Systems and methods for proton flash arc therapy

Abstract

A method for generating a radiation treatment plan for proton FLASH arc therapy (PF AT) includes receiving at least one image of the region of interest of the subject, where the region of interest includes a target and performing arc selection based on the at least one image to determine a set of arcs. Each arc in the set of arcs is associated with at least one beam angle from a predetermined set of beam angles and one or more radiation beams. The method further includes identifying whether each voxel of the image in the region of interest is a normal tissue voxel or a voxel within the target, optimizing a temporal spread of dose delivery within the normal tissue voxels only, and storing the radiation treatment plan including at least the arc selection and the optimized temporal spread of the dose delivery within the normal tissue voxels.

Description

SYSTEMS AND METHODS FOR PROTON FLASH ARC THERAPYCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on, claims priority to, and incorporates herein by reference in its entirety U.S. Serial No. 63 / 534,595 filed August 25, 2023, and entitled “Proton FLASH Arc Therapy."STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under award number 1R21CA252562- 01 Al awarded by the National Cancer Institute. The government has certain rights in the invention.FIELD

[0003] The present disclosure relates generally to radiation treatment systems and, in particular, to systems and methods for proton FLASH arc therapy including generating and optimizing radiation treatment plans.BACKGROUND

[0004] The field of radiotherapy has witnessed significant advancements over recent decades aimed at improving treatment precision and reducing normal tissue toxicity. Among these, proton arc therapy (PAT) has emerged as a promising approach, offering potential dosimetric advantages compared to the use of static fields, as well as mitigation of range uncertainties and improved delivery efficiency. Proton arc therapy consists of spreading the angular incidences of proton beams when irradiating a tumor for therapeutic purposes. This can be achieved either by rotating the device emitting protons or by rotating the patient itself. In addition, in a recently developed modality of PAT, proton monoenergetic arc therapy (PMAT), a single energy can be used per angular point. In PMAT, use of partial monoenergetic proton beams, with centralized placement of spots inside a target (e.g., a tumor) as opposed to distal edge tracking, can achieve an enhancement of biological effect in the tumor by effectively placing high linear energy transfer (LET) beam components within the target instead of beyond the distal edge.

[0005] In parallel, FLASH radiotherapy (FLASH-RT) is a rapidly advancing field that offers enhanced normal-tissue sparing, and equivalent tumor control compared to conventional radiotherapy, via delivery of radiation at ultra-high dose rates. However, translating the pre- clinically observed FLASH sparing effect into clinical treatments is not straightforward. For proton pencil-beam scanning (PBS), the current clinical standard of proton treatments across many centers, the prolonged nature of per-layer scanning and energy-layer switching, as well as degrader losses at low proton energies presents a challenge for maintaining high dose rates.

[0006] As a result, new techniques must be developed to ensure sufficiently high dose rates in patient treatment plans, which often compromise on plan quality. For example, studies have suggested the use of transmission (“shoot-through”) proton beams, which sacrifice dose conformity and nullify the distal dose fall-off advantage of protons, in exchange for easier attainment of high dose rates. More recent developments have explored the use of static devices, such as ridge filters, to modulate the proton beam enabling exploitation of the Bragg peak while still maintaining high dose rates. However, these are patient- and field-specific devices that may often need to be re-manufactured in line with any plan adjustments. Ridge filters could also impose target volume limitations and potentially compromise dose distribution, particularly at the proximal tissue, among other challenges.

[0007] Various treatment planning studies have demonstrated the ability of techniques such as these to obtain dose rates across a radiation treatment plan that exceed the supposed FLASH threshold of 40 Gy / s, based on pre-clinical measurements from single-exposure electron treatments. A further significant challenge in the field is the lack of consensus on how dose rates should be defined in the context of FLASH sparing. Several definitions have been proposed and evaluated in planning studies, but given the limited understanding of the mechanism underlying the FLASH sparing effect, the “true” dose-rate requirement remains uncertain. For any dose rate definition, the notion of an onset of a FLASH sparing effect after a given threshold is also likely to be more complex than perceived.

[0008] It would be desirable to provide systems and methods to implementing FLASH-RT for clinical treatments.SUMMARY

[0009] In accordance with an embodiment, a method for generating a radiation treatment plan for proton FLASH arc therapy (PF AT) includes receiving at least one image of the region of interest of the subject, where the region of interest includes a target, performing, using a processor, arc selection based on the at least one image to determine a set of arcs, wherein each arc in the set of arcs is associated with at least one beam angle from a predetermined set of beam angles and one or more radiation beams, identifying, using the processor, whether each voxel of the image in the region of interest is a normal tissue voxel or a voxel within the target, optimizing, using the processor, a temporal spread of dose delivery within the normal tissue voxels only, and storing, using the processor and a storage device, the radiation treatment plan including at least the arc selection and the optimized temporal spread of the dose delivery within the normal tissue voxels.

[0010] In accordance with another embodiment, a system for generating a radiation treatment plan for proton FLASH arc therapy (PF AT) includes a memory that stores one or more computer readable media that includes instructions and one or more processor devices configured to execute the instructions of the computer readable media to receive at least one image of the region of interest of the subject, wherein the region of interest includes a target, perform arc selection based on the at least one image to determine a set of arcs, wherein each arc in the set of arcs is associated with at least one beam angle from a predetermined set of beam angles and one or more radiation beams, identify whether each voxel of the image in the region of interest is a normal tissue voxel or a voxel within the target, optimize a temporal spread of dose delivery within the normal tissue voxels only, and store the radiation treatment plan including at least the arc selection and the optimized temporal spread of the dose delivery within the normal tissue voxels.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements.

[0012] FIG. l is a schematic diagram of an example radiation treatment system in accordance with an embodiment;

[0013] FIG. 2 illustrates a method for generating a radiation treatment plan for proton FLASH arc therapy (PF AT) in accordance with an embodiment;

[0014] FIG. 3 illustrates a method for arc selection for a radiation treatment plan in accordance with an embodiment;

[0015] FIG. 4 illustrates a method for optimizing temporal spread of dose delivery for a radiation treatment plan in accordance with an embodiment;

[0016] FIG. 5 illustrates extracts from example dose-influence matrices in accordance with an embodiment;

[0017] FIG. 6 illustrates an example dose distribution and linear energy transfer (LET) distribution for a proton FLASH arc therapy treatment plan in accordance with an embodiment;

[0018] FIG. 7 illustrates an example dose distribution and linear transfer energy distribution for a proton FLASH arc therapy treatment plan in accordance with an embodiment;

[0019] FIG. 8 illustrates an example graph of a range of target water-equivalent depths (WEDs) for a plurality of beam angles in accordance with an embodiment;

[0020] FIG. 9 illustrates and example graph of energy-arc combinations in accordance with an embodiment;

[0021] FIG. 10 illustrates a method for delivering radiation therapy to a subject in accordance with an embodiment; and

[0022] FIG. 11 is a block diagram of an example computer system in accordance with an embodiment.DETAILED DESCRIPTION

[0023] FIG. 1 is a schematic diagram of an example radiation treatment system in accordance with an embodiment. In some embodiments, the radiation treatment system 100 may be used to perform one or more aspects of the methods described herein. The radiotherapy system 100 may generally include a delivery system 102, an imaging system 104, and a positioning system 106, each in communication with a treatment console 108. The delivery system 102 can include a radiation source and can be configured to generate and direct radiation (e.g., radiation beams) to a subject or patient 120 positioned on a treatment table 110, in accordance with a radiation treatment plan, where the treatment table 110 can be movable. The imaging system 104 may be configured to image the patient 120 before, during or after treatment. Although shown in FIG. 1 as a separate system, in some embodiments, the imaging system 104 may be part of, or combinedwith, the delivery system 102. In some embodiments, the imaging system 104 can be, for example, an x-ray source, a cone-beam CT system, a CT system, a 4DCT system, and the like. The positioning system 106 may be configured to position and orient the treatment table 110. In addition, the positioning system 106 may also be configured to move the patient 120 to the imaging system 104. In some embodiments, the treatment console 108 may be implemented on a computer system, for example, computer system 500 described below with respect to FIG. 5. In addition, various aspects of the delivery system 102, imaging system 104 and positioning system 106 may be implemented on a computer system, for example, using one or more processors (e.g., as described below with respect to FIG. 5).

[0024] The treatment console 108, or another suitable controller, may be configured to receive a radiation treatment plan from a planning workstation 112, or another location, such as a database 114, server 116, or cloud 118. Thereafter, the treatment console 108 may control the delivery system 102, imaging system 104, and positioning system 106 to execute the radiation treatment plan. During treatment, the delivery system 102 builds radiation dose inside a patient 120 to achieve dose distributions in accordance with the radiation treatment plan. The plan may include, for example, a number of treatment fields having various beam numbers, beam shapes or fluences, beam energies, beam orientations relative to the patient 120, and durations of exposure. The delivery system 102, for example, a linear accelerator (Linac) or other particle accelerator configured to accelerate particles (e.g., electrons, protons, etc.), can be moved about the patient 120 on the treatment table 110. Although not shown, in some embodiments, the delivery system 102 can include a gantry that supports one or more components of the delivery system 102 (e.g., a radiation source). The gantry can be moveable so that when the gantry moves, one or more components of the delivery system 102 moves with the gantry. In some embodiments, the gantry can be, for example, a cylinder gantry, a ring gantry, a C-arm gantry, etc. In some embodiments, the radiation treatment plan may also be executed using a combination of table 110 and delivery system 102 movements.

[0025] The planning workstation 112 may implement a treatment planning system that can be utilized to generate a radiation treatment plan based on dosimetric prescriptions and imaging information obtained from a subject 120 (e.g., using imaging system 104). for example, from one or more images (e.g., CT images) of a region of interest of the subject 120 including a target (e.g., a tumor) that are acquired, for example, before treatment. In some embodiments,generating the treatment plan includes selecting appropriate treatment beam (or fields), which can vary in number, duration, shape or fluence, energy and orientation relative to the patient, to optimize patient outcomes. In some embodiments, the planning workstation 112 and treatment planning system may be implemented on a computer system, for example, computer system 500 described below with respect to FIG. 5.

[0026] As mentioned, implementing ultra-high dose rate radiotherapy techniques such as, for example, FLASH-RT, clinically presents a number of challenges. Some studies optimize radiation treatment plans to achieve FLASH dose rates with the target or target region (e.g., a tumor). However, since FLASH-RT is a healthy tissue sparing phenomenon, it would be of greater benefit to focus on dose-rate optimization outside of the target region, for example, within healthy (or normal) tissue and / or organs at risk (OAR). In addition, while pre-clinical evidence suggests am inherent immunity of tumor tissue to FLASH-RT, the lack of a comprehensive parameter space for FLASH sparing necessitates caution in assuming universal resistance across all tumor sites in patients. Accordingly, prioritizing the delivery of FLASH ultra-high dose rates in healthy tissue only may be a more prudent approach until a clearer understanding of the full implications of FLASH-RT is established.

[0027] The present disclosure describes a system and method for generating a radiation treatment plan for proton FLASH arc therapy (PF AT). The system and method for generating a radiation treatment plan for PF AT can include optimizing a temporal spread of dose delivery within the normal tissue voxels only in a region of interest having a target (e.g., a tumor). In some embodiments, the optimization of the temporal spread of dose delivery within the normal tissue voxels can be configured to generate a radiation treatment plan that irradiates control points (or beam angles) outside of the target at one point in time, i.e., the dose to the healthy tissue voxels can be delivered individually by multiple spatially separated radiation beams. Advantageously, the irradiation of control points (or beam angles) outside of the target at one point in time can occur simultaneously with directing multiple overlapping beams to irradiate the target. This can result in high dose rates in the healthy (or normal) tissue while spreading out the dose delivery to the target over time. Accordingly, the dose distribution in the normal or healthy tissue in the regions of interest is constrained in time which can enhance the possibility of achieving FLASH sparing in the healthy tissue in the region of interest while minimizing any possibility of sparing effect within the target. In addition, irradiation at a single point in time orduring a small window in time can mitigate the disparity between different dose rate definitions (e.g., average dose rate, spot-wise dose rate) and eliminate the need for multiple dose rate definitions. The disclosed systems and methods can leverage the benefits of arc therapy while addressing FLASH ultra-high dose delivery concerns by spatially fractionating dose delivery to healthy tissue. The spatial fractionation of the dose to healthy tissue can be used to modulate the average dose rate at the points outside the target (e.g., healthy tissue) and cause it to tend towards the instantaneous dose rate of a single spot. In some embodiments, the number of spots influencing healthy tissue voxels can be reduced which can lead to regions of significantly higher dose rate in points or locations outside the target. In some embodiments, the disclosed systems and methods can also shift regions of elevate linear energy transfer (LET) away from the distal beam edge and towards the center of the target which can enhance the biological effect in the target.

[0028] FIG. 2 illustrates a method for generating a radiation treatment plan for proton FLASH arc therapy (PF AT) in accordance with an embodiment. The process illustrated in FIG. 2 is described as being carried out by the system illustrated in FIG. 1. However, in some examples, the process of FIG. 2 may be implemented by another system. Although the blocks of the process are illustrated in a particular order, in some embodiments, one or more blocks may be executed in a different order than illustrated in FIG. 2, or may be bypassed.

[0029] At block 202, one or more images of a region of interest of a subject may be received. In some embodiments, the region of interest can include a target or target site (e.g., a tumor, gross tumor volume (GTV), or clinical target volume (CTV)), normal (or healthy) tissue (e.g., within an external contour), or organ at risk (OAR). In some embodiments, the region of interest can be larger than the target. The one or more images of the region of interest of the subject can be acquired using an imaging system, for example imaging system 104 shown in FIG. 1 using known acquisition methods. In some embodiments, the one or more images of the region of interest of the subject can be computed tomography (CT) images acquired using a CT imaging system (e.g., imaging system 104 shown in FIG. 1). In some embodiments, the one or more images of the region of interest of the subject can be retrieved from data storage (or memory) of the radiation treatment system 100 (e.g., database 114, server 116, or cloud 118 shown in FIG. 1), or data storage of an imaging system (e.g., imaging system 104 shown in FIG. 1).

[0030] At block 204, an arc selection process can be performed, for example, using a treatment planning system such as mentioned above with respect to planning workstation 112 in FIG. 1, based on the one or more images of the region of interest of the subject to determine a set of arcs for the radiation treatment plan, where each of the arcs is associated with one or more radiation beams. In some embodiments, the arcs are proton arcs and the proton beams (i.e., radiation beams) can be continuously delivered as a gantry of a delivery system 102 rotates around the subject 120. In some embodiments, the arcs are monoenergetic partial arcs within a single 360° gantry rotation and the radiation beams are monoenergetic radiation beams. Accordingly, a single energy can be used per beam angle (or control point). For example, monoenergetic partial arcs can be selected to place spots in the middle of a target (e.g.., a tumor), for example, monoenergetic partial arcs within a single 360° gantry rotation can be selected to deposit Bragg’s peaks at the center part of the target to increase LET values. An example method for arc selection for a radiation treatment plan using monoenergetic partial arcs is described below with respect to FIG. 3. In some embodiments, the arc selection process can advantageously utilize energy selection to achieve a homogeneous dose distribution across the target while leveraging biological effectiveness enhancement within the target by ensuring Bragg peaks are not placed at the distal edge of the target.

[0031] At block 206, spots can be placed at each beam angle or control point within a partial arc (i.e., the beam angles associated with the partial arc, for example, as described below with respect to FIG. 3), using an energy of the partial arc (e.g., an energy calculated for the partial arc as discussed below with respect to FIG. 3). At block 208, a dose-influence matrix can be calculated for each partial arc. In some embodiments, the dose-influence matrix can be a nonweighted dose-influence matrix and can be determined using ray tracing. In some embodiments, the dose-influence matrix calculated for each partial arc can be used to constrain the temporal spread of the spot delivery to non-target regions of the radiation treatment plan. For example, the dose-influence matrices determined at block 208 can be used to approximate and show the number of spots which contribute dose to each voxel in the radiation treatment plan, and, therefore, by assuming a spot-wise delivery time, can be used to approximate the temporal distribution of dose delivery to that voxel.

[0032] FIG. 5 illustrates extracts from example dose-influence matrices in accordance with an embodiment. In FIG. 5, a contribution from each spot (vertical axis) to each voxel (horizontalaxis) in the radiation treatment plan is shown. In FIG. 5, voxels have been reshaped from 3- dimensional arrays to a 1 -dimensional list. In this example, the voxels include voxels 504 contained within the target (e.g., a GTV) and voxels 502 contained within a remaining external contour of the region of interest which represent the normal or healthy tissue. In FIG. 5, the voxels not identified with a reference number represent the remaining voxel in the CT image (e.g., the CT image(s) from block 202). In this example, the temporal distribution of dose delivered to a given voxel can be approximated by reading down the column for that voxel. FIG. 5 illustrates that for PF AT, for most of the normal tissue voxels 502, the dose is received from a small number of consecutive spots. In some embodiments, the temporal spot-range for a given voxel can be defined as the total number of spots delivered in the radiation treatment plan between the first and final spot that deliver any dose to that voxel. A smaller spot-range can imply a more constrained temporal dose delivery, such that a differentiation between different dose rate definitions (e.g.., average dose rate, spot-wise dose rate) can be mitigated, i.e., greater and more consistent dose rates from different definitions.

[0033] Returning to FIG. 2, at block 210, voxels can be identified or flagged as normal (or healthy) tissue (e.g., within an external contour of the region of interest but outside of the target), or as within the target. Identifying each voxel as normal or as within the target can be used to facilitate an optimization process for the temporal spread of dose delivery within the normal tissue voxels. At block 212, the temporal spread of dose delivery within normal tissue voxels only can be optimized. The optimization of the temporal spread of dose delivery within the normal tissue voxels can be configured to generate a radiation treatment plan that irradiates control points (or beam angles) outside of the target at one point in time, i.e., the dose to the healthy tissue voxels can be delivered individually by multiple spatially separated radiation beams. An example process for optimizing temporal spread of dose delivery for a radiation treatment plan is discussed below with respect to FIG. 4. Advantageously, the irradiation of control points (or beam angles) outside of the target at one point in time can occur simultaneously with directing multiple overlapping beams to irradiate the target. This can result in high dose rates in the healthy (or normal) tissue while spreading out the dose delivery to the target over time. At block 214, dose distributions and linear energy transfer (LET) distributions can be calculated. In some embodiments, the dose distribution and the LET distribution can be calculated using a Monte-Carlo simulation. In some embodiments, by incorporating deliveryinformation for specific radiation treatment machines (e.g., gantry rotation speed, spot spill time, etc.), the temporal dose distributions calculated for the radiation treatment plan could be used to determine a dose rates in Gy / s.

[0034] FIG. 6 illustrates an example dose distribution and linear energy transfer (LET) distribution for a proton FLASH arc therapy treatment plan in accordance with an embodiment. The dose distribution 602 and the LET distribution 606 shown in FIG. 6 are generated for an example radiation treatment plan based on an abdominal phantom. The target 604, 608 is also illustrated in the dose 602 and LET 606 distribution, respectively. In the example of FIG. 6, a prescription dose of 60 Gy was applied to the target 604, 608 (e.g., a GTV) of the abdominal phantom. The LET distribution generated using the disclosed PF AT technique (e.g., as described with respect to FIG. 2) shows a shift of greater LET values towards the center of the target (e.g., a GTV). This can result in a potentially enhanced biological effect within the target, as opposed to on the distal edge tracking of the radiation beams, where healthy tissue, or even OARs may be situated.

[0035] FIG. 7 illustrates an example dose distribution and linear transfer energy distribution for a proton FLASH arc therapy treatment plan in accordance with an embodiment. The dose distribution 702 and the LET distribution 706 shown in FIG. 7 are generated for an example radiation treatment plan based on a clinical brain case. The target 704, 708 is also illustrated in the dose 702 and LET 706 distribution, respectively. For the clinical brain case example, two non-coplanar arcs at couch angles of 0 and 90 degrees can be used, containing 8 and 4 beams, respectively. In the example of FIG. 7, a prescription dose of 45 Gy was applied to the target 704, 708 of the brain. The LET distribution generated using the disclosed PF AT technique (e.g., as described with respect to FIG. 2) shows a shift of greater LET values towards the center of the target. This can result in a potentially enhanced biological effect within the target, as opposed to on the distal edge tracking of the radiation beams, where healthy tissue, or even OARs may be situated.

[0036] Returning to FIG. 2, at block 216, the radiation treatment plan as determined at blocks 202-214 can be stored data storage (or memory) of the radiation treatment system 100 (e.g., database 114, server 116, or cloud 118 shown in FIG. 1). In some embodiments, the radiation treatment plan can be applied to a subject 120 during a treatment session using a radiation treatment system 100, for example, using the treatment console 108, delivery system 102,imaging system 104, and positioning system 106 of the radiation treatment system 100. The optimized dose delivery strategy of the radiation treatment plan determined using the process of FIG. 2 can advantageously constrain the dose distribution in healthy tissue in time, while the spread-out dose pattern within the target is maintined. This can enhance the possibility of achieving FLASH sparing in healthy tissue while minimizing any possibility of sparing effect within the target. The described PF AT technique of FIG. 2 can also shift regions of elevated LET away from the distal beam edge and towards the center of the target which can serve to amplify the biological impact within the target region and mitigate potential effects in adjacent healthy tissue. As mentioned, the described PF AT technique optimizes the arc plans (e.g., by optimizing the temporal spread of the dose delivery within the normal tissue) to achieve spatial fractionation of the dose to modulate the average dose rate at points outside the target to cause the average dose rate outside of the target (e.g., normal tissue or OARS) to tend towards the instantaneous dose rate of a single spot.

[0037] As mentioned, the arc selection process described above with respect to FIG. 2 can be performed using monoenergetic partial arcs within a single 360° gantry rotation. FIG. 3 illustrates a method for arc selection for a radiation treatment plan in accordance with an embodiment. The process illustrated in FIG. 3 is described as being carried out by the system illustrated in FIG. 1. However, in some examples, the process of FIG. 3 may be implemented by another system. Although the blocks of the process are illustrated in a particular order, in some embodiments, one or more blocks may be executed in a different order than illustrated in FIG. 3, or may be bypassed.

[0038] At block 302, water-equivalent depths (WEDs) of target voxels (e.g., target voxels based on the one or more images of a region of interest of a subject discussed above with respect to FIG. 2) for each beam angle (or a control point) can be calculated using, for example, a planning workstation 112 and treatment planning system. In some embodiments, the WED can be determined from the weighted sum of the thickness and relative density of the tissue layers in the regions of interest. In some embodiments, the WED can be determined using ray tracing. A predetermined beam angle (or control point) resolution can be, for example, 1° or 5° and the WED can be determined for each beam angle (or control point) within a 360° gantry rotation spaced with the predetermined beam angle resolution or spacing (e.g., 1°. 5° between each beam angle). At block 304, a selection region can be determined for each beam angle (or controlpoint). The selection region can define the acceptable target regions within which spots can be placed (e.g., as part of block 206 discussed above with respect to FIG. 2). In some embodiments, the selection region can be determined to ensure adequate target coverage while maintaining sufficient distance from the distal edge. In some embodiments, the selection region can be defined as a percentage of the WED from a list of the determined WEDs. For example, the selection region can be defined as 50-70% of the WED list, 50-80% of the WED list, etc.

[0039] At block 306, WED-wise angular maps can be generated for each WED determined at block 302 to represent, for every beam angle, points in the target that may be hit by a radiation beam with a range equal to that depth (i.e., the WED). FIG. 8 illustrates an example graph of a range of target water-equivalent depths (WEDs) for a plurality of beam angles in accordance with an embodiment. In FIG. 8. graph 800 illustrates the determined WEDs in the target (e.g., a GTV) for each beam angle (or control point). A selection region 802 (e.g., between 50-70% of the WED list in this example) is also shown that includes target WEDs for each angle.

[0040] Returning to FIG. 3, at block 308, a longest partial arc can be determined. In some embodiments, the longest partial arc can be determined by identifying the WED that results in a “hit” within the selection range of the highest number of consecutive beam angles (or control points). At block 310, the energy of the determined longest partial arc can be calculated from the WED. At block 312, the beam angles with hits can be assigned to the determined longest partial arc. At block 314, the determined longest partial arc and the beam angles assigned to the determined longest partial arc can be removed from the selection process.

[0041] At block 316, if all of the beam angles have not been assigned, the process returns to block 308 and the next longest partial arc is determined and beam angles assigned to the next longest partial arc in blocks 310-314. If at block 316 all of the beam angles (or control points) have been assigned, the results of the arc selection process (e.g., the set of partial arcs and the beam angles assigned to each partial arc) can be stored in data storage at block 318. In some embodiments, the results of the arc selection process can be stored in data storage (or memory) of the radiation treatment system 100 (e.g., database 114, server 116, or cloud 118 shown in FIG. 1). FIG. 9 illustrates and example graph of energy-arc combinations in accordance with an embodiment. In FIG. 9, the graph 900 shows an example set of selected partial arcs 902 for a radiation treatment plan.

[0042] As mentioned at block 212 of FIG. 2 above, the temporal spread of dose delivery within normal tissue voxels can be optimized. FIG. 4 illustrates a method for optimizing temporal spread of dose delivery for a radiation treatment plan in accordance with an embodiment. The process illustrated in FIG. 4 is described as being carried out by the system illustrated in FIG. 1. However, in some examples, the process of FIG. 4 may be implemented by another system. Although the blocks of the process are illustrated in a particular order, in some embodiments, one or more blocks may be executed in a different order than illustrated in FIG. 4, or may be bypassed.

[0043] At block 402, for each normal tissue voxel in the region of interest, the number of delivered spots between the first and last dose contributing spot can be minimized. As mentioned above, at block 210 of FIG. 2, voxels in a region of interest can be identified or flagged as normal (or healthy) tissue (e.g., within an external contour of the region of interest but outside of the target), or as within the target. In some embodiments, spots that contribute partial doses to normal tissue voxels that are primarily influenced by other spots can be removed from the radiation treatment plan. In some embodiments, spots placed at beam angles (or control points) forming boundaries between consecutive partial arcs may also be removed from the radiation treatment plan to prevent any overlap of dose in a given normal tissue voxel from multiple arcs, where the energy switching time required between the delivery of different arcs can have a significant lengthening effect on the temporal dose distribution in that voxel. In some embodiments, the process of block 402 can be performed using specific areas of interest instead of the full normal tissue region, for example, to minimize the temporal spread in one or more organs at risk.

[0044] At block 404, the remaining spot positions of the normal tissue voxels can be used to optimize the spot-wise monitor units to deliver a homogenous dose to the target, with predetermined target and organs at risk dose constraints. In some embodiments, the optimization of the spot-wise monitor units can be performed using a fast iterative shrinkage-thresholding (FISTA) algorithm. At bock 406, the optimized temporal spread of dose delivery within the normal tissue voxels can be stored in data storage (or memory) of the radiation treatment system 100 (e.g., database 114, server 116, or cloud 118 shown in FIG. 1, for example, as part of the radiation treatment plan.

[0045] As mentioned, a radiation treatment plan generated using the PF AT technique described above with respect to FIG. 2 can be applied to a subject during a treatment session using a radiation treatment system 100. FIG. 10 illustrates a method for delivering radiation therapy to a subject in accordance with an embodiment. The process illustrated in FIG. 10 is described as being carried out by the system illustrated in FIG. 1. However, in some examples, the process of FIG. 10 may be implemented by another system. Although the blocks of the process are illustrated in a particular order, in some embodiments, one or more blocks may be executed in a different order than illustrated in FIG. 10, or may be bypassed.

[0046] At block 1002, a radiation treatment plan for a region of interest of a subject including an optimized temporal spread for dose delivery within normal tissue only may be received, for example, a radiation treatment plan generated using the method described above with respect to FIG. 2. In some embodiments, the radiation treatment plan including an optimized temporal spread for dose delivery within normal tissue only can be retrieved from data storage (or memory) of a radiation treatment system (e.g., database 114, server 116, or cloud 118 of the radiation treatment system 100 shown in FIG. 1). At block 1004, a radiation treatment system (e g., radiation treatment system 200 shown in FIG. 1) can be controlled to deliver the radiation treatment plan. In some embodiments, a radiation source (e g., a radiation source of delivery system 102 shown in FIG. 1) can be used to emit radiation beams based on the radiation treatment plan. In some embodiments, the radiation treatment system used to deliver the radiation treatment plan can be configured to provide image guided radiotherapy (e.g., an imaging system 104 shown in FIG. 1) where images acquired during a treatment session can be used to guide the delivery of the radiation treatment plan. In some embodiments, the radiation treatment system used to deliver the radiation treatment plan can be configured to enable adaptive radiation therapy where radiation treatment plans can be modified based on, for example, the subjects daily anatomy. At block 1006, a report may be generated based on the delivery of the radiation treatment plan. For example, the report may indicate a status or completion of treatment field(s), a treatment progress, treatment interruption or errors, position of a delivery system (e.g., delivery system 102 shown in FIG. 1) and components therein, etc.

[0047] FIG. 11 is a block diagram of an example computer system in accordance with an embodiment. Computer system 1100 may be used to implement the systems and methods described herein. In some embodiments, the computer system 1100 may be a workstation, anotebook computer, a tablet device, a mobile device, a multimedia device, a network server, a mainframe, one or more controllers, one or more microcontrollers, or any other general-purpose or application-specific computing device. The computer system 1100 may operate autonomously or semi-autonomously, or may read executable software instructions from the memory or storage device 1116 or a computer-readable medium (e.g., a hard drive, a CD-ROM, flash memory), or may receive instructions via the input device 1120 from a user, or any other source logically connected to a computer or device, such as another networked computer or server. Thus, in some embodiments, the computer system 1100 can also include any suitable device for reading computer-readable storage media.

[0048] Data, such as data acquired with an imaging system (e.g., a magnetic resonance imaging (MRI) system) may be provided to the computer system 1100 from a data storage device 1116, and these data are received in a processing unit 1102. In some embodiment, the processing unit 1102 includes one or more processors. For example, the processing unit 1102 may include one or more of a digital signal processor (DSP) 1104, a microprocessor unit (MPU) 1106, and a graphics processing unit (GPU) 1108. The processing unit 1102 also includes a data acquisition unit 1110 that is configured to electronically receive data to be processed. The DSP 1104, MPU 1106, GPU 1108, and data acquisition unit 1110 are all coupled to a communication bus 1112. The communication bus 1112 may be, for example, a group of wires, or a hardware used for switching data between the peripherals or between any components in the processing unit 1102.

[0049] The processing unit 1102 may also include a communication port 1114 in electronic communication with other devices, which may include a storage device 1116, a display 1118, and one or more input devices 1120. Examples of an input device 1120 include, but are not limited to, a keyboard, a mouse, and a touch screen through which a user can provide an input. The storage device 1116 may be configured to store data, which may include data such as, for example, medical images of a subject (e.g., CT images), radiation treatment plans, etc. whether these data are provided to, or processed by, the processing unit 1102. The display 1118 may be used to display images and other information, such as magnetic resonance images, patient health data, and so on.

[0050] The processing unit 1102 can also be in electronic communication with a network 1122 to transmit and receive data and other information. The communication port 1114 can also be coupled to the processing unit 1102 through a switched central resource, for example thecommuni cation bus 1112. The processing unit can also include temporary storage 1124 and a display controller 1126. The temporary storage 1124 is configured to store temporary information. For example, the temporary storage 1124 can be a random access memory.

[0051] Computer-executable instructions for generating a radiation treatment plan for proton FLASH arc therapy (PF AT) according to the above-described methods may be stored on a form of computer readable media. Computer readable 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 readable media includes, but is 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 volatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired instructions and which may be accessed by a system (e.g., a computer), including by internet or other computer network form of access

[0052] The present technology has been described in terms of one or more preferred embodiments, and it should be appreciated that many equivalents, alternatives, variations, and modifications, aside from those expressly stated, are possible and within the scope of the invention.

Claims

CLAIMS1. A method for generating a radiation treatment plan for proton FLASH arc therapy(PF AT), the method comprising: receiving at least one image of the region of interest of the subject, wherein the region of interest includes a target; performing, using a processor, arc selection based on the at least one image to determine a set of arcs, wherein each arc in the set of arcs is associated with at least one beam angle from a predetermined set of beam angles and one or more radiation beams; identifying, using the processor, whether each voxel of the image in the region of interest is a normal tissue voxel or a voxel within the target; optimizing, using the processor, a temporal spread of dose delivery within the normal tissue voxels only; and storing, using the processor and a storage device, the radiation treatment plan including at least the arc selection and the optimized temporal spread of the dose delivery within the normal tissue voxels.

2. The method according to claim 1, further comprising placing, using a processor, a spot at each beam angle within the associated arc; and wherein optimizing a temporal spread of dose delivery within the normal tissue voxels only comprises minimizing, using the processor, a number of spots between a first dosecontributing spot and a last dose-contributing spot for each normal tissue voxel.

3. The method according to claim 1, further comprising: determining, using the processor, a dose distribution for the region of interest; and determining, using the processor, an linear energy transfer distribution for the region of interest.

4. The method according to claim 1, wherein performing arc selection based on the at least one image to determine a set of arcs comprises determining water-equivalent depths (WEDs) for voxels within the target for each beam angle in the predetermined set of beam angles.

5. The method according to claim 1, further comprising calculating a dose-influence matrix for each arc in the set of arcs.

6. The method according to claim 1, wherein each arc in the set of arcs is a monoenergetic partial arc.

7. The method according to claim 1, wherein an optimized temporal spread of dose delivery within the normal tissue voxels comprises multiple spatially separated radiation beams to be delivered individually at a point in time.

8. The method according to claim 1, wherein the target is a tumor.

9. A system for generating a radiation treatment plan for proton FLASH arc therapy(PF AT), the system comprising: a memory that stores one or more computer readable media that includes instructions; and one or more processor devices configured to execute the instructions of the computer readable media to: receive at least one image of the region of interest of the subject, wherein the region of interest includes a target; perform arc selection based on the at least one image to determine a set of arcs, wherein each arc in the set of arcs is associated with at least one beam angle from a predetermined set of beam angles and one or more radiation beams; identify whether each voxel of the image in the region of interest is a normal tissue voxel or a voxel within the target; optimize a temporal spread of dose delivery within the normal tissue voxels only; and store the radiation treatment plan including at least the arc selection and the optimized temporal spread of the dose delivery within the normal tissue voxels.

10. The system according to claim 9, wherein the one or more processor devices are configured to execute instructions of the computer readable media further to place a spot at each beam angle within the associated arc; and wherein optimizing a temporal spread of dose delivery within the normal tissue voxels only comprises minimizing, using the processor, a number of spots between a first dosecontributing spot and a last dose-contributing spot for each normal tissue voxel.

11. The system according to claim 9, wherein the one or more processor devices are configured to execute instructions of the computer readable media further to: determine a dose distribution for the region of interest; and determine a linear energy transfer distribution for the region of interest.

12. The system according to claim 9, wherein performing arc selection based on the at least one image to determine a set of arcs comprises determining water-equivalent depths (WEDs) for voxels within the target for each beam angle in the predetermined set of beam angles.

13. The system according to claim 9, wherein the one or more processor devices are configured to execute instructions of the computer readable media further to calculate a doseinfluence matrix for each arc in the set of arcs.

14. The system according to claim 9, wherein each arc in the set of arcs is a monoenergetic partial arc.

15. The system according to claim 9, wherein an optimized temporal spread of dose delivery within the normal tissue voxels comprises multiple spatially separated radiation beams to be delivered individually at a point in time.

16. The system according to claim 9, wherein the target is a tumor.

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