JP2009172261A - Charged particle beam irradiation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problem: when an irradiation angle changes by rotation of a gantry, disposition of a γ-ray detector cannot be appropriate, so that an irradiation field cannot be measured precisely. <P>SOLUTION: The charged particle beam irradiation system is provided with: a rotating gantry 12; a charged particle beam generator for generating charged particle beams; an irradiator 21, provided in the rotating gantry 12, for emitting the charged particle beams to an object to be irradiated; and a γ-ray detector 46 for detecting a prompt γ-ray generated by the object to be irradiated. The rotating gantry 12 is provided with the γ-ray detector 46. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a particle beam irradiation system, and more particularly to a charged particle beam irradiation system that treats a diseased part such as a tumor by irradiating it with a charged particle beam.

  A method of irradiating a patient with cancer or the like with a charged particle beam such as a proton beam is known. The system used for this irradiation includes a charged particle beam generator, a beam transport system, and a treatment room. The charged particle beam accelerated by the charged particle beam generating apparatus reaches the irradiation apparatus in the treatment room through the beam transport system, and the distribution is expanded by the irradiation apparatus to form an irradiation field suitable for the shape of the affected part in the body of the patient. At that time, as a means for confirming that the irradiation field has been formed at a desired position, a method is used in which annihilation gamma rays from positron emitting nuclides generated in the body by irradiation are photographed by positron tomography (PET) after irradiation. Yes. In addition, a method for observing gamma rays (prompt gamma) generated from excited nuclei such as carbon, oxygen, and nitrogen generated in the irradiation field during treatment has been proposed.

JP-A-9-189769 “Prompt gamma measurements for locating the dose falloff region in the proton therapy” APPLIED PHYSICS LETTERS 89, 183517 (2006)

  In the conventional method using PET, since the positron emitting nuclide generated by irradiation moves due to a physiological phenomenon to measure after irradiation, the positron emitted from the positron emitting nuclide moves after several mm and disappears. The generation of gamma rays and the generation of positron-emitting nuclides require a nuclear reaction, but charged particles that reach the deepest position in the irradiation field do not have sufficient energy to cause a nuclear reaction. It was difficult to accurately measure the shape of the irradiation field. In addition, a method for measuring prompt gamma rays has not yet been established. When checking the irradiation field with prompt gamma rays, place the gamma ray measuring device as close to the irradiation field as possible, place the detection surface of the gamma ray detector in a direction perpendicular to the beam axis direction, and draw it from the center of the detection surface of the gamma ray detector. It is preferable to arrange so that the perpendicular line is the deepest part of the irradiation field. In particular, when the irradiation direction is changed using a gantry, it is necessary to arrange the gamma ray detector at an optimum position in the irradiation direction in order to measure with high accuracy, but the method has not been invented yet.

  An object of the present invention is to provide a charged particle beam irradiation system capable of accurately measuring an irradiation field position even when an ion beam is irradiated from a plurality of angles by rotating a gantry.

  The features of the present invention that achieve the above-mentioned objects are a rotating gantry, a charged particle beam generating device that generates a charged particle beam, an irradiation device that is provided in the rotating gantry and emits a charged particle beam to the irradiation target, and an irradiation target And a gamma ray detector for detecting the prompt gamma ray generated from the first gamma ray, and providing the prompt gamma ray detector in the rotating gantry.

  According to the present invention, the irradiation field position irradiated with the ion beam can be accurately measured.

  Hereinafter, a charged particle beam irradiation system which is a preferred embodiment of the present invention will be described.

  The charged particle beam irradiation system of this embodiment includes a charged particle beam generator 1, a beam transport system 2, and a radiation treatment room 40.

  A charged particle beam generator 1 will be described with reference to FIG.

  The charged particle beam generator 1 includes an ion source (not shown), a linac 3 (previous charged particle beam accelerator), and a synchrotron 4. The synchrotron 4 includes a high-frequency application device 5, an acceleration device 6, and a stored charge amount detector 10. The high-frequency application device 5 includes a high-frequency application electrode 7 disposed on the orbit of the synchrotron 4 and a high-frequency application power source 8. The high frequency application electrode 7 and the high frequency application power source 8 are connected by a switch 9. The acceleration device 6 includes a high-frequency accelerating cavity (not shown) disposed in the orbit of the ion beam and a high-frequency power source (not shown) that applies high-frequency power to the high-frequency accelerating cavity. Ions such as protons and carbon are generated in the ion source and are incident on the linac 3 and accelerated. The ion beam emitted from the linac 3 is incident on the synchrotron 4. In the synchrotron 4, the ion beam is accelerated by being given energy by a high frequency power applied to the ion beam from a high frequency power source through a high frequency acceleration cavity. After acceleration to a preset energy, the switch 9 is connected and a high frequency is applied to the ion beam by the high frequency application device 5. The ion beam orbiting within the synchrotron 4 within the stability limit moves outside the stability limit, and is emitted from the synchrotron 4 through the extraction deflector 11. The ion beam emission from the synchrotron 4 is stopped by turning off the switch 9 and stopping the application of the high frequency. The ion beam emitted from the synchrotron 4 is transported to the irradiation device 21 through the beam transport system 2. The beam transport system 2 includes quadrupole electromagnets 14 and 18 and deflection electromagnets 15, 19 and 20.

  A part of the beam transport system 2, the inverted U-shaped portion and the irradiation device 21 are installed in a substantially cylindrical rotating drum of a rotating gantry (hereinafter referred to as a gantry) 12 and can be rotated by a motor (not shown). It is. The ion beam that has passed through the irradiation device 21 is irradiated onto a subject (patient) 101 placed on a couch (irradiation bed) 41 installed inside the rotating drum.

  The irradiation device 21 will be described with reference to FIG.

  The irradiation device 21 includes a beam position detector 22, scanning electromagnets 23 and 24, a scatterer 25, a ridge filter 26, a range shifter 27, a dose detector 28, a collimator 30, a bolus 31, an X-ray generator (X-ray tube) 32, An X-ray rail 33 is used. The two scanning electromagnets 23 and 24 are arranged so as to scan the ion beam in a direction perpendicular to each other in a plane perpendicular to the beam axis, and scan the ion beam in a circle in a plane perpendicular to the beam axis. Here, the beam axis indicates a path along which the ion beam travels when scanning by the scanning electromagnets 23 and 24 is not performed. After scanning by the scanning electromagnets 23 and 24, the ion beam is scattered by the scatterer 25, and the beam diameter is expanded. By appropriately adjusting the size of the beam diameter and the beam scanning radius, the dose distribution in the direction perpendicular to the beam axis can be made uniform. After passing through the scatterer, the ion beam reaches the ridge filter 26. The cross-sectional shape of the ridge filter 26 is wedge-shaped, and the surface corresponding to the hypotenuse has a number of step-like structures. The ion beam absorbs different energy depending on the thickness of the incident step into the ridge filter 26. The ion beam that has passed through the ridge filter 26 loses energy as the step thickness of the ridge filter 26 increases, resulting in a particle number distribution proportional to the step area. The dose distribution in the beam axis direction can be made uniform by adjusting the area of each stage. The ion beam passes through the ridge filter 26 and then reaches the range shifter 27. The range shifter 27 is made of a light material such as ABS, and suppresses ion beam scattering and absorbs energy. The range of the ion beam in the patient 101 is adjusted by adjusting the thickness of the range shifter 27. After passing through the range shifter 27, the ion beam passes through the bolus 31 and the collimator 30. The bolus 31 is created according to the shape of the affected part 102 for each patient. The bolus 31 makes the irradiation field shape formed at the end of the range of the ion beam suitable for the shape of the affected area 102. In addition, the collimator 30 makes the irradiation field shape perpendicular to the beam axis suitable for the shape of the affected area 102. An irradiation field suitable for the affected area 102 of the patient 101 is formed by the devices arranged in the irradiation apparatus 21 described above. The beam position detector 22 is a multi-wire chamber, measures the beam position, and compensates for the position where the incident beam to the irradiation device 21 can make the irradiation field uniform. The dose detector 28 measures the irradiated dose. The X-ray generator 32 has a structure that can be moved to the beam axis position by the X-ray rail 33, and is used when determining the position of the patient 101 before irradiation.

  The structure in the radiation therapy room 40 will be described with reference to FIG.

  In the radiation therapy room 40, there is a cylindrical gantry 12, and the direction of the irradiation device 21 is changed by rotating the gantry 12, and the irradiation device 21 can make a round around the patient 101. The patient 101 is placed on a movable bed called a couch 41 and irradiated. The couch 41 is provided in the radiation treatment room 40, can move in any direction three-dimensionally, and can rotate in three directions. The patient 101 can be irradiated from an arbitrary direction by the rotation of the gantry 12 and the movement of the couch 41. An X-ray support 42 and X-ray detectors (for example, FPD) 44 and 45 protrude from the wall surface of the gantry 12. These are pulled out and used only when necessary, and can be stored in the wall surface of the gantry 12 when unnecessary. By storing it when it is not necessary, the FPDs 44 and 45 can be prevented from being damaged by radiation. Further, collision with the couch 41 can be prevented when the gantry 12 is rotated. The FPD 45 is installed to detect X-rays from the X-ray generator 32 mounted in the irradiation device 21, and the FPD 44 is supplied from the X-ray generator (X-ray tube) 43 mounted on the X-ray support 42. X-rays are detected. In order to confirm the position of the patient 101, it is necessary to photograph the patient 101 from two orthogonal directions. Moreover, since the X-ray generator 32 is in the irradiation device 21, the positions of the collimator 30 and the affected part 102 can be confirmed from the direction of irradiation with the ion beam, and safety can be improved. Since one X-ray generator 32 is arranged in the irradiation device 21, the other X-ray generator 43 is arranged in a direction perpendicular to the beam axis. There is a gamma ray detector 46 next to the X-ray generator 43 on the X-ray support 42. The gamma ray detector 46 is provided on the X-ray support 42.

  The procedure for proceeding with irradiation will be described with reference to FIG.

  For irradiation of cancer or the like, the patient 101 is imaged in advance by the CT device 52, the position of the affected area is specified using the captured image, and the irradiation field including the periphery of the affected area is determined using the treatment planning system 51. In order to form the determined irradiation field, the treatment planning system 51 irradiates the accelerator control unit 54 and the beam transport system control unit 55 in the irradiation control system 53 by the energy of the ion beam accelerated by the synchrotron 4 and the rotation of the gantry 12. An angle is set, and parameters of each device in the irradiation apparatus 21 are set in the irradiation apparatus control unit 56. Further, the treatment planning system 51 designates the position where the affected part 102 should be arranged and the arrangement position of the gamma ray detector 46 with respect to the positioning system 60.

  The positioning system 60 includes an FPD 45 disposed facing the X-ray generator 32 disposed in the nozzle through the X-ray controller 57, an X-ray generator 43 capturing the image perpendicular to the beam axis, and the FPD 44 disposed facing the beam axis. The affected part is imaged using two sets of X-rays, and the couch 41 is moved through the couch control device 59 so that the position of the affected part is arranged at the position designated by the treatment planning system 51. Also, after the bolus 31 and the collimator 30 are installed in the irradiation device 21 and the patient 101 is positioned, the gantry 12 is rotated to the angle specified by the treatment planning system 51, and then the gamma ray detector control device 58 is the treatment planning system. The gamma ray detector 46 is moved to the position designated by 51. The irradiation preparation is completed by the above, and irradiation is started. After the irradiated dose is measured by the dose detector 28 in the irradiation device 21 and the amount designated by the treatment planning system 51 is irradiated, the irradiation is terminated. During irradiation with the ion beam, the gamma ray detector 46 continues to measure gamma rays and transfers the acquired data to the irradiation field confirmation system 61 after the end of irradiation. The irradiation field confirmation system 61 compares the data acquired from the gamma ray detector 46 with the patient position information received from the positioning system 60 and confirms that the affected area 102 is irradiated. In this embodiment, the affected area 102 is positioned by X-ray imaging from two directions. However, X-ray imaging is performed at a plurality of angles while rotating the gantry 12, and positioning is performed by CT to increase accuracy. Can do.

  The shape of the irradiation field is determined by the energy of the ion beam, the equipment in the irradiation device 21 and the composition of the patient. The higher the energy, the deeper the ion beam reaches the patient. When the device does not pass through the device in the irradiation device 21, a dose distribution having a peak at the deepest position where the ion beam reaches within the patient body is formed as shown in FIG. The ridge filter 26 absorbs energy, and ion beams of different energies are mixed at an appropriate ratio, thereby forming a uniform dose region (SOBP) equal to the size of the affected area in the depth direction as shown in FIG. 5B. be able to. Even when SOBP is formed, the dose distribution decreases sharply near the end of the range. The range end position is determined by the energy of the ion beam, the thickness of the range shifter 27, the thickness of the bolus 31, and the amount of material up to the range end in the patient. The shape on the deep side of the irradiation field formed at the end of the range of the ion beam is called the irradiation field deep portion shape. The deepest position of the irradiation field deep portion shape is called the irradiation field deepest portion. The amount of substance from the patient body surface to the affected area in the irradiation direction of the ion beam is calculated from the CT image taken before irradiation, and the energy at the time of irradiation, the thickness of the range shifter 27, and the shape of the bolus 31 are determined based on the data. .

  As described above, when the ion beam forms an irradiation field, the ion beam causes a nuclear reaction with a constituent element in the patient body at a certain rate. Atoms in the irradiation field that have undergone a nuclear reaction transition to an excited state, and then emit gamma rays (prompt gamma rays) to transition to the ground state. The area where the nuclear reaction takes place coincides with the irradiation field, and gamma rays are emitted almost isotropically. The position of the irradiation field can be measured by accurately measuring the gamma rays emitted here and specifying the generation position of the gamma rays.

  In the above process, the constituents in the body are excited, so oxygen, carbon, and nitrogen are mainly excited. Each first excitation energy is in the region of several MeV (1 MeV to 10 MeV). Therefore, most of the energy of the emitted gamma rays is emitted with the same energy (1 MeV to 10 MeV). When gamma rays having an energy of 1 MeV or more react with a substance, the probability of occurrence of a photoelectric absorption reaction is low, and the establishment of occurrence of two reactions of Compton scattering and pair production becomes dominant.

  For the above reasons, a Compton camera using Compton scattering reaction is preferable as the gamma ray detector 46 for measuring the gamma rays. The Compton camera is composed of a first detector 71 and a second detector 72 as shown in FIG. It is assumed that the gamma ray detection surface 73 is a surface far from the second detection unit 72 and that gamma rays are incident from the detection surface 73. The first detector 71 is filled with an inert gas such as xenon, and a high voltage is applied to the detection surface 73. Charge detectors (not shown) are arranged in a lattice pattern near the boundary surface between the first detection unit 71 and the second detection unit 72. In the second detector 72, heavy scintillators such as GSO crystals are arranged in a lattice pattern. When gamma rays are incident, Compton scattering occurs in the first detector 71. The gamma rays lose energy due to scattering, and after reaching the second detector 72, all energy is lost and detected. Recoil electrons scattered by Compton scattering proceed while ionizing the gas in the first detection unit 71. Since a voltage is applied in the first detection unit 71, the ionized electrons travel toward the second detection unit 72 and are detected by the charge detector. The position where the inert gas is ionized by recoil electrons can be specified by measuring the time from when the gamma rays are detected by the second detector 72 until the electrons are detected by the charge detector. The position of Compton scattering and the recoil direction of the recoil electrons can be found from the recoil electron trajectory obtained as described above, and the energy of the recoil electrons can be obtained from the total charge detected by the charge detector. Further, the position and energy of the scattered gamma rays are known from the data of the second detection unit 72. By calculating using the law of conservation of momentum and energy conservation, the direction and energy of incident gamma rays can be determined. The incident gamma rays need to reach the second detector 72 after being Compton scattered by the first detector 71. When the light enters from the end of the detection surface 73, there is a high possibility that the light will come out of the detector before reaching the second detection unit 72, and the detection surface center has the highest detection efficiency. For the same reason as for the incident angle, the detection efficiency is best when it is incident on the detection surface 73 perpendicularly. It should be noted that a semiconductor detector such as Si or CdTe can be used for both the first detector 71 and the second detector 72. By using a semiconductor detector as the first detection unit 71, it is possible to improve the establishment of the reaction at the first detection unit 71 for incident gamma rays. Moreover, the detection position accuracy can be improved by using a semiconductor detector for the second detector 72.

  Details of the arrangement of the gamma ray detector 46 will be described with reference to FIG.

  FIG. 7 is an enlarged view of the vicinity of the gamma ray detector 46 of FIG. Gamma ray detector supports 47 and 48 and a gamma ray detector 46 are disposed at the tip of the X-ray support 42. Box-shaped gamma ray detector supports 47 and 48 are housed in and out of each other, and the gamma ray detector 46 can move in the radial direction of the gantry 12 by moving in the radial direction of the gantry 12. . Since the gamma ray detector 46 detects the position and angle of the gamma ray and identifies the irradiation field position, the irradiation field position measurement accuracy is proportional to the distance between the irradiation field and the gamma ray detector 46. The irradiation field position accuracy can be improved by bringing the gamma ray detector 46 as close as possible to the patient 101. The gamma ray detector 46 can be stored in a gamma ray detector support 48, the gamma ray detector 46 can be stored in a gamma ray detector support 47, and the gamma ray detector support 47 can be stored in an X-ray support 42. When neither the gamma ray detector 46 nor the X-ray generator 43 is required, the X-ray support 42 can be stored in the wall surface of the gantry 12. By being able to be stored on the wall surface, it is possible to prevent a collision with the couch 41 when the gantry 12 is rotated. In this embodiment, the gamma ray detector support has two stages. The number and shape of the steps are determined so that the detection surface of the gamma ray detector 46 can move to at least the rotation center position of the gantry 12. The gamma ray detector 46 is fixed to a gamma ray detector rail 49 installed on a gamma ray detector support 48 and can move in a plane perpendicular to the radial direction of the gantry 12. As described above, since the gamma ray detector 46 has the highest detection sensitivity for gamma rays incident perpendicularly to the center of the detection surface 73, it is preferable that the deepest irradiation field is located near the vertical line drawn from the center of the detection surface. During irradiation, the beam axis is generally located at the center of the affected area, and therefore it is difficult to move the gamma ray detector 46 two-dimensionally within the plane of the gamma ray detector support 48. A structure that can move only in the direction of the beam axis by arranging the perpendicular so as to always intersect the beam axis is sufficient. In order to improve the irradiation field position measurement accuracy, the position accuracy during irradiation of the gamma ray detector 46 is important. Each of the driving mechanisms is provided with a potentiometer and a mechanism for measuring the position where the gamma ray detector 46 is disposed.

  In this embodiment, by arranging the gamma ray detector 46 on the X-ray support 42, a position perpendicular to the beam axis can always be secured. There are other positions where the beam axis can always be kept perpendicular to the position where the FPD 44 of FIG. 3 is arranged and the rotation axis of the gantry 12. If the gamma ray detector 46 is arranged on the support of the FPD 44, the FPD cannot be stored on the wall surface of the gantry 12 during irradiation, and there is a possibility that it is damaged by radiation. In this case, it is preferable that the support is separate from the FPD, and only the FPD during irradiation can be stored on the wall surface of the gantry 12. Further, the gamma ray detectors 46 may be arranged on both sides of the FPD side and the X-ray generator side. By measuring from both sides, the amount of signal can be increased and the measurement system can be improved. As the installation position of the gamma ray detector 46 on the rotation axis of the gantry 12, the side opposite to the wall surface side (couch side) of the gantry 12 can be considered. In many treatments, the patient 101 irradiates in a state almost parallel to the rotation axis of the gantry 12. Therefore, even when the gamma ray detector 46 is arranged on the rotation axis of the gantry 12 for irradiation other than the head, the gamma ray detector 46 is placed on the affected area. Cannot be brought close to each other, and the detection position accuracy cannot be improved. However, there is a case where the couch 41 is rotated and irradiation is performed in a state close to the rotation axis of the gantry 12. In this case, the detection position accuracy can be improved by measuring with the gamma ray detector 46 on the rotation axis of the gantry 12. When installing on the wall surface side of the gantry 12, the structure can be pulled out from the wall surface. Moreover, when arrange | positioning to the couch side, it is set as the structure pulled out from the outer ceiling of the gantry 12. FIG. In many cases, the position of the irradiation field can be measured with high accuracy by the gamma ray detector 46 arranged in the X-ray generator 43. However, by arranging the gamma ray detector 46 on the rotation axis of the gantry 12, irradiation is performed in all cases. The field position can be measured with high accuracy.

  The details of the procedure for the irradiation field confirmation system 61 to confirm the irradiation field will be described.

  The irradiation field confirmation system 61 receives the detection data of the gamma ray detector 46 acquired during irradiation of the ion beam and the position data where the gamma ray detector 46 is arranged via the gamma ray detector control device 58. Further, the irradiation field confirmation system 61 receives information on the rotation angle of the gantry 12 from the beam transport system control unit 55. Based on the detection data of the gamma ray detector 46, the incident angle, position and energy of each incident gamma ray at coordinates specific to the gamma ray detector 46 are calculated. From the result of the calculation, the irradiation field confirmation system 61 extracts only those that are perpendicularly incident on the gamma ray detector 46. Further, since the energy emitted from the nucleus in the excited state is several MeV as described above, those having an energy of 1 MeV or more are extracted. A gamma ray generation distribution in the beam axis direction is obtained from the extracted gamma ray position information, and the position where the distribution sharply decreases is set as the position of the deepest irradiation field. Using the information on the rotation angle of the gantry 12 and the position of the gamma ray detector 46, the obtained position of the deepest irradiation field is converted from the coordinates of the gamma ray detector 46 into a coordinate system unique to the treatment room. This deepest irradiation field position is represented as a plane perpendicular to the beam axis. The irradiation field deep part shape is generally various, and the irradiation field deepest part is not necessarily on the beam axis. Therefore, it is necessary to express the measured result as a surface. Further, the irradiation field confirmation system 61 receives information on the irradiation field planned for treatment from the treatment planning system 51 in a coordinate system unique to the treatment room. The irradiation field confirmation system 61 compares the irradiation field deepest part with the irradiation field shape planned for treatment on the coordinate system unique to the treatment room, and confirms that the irradiation has been completed as planned.

  Further, the shape of the irradiation field deep portion can be obtained by using information of gamma rays incident on the detection surface of the gamma ray detector 46 from a direction other than perpendicular to the detection surface. An angular distribution of gamma rays incident on the gamma ray detector 46 is obtained for each position, and an angle at which the distribution sharply decreases is obtained. The angular distribution can be obtained for each angle using a straight line perpendicular to the detection surface of the gamma ray detector 46 as a rotation axis. By drawing a straight line in the angular direction in which the distribution decreases through the position where the distribution is obtained, the straight line corresponds to the tangent of the irradiation field shape. The field shape can be reconstructed by obtaining this tangent line for each position and angle, and obtaining a curved surface in contact with the tangent line.

  Further, conventionally, in order to confirm that the irradiation device 21 is normal, a water phantom is disposed at the irradiation position, and the range of the ion beam is measured by moving the detector in water and measuring the dose value for each depth position. The end position is measured. It is possible to confirm the normal operation of the apparatus more easily than the conventional method by installing a water phantom at the irradiation position and measuring the end of the range of the ion beam in the same manner as when the patient 101 is irradiated using the gamma ray detector 46. it can.

  Further, by attaching the gamma ray detector 46 to the robot arm, it can be freely arranged in the gantry 12 three-dimensionally. In this case, since the robot arm does not interfere with the couch 41, it is desirable that the robot arm be installed on the ceiling outside the gantry 12.

  In this embodiment, even when the gantry 12 is rotated and the angle of the irradiation device 21 is changed, the gamma ray detector 46 can be arranged in a direction perpendicular to the beam axis. Further, the gamma ray detector 46 can be brought closer to the affected area by the radial movement of the gantry 12. Further, the gamma ray detector 46 can move in a plane perpendicular to the radial direction of the gantry 12. For this reason, even when the gamma ray detector 46 is small, it can be arranged so that the perpendicular drawn from the center of the detection surface of the gamma ray detector 46 is near the deepest part of the irradiation field. Even when irradiating from various angles, the irradiation field position can be measured with high accuracy. Furthermore, the irradiation field can be accurately measured even when the small gamma ray detector 46 is used.

  In this embodiment, since the prompt gamma ray generated by irradiating the irradiation target with the ion beam is detected and the shape of the irradiation field is measured, the irradiation position of the ion beam irradiated to the patient 101 is accurately measured. Can do. Thereby, a highly reliable charged particle beam irradiation system can be provided. In addition, this embodiment can measure with high precision compared with the conventional technique which detects the shape of the irradiation field by detecting annihilation gamma rays.

  In this embodiment, a proton beam or a heavy particle beam (carbon beam or the like) can be used as the ion beam. The present embodiment in which prompt gamma rays are detected and the shape of the irradiation field is measured is particularly effective in the case of a proton beam irradiation system using proton beams.

  This embodiment can detect prompt gamma rays emitted from the irradiation target and collect information necessary for measuring the shape of the irradiation field while irradiating the ion beam. The displacement is small and the shape of the irradiation field can be measured with high accuracy. In addition, the time for measuring the shape of the irradiation field can be shortened, and the throughput is improved.

  In the present embodiment, the irradiation field confirmation system 61 determines that the detection data output from the gamma ray detector 46 has an energy of 1 MeV or more as valid data. The detection data of energy from 1 MeV to 10 MeV may be determined as valid data to confirm the irradiation field. Thereby, the irradiation field can be measured with higher accuracy.

  In this embodiment, the synchrotron 4 is used, but the same effect can be obtained with other accelerators such as a cyclotron.

It is a figure showing the whole schematic structure of the charged particle beam irradiation system which is one suitable embodiment of this invention. 2 is a cross-sectional view illustrating a configuration of an irradiation apparatus provided in the charged particle beam irradiation system illustrated in FIG. 1. It is a conceptual diagram which shows the irradiation chamber with which the charged particle beam irradiation system shown in FIG. 1 is equipped. BRIEF DESCRIPTION OF THE DRAWINGS It is the figure which shows the whole schematic structure of the charged particle beam irradiation system which is one suitable embodiment of this invention, and the block block diagram of a control system. It is a figure which shows the dose distribution obtained when the irradiation object shown in FIG. 1 is irradiated with an ion beam. It is the conceptual diagram which showed the structure of the gamma ray detector. It is a conceptual diagram which shows in detail the gamma ray detector periphery arrange | positioned in the irradiation chamber of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charged particle beam generator 2 Beam transport system 3 Linac 4 Synchrotron 5 High frequency application device 6 Acceleration device 7 High frequency application electrode 8 High frequency application power source 9 Switch 11 Deflector for extraction 12 Gantry 14, 18 Quadrupole electromagnets 15, 19, 20 Deflection electromagnet DESCRIPTION OF SYMBOLS 21 Irradiation device 22 Beam position detector 23, 24 Scanning electromagnet 25 Scattering body 26 Ridge filter 27 Range shifter 28 Dose detector 30 Collimator 31 Bolus 32, 43 X-ray generator 33 X-ray rail 40 Treatment room 41 Couch 42 X-ray support Body 44, 45 FPD
46 Gamma-ray detectors 47 and 48 Gamma-ray detector support 49 Gamma-ray detector rail 51 Treatment planning system 52 CT apparatus 53 Irradiation control system 54 Accelerator controller 55 Beam transport controller 56 Irradiator controller 57 X-ray controller 58 Gamma ray Detector control device 59 Couch control device 60 Positioning system 61 Irradiation field confirmation system 71 First detection unit 72 Second detection unit 73 Detection surface 101 Patient 102 Affected site

Claims (8)

With rotating gantry,
A charged particle beam generator for generating a charged particle beam;
An irradiation device provided in the rotating gantry for emitting the charged particle beam to an irradiation target;
A gamma ray detector for detecting prompt gamma rays generated from the irradiation object,
A charged particle beam irradiation system, wherein the prompt gamma ray detector is provided in the rotating gantry.   The charged particle beam irradiation system according to claim 1, wherein the gamma ray detector is disposed on a structure that can be pulled out from a wall surface of the rotating gantry.   The charged particle beam irradiation system according to claim 2, wherein an X-ray generator for generating X-rays is installed in the structure.   The charged particle beam irradiation system according to claim 2, wherein the gamma ray detector moves in a radial direction of the rotating gantry.   The charged particle beam irradiation system according to claim 2, wherein the gamma ray detector moves in a beam axis direction.   The charged particle beam irradiation system according to claim 2, wherein the gamma ray detector moves in a plane perpendicular to a radial direction of the gantry.   The charged particle beam irradiation system according to any one of claims 1 to 6, wherein the energy of the prompt gamma ray is 1 MeV to 10 MeV.   The charged particle beam irradiation system according to claim 1, wherein the charged particle beam is a proton beam.

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