Methods and systems for modeling point placements for radiation therapy using crystalline materials

Abstract

The conventional crystal structure modeling method used to model crystalline materials to the atomic level is modified to determine point placement for radiation processing. The cross-sectional shape of the processing target is specified 202; the location (peak) in the density field inside the shape is determined using the crystal structure model 204; the location of points in the processing target is determined for point scanning 206, where the location corresponds to the location (peak) inside the shape determined using the crystal structure model; and the location of the points is stored as candidates to be potentially included in the radiation processing plan 208.

Description

Background Technology

[0001] The use of radiation therapy to treat cancer is well-known. Typically, radiation therapy involves directing beams of high-energy protons, photons, ions, or electrons to a target or volume within unhealthy tissue, such as a tumor or lesion.

[0002] Radiation treatment using proton beams offers significant advantages over other types of beams. The depth to which a proton beam reaches tissue depends on the beam's energy, and at this depth, most of its energy is released (delivering the majority of its dose). The region of the depth-dose curve where most of the energy is released is called the Bragg peak of the beam.

[0003] Before administering radiation treatment to a patient, a treatment plan is developed. This plan uses simulations and optimizations that can be based on past experience to define various aspects of the radiation treatment. Typically, the goal of the treatment plan is to deliver sufficient radiation to unhealthy tissue while minimizing the exposure of surrounding healthy tissue to that radiation.

[0004] One radiation therapy technique is called spot scanning, also known as pencil beam scanning. In spot scanning, a beam is directed to a point within the treatment target as specified in the treatment plan. For each energy level in the beam, the specified point locations are typically arranged in a fixed (grating) pattern, and the beam is delivered along a fixed scanning path within the energy level. By superimposing several beams of different energies at adjacent points, the Bragg peaks of the beams overlap to deliver a prescribed dose uniformly across the treatment target until the edge of the target, where the dose drops sharply to zero at or just beyond the edge.

[0005] Accurately calculating the number of points and their placement (location and distribution) is crucial. The goal is to determine the point placement to: 1) conform to the contour of the treatment target to improve the lateral penumbra and protect healthy tissue outside the treatment target from radiation beyond what is necessary to treat unhealthy tissue; and 2) be homogeneous within the treatment target to avoid dose variations (dose inhomogeneity) within the treatment target, ensuring that the prescribed dose is delivered to all parts of the target. Summary of the Invention

[0006] According to embodiments of the invention, methods not conventionally used for point placement are applied to formulate a radiation treatment plan for point scanning. In these embodiments, crystal structure modeling methods conventionally used to model crystalline materials to the atomic level are modified to determine point placement for radiation treatment. Crystal structure models include a range of models and methods, including but not limited to phase-field crystal (PFC) modeling and molecular dynamics.

[0007] For example, the PFC model describes periodic systems (such as atomic lattices) using smoothed classical density fields. The evolution of the PFC system model is governed by minimizing the free energy as a function of the density field. The formula and parameters of the free energy determine the lattice symmetry, elastic properties, and other characteristics of the periodic system.

[0008] In a PFC embodiment according to the invention, the solution to the problem of finding suitable point placement for point scanning is transformed into iterative relaxation of the density field, which yields a two-dimensional (2D) lattice with highly regular density peaks and conformal edges, which in turn defines the point location. More specifically, for example, in a PFC embodiment, information describing the treatment target in the patient (e.g., the size and cross-sectional shape of the target) is detailed; the location (peak) in the density field within the shape is determined using a crystal structure model; the location of the point in the treatment target for point scanning is determined, where the location corresponds to the location (peak) within the shape determined using the crystal structure model; and the point locations are stored as candidates, which can be included in the radiation treatment plan for the patient. A PFC-type model can also be solved in three dimensions to produce a body-centered cubic point pattern for uniform coverage within the treatment target.

[0009] Crystal structure modeling methods can generate point locations and distributions that conform to the contour of the target being treated and are uniform within the target. Therefore, during radiation treatment, surrounding healthy tissue is protected from damaging radiation, and dose variations within the target are avoided.

[0010] Typically, the use of crystal structure modeling methods can improve upon previous spot placement schemes. Crystal structure models (such as PFC-based models) produce edge-conformal spot placements for sharper lateral penumbra and better dose distribution, allowing spot placements to take into account distances from the edges of the treated target used for edge enhancement, and can produce highly regular spot placements aligned in fast scan directions that optimize (reduce) scan time. These benefits are particularly useful for FLASH radiotherapy, in which relatively high treatment radiation doses are delivered to the target in a single, short time period (e.g., at least 40 grays in less than one second, and dose rates of up to 120 grays or more per second).

[0011] Upon reading the following detailed description, those skilled in the art will recognize these and other objects and advantages according to embodiments of the invention, which are illustrated in the various accompanying drawings.

[0012] This summary is provided to introduce a series of concepts that will be further described in the following detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. Attached Figure Description

[0013] The accompanying drawings illustrate embodiments of the present disclosure and, together with the detailed description, serve to explain the principles of the disclosure. The drawings are incorporated in and form a part of this specification, and like reference numerals describe like elements. The drawings are not necessarily drawn to scale.

[0014] Figure 1 This is a block diagram of an example computer system on which the embodiments described herein can be implemented.

[0015] Figure 2 This is a flowchart illustrating an example of a computer-implemented operation for a radiation treatment plan using a crystal structure modeling method in an embodiment of the present invention.

[0016] Figure 3 An example is shown of the cross-sectional shape of a processing target that can be modeled using a crystal structure modeling method in an embodiment of the invention.

[0017] Figure 4 This is an example illustrating the position in the target shape determined using a crystal structure model in an embodiment according to the invention.

[0018] Figure 5 This is a flowchart illustrating an example of a computer-implemented operation for a radiation treatment plan using a crystal structure modeling method in an embodiment of the present invention.

[0019] Figure 6 This is an example illustrating a target shape having an internal crystalline state and an external constant state in crystal structure modeling according to an embodiment of the invention.

[0020] Figures 7A, 7B, and 7C illustrate an example of crystal structure modeling in an embodiment of the invention.

[0021] Figures 8A, 8B, and 8C illustrate another example of crystal structure modeling in an embodiment of the invention.

[0022] Figure 9 An example is illustrated where, in crystal structure modeling according to an embodiment of the invention, the spacing between density field peaks is a function of the distance from the edge of the target shape.

[0023] Figure 10 An example of a nonplanar energy layer of a target shape is illustrated in crystal structure modeling according to an embodiment of the invention.

[0024] Figure 11A and Figure 11B An example of multiple energy layers in a target shape in crystal structure modeling according to an embodiment of the invention is illustrated.

[0025] Figure 12 An example is illustrated where the target shape is subdivided into smaller shapes for crystal structure modeling in an embodiment of the invention. Detailed Implementation

[0026] Reference will now be made in detail to various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. While described in conjunction with these embodiments, it should be understood that they are not intended to limit the present disclosure to these embodiments. Rather, the present disclosure is intended to cover alternatives, modifications, and equivalents that may be included within the spirit and scope of the present disclosure as defined by the appended claims. Furthermore, numerous specific details are set forth in the following detailed description of the present disclosure to provide a thorough understanding of the disclosure. However, it should be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, processes, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.

[0027] Certain portions of the following detailed description are presented using other notations for procedures, logic blocks, processes, and operations on data bits within computer memory. These descriptions and representations are means by which those skilled in the art of data processing most effectively communicate the substance of their work to others skilled in the art. In this application, procedures, logic blocks, processes, etc., are considered as a consistent sequence of steps or instructions that lead to a desired result. These steps are steps involving the physical manipulation of physical quantities. Typically, although not essential, these quantities take the form of electrical or magnetic signals that can be stored, transmitted, combined, compared, and otherwise manipulated in a computer system. It is sometimes convenient to refer to these signals as transactions, bits, values, elements, symbols, characters, samples, pixels, etc., primarily for general reasons.

[0028] However, it should be remembered that all these and similar terms will be associated with appropriate physical quantities and are merely convenient notations applied to those quantities. Unless otherwise stated, as will be apparent from the following discussion, it should be understood that throughout this disclosure, discussions using terms such as “access,” “determine,” “describe,” “use,” “model,” “store,” “initialize,” “relax,” “place,” “fill,” “cover,” etc., refer to computer systems or similar electronic computing devices or processors (e.g., Figure 1 The actions and processes of the computer system 100 (e.g., Figure 2 and Figure 5 (Flowchart). A computer system or similar electronic computing device manipulates and converts data that is represented as physical (electronic) quantities within the computer system's memory, registers, or other such information storage, transmission, or display devices.

[0029] The following discussion may include terms such as “dose,” “dose rate,” and “energy.” Unless otherwise stated, a value is associated with each of these terms. For example, a dose has a value and can have different values. For simplicity, the term “dose” may refer to, for example, the value of a dose, unless otherwise stated or obvious from the discussion.

[0030] The following detailed description is presented and discussed according to the methods. Although the accompanying drawings describing the operation of these methods (e.g., Figure 2 and Figure 5 The steps and ordering are disclosed in the document, but these steps and ordering are merely examples. The embodiments are well-suited for performing various other steps or variations thereof listed in the flowcharts of the accompanying drawings in an order different from that depicted and described herein.

[0031] The embodiments described herein can be discussed in the general context of computer-executable instructions residing on some form of computer-readable storage medium (such as a program module) executed by one or more computers or other devices. By way of example and not limitation, the computer-readable storage medium may include non-transitory computer storage media and communication media. Typically, a program module includes routines, programs, objects, components, data structures, etc., that perform a particular task or implement a particular abstract data type. In various embodiments, the functionality of the program module may be combined or distributed as needed.

[0032] Computer storage media include volatile and non-volatile, removable and non-removable media implemented using any method or technology for storing information such as computer-readable instructions, data structures, program modules or other data. Computer storage media include, but are not limited to, random access memory, read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other memory technologies, optical disc ROM (CD-ROM), digital versatile disc (DVD) or other optical or magnetic storage devices, or any other medium that can be used to store desired information and can be accessed to retrieve that information.

[0033] Communication media can embody computer-executable instructions, data structures, and program modules, and includes any medium for transmitting information. By way of example and not limitation, communication media includes wired media such as wired networks or direct wired connections, and wireless media such as acoustic, radio frequency (RF), infrared, and other wireless media. Any combination of the foregoing may also be included within the scope of computer-readable media.

[0034] Figure 1A block diagram of an example computer system 100 on which the embodiments described herein can be implemented is shown. In its most basic configuration, system 100 includes at least one processing unit 102 and memory 104. This most basic configuration in Figure 1 The diagram is illustrated by dashed line 106. System 100 may also have additional features and / or functions. For example, system 100 may also include additional storage devices (removable and / or non-removable), including but not limited to disks, optical discs, or magnetic tapes. Such additional storage devices... Figure 1 The diagram is illustrated by removable storage device 108 and non-removable storage device 120. System 100 may also include communication connections(s)122, which allow devices to communicate with other devices, for example, in a networked environment using logical connections to one or more remote computers.

[0035] System 100 also includes multiple input devices 124, such as a keyboard, mouse, pen, voice input device, touch input device, etc. It also includes multiple output devices 126, such as display devices, speakers, printers, etc. The display device may be, for example, a cathode ray tube display, a light-emitting diode display, or a liquid crystal display.

[0036] exist Figure 1 In this example, memory 104 includes computer-readable instructions, data structures, program modules, etc., associated with the processing planning system (TPS) 150. However, the processing planning system 150 may alternatively reside in any of the computer storage media used by system 100, or may be distributed across some combination of computer storage media, or may be distributed across some combination of networked computers. The processing planning system 150 is used to evaluate and generate a final (prescribed) processing plan.

[0037] In radiation therapy techniques where the intensity of the particle beam is constant or modulated in the delivery field (such as intensity-modulated radiation therapy (IMRT) and intensity-modulated particle therapy (IMPT)), the beam intensity varies over each treatment region (volume within the treatment target) in the patient. Depending on the treatment modality, the degrees of freedom available for intensity modulation include, but are not limited to, beam shaping (collimation), beam weighting (spot scanning), the number of energy layers, and the angle of incidence (which may be referred to as beam geometry). These degrees of freedom result in an effectively infinite number of potential treatment plans, and therefore the ability to consistently and efficiently generate and evaluate high-quality treatment plans is beyond human capability and relies on the use of computer systems, especially considering the time constraints associated with diseases treated with radiation therapy (such as cancer) and the large number of patients undergoing or requiring radiation therapy during any given time period. For IMPT, steep dose gradients are typically used at the target boundaries and field edges to enhance dose consistency. This increases the complexity of the fluence map and reduces robustness to uncertainties.

[0038] Embodiments of the present invention improve the radiation treatment plan and the treatment itself. Compared to conventional techniques, the resulting treatment plan, as described herein, is superior for protecting healthy tissue from radiation by optimizing the balance between the dose rate delivered to the volume of unhealthy tissue (e.g., tumor) in the treatment target and the dose rate delivered to the surrounding healthy tissue. While treatment planning remains a complex task, it is an improvement over conventional treatment plans.

[0039] In summary, embodiments of this disclosure relate to the generation and implementation of treatment plans that are the most effective (relative to other plans) and have minimal (or most acceptable) side effects (e.g., lower dose rates outside the treated area). Therefore, embodiments of the invention specifically improve the field of radiation treatment planning and, in general, the field of radiation therapy. Embodiments of the invention allow for the faster generation of more effective treatment plans.

[0040] Embodiments of the present invention are not limited to radiation therapy techniques such as IMRT and IMPT.

[0041] The recommended radiation treatment plan is limited (e.g., using...) Figure 1 The proposed radiation treatment plan (150) is stored in and accessed from the computer system memory. The proposed radiation treatment plan includes parameter values ​​that may affect the dose and dose rate, as well as other parameters. Parameters that may affect the dose and dose rate include, but are not limited to, the number of irradiations of the volume in the target being treated, the duration of each irradiation (irradiation time), and the dose deposited in each irradiation. Parameters may also include the angle (direction) of the beam directed to the target being treated, and the beam energy of each beam. Parameters may also include the time period for which radiation is applied (e.g., multiple irradiations applied over a time period such as one hour, where each irradiation within a time period is separated from the next irradiation by another time period) and the time interval between each irradiation time period (e.g., each hour-long time period is separated from the next time period by one day). The volume of the target being treated can be divided into sub-volumes or voxels, in which case the parameter values ​​can be based on each sub-volume or each voxel (e.g., values ​​for each sub-volume or voxel).

[0042] A control system (not shown) implemented using a computer system (such as the computer system of 100) can be used to implement a prescribed radiation treatment plan. The control system can control parameters of the beam generation system, nozzles, and patient support equipment, including parameters such as beam energy, intensity, direction, size, and / or shape, based on the data it receives and in accordance with the prescribed radiation treatment plan.

[0043] During processing, in one exemplary embodiment, a particle beam enters a nozzle that includes one or more components that influence (e.g., reduce, modulate) the energy of the beam to control the dose delivered by the beam and / or control the relationship between the beam's depth and its depth profile, depending on the type of beam. For example, for a proton or ion beam with a Bragg peak, the nozzle can control the position of the Bragg peak within the target being processed. In other embodiments, energy modulation is performed outside the nozzle (e.g., upstream of the nozzle).

[0044] In an embodiment of the invention, the nozzle emits particles in a point-scanning beam (also known as a pencil beam). The nozzle is mounted on a movable gantry, allowing the beam to be delivered from different directions (angles) relative to the patient (the treatment target) on the patient support device, and also allowing the position of the patient support device relative to the beam to be changed. The target area is irradiated by the point-scanning beam using a raster scan. The increased flexibility gained through point scanning greatly improves the accuracy of the dose delivered to the treatment, maximizing the dose delivered to unhealthy tissues and minimizing damage to healthy tissues.

[0045] A beam can deliver a relatively high dose rate (a relatively high dose over a relatively short period of time). For example, a beam can deliver at least 40 grays (Gy) in less than one second and up to 120 Gy or more per second.

[0046] Modeling using crystalline materials for point placement in radiation therapy

[0047] Embodiments of the present invention provide an improved method for generating radiation treatment plans for radiation treatments (RTs) including FLASH RT. For FLASH RT, dose rates of at least 40 Gy per second and up to 120 Gy or more per second can be used.

[0048] The following discussion takes place within the framework of the phase-field crystal (PFC) model. However, embodiments of the invention are not limited thereto. Other types of models (such as, but not limited to, molecular dynamics) can be applied for use in determining point locations for point scans.

[0049] In summary, in embodiments according to the invention, the solution to the problem of finding suitable point placement for point scanning is transformed into iterative relaxation of the density field, which yields a two-dimensional (2D) lattice with highly regular density peaks and conformal edges, which in turn defines the point location for radiation therapy using point scanning. In the following discussion, the term "peak" is used when discussing the location in the treatment target within the crystal structure model, and the term "point" is used when discussing the location in the treatment target within the resulting treatment plan. However, since the location of a peak defines the location of a point, the two terms are practically synonymous in the following discussion.

[0050] Figure 2 and Figure 5 Flowcharts 200 and 500 are examples of computer-implemented methods for radiation processing planning using crystal structure models, respectively, in embodiments of the present invention. Flowcharts 200 and 500 can be implemented residing on some form of computer-readable storage medium (e.g., on...). Figure 1 Computer-executable instructions (e.g., in the memory of the computer system 100) Figure 1 Processing plan system 150).

[0051] Although Figure 2 and Figure 5 The operations in the flowchart are presented as occurring sequentially and in a specific order, but the invention is not limited thereto. These operations can be performed in different orders and / or in parallel, and they can also be performed iteratively. As mentioned above, due to the need to consider different parameters, the range of values ​​of these parameters, the interrelationships of these parameters, the need for a treatment plan that is effective for the patient and has the lowest risk to the patient, and the need to rapidly generate high-quality treatment plans, the use of computer system 100 ( Figure 1 It is important that the processing plan system 150 is consistently implemented on the radiation processing plan as disclosed herein.

[0052] exist Figure 2 In box 202, information describing the outline or shape and size of the cross section of the target being processed is accessed from the computer system memory.

[0053] Figure 3 The illustration shows an example of a cross-sectional shape 300 of a processing target that can be modeled using a crystal structure modeling method (e.g., a PFC model) in an embodiment of the invention. Shape 300 may have smooth or sharp (e.g., straight) edges, boundaries, and convex or concave corners. Generally, shape 300 is not limited.

[0054] exist Figure 2 In box 204, the location inside the shape is determined using a crystal structure model.

[0055] Figure 4 This is an example illustrating a position (illustrated by position 402) in shape 300 determined using a crystal structure model in an embodiment according to the invention. Figure 5 Additional information was provided in the discussion.

[0056] Crystal structure models such as the PFC model describe the use of smooth classical density fields. Periodic systems such as atomic lattices. The evolution of PFC systems is determined by free energy. Minimization control. The formula and parameters of free energy determine the lattice symmetry, elastic properties, and other characteristics of a periodic system. Free energy is given by the following equation (1):

[0057]

[0058] In equation (1), the two first terms generate the so-called double-well potential, and the third term generates the periodic density field. And Hookean elasticity. Equation (1) represents a formula for free energy; however, the invention is not limited thereto, and other formulas are possible and can be used alternatively. In 2D, this model can produce close-packed (e.g., hexagonal) structures or patterns.

[0059] For example, rectangular and linear structures or patterns are also possible with almost no increase in computational cost. Such structures can be constructed by using equation (1) with... replace To achieve this, in which and It is the weight, and It is a relative length scale (e.g., for rectangular lattices). The computational cost is actually the same because the above substitutions can be incorporated into pre-computed operators that may not require updates.

[0060] The crystal structure model can also be extended to three dimensions (3D). This model can be solved in 3D to produce body-centered cubic point patterns for more uniform coverage. Other structures are also possible using, for example, the substitutions described above. Face-centered cubic and hexagonal close packing also produce more uniform packing.

[0061] Calculations using the crystal structure model begin with an analysis of the density field. The initial estimate is then obtained, and the model iteratively balances the density field. And the free energy F is minimized using dissipative dynamics (such as gradient descent), which is given by the following equation (2):

[0062]

[0063] Equation (2) can be solved efficiently and accurately using a semi-implicit spectral method. Equation (2) is an example of dissipation dynamics; however, there are other dissipation dynamics that can be used alternatively, and therefore the invention is not limited thereto.

[0064] In an embodiment of the invention, point location calculation is converted into 2D calculation, wherein a relaxed density field The peak value is equal to the point position within the energy layer of the beam used for point scanning. Chemical potential term. ,in (For example, a spatially variable field), is added to the free energy. Use constant values ​​within the target. , generating a periodic density field That is, to generate peaks (and corresponding points). Different constant values ​​are given outside the target. This results in a constant density field. (For example, there is no peak, and therefore no point). The region within the target can be expanded at the expense of the region outside the target to obtain a peak (and corresponding point) at an optimal distance from the target boundary (edge). The dissipation dynamics are now given by the following equation (3):

[0065]

[0066] Equation (3) is an example of dissipation dynamics; however, there are other dissipation dynamics that can be used alternatively, and therefore the invention is not limited thereto.

[0067] exist Figure 2 In box 206, the point positions in the processed target for point scanning with a radiation beam are determined based on the results of box 204. Specifically, the positions of the points used for point scanning correspond to the positions of peaks determined using a crystal structure model (e.g., Figure 4 (Position 402).

[0068] In box 208, the locations of the points used for point scanning (from box 206) can be included in the radiation treatment plan.

[0069] Now for reference Figure 5 In box 502, the cross section of the target being processed is modeled using a density field model with a crystal structure (e.g., PFC) that has a crystalline state inside the shape and a constant state outside the shape.

[0070] Figure 6 This is an example illustrating shape 300 having an internal crystalline state and an external constant state in an embodiment according to the invention.

[0071] exist Figure 5 In box 504, the density field is initialized. The initial state of the density field can be, for example, a constant state, a perfect crystal state, or a mixture of constant and perfect crystal states. Additional information is provided in the discussion of Figures 7A and 8A.

[0072] exist Figure 5In box 506, the density field is relaxed to determine the final set of peaks in the density field. During relaxation, dissipative dynamics (such as equation (3) above) are used to minimize the free energy of the density field. As the density field is relaxed, it is allowed to evolve until it reaches equilibrium at the minimum of the free energy (the state where it no longer changes from one iteration to the next). During relaxation, the peaks in the density field can move, grow, or bend. The final set of peaks is the set of peaks at the minimum of the free energy. Additional information is provided in the discussion of Figures 7B, 7C, 8A, and 8B.

[0073] exist Figure 5 In box 508, the final set of peaks (from box 506) can be used as candidates for point locations in the radiation treatment plan.

[0074] Figures 7A, 7B, and 7C illustrate an example of initial crystal structure modeling with a constant state according to an embodiment of the present invention. In the constant state, the density field... Initially constant, and the value at the boundary of the target shape 300. The discontinuity in (Equation (3)) leads to the density field that was initially constant. Conformal peaks form nucleation at the edges. Figure 7A shows the density field after several iterations. As the density field is relaxed, the lattice of peaks propagates inward from the boundary of the target shape 300 through the nucleation of more peaks until the shape shown in Figures 7B and 7C is filled.

[0075] Figures 8A, 8B, and 8C illustrate an example of crystal structure modeling with initialization in a perfect crystal state according to an embodiment of the invention. In the perfect crystal initial state, the shape 300 of the target being processed is filled with an initial set of (patterned) peaks (e.g., as a hexagonal lattice) that can extend beyond the boundary of the target shape as shown in Figure 8A. In the example of Figure 8A, the hexagonal lattice of peaks (the sum of three plane waves from a 120-degree angle) is used as the initial state. When the density field is relaxed, the peaks outside the target shape 300 disappear, and the peaks inside the shape rearrange to conform to the boundary of the shape as shown in Figures 8B and 8C.

[0076] In the initial mixed state, the crystal structure model begins with a constant density field. As in the constant initial state (Fig. 7A), but after a brief relaxation (before the peaks propagate and fill the target shape 300), the interior of the target shape is covered by, for example, a hexagonal lattice as in the initial state of a perfect crystal (Fig. 8A). The entire interior of shape 300 is not covered; for example, the peaks at the edges of the target shape 300 are not covered. Then, calculations are performed using the model until the interior of the target shape is filled, as described above with respect to Figs. 8B and 8C.

[0077] In other words, in the initial state of mixing, the distribution of the initial set of peaks is obtained from the nucleation of the peaks and diffuses inward at the boundary of the shape 300 of the target being processed. The density field is relaxed to generate an additional set of peaks at a location inside the target shape. At least a subset of the additional set of peaks is covered by the distribution of different peaks, and then relaxation continues to determine the final set of peaks that fills the target shape.

[0078] Mixing initial states can produce peak (and point) placements that are more uniform within the target and better conform to the target shape boundaries.

[0079] The initial state can also be selected based on or taking into account the scanning direction. Scanning the beam in the main scanning direction of the beam delivery system (e.g., the nozzle) is typically significantly faster. This main direction is referred to as the fast scanning direction. Therefore, the orientation of the initial peaks in the perfect crystal and mixed initial state can be selected such that the peaks are aligned with, for example, the rows of the fast scanning direction. To align the lattice of the points with the fast scanning direction, the density field can be initialized based on the desired alignment. An alternative is to introduce the following terms into the free energy term in equation (1). In this example, the following terms tend to be periodic in the x-direction:

[0080]

[0081] Alignment of the peak (and therefore the point used for scanning) with the rapid scanning direction reduces scanning time during radiation treatment, which simplifies the management of patient movement during treatment and leads to better treatment outcomes.

[0082] The point placements obtained using initialization from a constant state (Figs. 7A-7C) and relaxation of the density field in the crystal structure (Figs. 8A-8C) can be subdivided into smaller clusters to optimize the scan pattern for improving the dose rate in critical regions where the field projection overlaps with the projection of organs in hazardous structures (see below for example). Figure 12 (Discussion).

[0083] Figure 9 An example is illustrated where, in an embodiment according to the invention, the spacing of the density field peaks (and the resulting points) is a function of the distance from the edge of the target shape 900. In this example, the peak (point) spacing decreases as the distance from the boundary of the target shape 900 increases. This is achieved by using equation (1) with... ( )replace This allows the spacing to depend on the distance from the target boundary. Here, This is a distance map. Increased spacing at the boundaries of the target shape promotes edge enhancement.

[0084] Figure 9 The example illustration shows a planar energy layer with a target shape of 90°. However, the energy layer may not be planar on the target shape. Figure 10 An example of a nonplanar energy layer in a target shape 1000 according to an embodiment of the invention is illustrated. In the embodiment, finite element code can be used to determine peaks (and points) on a curved surface, such as a curved energy layer.

[0085] Figure 9 and Figure 10 The example illustration shows a single energy layer. Figure 11A and Figure 11B An example of multiple energy layers 1101, 1102, and 1103 in a target shape 1100 according to an embodiment of the invention is illustrated. Three energy layers are shown, but the invention is not limited thereto. Note that... Figure 11A and Figure 11B Energy layers are shown, not physical layers. For example, energy layers 1101 and 1102 could be in the same physical layer, where the physical layer receives two beams of radiation during processing, each with a different energy. In other examples, energy layers 1101 and 1102 could be in different physical layers corresponding to different Bragg peak depths.

[0086] exist Figure 11A In the example, peaks (and the resulting points) are coupled between layers. That is, for example, the placement and position of peaks in energy layer 1101 take into account (e.g., based on) the placement and position of peaks in energy layer 1102. In other words, peaks are coupled between energy layers. The coupling of peaks between energy layers allows peaks (and corresponding points) to be staggered with adjacent energy layers for more uniform 3D coverage within the target. Figure 11A In the example, the peak in one layer is shifted relative to the peak in the adjacent layer, which also improves the uniformity of coverage and dose distribution on the treated target during radiation treatment. Peaks in adjacent layers can be coupled by introducing the following term into the free energy term in equation (1), where Corresponding to the density field used for adjacent energy layers:

[0087]

[0088] exist Figure 11B In the example, the peaks in layers 1101-1103 can be coupled, but not necessarily. That is, because the peaks in energy layers 1101-1103 are aligned in this example, the peak distribution in any one energy layer can be determined independently of the peak distribution in adjacent energy layers.

[0089] Figure 12An example according to an embodiment of the invention is illustrated, wherein the processing target 1200 is subdivided into smaller target shapes (e.g., four smaller shapes 1201, 1202, 1203, and 1204), and the method described above is used to determine the locations of peaks (and points) with edge enhancement for each smaller target shape for a given energy layer. By optimizing the point distribution in each smaller shape 1201-1204, this method can reduce the total time required for raster scanning to process the target 1200.

[0090] Such as Figure 12 Those point clusters in can be represented in equation (1) Replace with To achieve this, in which It is a spatial field indicating the change in distance between adjacent points. It was chosen to make it uniform within the cluster and to vary at the cluster boundaries to produce a larger point spacing there.

[0091] In summary, crystal structure modeling methods (e.g., PFC) can generate point locations and distributions that conform to the contour of the target being treated and are uniform within it. Therefore, during radiation treatment, surrounding healthy tissue is protected from damaging radiation, and dose variations within the target are avoided.

[0092] Crystal structure models (such as PFC-based models) can produce edge-conformal point placements for sharper lateral penumbra and better dose distribution. They allow for point placements that consider the distance from the edge of the treatment target used for edge enhancement and can produce highly regular point placements aligned in fast scanning directions, thereby optimizing (reducing) scan time. This is particularly useful for FLASH radiotherapy, where a relatively high treatment dose is delivered to the target in a single, short time period. Furthermore, PFC-based crystal structure models do not require fixing the outermost points (those closest to the target boundary) in their positions; instead, their arrangement can be optimized. Additionally, PFC-based crystal structure models do not require a fixed number of peaks / points; instead, peaks (and corresponding points) nucleate and vanish freely without any constraint, providing greater freedom and flexibility in optimizing the number and distribution of points.

[0093] Typically, the use of crystal structure modeling methods can improve upon previous point placement schemes.

[0094] Embodiments of the present invention improve radiation treatment planning and the treatment itself. Treatment plans, as described herein, are superior for protecting normal tissue from radiation, by reducing (if not minimizing) the dose to normal tissue (outside the target) by design (and, in some cases, by integration). When used with FLASH dose rates, patient movement management is simplified because the dose is applied over a short time (e.g., less than one second). Treatment planning, while still a complex task of finding a balance between competing and relevant parameters, is simplified relative to conventional planning. The techniques described herein can be used in stereotactic radiosurgery as well as stereotactic body radiotherapy with single or multiple metastases.

[0095] Embodiments of the present invention are not limited to radiation therapy techniques such as IMRT and IMPT.

[0096] Although the subject matter has been described in language specifically used for structural features and / or methodological actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as exemplary forms of implementing the claims.

Claims

1. A computer system, comprising: processor; as well as A memory, coupled to the processor and including instructions, which, when executed, cause the processor to perform a method for planning a radiation process, the method comprising: Access information from the memory, the information describing the shape of the processing target; The location inside the shape is determined using a crystal structure model, wherein the crystal structure model is selected from the group consisting of: phase-field crystal modeling and molecular dynamics; The positions of points in the processing target are determined for point scanning with a radiation beam, wherein the positions of the points correspond to positions within the shape determined using the crystal structure model; and The location of the point in the storage radiation treatment plan.

2. The computer system according to claim 1, wherein determining the position inside the shape of the processing target and determining the position of the point in the processing target comprises: The crystal structure model is used to model the shape of the processing target using a density field, the density field having a crystalline state inside the shape and a constant state outside the shape; Initialize the density field; Relax the density field to determine the final set of peaks in the density field; The final set of peak values ​​is used as a candidate for the location of the point in the radiation treatment plan.

3. The computer system of claim 2, wherein the initialization includes using an initial constant density field.

4. The computer system of claim 2, wherein the initialization comprises filling the shape with a distribution of an initial set of peaks at locations in the density field.

5. The computer system according to claim 2, 3 or 4, wherein the relaxation includes: The initial constant density field is relaxed to generate an additional set of peaks at locations inside the boundary of the shape. Rewrite at least a subset of the additional set of peaks using the distribution of different peak values; as well as Following the rewrite, the relaxation continues to determine the final set of peaks.

6. The computer system according to any one of claims 2, 3, or 4, wherein determining the location inside the shape comprises: The location inside the shape is determined by considering the planned scan direction of the point scan.

7. The computer system according to any one of claims 2, 3, or 4, wherein the radiation beam comprises a plurality of energy layers, and wherein determining the location within the shape comprises: Considering the location within the shape determined for other energy layers, determine the location within the shape for each of the energy layers.

8. The computer system according to any one of claims 2, 3, or 4, wherein determining the location within the shape comprises: The location inside the shape is determined by considering the distance from the boundary of the shape.

9. A non-transitory computer-readable storage medium having computer-executable instructions, the computer-executable instructions being used to cause a computer system to perform a method for planned radiation treatment, the method comprising: Access information from the computer system's memory, the information describing the shape of the processing target; The location inside the shape is determined using a crystal structure model, wherein the crystal structure model is selected from the group consisting of: phase-field crystal modeling and molecular dynamics; The positions of points in the processing target are determined for point scanning with a radiation beam, wherein the positions of the points correspond to the positions within the shape determined using the crystal structure model; as well as The location of the point in the radiation treatment plan is stored in the memory of the computer system.

10. The non-transitory computer-readable storage medium of claim 9, wherein determining the location within the shape of the processing target and determining the location of the point in the processing target comprises: The crystal structure model is used to model the shape of the processing target using a density field, the density field having a crystalline state inside the shape and a constant state outside the shape; Initialize the density field; Relax the density field to determine the final set of peaks in the density field; The final set of peak values ​​is used as a candidate for the location of the point in the radiation treatment plan.

11. The non-transitory computer-readable storage medium of claim 10, wherein the initialization includes using an initial constant density field.

12. The non-transitory computer-readable storage medium of claim 10, wherein the initialization comprises filling the shape with a distribution of an initial set of peaks at locations in the density field.

13. The non-transitory computer-readable storage medium according to claim 10, 11, or 12, wherein the relaxation comprises: The initial constant density field is relaxed to generate an additional set of peaks at locations inside the said positions at the boundaries of the shape; Rewrite at least a subset of the additional set of peaks using the distribution of different peak values; as well as Following the rewrite, the relaxation continues to determine the final set of peaks.

14. The non-transitory computer-readable storage medium according to any one of claims 10, 11, or 12, wherein determining the location within the shape comprises: The location inside the shape is determined by considering the planned scan direction of the point scan.

15. The non-transitory computer-readable storage medium according to any one of claims 10, 11, or 12, wherein the radiation beam comprises a plurality of energy layers, and wherein determining the location within the shape comprises: Considering the location within the shape determined for other energy layers, determine the location within the shape for each of the energy layers.

16. The non-transitory computer-readable storage medium according to any one of claims 10, 11, or 12, wherein determining the location within the shape comprises: The location inside the shape is determined by considering the distance from the boundary of the shape.

17. A computer-implemented method for a radiation treatment program, the method comprising: Access information from memory, the information describing the shape of the target being processed; The location inside the shape is determined using a crystal structure model, wherein the crystal structure model is selected from the group consisting of: phase-field crystal modeling and molecular dynamics; The positions of points in the processing target are determined for point scanning with a radiation beam, wherein the positions of the points correspond to the positions within the shape determined using the crystal structure model; as well as The location of the point in the storage radiation treatment plan.

18. The computer-implemented method of claim 17, wherein determining the position inside the shape of the processing target and determining the position of the point in the processing target comprises: The crystal structure model is used to model the shape of the processing target using a density field, the density field having a crystalline state inside the shape and a constant state outside the shape; Initialize the density field; Relax the density field to determine the final set of peaks in the density field; The final set of peak values ​​is used as a candidate for the location of the point in the radiation treatment plan.

19. The computer-implemented method of claim 18, wherein the initialization includes using an initial constant density field.

20. The computer-implemented method of claim 18, wherein the initialization comprises filling the shape with a distribution of an initial set of peaks at locations in the density field.

21. The computer-implemented method according to claim 18, 19, or 20, wherein the relaxation comprises: The initial constant density field is relaxed to generate an additional set of peaks at locations inside the boundary of the shape. Rewrite at least a subset of the additional set of peaks using the distribution of different peak values; as well as Following the rewrite, the relaxation continues to determine the final set of peaks.

22. The computer-implemented method according to any one of claims 18, 19, or 20, wherein determining the position inside the shape comprises: The planned scanning direction of the point scan is taken into account to determine the location inside the shape.

23. The computer-implemented method according to any one of claims 18, 19, or 20, wherein the radiation beam comprises a plurality of energy layers, and wherein determining the location within the shape comprises: The location inside the shape is determined for each of the energy layers, taking into account the location inside the shape determined for other energy layers.

24. The computer-implemented method according to any one of claims 18, 19, or 20, wherein determining the location within the shape comprises: The location inside the shape is determined by considering the distance from the boundary of the shape.

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