Particle beam therapy device

Abstract

The present invention provides a particle beam therapy device that can reduce the effects of particle beam bending caused by the magnetic field of the magnetic resonance imaging unit. [Solution] The particle beam therapy apparatus 1 comprises an irradiation unit 2 that irradiates the tumor 14 of patient 15 with particle beam B, and an MRI device 60 that acquires an image of the tumor 14 of patient 15 using a magnetic field MF. Therefore, the irradiation unit 2 can irradiate the tumor 14 of patient 15 with particle beam B based on the image acquired by the MRI device 60. Here, the particle beam therapy apparatus 1 also comprises a correction unit 70 that corrects the irradiation pattern of particle beam B by the irradiation unit 2 to the tumor 14 of patient 15 according to the amount of bending of particle beam B due to the magnetic field MF of the MRI device 60. Therefore, even if the particle beam B is bent due to the influence of the magnetic field MF of the MRI device 60, the correction unit 70 corrects the irradiation pattern to match the amount of bending.

Description

Technical Field

[0001] The present invention relates to a particle beam therapy apparatus.

Background Art

[0002] Conventionally, as a particle beam therapy apparatus that performs treatment by irradiating a diseased part of a patient with a particle beam, for example, an apparatus described in Patent Document 1 is known. In the particle beam therapy apparatus described in Patent Document 1, a particle beam is irradiated from an irradiation unit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, as a method for acquiring an image of a treatment target object, it is known to use magnetic resonance imaging (MRI) that acquires an image by a magnetic field. By incorporating a magnetic resonance imaging unit into a particle beam therapy apparatus, it becomes possible to grasp the state of an irradiated object irradiated with a particle beam based on an acquired image. However, due to the influence of the magnetic field of the magnetic resonance imaging unit, the particle beam irradiated from the irradiation unit may bend.

[0005] Therefore, an object of the present invention is to provide a particle beam therapy apparatus capable of reducing the influence caused by bending of a particle beam due to a magnetic field of a magnetic resonance imaging unit.

Means for Solving the Problems

[0006] A particle beam therapy apparatus according to one aspect of the present invention comprises an irradiation unit that irradiates a target object with a particle beam, a magnetic resonance imaging unit that acquires an image of the target object using a magnetic field, and a correction unit that corrects the irradiation pattern of the particle beam by the irradiation unit to the target object according to the amount of bending of the particle beam by the magnetic field of the magnetic resonance imaging unit.

[0007] The particle beam therapy device comprises an irradiation unit that irradiates a target object with a particle beam, and a magnetic resonance imaging unit that acquires an image of the target object using a magnetic field. Therefore, the irradiation unit can irradiate the target object with a particle beam based on the image acquired by the magnetic resonance imaging unit. The particle beam therapy device also includes a correction unit that corrects the irradiation pattern of the particle beam by the irradiation unit to the target object according to the amount of bending of the particle beam caused by the magnetic field of the magnetic resonance imaging unit. Therefore, even if the particle beam is bent due to the influence of the magnetic field of the magnetic resonance imaging unit, the correction unit corrects the irradiation pattern to match the amount of bending. Thus, the effect of particle beam bending due to the magnetic field of the magnetic resonance imaging unit can be reduced.

[0008] The correction unit may have an irradiation unit position adjustment unit that can adjust the position of the irradiation unit. In this case, the irradiation unit position adjustment unit adjusts the position of the irradiation unit according to the amount of bending of the particle beam, so that the particle beam can be irradiated onto the object to be irradiated from a position that eliminates the bending of the particle beam.

[0009] The correction unit may include a magnetic field adjustment unit that adjusts the magnetic field of the magnet in the irradiation unit. In this case, the magnetic field adjustment unit adjusts the magnetic field of the magnet in the irradiation unit according to the amount of bending of the particle beam, thereby correcting the tilt to eliminate the bending of the particle beam and irradiating the object to be irradiated with the particle beam.

[0010] The correction unit may have an irradiated object fixing unit that can fix the irradiated object and adjust its position relative to the irradiation unit. In this case, the irradiated object fixing unit can move the irradiated object according to the amount of bending of the particle beam, so that the particle beam can be irradiated to the irradiated object at a position where the bending can be eliminated.

[0011] The irradiation unit may be configured to rotate around the object to be irradiated. In this case, the correction unit can correct the irradiation pattern according to the amount of particle beam bending at the rotational position of the irradiation unit.

[0012] The irradiation unit may be configured as a fixed irradiation port. In this case, since the particle beam is irradiated from only one side, correction by the correction unit becomes easier.

[0013] The correction unit may correct the irradiation pattern based on the kinetic energy of the particle beam. The amount of bending changes according to the kinetic energy of the particle beam. Therefore, the correction unit can correct the irradiation pattern to an appropriate one according to this change.

[0014] The magnetic resonance imaging unit has a coil that generates a magnetic field, and the central axis of the coil may extend in a direction perpendicular to the base axis of the particle beam irradiated from the irradiation unit. In this case, the particle beam bends in a direction perpendicular to the central axis of the coil and the base axis. The correction unit corrects for this bending. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a particle beam therapy apparatus that can reduce the effects of particle beam bending caused by the magnetic field of the magnetic resonance imaging unit. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram showing a particle beam therapy apparatus according to one embodiment of the present invention. [Figure 2] Figure 1 is a schematic diagram of the area around the irradiation section of the particle beam therapy device. [Figure 3] This diagram shows the layers set for the tumor. [Figure 4] This is a conceptual diagram showing the irradiation process as viewed from the Y-axis direction when the position of the irradiation unit is not corrected by the correction unit (reference state). [Figure 5] This is a conceptual diagram showing the irradiation of the irradiation unit after position adjustment by the irradiation unit position adjustment unit. [Figure 6]It is a conceptual diagram showing the state of irradiation of the irradiation unit after position adjustment by the irradiation unit position adjustment unit. [Figure 7] It is a conceptual diagram showing the state of irradiation of the irradiation unit after magnetic field adjustment by the magnetic field adjustment unit. [Figure 8] It is a conceptual diagram showing the state of irradiation of the irradiation unit when the irradiated object fixing unit is performing position adjustment.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, a particle beam therapy apparatus 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.

[0018] FIG. 1 is a schematic configuration diagram showing a particle beam therapy apparatus 1 according to an embodiment of the present invention. The particle beam therapy apparatus 1 is a system used for cancer treatment and the like by radiation therapy. The particle beam therapy apparatus 1 includes an accelerator 3 that accelerates charged particles generated by an ion source device and emits them as a particle beam B, an irradiation unit 2 that irradiates the particle beam B to a patient 15, and a beam transport line 20 that transports the particle beam B emitted from the accelerator 3 to the irradiation unit 2. The irradiation unit 2 is attached to a rotating gantry 17 (gantry structure) provided so as to surround a treatment table 6. The irradiation unit 2 is rotatable around the treatment table 6, which is an arrangement unit for arranging the patient 15, with the central axis CL as the rotation center by the rotating gantry 17. Further, the particle beam therapy apparatus 1 includes an MRI device 60 (MRI: Magnetic Resonance Imaging, magnetic resonance imaging unit) that acquires an image of the patient 15 by a magnetic field. The more detailed configurations of the accelerator 3, the irradiation unit 2, the beam transport line 20, and the MRI device 60 will be described later.

[0019] The beam transport line 20 includes a beam duct 21 for transporting particle beam B, electromagnets 22 such as quadrupole electromagnets for focusing particle beam B, and deflection electromagnets 23A, 23B, 23C, and 22D for bending the trajectory of particle beam B. Deflection electromagnets 23A and 23B bend the trajectory of particle beam B, which is traveling from accelerator 3 to rotating gantry 17, toward the outer periphery relative to the central axis CL. Deflection electromagnets 23C and 23D, at positions spaced outward from the central axis CL, bend the trajectory of particle beam B, which is traveling toward the outer periphery relative to the central axis CL, toward the inner periphery. Furthermore, deflection electromagnet 23D bends the trajectory of particle beam B so that it is traveling in a direction perpendicular to the central axis CL, guiding it toward the irradiation section 2.

[0020] Figure 2 is a schematic diagram of the area near the irradiation section of the particle beam therapy device 1 shown in Figure 1. In the following explanation, the terms "X-axis direction," "Y-axis direction," and "Z-axis direction" will be used. The "Z-axis direction" is the direction in which the base axis AX of particle beam B extends, and is the direction of irradiation depth of particle beam B. The "base axis AX" is the irradiation axis of particle beam B when it is not deflected by the scanning electromagnet 50 described later. Figure 2 shows how particle beam B is irradiated along the base axis AX. The "X-axis direction" is one direction in a plane perpendicular to the Z-axis direction. The "Y-axis direction" is the direction perpendicular to the X-axis direction in a plane perpendicular to the Z-axis direction.

[0021] First, with reference to Figure 2, the schematic configuration of the particle beam therapy apparatus 1 according to this embodiment will be described. The particle beam therapy apparatus 1 is an irradiation device that uses a scanning method. The scanning method is not particularly limited, and line scanning, raster scanning, spot scanning, etc., may be employed. As shown in Figure 2, the particle beam therapy apparatus 1 comprises an accelerator 3, an irradiation unit 2, a beam transport line 20, a control unit 7, an MRI device 60, a treatment planning device 90, and a storage unit 95.

[0022] Accelerator 3 is a device that accelerates charged particles and emits a particle beam B with a preset energy. Examples of accelerator 3 include cyclotrons and synchrocyclotrons. This accelerator 3 is connected to a control unit 7, which controls the supplied current. The particle beam B generated in accelerator 3 is transported to the irradiation unit 2 by a beam transport line 20. The beam transport line 20 connects accelerator 3 and irradiation unit 2, and transports the particle beam B emitted from accelerator 3 to irradiation unit 2.

[0023] The irradiation unit 2 irradiates the tumor (target) 14 in the patient's body 15 with particle beam B. Particle beam B is a particle accelerated to high speed, such as a proton beam, heavy particle (heavy ion) beam, or electron beam. Specifically, the irradiation unit 2 is a device that irradiates the tumor 14 with 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 20. The irradiation unit 2 is equipped with a scanning electromagnet 50, a quadrupole electromagnet 8, a profile monitor 11, a dose monitor 12, position monitors 13a, 13b, a collimator 40, and a degrader 30. The scanning electromagnet 50, each monitor 11, 12, 13a, 13b, the quadrupole electromagnet 8, and the degrader 30 are housed in an irradiation nozzle 9, which serves as a housing. In this way, the irradiation unit 2 is constructed by housing each main component in the irradiation nozzle 9. Note that the quadrupole electromagnet 8, profile monitor 11, dose monitor 12, position monitors 13a and 13b, and degrader 30 may be omitted.

[0024] As scanning electromagnets 50, an X-axis scanning electromagnet 50A and a Y-axis scanning electromagnet 50B are used. Each X-axis scanning electromagnet 50A and Y-axis scanning electromagnet 50B consists of a pair of electromagnets, and the magnetic field between the pair of electromagnets is changed in accordance with the current supplied from the control unit 7, scanning the particle beam B passing between the electromagnets. The X-axis scanning electromagnet 50A scans the particle beam B in the X-axis direction, and the Y-axis scanning electromagnet 50B scans the particle beam B in the Y-axis direction. These scanning electromagnets 50 are located on the base axis AX and are arranged in this order downstream of the particle beam B from the accelerator 3. The scanning electromagnets 50 scan the particle beam B so that the particle beam B is irradiated according to a scan pattern pre-planned by the treatment planning device 90. How the scanning electromagnets 50 are controlled will be described later.

[0025] The quadrupole electromagnet 8 includes a quadrupole electromagnet 8a in the X-axis direction and a quadrupole electromagnet 8b in the Y-axis direction. The quadrupole electromagnet 8a in the X-axis direction and the quadrupole electromagnet 8b in the Y-axis direction focus the particle beam B according to the current supplied from the control unit 7. The quadrupole electromagnet 8a in the X-axis direction focuses the particle beam B in the X-axis direction, and the quadrupole electromagnet 8b in the Y-axis direction focuses the particle beam B in the Y-axis direction. By changing the amount of focusing (amount of aspiration) by changing the current supplied to the quadrupole electromagnet 8, the beam size of the particle beam B can be changed. The quadrupole electromagnet 8 is located on the base axis AX and is arranged in this order between the accelerator 3 and the scanning electromagnet 50. The beam size is the size of the particle beam B in the XY plane. The beam shape is the shape of the particle beam B in the XY plane.

[0026] The profile monitor 11 detects the beam shape and position of particle beam B for initial alignment. The profile monitor 11 is located on the base axis AX, between the quadrupole electromagnet 8 and the scanning electromagnet 50. The dose monitor 12 detects the dose of particle beam B. The dose monitor 12 is located on the base axis AX, downstream of the scanning electromagnet 50. The position monitors 13a and 13b detect and monitor the beam shape and position of particle beam B. The position monitors 13a and 13b are located on the base axis AX, downstream of particle beam B from the dose monitor 12. Each monitor 11, 12, 13a, and 13b outputs the detected results to the control unit 7.

[0027] The degrader 30 reduces the intensity of the passing particle beam B to fine-tune its intensity. In this embodiment, the degrader 30 is located at the tip 9a of the irradiation nozzle 9. The tip 9a of the irradiation nozzle 9 is the downstream end of the particle beam B.

[0028] The collimator 40 is located at least downstream of the scanning electromagnet 50 of the particle beam B and is a component that shields a portion of the particle beam B and allows a portion to pass through. Here, the collimator 40 is located downstream of the position monitors 13a and 13b. The collimator 40 is connected to a collimator drive unit 51 that moves the collimator 40.

[0029] The control unit 7 is composed of, for example, a CPU, ROM, and RAM. Based on the detection results output from each of the monitors 11, 12, 13a, and 13b, the control unit 7 controls the accelerator 3, the scanning electromagnet 50, the quadrupole electromagnet 8, and the collimator drive unit 51.

[0030] Furthermore, the control unit 7 of the particle beam therapy apparatus 1 is connected to a treatment planning apparatus 90 that plans the treatment for particle beam therapy, and a storage unit 95 that stores various data. Before treatment, the treatment planning apparatus 90 measures the tumor 14 of the patient 15 using CT or the like, and plans the dose distribution (dose distribution of the particle beam to be irradiated) at each location of the tumor 14. Specifically, the treatment planning apparatus 90 creates a scan pattern for the tumor 14. The treatment planning apparatus 90 transmits the created scan pattern to the control unit 7. The scan pattern created by the treatment planning apparatus 90 plans what kind of scanning path the particle beam B will trace and at what scanning speed.

[0031] When performing particle beam irradiation using the scanning method, the tumor 14 is virtually divided into multiple layers in the Z-axis direction, and the particle beam is irradiated in one layer by scanning according to the scanning path defined in the treatment plan. After the irradiation of the particle beam in that layer is completed, the particle beam B is irradiated in the adjacent next layer.

[0032] When irradiating with particle beam B using the scanning method with the particle beam therapy device 1 shown in Figure 2, the quadrupole electromagnet 8 is activated (ON) so that the passing particle beam B is focused.

[0033] Next, particle beam B is emitted from accelerator 3. The emitted particle beam B is scanned according to the scan pattern defined in the treatment plan by the control of the scanning electromagnet 50. As a result, particle beam B is irradiated to the tumor 14 while scanning within the irradiation range of one layer set in the Z-axis direction. Once irradiation of one layer is complete, particle beam B is irradiated to the next layer.

[0034] The particle beam irradiation image of the scanning electromagnet 50 in response to the control of the control unit 7 will be explained with reference to Figures 3(a) and (b). Figure 3(a) shows the irradiated object virtually sliced ​​into multiple layers in the depth direction, and Figure 3(b) shows the scanning image of the particle beam in one layer as viewed from the depth direction.

[0035] As shown in Figure 3(a), the irradiated object is virtually sliced ​​into multiple layers in the depth direction of irradiation. In this example, the layers are named Layer L1, Layer L2, ... Layer L, starting from the deepest layer (where the range of particle beam B is long). n-1 Layer L n Layer L n+1 ...Layer L N-1 Layer L N It is virtually sliced ​​into N layers. Also, as shown in Figure 3(b), the particle beam B traces a beam trajectory along the scanning path TL, and in the case of continuous irradiation (line scanning or raster scanning), it is sliced ​​into layer L n The light is continuously irradiated along the scanning path TL, and in the case of spot scanning, layer L n The particle beam B is irradiated to multiple irradiation spots. The particle beam B is irradiated along the scanning path TL1 extending in the X direction, shifts slightly in the Y direction along the scanning path TL2, and irradiates along the adjacent scanning path TL1. In this way, the particle beam B emitted from the irradiation unit 2 controlled by the control unit 7 moves along the scanning path TL.

[0036] Next, the MRI device 60 will be described with reference to Figure 1. The MRI device 60 is mounted on the rotating gantry 17 together with the irradiation unit 2. The MRI device 60 is rotatable around the treatment table 6 with its central axis CL as the center of rotation by the rotating gantry 17. The MRI device 60 is equipped with multiple (a pair in Figure 1) coils 61, which are sources of magnetic field MF. The MRI device 60 is a passive shield type device that returns the magnetic flux generated by the coils 61 with an iron yoke 62. The MRI device 60 is equipped with gradient magnetic field coils and a high-frequency transmitting / receiving system (not shown) for causing magnetic resonance phenomena and collecting the resulting signals. The MRI device 60 is also equipped with a processing unit 63 (see Figure 2) that controls the energization of the gradient magnetic field coils and generates an MRI image from the detected values ​​of the high-frequency transmitting / receiving system and outputs it to the control unit 7.

[0037] The pair of coils 61 have an annular shape with a central axis CL. The pair of coils 61 are spaced apart from each other in the direction in which the central axis CL extends, with the irradiation unit 2 in between. As a result, the magnetic field generated by the MRI device 60 is parallel to the direction in which the central axis CL extends, that is, perpendicular to the base axis AX of the particle beam B. At this time, the central axis CL of the coil 61 extends in a direction perpendicular to the base axis AX of the particle beam B irradiated from the irradiation unit 2. As a result, the patient 15 is placed on the treatment table 6 so that the tumor 14 (see Figure 2) is within the uniform magnetic field MF generated by the coils 61 of the MRI device 60, and an MRI image of the area around the tumor 14 is taken.

[0038] The yoke 62 of the MRI apparatus 60 comprises a shielding member 66 and a return yoke portion 67. The shielding member 66 is a cylindrical member centered on a central axis CL. An opening 68 is formed in the shielding member 66 at a position radially opposite to the irradiation unit 2. The opening 68 allows the particle beam B irradiated from the irradiation unit 2 to pass through and guide it into the interior of the shielding member 66. The return yoke portion 67 is a member that extends inside the shielding member 66 at the rear of the rotating gantry 17 in a direction perpendicular to the central axis CL and is connected to the inner circumferential surface of the shielding member 66. This return yoke portion 67 and the shielding member 66 form a magnetic flux passage path, i.e., a magnetic circuit.

[0039] Next, with reference to Figure 4, the effect of the magnetic field MF of the MRI apparatus 60 on the particle beam B irradiated from the irradiation unit 2 will be explained. Figure 4 is a conceptual diagram of the irradiation process viewed from the Y-axis direction when the position of the irradiation unit 2 is not corrected by the correction unit 70 described later (reference state). In Figure 4, the irradiation unit 2 is shown by a solid line when it is positioned at its uppermost position. The position of the scanning electromagnet 50 at this time will be called "position PG1". In the following explanation, the XYZ axis coordinates will be fixed based on the state of the irradiation unit 2 shown by the solid line in Figure 4 as the reference state. The position of the scanning electromagnet 50 (shown by a dashed line) when it is rotated 180° from position PG1, i.e., when the irradiation unit 2 is positioned at its lowermost position, will be called "position PG2". In Figure 4, an isocenter AC is set. The isocenter AC is a center point set on the central axis CL of the rotating gantry 17. The isocenter AC is the point where the central axis CL and the base axis AX intersect. The base axis AX at this time will be called the reference line SL1. Furthermore, the line perpendicular to the reference line SL1 and passing through the isocenter AC is defined as the reference line SL2.

[0040] Here, assuming that the magnetic field MF of the MRI device 60 is absent, the irradiation range of particle beam B scanned by the scanning electromagnet 50 at position PG1 is defined as "VRE1". The irradiation range of particle beam B scanned by the scanning electromagnet 50 at position PG2 is defined as "VRE2". In this case, irradiation ranges VRE1 and VRE2 are the same range along the reference line SL2. Therefore, the size of the irradiation field where the two overlap is "W1".

[0041] However, if the magnetic field MF of the MRI device 60 is present, the particle beam B is deflected to the positive side in the X-axis direction due to the influence of the magnetic field MF. The irradiation range of the deflected particle beam B scanned by the scanning electromagnet 50 at position PG1 is defined as "RE1". The irradiation range of the deflected particle beam B scanned by the scanning electromagnet 50 at position PG2 is defined as "RE2". In this case, the irradiation range RE1 will have a shape that is deflected to the positive side in the X-axis direction. The irradiation range RE2 will have a shape that is deflected to the negative side in the X-axis direction. At this time, the irradiation ranges RE1 and RE2 will be offset from each other on the reference line SL2. Therefore, the size of the irradiation field where the two overlap will be "W2", which is smaller than the size W1.

[0042] In contrast, the particle beam therapy device 1 includes a correction unit 70 that corrects the irradiation pattern of the particle beam B by the irradiation unit 2 to the tumor 14 according to the amount of bending of the particle beam B due to the magnetic field MF of the MRI device 60. The amount of bending of the particle beam B can be calculated using the set kinetic energy of the particle beam B and the designed intensity of the magnetic field MF. In the example shown in Figure 5, the correction unit 70 has an irradiation unit position adjustment unit 71 that can adjust the position of the irradiation unit 2. Figure 5(a) is a conceptual diagram of the irradiation of the irradiation unit 2 after position adjustment by the irradiation unit position adjustment unit 71, viewed from the Y-axis direction. Figure 5(b) is a conceptual diagram of the irradiation of the irradiation unit 2 after position adjustment by the irradiation unit position adjustment unit 71, viewed from the X-axis direction.

[0043] As shown in Figure 5, the irradiation unit position adjustment unit 71 shifts the irradiation unit 2 so that the position of the base axis AX is shifted relative to the reference line SL1 by the amount of bending of the particle beam B. The irradiation unit position adjustment unit 71 shifts the irradiation unit 2 to the negative side in the X-axis direction so that the irradiation range RE1 is shifted to the negative side in the X-axis direction relative to the reference line SL1. Then, the irradiation unit 2 is shifted to the positive side in the X-axis direction so that the irradiation range RE2 is shifted to the positive side in the X-axis direction relative to the reference line SL1. At this time, the irradiation range RE1 and the irradiation range RE2 are approximately the same range on the reference line SL2. Therefore, the size of the irradiation field where the two overlap can be increased.

[0044] The correction unit 70 may correct the irradiation pattern based on the kinetic energy of particle beam B. For example, the irradiation unit position adjustment unit 71 of the correction unit 70 adjusts the shift amount of the irradiation unit 2 so that irradiation range RE1 and irradiation range RE2 are in the same range on the reference line SL2. If the kinetic energy of particle beam B changes, the irradiation unit position adjustment unit 71 may change the shift amount of the irradiation unit 2 to match the changed kinetic energy.

[0045] The irradiation unit position adjustment unit 71 may adjust its position to tilt the irradiation unit 2. Figure 6(a) is a conceptual diagram of the irradiation of the irradiation unit 2 after position adjustment by the irradiation unit position adjustment unit 71, viewed from the Y-axis direction. Figure 6(b) is a conceptual diagram of the irradiation of the irradiation unit 2 after position adjustment by the irradiation unit position adjustment unit 71, viewed from the X-axis direction.

[0046] As shown in Figure 6, the irradiation unit position adjustment unit 71 tilts the irradiation unit 2 so that the position of the base axis AX is tilted relative to the reference line SL1 by the amount of bending of the particle beam B. The irradiation unit position adjustment unit 71 tilts the irradiation port of the irradiation unit 2 to the negative side in the X-axis direction so that the irradiation range RE1 is shifted to the negative side in the X-axis direction relative to the reference line SL1. Then, the irradiation unit position adjustment unit 71 tilts the irradiation port of the irradiation unit 2 to the positive side in the X-axis direction so that the irradiation range RE2 is shifted to the positive side in the X-axis direction relative to the reference line SL1. At this time, the irradiation range RE1 and the irradiation range RE2 are approximately the same range on the reference line SL2. Therefore, the size of the irradiation field where the two overlap can be increased.

[0047] The correction unit 70 may correct the irradiation pattern based on the kinetic energy of particle beam B. For example, the irradiation unit position adjustment unit 71 of the correction unit 70 adjusts the tilt amount of the irradiation unit 2 so that irradiation range RE1 and irradiation range RE2 are in the same range on the reference line SL2. If the kinetic energy of particle beam B changes, the irradiation unit position adjustment unit 71 may change the tilt amount of the irradiation unit 2 to match the changed kinetic energy.

[0048] The correction unit 70 may have a magnetic field adjustment unit 72 that adjusts the magnetic field of the scanning electromagnet 50 of the irradiation unit 2. Figure 7(a) is a conceptual diagram of the irradiation of the irradiation unit 2 after magnetic field adjustment by the magnetic field adjustment unit 72, viewed from the Y-axis direction. Figure 7(b) is a diagram showing the power supply circuit for the scanning electromagnet 50.

[0049] As shown in Figure 7(a), the magnetic field adjustment unit 72 tilts the scanning electromagnet 50 so that the base axis AX is tilted relative to the reference line SL1 by the amount of bending of the particle beam B. The magnetic field adjustment unit 72 tilts the downstream side of the scanning electromagnet 50 to the negative side in the X-axis direction so that the irradiation range RE1 is shifted to the negative side in the X-axis direction relative to the reference line SL1. Then, the magnetic field adjustment unit 72 tilts the downstream side of the scanning electromagnet 50 to the positive side in the X-axis direction so that the irradiation range RE2 is shifted to the positive side in the X-axis direction relative to the reference line SL1. At this time, the irradiation range RE1 and the irradiation range RE2 are approximately the same range along the reference line SL2. Therefore, the size of the irradiation field where the two overlap can be increased.

[0050] The correction unit 70 may correct the irradiation pattern based on the kinetic energy of particle beam B. For example, the magnetic field adjustment unit 72 of the correction unit 70 adjusts the tilt amount of the scanning electromagnet 50 so that irradiation range RE1 and irradiation range RE2 are in the same range on the reference line SL2. If the kinetic energy of particle beam B changes, the magnetic field adjustment unit 72 may change the tilt amount of the scanning electromagnet 50 to match the changed kinetic energy.

[0051] As shown in Figure 7(b), it is preferable to connect a unipolar bias power supply 77 to the scanning electromagnet 50 in addition to a bipolar scanning power supply 76 for scanning, in order to supply a bias current to one polarity. In this case, when the scanning electromagnet 50 is excited, the bias power supply 77 can always be configured to supply current equal to the bending allowance of the magnetic field to one polarity. For example, the scanning power supply 76 could be configured to supply current in a state that is not symmetrical with respect to both polarities, but this method would require a larger range of current that can be output as a power supply, thus increasing costs. In contrast, by adding a bias power supply 77 and offsetting the sweep current, costs can be suppressed.

[0052] The correction unit 70 may have a patient fixation unit 73 that can fix a patient 15 having a tumor 14 and whose position can be adjusted relative to the irradiation unit 2. The patient fixation unit 73 is configured by providing a moving mechanism on the treatment table 6. Figure 8(a) is a conceptual diagram of the irradiation of the irradiation unit 2 as seen from the Y-axis direction when the patient fixation unit 73 is performing position adjustment. Figure 8(b) is a conceptual diagram showing the operation of the patient fixation unit 73.

[0053] As shown in Figure 8(a), the irradiated object fixing unit 73 moves the tumor 14 of patient 15 by the amount of bending of the particle beam B, following the amount of bending. The irradiated object fixing unit 73 moves toward the positive side of the X-axis direction together with the tumor 14 of patient 15 to follow the irradiation range RE1 which is shifted toward the positive side of the X-axis direction. Then, the irradiated object fixing unit 73 moves toward the negative side of the X-axis direction together with the tumor 14 of patient 15 to follow the irradiation range RE2 which is shifted toward the negative side of the X-axis direction. At this time, the irradiation range RE1 and the irradiation range RE2 have similar irradiation patterns for the tumor 14 of patient 15. This makes it possible to increase the size of the effective irradiation field for the tumor 14 of patient 15.

[0054] As shown in Figure 8(b), the position of the object to be irradiated fixing part 73 may be moved to rotate according to the rotation angle of the irradiation part 2 (the rotation angle of the rotating gantry 17).

[0055] The correction unit 70 may correct the irradiation pattern based on the kinetic energy of particle beam B. For example, the irradiated object fixing unit 73 of the correction unit 70 adjusts the amount of movement of the tumor 14 of the patient 15 according to the bending amount of irradiation range RE1 and irradiation range RE2. If the kinetic energy of particle beam B changes, the irradiated object fixing unit 73 may change the amount of movement to match the changed kinetic energy.

[0056] Next, the operation and effects of the particle beam therapy apparatus 1 according to this embodiment will be described.

[0057] The particle beam therapy device 1 comprises an irradiation unit 2 that irradiates the tumor 14 of patient 15 with particle beam B, and an MRI device 60 that acquires an image of the tumor 14 of patient 15 using a magnetic field MF. Therefore, the irradiation unit 2 can irradiate the tumor 14 of patient 15 with particle beam B based on the image acquired by the MRI device 60. Here, the particle beam therapy device 1 also comprises a correction unit 70 that corrects the irradiation pattern of particle beam B by the irradiation unit 2 to the tumor 14 of patient 15 according to the amount of bending of particle beam B due to the magnetic field MF of the MRI device 60. Therefore, even if the particle beam B is bent due to the influence of the magnetic field MF of the MRI device 60, the correction unit 70 corrects the irradiation pattern to match the amount of bending. Thus, the effect of bending of particle beam B due to the magnetic field MF of the MRI device 60 can be reduced.

[0058] The correction unit 70 may have an irradiation unit position adjustment unit 71 that can adjust the position of the irradiation unit 2. In this case, the irradiation unit position adjustment unit 71 adjusts the position of the irradiation unit 2 according to the amount of bending of the particle beam B, so that the particle beam B can be irradiated onto the tumor 14 of the patient 15 from a position that eliminates the bending of the particle beam B.

[0059] The correction unit 70 may include a magnetic field adjustment unit 72 that adjusts the magnetic field of the scanning electromagnet 50 of the irradiation unit 2. In this case, the magnetic field adjustment unit 72 adjusts the magnetic field of the scanning electromagnet 50 of the irradiation unit 2 according to the amount of bending of the particle beam B, thereby correcting the tilt to eliminate the bending of the particle beam B and allowing the tumor 14 of the patient 15 to be irradiated with the particle beam B.

[0060] The correction unit 70 may have an irradiated body fixing unit 73 that can fix the tumor 14 of the patient 15 and can be adjusted in position relative to the irradiation unit 2. In this case, the irradiated body fixing unit 73 can move the tumor 14 of the patient 15 according to the amount of bending of the particle beam B, so that the tumor 14 of the patient 15 can be irradiated with the particle beam B at a position where the bending can be eliminated.

[0061] The irradiation unit 2 may be configured to rotate around the tumor 14 of the patient 15. In this case, the correction unit 70 can correct the irradiation pattern according to the amount of bending of the particle beam B at the rotational position of the irradiation unit 2.

[0062] The correction unit 70 may correct the irradiation pattern based on the kinetic energy of particle beam B. The amount of bending changes according to the kinetic energy of particle beam B. Therefore, the correction unit 70 can correct the irradiation pattern to an appropriate one according to this change.

[0063] The MRI apparatus 60 has a coil 61 that generates a magnetic field MF, and the central axis CL of the coil 61 may extend in a direction perpendicular to the base axis AX of the particle beam B irradiated from the irradiation unit 2. In this case, the particle beam B bends in a direction perpendicular to both the central axis CL of the coil 61 and the base axis AX. The correction unit 70 corrects for this bending.

[0064] The present invention is not limited to the embodiments described above.

[0065] Although a cyclotron was shown as an example of an accelerator in Figure 1, the configuration of the present invention may also be applied to various accelerators such as synchrocyclotrons and linear accelerators (linacs).

[0066] The correction units 70 shown in Figures 5 to 8 may be adopted individually or in combination of two or more.

[0067] In the above-described embodiment, the irradiation unit could rotate around the irradiated object by a rotating gantry. Alternatively, the irradiation unit may be configured as a fixed irradiation port. In this case, since the particle beam is irradiated from only one side, correction by the correction unit becomes easier. In the correction unit 70, the irradiation pattern was corrected based on the kinetic energy of the particle beam B in various ways, but the irradiation pattern may also be corrected based on the velocity of the particle beam B. [Explanation of Symbols]

[0068] 1...Particle beam therapy device, 2...Irradiation unit, 3...Accelerator, 14...Tumor (irradiated object), 50...Scanning electromagnet, 60...MRI device (magnetic resonance imaging unit), 70...Correction unit, 71...Irradiation unit position adjustment unit, 72...Magnetic field adjustment unit, 73...Irradiated object fixing unit.

Claims

[Claim 1] An irradiation unit that irradiates the object to be irradiated with a particle beam, A magnetic resonance imaging unit that acquires an image of the irradiated object using a magnetic field, The system includes a correction unit that corrects the irradiation pattern of the particle beam by the irradiation unit to the irradiated object according to the amount of bending of the particle beam by the magnetic field of the magnetic resonance imaging unit, The correction unit has a target object fixing unit that can fix the target object and adjust the position of the target object relative to the irradiation unit so as to follow the bending amount of the particle beam, in a particle beam therapy apparatus.

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