 908 of , for each subvolume in the target, the values ​​of each beam region reaching the subvolume for each beam are added together to generate a total value for the subvolume. Fig.8D and discussion thereof.

[0116] exist Fig. 9 In block 910, a parameter that affects the calculated amount of dose to be delivered by the beam region is adjusted until the difference between the total values ​​of the subvolumes meets a threshold or is the same (in the latter case, the threshold is zero). That is, the value of the parameter is adjusted until the dose across the target is satisfactory (e.g., the dose is uniform or nearly uniform across the target).

[0117] In block 912, the adjusted parameter values ​​are provided as radiation therapy plan 322 ( Figure 3 ) is stored in computing system 100 ( Figure 1 ) in the memory.

[0118] In an embodiment according to the present invention, dose thresholds are used to specify limits for a radiation therapy plan. Fig. 10A and Fig. 10B Examples of dose thresholds are presented in .

[0119] Fig. 10A and Fig. 10B Shows the normal (healthy) tissue protection dose as a function of dose rate or irradiation time. Fig. 10A In the example of , the function is a step function. Fig. 10B In the example of , the function is a sigmoid function. Fig. 10A and Fig. 10B The dose, dose rate and irradiation time in are examples only. Other functions may be used. The dose threshold curve may be tissue-dependent. For example, the dose threshold curve for the lung may be different from the dose threshold curve for the brain. Figure 3 ) can be used to establish dose constraints for the radiation therapy plan. For example, appropriate (e.g., tissue-dependent) dose threshold curves can be used to determine beam direction (gantry angle) and beam segment weighting ( Fig. 7A). That is, parameters that affect dose can be adjusted during radiation therapy planning so that the constraints in the dose threshold curve are met.

[0120] Dose constraints may include, but are not limited to: a maximum limit on the irradiation time of each subvolume (voxel) in the target (e.g., a treatment time shorter than x1 seconds for each voxel of target tissue); a maximum limit on the irradiation time of each subvolume (voxel) outside the target (e.g., a treatment time shorter than x2 seconds for each voxel of normal tissue; x1 and x2 may be the same or different); a minimum limit on the dose rate of each subvolume (voxel) in the target (e.g., a dose rate greater than y1 Gy / sec for each voxel of target tissue); and a minimum limit on the dose rate of each subvolume (voxel) outside the target (e.g., a dose rate greater than y2 Gy / sec for each voxel of normal tissue; y1 and y2 may be the same or different). In general, these constraints are intended to minimize the amount of time that normal tissue is irradiated.

[0121] Fig.11 1100 is a flowchart of an example of a computer-implemented operation for radiation therapy planning in accordance with an embodiment of the present invention. Flowchart 1100 may be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., Figure 3 Optimizer model 150) (e.g., using Figure 1 computing system 100).

[0122] exist Fig.11 In block 1102 of , values ​​of parameters such as the number of beams to be directed into the subvolume in the target, the direction of the beams, and the beam energy are accessed. These parameter values ​​can be used by system 300 ( Figure 3 ) is generated and may be stored in the computing system 100 ( Figure 1 ) in the memory.

[0123] exist Fig.11 In block 1104 of , information specifying constraints for the radiation therapy plan is accessed. In an embodiment, the constraints are based on dose thresholds (see, e.g., Fig. 10A and Fig. 10B ), and includes a maximum limit on the irradiation time of each subvolume outside the target. Other limits may include a maximum limit on the irradiation time of each subvolume in the target, a minimum limit on the dose rate of each subvolume in the target, and a minimum limit on the dose rate of each subvolume outside the target.

[0124] exist Fig.11In block 1106 of , in an embodiment, the values ​​of the parameters are adjusted until the irradiation time of each subvolume outside the target meets the maximum limit on the irradiation time. In general, the goal is to minimize the amount of time that healthy tissue (tissue outside the target) is irradiated. It should be noted that multiple beams can pass through subvolumes outside the target as long as the total irradiation time of the subvolumes is shorter than the limit.

[0125] In an embodiment, the values ​​of the parameters that affect the calculated amount of dose to be delivered by the beam are adjusted until the calculated total doses for the subvolumes in the target are within a specified range of each other. In other words, the values ​​of the parameters that affect the calculated amount of dose to be delivered by the beam are adjusted until the calculated total doses for the subvolumes in the target are satisfactorily uniform across the entire target.

[0126] In block 1112, the adjusted parameter values ​​are used as the radiation therapy plan 322 ( Figure 3 ) is stored in computing system 100 ( Figure 1 ) in the memory.

[0127] As discussed previously herein, beam directions (gantry angles) are defined to minimize the amount of overlap between beam paths outside the target. The goal is no overlap between beam paths outside the target; however, this may not always be possible or advantageous from a treatment goal perspective.

[0128] Fig.12 1200 is a flowchart of an example of a computer-implemented operation for radiation therapy planning in accordance with an embodiment of the present invention. Flowchart 1200 may be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., Figure 3 Optimizer model 150) (e.g., using Figure 1 computing system 100).

[0129] exist Fig.12 In block 1202 of FIG. 1 , values ​​of parameters such as the number of beams to be directed in the subvolume in the target, the direction of the beams, and / or the beam energy are accessed. These parameter values ​​can be used Figure 3 The system 300 generates and can be stored in Figure 1 The beam energy and the number and / or direction of the beams are determined so that the entire target receives a minimum prescribed dose.

[0130] exist Fig.12 In box 1204, the number of times (how many times) each of the beams can be turned on is determined, and the amount of time (how long) that the beam is turned on each time the beam can be turned on is also determined, so that the total amount of time the beam is turned on does not exceed a maximum limit of the beam (for example, the "on time" of the beam can be minimized).

[0131] It should be noted that, as previously mentioned herein, a subvolume outside the target may be irradiated by only one beam, or it may be irradiated by multiple beams (two or more beams may overlap the subvolume). Thus, a subvolume outside the target may be irradiated multiple times: the subvolume may be irradiated multiple times by the same beam (the beam is turned on and off multiple times), or the subvolume may be irradiated by multiple beams (each of these beams may be turned on and off once or on and off multiple times). However, the total amount of time that the subvolume may be irradiated is minimized. That is, a maximum limit is specified for the irradiation time per subvolume. Equivalently, a maximum limit is specified for the total amount of time that each beam may be turned on. Thus, the total amount of time that each beam is turned on may be minimized while still meeting the prescribed dose to be delivered to the target. In this way, while still delivering the prescribed dose across the entire target, the total amount of time that each subvolume outside the target is irradiated by the beam does not exceed the maximum limit (e.g., it may be minimized), and therefore, the total amount of dose delivered to each subvolume outside the target does not exceed the maximum limit (e.g., it may be minimized).

[0132] Fig.13 1300 is a flowchart of an example of a computer-implemented operation for calculating dose (particularly dose calculation of a target external subvolume) during radiation therapy planning in accordance with an embodiment of the present invention. Notably, as will be seen, the method of flowchart 1300 takes into account the tissue sparing effect of FLASH RT on normal (healthy) tissue. Flowchart 1300 may be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., Figure 3 Optimizer model 150) (e.g., using Figure 1 computing system 100).

[0133] exist Fig.13 In block 1302 of , the value of a dose calculation factor for the target external subvolume is accessed. The value of the dose calculation factor is determined based on the number of beams that reach the target external subvolume. If a single beam reaches the target external subvolume, the dose calculation factor has a first value close to zero (e.g., 0.1). If more than two beams reach the target external subvolume, the value of the dose calculation factor increases (e.g., increases to 0.3). The dose calculation factor increases as the number of beams received by the target external subvolume increases. If the target external volume receives all beams specified by the radiation therapy plan, the dose calculation factor is 1.0, thereby reflecting that the tissue protection effect of FLASH RT is not achieved.

[0134] In block 1304 , a dose for the target outer subvolume is calculated.

[0135] In block 1306, the value of the dose calculation factor is applied to the dose calculated for the target outer subvolume. That is, for example, the calculated dose is multiplied by the dose calculation factor. If, for example, the subvolume receives a single beam, the calculated dose is reduced by a factor of 0.1, thereby identifying the tissue protection effect of FLASH RT.

[0136] In summary, embodiments according to the present invention improve radiation therapy planning and the treatment itself by extending FLASH RT to a wider variety of treatment platforms and target sites. By deliberately reducing (if not minimizing) the magnitude of the dose to normal tissue (outside the target) (and in some cases, the whole), the treatment plan generated as described herein is superior to conventional techniques for protecting normal tissue from radiation even in the case of non-FLASH dose rates. When used with FLASH dose rates, the management of patient motion is simplified. Although treatment planning is still a complex task of finding a balance between competing and related parameters, it has been simplified relative to conventional plans. The technology described herein can be used for stereotactic radiation surgery in the case of single or multiple metastases and stereotactic whole body radiation surgery.

[0137] In addition to IMRT and IMPT, embodiments according to the present invention may be used for spatially fractionated radiation therapy (including high-dose spatially fractionated grid radiation therapy) and microbeam radiation therapy.

[0138] Although the subject matter has been described in language specific to structural features and / or methodological acts, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features and acts described above are disclosed as exemplary forms of implementing the claims.

Claims

1. A non-transitory computer-readable storage medium having computer-executable instructions for causing a computing system to perform a method for generating a radiation therapy plan, the method comprising: determining a prescribed dose to be delivered into and across a target; accessing values ​​of parameters including a number of beams in a plurality of beams to be directed into a subvolume in the target, directions of the plurality of beams, and beam energies of the plurality of beams, wherein each of the beams includes a plurality of beam segments; identifying, based on the parameter, any overlapping beams of the plurality of beams having respective beam paths that overlap outside of the target; determining, for each beam of the plurality of beams, a maximum beam energy for the beam, and determining a beam energy of the beam segment of the beam as a percentage of the maximum beam energy for the beam; reducing, for each of the overlapping beams that overlap outside the target, a planned beam intensity of the beam segment of the overlapping beam by a factor, wherein the planned beam intensity for the beam segment of the plurality of beams is determined such that a cumulative dose delivered to the target satisfies the prescribed dose; representing each of the beams in the target as a set of corresponding longitudinal beam regions, wherein a value corresponding to a calculated amount of a dose to be delivered by the beam region is associated with each beam region in the set; as well as The value of the parameter is stored in a memory of the computing system after the reducing as at least part of the radiation therapy plan.

2. The non-transitory computer-readable storage medium of claim 1, wherein the method further comprises: for each subvolume in the object, adding together the values ​​of each beam region of each beam reaching the subvolume to determine a total value for the subvolume, thereby producing a corresponding total value for the subvolume in the object; as well as The values ​​of the parameters that influence the calculated amount of dose to be delivered by the beam region are adjusted until a difference between the total values ​​for the subvolumes satisfies a threshold.

3. The non-transitory computer-readable storage medium of claim 1 , wherein the method further comprises: accessing, for a target outer subvolume, a value of a dose calculation factor, wherein the value of the dose calculation factor is determined based on a number of beams that reach the target outer subvolume; calculating a dose for the target outer subvolume; and The value of the dose calculation factor is applied to the dose calculated for the target outer subvolume, wherein the dose calculation factor reduces the dose calculated for the target outer subvolume if only one beam reaches the target outer subvolume.

4. The non-transitory computer-readable storage medium of claim 1 , wherein the method further comprises: A dose threshold is used to specify a constraint for the radiation therapy plan, wherein the constraint is selected from the group consisting of: a maximum limit on irradiation time for each subvolume in the target; a maximum limit on the irradiation time for each subvolume outside the target; a minimum limit on dose rate for each subvolume in the target; and A minimum limit on the dose rate for each subvolume outside the target. The non-transitory computer-readable storage medium of claim 4 , wherein the dose threshold depends on tissue type.

6. The non-transitory computer-readable storage medium of claim 1, wherein the beam comprises a beam type selected from the group consisting of: protons, electrons, photons, nuclei, and ions.

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