Charged Particle Beam Irradiation Method and Charged Particle Beam Irradiation System

Abstract

To provide a charged particle beam irradiation system capable of appropriately irradiating an irradiated body with a charged particle beam.SOLUTION: Penumbra adjustment of a charged particle beam B by a snout degrader 30 makes it possible, when an irradiation unit 2 irradiates the vicinity of a boundary of a tumor 14, to inhibit the outside of the tumor 14 from being irradiated with the charged particle beam B. The irradiation unit 2 has a holding unit 60 for holding the snout degrader 30. Accordingly, positioning between the charged particle beam B with which the tumor 14 is to be irradiated and the snout degrader 30 can be performed easily. Accordingly, the irradiation unit 2 can irradiate the tumor 14 with the charged particle beam B in a state of penumbra adjustment being performed at an appropriate position by the snout degrader 30. The positioning is easy because only holding of the snout degrader 30 by the holding unit 60 is required.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a charged particle beam irradiation system.

Background Art

[0002] Conventionally, as a charged particle beam irradiation system for treating a patient's affected area by irradiating the affected area with a charged particle beam, for example, the apparatus described in Patent Document 1 is known. In the charged particle beam irradiation system described in Patent Document 1, the irradiation unit irradiates the charged particle beam by a scanning method. That is, the irradiation unit performs irradiation while moving the irradiation position of the charged particle beam with respect to the affected area by scanning with a scanning electromagnet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, when the irradiation unit irradiates the charged particle beam by a scanning method, there is a problem that a therapeutic dose is applied to the outside of the irradiated object due to, for example, a large beam size of the charged particle beam. Therefore, it has been required to appropriately irradiate the irradiated object with the charged particle beam.

[0005] Therefore, an object of the present invention is to provide a charged particle beam irradiation system capable of appropriately irradiating an irradiated object with a charged particle beam.

Means for Solving the Problems

[0006] In order to solve the above problems, a charged particle beam irradiation system according to the present invention is a charged particle beam irradiation system that irradiates a charged particle beam onto an irradiated object within an object, and includes an irradiation unit that irradiates the charged particle beam onto the irradiated object by scanning the charged particle beam with a scanning electromagnet, an adjustment member that adjusts the penumbra of the scanned charged particle beam, and a holding unit that is provided in the irradiation unit and holds the adjustment member.

[0007] The charged particle beam irradiation system according to the present invention includes an irradiation unit that irradiates a charged particle beam onto an irradiated object by scanning the charged particle beam with a scanning electromagnet, and an adjustment member that adjusts the penumbra of the charged particle beam. Therefore, by adjusting the penumbra of the charged particle beam by the adjustment member, it is possible to suppress the irradiation of the charged particle beam outside the irradiated object when the irradiation unit irradiates near the boundary of the irradiated object. Here, the holding unit that holds the adjustment member is provided in the irradiation unit. Therefore, the irradiation unit can irradiate the charged particle beam onto the irradiated object in a state where the penumbra is adjusted at an appropriate position by the adjustment member. From the above, the irradiation unit can appropriately irradiate the charged particle beam onto the irradiated object.

[0008] The holding unit may be provided at the tip of the irradiation unit. In this case, the adjustment member can adjust the penumbra at a position close to the object. Therefore, after the adjustment member adjusts the penumbra, the charged particle beam is quickly irradiated onto the irradiated object before the spread of the beam becomes large.

[0009] The adjustment member may have an adjustment level of the penumbra corresponding to the depth of the irradiated object within the object. In this case, the adjustment member can adjust the penumbra at the adjustment level of the penumbra corresponding to the depth of the irradiated object within the object.

[0010] The charged particle beam irradiation system may be configured to be able to select the adjustment level of the penumbra of the adjustment member based on the depth of the irradiated object within the object. In this case, the adjustment member can adjust the penumbra at an appropriate adjustment level of the penumbra according to the depth of the irradiated object within the object.

[0011] The charged particle beam irradiation system may be configured to be able to select the adjustment level of the penumbra of the adjustment member based on the distance between the object and the irradiation unit. In this case, the adjustment member can adjust the penumbra at an appropriate adjustment level of the penumbra according to the distance between the object and the irradiation unit.

[0012] The charged particle beam irradiation system may further include a detection unit that detects when an incorrect adjustment member is arranged with respect to the holding unit. In this case, it is possible to suppress the adjustment of the penumbra with an adjustment member related to an inappropriate adjustment level.

Effect of the Invention

[0013] According to the present invention, it is possible to provide a charged particle beam irradiation system that can appropriately irradiate a subject with a charged particle beam.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0015] Hereinafter, a charged particle beam irradiation system according to an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are given to the same elements, and redundant descriptions are omitted.

[0016] FIG. 1 is a schematic configuration diagram showing a charged particle beam irradiation system 1 according to an embodiment of the present invention. The charged particle beam irradiation system 1 is a system used for cancer treatment and the like by radiation therapy. The charged particle beam irradiation system 1 includes an accelerator 3 that accelerates charged particles generated by an ion source device and emits them as a charged particle beam, an irradiation unit 2 that irradiates a subject with the charged particle beam, and a beam transport line 21 that transports the charged particle beam emitted from the accelerator 3 to the irradiation unit 2. The irradiation unit 2 is attached to a rotating gantry 5 provided so as to surround a treatment table 4. The irradiation unit 2 is rotatable around the treatment table 4 by the rotating gantry 5. The more detailed configurations of the accelerator 3, the irradiation unit 2, and the beam transport line 21 will be described later.

[0017] FIG. 2 is a schematic configuration diagram near the irradiation unit 2 of the charged particle beam irradiation system 1 in FIG. 1. In the following description, the terms "X-axis direction", "Y-axis direction", and "Z-axis direction" will be used for explanation. The "Z-axis direction" is the direction in which the base axis AX of the charged particle beam B extends, and is the depth direction of the irradiation of the charged particle beam B. The "base axis AX" is defined as the irradiation axis of the charged particle beam B when it is not deflected by a scanning electromagnet 50 described later. FIG. 2 shows a state in which the charged particle beam B is irradiated along the base axis AX. The "X-axis direction" is one direction in a plane orthogonal to the Z-axis direction. The "Y-axis direction" is a direction orthogonal to the X-axis direction in a plane orthogonal to the Z-axis direction.

[0018] First, referring to FIG. 2, the schematic configuration of the charged particle beam irradiation system 1 according to the present embodiment will be described. The charged particle beam irradiation system 1 is an irradiation device according to a scanning method. The scanning method is not particularly limited, and line scanning, raster scanning, spot scanning, etc. may be adopted. As shown in FIG. 2, the charged particle beam irradiation system 1 includes an accelerator 3, an irradiation unit 2, a beam transport line 21, a control unit 7, a treatment planning device 90, and a storage unit 95.

[0019] The accelerator 3 is a device that accelerates charged particles and emits a charged particle beam B having a preset energy. Examples of the accelerator 3 include a cyclotron, a synchrocyclotron, and a linac. When a cyclotron that emits a charged particle beam B having a preset energy is adopted as the accelerator 3, the energy of the charged particle beam sent to the irradiation unit 2 can be adjusted (lowered) by adopting an energy adjustment unit. This accelerator 3 is connected to the control unit 7, and the supplied current is controlled. The charged particle beam B generated by the accelerator 3 is transported to the irradiation unit 2 by the beam transport line 21. The beam transport line 21 connects the accelerator 3 and the irradiation unit 2 and transports the charged particle beam emitted from the accelerator 3 to the irradiation unit 2.

[0020] The beam transport line 21 has an energy adjustment device (ESS: Energy Selection System) that adjusts the energy of the charged particle beam B while transporting it. Among these, the beam transport line 21 has an energy degrader 20 near the exit of the accelerator 3. The energy degrader 20 is a member that adjusts the range of the charged particle beam B and adjusts the depth of arrival of the charged particle beam B in the body of the patient 15 (object). The energy degrader 20 adjusts the range by causing the charged particle beam B to lose energy. The energy degrader 20 can adjust the range of the charged particle beam B by adjusting the thickness of the portion through which the charged particle beam B passes. Note that in addition to the energy loss in the energy degrader 20, the ESS also suppresses (using a collimator) the energy fluctuations and beam size expansion that occur in the beam transport line downstream of the ESS. The energy degrader 20 is composed of a material such as beryllium or carbon, for example. The energy degrader 20 is arranged at a position on the upstream side (i.e., on the accelerator 3 side) in the traveling direction of the charged particle beam B in the beam transport line 21. In the example shown in FIG. 1, the energy degrader 20 is arranged at the most upstream position among the devices such as the electromagnets of the beam transport line 21, immediately after the accelerator 3, in the path upstream of the rotating gantry 5. However, the position of the energy degrader 20 in the beam transport line 21 is not particularly limited.

[0021] The irradiation unit 2 irradiates the tumor (object to be irradiated) 14 in the body of the patient 15 (object) with a charged particle beam B. The charged particle beam B is obtained by accelerating particles having an electric charge at high speed, and examples thereof include a proton beam, a heavy particle (heavy ion) beam, and an electron beam. Specifically, the irradiation unit 2 is a device that irradiates the tumor 14 with the charged particle beam B emitted from an accelerator 3 that accelerates charged particles generated by an ion source (not shown) and transported by a beam transport line 21. The irradiation unit 2 includes a scanning electromagnet 50, quadrupole electromagnets 8, a profile monitor 11, a dose monitor 12, position monitors 13a and 13b, a collimator 40, and a snow degrader 30 (adjusting member). The scanning electromagnet 50, each monitor 11, 12, 13a, 13b, the quadrupole electromagnets 8, and the snow degrader 30 are housed in an irradiation nozzle 9 as a housing. In this way, the irradiation unit 2 is configured by housing each main component in the irradiation nozzle 9. Note that the quadrupole electromagnets 8, the profile monitor 11, the dose monitor 12, and the position monitors 13a and 13b may be omitted.

[0022] As the scanning electromagnet 50, an X-axis direction scanning electromagnet 50A and a Y-axis direction scanning electromagnet 50B are used. The X-axis direction scanning electromagnet 50A and the Y-axis direction scanning electromagnet 50B are each composed of a pair of electromagnets, change the magnetic field between the pair of electromagnets according to the current supplied from the control unit 7, and scan the charged particle beam B passing between the electromagnets. The X-axis direction scanning electromagnet 50A scans the charged particle beam B in the X-axis direction, and the Y-axis direction scanning electromagnet 50B scans the charged particle beam B in the Y-axis direction. These scanning electromagnets 50 are on the central axis AX and are arranged in this order on the downstream side of the charged particle beam B from the accelerator 3. Note that the scanning electromagnet 50 scans the charged particle beam B so that the charged particle beam B is irradiated in a scan pattern planned in advance by the treatment planning device 90. How to control the scanning electromagnet 50 will be described later.

[0023] The quadrupole electromagnet 8 includes an X-axis direction quadrupole electromagnet 8a and a Y-axis direction quadrupole electromagnet 8b. The X-axis direction quadrupole electromagnet 8a and the Y-axis direction quadrupole electromagnet 8b constrict and converge the charged particle beam B according to the current supplied from the control unit 7. The X-axis direction quadrupole electromagnet 8a converges the charged particle beam B in the X-axis direction, and the Y-axis direction quadrupole electromagnet 8b converges the charged particle beam B in the Y-axis direction. By changing the current supplied to the quadrupole electromagnet 8 to change the aperture amount (convergence amount), the beam size of the charged particle beam B can be changed. The quadrupole electromagnet 8 is arranged on the base axis AX in this order between the accelerator 3 and the scanning electromagnet 50. Note that the beam size is the size of the charged particle beam B in the XY plane. Also, the beam shape is the shape of the charged particle beam B in the XY plane.

[0024] The profile monitor 11 detects the beam shape and position of the charged particle beam B for alignment during initial setting. The profile monitor 11 is arranged on the base axis AX between the quadrupole electromagnet 8 and the scanning electromagnet 50. The dose monitor 12 detects the dose of the charged particle beam B. The dose monitor 12 is arranged on the base axis AX on the downstream side with respect to the scanning electromagnet 50. The position monitors 13a, 13b detect and monitor the beam shape and position of the charged particle beam B. The position monitors 13a, 13b are arranged on the base axis AX on the downstream side of the charged particle beam B with respect to the dose monitor 12. Each of the monitors 11, 12, 13a, 13b outputs the detected detection result to the control unit 7.

[0025] The collimator 40 is a member provided at least on the downstream side of the charged particle beam B with respect to the scanning electromagnet 50, which shields a part of the charged particle beam B and allows a part to pass through. Here, the collimator 40 is provided on the downstream side of the position monitors 13a, 13b. The collimator 40 is connected to a collimator drive unit 51 that moves the collimator 40.

[0026] The snow degreaser 30 reduces the energy of the passing charged particle beam B to adjust the energy of the charged particle beam B. The snow degreaser 30 is configured as an adjustment member for adjusting the penumbra of the charged particle beam B. In the present embodiment, the snow degreaser 30 is held by a holding portion 60 provided at the tip portion 9a of the irradiation nozzle 9. Note that the tip portion 9a of the irradiation nozzle 9 is the end portion on the downstream side of the charged particle beam B. Details of the snow degreaser 30 and the holding portion 60 will be described later.

[0027] The control unit 7 is composed of, for example, a CPU, a ROM, and a RAM. Based on the detection results output from each monitor 11, 12, 13a, 13b, the control unit 7 controls the accelerator 3, the thickness adjustment mechanism of the energy degreaser 20, the scanning electromagnet 50, the quadrupole electromagnet 8, and the collimator drive unit 51.

[0028] In addition, the control unit 7 of the charged particle beam irradiation system 1 is connected to a treatment planning device 90 that performs a treatment plan for charged particle beam therapy and a storage unit 95 that stores various data. The treatment planning device 90 measures the tumor 14 of the patient 15 by CT or the like before treatment and plans the dose distribution (the dose distribution of the charged particle beam to be irradiated) at each position of the tumor 14. Specifically, the treatment planning device 90 creates a scan pattern for the tumor 14. The treatment planning device 90 transmits the created scan pattern to the control unit 7. In the scan pattern created by the treatment planning device 90, the scanning path and scanning speed of the charged particle beam B are planned.

[0029] When performing irradiation of a charged particle beam by a scanning method, the tumor 14 is virtually divided into a plurality of layers in the Z-axis direction, and in one layer, the charged particle beam is scanned and irradiated according to the scanning path determined in the treatment plan. After the irradiation of the charged particle beam in the one layer is completed, irradiation of the charged particle beam B in the next adjacent layer is performed.

[0030] When irradiating the charged particle beam B by a scanning method using the charged particle beam irradiation system 1 shown in FIG. 2, the quadrupole electromagnet 8 is set to the operating state (ON) so that the passing charged particle beam B converges.

[0031] Subsequently, the charged particle beam B is emitted from the accelerator 3. The emitted charged particle beam B is scanned according to the scan pattern determined in the treatment plan under the control of the scanning electromagnet 50. As a result, the charged particle beam B is irradiated while being scanned within the irradiation range in one layer set in the Z-axis direction with respect to the tumor 14. When the irradiation of one layer is completed, the charged particle beam B is irradiated to the next layer.

[0032] The charged particle beam irradiation image of the scanning electromagnet 50 according to the control of the control unit 7 will be described with reference to FIGS. 3(a) and (b). FIG. 3(a) shows an irradiated object virtually sliced into a plurality of layers in the depth direction, and FIG. 3(b) shows a scanning image of the charged particle beam in one layer viewed from the depth direction.

[0033] As shown in FIG. 3(a), the irradiated object is virtually sliced into a plurality of layers in the irradiation depth direction. In this example, from the deep (long range of the charged particle beam B) layer in order, layer L1, layer L2,... layer L n-1 , layer L n , layer L n+1 ,... layer L N-1 , layer L N and N layers are virtually sliced. Also, as shown in FIG. 3(b), the charged particle beam B draws a beam trajectory along the scan path TL, and in the case of continuous irradiation (line scanning or raster scanning), it is continuously irradiated along the scan path TL of layer L n , and in the case of spot scanning, it is irradiated to a plurality of irradiation spots of layer L n . The charged particle beam B is irradiated along the scan path TL1 extending in the X-axis direction, slightly shifted in the Y-axis direction along the scan path TL2, and irradiated along the adjacent scan path TL1. In this way, the charged particle beam B emitted from the irradiation unit 2 controlled by the control unit 7 moves on the scan path TL.

[0034] Next, with reference to FIGS. 4 to 7, the snow degreaser 30 will be described in detail. FIG. 4 is a schematic view showing a state in which the snow degreaser 30 is held by the holding unit 60. As shown in FIG. 4, the snow degreaser 30 is, as an example, a member having a rectangular plate shape. The snow degreaser 30 has a planar incident surface 30a and an exit surface 30b that extend in a direction orthogonal to the base axis AX. Since the snow degreaser 30 has a uniform thickness within the range where the charged particle beam B scans, it attenuates a certain amount of energy. The snow degreaser 30 can change the amount of energy adjustment of the charged particle beam B by changing the thickness, that is, the dimension between the incident surface 30a and the exit surface 30b. Thereby, the snow degreaser 30 can adjust the penumbra of the charged particle beam B by adjusting the expansion of the beam size of the charged particle beam B. The snow degreaser 30 is made of a material having a density close to that of water, such as polyethylene or acrylic, for example. Note that the snow degreaser 30 is intended to adjust the spread of the charged particle beam B.

[0035] The holding part 60 is provided on the irradiation part 2 and holds the snow grader 30 on the irradiation part 2 side. Since the holding part 60 is provided at the tip 9a of the irradiation nozzle 9, the snow grader 30 is arranged on the downstream side of all the components arranged inside the irradiation nozzle 9, that is, at a position closer to the patient 15. By being held by the holding part 60, the snow grader 30 is in a state of being provided on the irradiation part 2 side. The state of being provided on the irradiation part 2 side means, for example, not a state where the snow grader is arranged around the patient 15 or attached to the patient's bed 15, but a state where the snow grader 30 can also move as the irradiation part 2 moves. The holding part 60 can hold the snow grader 30 at a position closest to the patient 15 while holding the snow grader 30 on the irradiation part 2 side. Note that the position closest to the patient 15 means that the positions of the patient 15 and the snow grader 30 are, for example, closer than 30 cm. However, the distance between the snow grader 30 and the patient 15 may be appropriately changed according to the relationship with the surrounding environment and the like.

[0036] The holding part 60 has a pair of side wall parts 61 that support the outer peripheral edge part 30c of the snow toothed grader 30. The holding part 60 has a pair of side wall parts 62 that face the other outer peripheral edge part 30c (see Fig. 4(b)). These side wall parts 61, 62 extend downward from the support part 86. A wide member 87 is provided at the tip of the side wall parts 61, 62. Further, the holding part 60 can hold snow toothed graders 30 of multiple types of thicknesses. For example, the holding part 60 can hold a thin snow toothed grader 30A and can also hold a thick snow toothed grader 30B. When changing the thickness, the user takes out the thin snow toothed grader 30A from the holding part 60 and causes the thick snow toothed grader 30B to be held by the holding part 60. Thus, since the holding part 60 is configured to be able to hold snow toothed graders of multiple thicknesses, it can be said that it has a configuration in which the adjustment level of the penumbra, that is, the thickness, can be selected. Note that the holding part 60 may also serve as a bolus holder used, for example, in the wobbler irradiation method. Therefore, the holding part 60 may hold the snow toothed grader 30 with the bolus holder 66. Further, the holding part 60 may have a collimator holder 67 that holds a collimator below the bolus holder 66.

[0037] Here, the penumbra will be described with reference to FIG. 5. FIG. 5 is a graph showing the dose distribution when the charged particle beam B is irradiated by a scanning method in a predetermined plane perpendicular to the base axis AX. The horizontal axis indicates the position in a predetermined direction of the predetermined plane, and the vertical axis indicates the dose at each position. However, the graph shown in FIG. 5 is shown in a deformed manner for easy understanding. Among FIG. 5, the graph G1 shows the dose distribution of the charged particle beam B per pass. By scanning the charged particle beam B in the predetermined plane, a plurality of graphs G1 are formed in a state where they are shifted little by little at each position. The total dose distribution obtained by overlapping these graphs G1 is shown by the graph G2. The region indicated as W in FIG. 5 indicates the reference condition target width. The reference condition target width W indicates the width in the plane of the irradiated object to be irradiated. The width of the tumor 14 in the irradiation plane becomes the reference condition target width W. Within the range of the reference condition target width W, the graph G2 forms a flat region FE. The flat region FE is a region where the dose is substantially uniform and the difference in dose is within a predetermined range. On the other hand, the region outside the reference condition target width W becomes the penumbra P.

[0038] Here, the snow degrader 30 can suppress the expansion of the beam size of the charged particle beam B. Therefore, when suppressing the penumbra, the snow degrader 30 reduces the spread of the charged particle beam B (see graph G1a). As a result, the dose distribution changes as a whole, and the spread of the charged particle beam B also becomes smaller, so that the penumbra P can be suppressed (see graph G2a).

[0039] FIG. 6 is a graph showing simulation results related to the relationship between the spread of the charged particle beam B and the depth of the object. The graph shown in FIG. 6 is a graph obtained by setting the snow degrader 30 to an arbitrary thickness and calculating the spread of the charged particle beam B in water when the charged particle beam B is irradiated into water at each thickness using Monte Carlo simulation. The horizontal axis represents the distance from the surface of the water tank. This corresponds to the depth of the tumor 14 from the surface of the body of the patient 15. The vertical axis represents the spread of the charged particle beam B. The spread is a value calculated by a method called Gaussian fitting. Note that in FIG. 6, the distance between the snow degrader 30 and the water tank, that is, the thickness of the air layer through which the charged particle beam B emitted from the snow degrader 30 passes is set to 50 mm. This corresponds to the distance between the snow degrader 30 and the surface of the body of the patient 15.

[0040] As shown in FIG. 6, in a shallow region, the larger the thickness of the snow degrader 30, the more the spread of the charged particle beam B can be suppressed. On the other hand, in a deep region, the thinner the thickness of the snow degrader 30, the more the spread of the charged particle beam B can be suppressed. From such simulation results, the charged particle beam irradiation system 1 may be configured to be able to select the adjustment level (here, the thickness) of the penumbra of the snow degrader 30 based on the depth of the tumor 14 in the patient 15.

[0041] For example, when the tumor 14 is present in a shallow region E1a (less than 10 cm) in the body, the snow degrader 30 with a thickness of 13 cm may be selected. Also, when the tumor 14 is present in a deep region E2a (10 cm or more) in the body, the snow degrader 30 with a thickness of 0 cm or 4 cm may be selected. Or, when the tumor 14 is present in a shallow region E1b (less than 7 cm) in the body, the snow degrader 30 with a thickness of 12 cm may be selected. Also, when the tumor 14 is present in an intermediate region E2b (7 cm or more and less than 12 cm) in the body, the snow degrader 30 with a thickness of 8 cm may be selected. Also, when the tumor 14 is in a deep region E3b (12 cm or more) in the body, the snow degrader 30 with a thickness of 0 cm or 4 cm may be selected.

[0042] Figs. 7 and 8 are graphs showing simulation results when the thickness of the air layer is changed from Fig. 6. Fig. 7 shows the simulation results when the thickness of the air layer is 100 mm, and Fig. 8 shows the simulation results when the thickness of the air layer is 200 mm. As shown in Figs. 6 to 8, the relationship between the depth of the snowplow grader 30 at each thickness and the spread of the charged particle beam B changes depending on the thickness of the air layer. Therefore, the charged particle beam irradiation system 1 may be configured to be able to select the adjustment level (i.e., thickness) of the penumbra of the snowplow grader 30 based on the distance between the patient 15 and the irradiation unit 2 (see Fig. 2).

[0043] Next, with reference to Figs. 4 and 9, a configuration that enables selection of the adjustment level (i.e., thickness) of the penumbra of the snowplow grader 30 will be described. Fig. 9 is a block diagram showing a configuration for enabling selection of the adjustment level of the penumbra of the snowplow grader 30. As shown in Fig. 9, the charged particle beam irradiation system 1 includes the above-described control unit 7, an output unit 76, a reading unit 77, and an identification information detection unit 78. The control unit 7 further includes an information acquisition unit 70, a calculation unit 71, and a determination unit 72.

[0044] The information acquisition unit 70 acquires various information related to the irradiation of the charged particle beam B from the treatment planning device 90 and the storage unit 95. The information acquisition unit 70 can acquire information on the depth of the tumor 14 within the patient 15 and information on the distance between the patient 15 and the irradiation unit 2 (see FIG. 2) from the treatment plan created by the treatment planning device 90. The calculation unit 71 performs various calculations related to the selection of the adjustment level of the penumbra of the snow degrader 30. The calculation unit 71 selects the adjustment level, that is, the thickness, of the penumbra of the snow degrader 30 based on at least one of the information on the depth of the tumor 14 within the patient 15 and the information on the distance between the patient 15 and the irradiation unit 2 (see FIG. 2). The calculation unit 71 may select the thickness of the snow degrader 30 by comparing the acquired information with pre-prepared data as shown in FIGS. 6 to 8, for example. Alternatively, the calculation unit 71 may select an appropriate thickness of the snow degrader 30 by performing calculations based on the acquired information. However, the treatment planning device 90 may select an appropriate thickness of the snow degrader 30, and in this case, the information acquisition unit 70 acquires the information on the thickness of the snow degrader 30. The determination unit 72 determines whether the correct snow degrader 30 is arranged in the holding unit 60.

[0045] The output unit 76 outputs various information. The output unit 76 is composed of a monitor, a speaker, etc. The output unit 76 may output, for example, information on the thickness of the selected snow degrader 30 to the user. Thereby, the user can arrange the snow degrader 30 having the thickness selected by the control unit 7 in the holding unit 60.

[0046] Here, the reading unit 77, the identification information detection unit 78, and the determination unit 72 are configured as a detection unit 80 that detects that an incorrect snow degrader 30 is arranged in the holding unit 60.

[0047] Specifically, the reading unit 77 reads information regarding the thickness from the thickness information holding unit 81 (see Fig. 4(a)) provided for each snow grader 30. The thickness information holding unit 81 is not particularly limited as long as it can hold information regarding the thickness, and may be constituted by, for example, a barcode. In this case, the reading unit 77 is constituted by a barcode reader. Alternatively, the thickness information holding unit 81 may be constituted by a QR code (registered trademark), and the reading unit 77 may be constituted by a QR code reader. The thickness information holding unit 81 may be constituted by a means for holding temporal information, and the reading unit 77 may be constituted by a device for reading the magnetic information.

[0048] The identification information detection unit 78 detects information that can identify the snow grader 30 held in the holding unit 60. For example, the identification information detection unit 78 may detect, as identification information, a signal from a predetermined detection means provided in the holding unit 60. Such a detection means may transmit, to the identification information detection unit 78, a signal indicating what thickness the held snow grader 30 is when the snow grader 30 is held by the holding unit 60.

[0049] The determination unit 72 determines whether the thickness selected by the calculation unit 71 matches the thickness read by the reading unit 77. If they do not match, the determination unit 72 outputs, via the output unit 76, information indicating that an incorrect snow grader 30 is placed. If they match, the determination unit 72 outputs, via the output unit 76, information indicating that the correct snow grader 30 is placed.

[0050] The determination unit 72 compares the thickness information read by the reading unit 77 with the thickness selected by the calculation unit 71. In this case, the user can make a pre-error determination by reading the thickness information with the reading unit 77 before placing the snow grader 30 in the holding unit 60. Further, the determination unit 72 specifies the thickness of the snow grader 30 held in the holding unit 60 from the identification information detected by the identification information detection unit 78, and compares the thickness with the thickness selected by the calculation unit 71. In this case, the user can make an error determination without performing a reading operation with the reading unit 77.

[0051] Next, the charged particle beam irradiation method according to the present embodiment will be described with reference to FIG. 10. FIG. 10 is a process diagram showing the content of the charged particle beam irradiation method according to the present embodiment. As shown in FIG. 10, a step S10 of selecting the adjustment level (i.e., thickness) of the penumbra of the snow degrader 30 is executed based on at least one of the depth of the tumor 14 in the body of the patient 15 and the distance between the patient 15 and the irradiation unit 2. Next, a step S20 of arranging the snow degrader 30 selected in the step S10 in the holding unit 60 is executed. Next, a step S30 of determining, using the detection unit 80 (see FIG. 9), whether an incorrect snow degrader 30 is arranged in the holding unit 60 is executed. When using the reading unit 77, the determination step S30 is executed at a stage prior to the step S20. Next, when the correct snow degrader 30 is arranged, a step S40 of irradiating the tumor 14 with the charged particle beam B from the irradiation unit 2 is executed.

[0052] Next, the operation and effects of the charged particle beam irradiation system 1 and the charged particle beam irradiation method according to the present embodiment will be described.

[0053] The charged particle beam irradiation system 1 according to this embodiment includes an irradiation unit 2 that irradiates the tumor 14 with the charged particle beam B by scanning the charged particle beam B with the scanning electromagnet 50, and a snow degrader 30 that adjusts the penumbra of the charged particle beam B. Therefore, when the snow degrader 30 adjusts the penumbra of the charged particle beam B, it is possible to suppress the irradiation of the charged particle beam B outside the tumor 14 when the irradiation unit 2 irradiates near the boundary of the tumor 14. Here, a holding unit 60 that holds the snow degrader 30 is provided in the irradiation unit 2. Therefore, it is possible to easily align the position between the charged particle beam B irradiated to the tumor 14 and the snow degrader 30. Therefore, the irradiation unit 2 can irradiate the tumor 14 with the charged particle beam B in a state where the penumbra is adjusted at an appropriate position by the snow degrader 30. For example, when the snow degrader is provided on the bed side of the patient 15, the operator has to align the snow degrader while considering the positional relationship between the patient 15 and the irradiation unit 2. However, since the patient 15 is difficult to see, there is a problem that it is difficult to perform the alignment. On the other hand, in this embodiment, since it is only necessary to hold the snow degrader 30 by the holding unit 60, the alignment is easy. As described above, the irradiation unit 2 can appropriately irradiate the tumor 14 with the charged particle beam B.

[0054] The holding unit 60 may be provided at the tip 9a of the irradiation unit 2. In this case, the snow degrader 30 can adjust the penumbra at a position close to the patient 15. Therefore, after the snow degrader 30 adjusts the penumbra, the charged particle beam B is quickly irradiated to the tumor 14 before the spread becomes large.

[0055] The charged particle beam irradiation system 1 may be configured to be able to select the adjustment level of the penumbra of the snow degrader 30 based on the depth of the tumor 14 in the body of the patient 15. In this case, the snow degrader 30 can adjust the penumbra at an appropriate penumbra adjustment level according to the depth of the tumor 14 in the body of the patient 15.

[0056] The charged particle beam irradiation system 1 may be configured to be able to select the adjustment level of the penumbra of the snow degrader 30 based on the distance between the patient 15 and the irradiation unit 2. In this case, the snow degrader 30 can adjust the penumbra at an appropriate penumbra adjustment level according to the distance between the patient 15 and the irradiation unit 2.

[0057] The charged particle beam irradiation system 1 may further include a detection unit 80 that detects that an incorrect snow degrader 30 is arranged with respect to the holding unit 60. In this case, it is possible to suppress the penumbra adjustment from being performed with the snow degrader 30 related to an inappropriate adjustment level.

[0058] The charged particle beam irradiation method according to the present embodiment is a charged particle beam irradiation method for irradiating a tumor 14 in the body of a patient 15 with a charged particle beam B, and includes a step S10 of selecting an adjustment level of the penumbra of a snow degrader 30 that adjusts the penumbra of the charged particle beam B based on the depth of the tumor 14 in the body of the patient 15, a step S20 of arranging the selected snow degrader 30 with respect to the charged particle beam B, and a step S40 of irradiating the tumor 14 with the charged particle beam B by scanning the charged particle beam B with a scanning electromagnet 50.

[0059] According to this charged particle beam irradiation method, the snow degrader 30 can adjust the penumbra at an appropriate penumbra adjustment level according to the depth of the tumor 14 in the body of the patient 15. From the above, the tumor 14 can be appropriately irradiated with the charged particle beam B.

[0060] When treating cases (for example, head and neck cases) that generally use low-energy proton beams in large hospitals with a large number of patients, the treatment using an adjustment member (snow degrader) as in this embodiment has good beam usage efficiency. Since there is a usage limit of proton beam for each facility, if the efficiency is high, the number of treated patients can be increased compared to the control with the conventional ESS.

[0061] The snow degreaser 30 may have an adjustment level according to the distance between the patient 15 and the irradiation unit 2. In this case, the snow degreaser 30 can adjust the penumbra at an adjustment level of the penumbra according to the distance between the patient 15 and the irradiation unit 2.

[0062] The charged particle beam irradiation method further includes a step S10 of selecting an adjustment level based on the depth of the tumor 14 in the body of the patient 15, and in the step S30 of arranging the snow degreaser 30, the selected snow degreaser 30 may be arranged. In this case, the snow degreaser 30 can adjust the penumbra at an appropriate adjustment level of the penumbra according to the depth of the tumor 14 in the body of the patient 15.

[0063] The charged particle beam irradiation method further includes a step S10 of selecting an adjustment level based on the distance between the patient 15 and the irradiation unit 2, and in the step S30 of arranging the snow degreaser 30, the selected snow degreaser 30 may be arranged. In this case, the snow degreaser 30 can adjust the penumbra at an appropriate adjustment level of the penumbra according to the distance between the patient 15 and the irradiation unit 2.

[0064] For example, as a comparative example, a charged particle beam irradiation system that does not have a snow degreaser 30 at the tip 9a of the irradiation unit 2 will be described. In this case, the charged particle beam irradiation system controls the energy of the charged particle beam B with an energy adjustment device (ESS: Energy Selection System) upstream of the beam transport line 21. The energy adjustment device needs to cause a large energy loss with the energy degreaser 20 in order to change the depth of penetration of the charged particle beam B in the patient's body. Therefore, the charged particle beam B will spread in the direction of motion. As the beam having a spread in the direction of motion is transported by the energy adjustment device, the beam size expands due to drift as the charged particle beam B advances downstream of the beam transport line 21, and the penumbra also expands.

[0065] On the other hand, in the charged particle beam irradiation system 1 according to the present embodiment, the snow degreaser 30 adjusts the penumbra of the charged particle beam B immediately before the patient 15. Therefore, by suppressing the energy loss in the upstream energy degreaser 20 to a small level and increasing the energy loss for penumbra adjustment in the snow degreaser 30, it is possible to irradiate the patient 15 while suppressing the expansion of the beam size, and the penumbra can be suppressed. Further, since the thickness of the snow degreaser 30 can be selected, the adjustment level of the penumbra of the snow degreaser 30 can be appropriately adjusted according to the depth of the tumor 14 and the distance between the patient 15 and the irradiation unit 2.

[0066] The present invention is not limited to the above-described embodiments.

[0067] For example, although the snow degreaser is exemplified as an adjustment member for adjusting the penumbra, other members may be adopted as long as they can adjust the penumbra. For example, a collimator or a multi-leaf collimator may be provided at the position of the holding unit 60, that is, immediately before the patient 15, and the penumbra may be adjusted by the multi-leaf collimator. The multi-leaf collimator can adjust the penumbra by blocking the beam of the charged particle beam B at a position corresponding to the boundary of the tumor 14. The adjustment level can be adjusted by the aperture diameter. If the aperture diameter is opened wide (that is, a margin is provided for the outer diameter of the tumor), the penumbra portion is not blocked, and if the aperture diameter is opened small (fitted to the outer diameter of the tumor), the penumbra can be blocked. In this case, by adjusting the penumbra with a multi-leaf collimator in the immediate vicinity (for example, 30 cm or less) of the patient 15, the charged particle beam B can be irradiated to the tumor 14 before the beam size of the charged particle beam B is expanded.

[0068] The position where the holding unit for holding the multi-leaf collimator is provided does not necessarily have to be the tip of the irradiation unit, and may be inside the irradiation unit.

Description of Reference Numerals

[0069] 1... Charged particle beam irradiation system, 2... Irradiation unit, 14... Tumor (irradiated object), 15... Patient (object), 30... Snow degreaser (adjusting member), 50... Scanning electromagnet, 60... Holding unit, 80... Detection unit.

Claims

1. A charged particle beam irradiation method using a charged particle beam irradiation system for irradiating a radiation target in an object with a charged particle beam, wherein the charged particle beam irradiation system includes: an irradiation unit that irradiates the radiation target with the charged particle beam by scanning the charged particle beam with a scanning electromagnet; an adjustment member that adjusts the penumbra of the scanned charged particle beam; a holding unit provided in the irradiation unit for holding the adjustment member; a calculation unit that performs calculations; and the adjustment member is a snout degrader having a predetermined thickness and adjusting the energy of the charged particle beam passing therethrough by reducing the energy of the charged particle beam; and the calculation unit selects the thickness of the snout degrader based on the depth of the object from a simulation result related to the relationship between the thickness of the snout degrader, the spread of the charged particle beam, and the depth of the object. A charged particle beam irradiation method.

2. The charged particle beam irradiation method according to claim 1, wherein the holding unit is provided at a tip of the irradiation unit.

3. The charged particle beam irradiation system according to claim 1 or 2, further comprising a detection unit that detects that an incorrect adjustment member is arranged with respect to the holding unit. A charged particle beam irradiation method.

4. A charged particle beam irradiation system for irradiating a radiation target in an object with a charged particle beam, including an irradiation unit that irradiates the radiation target with the charged particle beam by scanning the charged particle beam with a scanning electromagnet; an adjustment member that adjusts the penumbra of the scanned charged particle beam; a holding unit provided in the irradiation unit for holding the adjustment member; and a calculation unit that performs calculations, wherein the adjustment member is a snout degrader having a predetermined thickness and adjusting the energy of the charged particle beam passing therethrough by reducing the energy of the charged particle beam; the holding unit is capable of holding the snout degrader whose thickness is adjusted to adjust the penumbra of the scanned charged particle beam; and the calculation unit selects the thickness of the snout degrader based on the depth of the object from a simulation result related to the relationship between the thickness of the snout degrader, the spread of the charged particle beam, and the depth of the object. A charged particle beam irradiation system. ​

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