Circular accelerator and particle ray therapy system

Abstract

Provided is a circular accelerator and a particle beam therapy system that can irradiate a high-current, high-quality beam at low cost. The circular accelerator accelerates a beam of charged particles orbiting in a magnetic field in such a manner that the closed orbit of each energy of the beam is eccentric, and has: a beam exit port that emits a beam of different energy from the closed orbit; a first deflection electromagnet (21) and a second deflection electromagnet (22) that deflect the beam emitted from the beam exit port; and a control unit (40a) that controls the excitation amount of the first and second deflection electromagnets in accordance with the energy of the emitted beam, the control unit (40a) causing the first and second deflection electromagnets (21, 22) to be excited and deflect the beam when the energy of the emitted beam is the maximum energy on the design of the circular accelerator (1).

Description

TECHNICAL FIELD

[0001] The present application relates to a circular accelerator that accelerates a particle ray and a particle ray treatment system. BACKGROUND

[0002] In a circular accelerator that accelerates a charged particle beam while increasing the orbit radius by applying high frequency in a main magnetic field, as an example of a technique for controlling the ejection of a charged particle beam from a circular accelerator with high precision, Patent Literature 1 describes a technique in which a charged particle beam is ejected by applying high frequency different from the high frequency used for acceleration to the charged particle beam in a circular accelerator that accelerates a charged particle beam while increasing the orbit radius by applying high frequency in a main magnetic field.

[0003] As an example of a particle ray treatment device in which the adjustment time of a particle accelerator is shortened, the number of types of operation parameter files is small, the moving sound of a range shifter and the energy change time can be greatly reduced, the frequency of system stop due to equipment variation of the particle accelerator is low, and the variation in the energy and intensity of the charged particle beam is small, Patent Literature 2 describes a technique in which an energy changing device is provided, the energy changing device includes a range shifter whose thickness in the direction in which a charged particle beam passes through is different in a direction orthogonal to the beam passing direction, and reduces the energy of the passed charged particle beam by an amount proportional to the thickness, an upstream deflection electromagnet pair that moves the orbit of the charged particle beam in the direction in which the thickness changes in parallel on the upstream side of the range shifter in order to pass through the part in which the thickness of the range shifter differs, a downstream deflection electromagnet pair that moves the orbit of the charged particle beam that has passed through the range shifter to the extension line of the orbit at the time of injection to the upstream deflection electromagnet pair in parallel, and a change control device that controls the upstream deflection electromagnet pair and the downstream deflection electromagnet pair to cause the charged particle beam to travel on an orbit in which the energy of the charged particle beam is reduced to a desired value by passing through the range shifter.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2019-133745

[0007] Patent Literature 2: Japanese Patent No. 4115468 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] A charged particle beam (hereinafter, simply referred to as a beam) is accelerated by an accelerator such as a synchrotron or a cyclotron, and the beam thus accelerated is irradiated to a lesion such as cancer, thereby performing particle beam therapy.

[0010] As one of the accelerators used for particle beam therapy, there is, for example, the accelerator described in Patent Literature 1. In the circular accelerator described in Patent Literature 1, a circular closed orbit (hereinafter, referred to as a central orbit) formed by beam particles having different kinetic energies (hereinafter, simply referred to as energies) in a static magnetic field is arranged so as to be eccentric toward a beam exit of the accelerator, and beams having different energies are emitted from the same beam exit to the outside of the accelerator.

[0011] In the circular accelerator described in Patent Literature 1, after a beam circulating in the accelerator (hereinafter, referred to as a circulating beam) is accelerated to a desired energy, a high-frequency voltage in a direction (hereinafter, referred to as a horizontal direction) perpendicular to a beam traveling direction and a magnetic pole gap direction (hereinafter, referred to as a vertical direction) is applied to the circulating beam. The amplitude of oscillation of the beam particles to which the high-frequency voltage is applied in the horizontal direction around the central orbit (hereinafter, referred to as betatron oscillation) gradually increases, and comes into contact with a magnetic field distribution for generating resonance of the betatron oscillation, which is referred to as a stripping magnetic field and a regenerative magnetic field, formed around the central orbit. The amplitude of the betatron oscillation of the beam particles in the horizontal direction which has come into contact with the stripping magnetic field and the regenerative magnetic field sharply increases, and the beam is injected into a septum coil for emission. The septum coil deflects the beam toward the outer periphery direction of the circular accelerator. The deflected beam is emitted to a high-energy beam transport system which is outside the circular accelerator.

[0012] Therefore, the circular accelerator described in Patent Literature 1 is a circular accelerator which accelerates a beam in a static magnetic field, and can switch the energy of the beam emitted from the circular accelerator in a predetermined range (for example, a range of 70 MeV to 230 MeV).

[0013] On the other hand, in the circular accelerator described in Patent Literature 1, since the septum coil is provided in a limited space inside the magnetic pole of the circular accelerator, the strength of the magnetic field (septum magnetic field) generated by the septum coil is limited. The septum coil has a function of making the orbits of beams having different energies coincide at the beam exit of the circular accelerator, and therefore, in the circular accelerator described in Patent Literature 1, due to the insufficiency of the septum magnetic field, it is possible that the orbits of the beams emitted from the circular accelerator change with the energy.

[0014] Here, the deflection electromagnet, the quadrupole electromagnet, and the like which constitute the high-energy beam transport system need to be manufactured so as to have a beam orbit passing through all the energies of the high-energy beam transport system built therein.

[0015] Therefore, in the circular accelerator described in Patent Literature 1, in order to cope with the change in the trajectory of the emitted beam, the constituent devices of the high-energy beam transport system are likely to be upsized, and the installation area and cost of the accelerator system constituted by the high-energy beam transport system and the circular accelerator and the beam transport system are likely to increase, and thus there is room for improvement.

[0016] The energy changing device described in Patent Literature 2 is constituted by an energy absorber (range shifter) having a thickness different depending on the position in the plane perpendicular to the beam trajectory, two deflection electromagnets provided on the upstream side of the range shifter, and two deflection electromagnets provided on the downstream side of the range shifter.

[0017] In the energy changing device described in Patent Literature 2, the beam emitted from the accelerator is deflected by the deflection electromagnets on the upstream side, and thus the position at which the beam is injected into the range shifter, that is, the thickness of the range shifter is controlled, and the energy of the beam after passing through the range shifter is changed to a desired value. The beam that has passed through the range shifter is deflected by the deflection electromagnets on the downstream side, and is aligned on the extension line of the beam trajectory before the energy changing device. Thus, the energy changing device described in Patent Literature 2 can adjust the energy of the beam emitted from the cyclotron or the like to a desired value without changing the trajectory of the beam, and thus can adjust the energy of the beam emitted from the static magnetic field type accelerator such as a cyclotron for use in the purpose of particle therapy or the like.

[0018] On the other hand, in the energy changing device described in Patent Literature 2, since the range shifter is used in the change in the energy, the spatial spread (beam size) of the beam after the change in the energy is likely to be enlarged due to the scattering of the beam with the range shifter.

[0019] In recent years, in particle therapy, a scanning irradiation method in which a fine-diameter beam is used to scan a diseased part three-dimensionally is becoming widespread, and in terms of forming a high-precision radiation dose distribution by the scanning irradiation method, it is desired to suppress the enlargement of the beam size as much as possible.

[0020] Therefore, in the case of using the energy changing device described in Patent Literature 2, the spread of the energy of the beam particles (hereinafter, momentum spread) is likely to be enlarged when the beam passes through the range shifter, the passing efficiency of the high-energy beam transport system is likely to be reduced, and the effective beam current is likely to be reduced, and thus it is difficult to directly apply the technology, and improvement is required.

[0021] The present application has been achieved in view of the above-described problems, and an object thereof is to provide a circular accelerator and a particle therapy system capable of irradiating a large-current and high-quality beam at low cost.

[0022] Means for solving the problems

[0023] The present application includes a plurality of solutions to the above problems, and if one example is cited, it is a circular accelerator that accelerates a beam of charged particles orbiting in a magnetic field in such a way that the closed orbit of each energy of the beam is decentered, the circular accelerator being characterized by having: a beam exit port that emits a beam of different energy from the closed orbit; a first deflection electromagnet and a second deflection electromagnet that deflect the beam emitted from the beam exit port; and a control section that controls the excitation amount of the first deflection electromagnet and the second deflection electromagnet according to the energy of the emitted beam, in which case, with respect to the control section, in the case where the energy of the emitted beam is the maximum energy on the design of the circular accelerator, both the first deflection electromagnet and the second deflection electromagnet are excited to deflect the beam.

[0024] Effects of the Invention

[0025] According to the present application, it is possible to provide a circular accelerator and a particle beam therapy system that can irradiate a large current and high-quality beam at low cost. The above problems, structures, and effects are made clear by the following description of the embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a schematic view showing the structure of a particle beam therapy system using the circular accelerator of Embodiment 1 of the present application.

[0027] Figure 2 is a schematic view showing the structure of the circular accelerator of Embodiment 1.

[0028] Figure 3 is a schematic view showing the structure of a circular accelerator of Embodiment 2 of the present application.

[0029] Figure 4 is a schematic view showing the structure of a circular accelerator of Embodiment 3 of the present application.

[0030] In the drawings:

[0031] 1, 1A, 1B - circular accelerator, 10 - main body, 11 - magnetic pole, 12 - coil, 13 - beam extraction field generating device, 14 - yoke, 15 - beam extraction port, 16 - beam orbit surrounding region, 17 - orbit merging region, 18, 18A, 18B - orbit control device, 21, 61 - first deflection electromagnet, 22, 62, 22B - second deflection electromagnet, 23, 24, 63, 64 - power supply, 25, 65 - designed orbit, 26, 66, 67 - beam orbit, 30 - high-energy beam transport system, 31, 32 - profile monitor, 40, 40A, 40B - control device, 40a, 40a1, 40a2 - control section, 50 - rotating gantry, 50a, 50b, 50c - deflection electromagnet, 51 - patient, 52 - affected part, 53 - irradiation nozzle, 71 - quadrupole electromagnet, 72 - power supply, 100 - particle beam therapy system. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the circular accelerator and the particle beam therapy system of the present application will be described using the drawings. In addition, in the drawings used in the present specification, the same or corresponding components are sometimes denoted by the same or similar symbols, and repeated description will be omitted for these components.

[0033] <Embodiment 1>

[0034] Use Figure 1 and Figure 2 Embodiment 1 of the circular accelerator and the particle beam therapy system of the present application will be described.

[0035] First, use Figure 1 The overall structure of the particle beam therapy system including the circular accelerator will be described. Figure 1 is a schematic view showing the structure of the particle beam therapy system using the circular accelerator of Embodiment 1.

[0036] Figure 1 The particle beam therapy system 100 of the present embodiment shown in the drawing includes a circular accelerator 1 that accelerates and extracts a beam of charged particles that circulate in a magnetic field, a high-energy beam transport system 30 that transports the beam of charged particles accelerated by the circular accelerator 1, an irradiation nozzle 53 that irradiates the beam of charged particles transported by the high-energy beam transport system 30, and a control device 40, and the like.

[0037] In the particle beam therapy system 100, the beam extracted from the circular accelerator 1 is transported by the high-energy beam transport system 30 and irradiated to the affected part 52 of the patient 51, thereby performing treatment of a lesion such as cancer.

[0038] The rear section of the high-energy beam delivery system 30 is a rotating gantry 50, which rotates around the patient 51, thereby enabling beam irradiation from multiple different directions.

[0039] An irradiation nozzle 53 is provided on the straight section at the lowest end of the rotating frame 50. The irradiation nozzle 53 shapes the beam from the circular accelerator 1 according to the shape of the affected area 52.

[0040] The electromagnets and other equipment that constitute the high-energy beam delivery system 30 and the rotating frame 50 are connected to the control device 40 in the same way as the circular accelerator 1.

[0041] In particle beam therapy, the distance the beam travels within the patient's body (hereinafter referred to as the range) is controlled by the energy of the beam irradiated onto the patient 51.

[0042] The control device 40 controls the circular accelerator 1 based on information about the irradiation position and irradiation amount of the beam pre-prepared for each patient 51 (hereinafter referred to as the treatment plan), adjusting the energy of the beam emitted from the circular accelerator 1 to a value corresponding to the depth of the affected area 52. The control device 40 controls the first deflecting electromagnet 21, the second deflecting electromagnet 22, the high-energy beam delivery system 30, and the rotating gantry 50 based on the treatment plan, irradiating the affected area 52 with the beam emitted from the circular accelerator 1.

[0043] Next, use Figure 2 The structure of the circular accelerator will be explained. Figure 2 This diagram shows an outline of the circular accelerator 1 of this embodiment, and in particular a schematic diagram of the beam trajectory adjustment device of the circular accelerator 1 mounted on the outside of the main body 10.

[0044] like Figure 2 As shown, the circular accelerator 1 includes magnetic poles 11, coils 12, an ejection magnetic field generating device 13, and a magnetic yoke 14, with an ejection port 15 formed on the magnetic yoke 14. When a predetermined current flows through the coils 12, a magnetic field (hereinafter referred to as the main magnetic field) is generated between the magnetic poles 11 to cause the beam to circulate within the circular accelerator 1, forming a circular orbit 16 around the beam on the orbital plane. The higher the kinetic energy (hereinafter simply referred to as energy) of the beam particles, the larger the radius of the orbit 16 around the beam.

[0045] In the circular accelerator 1 of this embodiment, the closed-loop orbit of each energy of the beam is eccentric. More specifically, the higher the energy, the further away the center of the orbit 16 around the beam is from the exit magnetic field generating device 13, and an orbit convergence region 17 is formed near the exit magnetic field generating device 13, where the orbits around the beam 16 with different energies converge in a narrow area. By forming the orbit convergence region 17, the circular accelerator 1 can emit beams with different energies from a common exit port 15 without changing the strength of the main magnetic field.

[0046] The emitted magnetic field generating device 13 deflects the beam entering it and guides it to the exit outlet 15. The emitted magnetic field generating device 13 is constructed, for example, by a diaphragm coil formed along the beam track. The diaphragm coil is configured such that the direction and amount of beam deflection can be adjusted according to energy by changing the current flowing through the coil. Furthermore, while this embodiment describes an example of an emitted magnetic field generating device 13 constructed with a diaphragm coil, a magnetic field correction structure component (hereinafter referred to as a magnetic channel) made of a magnetic material such as iron can be arranged along the beam track instead of a diaphragm coil. The magnetic channel does not require a power source for excitation, but on the other hand, the generated magnetic field is constant and does not depend on the energy of the beam. Alternatively, both a diaphragm coil and a magnetic channel can be configured to construct the emitted magnetic field generating device 13.

[0047] A first deflecting electromagnet 21 and a second deflecting electromagnet 22 are provided downstream of the ejection port 15 of the circular accelerator 1. The track control device 18 of this embodiment includes the first deflecting electromagnet 21, the second deflecting electromagnet 22, power supplies 23 and 24, and a control unit 40a (preferably part of the control device 40). The first deflecting electromagnet 21 is connected to the power supply 23, and the second deflecting electromagnet 22 is connected to the power supply 24. The control unit 40a controls the excitation current for energizing the first deflecting electromagnet 21 by controlling the power supply 23. Furthermore, the control unit 40a controls the excitation current for energizing the second deflecting electromagnet 22 by controlling the power supply 24.

[0048] The first deflecting electromagnet 21 deflects the beam away from the center of the magnetic pole 11, i.e., the outer periphery of the circular accelerator 1, while the second deflecting electromagnet 22 deflects the beam closer to the center of the magnetic pole 11, i.e., the inner periphery of the circular accelerator 1.

[0049] In this embodiment, such as Figure 1 As shown, the diameter of the first deflecting electromagnet 21 is larger than the diameter of the second deflecting electromagnet 22 and the diameters of the deflecting electromagnets 50a, 50b, and 50c constituting the high-energy beam delivery system 30.

[0050] In addition, such as Figure 1As shown, the second deflection electromagnet 22 has a smaller diameter than the first deflection electromagnet 21, but has a larger diameter than the deflection electromagnets 50a, 50b, 50c that constitute the high-energy beam transport system 30. In addition, the diameter of the second deflection electromagnet 22 need not be smaller than the diameter of the first deflection electromagnet 21, nor need it be larger than the diameters of the deflection electromagnets 50a, 50b, 50c. It can be the same diameter as the first deflection electromagnet 21, or the same diameter as the deflection electromagnets 50a, 50b, 50c. In the case where the diameter of the second deflection electromagnet 22 is the same as the diameters of the first deflection electromagnet 21 or the deflection electromagnets 50a, 50b, 50c, since they are standardized, the second deflection electromagnet need not be manufactured as a dedicated standard, and cost reduction can be achieved.

[0051] In addition, the diameter of the vacuum duct (omitted for the sake of illustration) disposed inside the deflection electromagnet tends to be the same as the diameter of the deflection electromagnet. For example, the diameter of the vacuum duct in the portion in which the first deflection electromagnet 21 is disposed is larger than the diameters of the vacuum ducts in the portions in which the second deflection electromagnet 22 and the deflection electromagnets 50a, 50b, 50c are disposed.

[0052] A high-energy beam transport system 30 that transports the beam to an irradiation target is formed on the downstream side of the second deflection electromagnet 22, and a profile monitor 31, 32 that measures the position and shape of the beam in a plane perpendicular to the direction of travel of the beam is disposed in the straight portion of the high-energy beam transport system 30 that is connected only to the downstream side of the second deflection electromagnet 22. In addition, the location at which the profile monitor that measures the position and inclination of the beam is disposed is not limited to within the high-energy beam transport system 30, but can be disposed in another location, such as within the orbit control device 18.

[0053] The first deflection electromagnet 21 is connected to a power supply 23, and the second deflection electromagnet 22 is connected to a power supply 24. The power supply 23, the power supply 24, the circular accelerator 1, and the profile monitor 31 are connected to a control device 40.

[0054] A method for providing an accelerator system that is capable of irradiating a large current and high-quality beam at low cost by the circular accelerator 1 of the present embodiment will be described.

[0055] The circular accelerator 1 of the present embodiment is capable of emitting beams having different energies from the common beam exit 15 without changing the strength of the main magnetic field. However, the orbit of the beam at the beam exit 15 can differ according to the energy within the range that can pass through the beam exit 15.

[0056] The reason for the deviation of the beam orbit at the exit port 15 is that, for example, the septum coil constituting the exit magnetic field generating device 13 cannot generate a magnetic field of sufficient strength, or the magnetic field generated by the magnetic channel is constant regardless of the energy. The degree of the insufficiency of the magnetic field strength of the septum coil depends on the design of the cyclotron 1, but in the case where the main magnetic field of high strength (for example, about 2.5 T) is generated for the purpose of miniaturization of the cyclotron 1, the insufficiency of the magnetic field strength of the septum coil becomes a problem.

[0057] In addition, in the case where the exit magnetic field generating device 13 is constituted by the magnetic channel, the beam orbit at the exit port 15 varies depending on the energy regardless of the design of the cyclotron 1.

[0058] In the case where the high-energy beam transport system is connected immediately after the exit port 15, the constituent devices of the high-energy beam transport system 30, such as the electromagnets such as the deflection electromagnets 50a, 50b, 50c, the quadrupole electromagnets, and the measuring devices such as the profile monitors 31, 32, need to be designed to be large enough to pass the beam of all energies inside. Thus, in the accelerator system using the existing cyclotron, the installation area and the production cost of the high-energy beam transport system can increase.

[0059] Therefore, in the cyclotron 1 of the present embodiment, the first deflection electromagnet 21 and the second deflection electromagnet 22 are provided on the downstream side of the exit port 15, and the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 are controlled so that the orbits of the beams of different energies coincide on the downstream side of the second deflection electromagnet 22. Thus, in the cyclotron 1 of the present embodiment, it is possible to prevent the expansion of the beam passing region in the high-energy beam transport system 30, and to achieve the purpose of suppressing the size of the devices constituting the high-energy beam transport system 30.

[0060] In addition, the excitation amount of the electromagnet indicates the strength of the magnetic field generated by the electromagnet, and is generally proportional to the current flowing through the coil constituting the electromagnet. The current flowing through the coil of the first deflection electromagnet 21 is controlled by the power supply 23, and the current flowing through the coil of the second deflection electromagnet 22 is controlled by the power supply 24.

[0061] Next, the method of making the orbits of the beams of different energies coincide in the high-energy beam transport system 30 using the first deflection electromagnet 21 and the second deflection electromagnet 22 will be described.

[0062] A magnetic field that deflects the beam toward the inner circumferential side of the cyclotron 1 is generated inside the cyclotron 1, and therefore at the exit port 15, the more the energy of the beam, the more the orbit of the beam is located on the outer circumferential side, and the orbits differ depending on the energy.

[0063] In the case where the high-energy beam transport system is connected immediately after the exit port 15, Figure 2In this embodiment, the orbit 25 represents a designed beam orbit (hereinafter referred to as a designed orbit) of the maximum energy (hereinafter referred to as the highest energy) of the beam emitted from the circular accelerator 1, and the orbit 26 represents an example of a beam orbit of an energy lower than the highest energy. In this way, the orbit of the beam emitted from the circular accelerator 1 differs depending on the energy, and thus the strength of the deflection magnetic field generated by the first deflection electromagnet 21 and the second deflection electromagnet 22 needs to be controlled in accordance with the energy of the beam emitted from the circular accelerator 1, and the amount by which the first deflection electromagnet 21 and the second deflection electromagnet 22 deflect the beam needs to be made to differ depending on the energy of the beam.

[0064] On this basis, in the control section 40a of the control device 40, in the case where the energy of the emitted beam is the designed maximum energy of the circular accelerator 1, both the first deflection electromagnet 21 and the second deflection electromagnet 22 are excited to deflect the beam. At this time, it is preferable that, in the case where the energy of the emitted beam is the designed minimum energy of the circular accelerator 1, both the first deflection electromagnet 21 and the second deflection electromagnet 22 are excited to deflect the beam.

[0065] Here, the first deflection electromagnet 21 deflects the beam in the outward peripheral direction, and the second deflection electromagnet 22 deflects the beam in the inward peripheral direction, and the strength of the magnetic field generated by the first deflection electromagnet 21 and the second deflection electromagnet 22 is controlled so that the beam orbit 26 of each energy at the exit of the second deflection electromagnet 22 coincides with the designed orbit 25 in the case where the energy of the beam is the designed maximum value.

[0066] The designed value of the excitation amount of the first deflection electromagnet 21 and the designed value of the excitation amount of the second deflection electromagnet 22 at the highest energy are not 0, and the designed orbit 25 of the highest energy is bent by the first deflection electromagnet 21 and the second deflection electromagnet 22. In the circular accelerator 1 of the present embodiment, the beam orbits of the energies lower than the highest energy are bent more than the designed orbit 25 of the highest energy, so as to coincide with the designed orbit 25 of the highest energy within the high-energy beam transport system 30.

[0067] The excitation amount of the first deflection electromagnet 21 and the excitation amount of the second deflection electromagnet 22 are determined in a tuning operation (hereinafter referred to as beam tuning) performed before the circular accelerator 1 is supplied with a particle beam for beam irradiation such as particle beam therapy.

[0068] In the case of tuning the beam orbit 26 of an energy lower than the highest energy, the control device 40 controls the circular accelerator 1 so that the energy of the beam emitted from the circular accelerator 1 becomes a target value.

[0069] Further, the control device 40 controls the power supplies 23, 24 to set the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 to the designed values at the energy to be adjusted. The designed values of the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 are derived in advance by analysis of the beam orbit using a computer or the like.

[0070] The position and the inclination of the beam in the high-energy beam transport system 30 are measured using the profile monitors 31, 32. The magnetic field generated by the circular accelerator 1 has a deviation from the designed value due to manufacturing errors of the poles 11 or the like, and thus the position and the inclination of the beam in the high-energy beam transport system 30 are not always consistent with the designed values in the initial state.

[0071] Therefore, in the circular accelerator 1 of the present embodiment, the beam position and the inclination of the beam are measured by the profile monitors 31, 32, the deviation from the designed values is measured, and the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 are adjusted so that the beam position and the inclination of the beam are consistent with the designed values.

[0072]

[0073] Further, it is possible to find out whether the beam orbit at the beam exit 15 deviates toward the inner periphery or the outer periphery by the measurement by the profile monitors 31, 32 in the high-energy beam transport system 30. Specifically, by finding out the position and the inclination of the beam in the high-energy beam transport system 30, it is possible to determine whether the beam orbit at the beam exit 15 deviates toward the inner periphery or the outer periphery from the designed orbit 25.

[0074] The amount of change in the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 and the amount of change in the position and the inclination of the beam in the high-energy beam transport system 30 are in a linear relationship, and thus the amount of adjustment of the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 can be easily found out from the measurement results of the beam position and the inclination. The amount of change in the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 can be derived by the control device 40 based on the measurement results of the beam position and the inclination, or can be calculated separately by an adjuster of the circular accelerator 1 from the measurement results of the beam position and the inclination and input to the control device 40.

[0075] ​After adjusting the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22, the position and the inclination of the beam in the high-energy beam transport system 30 are measured again, and it is confirmed that the beam orbit coincides with the design orbit 25 of the highest energy. In the case where there is an inadmissible deviation between the beam orbit and the design orbit 25 of the highest energy at this stage, the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 are adjusted again in the same order. The adjustment results of the excitation amounts are stored in the control device 40, and the first deflection electromagnet 21 and the second deflection electromagnet 22 are excited on the basis of the adjustment results at the time of actually performing the beam irradiation of the cyclotron 1.

[0076] Next, the method of adjusting the beam orbit of the highest energy in the cyclotron 1 of the present embodiment will be described.

[0077] In the present embodiment, adjustment is performed so that the beam orbits 26 of the respective energies within the high-energy beam transport system 30 coincide with the design orbit 25 of the highest energy, but the deviation from the design orbit 25 due to the influence of the magnetic field error and the like is also predicted for the beam orbit of the highest energy itself, and thus adjustment of the beam orbit is required for the highest energy as well as for the other energies.

[0078] In the case where the beam orbit of the highest energy at the beam exit 15 is located on the inner periphery side than the design orbit 25, the beam orbit can be deflected to the outer periphery side by setting the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 to values higher than the design values, so that the beam orbit of the highest energy coincides with the design orbit 25.

[0079] On the contrary, in the case where the beam orbit of the highest energy at the beam exit 15 is located on the outer periphery side than the design orbit 25, the beam orbit of the highest energy can coincide with the design orbit 25 by setting the excitation amounts of the first deflection electromagnet 21 and the second deflection electromagnet 22 to values lower than the design values.

[0080] Next, the effects of the present embodiment will be described.

[0081] The circular accelerator 1 of the particle therapy system 100 of Embodiment 1 of the present application described above is a circular accelerator that accelerates a beam of charged particles orbiting in a magnetic field in a manner that the closed orbit of each energy of the beam is decentered, and includes a beam exit port that emits beams of different energies from the closed orbit, first and second deflection electromagnets 21 and 22 that deflect the beams emitted from the beam exit port, and a control section 40a that controls the excitation amounts of the first and second deflection electromagnets in accordance with the energy of the emitted beam, the control section 40a causing the first and second deflection electromagnets 21 and 22 to be excited to deflect the beam when the energy of the emitted beam is the maximum energy on the design of the circular accelerator 1. In addition, the diameter of the first deflection electromagnet 21 can be made larger than the diameters of the deflection electromagnets 50a, 50b, and 50c that constitute the high-energy beam transport system 30.

[0082] Thus, in the circular accelerator 1 of the present embodiment, the design values of the excitation amounts of the first and second deflection electromagnets 21 and 22 with respect to the design orbit 25 of the highest energy are set to values other than 0, and therefore even when the beam orbit of the highest energy at the exit port 15 is located on the outer circumferential side than the design value, the beam orbit of the highest energy can be made to coincide with the design value. Thus, in the circular accelerator 1 of the present embodiment, the beam orbit in the high-energy beam transport system 30 can be effectively corrected, and the enlargement of the devices that constitute the high-energy beam transport system 30 can be prevented, and the manufacturing cost of the accelerator system can be suppressed.

[0083] In addition, the circular accelerator 1 of the present embodiment can emit beams of different energies from the common exit port 15 because the closed orbits of the beams of different energies are decentered. Thus, the circular accelerator 1 does not need to provide an energy absorber in the high-energy beam transport system when changing the energy of the irradiation beam, and therefore can prevent the increase in the size of the irradiation beam due to scattering with the energy absorber, and can emit a beam of high irradiation quality. Also, in the circular accelerator 1, the strength of the main magnetic field does not need to be changed in order to change the energy of the beam to be emitted, and therefore the beam can be continuously emitted from the circular accelerator 1, and a higher beam current can be obtained. In particular, the size of the beam irradiated to the patient 51 can be suppressed from increasing, and high-precision irradiation can be performed in a scanning irradiation method in which the beam is three-dimensionally scanned over the affected part 52. Also, the circular accelerator 1 of the present embodiment can irradiate a beam of a large current regardless of the energy of the beam, and therefore can complete treatment in a shorter time than in the past in particle therapy, and can further reduce the burden on the patient.

[0084] In the circular accelerator 1 of the present embodiment, the design orbit 25 of the highest energy is bent by the first deflection electromagnet 21 and the second deflection electromagnet 22, i.e., the design value of the excitation amount of these deflection electromagnets corresponding to the highest energy is a value other than 0. According to this feature, the circular accelerator 1 can correct the beam orbit of the highest energy even in a case where the beam orbit before the beam adjustment of the highest energy is located on the outer circumferential side than the design orbit 25, and can suppress the expansion of the beam passing region in the high-energy beam transport system 30.

[0085] According to the particle ray therapy system 100 of the present embodiment, it is possible to provide an accelerator system that can irradiate a high-current and high-quality beam and is low in cost.

[0086] In addition, since the diameter of the second deflection electromagnet 22 is smaller than the diameter of the first deflection electromagnet 21, it is possible to achieve a reduction in the manufacturing cost thereof.

[0087] Further, the strength of the magnetic field generated by the first deflection electromagnet 21 and the second deflection electromagnet 22 is controlled so that the beam orbit 26 of each energy at the exit of the second deflection electromagnet 22 coincides with the design orbit 25 in a case where the energy of the beam is the maximum value in design, and it is possible to reduce the passing region of the beam in the high-energy beam transport system and reduce the cost of the accelerator system.

[0088] The circular accelerator 1 of the present embodiment accelerates the charged particle beam circulating in the magnetic field in a manner that the closed orbit of the beam of each energy is eccentric, and ejects and guides the accelerated beam from the closed orbit to the ejection exit 15. The beam orbit after being ejected from the ejection exit 15 becomes a different orbit depending on the energy of the beam, but as in the present embodiment, a plurality of deflection electromagnets are provided at a position on the downstream side of the ejection exit 15 of the circular accelerator 1 and on the upstream side of the high-energy beam transport system 30, and the excitation amount of these deflection electromagnets is controlled depending on the energy of the beam, so that it is possible to make the beam orbit substantially uniform within the high-energy beam transport system 30. Therefore, it is possible to miniaturize the particle ray therapy system. In particular, in a case where the ejection magnetic field generating device 13 is constituted by a magnetic channel, the magnetic field generated by the magnetic channel is constant, so the beam orbit after being ejected from the ejection exit 15 becomes a substantially different orbit depending on the energy of the beam, and it is possible to obtain an effect of further miniaturizing the particle ray therapy system.

[0089] In addition, in the present embodiment 1, the embodiments 2 and 3 to be described later, a case where the deflection electromagnets constituting the orbit control device 18, 18A, 18B are two (the first deflection electromagnet and the second deflection electromagnet) is described, but the number of deflection electromagnets provided in the orbit control device provided between the exit side of the main body of the circular accelerator and the high-energy beam transport system can be more than two, and is not particularly limited.

[0090] Embodiment 2

[0091] Using Figure 3 A circular accelerator and a particle beam therapy system according to Embodiment 2 of the present application will be described. Figure 3 A schematic view showing a circular accelerator 1A according to the present embodiment.

[0092] Figure 3 The circular accelerator 1A according to the present embodiment shown in the drawing has substantially the same structure as the circular accelerator 1 described in Embodiment 1, and differs from Embodiment 1 in that the orbit control device 18A of the example is provided with a first deflection electromagnet 61, a second deflection electromagnet 62, power supplies 63, 64, and a control section 40a1 (preferably, a part of the control device 40A), and the first deflection electromagnet 61 and the second deflection electromagnet 62 deflect the beam in both the outer peripheral direction and the inner peripheral direction of the circular accelerator 1A.

[0093] The power supply 63 that excites the first deflection electromagnet 61 and the power supply 64 that excite the second deflection electromagnet 62 are bipolar power supplies that can switch the direction of the current flowing through the coils that constitute the first deflection electromagnet 61 or the second deflection electromagnet 62 in order to deflect the beam in both directions.

[0094] Next, a method of making the orbits of beams of different energies uniform in the high-energy beam transport system 30 using the first deflection electromagnet 61 and the second deflection electromagnet 62 will be described.

[0095] In the present embodiment, the strength of the magnetic field generated by the first deflection electromagnet 61 and the second deflection electromagnet 62 is controlled so that the beam orbits of each energy at the exit of the second deflection electromagnet 62 coincide with the design orbit 65 in the case where the beam orbits of each energy are greater than the minimum value and less than the maximum value of the design orbit 65.

[0096] For example, an energy that becomes a reference (reference energy) is determined between the minimum energy (hereinafter, referred to as the lowest energy) and the maximum energy of the beams emitted from the circular accelerator 1, and the excitation amount of the first deflection electromagnet 61 and the second deflection electromagnet 62 is controlled so that the beam orbits of each energy in the high-energy beam transport system 30 coincide with the design orbit 65 of the reference energy.

[0097] At this time, the first deflection electromagnet 61 deflects the beam of the lowest energy (orbit 66) in the outer peripheral direction and deflects the beam of the maximum energy (orbit 67) in the inner peripheral direction. The second deflection electromagnet 62 deflects the beam of the lowest energy in the inner peripheral direction and deflects the beam of the maximum energy in the outer peripheral direction.

[0098] In the beam adjustment, the step of adjusting the excitation amount of the first deflection electromagnet 61 and the second deflection electromagnet 62 using the profile monitors 31, 32 in the high-energy beam transport system 30 is the same as that of Embodiment 1.

[0099] The other structures and operations are substantially the same as those of the circular accelerator 1 and the particle beam therapy system of Embodiment 1 described above, and detailed description is omitted.

[0100] In the circular accelerator 1A and the particle beam therapy system of Embodiment 2 of the present application, the directions in which the first deflection electromagnet 61 and the second deflection electromagnet 62 deflect the beam are different between the minimum energy and the maximum energy, and thus the beam orbit in the high-energy beam transport system 30 can be effectively corrected as in Embodiment 1. For example, in the case where the beam orbit 67 before adjustment of the maximum energy is located on the outer peripheral side than the designed orbit 65 of the maximum energy, the excitation amount of the first deflection electromagnet 61 and the second deflection electromagnet 62 is weakened than the designed value, and thus the beam orbit 67 can be made to coincide with the designed orbit 65.

[0101] Further, the power supply 63 that excites the first deflection electromagnet 61 and the power supply 64 that excites the second deflection electromagnet 62 are constituted by a power supply that can switch the polarity of the direction of the current flowing in the coil constituting the first deflection electromagnet 61 or the second deflection electromagnet 62, and thus the magnetic field strength of the deflection electromagnet can be further reduced.

[0102] Further, the strength of the magnetic field generated by the first deflection electromagnet 61 and the second deflection electromagnet 62 is controlled so that the beam orbit of each energy at the exit of the second deflection electromagnet 62 coincides with the designed orbit 65 in the case where the beam orbit is larger than the minimum value and smaller than the maximum value of the designed orbit 65, and thus in the circular accelerator 1A of the present embodiment, only the beam orbit 66 of the minimum energy is deflected to the position of the designed orbit 65 of the reference energy, and the maximum value of the excitation amount of the first deflection electromagnet 61 and the second deflection electromagnet 62 can be reduced as compared with Embodiment 1 in which the beam is deflected to the position of the designed orbit 65 of the maximum energy. On the contrary, even in the case where the maximum value of the excitation amount of these deflection electromagnets is the same as that of Embodiment 1, the length of the traveling direction (hereinafter referred to as the pole length) of the first deflection electromagnet 61 and the second deflection electromagnet 62 can be shortened, and the accelerator system can be downsized in the present embodiment.

[0103] <Embodiment 3>

[0104] Use Figure 4 Embodiment 3 of the present application will be described. Figure 4 is a schematic view of the circular accelerator 1B of the present embodiment.

[0105] Figure 4 The circular accelerator 1B of the present embodiment shown basically has the same structure as the circular accelerator 1 described in Embodiment 1, and differs from Embodiment 1 in that the orbit control device 18B of the example is provided with the first deflection electromagnet 21, the second deflection electromagnet 22, the quadrupole electromagnet 71, the power supplies 23, 24, 72, and the control section 40a2 (preferably, a part of the control device 40B), and the quadrupole electromagnet 71 is provided on the downstream side of the first deflection electromagnet 21 and on the upstream side of the second deflection electromagnet 22.

[0106] The quadrupole electromagnet 71 is connected to the power supply 72, and the power supply 72 is connected to the control device 40. As with the first deflection electromagnet 21 and the second deflection electromagnet 22B, the excitation amount of the quadrupole electromagnet 71 is controlled by the control device 40 via the power supply 72.

[0107] In the circular accelerator 1B of the present embodiment, the orbit control device 18B is configured to have the quadrupole electromagnet 71 to converge the passing beam in the horizontal direction and the vertical direction. The beam emitted from the circular accelerator 1 gradually expands in the horizontal direction and the vertical direction, but by providing the quadrupole electromagnet 71 as in the present embodiment, the expansion of the beam size on the downstream side of the quadrupole electromagnet 71 can be suppressed. Thus, the beam loss due to the collision of the beam with the second deflection electromagnet 22, the vacuum duct, and the like can be prevented. In addition, the circular accelerator 1B of the present embodiment is a structure provided with the quadrupole electromagnet 71 on the downstream side of the first deflection electromagnet 21 and on the upstream side of the second deflection electromagnet 22, and thus the beam after passing through the first deflection electromagnet 21 can be converged in the horizontal direction or the vertical direction using the quadrupole electromagnet 71, the expansion of the beam size at the second deflection electromagnet 22B is suppressed, the second deflection electromagnet 22B can be further downsized, and the production cost of the second deflection electromagnet 22B can be reduced.

[0108] In addition, in the circular accelerator 1B of the present embodiment, the excitation amount of the quadrupole electromagnet 71, that is, the strength of the magnetic field generated, is adjusted according to the energy of the beam.

[0109] The other structures and operations are substantially the same as those of the circular accelerator 1 and the particle beam therapy system of Embodiment 1 described above, and detailed description is omitted.

[0110] In the circular accelerator 1B and the particle beam therapy system of Embodiment 3 of the present application, substantially the same effects as those of the circular accelerator 1 and the particle beam therapy system of Embodiment 1 described above can also be obtained.

[0111] In the circular accelerator 1B of the present embodiment, the quadrupole electromagnet 71 is provided on the upstream side of the second deflection electromagnet 22B, whereby it is possible to reduce the energy dependence of the beam size in the high-energy beam transport system 30, and it is possible to simplify the beam adjustment after the high-energy beam transport system 30.

[0112] In the circular accelerator 1B of the present embodiment, the quadrupole electromagnet 71 is provided on the downstream side of the first deflection electromagnet 21, whereby it is possible to ensure that the beam that has exited from the main body 10 of the circular accelerator 1 is promptly kicked by the first deflection electromagnet 21, the beam orbit is deflected, and it is possible to suppress an increase in the diameter of the second deflection electromagnet 22.

[0113] The circular accelerator 1B of the present embodiment sets the strength of the magnetic field generated by the quadrupole electromagnet 71 to different values in accordance with the energy of the beam, whereby it is possible to more reliably obtain the effect of suppressing an increase in the beam size.

[0114] In the circular accelerator 1B of the present embodiment, an example in which one quadrupole electromagnet is provided between the first deflection electromagnet 21 and the second deflection electromagnet 22B is described, but two or more quadrupole electromagnets can be provided in this region. In the case where a plurality of quadrupole electromagnets are provided between the first deflection electromagnet 21 and the second deflection electromagnet 22B, it is possible to suppress the beam size at the exit of the second deflection electromagnet 22B to be smaller than in the case where only one quadrupole electromagnet is provided.

[0115] In addition, in the present embodiment, an example in which the quadrupole electromagnet 71 is provided on the downstream side of the first deflection electromagnet 21 is described, but the location at which the quadrupole electromagnet 71 is provided is not limited to this, and it can be configured so that one or more quadrupole electromagnets are provided on the upstream side of the first deflection electromagnet 21.

[0116] Furthermore, the quadrupole electromagnet 71 of the present embodiment can also be applied to Embodiment 2. That is, it can be configured so that the track control device of Embodiment 2 is provided with one or more quadrupole electromagnets on the upstream side of the second deflection electromagnet 62. Furthermore, it is preferable that one or more quadrupole electromagnets are also provided on the downstream side of the first deflection electromagnet 61 of Embodiment 2.

[0117] <Other>

[0118] Furthermore, the present application is not limited to the above-described embodiments, and includes various modifications. The above-described embodiments are embodiments that are described in detail in order to easily understand the present application, and are not limited to necessarily having all of the structures described.

[0119] In addition, a part of the structure of one embodiment can be replaced with that of another embodiment, and a part of the structure of one embodiment can be added with that of another embodiment. In addition, a part of the structure of one embodiment can be deleted, replaced, or added with that of another embodiment.

Claims

1. A circular accelerator that accelerates a beam of charged particles orbiting in a magnetic field in such a way that the closed-loop orbit of each energy of the beam is deflected, the circular accelerator being characterized by comprising: A beam exit point, from which beams of different energies are emitted from the closed-loop orbit; A first deflecting electromagnet and a second deflecting electromagnet deflect the beam exiting the beam; and The control unit controls the excitation amount of the first deflecting electromagnet and the second deflecting electromagnet based on the energy of the emitted beam. Regarding the control unit, When the energy of the emitted beam is the maximum energy designed for the circular accelerator, both the first deflecting electromagnet and the second deflecting electromagnet are energized to deflect the beam. The first deflecting electromagnet and the second deflecting electromagnet are disposed on the downstream side of the beam exit. The control unit controls the excitation amount of the first deflecting electromagnet and the second deflecting electromagnet so that the trajectories of beams with different energies are aligned on the downstream side of the second deflecting electromagnet.

2. The circular accelerator according to claim 1, characterized in that, Regarding the control unit, When the energy of the emitted beam is the minimum energy designed for the circular accelerator, both the first deflection electromagnet and the second deflection electromagnet are energized to deflect the beam.

3. The circular accelerator according to claim 1, characterized in that, The strength of the magnetic field generated by the first deflecting electromagnet and the second deflecting electromagnet is controlled such that the trajectory of each energy beam at the exit of the second deflecting electromagnet is consistent with the designed trajectory when the energy of the beam is at the maximum designed value.

4. The circular accelerator according to claim 1, characterized in that, The first power supply for energizing the first deflecting electromagnet and the second power supply for energizing the second deflecting electromagnet are both bipolar power supplies. The bipolar power supply can switch the direction of the current flowing through the coils constituting the first deflecting electromagnet or the second deflecting electromagnet.

5. The circular accelerator according to claim 4, characterized in that, The strength of the magnetic fields generated by the first deflecting electromagnet and the second deflecting electromagnet is controlled such that the trajectory of each energy beam at the exit of the second deflecting electromagnet is consistent with the designed trajectory when the energy of the beam is greater than the designed minimum value and less than the designed maximum value.

6. The circular accelerator according to claim 1, characterized in that, It also includes: one or more four-pole electromagnets disposed upstream of the second deflecting electromagnet.

7. The circular accelerator according to claim 6, characterized in that, The quadrupole electromagnet is located downstream of the first deflection electromagnet.

8. The circular accelerator according to claim 6, characterized in that, The strength of the magnetic field generated by the quadrupole electromagnet is set to different values ​​according to the energy of the beam.

9. A particle beam therapy system, characterized in that, have: The circular accelerator according to any one of claims 1 to 8.

10. A particle beam therapy system, characterized in that, have: The circular accelerator as claimed in any one of claims 1 to 8; A beam delivery system that delivers the beam emitted from the circular accelerator; and An irradiation device that irradiates the beam delivered by the beam delivery system. The beam delivery system includes a beam detector that measures the position and tilt of the passing beam. The control unit controls the excitation amount of the first deflection electromagnet and the second deflection electromagnet so that the beam trajectory calculated based on the position and inclination of the beam becomes the designed beam trajectory.

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