JP2015073827A - Charged particle beam treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charged particle beam treatment device capable of accurately radiating a charged particle beam with a desired dose distribution.SOLUTION: A charged particle beam treatment device 1 comprises: a radiation nozzle 8 for radiating a charged particle beam R; a degrader 30 which is provided in the radiation nozzle 8, is configured by a first absorber 31 to fourth absorber 34 for reducing energy of the charged particle beam R, and adjusts a range of the charged particle beam R according to a used combination of the absorbers; a drive unit 40 for moving the degrader 30 in a radiation axis direction of the charged particle beam R; and a control unit 7 for controlling the drive unit 40 so that the degrader 30 moves in the radiation axis direction of the charged particle beam R according to the used combination of the first absorber 31 to fourth absorber 34.

Description

  The present invention relates to a charged particle beam therapy apparatus that irradiates a charged particle beam.

  Conventionally, what was described in patent document 1 is known as a charged particle beam therapy apparatus which irradiates a charged particle beam. The charged particle beam therapy apparatus described in Patent Literature 1 is an apparatus that performs treatment by irradiating a tumor in a patient's body with a charged particle beam by a wobbler method (broad beam method). This charged particle beam therapy system includes a cyclotron that accelerates charged particles to generate a charged particle beam, a degrader (range shifter) that adjusts the range of the charged particle beam by reducing the energy of the charged particle beam, and a charged particle beam. And a collimator for forming an irradiation field. The degrader is composed of a plurality of energy absorbers, and the number of energy absorbers used is set so that the charged particle beam has a desired range. The charged particle beam whose range is adjusted by the degrader is irradiated to the tumor in the patient's body after the irradiation range (irradiation field) is adjusted by the collimator.

Japanese Patent Laid-Open No. 01-131675

  Here, the amount of scattering of the charged particle beam greatly depends on the distance after passing through the degrader. If the gap between the downstream surface of the energy absorber disposed on the most downstream side of the degrader and the isocenter changes, the amount of scattering of the charged particle beam may change significantly. When the amount of scattering changes, the dose distribution of the charged particle beam applied to the affected area changes greatly. For example, when irradiating a charged particle beam by the wobbler method, even if the gap between the downstream surface of the energy absorber and the isocenter changes and the scattering amount of the charged particle beam changes significantly, the irradiation is performed by using a collimator. The dose at the outer edge of the field can be prevented from not meeting the treatment plan. On the other hand, in a charged particle beam treatment apparatus that irradiates a charged particle beam by a scanning method, the charged particle beam is scanned in accordance with the shape of the affected part (irradiation field), and therefore usually on the downstream side of the charged particle beam from the degrader. There is no collimator. For this reason, in a charged particle beam therapy system that irradiates a charged particle beam by the scanning method, when the gap between the downstream surface of the energy absorber and the isocenter changes and the amount of scattering of the charged particle beam changes significantly. It was difficult to irradiate a charged particle beam with a dose distribution according to the treatment plan.

  Then, an object of this invention is to provide the charged particle beam therapeutic apparatus which can irradiate a charged particle beam accurately with desired dose distribution.

  A charged particle beam therapy system according to an embodiment of the present invention includes an irradiation nozzle that irradiates a charged particle beam, and a plurality of energy absorbers that are provided in the irradiation nozzle and reduce the energy of the charged particle beam. In accordance with the combination of the energy absorber to be used, the degrader that adjusts the range of the charged particle beam according to the combination of the energy absorber used together, the drive unit that moves the degrader in the irradiation axis direction of the charged particle beam, and And a control unit that controls the drive unit so that the degrader moves in the irradiation axis direction of the charged particle beam.

  In this charged particle beam therapy system, the degrader moves in the direction of the irradiation axis of the charged particle beam in accordance with the combination of energy absorbers used in the degrader. Thereby, the dispersion | variation in the dose distribution of the charged particle beam which arises by the combination of an energy absorber can be correct | amended. Therefore, the charged particle beam can be accurately irradiated with a desired dose distribution.

  The control unit is a drive unit such that the distance from the downstream surface of the energy absorber disposed on the most downstream side in the irradiation axis direction of the charged particle beam among the energy absorbers to the isocenter is a preset distance. May be controlled. In this case, regardless of the combination of the energy absorbers, the gap between the downstream surface of the energy absorber disposed on the most downstream side and the isocenter is constant. Therefore, in the dose distribution at the isocenter of the charged particle beam, the dependence of the gap between the degrader and the isocenter due to the combination of energy absorbers can be excluded. Thereby, it is possible to irradiate the charged particle beam with higher accuracy with a desired dose distribution.

  The control unit may control the drive unit so that the distance from the scattering center of the charged particle beam passing through the degrader to the isocenter is a preset distance. In this case, the scattering at the isocenter of the charged particle beam can be made the same regardless of the combination of the energy absorbers. Thereby, it is possible to irradiate the charged particle beam with higher accuracy with a desired dose distribution.

  Of the plurality of energy absorbers, the energy absorber having the largest energy absorption amount and the energy absorber having the second largest energy absorption amount may be respectively disposed at both ends in the irradiation axis direction of the charged particle beam. In this case, the dose of the charged particle beam depends on whether or not at least one of the energy absorber disposed on the most upstream side of the charged particle beam and the energy absorber disposed on the most downstream side is disposed on the irradiation axis. Although the distribution tends to vary, the dose distribution variation can be corrected by moving the degrader. For this reason, a charged particle beam can be accurately irradiated with a desired dose distribution.

  A charged particle beam therapy system according to another embodiment of the present invention includes an irradiation nozzle that irradiates a charged particle beam, and an irradiation nozzle that reduces the energy of the charged particle beam and reduces the range of the charged particle beam. Degrader to be adjusted, drive unit for moving the degrader in the irradiation axis direction of the charged particle beam, and the distance from the most downstream surface in the irradiation axis direction of the charged particle beam in the degrader to the isocenter is a preset distance And a control unit for controlling the drive unit.

  In this charged particle beam therapy system, the degrader moves in the charged particle beam irradiation axis direction so that the distance from the most downstream surface in the irradiation axis direction of the charged particle beam in the degrader to the isocenter is a preset distance. To do. Thereby, even if the dose distribution of the charged particle beam varies when the range of the charged particle beam is changed by the degrader, the dose distribution variation can be corrected by moving the degrader. Therefore, the charged particle beam can be accurately irradiated with a desired dose distribution.

  A charged particle beam therapy system according to still another embodiment of the present invention includes an irradiation nozzle that irradiates a charged particle beam, and a charged particle beam range that is provided in the irradiation nozzle and reduces the energy of the charged particle beam. And a drive unit for moving the degrader in the direction of the irradiation axis of the charged particle beam, and a drive unit so that the distance from the scattering center of the charged particle beam passing through the degrader to the isocenter is a preset distance. A control unit for controlling.

  In this charged particle beam therapy system, the degrader moves in the irradiation axis direction of the charged particle beam so that the distance from the scattering center of the charged particle beam passing through the degrader to the isocenter becomes a preset distance. As a result, even when the dose distribution of the charged particle beam varies when the range of the charged particle beam is changed by the degrader, the scattering at the isocenter of the charged particle beam is made the same by moving the degrader. be able to. Therefore, the charged particle beam can be accurately irradiated with a desired dose distribution.

  According to various embodiments of the present invention, a charged particle beam can be accurately irradiated with a desired dose distribution.

1 is a perspective view of a charged particle beam therapy apparatus according to an embodiment. It is a schematic block diagram of the charged particle beam therapy apparatus of FIG. It is a schematic diagram which shows the structure of the degrader of FIG. It is a schematic diagram which shows the drive structure of the degrader of FIG. It is a figure which shows the drive position of a degrader, (a) is the state where the 1st absorber-the 4th absorber are arrange | positioned on a base axis, (b) is the state where only the 1st absorber is arrange | positioned on a base axis. It is a schematic diagram shown. It is a figure which shows the drive position of the degrader which concerns on a 1st modification, (a) is the state by which the 1st absorber-the 4th absorber were arrange | positioned on a base axis, (b) is only a 1st absorber on a base axis. It is a schematic diagram which shows the state by which is arrange | positioned. It is a figure which shows the drive position of the degrader which concerns on a 2nd modification, (a) is the state which extended the absorber, (b) is a schematic diagram which shows the state which shrunk the absorber. It is a figure which shows the drive position of the degrader which concerns on a 3rd modification, (a) is the state which extended the absorber, (b) is a schematic diagram which shows the state which shortened the absorber.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIGS. 1 and 2, the charged particle beam therapy system 1 includes a treatment table 11 on which a patient 13 is placed, a rotating gantry 12 that can accommodate the treatment table 11 and can be rotated around the treatment table, and a rotation. An irradiation nozzle (irradiation unit) 8 provided inside the gantry 12 for irradiating the charged particle beam R and an accelerator 2 for generating the charged particle beam R are provided.

  FIG. 2 is a schematic configuration diagram of a charged particle beam therapy apparatus that irradiates a charged particle beam with a scanning method. As shown in FIG. 2, the charged particle beam therapy system 1 irradiates a charged particle beam R to a tumor (irradiated body) 14 in the body of a patient 13. The charged particle beam R is obtained by accelerating charged particles at high speed, and examples thereof include a proton beam, a heavy particle (heavy ion) beam, and an electron beam. The charged particle beam R is generated in the accelerator 2. The accelerator 2 is a generation source that accelerates charged particles and continuously generates charged particle beams R. Examples of the accelerator 2 include a cyclotron, a synchrotron, a cyclosynchrotron, and a linac.

  In the following description, the terms “X direction”, “Y direction”, and “Z direction” will be used. The “Z direction” is a direction in which the base axis AX of the charged particle beam R extends. The “base axis AX” is an irradiation axis of the charged particle beam R when it is not deflected by scanning electromagnets 3a and 3b described later. FIG. 2 and the like show a state where the charged particle beam R is irradiated along the base axis AX. The “X direction” is one direction in a plane orthogonal to the Z direction. The “Y direction” is a direction orthogonal to the X direction in a plane orthogonal to the Z direction.

  As shown in FIG. 2, the irradiation nozzle 8 includes scanning electromagnets 3a and 3b, monitors 4a and 4b, converging bodies 6a and 6b, a degrader 30, and a drive unit 40 (see FIG. 4). The scanning electromagnets 3 a and 3 b, the monitors 4 a and 4 b, the convergence bodies 6 a and 6 b, the degrader 30, and the drive unit 40 are accommodated in the irradiation nozzle 8. Each component such as the degrader 30 and the accelerator 2 accommodated in the irradiation nozzle 8 are controlled by a control device (control unit) 7 provided in the charged particle beam treatment apparatus 1.

  The charged particle beam R generated by the accelerator 2 is transported to the irradiation nozzle 8 by a beam transport system. The accelerator 2 is connected to the control device 7, and the supplied current is controlled.

  The scanning electromagnets 3a and 3b are each composed of a pair of electromagnets, change the magnetic field between the pair of electromagnets according to the current supplied from the control device 7, and scan the charged particle beam R passing between the electromagnets. The X direction scanning electromagnet 3a scans the charged particle beam R in the X direction, and the Y direction scanning electromagnet 3b scans the charged particle beam R in the Y direction. These scanning electromagnets 3 a and 3 b are arranged in this order on the base axis AX and downstream of the accelerator 2.

  The monitor 4a monitors the beam position of the charged particle beam R. The monitor 4b monitors the absolute value of the dose of the charged particle beam R and the dose distribution of the charged particle beam R. Each of the monitors 4a and 4b outputs the monitored monitoring information to the control device 7. The monitor 4a is disposed on the base axis AX of the charged particle beam R and downstream of the accelerator 2 and upstream of the X-direction scanning electromagnet 3a. The monitor 4b is disposed on the base axis AX and downstream of the Y-direction scanning electromagnet 3b.

  The converging bodies 6a and 6b are for focusing the charged particle beam R, for example, and here, an electromagnet is used. The converging body 6a is disposed on the base axis AX and between the accelerator 2 and the monitor 4a, and the converging body 6b is disposed on the base axis AX and between the monitor 4a and the scanning electromagnet 3a.

  The degrader 30 adjusts the range of the charged particle beam R by reducing the energy of the charged particle beam R passing therethrough. The range is adjusted roughly by a degrader (not shown) provided immediately after the accelerator 2 and finely adjusted by the degrader 30 in the irradiation nozzle 8. The degrader 30 is provided on the base axis AX and on the downstream side of the charged particle beam R with respect to the scanning electromagnets 3a and 3b, and adjusts the maximum reachable depth of the charged particle beam R in the body of the patient 13. In the present embodiment, the “range” is a distance traveled from the body surface of the patient 13 until the charged particle beam R loses kinetic energy and stops. More specifically, the range is a depth that is deeper than the irradiation distance (depth) at which the maximum dose is obtained and the dose is 90% when the maximum dose is 100%. When irradiating the tumor 14 with the charged particle beam R, the tumor 14 is virtually divided into a plurality of layers in the Z direction, and the charged particle beam R is scanned along a predetermined scanning pattern in the irradiation range set in each layer. While irradiating. After the irradiation of the charged particle beam R to one layer is completed, the range is adjusted by the degrader 30 (or a degrader immediately after the accelerator 2), and the charged particle beam R of the other layer is adjusted to the other layer. Irradiate. The degrader 30 is disposed at a position of about 1500 mm to 2000 mm from the Y-direction scanning electromagnet 3b.

  The range of the charged particle beam R is adjusted by changing the passing distance of the charged particle beam R in the degrader 30. The configuration of the degrader 30 will be described later in detail. The position where the degrader 30 is provided is not particularly limited as long as it is on the downstream side of the scanning electromagnets 3a and 3b. However, when the scanning method is employed, it is preferably provided on the downstream side of the monitor 4b. In the present embodiment, the degrader 30 is provided at the tip 8 a of the irradiation nozzle 8. The tip of the irradiation nozzle 8 is the downstream end of the charged particle beam R. The downstream side of the charged particle beam R from the degrader 30 is filled with the atmosphere or a predetermined gas.

  The control device 7 is constituted by, for example, a CPU, a ROM, a RAM, and the like. The control device 7 controls the accelerator 2, the scanning electromagnets 3a and 3b, the converging bodies 6a and 6b, and the degrader 30 based on the monitoring information output from the monitors 4a and 4b.

  When the charged particle beam therapy apparatus 1 shown in FIG. 2 irradiates the charged particle beam R by the scanning method, the degrader 30 is set so as to have a predetermined range, and the passing charged particle beam R converges. Then, the convergence bodies 6a and 6b are set in the operating state (ON).

  Subsequently, a charged particle beam R is emitted from the accelerator 2. The emitted charged particle beam R is scanned by the scanning electromagnets 3 a and 3 b and the range of the charged particle beam R is adjusted by the degrader 30. Thereby, the charged particle beam R is irradiated while being scanned within the irradiation range in one layer set in the Z direction with respect to the tumor 14. After the irradiation of one layer is completed, the charged particle beam R is irradiated to the next layer.

  Furthermore, the control device 7 controls the drive unit 40 to move the degrader 30 along the base axis AX of the charged particle beam R. The control of the drive unit 40 by the control device 7 will be described later in detail.

  Next, details of the configuration of the degrader 30 will be described with reference to FIG. As shown in FIG. 3, the degrader 30 includes a first absorber 31, a second absorber 32, a third absorber 33 and a fourth absorber 34 as energy absorbers, and an actuator 35. The first absorber 31 to the fourth absorber 34 absorb the energy of the charged particle beam R. The 1st absorber 31-the 4th absorber 34 have plate shape, and the thickness of the irradiation axis direction of the charged particle beam R mutually differs. In the present embodiment, the first absorber 31, the fourth absorber 34, the second absorber 32, and the third absorber 33 are reduced in thickness in this order. The first absorber 31 to the fourth absorber 34 are a first absorber 31, a second absorber 32, and a third absorber 33 from the upstream side to the downstream side in the irradiation axis direction of the charged particle beam R. The fourth absorbers 34 are arranged in this order. As the 1st absorber 31-the 4th absorber 34, an acrylic board can be used, for example.

  The actuator 35 reciprocates the first absorber 31 to the fourth absorber 34 in a plane orthogonal to the Z direction based on an instruction from the control device 7. The actuator 35 can arrange the first absorber 31 to the fourth absorber 34 on the base axis AX of the charged particle beam R independently of each other and can be retracted from the base axis AX. In this way, by changing the number of the first absorber 31 to the fourth absorber 34 arranged on the base axis AX of the charged particle beam R, the charged particle beam R is changed to the first absorber 31 and the like on the base axis AX. The length passing through the energy absorber can be changed. Thereby, the range of the charged particle beam R can be adjusted.

  Next, details of the configuration of the drive unit 40 will be described with reference to FIG. As shown in FIG. 4, the drive unit 40 includes a motor 41 and a ball screw 42. The ball screw 42 is arranged so that the extending direction is parallel to the base axis AX. The ball screw 42 is screwed into a nut portion 30Xa attached to the housing portion 30X that houses the degrader 30. As the ball screw 42 rotates, the housing 30 </ b> X moves along the extending direction of the ball screw 42. That is, as the ball screw 42 rotates, the degrader 30 moves along the base axis AX of the charged particle beam R. A driving force from the motor 41 is transmitted to the ball screw 42. The motor 41 is controlled by the control device 7.

  Next, details of control of the drive unit 40 by the control device 7 will be described. The controller 7 drives the drive unit 40 so that the degrader 30 moves along the base axis AX according to the combination of the first absorber 31 to the fourth absorber 34 arranged on the base axis AX of the charged particle beam R. The motor 41 is controlled. In more detail, the control apparatus 7 is the downstream in the absorber arrange | positioned in the most downstream side of the base axis AX among the 1st absorber 31-the 4th absorber 34 arrange | positioned on the base axis AX of the charged particle beam R. The motor 41 is controlled so that the distance from the side surface to the isocenter P becomes a predetermined distance L1, and the degrader 30 is moved.

  Specifically, for example, when the first absorber 31 to the fourth absorber 34 are arranged on the base axis AX of the charged particle beam R as shown in FIG. The motor 41 is controlled to move the degrader 30 so that the distance from the downstream surface of the fourth absorber 34 arranged on the most downstream side to the isocenter P becomes a predetermined distance L1. Further, for example, when only the first absorber 31 is disposed on the base axis AX of the charged particle beam R as shown in FIG. 5B, the control device 7 performs isolating from the downstream surface of the first absorber 31. The motor 41 is controlled so that the distance to the center P becomes a predetermined distance L1, and the degrader 30 is moved. The isocenter P is an intersection of the base axis AX and the rotation axis CX of the rotating gantry 12.

  In addition, the control apparatus 7 has memorize | stored previously the positional relationship of the 1st absorber 31-the 4th absorber 34, information, such as a mutual space | interval. For this reason, the control device 7 controls the position of the degrader 30 in the base axis AX direction based on such information, information on the first absorber 31 to the fourth absorber 34 arranged on the base axis AX, and the like. Can do.

  The present embodiment is configured as described above, and is arranged on the most downstream side on the base axis AX in accordance with the combination of the first absorber 31 to the fourth absorber 34 arranged on the base axis AX of the charged particle beam R. The degrader 30 moves along the base axis AX so that the distance from the downstream surface of the absorber to the isocenter P is a predetermined distance L1. Thereby, whatever the combination of the first absorber 31 to the fourth absorber 34 arranged on the base axis AX, the downstream surface of the absorber arranged on the most downstream side and the isocenter P The gap between is constant.

  Since the amount of scattering of the charged particle beam R greatly depends on the distance after passing through the degrader 30, the gap between the downstream surface of the absorber arranged on the most downstream side and the isocenter P changes. Then, the amount of scattering of the charged particle beam R may be greatly changed. When the amount of scattering of the charged particle beam R changes significantly, the dose distribution of the charged particle beam R irradiated to the affected area 14 changes significantly. In particular, the dose of the charged particle beam that is irradiated outside the edge of the irradiation field increases. In other words, if the gap between the downstream surface of the absorber arranged on the most downstream side and the isocenter P changes, there is a possibility that irradiation with a dose distribution as planned for treatment cannot be performed. For this reason, the 1st absorber 31-4th absorption arrange | positioned on the base axis AX by making the gap between the downstream surface of the absorber arrange | positioned most downstream, and the isocenter P constant. It is possible to suppress a significant change in the dose distribution of the charged particle beam R irradiated to the affected area 14 due to the combination of the bodies 34.

  Thus, the charged particle beam therapy system 1 can correct the variation in dose distribution of the charged particle beam R caused by the combination of the first absorber 31 to the fourth absorber 34, and the charged particle beam R can be used as a desired dose. It is possible to irradiate accurately with distribution.

  In the degrader 30, the first absorber 31 having the largest energy absorption amount is arranged on the most upstream side of the charged particle beam R, and the fourth absorber 34 having the second largest energy absorption amount is on the most downstream side of the charged particle beam R. Is arranged. In this case, depending on whether or not the fourth absorber 34 is disposed on the base axis AX, the distance from the downstream surface of the absorber disposed on the most downstream side on the base axis AX to the isocenter P varies. As a result, the dose distribution of the charged particle beam R tends to vary. Therefore, by moving the degrader 30 as in the irradiation nozzle 8 of the present embodiment, it is possible to correct this variation in dose distribution.

  Next, a first modification will be described. In this modification, only the method for controlling the movement of the degrader 30 by the control device 7 is changed from the above embodiment. In the present modification, the control device 7 controls the motor 41 of the driving unit 40 so that the distance from the scattering center of the charged particle beam R passing through the degrader 30 to the isocenter P becomes a predetermined distance L2. Move 30.

  Specifically, for example, when the first absorber 31 to the fourth absorber 34 are arranged on the base axis AX of the charged particle beam R as illustrated in FIG. 6A, the control device 7 passes through the degrader 30. The motor 41 is controlled to move the degrader 30 so that the distance between the scattering center W of the charged particle beam R and the isocenter P is the distance L2. For example, when only the first absorber 31 is arranged on the base axis AX of the charged particle beam R as shown in FIG. 6B, the control device 7 causes the scattering center of the charged particle beam R passing through the degrader 30 to The motor 41 is controlled so that the distance between W and the isocenter P becomes the distance L2, and the degrader 30 is moved.

  In this case, the scattering at the isocenter P of the charged particle beam R can be made the same regardless of the combination of the first absorber 31 to the fourth absorber 34 arranged on the base axis AX. . Accordingly, the charged particle beam R can be accurately irradiated with a desired dose distribution regardless of the combination of the first absorber 31 to the fourth absorber 34 disposed on the base axis AX.

  In the degrader 30, the first absorber 31 having the largest energy absorption amount is disposed on the most upstream side of the charged particle beam R, and the fourth absorber 34 having the second largest energy absorption amount is the largest of the charged particle beam R. It is arranged downstream. In this case, the dose distribution of the charged particle beam R tends to vary depending on whether or not at least one of the first absorber 31 and the fourth absorber 34 is disposed on the base axis AX. Therefore, by moving the degrader 30 like the irradiation nozzle 8 of this modification, the charged particle beam R is scattered at the isocenter P regardless of the combination of the first absorber 31 to the fourth absorber 34. Can be the same.

  Next, a second modification will be described. In this modification, a degrader 30A having a different configuration is used instead of the degrader 30 in the above embodiment. The degrader 30 </ b> A in the present modification is configured to include a bellows-shaped housing part 36 that can be expanded and contracted in the base axis AX direction of the charged particle beam R, and an absorber 37 filled in the housing part 36. As the absorber 37, for example, a liquid such as water can be used. The length of the absorber 37 on the base axis AX can be changed by expanding and contracting the housing part 36. Thereby, the amount of decrease in energy of the charged particle beam R passing through the absorber 37 can be changed, and the range of the charged particle beam R can be adjusted.

  In addition, since the volume in the housing | casing part 36 changes by expanding / contracting the housing | casing part 36, the quantity of the absorber 37 required in order to satisfy | fill the inside of the housing | casing part 36 changes. For this reason, a reservoir tank or the like may be connected to the housing portion 36. Expansion and contraction of the housing part 36 is performed by an actuator (not shown). The actuator that expands and contracts the housing portion 36 is controlled by the control device 7. Similarly to the above-described embodiment, the degrader 30A is moved along the base axis AX by the drive unit 40.

  The control device 7 is, for example, in a state where the housing part 36 is extended as shown in FIG. 7A and a state where the housing part 36 is contracted as shown in FIG. Whatever the expansion / contraction state of the housing 36, the distance from the most downstream surface of the base axis AX of the charged particle beam R to the isocenter P in the degrader 30A is a predetermined distance L3. The motor 41 of the drive unit 40 is controlled to move the degrader 30A.

  In this case, the gap between the most downstream surface of the degrader 30A and the isocenter P is constant regardless of the stretched state of the absorber 37 on the base axis AX. Therefore, the variation in the dose distribution of the charged particle beam R that occurs when the absorber 37 is only expanded and contracted can be corrected, and the charged particle beam R can be accurately irradiated with the desired dose distribution.

  Next, a third modification will be described. This modification is obtained by changing only the method of controlling the movement of the degrader 30A by the control device 7 with respect to the second modification described with reference to FIG. In the present modification, the control device 7 controls the motor 41 of the drive unit 40 so that the distance from the scattering center of the charged particle beam R passing through the degrader 30A to the isocenter P becomes a predetermined distance L4. Move 30A.

  Specifically, for example, as shown in FIG. 8A, the casing 36 is extended, and as shown in FIG. 8B, the casing 36 is contracted. Regardless of the expansion / contraction state of the housing unit 36, the motor 41 is controlled so that the distance between the scattering center W of the charged particle beam R passing through the degrader 30A and the isocenter P becomes the distance L4, and the degrader 30A is Move.

  In this case, the scattering at the isocenter P of the charged particle beam R can be made the same regardless of the stretched state of the absorber 37 on the base axis AX. Thereby, the charged particle beam R can be accurately irradiated with a desired dose distribution regardless of the stretched state of the absorber 37 on the base axis AX.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the embodiment, the first modification, and the second modification, the degrader 30 includes the four energy absorbers of the first absorber 31 to the fourth absorber 34, but is limited to four. Not. Further, the first absorber 31 having the largest energy absorption amount is arranged on the most upstream side of the charged particle beam R, and the fourth absorber 34 having the second largest energy absorption amount is arranged on the most downstream side of the charged particle beam R. However, the order of arrangement of the first absorber 31 to the fourth absorber 34 is not limited to this.

  In the embodiment and each modification, the configuration in which the degraders 30 and 30A are moved along the base axis AX is applied to the charged particle beam therapy apparatus 1 that irradiates the charged particle beam R by the scanning method. You may apply to the charged particle beam therapy apparatus 1 which irradiates the particle beam R with a wobbler method. Also in this case, the charged particle beam R can be accurately irradiated with a desired dose distribution.

  DESCRIPTION OF SYMBOLS 1 ... Charged particle beam therapy apparatus, 2 ... Accelerator, 7 ... Control apparatus (control part), 8 ... Irradiation nozzle, 30, 30A ... Degrader, 31 ... 1st absorber (energy absorber), 32 ... 2nd absorber (Energy absorber), 33 ... third absorber (energy absorber), 34 ... fourth absorber (energy absorber), 37 ... absorber (energy absorber), 40 ... drive unit.

Claims (6)

An irradiation nozzle for irradiating a charged particle beam;
A degrader that is provided in the irradiation nozzle and includes a plurality of energy absorbers that reduce the energy of the charged particle beam and adjusts the range of the charged particle beam according to the combination of the energy absorbers to be used. When,
A drive unit for moving the degrader in the irradiation axis direction of the charged particle beam;
A charged particle beam therapy apparatus comprising: a control unit that controls the drive unit so that the degrader moves in an irradiation axis direction of the charged particle beam according to a combination of the energy absorbers to be used.   In the control unit, a distance from the downstream surface of the energy absorber disposed on the most downstream side in the irradiation axis direction of the charged particle beam to the isocenter in the energy absorber is a preset distance. The charged particle beam therapy apparatus according to claim 1, wherein the drive unit is controlled as described above.   The charged particle beam therapy system according to claim 1, wherein the control unit controls the driving unit so that a distance from a scattering center of the charged particle beam passing through the degrader to an isocenter is a preset distance. .   Among the plurality of energy absorbers, the energy absorber having the largest energy absorption amount and the energy absorber having the second largest energy absorption amount are respectively disposed at both ends in the irradiation axis direction of the charged particle beam. The charged particle beam therapy apparatus according to claim 2 or 3. An irradiation nozzle for irradiating a charged particle beam;
A degrader that is provided in the irradiation nozzle and adjusts the range of the charged particle beam by reducing the energy of the charged particle beam;
A drive unit for moving the degrader in the irradiation axis direction of the charged particle beam;
A charged particle beam therapy system comprising: a control unit that controls the drive unit such that a distance from the most downstream surface in the irradiation axis direction of the charged particle beam in the degrader to the isocenter is a preset distance. An irradiation nozzle for irradiating a charged particle beam;
A degrader that is provided in the irradiation nozzle and adjusts the range of the charged particle beam by reducing the energy of the charged particle beam;
A drive unit for moving the degrader in the irradiation axis direction of the charged particle beam;
A charged particle beam therapy apparatus comprising: a control unit that controls the drive unit so that a distance from a scattering center of the charged particle beam passing through the degrader to an isocenter is a preset distance.

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