Particle beam therapy device
The particle beam therapy apparatus addresses inaccuracies due to patient movement by synchronizing irradiation with respiratory phases, ensuring precise dose distribution and improved treatment outcomes.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- SUMITOMO HEAVY IND LTD
- Filing Date
- 2022-03-25
- Publication Date
- 2026-06-10
Smart Images
Figure 0007872685000001 
Figure 0007872685000002 
Figure 0007872685000003
Abstract
Description
Technical Field
[0001] The present invention relates to a particle beam therapy apparatus.
Background Art
[0002] Conventionally, a particle beam therapy apparatus that irradiates a diseased part of a patient with a charged particle beam emitted from an accelerator has been known. Since there is an upper limit to the dose output by this type of particle beam therapy apparatus, there are cases where it is not possible to finish irradiating the required dose in one irradiation. In such a case, it is necessary to repeatedly execute irradiation to the same location of the diseased part multiple times. For example, the particle beam therapy apparatus of Patent Document 1 below divides the diseased part into a plurality of virtual layers and irradiates each layer by scanning the charged particle beam, performing multiple irradiations on one layer and then moving to the next layer and performing multiple irradiations, and repeating such operations until the required dose of charged particle beam irradiates the diseased part.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] However, in the above-described particle beam therapy apparatus, when the position of the diseased part fluctuates due to the patient's breathing or the like, the positions of the multiple irradiations on one layer of the diseased part shift from each other, so that a so-called Interplay Effect occurs, and there is a risk that the accuracy and effect of the treatment will deteriorate with respect to the planned dose distribution. In view of such problems, an object of the present invention is to provide a particle beam therapy apparatus that accurately realizes irradiation according to a planned dose distribution regardless of the movement of the irradiated object.
Means for Solving the Problems
[0005] The particle beam therapy apparatus of the present invention comprises an accelerator that emits a charged particle beam, and an irradiation unit that has a scanning unit for scanning the charged particle beam and outputs the charged particle beam emitted from the accelerator. For each of the multiple irradiated layers virtually set within the body to be irradiated, the irradiation unit performs an irradiation process in which it irradiates multiple irradiated layers with a charged particle beam in a predetermined irradiation order, and a re-irradiation process in which the irradiation unit irradiates multiple irradiated layers again with a charged particle beam in the same irradiation order as the initial irradiation.
[0006] In the irradiation process, multiple irradiated layers aligned in the direction of irradiation by the charged particle beam may be irradiated in the order they are aligned. The irradiated layers may be set up so that they are stacked in the direction of irradiation by the charged particle beam, and in the irradiation process, all the set irradiated layers may be irradiated in the stacking order. The re-irradiation process may be repeated multiple times.
[0007] In the particle beam therapy apparatus of the present invention, the irradiated body is the affected area of the patient, and the apparatus may further include a synchronization control unit that synchronizes the timing of irradiation with charged particle beams in the irradiation process and re-irradiation process with the phase of the patient's periodic movement. [Effects of the Invention]
[0008] According to the present invention, it is possible to provide a particle beam therapy device that accurately achieves irradiation according to a planned dose distribution, regardless of the movement of the object being irradiated. [Brief explanation of the drawing]
[0009] [Figure 1] This is a schematic diagram showing an example of a charged particle beam therapy apparatus according to the first embodiment. [Figure 2] (a) and (b) are diagrams illustrating the irradiation of an object with a charged particle beam. [Figure 3] This flowchart shows an example of the charged particle beam irradiation process performed by the charged particle beam therapy device shown in Figure 1. [Figure 4](a) is a schematic graph showing the displacement of the irradiated body due to the patient P's respiration for a conventional charged particle beam therapy device, and (b) is a schematic graph showing the displacement of the irradiated body due to the patient P's respiration for the charged particle beam therapy device of the first embodiment. [Figure 5] (a) to (c) are diagrams that conceptually show the radiation dose distribution in a predetermined layer of the irradiated object. [Modes for carrying out the invention]
[0010] Embodiments of the present invention will be described in detail below with reference to the attached drawings. The terms "upstream" and "downstream" refer to the upstream (accelerator side) and downstream (patient side) of the emitted charged particle beam, respectively. The direction of irradiation of the irradiated object A with the charged particle beam is defined as the Z direction, the direction perpendicular to the Z direction is defined as the X direction, and the direction perpendicular to both the Z and X directions is defined as the Y direction.
[0011] [First Embodiment] As shown in Figure 1, the charged particle beam therapy apparatus 1 (particle beam therapy apparatus) is a device used for cancer treatment by radiotherapy, and comprises an accelerator 11 that accelerates charged particles and emits a charged particle beam, an irradiation nozzle 12 (irradiation unit) that irradiates a target with the charged particle beam, a beam transport line 13 that transports the charged particle beam emitted from the accelerator 11 to the irradiation nozzle 12, a degrader 18 provided in the beam transport line 13 that reduces the energy of the charged particle beam to adjust its range, a plurality of electromagnets 25 provided in the beam transport line 13, an electromagnet power supply 27 provided corresponding to each of the plurality of electromagnets 25, and a control unit 30 that controls the entire charged particle beam therapy apparatus 1. In this embodiment, a cyclotron is used as the accelerator 11, but it is not limited to this, and other sources that generate charged particle beams, such as a synchroton, synchrocycloton, linac, etc., may also be used.
[0012] In the charged particle beam therapy apparatus 1, the tumor (irradiated body, affected area) of patient P on the treatment table 22 is irradiated with a charged particle beam emitted from the accelerator 11. A charged particle beam is a particle with an electric charge accelerated to high speed, and examples include proton beams and heavy particle (heavy ion) beams. The charged particle beam therapy apparatus 1 according to this embodiment irradiates with a charged particle beam using a so-called scanning method, dividing (slicing) the irradiated body in the depth direction, and irradiating the irradiation area on each slice plane (layer) with a charged particle beam (see Figures 2(a) and (b)).
[0013] There are two types of irradiation methods using the scanning method: spot-type scanning irradiation and raster-type scanning irradiation. Spot-type scanning irradiation is a method in which, once irradiation of one spot (the irradiation area) is completed, the beam (charged particle beam) irradiation is stopped, and irradiation of the next spot is resumed after preparation for irradiation of the next spot is complete. In contrast, raster-type scanning irradiation is a method in which the beam irradiation is performed continuously without stopping the irradiation in the irradiation area of the same layer. Thus, since raster-type scanning irradiation is performed continuously within the irradiation area of the same layer, unlike spot-type scanning irradiation, the irradiation area does not consist of multiple spots. In the following, we will explain an example of irradiation performed by spot-type scanning irradiation, and will explain it as if the irradiation area on the same layer consists of multiple spots, but it is not limited to this, and when irradiation is performed by raster-type scanning irradiation, the irradiation area does not have to consist of spots as described above.
[0014] The irradiation nozzle 12 is mounted inside a rotating gantry 23 that can rotate 360 degrees around the treatment table 22, and can be moved to any rotational position by the rotating gantry 23. The irradiation nozzle 12 includes a focusing electromagnet 19 (details described later), a scanning electromagnet 21 (scanning unit), and a vacuum duct 28. The scanning electromagnet 21 is located inside the irradiation nozzle 12. The scanning electromagnet 21 has an X-direction scanning electromagnet that scans the charged particle beam in the X direction on a plane intersecting the irradiation direction of the charged particle beam, and a Y-direction scanning electromagnet that scans the charged particle beam in the Y direction intersecting the X direction on a plane intersecting the irradiation direction of the charged particle beam. Furthermore, since the charged particle beam scanned by the scanning electromagnet 21 is deflected in the X direction and / or Y direction, the diameter of the vacuum duct 28 downstream of the scanning electromagnet is increased towards the downstream side.
[0015] The beam transport line 13 has a vacuum duct 14 through which the charged particle beam passes. The inside of the vacuum duct 14 is maintained in a vacuum state, which suppresses scattering of the charged particles constituting the transported charged particle beam by air or other means.
[0016] Furthermore, the beam transport line 13 includes an Energy Selection System (ESS) 15 that selectively extracts charged particle beams with an energy width narrower than a predetermined energy width from a charged particle beam with a predetermined energy width emitted from the accelerator 11, a Beam Transport System (BTS) 16 that transports the charged particle beam with the energy width selected by the ESS 15 while maintaining its energy, and a Gantry Transport System (GTS) 17 that transports the charged particle beam from the BTS 16 toward the rotating gantry 23.
[0017] The degrader 18 adjusts the range of the charged particle beam by reducing its energy. Since the depth from the patient's body surface to the tumor, which is the target of irradiation, varies from patient to patient, it is necessary to adjust the range of the charged particle beam when irradiating a patient with a charged particle beam. The degrader 18 adjusts the energy of the charged particle beam emitted from the accelerator 11 at a constant energy so that the charged particle beam reaches the target of irradiation at a predetermined depth within the patient's body appropriately. This energy adjustment of the charged particle beam by the degrader 18 is performed for each sliced layer of the target of irradiation.
[0018] Multiple electromagnets 25 are provided in the beam transport line 13 and adjust the charged particle beam so that it can be transported in the beam transport line 13 by magnetic field. The electromagnets 25 include focusing electromagnets 19 that converge the beam diameter of the transported charged particle beam, and deflecting electromagnets 20 that deflect the charged particle beam. In the following, focusing electromagnets 19 and deflecting electromagnets 20 may be referred to simply as electromagnets 25 without distinction. Furthermore, multiple electromagnets 25 are provided at least downstream of the degrader 18 in the beam transport line 13. However, in this embodiment, electromagnets 25 are also provided upstream of the degrader 18. Here, focusing electromagnets 19 are also provided upstream of the degrader 18 to converge the beam diameter of the charged particle beam before energy adjustment by the degrader 18. The total number of electromagnets 25 can be flexibly changed depending on the length of the beam transport line 13, for example, between 10 and 40. Although only a portion of the electromagnet power supplies 27 are shown in Figure 1, in reality, the same number of power supplies as the number of electromagnets 25 are provided.
[0019] The positions of the degradator 18 and the electromagnet 25 in the beam transport line 13 are not particularly limited. However, in this embodiment, the ESS 15 is provided with a degradator 18, a focusing electromagnet 19, and a deflection electromagnet 20. Further, the BTS 16 is provided with a focusing electromagnet 19, and the GTS 17 is provided with a focusing electromagnet 19 and a deflection electromagnet 20. The degradator 18 is provided in the ESS 15 between the accelerator 11 and the rotating gantry 23 as described above. More specifically, it is provided on the accelerator 11 side (upstream side) of the rotating gantry 23 in the ESS 15.
[0020] The electromagnet power supply 27 generates a magnetic field of the electromagnet 25 by supplying current to the corresponding electromagnet 25. The electromagnet power supply 27 can set the strength of the magnetic field of the corresponding electromagnet 25 by adjusting the current supplied to the corresponding electromagnet 25. The electromagnet power supply 27 adjusts the current supplied to the electromagnet 25 according to a signal from the control unit 30 (details will be described later). The electromagnet power supply 27 is provided so as to correspond one-to-one to each electromagnet 25. That is, the number of electromagnet power supplies 27 provided is the same as the number of electromagnets 25.
[0021] The relationship between the depth of each layer of the irradiated object and the current supplied from the electromagnet power supply 27 to the electromagnet 25 is as follows. That is, from the depth of each layer, the energy of the charged particle beam required to irradiate each layer is determined, and the energy adjustment amount by the degradator 18 is determined. Here, when the energy of the charged particle beam changes, the strength of the magnetic field required to deflect and focus the charged particle beam also changes. Therefore, the current supplied to the electromagnet 25 is determined so that the strength of the magnetic field of the electromagnet 25 becomes a strength corresponding to the energy adjustment amount by the degradator 18.
[0022] The control unit 30 is, for example, a computer, and controls the irradiation of the irradiated object with the charged particle beam B emitted from the accelerator 11. The control unit 30 has a scanning control unit 36 and a layer control unit 37. The scanning control unit 36 controls the scanning of the irradiated object A with the charged particle beam B. The scanning control unit 36 transmits an irradiation start signal to the scanning electromagnet 21, causing the scanning electromagnet 21 to irradiate multiple irradiation spots on the same layer. Information regarding the irradiation spots in each layer is stored in the scanning control unit 36 in advance based on a pre-set treatment plan.
[0023] The charged particle beam irradiation image of the scanning electromagnet 21 in accordance with the control of the scanning control unit 36 will be explained with reference to Figures 2(a) and (b). Figure 2(a) shows the irradiated object A, which is virtually sliced into multiple layers in the depth direction, and Figure 2(b) shows the scanning image of the charged particle beam B in one layer as viewed from the irradiation direction (Z direction) of the charged particle beam B. As shown in Figure 2(a), the irradiated object A is virtually sliced and divided into multiple layers (irradiated layers) stacked in the irradiation direction (Z direction). In this example, the irradiated object A is virtually sliced and divided into N layers, and these layers are called, in order from the deepest layer (where the range of the charged particle beam B is longest), layer L1, layer L2, ..., layer (n-1), layer n, layer (n+1), ..., layer L(N-1), and layer LN. The value of N in general tumor treatment is, for example, around 30, but it is not limited to this value.
[0024] The energy adjustment amount of the degrader 18 is set to correspond to a predetermined layer Ln, and the scanning electromagnet 21 deflects the charged particle beam B in the X and Y directions, so that, as shown in Figure 2(b), the charged particle beam B irradiates multiple irradiation spots while drawing a zigzag-shaped beam trajectory TL on layer Ln. As a result, the charged particle beam B irradiates the entire layer Ln of the irradiated object A. In general tumor treatment, the time required to irradiate one layer Ln is, for example, several hundred msec to about 2 seconds, but this value is not limited to that.
[0025] Furthermore, when the scanning control unit 36 has completed irradiating all spots in one layer with the scanning electromagnet 21, it transmits a layer switching signal to the layer control unit 37. This layer switching signal includes information that identifies the layer after the switch (for example, layer L(n+1), etc.). The layer control unit 37 performs layer switching-related processing in response to the layer switching signal from the scanning control unit 36. The layer switching-related processing includes degrader setting processing, which changes the energy adjustment amount of the degrader 18, and electromagnet setting processing, which sets the current supplied to the electromagnet 25 to match the energy adjustment amount of the degrader 18 after the degrader setting processing. The time required for this layer switching-related processing is, for example, about 300 msec, but is not limited to this value.
[0026] In charged particle beam therapy, a treatment plan is created to determine how to irradiate a patient with charged particle beam B. The treatment plan data determined during this planning stage is transmitted from a treatment planning device (not shown) to a control unit 30 before treatment is performed and stored in the control unit 30. Based on this treatment plan, the scanning control unit 36 and layer control unit 37 execute the control described above, and irradiate each of the layers L1 to LN, which are virtually set up in multiple layers Ln within the irradiated object A, with charged particle beam B while scanning along the beam trajectory TL (see Figure 2(b)), thereby irradiating the entire irradiated object A with charged particle beam B.
[0027] Furthermore, as shown in Figure 1, the charged particle beam therapy device 1 is equipped with a respiratory synchronization control unit 40 (synchronization control unit), which synchronizes the timing of irradiation of the charged particle beam B from the irradiation nozzle 12 with the respiratory phase of the patient P. The respiratory synchronization control unit 40 detects the respiratory phase of the patient P by, for example, monitoring the displacement of the patient P's body surface with an imaging device or laser displacement meter. The detected respiratory phase information is transmitted as an electrical signal to the control unit 30, and the control unit 30 controls the timing of outputting the charged particle beam B from the irradiation nozzle 12 based on the obtained respiratory phase. The respiratory synchronization control unit 40 performs control such as irradiating the charged particle beam B only when the displacement of the irradiated body A (the affected area of the patient P) due to respiration is smaller than a predetermined value, and further performs control such as irradiating the charged particle beam B only within a specific respiratory phase range when the above displacement is smaller than the predetermined value. As the above specific respiratory phase range, for example, a respiratory phase range in which the displacement of the affected area due to respiration is relatively small is selected. The presence of this respiratory synchronization control unit 40 helps to suppress the relative discrepancy between the irradiated object A and the irradiation position due to the positional changes caused by the patient P's respiration, even when the irradiated object A is a moving organ whose position changes almost periodically due to the patient P's respiration.
[0028] The charged particle beam irradiation process performed on the irradiated body A by the charged particle beam therapy device 1 described above will now be explained. This charged particle beam irradiation process is realized when a control unit 30, which is composed of a computer, executes a predetermined irradiation program, and under the control of the control unit 30, the degrader 18, scanning electromagnet 21, respiratory synchronization control unit 40, etc., which have the aforementioned functions, operate.
[0029] Since there is an upper limit to the dose output by the charged particle beam therapy device 1, it may not be possible to complete the required dose of irradiation for each layer L1 to LN of the irradiated body A in a single irradiation. The charged particle beam irradiation process of this embodiment is applied in such cases, and it is necessary to repeat irradiation of the same layer Ln multiple times. In the charged particle beam irradiation process of this embodiment, in order to simplify the treatment plan, irradiation of the same layer Ln is performed with the same dose each time, and the number of required irradiations is denoted as M. The value of M in the treatment of a typical tumor is, for example, around 3 to 5, but it is not limited to this value.
[0030] The specific charged particle beam irradiation process S10 will be explained with reference to the flowchart in Figure 3. During this charged particle beam irradiation process S10, the respiratory synchronization process by the aforementioned respiratory synchronization control unit 40 is executed in parallel.
[0031] In the flowchart of Figure 3, we conveniently use variables n (n=1 to N) indicating which layer Ln is, and m (m=1 to M) indicating which number the layer Ln has been irradiated with. As shown in Figure 3, in order to perform the first irradiation of layer L1 at the beginning of this charged particle beam irradiation process S10, the initial values of the above variables m and n are set to m=1 (S102) and n=1 (S104). In the subsequent process S106, the charged particle beam B from the irradiation nozzle 12 is irradiated onto layer Ln of the irradiated object A. Here, with the energy adjustment amount of the degrader 18 set to an amount corresponding to the depth of layer Ln, scanning in the X and Y directions is performed by the scanning electromagnet 21, so that the charged particle beam B is irradiated onto layer Ln along the beam trajectory TL (see Figure 2(b)).
[0032] Subsequently, in process S108, it is determined whether the variable n has reached N, which corresponds to the shallowest layer. If the variable n has reached N, it means that the mth irradiation of all layers L1 to LN of the irradiated object A has been completed, and in this case, the process proceeds to S110. On the other hand, if the determination in process S108 is that the variable n has not reached N, then in process S112, the variable n is incremented (plus 1), and the process returns to the aforementioned process S106. Then, processes S106, S108, and S112 are repeated until the variable n reaches N in process S108. In other words, the irradiation of each layer with the charged particle beam B is repeatedly performed, switching between layers L2, L3, ..., LN.
[0033] In process S110, it is determined whether the variable m has reached M, which corresponds to the final number of irradiations. If the variable m has reached M, it means that all irradiations from the 1st to the Mth time have been completed for all layers L1 to LN of the irradiated object A, and the charged particle beam irradiation process S10 is terminated. On the other hand, if the determination in process S110 is that the variable m has not reached M, then in process S114, the variable m is incremented (plus 1), and the process returns to S104. Then, in process S104, n is initialized to n=1 again, and the aforementioned processes S106, S108, and S112 are executed again. Then, in process S110, processes S104 to S114 are repeated until the variable m reaches M, and finally, in process S110, when the variable m reaches M, the charged particle beam irradiation process S10 is terminated.
[0034] As shown by the dashed line in Figure 3, if we consider the series of processes S104, S106, S108, and S112 together as "irradiation process S201", then in this charged particle beam irradiation process S10, it can be said that irradiation process S201 is repeated M times. In other words, charged particle beam irradiation process S10 can be said to include one irradiation process S201 in which each layer L1 to LN is irradiated with charged particle beam B in the order of layer L1, layer L2, ..., layer LN, and (M-1) re-irradiation processes S202 in which each layer L1 to LN is irradiated with charged particle beam B in the same order as irradiation process S201 (layer L1, layer L2, ..., layer LN). To put it another way, the charged particle beam therapy device 1 irradiates charged particles in the order of (layer L1, layer L2, ..., layer LN), (layer L1, layer L2, ..., layer LN), ...
[0035] Furthermore, as mentioned above, during the charged particle beam irradiation process S10, the respiratory synchronization process by the respiratory synchronization control unit 40 is performed in parallel. Therefore, the charged particle beam B is irradiated onto layer Ln only when the displacement of the irradiated body A (the affected area of patient P) due to respiration is smaller than a predetermined value and the respiratory phase of patient P is within a specific respiratory phase range; otherwise, the irradiation of the charged particle beam B is stopped (beam off).
[0036] The effects of the charged particle beam therapy device 1 described above will now be explained. Figures 4(a) and 4(b) are graphs that schematically represent the change in the positional displacement of the irradiated object A due to the patient P's respiration, with the horizontal axis representing time and the vertical axis representing the displacement of the irradiated object A from the treatment plan. Assuming that the patient P's respiration is periodic, the horizontal axis can be considered to represent the phase of the patient P's respiration. In the charged particle beam therapy device 1, the respiratory synchronization control unit 40 performs control such as irradiating the charged particle beam B only when the displacement of the irradiated object A is smaller than a predetermined value (displacement range E in the figure), and irradiating the charged particle beam B only within a specific respiratory phase range (phase range F in the figure) within the displacement range E.
[0037] Conventional charged particle beam therapy devices irradiate the charged particle beam B in the order of (layer L1, layer L1, ..., layer L1), (layer L2, layer L2, ..., layer L2), ..., (layer LN, layer LN, ..., layer LN). If we were to plot the irradiation timing for each layer on a graph, it would look like Figure 4(a), for example. That is, irradiation to layer L1 is repeated within the phase range F of the first respiration cycle, irradiation to layer L2 is repeated within the phase range F of the second respiration cycle, ..., and irradiation to layer LN is repeated within the phase range F of the Nth respiration cycle.
[0038] In contrast, the charged particle beam therapy apparatus 1 of this embodiment irradiates the charged particle beam in the order of (layer L1, layer L2, ..., layer LN), (layer L1, layer L2, ..., layer LN), ..., so if we were to plot the irradiation timing for each layer on a graph, it would look like Figure 4(b), for example. That is, irradiation from layers L1 to LN is performed while switching layers within the phase range F of the first respiration cycle, the same process as in the first cycle is performed in the second respiration cycle, and the same process as in the first cycle is repeated in the third to M respiration cycles.
[0039] In conventional charged particle beam therapy devices, as shown in Figure 4(a), irradiation to layer L1 is repeated multiple times (e.g., M times) while the irradiated object A is gradually displaced within the phase range F of the first respiration cycle. Therefore, the respiration phase differs slightly each time for the first, second, ..., Mth irradiations to layer L1, meaning the position of the irradiated object A differs slightly each time. Consequently, the positional displacement between the irradiation position to layer L1 and the irradiated object A differs slightly with each irradiation, making it easier for the interplay effect to occur in layer L1, i.e., unevenness in the irradiation dose within layer L1 is likely to occur. Similarly, unevenness in the irradiation dose is likely to occur in layers L2 to LN. In other words, the irradiation dose distribution on the irradiated object A deteriorates compared to the treatment plan.
[0040] In contrast, in the charged particle beam therapy apparatus 1 of this embodiment, for example, irradiation of layers L1, L2, ..., LN is performed sequentially within the phase range F of the first respiratory cycle, and in the second, third, ... respiratory cycles, irradiation of layers L1, L2, ..., LN is performed in the same order within the phase range F. Therefore, for example, the respiratory phases for the first, second, ..., Mth irradiations to layer L1 tend to be approximately the same each time, meaning that the position of the irradiated body A tends to be approximately the same each time. Consequently, the positional misalignment between the irradiation position to layer L1 and the irradiated body A tends to be the same for each irradiation, and as a result, the interplay effect is less likely to occur in layer L1, meaning that unevenness in the irradiation dose within layer L1 is less likely to occur. Similarly, unevenness in the irradiation dose is less likely to occur for layers L2 to LN. In other words, a good irradiation dose distribution on the irradiated body A can be obtained in accordance with the treatment plan.
[0041] In this embodiment, an example was described in which irradiation of layers L1 to LN is performed within one respiratory cycle. However, if, for example, the respiratory cycle is short compared to the number of layers N, irradiation of layers L1 to LN may be performed over multiple respiratory cycles. Specifically, for example, irradiation of layers L1 to L5 may be performed within the phase range F of the first respiratory cycle, irradiation of layers L6 to L10 may be performed within the phase range F of the second respiratory cycle, and so on, with irradiation of layers L1 to LN being performed sequentially over multiple breaths of the patient.
[0042] Figures 5(a) to 5(c) conceptually show the irradiation dose distribution irradiated to a predetermined layer Ln of the irradiated object A. Figure 5(a) shows the irradiation dose distribution by the conventional charged particle beam therapy device described above, and Figure 5(b) shows the irradiation dose distribution by the charged particle beam therapy device 1 of this embodiment. Figure 5(c) shows the irradiation dose distribution when irradiation is performed under ideal conditions where the irradiated object A does not displace. As shown in Figure 5(a), with the conventional charged particle beam therapy device, areas of high / low irradiation dose (unevenness) appear along the zigzag-shaped beam trajectory TL (Figure 2(b)). For example, as indicated by reference numerals 91 and 92 in the figure, there are areas with extremely high irradiation doses 91 (Hot Spot) and extremely low irradiation doses 92 (Cold Spot) in the central part 93 of layer Ln.
[0043] In contrast, as shown in Figure 5(b), with the charged particle beam therapy apparatus 1 of this embodiment, unevenness in irradiation dose is less likely to appear in the central part 93 of layer Ln. However, compared to the ideal irradiation dose distribution shown in Figure 5(c), in the charged particle beam therapy apparatus 1 of this embodiment, the irradiation dose distribution as a whole is shifted and an error in irradiation dose appears biased towards the outer edge 94 of layer Ln. Nevertheless, this is preferable to the state in which unevenness is scattered in the central part 93 of layer Ln, as in conventional charged particle beam therapy apparatuses (Figure 5(a)). In other words, the error in irradiation dose that appears at the outer edge 94 of layer Ln can be resolved by other means, such as robust optimization of the treatment plan.
[0044] As described above, the charged particle beam therapy device 1 is less prone to uneven irradiation dose within each layer L1 to LN compared to conventional charged particle beam therapy devices. Therefore, regardless of the movement of the irradiated body A, irradiation according to the dose distribution determined in the treatment plan can be accurately achieved for the irradiated body A, and consequently, the quality of treatment can be improved.
[0045] In order to obtain the above-mentioned effects more efficiently, the respiratory synchronization processing by the respiratory synchronization control unit 40 may perform control such as aligning the start timing of each irradiation process S201 (the start timing of irradiation to layer L1) with a predetermined respiratory phase timing (for example, the start timing of phase range F). Furthermore, as mentioned above, if irradiation to layers L1 to LN is performed sequentially during multiple breaths of the patient, for example, irradiation to layers L1 to L5 is performed within the phase range F of the first respiratory cycle, and irradiation to layers L6 to L10 is performed within the phase range F of the second respiratory cycle, etc., then control may be performed such that the start timing of each irradiation to layers L1, L6, etc. in each irradiation process S201 is aligned with a predetermined respiratory phase timing (for example, the start timing of phase range F).
[0046] [Second Embodiment] The equipment configuration of the charged particle beam therapy apparatus 201 in this embodiment is the same as that of the charged particle beam therapy apparatus 1, as shown in Figure 1. Furthermore, the charged particle beam irradiation process performed by the charged particle beam therapy apparatus 201 is the same as the charged particle beam irradiation process S10 shown in the flowchart of Figure 3. That is, the charged particle beam therapy apparatus 201 in this embodiment performs charged particle beam irradiation in the order of (layer L1, layer L2, ..., layer LN), (layer L1, layer L2, ..., layer LN), ...
[0047] However, the charged particle beam therapy apparatus 201 of this embodiment differs from the charged particle beam therapy apparatus 1 in that the respiratory synchronization process by the respiratory synchronization control unit 40 is not performed during the charged particle beam irradiation process S10. Such a charged particle beam therapy apparatus 201 targets an irradiated body A, for example, which has relatively small displacement due to the patient P's respiration, as the target of the charged particle beam B. The displacement of the irradiated body A due to the patient P's respiration is present to a degree that cannot be ignored, but is not very large.
[0048] According to this charged particle beam therapy device 201, similar to the charged particle beam therapy device 1 of the first embodiment, for example, irradiation to layers L1, L2, ..., LN is performed sequentially within the phase range F of the first respiratory cycle, and in the second, third, ... respiratory cycles, irradiation to layers L1, L2, ..., LN is performed in the same order within the phase range F. However, since respiratory synchronization processing is not performed at this time, for example, the respiratory phases of the first, second, ..., Mth irradiations to layer L1 are not strongly correlated with each other. Therefore, the position of the irradiated body A in each irradiation to layer L1 tends to be random, and as a result, the positional difference between the irradiation position to layer L1 and the irradiated body A varies randomly, so the total dose irradiated to layer L1 each time tends to be equalized across the entire layer L1. As a result, the interplay effect is less likely to occur in layer L1, that is, unevenness in the irradiation dose within layer L1 is less likely to occur. Similarly, for layers L2 to LN, unevenness in irradiation dose is less likely to occur.
[0049] For comparison, let's consider the conventional charged particle beam therapy device mentioned earlier. As previously stated, the conventional charged particle beam therapy device irradiates the charged particle beam B in the order of (layer L1, layer L1, ..., layer L1), (layer L2, layer L2, ..., layer L2), ..., (layer LN, layer LN, ..., layer LN). In such a conventional charged particle beam therapy device, for example, each irradiation to layer L1 is repeated continuously while the irradiated body A is gradually displaced. Therefore, even without respiratory gating, the respiratory phase at each irradiation to layer L1 contains regularity, at least compared to the case of the charged particle beam therapy device 201. Consequently, compared to the charged particle beam therapy device 201, the randomness of the position of the irradiated body A at each irradiation to layer L1 is lower, and as a result, the tendency for the total dose irradiated to layer L1 each time to be equalized across the entire layer L1 is lower. Similarly, for layers L2 to LN, the tendency for the total dose irradiated each time to be equalized across the entire layer is also lower. Therefore, conventional charged particle beam therapy devices cannot achieve the same effects as charged particle beam therapy device 201.
[0050] As described above, in a charged particle beam therapy device 201 targeting an irradiated object A with relatively small displacement, the unevenness of the irradiation dose to the irradiated object A can be reduced without using respiratory synchronization processing by the respiratory synchronization control unit 40. As a result, irradiation to the irradiated object A according to the dose distribution determined in the treatment plan can be accurately achieved, thereby improving the quality of treatment. In this case, the effort required to set up the respiratory synchronization control unit 40 and the waiting time for beam off due to respiratory synchronization processing are saved, and the treatment time can be shortened. Note that in the charged particle beam therapy device 201, the respiratory synchronization control unit 40 that is not used may be omitted.
[0051] The present invention can be implemented in various forms, including the embodiments described above, by making various changes and improvements based on the knowledge of those skilled in the art. Furthermore, it is possible to construct modified versions by utilizing the technical matters described in the embodiments described above. The configurations of each embodiment may be used in appropriate combinations.
[0052] In the above-described embodiment, the irradiated body A targeted by the charged particle beam therapy apparatus 1 was a mobile organ whose position changes due to the patient P's respiration. However, the irradiated body A may also be a mobile organ whose position changes regularly or periodically due to movements other than the patient P's respiration.
[0053] In the above-described embodiment, the irradiation order to each layer L1 to LN in irradiation process S201 and re-irradiation process S202 was layer L1, layer L2, ..., layer LN, but the irradiation order is not limited to this. As long as the irradiation order is the same in irradiation process S201 and re-irradiation process S202, the following irradiation order may be used.
[0054] If the irradiation order is the same in irradiation process S201 and re-irradiation process S202, then in irradiation process S201, the charged particle beam B may be irradiated to each layer L1 to LN in a random order, for example, layer L4, layer L2, layer L7, layer L1, ...
[0055] Here, when the irradiated layer is switched in irradiation process S201, the energy adjustment amount of the degrader 18 is switched as described above, and the magnetic field on the beam transport line 13 is switched by switching the supply current from the electromagnet power supply 27 to each electromagnet 25 according to this energy adjustment amount. Since the magnetic field generated by the electromagnets 25 exhibits hysteresis with respect to the supply current, in order to simplify the control of the magnetic field during irradiation of each layer, it is preferable to switch the supply current to the electromagnets 25 in a way that unilaterally increases or decreases it each time the layer is switched.
[0056] Based on this finding, in irradiation treatment S201, an irradiation order that lengthens or shortens the range of the charged particle beam, such as layer L4, layer L2, layer L7, layer L1, ..., is undesirable. For example, it is preferable to irradiate in the order of the layers on the irradiated object A (in order from longer to shorter range of charged particle beam B), such as layer L1, layer L2, layer L4, layer L7, ..., or layer L7, layer L4, layer L2, layer L1, .... Furthermore, it is even more preferable to irradiate all layers on the irradiated object A in the stacking order, such as layer L1, layer L2, ..., layer LN in the above embodiment, or in the reverse order, such as layer LN, layer L(N-1), ..., layer L2, layer L1.
[0057] Furthermore, the charged particle beam therapy apparatus 1,201 of this embodiment performs irradiation processing S201 once, and then performs re-irradiation processing S202 (M-1) times, which irradiates in the same order as irradiation processing S201. However, re-irradiation processing S202 only needs to be performed at least once. For example, after irradiation processing S201 and re-irradiation processing S202 have been performed, irradiation processing may be performed that skips layers that do not require irradiation (for example, in the order of layer L1, layer L3, layer L4, layer L5, ...). Also, it is not essential that re-irradiation processing S202 is performed immediately after irradiation processing S201. Other irradiation processing with a different order from irradiation processing S201 may be performed between irradiation processing S201 and re-irradiation processing S202. [Explanation of symbols]
[0058] 1,201...Charged particle beam therapy device, 11...Accelerator, 12...Irradiation nozzle (irradiation unit), 21...Scanning electromagnet (scanning unit), 40...Respiratory synchronization control unit (synchronization control unit), L1~LN...Irradiated layer, A...Irradiated body (affected area), B...Charged particle beam, P...Patient, S201...Irradiation process, S202...Re-irradiation process.
Claims
1. An accelerator that emits charged particle beams, The system comprises a scanning unit for scanning the charged particle beam and an irradiation unit for outputting the charged particle beam emitted from the accelerator, For each of the multiple irradiated layers virtually set within the body to be irradiated, the irradiation unit performs an irradiation process in which it irradiates the multiple irradiated layers with the charged particle beam in a predetermined irradiation order, and a re-irradiation process in which the irradiation unit irradiates the multiple irradiated layers with the charged particle beam again in the same irradiation order as the first irradiation order. The timing of the irradiation process and the re-irradiation process is controlled to be synchronized with the phase of the periodic displacement of the irradiated object. The charged particle beam is irradiated only when the displacement of the irradiated object is within a predetermined range set to be less than the maximum value of the displacement and greater than the minimum value of the displacement. For the same irradiated layer, the phase during the irradiation process and the phase during the re-irradiation process are controlled to be the same. Particle beam therapy equipment.
2. The particle beam therapy apparatus according to claim 1, wherein in the re-irradiation process, the charged particle beam is irradiated to all of the irradiated layers that were irradiated with the charged particle beam in the irradiation process.
3. The particle beam therapy apparatus according to claim 1, wherein between the irradiation process and the re-irradiation process, another irradiation process is performed that is in a different order from the irradiation process.
4. The particle beam therapy apparatus according to claim 1, wherein the irradiation process is performed on a plurality of irradiated layers arranged in the direction of irradiation of the charged particle beam, in the order they are arranged.
5. The particle beam therapy apparatus according to claim 4, wherein the irradiated layers are configured to be stacked in the direction of irradiation of the charged particle beam, and in the irradiation process, the irradiation is performed on all the configured irradiated layers in the stacking order.
6. The particle beam therapy apparatus according to any one of claims 1 to 5, wherein the re-irradiation process is performed repeatedly multiple times.
7. The irradiated body is the affected area of the patient. The particle beam therapy apparatus according to any one of claims 1 to 6, further comprising a synchronization control unit that synchronizes the timing of irradiation of the charged particle beam in the irradiation process and the re-irradiation process with the phase of the patient's periodic movement.