Particle therapy device

Abstract

A particle therapy device according to the present invention comprises an irradiation unit that irradiates a particle beam at an irradiation target, a rotating gantry that supports the irradiation unit such that the irradiation unit can rotate around the irradiation target, and a magnetic resonance imaging unit that is provided to the rotating gantry and acquires an image of the irradiation target by means of magnetic fields. To acquire a desired cross-sectional image regardless of the rotation of the rotating gantry, the magnetic resonance imaging unit: has a gradient magnetic field generation unit that generates a gradient magnetic field in each of three axial directions; can apply gradient magnetic fields for at least two axes at the same time; and acquires a cross-sectional image for a desired stationary coordinate system by superimposing vectors for the gradient magnetic fields from the gradient magnetic field generation unit for the different axes on the basis of the rotation angle of the rotating gantry.

Description

Particle beam therapy equipment

[0001] The present disclosure relates to a particle beam therapy device.

[0002] A conventional radiotherapy device for treating a patient using radiation is disclosed in, for example, Patent Document 1. In the radiotherapy device disclosed in Patent Document 1, a particle beam is irradiated from an irradiation unit. An MRI device is also provided at the treatment position of the patient.

[0003] Japanese Patent Application Laid-Open No. 2021-49042

[0004] In a system in which an MRI device is incorporated into a rotating gantry as described above, the MRI device also rotates as the rotating gantry rotates. As a result, the images obtained by the MRI device also rotate in accordance with the rotation of the rotating gantry. Therefore, it has been desired to obtain desired images regardless of the rotation of the rotating gantry.

[0005] Therefore, an object of the present disclosure is to provide a particle beam therapy system that can acquire a desired image regardless of the rotation of the rotating gantry.

[0006] A particle beam therapy device according to one aspect of the present disclosure includes an irradiation unit that irradiates a particle beam onto an irradiated body, a rotating gantry that supports the irradiation unit so that it can rotate around the irradiated body, and a magnetic resonance imaging unit that is provided on the rotating gantry and acquires an image of the irradiated body using a magnetic field, and the magnetic resonance imaging unit acquires any cross-sectional image regardless of the rotation of the rotating gantry.

[0007] A particle beam therapy system includes a rotating gantry that supports an irradiation unit rotatably around an irradiated body, and a magnetic resonance imaging unit that is mounted on the rotating gantry and acquires images of the irradiated body using a magnetic field. In this case, the rotation of the irradiation unit on the rotating gantry allows images of the irradiated body irradiated with particle beams from multiple directions to be acquired. Here, the magnetic resonance imaging unit rotates together with the rotating gantry. In contrast, in a particle beam therapy system according to the present disclosure, the magnetic resonance imaging unit acquires any cross-sectional image regardless of the rotation of the rotating gantry. Therefore, even if the magnetic resonance imaging unit is rotated by the rotating gantry, any cross-sectional image can be acquired regardless of the rotation. As a result, desired images can be acquired regardless of the rotation of the rotating gantry.

[0008] The magnetic resonance imaging unit may have a gradient magnetic field generating unit that generates gradient magnetic fields in three axial directions and can simultaneously apply gradient magnetic fields in at least two axes. In this case, by superimposing the gradient magnetic fields in at least two axes, a gradient magnetic field in a desired direction can be generated to obtain a desired image.

[0009] The magnetic resonance imaging unit may synchronize power supplies that supply power to at least two-axis gradient magnetic field generating units, respectively. In this case, the power supplies can simultaneously excite the at least two-axis gradient magnetic field generating units and simultaneously apply gradient magnetic fields.

[0010] The magnetic resonance imaging unit may acquire a cross-sectional image in any direction by using at least two-axial gradient magnetic field generators. In this case, the magnetic resonance imaging unit can acquire a cross-sectional image in a desired direction by adjusting the at least two-axial gradient magnetic field generators.

[0011] The magnetic resonance imaging unit may acquire a cross-sectional image in an arbitrary stationary coordinate system by superimposing the vectors of the gradient magnetic fields of the gradient magnetic field generating units for each axis based on the rotation angle of the rotating gantry. In this case, the magnetic resonance imaging unit can generate a desired gradient magnetic field that is aligned with the stationary coordinate system by superimposing the vectors by adjusting the gradient magnetic fields of the gradient magnetic field generating units for each axis based on the rotation angle.

[0012] According to the present disclosure, it is possible to provide a particle beam therapy system that can acquire a desired image regardless of the rotation of a rotating gantry.

[0013] FIG. 1 is a schematic configuration diagram showing a radiation therapy device according to an embodiment of the present disclosure. FIG. 2 is a schematic configuration diagram of the vicinity of the irradiation unit of the radiation therapy device of FIG. 1. FIG. 3 is a diagram showing layers set for a tumor. FIG. 4 is a schematic cross-sectional view showing the structure around an MRI device and a rotating gantry. FIG. 5 is a schematic front view showing the structure around an MRI device and a rotating gantry. FIG. 6 is a diagram showing gradient magnetic field coils in each axial direction. FIG. 7 is a diagram showing a combined structure of an x-axis gradient magnetic field coil and a y-axis gradient magnetic field coil. FIG. 8 is a diagram for explaining the operation of an MRI device. FIG. 9 is a diagram showing a gradient magnetic field coil according to a modified example.

[0014] A radiotherapy device according to an embodiment of the present disclosure will be described below with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0015] 1 is a schematic configuration diagram showing a particle beam therapy system 1 according to an embodiment of the present disclosure. The particle beam therapy system 1 is a system used for cancer treatment by radiation therapy, etc. The particle beam therapy system 1 is a device that treats an affected area by irradiating a patient 15 (a target) with particle beams.

[0016] The particle beam therapy system 1 includes an accelerator 3 that accelerates charged particles generated by an ion source device and emits the particle beam B, an irradiation unit 2 that irradiates a patient 15 with the particle beam B, 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 that surrounds a treatment table 6 and an MRI device 60. The irradiation unit 2 can be rotated around the treatment table 6, which is a support unit on which the patient 15 is placed, by the rotating gantry 17, with a central axis CL as the center of rotation. The particle beam therapy system 1 also includes an MRI device 60 (MRI: Magnetic Resonance Imaging) that acquires images of the patient 15 using a magnetic field. The configurations of the accelerator 3, irradiation unit 2, beam transport line 20, and MRI device 60 will be described in more detail below.

[0017] The beam transport line 20 includes a beam duct 21 for transporting the particle beam B, an electromagnet 22 such as a quadrupole electromagnet for focusing the particle beam B, and bending electromagnets 23A, 23B, 23C, and 22D for bending the trajectory of the particle beam B. The bending electromagnets 23A and 23B bend the trajectory of the particle beam B traveling from the accelerator 3 to the rotating gantry 17 toward the outer periphery of the central axis CL. The bending electromagnets 23C and 23D, at positions spaced from the central axis CL toward the outer periphery, bend the trajectory of the particle beam B traveling toward the outer periphery of the central axis CL, and direct it toward the inner periphery. Furthermore, the bending electromagnet 23D bends the trajectory of the particle beam B so that it travels in a direction perpendicular to the central axis CL and guides it to the irradiation unit 2.

[0018] 2 is a schematic diagram of the vicinity of the irradiation unit of the particle beam therapy device 1 of FIG. 1. In the following description, the terms "X-axis direction," "Y-axis direction," and "Z-axis direction" are used. The "Z-axis direction" refers to the direction in which the base axis AX of the particle beam B extends, and is the depth direction of irradiation of the particle beam B. The "base axis AX" refers to the irradiation axis of the particle beam B when not deflected by the scanning electromagnet 50 described below. FIG. 2 shows the particle beam B being irradiated along the base axis AX. The "X-axis direction" refers to one direction in a plane perpendicular to the Z-axis direction. The "Y-axis direction" refers to a direction perpendicular to the X-axis direction in a plane perpendicular to the Z-axis direction.

[0019] First, the schematic configuration of a particle beam therapy system 1 according to this embodiment will be described with reference to Fig. 2. The particle beam therapy system 1 is an irradiation system using 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 particle beam therapy system 1 includes 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.

[0020] The accelerator 3 is a device that accelerates charged particles and emits a particle beam B of a preset intensity. Examples of the accelerator 3 include a cyclotron and a synchrocyclotron. The accelerator 3 is connected to a control unit 7, which controls the current supplied to the accelerator 3. The particle beam B generated by the accelerator 3 is transported to the irradiation unit 2 by a beam transport line 20. The beam transport line 20 connects the accelerator 3 and the irradiation unit 2, and transports the particle beam B emitted from the accelerator 3 to the irradiation unit 2.

[0021] The irradiation unit 2 irradiates a tumor (irradiated object) 14 inside the body of a patient 15 with a particle beam B. The particle beam B is electrically charged particles accelerated to high speed, such as a proton beam, a heavy particle (heavy ion) beam, or an electron beam. Specifically, the irradiation unit 2 is a device that irradiates the tumor 14 with the particle beam B emitted from an accelerator 3 that accelerates charged particles generated by an ion source (not shown) and transported via a beam transport line 20. The irradiation unit 2 includes a scanning electromagnet 50, a quadrupole electromagnet 8, a profile monitor 11, a dose monitor 12, position monitors 13a and 13b, a collimator 40, and a degrader 30. The scanning electromagnet 50, the monitors 11, 12, 13a, and 13b, the quadrupole electromagnet 8, and the degrader 30 are housed in an irradiation nozzle 9, which serves as a housing. In this manner, the irradiation unit 2 is configured by housing each of the main components in the irradiation nozzle 9. The quadrupole electromagnet 8, the profile monitor 11, the dose monitor 12, the position monitors 13a and 13b, and the degrader 30 may be omitted.

[0022] An X-axis scanning electromagnet 50A and a Y-axis scanning electromagnet 50B are used as the scanning electromagnets 50. Each of the X-axis scanning electromagnet 50A and the Y-axis scanning electromagnet 50B is composed of a pair of electromagnets, and changes the magnetic field between the pair of electromagnets in response to a current supplied from the control unit 7 to scan 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 arranged in this order on the base axis AX, downstream of the accelerator 3 from the particle beam B. The scanning electromagnets 50 scan the particle beam B so that the particle beam B is irradiated according to a scan pattern previously planned by the treatment planning device 90. How the scanning electromagnets 50 are controlled will be described later.

[0023] The quadrupole electromagnets 8 include an X-axis quadrupole electromagnet 8a and a Y-axis quadrupole electromagnet 8b. The X-axis quadrupole electromagnet 8a and the Y-axis quadrupole electromagnet 8b focus and converge the particle beam B in accordance with the current supplied from the control unit 7. The X-axis quadrupole electromagnet 8a focuses the particle beam B in the X-axis direction, and the Y-axis quadrupole electromagnet 8b focuses the particle beam B in the Y-axis direction. The beam size of the particle beam B can be changed by changing the amount of focusing (amount of convergence) by changing the current supplied to the quadrupole electromagnets 8. The quadrupole electromagnets 8 are arranged on the base axis AX between the accelerator 3 and the scanning electromagnet 50 in this order. The beam size refers to the size of the particle beam B in the XY plane. The beam shape refers to the shape of the particle beam B in the XY plane.

[0024] The profile monitor 11 detects the beam shape and position of the particle beam B for alignment during initial setup. The profile monitor 11 is disposed on the base axis AX between the quadrupole electromagnet 8 and the scanning electromagnet 50. The dose monitor 12 detects the dose of the particle beam B. The dose monitor 12 is disposed 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 the particle beam B. The position monitors 13a and 13b are disposed on the base axis AX downstream of the particle beam B from the dose monitor 12. Each of the monitors 11, 12, 13a, and 13b outputs the detected results to the control unit 7.

[0025] The degrader 30 reduces the intensity of the passing particle beam B to finely adjust the intensity of the particle beam B. In this embodiment, the degrader 30 is provided at the tip 9 a of the irradiation nozzle 9. The tip 9 a of the irradiation nozzle 9 is the end portion on the downstream side of the particle beam B.

[0026] The collimator 40 is a member that is provided at least downstream of the scanning electromagnet 50 in the particle beam B, and blocks a part of the particle beam B and allows a part of the particle beam B to pass through. In this example, the collimator 40 is provided downstream of the position monitors 13 a and 13 b. The collimator 40 is connected to a collimator driver 51 that moves the collimator 40.

[0027] The control unit 7 is configured with, for example, a CPU, a ROM, a RAM, etc. The control unit 7 controls the accelerator 3, the scanning electromagnet 50, the quadrupole electromagnet 8, and the collimator driving unit 51 based on the detection results output from the monitors 11, 12, 13a, and 13b.

[0028] The control unit 7 of the particle beam therapy system 1 is also connected to a treatment planning device 90 that creates a treatment plan for 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 using a CT or the like before treatment and plans a dose distribution (dose distribution of the particle beam to be irradiated) at each position on 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. The scan pattern created by the treatment planning device 90 plans the scanning path and scanning speed of the particle beam B.

[0029] When irradiating with particle beams using the scanning method, the tumor 14 is virtually divided into multiple layers in the Z-axis direction, and particle beams are scanned and irradiated in one layer along a scanning path defined in the treatment plan. After irradiation of the particle beams in the one layer is completed, particle beams B are irradiated in the next adjacent layer.

[0030] When the particle beam B is irradiated by the scanning method using the particle beam therapy system 1 shown in FIG. 2, the quadrupole electromagnet 8 is activated (ON) so that the passing particle beam B is converged.

[0031] 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 under the control of scanning electromagnet 50. As a result, particle beam B is irradiated while scanning within the irradiation range of one layer set in the Z-axis direction relative to tumor 14. After irradiation of one layer is completed, particle beam B is irradiated onto the next layer.

[0032] 3(a) and 3(b) will be used to explain particle beam irradiation images of the scanning electromagnet 50 in response to the control of the control unit 7. Fig. 3(a) shows an irradiated object virtually sliced ​​into multiple layers in the depth direction, and Fig. 3(b) shows a particle beam scanning image in one layer as viewed from the depth direction.

[0033] As shown in FIG. 3A, the object to be irradiated is virtually sliced ​​into a plurality of layers in the irradiation depth direction. In this example, the layers are arranged in order from the deepest layer (the longest range of the particle beam B), as follows: １ , Layer L ２ , ...Layer L ｎ－１ , Layer L ｎ , Layer L ｎ＋１ , ...Layer L Ｎ－１ , Layer L Ｎ As shown in FIG. 3B, the particle beam B is virtually sliced ​​into layers L and N while tracing a beam trajectory along a scanning path TL. In the case of continuous irradiation (line scanning or raster scanning), the particle beam B is virtually sliced ​​into layers L and N. ｎ In the case of spot scanning, the light is continuously irradiated along the scanning path TL of the layer L ｎ The particle beam B is irradiated onto a plurality of irradiation spots. The particle beam B is irradiated along a scanning path TL1 extending in the X-axis direction, shifted slightly in the Y-axis direction along a scanning path TL2, and then irradiated 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 on the scanning path TL.

[0034] Next, the MRI apparatus 60 and the rotating gantry 17 will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic cross-sectional view showing the structure of the MRI apparatus 60 and the rotating gantry 17 and its surroundings. FIG. 5 is a schematic front view showing the structure of the MRI apparatus 60 and the rotating gantry 17 and its surroundings. As shown in FIG. 4, the MRI apparatus 60 is mounted on the rotating gantry 17 together with the irradiation unit 2. The MRI apparatus 60 can be rotated around the treatment table 6 by the rotating gantry 17, with the central axis CL as the center of rotation. The MRI apparatus 60 includes multiple coils 61 (a pair in FIG. 1) that are sources of magnetic fields. The MRI apparatus 60 is a passive shield type apparatus that returns magnetic flux generated by the coils 61 using an iron yoke 62. The MRI apparatus 60 includes a gradient magnetic field coil unit 70 and a radio-frequency transmission / reception system (not shown) for generating magnetic resonance and collecting the resulting signals. The MRI apparatus 60 also includes a processing unit 63 (see FIG. 2) that controls the energization of the gradient magnetic field coil unit 70, generates an MRI image from the detected values ​​of the high frequency transmission / reception system, and outputs the image to the control unit 7.

[0035] The pair of coils 61 have an annular shape centered on 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, sandwiching the irradiation unit 2 therebetween. As a result, the magnetic field generated by the MRI device 60 is parallel to the direction in which the central axis CL extends, i.e., perpendicular to the base axis AX of the particle beam B. At this time, the central axis CL of the coils 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 couch 6 so that the tumor 14 (see FIG. 2 ) is within the uniform magnetic field generated by the coils 61 of the MRI device 60, and an MRI image of the area around the tumor 14 is taken.

[0036] The yoke 62 of the MRI apparatus 60 includes a shield member 66 and a return yoke portion 67. The shield member 66 is a cylindrical member centered on the central axis CL. An opening 68 is formed in the shield member 66 at a position radially opposite 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 shield member 66. The return yoke portion 67 is a member that extends in a direction perpendicular to the central axis CL inside the shield member 66 at the rear side of the rotating gantry 17 and is connected to the inner circumferential surface of the shield member 66. The return yoke portion 67 and the shield member 66 form a path for magnetic flux, i.e., a magnetic circuit. The shield member 66 is configured as a structural member of the rotating gantry 17. The shield member 66 is configured as a cylindrical rotating shaft member of the rotating gantry 17. The shield member 66 rotates about the central axis CL. The shield member 66 is configured in a circular shape so as to completely surround the treatment table 6 and the MRI device 60 when viewed from the Y-axis direction (see FIG. 5).

[0037] Next, the configuration of the gradient coil unit 70 will be described. The gradient coil unit 70 generates a gradient magnetic field at the timing of capturing an image. As shown in FIG. 4 , the gradient coil unit 70 may include a first unit 70A and a second unit 70B, sandwiching an opening 68 to allow a particle beam B to pass therethrough. The first unit 70A and the second unit 70B are cylindrical members centered on a central axis CL and arranged side by side in the Y-axis direction. The gradient coil unit 70 includes gradient coils that generate gradient magnetic fields in three axial directions. Specifically, the gradient coil unit 70 includes x-axis gradient coils 71A and 71B (gradient magnetic field generators), y-axis gradient coils 72A and 72B (gradient magnetic field generators), and z-axis gradient coils 73A and 73B (gradient magnetic field generators), as shown in FIG. 6 . The first unit 70A includes one x-axis gradient coil 71A, a y-axis gradient coil 72A, and a z-axis gradient coil 73A. The second unit 70B has the other x-axis gradient magnetic field coil 71B, y-axis gradient magnetic field coil 72B, and z-axis gradient magnetic field coil 73B.

[0038] The gradient coils 71, 72, and 73 in each axial direction will be described in detail with reference to FIGS. 6 and 7 . To explain the gradient coils 71, 72, and 73, an xyz coordinate system, which is a relative coordinate system with respect to the gradient coil unit 70, is set. When compared with the XYZ coordinate system, which is a relative coordinate system with respect to the irradiation unit 2 in FIGS. 2 to 5 , the z-axis direction of the gradient coil unit 70 corresponds to the Y-axis direction of the irradiation unit 2, which is the direction in which the central axis CL extends. Therefore, in the xyz coordinate system, the first unit 70A and the second unit 70B are arranged so as to be aligned in the z-axis direction. The x-axis and y-axis directions of the gradient coil unit 70 may correspond to the Z-axis and X-axis directions of the irradiation unit 2, but the correspondence is not particularly limited, and they may correspond to any direction in the ZX plane of the irradiation unit 2.

[0039] As shown in FIG. 6A, the first unit 70A has a pair of x-axis gradient magnetic field coils 71A, 71A facing each other in the x-axis direction. The second unit 70B has a pair of x-axis gradient magnetic field coils 71B, 71B facing each other in the x-axis direction. Each of the coils 71A, 71B has a configuration in which a coil wound in a rectangular ring shape is curved into a semi-cylindrical shape. The pair of x-axis gradient magnetic field coils 71A, 71A are arranged so that their central axes coincide with each other and are combined to form a substantially cylindrical shape. The pair of x-axis gradient magnetic field coils 71B, 71B are arranged so that their central axes coincide with each other and are combined to form a substantially cylindrical shape. The main magnetic field B generated by the coil 61 of the MRI apparatus 60 ０ is generated toward the positive side in the z-axis direction. ０ and a forward magnetic field Ba is generated, and a main magnetic field B is generated between the x-axis gradient magnetic field coils 71A and 71B on the other side. ０ An x-axis gradient magnetic field Gx in the x-axis direction is generated between the x-axis gradient magnetic field coils 71A and 71B so as to form a magnetic field distribution of a first-order component.

[0040] As shown in FIG. 6B, the first unit 70A has a pair of y-axis gradient magnetic field coils 72A, 72A facing each other in the y-axis direction. The second unit 70B has a pair of y-axis gradient magnetic field coils 72B, 72B facing each other in the y-axis direction. Each of the coils 72A, 72B has a configuration in which a coil wound in a rectangular ring shape is curved into a semi-cylindrical shape. The pair of y-axis gradient magnetic field coils 72A, 72A are arranged so that their central axes coincide with each other and are combined to form a substantially cylindrical shape. The pair of y-axis gradient magnetic field coils 72B, 72B are arranged so that their central axes coincide with each other and are combined to form a substantially cylindrical shape. The main magnetic field B generated by the coil 61 of the MRI apparatus 60 ０ is generated toward the positive side in the z-axis direction. ０ and a forward magnetic field Ba is generated, and a main magnetic field B is generated between the y-axis gradient magnetic field coils 72A and 72B on the other side. ０ A magnetic field Bb in the opposite direction to the y-axis gradient coils 72A and 72B is generated. A y-axis gradient magnetic field Gy in the y-axis direction is generated between the y-axis gradient coils 72A and 72B so as to form a magnetic field distribution of a first-order component.

[0041] As shown in FIG. 6C, the first unit 70A has a z-axis gradient magnetic field coil 73A. The second unit 70B has a z-axis gradient magnetic field coil 73B. Each of the coils 73A and 73B has a configuration in which it is wound in an annular shape with a central axis extending in the z-axis direction. The z-axis gradient magnetic field coils 73A and 73B are arranged so that their central axes coincide with each other. The main magnetic field B generated by the coil 61 of the MRI apparatus 60 ０ is generated toward the positive side in the z-axis direction. ０ The z-axis gradient coil 73B on the other side generates a main magnetic field B ０ A magnetic field Bb in the opposite direction to the z-axis gradient coils 73A and 73B is generated. A z-axis gradient magnetic field Gz in the z-axis direction is generated between the z-axis gradient coils 73A and 73B so as to form a magnetic field distribution of a first-order component.

[0042] With the above-described configuration, the MRI apparatus 60 can apply gradient magnetic fields Gx, Gy, and Gz to the patient 15 in three axial directions, i.e., the x-axis, y-axis, and z-axis directions. In this embodiment, the MRI apparatus 60 can simultaneously apply gradient magnetic fields in at least two axes. The MRI apparatus 60 may simultaneously apply the gradient magnetic fields Gx and Gy, may simultaneously apply the gradient magnetic fields Gx and Gz, may simultaneously apply the gradient magnetic fields Gy and Gz, or may simultaneously apply the gradient magnetic fields Gx, Gy, and Gz.

[0043] When the x-axis gradient magnetic field Gx and the y-axis gradient magnetic field Gy are superimposed, the x-axis gradient magnetic field coil 71A and the y-axis gradient magnetic field coil 72A in the first unit 70A may be configured as shown in Fig. 7. As shown in Fig. 7, the y-axis gradient magnetic field coil 72A is arranged on the inner periphery, and the x-axis gradient magnetic field coil 71A is arranged so as to surround the y-axis gradient magnetic field coil 72A from the outer periphery. Note that in Fig. 7, the y-axis gradient magnetic field coil 72A is indicated by a dashed line for ease of understanding.

[0044] Next, the operation of the MRI apparatus 60 will be described with reference to FIGS. 8 and 9 . As shown in FIGS. 8 and 9 , the x-axis gradient coils 71A and 71B are supplied with power from an x-axis power supply 81. The y-axis gradient coils 72A and 72B are supplied with power from a y-axis power supply 82. The power supply device 80 can simultaneously excite the x-axis gradient coils 71A and 71B and the y-axis gradient coils 72A and 72B by synchronizing the x-axis power supply 81 and the y-axis power supply 82. In this case, the MRI apparatus 60 can generate a gradient magnetic field in which the vector of the x-axis gradient magnetic field Gx of the x-axis gradient coils 71A and 71B and the vector of the y-axis gradient magnetic field Gy of the y-axis gradient coils 72A and 72B are superimposed. In this manner, the MRI apparatus 60 can synchronize the power supplies that supply power to at least two gradient coils. In the following description, such superimposed gradient magnetic fields may be referred to as a "synthetic gradient magnetic field."

[0045] The MRI apparatus 60 can acquire any cross-sectional image regardless of the rotation of the rotating gantry 17. The MRI apparatus 60 can acquire cross-sectional images in any direction using at least two-axial gradient magnetic field coils. Furthermore, the MRI apparatus 60 can acquire cross-sectional images in any stationary coordinate system by superimposing the vectors of the gradient magnetic fields of the gradient magnetic field coils on each axis based on the rotation angle of the rotating gantry 17.

[0046] Here, a coordinate system defined by a first direction D1 and a second direction D2 is set as a stationary coordinate system for determining the orientation of a cross-sectional image of the tumor 14 in the patient 15. The patient 15 is treated while remaining fixed within the stationary coordinate system, regardless of the rotation of the rotating gantry 17.

[0047] First, imaging by the MRI apparatus 60 in the example shown in Fig. 8 will be described. In Fig. 8, the y-axis direction of the MRI apparatus 60 corresponds to a first direction D1, and the x-axis direction corresponds to a second direction D2. During imaging, a z-axis gradient magnetic field (Gz) is applied in accordance with an imaging pulse sequence to determine a slice plane in a direction perpendicular to the imaging cross section (slice plane). Specifically, the z-axis power supply 83 of the power supply device 80 excites the z-axis gradient magnetic field coils 73A and 73B with a current value that allows the imaging cross section to be set at a desired position in the z-axis direction.

[0048] As shown in Fig. 8(a), the x-axis power supply 81 excites the x-axis gradient coils 71A and 71B to generate an x-axis magnetic field Gx in the second direction D2. Also, as shown in Fig. 8(b), the y-axis power supply 82 excites the y-axis gradient coils 72A and 72B to generate a y-axis magnetic field Gy in the first direction D2. This applies a gradient magnetic field (Gy) that imparts frequency encoding to nuclear spins and a gradient magnetic field (Gx) that imparts phase encoding to nuclear spins in the imaging slice. Therefore, position information in the first direction D1 and the second direction D2 is encoded in the echo signals (NMR signals) emitted from the nuclear spins.

[0049] Next, imaging by the MRI apparatus 60 in the example shown in Fig. 9 will be described. In Fig. 9, due to rotation of the rotating gantry 17, the y-axis direction of the MRI apparatus 60 is tilted by a rotation angle θ1 with respect to the first direction D1, and the x-axis direction is tilted by a rotation angle θ1 with respect to the second direction D2. During imaging, a z-axis gradient magnetic field (Gz) is applied in accordance with the imaging pulse sequence to determine a slice plane in a direction perpendicular to the imaging cross section (slice plane), as in Fig. 8.

[0050] As shown in FIG. 9A , the power supply device 80 supplies power to the x-axis power supply 81 and the y-axis power supply 82 in a synchronized state, thereby simultaneously exciting the x-axis gradient coils 71A, 71B and the y-axis gradient coils 72A, 72B. This simultaneously generates the x-axis gradient magnetic field Gx and the y-axis gradient magnetic field Gy. At this time, the power supply device 80 generates a composite gradient magnetic field MG2 directed in the second direction D2 by superimposing the x-axis gradient magnetic field Gx and the y-axis gradient magnetic field Gy, taking into account the rotation angle θ1 of the rotating gantry 17. Also, as shown in FIG. 9B , the power supply device 80 generates a composite gradient magnetic field MG2 directed in the first direction D1 by superimposing the x-axis gradient magnetic field Gx and the y-axis gradient magnetic field Gy, taking into account the rotation angle θ1 of the rotating gantry 17.

[0051] As a result, a gradient magnetic field (synthetic gradient magnetic field MG1) that imparts frequency encoding to nuclear spins and a gradient magnetic field (synthetic gradient magnetic field MG2) that imparts phase encoding are applied to the imaging cross section. Therefore, position information in the first direction D1 and the second direction D2 is encoded in the echo signals (NMR signals) emitted from the nuclear spins. In this way, as shown in Figures 8 and 9, gradient magnetic fields directed in the first direction D1 and the second direction D2 of the stationary coordinate system can be generated in either case, regardless of the rotation of the rotating gantry 17. This allows cross-sectional images in the same direction to be obtained in Figures 8 and 9.

[0052] Next, the operation and effects of the particle beam therapy system 1 according to this embodiment will be described.

[0053] The particle beam therapy system 1 includes a rotating gantry 17 that supports the irradiation unit 2 so that it can rotate around the patient 15, and an MRI device 60 that is attached to the rotating gantry 17 and acquires images of the patient 15 using a magnetic field. In this case, the rotation of the irradiation unit 2 by the rotating gantry 17 allows images of the patient 15 being irradiated with particle beams B from multiple directions to be acquired. Here, the MRI device 60 rotates together with the rotating gantry 17. In contrast, in the particle beam therapy system 1 according to this embodiment, the MRI device 60 acquires any cross-sectional image regardless of the rotation of the rotating gantry 17. Therefore, even if the MRI device 60 is rotated by the rotating gantry 17, any cross-sectional image can be acquired regardless of the rotation. As described above, desired images can be acquired regardless of the rotation of the rotating gantry 17.

[0054] The MRI apparatus 60 may have gradient coils that generate gradient magnetic fields in three axial directions and may be capable of simultaneously applying gradient magnetic fields in at least two axes. In this case, by superimposing the gradient magnetic fields in at least two axes, a gradient magnetic field in a desired direction can be generated to obtain a desired image.

[0055] The MRI apparatus 60 may synchronize the power supplies that supply power to the at least two-axis gradient magnetic field coils, respectively. In this case, the power supply device 80 can simultaneously excite the at least two-axis gradient magnetic field coils and simultaneously apply gradient magnetic fields.

[0056] The MRI apparatus 60 may acquire a cross-sectional image in any direction using at least two-axial gradient magnetic field coils. In this case, the MRI apparatus 60 can acquire a cross-sectional image in a desired direction by adjusting the at least two-axial gradient magnetic field coils.

[0057] The MRI apparatus 60 may acquire a cross-sectional image in any stationary coordinate system by superimposing the vectors of the gradient magnetic fields of the gradient magnetic field coils on each axis based on the rotation angle of the rotating gantry 17. In this case, the MRI apparatus 60 can generate a desired gradient magnetic field that is aligned with the stationary coordinate system by superimposing the vectors by adjusting the gradient magnetic fields of the gradient magnetic field coils on each axis based on the rotation angle.

[0058] The present disclosure is not limited to the above-described embodiments.

[0059] In the above-described embodiment, a rotating gantry that rotates 360° has been exemplified, but a rotating gantry that rotates at a particularly limited rotation angle smaller than 360° may also be used. For example, a rotating gantry with a rotation angle of 180° or 270° may be used. In other words, the rotating gantry may be any gantry that can rotatably support the irradiation unit around the irradiated object, and there is no particular limitation on the range of rotation around the irradiated object.

[0060] Although a cyclotron is shown as an example of an accelerator in FIG. 1, the configuration of the present disclosure may also be adopted for various accelerators, such as a synchrocyclotron or a linear accelerator (linac).

[0061] The MRI apparatus is not limited to a tunnel-type apparatus as shown in FIG. 4 . For example, the present disclosure may be applied to an open-type MRI apparatus. In this case, as shown in FIG. 10 , a gradient coil 110 that generates a gradient magnetic field in the direction of the main magnetic field may be combined with gradient coils 111A and 111B that generate a gradient magnetic field in a direction perpendicular to the rotation axis of the gantry. In this configuration, the gradient magnetic fields may also be superimposed by simultaneously exciting the gradient coil 110 and the gradient coils 111A and 111B.

[0062] 6 and 7 are merely examples of the structure of the gradient coil, and any coil structure may be used as long as it can generate a gradient magnetic field.

[0063] In the above-described embodiment, examples in which cross-sectional images are acquired in a direction corresponding to a stationary coordinate system have been described with reference to Figures 8 and 9. However, the cross-sectional images do not need to be based on a stationary coordinate system, and cross-sectional images in any direction may be acquired according to the needs of the user.

[0064] 1...particle beam therapy device, 2...irradiation unit, 14...tumor (irradiated object), 15...patient (irradiated object), 17...rotating gantry, 60...MRI device (magnetic resonance imaging unit), 71, 72, 73...gradient magnetic field coil (gradient magnetic field generating unit).

Claims

1. An irradiation unit that irradiates a subject with a particle beam, an irradiation unit that irradiates the subject with a particle beam, a rotating gantry that rotatably supports the irradiation unit around the subject, and a magnetic resonance imaging unit provided on the rotating gantry and acquiring an image of the subject by a magnetic field, wherein the magnetic resonance imaging unit acquires an arbitrary cross-sectional image regardless of the rotation of the rotating gantry. A particle beam therapy apparatus.

2. The particle beam therapy apparatus according to claim 1, wherein the magnetic resonance imaging unit has a gradient magnetic field generation unit that generates gradient magnetic fields in three axial directions, and is capable of applying at least two axial gradient magnetic fields simultaneously.

3. The particle beam therapy apparatus according to claim 2, wherein the magnetic resonance imaging unit synchronizes power supplies that supply power to the gradient magnetic field generation units of at least two axes, respectively.

4. The particle beam therapy apparatus according to claim 2, wherein the magnetic resonance imaging unit acquires a cross-sectional image in an arbitrary direction by the gradient magnetic field generation units of at least two axes.

5. The particle beam therapy apparatus according to claim 2, wherein the magnetic resonance imaging unit acquires a cross-sectional image in an arbitrary stationary coordinate system by superimposing the vectors of the gradient magnetic fields of the gradient magnetic field generation units on each axis based on the rotation angle of the rotating gantry.

Images