Enhanced dose rate / ultra-high dose rate radiation and spatially split radiation therapy

Abstract

One or more new indicators are introduced in the process of processing the plan. More specifically, correction factors / metrics referred to herein as key / repair ratio indices are introduced, and / or spatially periodic correction factors / metrics referred to herein as key equal dose values are introduced. By using these indicators, the expected savings of the dose spatial distribution may be better considered in the processing mode, including general spatially segmented radiation therapy (SFRT) and particularly SFRT with ultra-high dose rates. The targets may be covered by extended Bragg peaks according to a treatment plan strategy to optimize and / or homogenize target levels of dose distribution, but still can benefit from SFRT saving effects at healthy tissue levels. Transport techniques include a dynamic focusing technique and a magnetic bundle steering technique. Increasing the dose rate can maximize the peak valley dose distribution of SFRT despite movement of the patient.

Description

Background Art

[0001] Radiation therapy is well known for its use in the treatment of cancer. Generally, radiation therapy involves directing radiation beams to a target in the body, such as a malignant tumor, a resected tumor bed, a site known to be at risk for tumor progression, or a benign lesion.

[0002] Using proton beams for radiation therapy (proton therapy) has significant advantages over using other types of beams. The depth to which a proton beam reaches tissue depends on the energy of the beam, and it is at this depth that most of its energy is delivered (most of the dose is delivered). The region in the depth-dose curve where most of the energy is delivered is called the Bragg peak of the beam.

[0003] Before radiation therapy is given to a patient, a treatment plan is developed for that patient. The treatment plan defines all aspects of radiation therapy using simulations and optimizations that may be based on past experience. In general, the goal of a treatment plan is to deliver sufficient radiation to unhealthy tissue while minimizing the exposure of surrounding healthy tissue to radiation.

[0004] One type of radiation therapy technique is called spatially fractionated radiation therapy (SFRT). In SFRT, multiple beams of radiation are directed into a target volume. These beams are spatially separated from each other; that is, they take different paths through the tissue and they do not completely overlap, resulting in a characteristic "peak and valley" dose distribution. Types of spatially separated beams include grids, microbeams and microbeams, beamlets, pencil beams (spot scanning beams), which are appropriately oriented and spaced. Microbeams are distinguished from other types of GRID-SFRT techniques by the distance between the beams and the size of the beams. The full width at half maximum (FWHM) of a microbeam may be in the range of less than two millimeters (mm), while other types of SFRT beams are larger. For ease of discussion, this article uses the term "beam" in the most general way to include beams of any size applied to SFRT.

[0005] SFRT can be performed using a variety of radiation treatment modes, including intensity modulated radiation therapy (IMRT) and intensity modulated particle therapy (IMPT). In SFRT / IMRT, a collimator is used to direct the beam to the target. A portion of the beam passes through an opening (e.g., a hole or slit) in the collimator, while the remainder of the beam is blocked or attenuated by the collimator. The opening in the collimator is positioned to align with a location (e.g., a point) in the target volume specified in the treatment plan. In SFRT / IMPT, a scanning magnet in the collimator and / or the treatment machine nozzle is used to focus the beam into the target volume. In both cases, SFRT / IMPT controls the direction of a relatively narrow beam directed to a location in the target volume specified in the treatment plan.

[0006] The advantage of SFRT is that it provides better treatment tolerance to healthy tissues compared with standard homogeneous radiation therapy. The biological mechanism behind this sparing effect is thought to be related to the specific continuous high-dose peak to low-dose peak distribution of SFRT. Since the motion of the target and surrounding tissues during conventional dose delivery is expected to smooth this dose distribution, motion may reduce the overall advantage of SFRT.

[0007] In addition, conventional treatment planning systems do not adequately consider the spatial distribution of dose. For example, the conventional dose volume histogram (DVH) metric used during the treatment planning process to evaluate the quality of a proposed treatment plan does not consider the spatial distribution of dose. Summary of the invention

[0008] To address the above issues, a new dedicated metric is needed to optimize spatially fractionated radiation therapy (SFRT) treatment plans, including proton-SFRT treatment plans. Ideally, the metric should also consider the distribution of peaks coinciding with the paths of the incident spatially fractionated beams and valleys coinciding with the spacing between these beams, and should also be compatible with the current dose-volume histogram (DVH) representation. In addition, since tolerance to proton-based SFRT is expected to be motion-sensitive, a motion mitigation strategy that is compatible with the treatment planning system is also needed.

[0009] In one aspect, the invention provides a computer system as defined in claim 1. Optional features are specified in the dependent claims.

[0010] In another aspect, the invention provides a system as defined in claim 12. Optional features are specified in the dependent claims.

[0011] In another aspect, the invention provides a computer implemented method as defined in claim 20. Optional features are specified in the dependent claims.

[0012] In another aspect, the invention provides a system as defined in claim 28. Optional features are specified in the dependent claims.

[0013] In one embodiment, a system includes a beam system that generates a radiation beam; a nozzle connected to the beam system and directing the radiation beam to a target volume; and a control system connected to the beam system and the nozzle, the control system including a computer system, the computer system including a processor and a memory connected to the processor; wherein the memory stores a radiation treatment plan, the radiation treatment plan including information describing the spatial distribution of the radiation beam and a dose volume histogram (DVH) of the target volume and a tissue volume located outside the target volume and intersecting the radiation beam, wherein the DVH is based on a metric as a function of the dose distribution in the tissue volume; and wherein the control system controls the beam system and the nozzle to deliver a dose to the target volume according to the radiation treatment plan.

[0014] According to embodiments of the present disclosure, solutions to meet the above needs are provided by introducing one or more new indicators into the treatment planning process. In embodiments, a correction factor / indicator referred to herein as the critical / repair ratio index (CRI) is introduced. In other embodiments, a correction factor / indicator referred to herein as the spatial periodicity of critical isodose values ​​(SP-CIV) is introduced. In principle, these indicators enable planners and clinicians to better assess the DVH and even apply correction factors to the DVH of SFRT (e.g., proton-SFRT) treatment plans.

[0015] CRI is a metric that considers the area of ​​a given isodose surface in addition to the target volume. More specifically, CRI optimizes (eg, maximizes) the surface area of ​​the severely lesioned isodose volume during treatment planning.

[0016] SP-CIV is a metric that, in general, limits the surface of a severely damaged isodose volume so that the contour of the surface does not lie within a certain distance of itself; that is, so that the contour does not fold back on itself. In an embodiment, the maximum SP-CIV and / or minimum SP-CIV may be calculated as the maximum spatial periodicity and / or minimum spatial periodicity of the contour given by the surface. In an embodiment, the maximum SP-CIV cannot be greater than a first specified limit, and the minimum SP-CIV cannot be less than a second specified limit.

[0017] Embodiments according to the present disclosure may be used for radiation therapy / treatment modes including, but not limited to, enhanced dose rate (EDR) radiation therapy (RT), ultra-high dose rate (UHDR) RT, and FLASHRT. EDR is defined as a dose rate ranging from 1 to 40 Grays per second (Gy / s). UHDR is defined as a dose rate greater than 40 Gy / s. FLASHRT is a special case of UHDRRT, where, in addition to the dose rate, the expected tolerance of healthy tissue is greater than the expected tolerance of a low dose rate due to the so-called "FLASH effect." Specifically, embodiments according to the present disclosure include a combination of SFRT (including SFRT with a transmitted proton beam; for example, pencil beam scanning), EDRRT, UHDRRT, FLASHRT, and a proton beam with an extended Bragg peak (SOBP). Due to these combinations, during treatment of a patient, a uniform therapeutic dose can be delivered throughout the target volume by spatially segmenting the beam through healthy tissue. Another advantage of the combination of SFRT, EDRRT, UHDRRT, FLASHRT and proton beam (including transmitted proton beam or proton beam with SOBP) is that the effect of patient motion on the patient dose distribution pattern during treatment is eliminated or greatly reduced.

[0018] Also disclosed are techniques that can be used to deliver general spatially segmented beams (including transmitted proton beams and proton beams with SOBP) for SFRT using EDR or UHDR or FLASH. These techniques include the use of collimators or dynamic focusing techniques and magnetic beam steering techniques.

[0019] Those skilled in the art will recognize these and other objects and advantages according to embodiments of the present invention after reading the following detailed description, which is illustrated in the various drawing figures.

[0020] This Abstract is intended to introduce some concepts that are further described below in the Detailed Description. This Abstract is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, in which like numerals represent like elements, illustrate embodiments according to the present disclosure and, together with the detailed description, serve to explain the principles of the present disclosure. The drawings are not necessarily drawn to scale.

[0022] Figure 1 is a block diagram of an example of a computer system in which embodiments described herein may be implemented.

[0023] Figure 2 and Figure 3 is a block diagram illustrating an example of an automated radiation treatment planning process in an embodiment according to the present disclosure.

[0024] Figure 4 is a block diagram illustrating selected components of a radiation therapy system in which embodiments according to the present disclosure may be implemented.

[0025] Figure 5 An example of spatially split beams in accordance with an embodiment of the present disclosure is shown.

[0026] Fig. 6A is a diagram showing a cross-sectional view of a target volume in an embodiment according to the present disclosure.

[0027] Figure 6B is a diagram showing a cross-sectional view of a target volume in an embodiment according to the present disclosure.

[0028] Figure 7 is an example showing comparison of dose volume histograms (DVHs) of conventionally determined candidate treatment plans and DVHs of candidate treatment plans determined in accordance with an embodiment of the present disclosure.

[0029] Figure 8 Characteristics of a proton beam in accordance with an embodiment of the present disclosure are shown.

[0030] Fig. 9 An example of a dynamic point focusing technique in an embodiment according to the present disclosure is shown.

[0031] Fig. 10A and Fig. 10B An example of a magnetic flux steering technique in an embodiment according to the present disclosure is shown.

[0032] Fig.11 is a flow chart of an example of a computer-implemented method for radiation treatment planning according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0033] Reference will now be made in detail to various embodiments of the present disclosure, 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 within the spirit and scope of the present disclosure defined by the appended claims. In addition, in the following detailed description of the present disclosure, many 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 implemented without these specific details. In other cases, well-known methods, procedures, components and circuits are not described in detail to avoid unnecessarily obscuring aspects of the present disclosure.

[0034] Some parts of the detailed description below are presented in the form of programs, logic blocks, processing and other symbolic representations of data bits in computer memory. These descriptions and representations are the means used by technicians in the field of data processing to most effectively convey the content of their work to other technicians in the field. In this application, programs, logic blocks, processes, etc. are considered to be self-consistent steps or instruction sequences that lead to desired results. These steps are steps that utilize physical manipulation 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 computer system. Sometimes, mainly for commonly used reasons, it has proven to be convenient to refer to these signals as transactions, bits, values, elements, symbols, characters, samples, pixels, etc.

[0035] It should be remembered, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless expressly stated otherwise, as will be apparent from the following discussion, it should be understood that discussions throughout this disclosure using terms such as "access," "determine," "store," "partition," "optimize," "minimize," "maximize," "generate," "generate," "evaluate," "compute," "select," "graphically represent," and the like refer to computer systems or similar electronic computing devices or processors (e.g., Figure 1 computer system 100) actions and processes (e.g., Fig.11 A computer system or similar electronic computing device manipulates and transforms data represented as physical (electronic) quantities in a computer system memory, registers, or other such information storage, transmission, or display device.

[0036] Parts of the following detailed description are presented and discussed in the form of methods or processes. Although operations and their sequences are disclosed herein, these operations and sequences are only examples. Embodiments are very suitable for performing various other operations or variations of the operations described herein.

[0037] The embodiments described herein may be discussed in the general context of computer-executable instructions residing on some form of computer-readable storage media, such as program modules, that are 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. Typically, program modules include routines, programs, objects, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The functionality of the program modules may be combined or distributed as desired in various embodiments.

[0038] Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, random access memory, 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 or magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed to retrieve that information.

[0039] Communication media can embody computer executable instructions, data structures, and program modules, and include any information delivery media. As an 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). Any combination of the above may also be included within the scope of computer-readable media.

[0040] Nomenclature

[0041] The term "spatially separated beams" includes appropriately oriented and spaced GRIDs, lattices, beamlets, pencil beams (spot scanning beams), and microbeams. Microbeams can be distinguished from other types of beams by their size. The full width at half maximum (FWHM) of a microbeam may be in the range of less than two millimeters (mm), while other types of beams are larger. For example, the FWHM of a pencil beam or beamlet may be in the range of 4-5 mm. For ease of discussion, the term "beam" is used herein in the most general manner to include beams of any size unless otherwise stated or apparent from the discussion.

[0042] The discussion that follows may include terms such as "dose," "dose rate," and the like. Unless otherwise stated, each such term is associated with a value. For example, dose has one value and can have different values. For simplicity, each of these terms refers to its value unless otherwise stated or apparent from the discussion.

[0043] Figure 1 1 shows a block diagram of an example of a computer system 100 on which embodiments described herein may be implemented. In its most basic configuration, the system 100 includes at least one processing unit 102 and a memory 104. The most basic configuration is Figure 1 The system 100 may also have additional features and / or functionality. For example, the system 100 may also include additional storage (removable and / or non-removable), including but not limited to magnetic or optical disks or tapes. Such additional storage may be provided in the form of a plurality of storage devices, such as a plurality of storage devices, and / or a plurality of storage devices. Figure 11 and 2. The system 100 is shown in FIG. 1 by removable storage 108 and non-removable storage 120. The system 100 may also include 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.

[0044] The system 100 also includes an input device 124, such as a keyboard, a mouse, a pen, a voice input device, a touch input device, etc. It may also include an output device 126, such as a display device, a speaker, a printer, etc. The display device may be, for example, a cathode ray tube display, a light emitting diode display, or a liquid crystal display.

[0045] exist Figure 1 In the example of , the memory 104 includes computer readable instructions, data structures, program modules, etc. associated with a treatment planning system (TPS) 150, which may also be referred to as an optimizer. However, the TPS 150 may reside in any of the computer storage media used by the computer system 100, or may be distributed on some combination of computer storage media, or may be distributed on some combination of networked computers. The TPS 150 is used to generate and evaluate candidate (suggested) treatment plans and produce a final (optimized) treatment plan. The proposed radiation treatment plan is defined using the TPS 150, stored in the computer system memory, and accessed from the memory.

[0046] The radiation treatment plan may be converted (e.g., by TPS 150) into a program for configuring and controlling the treatment system (e.g., Figure 4 400). Depending on the treatment type, the machine parameters may include, but are not limited to, beam current for charged particle, ion or photon beam intensity, the number of charged particles, ions or photons emitted by the accelerator per time period, magnet current, settings to achieve a specified energy of protons, ions or photons at the target volume, and the measurement range of the dose monitoring system.

[0047] During processing, in one example embodiment, the beam enters a nozzle of a processor, which may include one or more components that affect (e.g., reduce, adjust) the energy of the beam to control the dose / dose rate delivered by the beam and / or control the dose-to-depth profile of the beam, depending on the type of beam. For example, for a beam having a Bragg peak, the nozzle may control the position of the Bragg peak in a processing target transverse to the beam axis.

[0048] Example of Automating the Radiological Treatment Planning Process

[0049] The proposed radiation treatment plan includes parameter values ​​that may affect the dose and / or dose rate as well as other parameters. These parameters depend on the treatment mode. In an embodiment of the present disclosure, the treatment mode includes spatially fractionated radiation therapy (SFRT), including intensity modulated radiation therapy (IMRT) and intensity modulated particle therapy (IMPT).

[0050] Depending on the treatment mode, parameters may include, but are not limited to: beam shape; beam collimation; number and arrangement of spots; spot weight; beam weight; beam intensity or energy; beam direction; prescribed dose and prescribed dose rate; number of irradiations of the target volume; duration of each irradiation (irradiation time); and dose deposited in each irradiation. Parameters may also include the time period over which the irradiations are applied (e.g., multiple irradiations are applied over a time period such as one hour, with each irradiation within the time period separated from the next by another time period; although the treatment period may be relatively long, a single beam transit time may be less than or even much less than one second) and the time interval between each irradiation (e.g., each hour-long time period is separated from the next by a day).

[0051] The large number of parameters and their range of values ​​can result in a virtually unlimited number of potential treatment plans, so 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 given the time constraints associated with the use of radiation therapy to treat diseases such as cancer, and the large number of patients who are receiving or need to receive radiation therapy in any given period of time.

[0052] Figure 2 2 is a block diagram illustrating an example of an automated radiation treatment planning process 200 in accordance with an embodiment of the present disclosure. The process 200 may be implemented in whole or in part as a software program, hardware logic, or a combination thereof on a computer system 100 ( Figure 1 ) on / using computer system 100 to implement.

[0053] exist Figure 2 In block 202 of the present invention, a three-dimensional (3D) image of the patient is acquired, and organs and other structures within the patient (patient geometry) can be segmented and delineated. In blocks 204 and 206, information from block 202 and other information such as the information described above are used to develop and evaluate candidate treatment plans, as described below in conjunction with Figure 3 Further description.

[0054] In block 208, if the candidate treatment plan is satisfactory (e.g., it meets the clinical objectives), then the plan can be used to treat the patient. If not, aspects of the treatment plan and / or clinical objectives can be iteratively modified until a satisfactory plan is generated. The clinical objectives can be represented by, for example, a set of quality indicators, such as target homogeneity, consistency with treatment targets, critical organ preservation, etc., where the quality indicators have respective target values. A dose volume histogram (DVH) or other type of graphical representation can be used to evaluate the treatment plan to determine whether the treatment plan meets the clinical objectives. For example, if the DVH based on the plan meets a specified dose threshold of a specified percentage of the target volume, then the treatment plan can be considered satisfactory.

[0055] Figure 3 300 is a block diagram illustrating an example of an automated radiation treatment planning process 300 in accordance with an embodiment of the present disclosure. The process 300 may be implemented in whole or in part as a software program, hardware logic, or a combination thereof on a computer system 100 ( Figure 1 ) is implemented on / using computer system 100. Process 300 generally corresponds to Figure 2 Blocks 204 and 206.

[0056] exist Figure 3 In the example of Figure 1 The memory 104 of the TPS 150 includes information of the above parameters. The TPS 150 may also access or receive information specific to the patient to be treated (e.g., patient geometry), including information describing the treatment target (region of interest, ROI), which may include a planning target volume (PTV), a gross tumor volume (GTV), a clinical target volume (CTV), and organs at risk (OARs).

[0057] The TPS 150 also accesses or receives an objective function defined for treating the patient. An objective function is a mathematical formula of variables (such as the above parameters) that can have an effect on achieving the specified clinical goals. More specifically, the objective function is used to evaluate candidate radiation treatment plans to determine whether the clinical goals specified for treating the patient are met.

[0058] Example Processing System

[0059] Figure 4 4 is a block diagram illustrating selected components of a radiation therapy or treatment system 400 upon which embodiments of the present invention may be implemented. Figure 4 In the example of FIG. 4 , system 400 includes a beam system 404 and a nozzle 406 .

[0060] The beam system 404 generates and transmits a beam. In an embodiment, depending on the type of beam, the beam system 404 includes components that direct (e.g., bend, steer, focus, or direct) the beam in the direction of a nozzle 406. The beam system 404 may also include components for adjusting (e.g., reducing or regulating) the energy of the beam entering the nozzle 406. The nozzle 406 is used to aim or direct the beam to various locations or points in a target volume within a patient supported on a patient support 408 (e.g., a chair or table) in a treatment chamber. The nozzle 406 can be mounted on a gantry or on a portion of a gantry that can move relative to the patient support 408, and the patient support 408 can also move. The nozzle 406 may also include components for directing the beam and / or adjusting the energy of the beam. As described below in Fig. 9 , 10A Further information is provided in the discussion of 10B.

[0061] The control system 410 implements the prescribed or optimized or final radiation treatment plan 420 received from the TPS 150 (see, e.g., Figure 1 In an embodiment, the control system 410 includes a computer system having a processor, a memory, an input device (e.g., a keyboard), and a display, similar to Figure 1 The control system 410 may receive data related to the operation of the system 400. The memory of the control system 410 stores a radiation treatment plan 420 to be implemented using the system 400. Specifically, the memory of the control system 410 includes computer readable instructions, data structures, program modules, etc. related to the radiation treatment plan 420. The control system 410 may 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 radiation treatment plan 420, including parameters such as the energy, intensity, direction, size, and / or shape of the beam.

[0062] Correction factors in treatment plans

[0063] In general, the embodiments disclosed herein simulate the expected sparing effect due to the spatial distribution of dose in treatment modes, including but not limited to general SFRT, in particular proton-SFRT with enhanced dose rate (EDR), ultra-high dose rate (UHDR), and proton beams with extended Bragg peak (SOBP) or transmitted proton beams (e.g., transmitted-SFRT).

[0064] In embodiments according to the present disclosure, new correction factors or indices that may be related to retention effects are introduced into the treatment planning process. In embodiments, a correction factor / indicator referred to herein as the Critical / Repair Ratio Index (CRI) is introduced. In embodiments, a correction factor / indicator referred to herein as the Spatial Periodicity of Critical Iso-dose Values ​​(SP-CIV) is introduced. CRI is discussed first below, followed by SP-CIV.

[0065] Embodiments according to the present disclosure may be used for radiation treatment or therapy (RT) modes including, but not limited to: CONVERT (simultaneous once-daily and twice-daily RT), enhanced dose rate (EDR) RT, UHDRRT, and FLASHRT. Typically, for each of these modes, the dose is determined by the treatment system (e.g., Figure 4 CONVERT delivers a dose rate ranging from zero to one Gray per second (Gy / s). EDR is defined as a dose rate ranging from 1 to 40 Gy / s. UHDR is defined as a dose rate greater than 40 Gy / s. FLASHRT is a special case of UHDRRT where, in addition to the dose rate, the expected tolerance of healthy tissue is greater than the expected tolerance of a low dose rate due to the so-called "FLASH effect." Specifically, embodiments according to the present disclosure include SFRT, EDRRT, UHDRRT, FLASHRT, and a combination of a transmitted proton beam or a proton beam with SOBP.

[0066] Figure 5 Three spatially segmented proton beams 501, 502, and 503 are shown. In actual operation, there may be any number of such beams. The beams 501-503 are not necessarily delivered simultaneously; that is, they may or may not be segmented in time.

[0067] The beams 501-503 may be focused into the target volume 505 with a collimator, or may be focused into the target volume with a scanning magnet, or both, depending on the treatment mode. In an embodiment, the respective ranges of the beams 501-503 are adjusted so that their respective Bragg peaks are located within the target volume 505. In general, as will be seen from the following discussion, a uniform healing dose is delivered across the target volume 505 by the spatially segmented beams 501-503.

[0068] Critical / Repair Ratio Index (CRI)

[0069] CRI is a metric that considers the area of ​​a given isodose surface or contour outside the target volume in addition to the volume defined by this surface. More specifically, CRI optimizes (maximizes) the surface area of ​​critical isodose surfaces / contours during treatment planning. In principle, this metric enables planners and clinicians to better assess the DVH and even apply correction factors to the DVH of SFRT (e.g., proton-SFRT) treatment plans. When using the metric with correction factors, the DVH can better take into account the expected savings in the spatial distribution of dose in the above-mentioned treatment modes. When using the metric without correction factors, it allows to distinguish between treatment plans with equivalent acceptable DVH distributions but with different CRIs. Depending on the treatment planning strategy, the target volume can be covered by a SOBP or a transmitted proton beam to optimize and / or homogenize the dose distribution at the target level, but still benefit from the sparing effect of SFRT at the healthy tissue level.

[0070] Fig. 6A 602 is a diagram showing a cross-sectional view of a target volume 505 including a tumor 602 in an embodiment according to the present disclosure. The target volume 505 may include tissue other than the tumor 602 (e.g., tissue surrounding the tumor). Fig. 6A In the example of Figure 5 The beam in the example) passes through other tissues in the patient from the direction shown, toward the target volume 505 and enters the target volume 505. Fig. 6A In the example of FIG. 6 , the other tissues include a severe lesion isodose volume 606 and a repair volume isodose volume 608 through which the spatially segmented beam passes. A repair interface 610 is located at the interface of the severe lesion isodose volume 606 and the repair volume isodose volume 608 .

[0071] In an embodiment, the repair interface 610 is an isodose surface or contour (a surface passing through isodose points in tissue outside the target volume 505), and the severe lesion isodose volume 606 is a volume defined by the repair interface. Therefore, the repair interface 610 represents the surface of the severe lesion isodose volume 606. In an embodiment, the severe lesion isodose volume 606 is the volume of overlap between the organ at risk and the isodose surface (e.g., the repair interface 610).

[0072] In this example, the shape or outline of the repair interface 610 is as follows: Fig. 6A The irregularities shown may have peaks that coincide with the paths of incident spatially segmented beams and valleys that coincide with the spacing between these beams. Conventional treatment planning systems and methods do not take into account the irregular contours of the repair interface 610. In contrast, in embodiments according to the present disclosure, the irregular contours (e.g., Figure 1 ).

[0073] In the embodiments, still refer to Fig. 6A , the objective function for determining the CRI value is defined as the volume of the severe lesion isodose volume 606 divided by the surface area of ​​the repair interface 610. The goal during treatment planning is to minimize the value of the CRI by maximizing the surface area of ​​the repair interface 610. In practice, as further described below, there may be several other objective functions in addition to the CRI, whose values ​​need to be minimized to achieve an optimal final treatment plan.

[0074] Ideally, during planning and actual treatment, the dose will be delivered primarily to the target volume 505, while the dose delivered to the severe lesion isodose volume 606 and the repair volume isodose volume 608 will be minimized. Figure 7 is an example showing a comparison of a DVH 712 of a conventionally determined candidate processing plan (without CRI) and a DVH 714 of a candidate processing plan (with CRI) determined in accordance with the present disclosure.

[0075] exist Figure 7 In the example, refer to Fig. 6A , region 705 corresponds to the target volume 505, region 706 corresponds to the severe lesion isodose volume 606, and region 708 corresponds to the repair volume isodose volume 608. From this example, it can be seen that DVH 714 is shifted relative to DVH 712, indicating that by incorporating CRI into the treatment planning process, a smaller volume of healthy tissue is expected to receive a dose.

[0076] Embodiments according to the present disclosure are not limited to the use of the DVH just described. For treatment planning, TPS150 can graphically represent (display) the results of the CRI calculation in different ways to facilitate planners and clinicians or TPS itself (within TPS) to evaluate different candidate treatment plans. In an embodiment, the graphical representation includes a display of isodose values ​​along the x-axis and values ​​of the surface area of ​​the repair interface 610 along the y-axis. As described above, the goal during treatment planning is to minimize the value of the CRI by maximizing the surface area of ​​the repair interface 610, so this display can be used to evaluate candidate treatment plans.

[0077] Spatial Periodicity of Critical Isodose Values ​​(SP-CIV)

[0078] SP-CIV is a metric that, in general, constrains the surface of the repair interface 610 so that it does not go within a certain distance of itself; that is, so that it does not fold back on itself. In a simple case, consider an example where there are concentric rings of equal dose values, in which case SP-CIV is used to constrain the minimum and / or maximum values ​​between these rings.

[0079] refer to Figure 6B, line segment 621 represents the maximum distance between the same isodose values ​​on the repair interface 610, and line segment 622 represents the minimum distance between the same isodose values ​​(each within a certain radius). That is, given a point on the contour of the repair interface 610, a search can be performed (for example, by TPS150) within a certain radius of the point to determine the maximum distance and the minimum distance represented by line segments 621 and 622, respectively. SP-CIV can have a maximum value, or can have a minimum value, or its maximum and minimum values ​​can be determined. Figure 6B In the example of , the maximum value of SP-CIV is the length of line segment 621, and the minimum value of SP-CIV is the length of line segment 622. TPS 150 may use one or both of the maximum value and the minimum value of SP-CIV.

[0080] In one embodiment, the repair interface 610 can be modeled as a waveform with peaks and valleys, and the maximum SP-CIV and / or minimum SP-CIV can be calculated using a Fourier transform that finds the maximum frequency (spatial periodicity) and / or minimum frequency (spatial periodicity) of the dose distribution or profile given by the repair interface 610.

[0081] In an embodiment, the maximum SP-CIV cannot be greater than a first specified limit. Similarly, in an embodiment, the minimum SP-CIV cannot be less than a second specified limit. Typically, the spatial periodicity of the repair interface 610 is constrained to be within a range between a minimum limit and a maximum limit.

[0082] Radiation treatment / therapy

[0083] As described above, embodiments according to the present disclosure can be used for different RT modes. Some embodiments according to the present disclosure combine SFRT, EDR or UHDR and a transmitted proton beam or a proton beam with SOBP. In these embodiments, the beam can be focused using a collimator or using a scanning magnet or both, as previously described herein. Due to this combination, a uniform healing dose is delivered over the entire target volume during treatment of the patient by the spatially segmented beam.

[0084] Another advantage of combining SFRT, EDR, or UHDR with transmitted proton beam or proton beam with SOBP is that patient motion is mitigated during treatment. Figure 8 A simplified pattern 800 of a proton beam measured by a detector at any point on a profile perpendicular to the beam axis in an embodiment according to the present disclosure is shown. Even with motion, pattern 800 exhibits a stable peak-to-valley ratio and a stable peak-to-peak distance, similar to a pattern measured without motion.

[0085] Space division conveying technology

[0086] Various techniques can be used to deliver spatially segmented beams in general and perform SFRT using EDR or UHDR proton beams, including transmitted proton beams or in particular proton beams with SOBP to achieve a proton beam with a stable peak-to-valley ratio and a stable peak-to-peak distance (e.g. Figure 8 ), and delivers a uniform healing dose across the entire target volume.

[0087] Fig. 9 An example of a dynamic point focusing technique in accordance with an embodiment of the present disclosure is shown. In this example, two spatially divided beams 901 and 902 are shown as being processed by a processor (e.g., Figure 4 However, the present disclosure is not limited thereto. Beams 901 and 902 may or may not be time-divided and space-divided.

[0088] In dynamic point focusing technology, Fig. 9 The beams 901 and 902 in the embodiment are dynamically focused at the interface 904 between the patient and the surrounding environment (air). The dynamic focusing of one beam can be performed independently of any other beam. In addition to the interface 904, the focal points of the beams 901 and 902 can be located at a point that optimizes (minimizes) the value of the metric CRI while still achieving the prescribed dose or the curative dose.

[0089] This dynamic focusing technique can be used to account for and mitigate patient motion during treatment. That is, the focus of beams 901 and 902 can be changed during treatment to compensate for any patient motion.

[0090] like Fig. 9 As shown in the example of , once the beam enters the patient, the width of the beam begins to widen, and the beam continues to widen as the depth increases. In order to take advantage of the widening characteristics of beams 901 and 902, it is best to focus the beams at the entry point (e.g., interface 904). This allows beams 901 and 902 to overlap at the target volume, which helps deliver a uniform healing dose throughout the target volume. However, it is also best for beams 901 and 902 to be as narrow as possible outside of target volume 505 to reduce the extent to which healthy tissue is irradiated. Focusing each of beams 901 and 902 at interface 904 helps achieve both of these goals.

[0091] Fig. 10A An example of a "zigzag" (e.g., double-bend) magnetic beam steering technique in accordance with an embodiment of the present disclosure is shown. In this example, a nozzle (e.g., Figure 4 The nozzle 406 of the processing system 400 includes a set of focusing magnets 1002 and a set of scanning magnets 1004. The nozzle 406 includes other components known in the art.

[0092] In accordance with Fig. 10A In an exemplary embodiment of the present invention, the handler includes additional magnet groups 1006 and 1008, which are coupled to the nozzle 406 (externally) or integrated into the nozzle (internal). In these embodiments, the first group of magnets 1006 includes a first pair of magnets 1006a and 1006b, and the second group of magnets 1008 includes a second pair of magnets 1008a and 1008b. In an embodiment, magnets 1006a and 1006b are located on opposite sides of the beam path, facing each other along the beam path, and magnets 1008a and 1008b are located on opposite sides of the beam path, facing each other along the beam path. In an embodiment, magnet groups 1006 and 1008 are located in the same plane. However, embodiments according to the present disclosure are not limited to the configuration just described. Typically, a meander line (e.g., double bend) magnetic beam steering technique includes a group of magnets (e.g., group 1006) along the x-axis of the beam path and another group of magnets (e.g., group 1008) along the y-axis of the beam path. In an embodiment, the scanning magnet set 1004 is not present in the handler.

[0093] refer to Fig. 10B , a first set of magnets 1006 turns the beam 1012 outward relative to its initial path, while a second set of magnets 1008 turns the beam back to a location or point in the target volume 505. Magnet sets 1006 and 1008 can each be controlled in a complementary manner to direct the beam to different points in the target volume 505; that is, the magnet sets can control the angle of the beam so that the beam enters the target volume at different points and at different angles. The characteristics (e.g., field strength) of magnet sets 1006 and 1008 can be changed dynamically and rapidly so that the beam can be quickly delivered to multiple locations in the target volume 505 from different directions.

[0094] The nozzle 406 (including the magnet groups 1006 and 1008) can also be moved relative to the target volume 505 (e.g., around the periphery of the patient or target volume) to allow the beam to be delivered from different directions. In general, the meander line magnetic beam steering technology, in conjunction with the position of the nozzle 406, allows the beam to be delivered to the target volume 505 from multiple different angles.

[0095] As described above, the beam widens as it passes through the patient, so the beams overlap in the target volume 505. Thus, using this meander line magnetic beam steering technique, the beam can deliver a uniform healing dose across the entire target volume 505 while producing a spatially fractionated dose in healthy tissue.

[0096] Furthermore, the beam may have a SOBP, and the range of the beam may be controlled in a known manner to control the depth (position) of the SOBP inside the target volume 505. This further facilitates delivery of a uniform dose across the target volume 505.

[0097] This meander line magnetic beam steering technique can also be used to account for and mitigate patient motion during treatment. That is, the direction of the beam can be adjusted during treatment to compensate for any patient motion.

[0098] The meander line magnetic beam steering technique is not limited to two sets of magnets. In some embodiments, the processor includes a third set of magnets and a fourth set of magnets (not shown). The third set of magnets includes a third pair of magnets and the fourth set of magnets includes a fourth pair of magnets. The third set of magnets and the fourth set of magnets are located in the same plane and the plane is orthogonal to the plane of the first and second sets of magnets 1006 and 1008. The third set of magnets and the fourth set of magnets function similarly to the first and second sets of magnets 1006 and 1008, but steer the beam in a different direction toward the target volume 505.

[0099] In an embodiment, both dynamic focusing techniques and meander line magnetic beam steering techniques are used to focus and steer the beam.

[0100] Plan treatment method

[0101] Fig.11 1100 is a flowchart of an example of a computer-implemented method for radiation therapy planning in accordance with an embodiment of the present invention. The operations of flowchart 1100 may be implemented as a computer program that resides on some form of computer-readable storage medium (e.g., on a computer-readable medium). Figure 1 ) in the memory of the computer system 100 (e.g., Figure 1 TPS150).

[0102] Although Fig.11 The operations in the flowchart are shown as being performed in a sequential and specific order, but the present invention is not limited thereto. These operations can be performed in different orders and / or in parallel, and they can also be performed in an iterative manner to obtain the best results.

[0103] As described above, due to the need to consider different parameters, the range of values ​​of these parameters, the relationship between these parameters, the need for the treatment plan to be effective while minimizing the risk to the patient, and the need to quickly generate a high-quality treatment plan, the computer system 100 ( Figure 1 ) is very important to perform the radiation treatment plans disclosed herein using a treatment planning system 150 that executes consistently on the system.

[0104] exist Fig.11 In block 1102, a radiation treatment plan (eg, a candidate treatment plan) is obtained from a computer system memory. The treatment plan includes information describing the spatial distribution of the radiation beam.

[0105] In block 1104, a volume of tissue outside the target volume and intersecting the radiation beam is determined (eg, Fig. 6ADose distribution in the severely compromised isodose volume 606).

[0106] exist Fig.11 In block 1106 of , a metric value is determined for the treatment plan as a function of the dose distribution in the tissue volume.

[0107] In some embodiments, the metric is CRI and the value of the metric is determined using an objective function that is a measure of tissue volume (e.g., Fig. 6A The value of the surface area amount is the maximum value of the isodose surface depicting the tissue volume.

[0108] In some embodiments, the metric is SP-CIV, and the value of the metric is determined using an objective function that calculates the spatial periodicity of the isodose surface, and the spatial periodicity is constrained by at least one of a maximum value and a minimum value.

[0109] In some embodiments, CRI and SP-CIV indicators are used.

[0110] exist Fig.11 At block 1108 , the radiation treatment plan is evaluated to determine whether the plan meets the clinical goals of the radiation treatment.

[0111] The operations of blocks 1102-1108 may be repeated for any practical number of treatment plans to identify and select a set of one or more candidate treatment plans that meet the clinical goals. In block 1110, each selected treatment plan may be evaluated (optimized) to determine a final (optimized) treatment plan that may be used to treat the patient.

[0112] In an embodiment, optimizing a treatment plan includes determining a minimum of an overall target (e.g., cost) function that includes the sum of the objective functions of the plan, including objective functions based on CRI and / or SP-CIV. For example, the planner defines a set of quality indicators. For the plan, the indicators are defined such that smaller values ​​take precedence over larger values. The planner also defines a relative priority or weight for each quality indicator. The task of developing an optimal plan is then formulated as a quadratic objective function. The optimal plan is determined by minimizing the objective function.

[0113] In practice, clinical goals may conflict with one another, that is, not all clinical goals can be met by any particular treatment plan. When clinical goals conflict, multi-criteria optimization (MCO) can be used to optimize the treatment plan. Some or all of the parameter values ​​of each candidate radiation treatment plan can be iteratively adjusted to determine a final set of parameter values ​​for each plan (e.g., spatial distribution of the radiation beam, beam weight, intensity or energy, and direction, and other parameters previously described herein) to produce a plan that meets the patient's treatment goals (clinical goals) and minimizes the overall function of the plan. For example, a dose prediction model (e.g., Figure 1 elements of the TPS 150) to generate alternative results of various combinations of adjustable parameters, and the objective function can be calculated for the various alternative results until a minimum or satisfactory value of the objective function is found.

[0114] In an embodiment, the candidate treatment plan that produces the overall objective function value that is closest to the minimum (relative to other proposed plans) can be identified as the optimized treatment plan. Information about the optimized treatment plan can be presented to the user (e.g., in a display that includes data about the dose distribution, such as DVHs for various volumes of interest). The planner can iterate the planning process, for example, by adjusting weights in the overall objective function and / or by adjusting clinical goals. Once a final optimized treatment plan is determined, the adjustable processor parameters corresponding to the final optimized treatment plan can be provided to the radiation treatment system in a machine-readable form, and the radiation treatment system can then be operated according to the plan to provide radiation therapy to the patient.

[0115] In another embodiment, the optimization algorithm selects a final optimized treatment plan from among different candidate plans as the plan having the best (e.g., minimum) CRI value for a given isodose range, and / or the plan having the SP-CIV that best meets the minimum and / or maximum limits for that metric.

[0116] In block 1112, in some embodiments, information for configuring a focus of the radiation beam is determined, wherein the focus is located at an interface between air and the patient.

[0117] In block 1114, in some embodiments, information for configuring magnets that control the direction of the radiation beam is determined, wherein the magnets include: a first set of magnets that steer the radiation beam outward from its initial path, and a second set of magnets that are located downstream of the first set of magnets and will steer the beam to a location in the target volume.

[0118] The methods disclosed herein may also be applicable to stereotactic radiosurgery and stereotactic radiotherapy of single or multiple metastases.

[0119] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

[0120] Embodiments of introducing one or more new indices into a treatment planning process are disclosed. More specifically, a correction factor / indicator referred to herein as a critical / repair ratio index is introduced, and / or a correction factor / indicator referred to herein as a spatial periodicity of critical isodose values ​​is introduced. By using these indices, the expected savings in dose spatial distribution are better taken into account in the treatment mode, including spatially fractionated radiation therapy (SFRT) in general and SFRT with ultra-high dose rates in particular. Depending on the treatment planning strategy, the target can be covered by an extended Bragg peak to optimize and / or homogenize the dose distribution at the target level, but still benefit from the sparing effect of SFRT at the healthy tissue level. Delivery techniques include dynamic focusing techniques and magnetic beam steering techniques. The enhanced dose rate can maximize the peak-to-valley dose distribution of SFRT despite patient motion.

Claims

1. A computer system comprising: processor; as well as a memory coupled to the processor and comprising instructions that, when executed, cause the processor to perform a method for planning radiation treatment of a target volume of a patient, the method comprising: accessing from the memory a first candidate radiation treatment plan, the first candidate radiation treatment plan comprising information describing a spatial distribution of a radiation beam; determining a distribution of dose in a volume of tissue outside the target volume and intersecting the radiation beam; determining a value of a metric as a function of the distribution of the dose in the volume of the tissue; and The first candidate radiation treatment plan is evaluated using the value of the metric.

2. The computer system of claim 1 , wherein said determining said value of said metric comprises: determining a value of the amount of the volume of the tissue, wherein the volume of tissue is delineated by an isodose surface; as well as determining a value for a quantity of surface area of ​​said volume of said tissue; Wherein the value of the metric is the value of the amount of the volume of the tissue divided by the value of the amount of the surface area.

3. A computer system according to claim 1 or 2, wherein the determining the value of the metric comprises determining a spatial periodicity of an isodose surface depicting the volume of tissue, wherein the spatial periodicity of the isodose surface is constrained by at least one of a maximum value and a minimum value.

4. The computer system of claim 1, 2 or 3, further comprising maximizing the value of the amount of surface area of ​​an isodose surface delineating the volume of tissue.

5. The computer system according to any one of claims 1 to 4, wherein the evaluation further comprises: determining a value of the metric corresponding to each candidate radiation treatment plan of a plurality of candidate radiation treatment plans including the first candidate radiation treatment plan; as well as A radiation treatment plan having a smallest corresponding value of the metric is selected from the plurality of candidate radiation treatment plans.

6. The computer system of any one of claims 1 to 5, wherein the volume of the tissue is a volume selected from the group consisting of: a volume between an isodose surface and the target volume, and an overlap volume between an organ at risk and an isodose surface. 7 . The computer system of claim 1 , wherein the method further comprises determining a dose-volume histogram based on the distribution of the dose in the volume of the tissue and the distribution of the dose in the target volume.

8. The computer system of any one of claims 1 to 7, wherein the evaluation produces a final radiation treatment plan configured to provide a curative dose across the target volume.

9. The computer system of any one of claims 1 to 8, wherein the radiation beam is a proton beam, and wherein a processing system is capable of delivering the dose to the volume of tissue in less than one second.

10. A computer system according to any one of claims 1 to 9, wherein the method further comprises determining information for configuring a focus of the radiation beam, and wherein the focus is located at a point selected from the group consisting of: a point at an interface between air and the patient, and a point that optimizes the value of the metric and provides a healing dose across the target volume.

11. A computer system according to any one of claims 1 to 10, wherein the method further includes determining information for configuring a plurality of magnets that control the direction of the radiation beam, wherein the plurality of magnets includes a first group of magnets that steer the radiation beam outward from its initial path, and wherein the plurality of magnets also includes a second group of magnets located downstream of the first group of magnets that steer the radiation beam toward a location in the target volume.

12. A system comprising: a beam system for generating a radiation beam; a nozzle coupled to the beam system and directing the radiation beam to a target volume; as well as a control system coupled to the beam system and the nozzle, the control system comprising a computer system including a processor and a memory coupled to the processor; wherein the memory stores a radiation treatment plan, the radiation treatment plan including information describing a spatial distribution of the radiation beam and a dose volume histogram (DVH) of the target volume and a volume of tissue outside the target volume and intersected by the radiation beam, wherein the DVH is based on a value of a metric as a function of the distribution of dose in the volume of tissue; and The beam system and the nozzle are controllable by the control system to deliver a dose to the target volume according to the radiation treatment plan.

13. The system of claim 12, wherein the value of the metric is equal to a value of an amount of the volume of the tissue divided by an amount of a surface area of ​​the volume of the tissue, wherein the volume of tissue is delineated by an isodose surface.

14. The system of claim 12 or 13, wherein the metric is a spatial periodicity of an isodose surface delineating the volume of tissue, wherein the value of the metric is constrained by at least one of a maximum value and a minimum value.

15. The system of claim 12, 13 or 14, wherein the volume of the tissue is a volume selected from the group consisting of: a volume between an isodose surface and the target volume, and an overlap volume between an organ at risk and an isodose surface.

16. The system of any one of claims 12 to 15, wherein the dose for delivery to the target volume is a curative dose across the target volume.

17. The system of any one of claims 12 to 16, wherein the radiation beam is a proton beam, and wherein the system is configured to deliver the dose to the volume of tissue in less than one second.

18. The system of any one of claims 12 to 17, wherein the radiation treatment plan further comprises information for configuring a focus of the beam, and wherein the focus is a point selected from the group consisting of: a point at an interface between air and the patient, and a point that optimizes the value of the metric and provides a curative dose across the target volume.

19. The system of any one of claims 12 to 18, further comprising a plurality of magnets for controlling the direction of the beam, wherein the plurality of magnets comprises a first set of magnets that steers the beam outward from its initial path, wherein the plurality of magnets further comprises a second set of magnets downstream of the first set of magnets that steers the radiation beam toward a location in the target volume, and wherein the radiation treatment plan further comprises information for configuring the plurality of magnets.

20. A computer-implemented method for planning radiation treatment of a target volume of a patient, the method comprising: accessing from a computer system memory a candidate radiation treatment plan, the candidate radiation treatment plan comprising information describing a spatial distribution of a radiation beam; determining a distribution of dose in a volume of tissue outside the target volume and intersecting the radiation beam; determining a value of the metric as a function of the surface area of ​​the isodose surface of the volume of tissue; as well as A determination is made using the value of the metric whether the candidate radiation treatment plan meets a clinical goal of the radiation treatment.

21. The computer-implemented method of claim 20, wherein said determining said value of said metric comprises: determining a value of the amount of the volume of tissue, wherein the volume of tissue is delineated by the isodose surface; as well as determining a value of the quantity of said surface area; Wherein the value of the metric is the value of the amount of the volume of the tissue divided by the value of the amount of the surface area.

22. The computer-implemented method of claim 20 or 21, wherein said determining the value of the metric comprises determining a spatial periodicity of an isodose surface delineating the volume of tissue, wherein the value of the metric is constrained by at least one of a maximum value and a minimum value.

23. The computer-implemented method of claim 20, 21 or 22, further comprising determining a dose-volume histogram based on the distribution of the dose in the volume of the tissue and the distribution of dose in the target volume.

24. The computer-implemented method of any one of claims 20 to 23, wherein the volume of the tissue is a volume selected from the group consisting of: a volume between the isodose surface and the target volume, and an overlap volume between an organ at risk and the isodose surface.

25. The computer-implemented method of any one of claims 20 to 24, wherein the radiation beam is a proton beam, and wherein the dose can be delivered to the volume of tissue by a treatment system in less than one second.

26. The computer-implemented method of any one of claims 20 to 25, further comprising determining information for configuring a focus of the radiation beam, wherein the focus is a point selected from the group consisting of: a point at an interface between air and the patient, and a point that optimizes the value of the metric and provides a healing dose across the target volume.

27. The computer-implemented method of any one of claims 20 to 26, further comprising determining information for configuring a plurality of magnets that control the direction of the radiation beam, wherein the plurality of magnets comprises a first group of magnets that steers the radiation beam outward from its initial path, and wherein the plurality of magnets further comprises a second group of magnets downstream of the first group of magnets that steers the radiation beam toward a location in the target volume.

28. A system comprising: a beam system for generating a radiation beam, wherein the radiation beam is a proton beam; a plurality of magnets to control the direction of the radiation beam relative to the target volume; as well as a control system coupled to the beam system and the nozzle, the control system comprising a computer system including a processor and a memory coupled to the processor; wherein the memory stores a radiation treatment plan based on a metric for maximizing a surface area of ​​an isodose surface outside of the target volume; and Wherein the beam system and the nozzle are controlled by the control system according to the radiation treatment plan to deliver a dose to the target volume in less than one second.

29. The system of claim 28, wherein the value of the metric is equal to the amount of volume of tissue outside the target volume and intersected by the radiation beam divided by the amount of the surface area, and wherein the volume of tissue is delineated by the isodose surface.

30. The system of claim 29, wherein the volume of the tissue is a volume selected from the group consisting of: a volume between the isodose surface and the target volume, and an overlap volume between an organ at risk and the isodose surface.

31. The system of claim 28, 29 or 30, wherein the spatial periodicity of the isodose surface is constrained by at least one of a maximum and a minimum.

32. A system according to any one of claims 28 to 31, wherein the plurality of magnets includes a first group of magnets that steers the radiation beam outward from its initial path, and wherein the plurality of magnets also includes a second group of magnets located downstream of the first group of magnets that steers the beam toward a location in the target volume.

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