Method for generating a radiation therapy treatment plan, computer program and computer system for generating a radiation therapy treatment plan, and radiation therapy delivery system

Abstract

A method for optimizing a radiotherapy treatment plan for delivering charged particles to a patient via pencil beam scanning involves optimizing the treatment plan using an optimization problem designed to allow the spot to vary in at least one of shape and orientation, and optionally size. This allows the spot to be optimized to cover the target in the best possible manner and with a well-defined penumbra along the outer edges of the target. The present invention also relates to a computer program product and computer system for such planning, and a treatment delivery system for delivering such a plan.

Description

Technical Field

[0001] The present invention relates to the planning and delivery of ion-based radiotherapy treatments. Background Art

[0002] Ion-based radiotherapy involves the use of charged particles (such as protons), or ions (such as helium or carbon ions). The overall goal is to deliver a dose to the target volume while minimizing unwanted doses to nearby critical organs and healthy tissues. In particular, the present invention relates to charged particle therapy using a scanning focused ion beam known as pencil beam scanning (PBS). In PBS, different beams are aimed at the patient with several discrete or quasi-discrete spots or by line scanning. Several spots are delivered at each of several different energy levels so as to cover the target in three dimensions while providing as little dose as possible outside the target.

[0003] The region near the edge of the beam where the dose rate drops to a low value is called the penumbra. It is desirable to keep the penumbra as narrow as possible.

[0004] Near the boundaries of the target, dose reduction should be as high as possible towards the edges to ensure adequate dose across the entire target while sparing as much surrounding tissue as possible. Dose reduction is determined by the lateral shape and size of the spot, with larger reductions for smaller spots. Therefore, current clinical practice when designing spots is to make them small and, traditionally, as round as technically feasible given the beam delivery system. Traditionally, proton therapy dose planning aims for consistently round spots of the same size. This is typically achieved by adjusting the beam using focusing elements upstream of the patient.

[0005] Various attempts have been made to further improve the dose distribution near the edge of the target. These attempts generally involve the use of different types of static, field-specific apertures. Such apertures must be manufactured specifically for each patient, which is expensive and impractical. It is also possible to use dynamically adjustable collimation devices, such as multi-leaf collimators (MLCs), although this is less common in PBS systems. MLCs are also expensive. Apertures also increase the generation of neutron background dose during treatment, which is problematic. Any type of aperture will only affect the spot at the edge of the treatment field. Summary of the Invention

[0006] It is an object of the present invention to enable the generation and delivery of particle-based radiotherapy with improved target coverage and in particular improved properties near the target edges.

[0007] The present invention relates to a computer-based method for generating a radiotherapy treatment plan for delivering charged particles to a patient by pencil beam scanning, the particles being delivered in a spot, the method involving optimizing the treatment plan using an optimization problem designed to allow the spot to vary in at least one of shape and orientation.

[0008] Thus, according to the present invention, the shape and / or orientation of the spot can be varied for a particular beam energy to create spots that together will cover the target cross section for that energy while achieving a reduced penumbra. This can be done per individual spot, per energy layer, or per beam. An alternative organization for spot deformation is to repeat energy layers or beams, wherein the spot of each energy layer (or each beam) has a different shape and / or orientation. This can be provided within an energy layer or beam. In a preferred embodiment, the spot shape is allowed to be circular or elliptical. In other embodiments, the spot shape may be allowed to vary more, including, for example, a triangular or rectangular spot, or a spot of any suitable geometry. It should be understood that due to technical limitations, the shape may not be geometrically perfect. For example, a circular spot may not be a perfect circle. In this document, the term "circular" means as close to a circle as possible when the delivery system is capable of generating it. The size of the spot may also be varied to achieve greater flexibility.

[0009] One or more predefined values ​​or combinations of values ​​for shape and / or orientation can be allowed. Limiting the number of possible combinations makes delivery easier and faster. Alternatively, the shape and / or orientation can be allowed to vary freely for maximum flexibility. This allows the spot to be positioned and oriented to cover the target in the best possible way. It also allows for positioning the edge of the spot with the best defined boundaries so that it is aligned and oriented relative to the target boundary, creating the sharpest reduction at the target boundary.

[0010] The optimization problem can be designed to allow the light spot to vary in at least one part of the target while keeping it consistent in at least another part. This allows for maximum flexibility in feasible areas, while allowing for simpler planning of other areas. For example, it might be advantageous to vary the light spot near the outer edge of the target, while keeping the light spot away from the edge consistent, such as a uniform circular shape. This allows for coverage that adapts to the actual shape of the target and more quickly delivers a light spot in the center of the target, as well as a clear penumbra at the outer edges of the target.

[0011] One effective way to achieve different spot shapes and / or orientations is with the aid of an aperture system, such as a collimator, that is arranged to adjust the spot flux. Alternatively, the spot can be shaped using an electromagnetic optical focusing system. In the latter case, there is no collimator-generated neutron dose, which is particularly advantageous for pediatric applications.

[0012] A combination of an aperture device and an electromagnetic focusing system may also be used. For this purpose, the plan generated by the method should include how the aperture device is to be controlled.

[0013] The greatest flexibility is achieved if spot shaping is done for each individual spot at each energy level. Each spot can then be stretched to an optimal form, typically an ellipse, and positioned and oriented in the best possible way based on the curvature of the eye's view projection of the target beam. Typically, the spot in the center of the target will remain circular, as spots near the edges will affect the penumbra surrounding the target.

[0014] Alternatively, a limited number of spot shapes may be allowed, such as one circular spot shape and two elliptical spot shapes with perpendicular major axes. It would also be possible to have one circular spot shape and several predefined elliptical spot shapes and sizes with predefined major axes. These embodiments may support simpler planning and / or simplified and faster delivery compared to embodiments that allow the shape, size, and / or orientation of the spot to vary freely.

[0015] Each type of spot can also be collected in a separate energy layer so that for example for one nominal energy there may be one layer with an elliptical spot of a first orientation, one layer with an elliptical spot of a second orientation, and one layer with a circular spot.

[0016] The optimization problem can also be formulated to define the order in which the spots are delivered, taking the delivery time into account.

[0017] The invention also relates to a computer program product comprising computer readable code means which, when run in a processor of a computer, causes the processor to perform a method according to any one of the preceding claims. The computer program product may comprise non-transitory storage means storing the computer readable code means.

[0018] The invention also relates to a computer system comprising a processor, a data memory and a program memory arranged to store a computer program in such a way that it can be executed in the processor, the program memory comprising a computer program product according to above.

[0019] The present invention also relates to a radiotherapy treatment delivery system for delivering charged particles to a patient via a PBS, wherein the particles are delivered in a spot, the system comprising a processor for controlling treatment delivery, the system further comprising a changing device for changing at least one of the shape and orientation of the spot during delivery, and the processor being arranged to control the changing. The changing device may comprise an electromagnetic optical system and / or a controllable aperture device, the electromagnetic optical system and / or the controllable aperture device being arranged to change the shape and / or orientation of the spot during delivery as discussed above. The system may also be arranged to organize the spot for the most effective delivery.

[0020] The radiotherapy treatment delivery system according to any of the claims may further comprise a memory storing a treatment plan, and the processor being arranged to control the delivery system according to the treatment plan, wherein the treatment plan has been generated using the method according to any embodiment disclosed in this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be described in more detail below by way of examples and with reference to the accompanying drawings.

[0022] Figure 1 The light spot distribution according to the embodiment of the present invention is schematically illustrated.

[0023] Figure 2 is a flow chart of a treatment planning method according to the present invention.

[0024] Figure 3 A computer system is disclosed that can implement the treatment planning method of the present invention.

[0025] Figure 4 A treatment delivery system for delivering a treatment plan according to the present invention is disclosed. DETAILED DESCRIPTION

[0026] Figure 1 The beam diagram schematically illustrates an energy layer in a target 1 according to an embodiment of the present invention, which is covered by light spots 3 and 5. As can be seen, at a central location away from the target boundary, substantially circular light spots 3 are present, positioned adjacent to each other so that they cover the central region of the target. Near the target boundary, the light spots 5 are elliptical, with each light spot 5 shaped to cover the region between the circular spot and the target boundary. The light spots 3 and 5 can be generated by any form of pencil beam scanning, including discrete scanning, quasi-discrete scanning, line scanning, or by any other suitable method.

[0027] exist Figure 1In the scenario shown in FIG, the shape and orientation of the light spots 3 and 5 are allowed to vary freely. As mentioned above, the plan can be set to allow only a limited set of shapes, sizes, and / or orientations. For example, two elliptical shapes with their major axes perpendicular to each other can be allowed, or four elliptical shapes with their major axes at 45 degrees to each other can be allowed. The shape and / or orientation can be allowed to vary. The size of the light spots can also vary. For example, all light spots may have the same size, but different shapes and / or orientations may be allowed, or the size may be allowed to adapt to a portion of the target, such as between another light spot and the boundary of the target.

[0028] Figure 2 The diagram illustrates a master planning method according to the present invention. In a first step S21, an optimization problem is defined. The optimization problem can be defined in any suitable manner, but is configured to allow the light spot to change in at least one of shape, size, or orientation. In a second step S22, optimization is performed using the optimization problem defined in step S21. In a third optional step S23, the energy layers included in the preferred plan are organized so that delivery is as efficient as possible. For example, all light spots with the same characteristics in shape, size, and orientation are delivered continuously so that the change in the light spot shape only needs to occur once for each set of characteristics. Alternatively, light spots with the same set of characteristics can be grouped together in energy layers so that there is one energy layer for each light spot type. This organization of the light spots can alternatively be performed in the delivery system.

[0029] The optimization problem can also be set up so that the light spot is only allowed to change in one or more parts of the target, while the light spot in the remaining one or more parts remains the same. Typically, this means that the boundary light spot (i.e., the light spot near the boundary of the target) will be allowed to change to be as close as possible to the outline of the target, while the light spot inside these boundary light spots will remain the same, for example, circular and the same size.

[0030] Figure 3 is a schematic diagram of a computer system that can perform the treatment planning method of the present invention. Computer 31 includes a processor 33, a data memory 34, and a program memory 36. Preferably, there are also one or more user input devices 38, 39 in the form of a keyboard, mouse, joystick, voice recognition device, or any other available user input device. The user input device may also be arranged to receive data from an external memory unit.

[0031] The data memory 34 comprises the necessary data for carrying out the method, such as the desired dose distribution and the segmented patient image. The program memory 36 stores a computer program arranged to cause the computer to carry out the method steps according to some embodiments of the present invention, such as Figure 2 As shown in .

[0032] As will be understood, data memory 34 and program memory 36 are shown and discussed schematically. There may be several data memory units, each storing one or more different types of data, or one data memory unit storing all data in a suitably structured manner, and the same for the program memory. Both programs and data may be found in one or more memories within the computer system or in another unit accessible from the computer system.

[0033] Figure 4 is an overview of a system 60 for radiation therapy treatment and / or treatment planning. As will be appreciated, such a system may be designed in any suitable manner, and Figure 4 The design shown is merely an example. A patient 61 is positioned on a treatment couch 63. The system includes an imaging / therapy unit having a radiation source 65 mounted in a gantry 67 for emitting radiation to the patient positioned on the couch 63. Typically, the couch 63 and gantry 67 can be moved relative to each other in several dimensions to provide the most flexible and precise radiation delivery to the patient. These components and their functions are well known to those skilled in the art.

[0034] There are typically several passive devices provided to shape the beam laterally and in depth, and these will not be discussed in greater detail here. The apparatus is arranged to provide radiation in the form of a pencil beam. In this example, the system further comprises means for modifying the magnetic field and means for modifying the magnetic field, the means for modifying the magnetic field being used to influence the beam, for example by generating a magnetic field or an electric field or a combined magnetic field / electric field that will influence the particle path of the beam in the beamline.

[0035] The changing device 89 is arranged to change at least one of the shape and orientation of the light spot and optionally the size of the light spot during delivery. In a preferred embodiment, the changing device comprises an electromagnetic optical system arranged to change the path of the charged particles to create different light spots. Alternatively, or in addition to the electromagnetic system, the changing device may comprise an aperture shaping device in the form of a collimator or block, arranged to change the shape and / or orientation of the light spot during delivery.

[0036] The computer 71 comprises a processor 73, a data memory 74 and a program memory 76. Preferably, there are also one or more user input devices 78, 79 in the form of a keyboard, a mouse, a joystick, a voice recognition device or any other available user input device. The user input device may also be arranged to receive data from an external memory unit.

[0037] The data memory 74 may include clinical data and / or other information used to obtain a treatment plan. Typically, the data memory 74 includes one or more patient images to be used in treatment planning according to embodiments of the present invention. The program memory 76 stores at least one computer program that is configured to cause the processor to control the delivery system based on the optimized results. If the planning system does not perform the organization of the light spots for delivery as shown in step S23, the processor 73 may also perform this step, i.e., determine the appropriate order for delivering the light spots to minimize delivery time.

[0038] As will be understood, the data memory 74 and program memory 76 are shown and discussed schematically only. There may be several data memory units, each storing one or more different types of data, or one data memory unit storing all data in a suitably structured manner, and the same for the program memory. One or more memories may also be stored on other computers. The computers may also be arranged to perform optimization.

[0039] Although variations in spot shape and orientation have been exemplified above with respect to circular and / or elliptical spots, it will be appreciated that the spot may be given any suitable shape, including triangular, rectangular, or any other geometric shape that may help cover a particular target in the best possible manner, with the aid of aperture devices designed for different shapes.

Claims

1. A computer-based method for generating a radiotherapy treatment plan for delivering charged particles to a target (1) in a patient (61) by pencil beam scanning, said particles being delivered in spots (3, 5), said method involving optimizing said treatment plan using an optimization problem, characterized in that The optimization problem is designed to allow the light spots (3, 5) of each energy layer to differ in at least one of geometry and orientation so that the light spots (3, 5) are positioned and oriented to cover a target cross section.

2. The computer-based method according to claim 1, wherein the optimization problem is designed to allow two or more predefined sets of values ​​for the geometry and / or orientation of the light spot (3, 5).

3. The computer-based method according to claim 1, wherein the optimization problem is designed to allow the light spot (3, 5) to freely vary in at least one of geometry and orientation.

4. A computer-based method according to any one of claims 1 to 3, wherein the optimization problem is designed to allow the light spot (3, 5) to vary in at least one part of the target (1) while keeping the light spot consistent in at least another part of the target (1).

5. The computer-based method of claim 4, wherein the optimization problem is designed to allow the light spot (5) near the target boundary to vary while keeping the light spot (3) in the center of the target (1) consistent.

6. The computer-based method according to any one of claims 1 to 3, further comprising the step of defining a delivery order of the light spots (3, 5) taking into account delivery times.

7. A computer-based method according to any one of claims 1 to 3, wherein the treatment plan is arranged to control an aperture device to define the geometry of the light spot and / or the orientation of the geometry of the light spot.

8. A computer-based method according to any one of claims 1 to 3, wherein the optimization problem is further arranged to allow the size of the light spot (3, 5) to vary.

9. A computer program product comprising computer readable code means which, when run in a processor (33) of a computer (31), causes the processor to perform the method according to any one of claims 1 to 8.

10. The computer program product according to claim 9, comprising non-transitory storage means (36) storing said computer readable code means.

11. A computer system (31) comprising a processor (33), a data memory (34) and a program memory (36), said program memory being arranged to store a computer program in such a manner that it can be run in said processor (33), characterised in that The program memory (36) comprises a computer program product according to claim 9 or 10.

12. A radiotherapy treatment delivery system (60) for delivering charged particles to a patient (61) via a PBS, the particles being delivered in a spot, the system comprising a processor (73) for controlling treatment delivery, characterized in that The system comprises changing means for changing at least one of the geometry and orientation of the light spot for each energy layer during delivery so that the light spot is positioned and oriented to cover a target cross section, and the processor (73) is arranged to control the changing.

13. The radiation therapy treatment delivery system of claim 12, wherein the altering device comprises an electromagnetic optical system.

14. A radiotherapy treatment delivery system according to claim 12, wherein the varying means comprises a controllable aperture device arranged to vary the geometry and / or orientation of the light spot during delivery.

15. The radiotherapy treatment delivery system according to any one of claims 12 to 14, further comprising a memory (74) storing a treatment plan, and the processor (93) being arranged to control the delivery system (60) according to the treatment plan, wherein the treatment plan has been generated using the method according to any one of claims 1 to 8.

Images