WO2016132445A1

WO2016132445A1 - Charged particle irradiation system

Info

Publication number: WO2016132445A1
Application number: PCT/JP2015/054184
Authority: WO
Inventors: 平本　和夫; 泰介高柳; 伸一清水; 祐介藤井; 博樹白土; 梅垣　菊男
Original assignee: 株式会社日立製作所; 国立大学法人北海道大学
Priority date: 2015-02-16
Filing date: 2015-02-16
Publication date: 2016-08-25

Abstract

Provided is a charged particle irradiation system capable of distinguishing the type of charged particles with which an object to be irradiated is to be irradiated, prior to the irradiation. The system is provided with: an ion generation device that generates a plurality of types of ions of different nuclear species; an accelerator that accelerates the ions supplied from the ion generation device to emit an ion beam; a beam transport system that transports the ion beam emitted from the accelerator; an irradiation device that irradiates an irradiation target with the ion beam transported by the beam transport system; and a nuclear species distinguishing device configured to distinguish the nuclear species of the ions supplied from the ion generation device.

Description

Charged particle irradiation system

The present invention relates to a charged particle irradiation system, and more particularly to a charged particle irradiation system suitable for cancer treatment using a plurality of types of ion beams composed of protons, helium ions, carbon ions, or the like.

There is a known method of treating cancer by irradiating charged particles such as protons, helium ions, and carbon ions to the affected area of the cancer. An apparatus for irradiating charged particles in this treatment method includes a charged particle generation apparatus, a beam transport system, and an irradiation apparatus. Charged particles generated by the charged particle generator are transported to the irradiation device by the beam transport system, and the lateral distribution and depth distribution (energy distribution) are expanded by the irradiation device to match the shape of the cancer. Later, the cancerous part is reached. Thereby, the charged particles that have reached the affected area of the cancer form a dose distribution that matches the shape of the affected area.

For charged particles such as protons, helium ions, and carbon ions, the heavier particles or the larger energy particles have a smaller scattering angle when they collide with a substance, so the gradient of the dose distribution in the lateral direction becomes steeper. The steeper lateral gradient of the dose distribution makes it possible to form a dose distribution that more closely matches the affected area. On the other hand, when the ratio of the number of charges to the mass number (hereinafter referred to as the charge-mass ratio) and the energy per nucleon are compared under the same condition, the lighter particles reach the same depth because they reach the patient deeper. The energy required for this is smaller for lighter particles. Therefore, the device for irradiating light particles is smaller than the device for irradiating heavy particles. As an apparatus for irradiating a plurality of types of charged particles, for example, there are devices described in Patent Document 1 and Patent Document 2.

JP 2013-233233 A Special table 2013-533953 gazette

According to the charged particle irradiation system described in

Patent Document

1 or 2, both the deep position and the shallow position are irradiated by irradiating light particles with high energy to the deep position of the affected area and irradiating heavy particles to the shallow position. In this case, it is possible to form a dose distribution more matched to the affected area with a small device. Here, the dose distribution formed by the charged particles to be irradiated is different for each type of charged particles. Therefore, confirming the type of charged particles to be irradiated before irradiation is important for ensuring the reliability of an apparatus that irradiates a plurality of types of charged particles.

Some devices that irradiate multiple types of charged particles irradiate multiple types of charged particles having the same charge-mass ratio. As an example, helium ions with a mass number of 4 and a charge number of 2 (charge mass ratio of 1/2) and carbon ions with a mass number of 12 and a charge number of 6 (also charge mass ratio of 1/2) are irradiated. There is a device. When charged particles with the same charge-mass ratio are accelerated under the same conditions, the energy per nucleon is equal and the trajectories in the magnetic field are also the same. Since it is difficult to determine the type of charged particles traveling in the same orbit, it is particularly significant that the type of charged particles can be determined in an apparatus that irradiates a plurality of types of charged particles having the same charge-mass ratio.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a charged particle irradiation system capable of determining the type of charged particles irradiated to an irradiation target before irradiation.

In order to solve the above problems, a charged particle irradiation system of the present invention includes an ion generator that generates a plurality of types of ions having different nuclides, and an accelerator that accelerates the ions supplied from the ion generator and emits the ions as an ion beam. A beam transport system that transports an ion beam emitted from the accelerator, an irradiation device that irradiates an irradiation target with an ion beam transported by the beam transport system, and a nuclide of ions supplied from the ion generator. A nuclide discrimination device configured to discriminate is provided.

According to the present invention, in the treatment of irradiating a plurality of types of charged particles, it is possible to reliably irradiate the charged particles determined in the treatment plan.

1 is an overall configuration diagram of a charged particle irradiation system according to a first embodiment. It is an expanded block diagram of the nuclide discrimination | determination apparatus with which the charged particle irradiation system in 1st Embodiment was equipped. It is an enlarged block diagram of the irradiation apparatus with which the charged particle irradiation system in 1st Embodiment was equipped. It is a figure which shows the dose distribution of the horizontal direction formed with the irradiated charged particle. It is a figure which shows the dose distribution of the depth direction formed with the charged particle irradiated with single energy. It is a figure which shows the dose distribution of the depth direction formed of the helium ion and carbon ion irradiated with multiple energy. It is a flowchart which shows irradiation control by the control apparatus with which the charged particle irradiation system in 1st Embodiment was equipped. It is an enlarged block diagram of the nuclide discrimination | determination apparatus (modification 1) with which the charged particle irradiation system in 1st Embodiment was equipped. It is an enlarged block diagram of the nuclide discrimination | determination apparatus (modification 2) with which the charged particle irradiation system in 1st Embodiment was equipped. It is an enlarged block diagram of the nuclide discrimination | determination apparatus (modification 3) with which the charged particle irradiation system in 1st Embodiment was equipped. It is a whole block diagram of the charged particle irradiation system in 2nd Embodiment. It is a flowchart which shows irradiation control by the control apparatus with which the charged particle irradiation system in 2nd Embodiment was equipped. It is a whole block diagram of the charged particle irradiation system in 3rd Embodiment. It is an expanded block diagram of the irradiation apparatus with which the charged particle irradiation system in 3rd Embodiment was equipped. It is a flowchart which shows the irradiation control by the control apparatus with which the charged particle irradiation system in 3rd Embodiment was equipped.

Embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is an overall configuration diagram of a charged particle beam irradiation system according to a first embodiment of the present invention. In FIG. 1, the particle beam irradiation system includes a charged particle generator 100, an accelerator 200 including a linac 6a as a front stage accelerator and a synchrotron 6b as a rear stage accelerator, a beam transport system 300, an irradiation apparatus 20, And a control device 30.

The charged particle generator 100 is mainly composed of a plurality of

ion sources

1 and 2. The

ion sources

1 and 2 are devices that generate charged particles of different nuclides, and the

ion sources

1 and 2 in the present embodiment are each composed of a helium ion source and a carbon ion source. The helium ions generated by the helium ion source 1 have a mass number of 4 and a charge number of 2 (charge-mass ratio is 1/2), and the carbon ions generated by the carbon ion source 2 have a mass number of 12 and a charge number. Is 6 (also charge-mass ratio is 1/2). A helium ion source shutter 3, a carbon ion source shutter 4, and an ion source switching device 5 are provided between the

ion sources

1 and 2 and the linac 6a. The linac 6a is connected to the synchrotron 6b via the beam duct 7, and after accelerating charged particles incident from the

ion sources

1 and 2 to energy that can enter the synchrotron 6b, the linac 6a is emitted toward the synchrotron 6b. To do. The synchrotron 6b includes an annular beam duct 8 and a plurality of deflection electromagnets 9, a plurality of quadrupole electromagnets (not shown), a high-frequency acceleration electrode 10, an output high-frequency electrode 11, and an output deflector 12. The synchrotron 6b accelerates charged particles incident from the linac 6a to energy necessary for target irradiation, and outputs the accelerated particles to the beam transport system 300.

The beam transport system 300 transports the beam emitted from the emission deflector 12 of the synchrotron 6b to the irradiation device 20, and includes a beam duct 13 that connects the emission deflector 12 of the synchrotron 6b and the irradiation device 20. A plurality of deflection electromagnets 14 provided in the beam duct 13 and a plurality of quadrupole electromagnets (not shown) are provided. A part of the beam transport system 300 is installed in the rotating gantry 15 so as to rotate together with the rotating gantry 15. The beam transport system 300 includes a path switching device 40 and a nuclide discrimination device 50 in the middle of the beam duct 13. The path switching device 40 includes an electromagnet that can switch the magnetic field intensity at high speed, and has a function of switching the path of the charged particles emitted from the synchrotron 6b between the path reaching the irradiation apparatus 20 and the path reaching the nuclide discrimination apparatus 50. Have. The nuclide discrimination device 50 has a function of measuring a predetermined parameter depending on the nuclide of the charged particle incident on the nuclide discrimination device 50. An enlarged configuration diagram of the nuclide discrimination device 50 is shown in FIG. In FIG. 2, the nuclide determination device 50 includes a nuclide measurement unit 51 and a nuclide determination unit 52. The nuclide measurement unit 51 includes a plurality of metal plates 53 stacked at a predetermined interval, and each of the plurality of metal plates 53 is connected to a nuclide determination unit 52.

Returning to FIG. 1, the irradiation device 20 is mounted on the rotating gantry 15 so as to rotate integrally with the rotating gantry 15. By rotating the rotating gantry 15, the irradiation device 20 is attached to the patient 17 fixed on the couch 16. The irradiation angle can be set from 0 degrees to 360 degrees.

The enlarged block diagram of the irradiation apparatus 20 is shown in FIG. In FIG. 3, the irradiation device 20 includes two pairs of scanning electromagnets 21 A and 21 B, a dose monitor 22, and a position monitor 23. The two pairs of scanning electromagnets 21 A and 21 B are installed in a direction perpendicular to each other, and change the position where charged particles in a direction perpendicular to the beam axis 24 arrive.

Returning to FIG. 1, the control device 30 is connected to the charged particle generation device 100, the accelerator 200, the beam transport system 300, the irradiation device 20, and the database 31, and spot data recorded in the database 31. These are controlled based on (described later).

The dose distribution formed in the patient's body by irradiating charged particles will be described. The scanning irradiation method, which is the irradiation method of the present embodiment, is a method in which a dose distribution called a spot is arranged in a direction perpendicular to the beam axis (hereinafter referred to as a lateral direction) and a depth direction so as to match the shape of the affected part. The irradiation position in the horizontal direction is changed by changing the excitation amount of the

scanning electromagnets

21A and 21B, and the irradiation position in the depth direction is changed by changing the energy of the electroparticles.

FIG. 4 is a diagram showing a dose distribution in the lateral direction formed by irradiated charged particles. The dose distribution 60 in the lateral direction of each spot has a Gaussian distribution shape. For example, a uniform dose distribution 61 can be formed by arranging spots irradiated with an equal amount of charged particles at equal intervals.

FIG. 5A is a diagram showing a dose distribution in the depth direction formed by charged particles irradiated with a single energy. Since charged particles give a lot of energy immediately before stopping, a peak 70 (hereinafter referred to as a Bragg peak) is formed immediately before stopping. The water equivalent thickness from the body surface to the Bragg peak 70 is called the range. For example, when helium ions and carbon ions are compared, if the energy per nucleon is equal, helium ions having a small mass number have a larger range than carbon ions. Therefore, helium ions can achieve the same range in a smaller system than carbon ions. On the other hand, when helium ions and carbon ions have the same range (energy per nucleon is different), carbon ions have higher straightness and a smaller beam size. In addition, the beam size is larger as the energy of any nuclide is lower (the shorter the range is). Therefore, for example, by irradiating helium ions at a deep position and irradiating carbon ions at a shallow position, the system can be miniaturized and charged particles having a small beam size can be irradiated at both a deep position and a shallow position. .

FIG. 5B is a diagram showing a dose distribution in the depth direction formed by helium ions and carbon ions irradiated with a plurality of energies. As shown in FIG. 5B, the affected area is divided into a deep irradiation region 71 and a shallow irradiation region 72 from the body surface, and helium ions are irradiated to the deep irradiation region 71 with a plurality of energies, and the shallow irradiation region 72 is irradiated to the shallow irradiation region 72. By irradiating carbon ions with a plurality of energies, a uniform dose distribution 73 is formed in the affected area in the depth direction.

-Work procedure-
An operation procedure by an operator when performing treatment using the charged particle irradiation system according to the present embodiment will be described with reference to FIG.

Before treatment, determine a treatment plan using a treatment planning device (not shown). Specifically, based on the X-ray CT image of the affected part 18 imaged in advance so that a desired dose distribution is formed in the affected part 18 of the patient 17, the angle of the rotating gantry 15, the irradiation parameters for each spot (charged particles) Type (nuclide), energy, target irradiation position, target irradiation amount) and the like. The determined irradiation parameters for each spot are registered in the database 31 as spot data.

After preparation of treatment plan, preparation for irradiation is performed. Specifically, the patient 17 is fixed on the couch 16, the couch 16 is moved so that the patient 17 is placed at a desired position, and the angle of the rotating gantry 15 is set to the same angle as when the treatment plan is created. .

After the above preparation work is completed, an irradiation start button (not shown) is pushed to instruct the control device 30 to start irradiation. Thereafter, irradiation control (described later) based on the spot data registered in the database 31 is performed by the control device 30.

-Irradiation control-
FIG. 6 is a flowchart showing irradiation control by the control device 30. Hereinafter, each step constituting the flow will be described in order.

In step S101, preparation for irradiation is performed. The control device 30 reads spot data from the database 31 and determines the irradiation order of each spot. Usually, irradiation is performed in the order of a high energy spot to a low energy spot. In this embodiment, helium ions are used first to irradiate from a high energy spot to a low energy spot, and then carbon ions are used to irradiate from a high energy spot to a low energy spot.

In step S102, the helium ion source 1 is selected. The control device 30 switches the path in the ion source switching device 5 to the helium ion source 1 side and opens the shutter 3 for the helium ion source. At this time, the carbon ion source shutter 4 is kept closed.

In step S103, helium ions are accelerated in the previous stage. The control device 30 accelerates the helium ions emitted from the helium ion source 1 by the linac 6a and emits the helium ions to the synchrotron 6b. The helium ions incident on the synchrotron 6b circulate in the synchrotron 6b.

In step S104, helium ions are accelerated later. The control device 30 applies a high frequency to the high frequency acceleration electrode 10 and controls the amount of excitation of the deflection electromagnet 9 and a quadrupole magnet (not shown) to accelerate helium ions to a predetermined energy.

In step S105, the control device 30 excites the electromagnet of the path switching device 40 so that helium ions reach the nuclide discrimination device 50.

In step S106, the ion nuclide is determined. The control device 30 applies a high frequency to the high-frequency electrode 11 for emission, and emits helium ions circulating in the synchrotron 6b from the extraction deflector 12 to the beam transport system 300. The helium ions emitted to the beam transport system 300 reach the nuclide discrimination device 50 via the path switching device 40. The helium ions that have reached the nuclide discrimination device 50 lose energy while passing through the metal plate 53 (FIG. 2), and eventually stop in any of the metal plates 53 when the energy disappears. The position (range) of the metal plate 53 where helium ions are stopped is detected by the nuclide discrimination unit 52 as an electric signal flowing through the metal plate 53. The nuclide discrimination unit 52 enters the nuclide discrimination device 50 based on the energy per nucleon determined by the acceleration condition of the accelerator 200 (the synchrotron 6b) and the stop position (range) of helium ions measured by the nuclide measurement unit 51. The nuclide of the charged particles is discriminated, and the discrimination result is transmitted to the control device 30. After receiving the nuclide discrimination result, the control device 30 stops the extraction of helium ions from the synchrotron 6b to the beam transport system 300 by stopping the application of the high frequency to the extraction high-frequency electrode 11.

In step S107, it is determined whether or not the nuclide of the helium ion source 1 selected in step S102 matches the nuclide determined in step S106. If the nuclide is determined to be helium ions in step S106, and if it is determined to be coincident (yes) in step S107 (normal), helium ions are irradiated to the affected part 18 of the patient 17 in step S109 and thereafter. On the other hand, if the nuclide is determined to be a nuclide other than helium ions in step S106 and it is determined in step S107 that there is a mismatch (no) (abnormal), the application of the high frequency to the high frequency electrode 11 for emission is stopped and the irradiation is interrupted ( Step S108).

In step S109, the irradiation position is set. The control device 30 excites the

scanning electromagnets

21A and 21B (FIG. 3) in the irradiation device 20 according to the target irradiation position of the spot data, and the electromagnets of the path switching device 40 so that helium ions reach the irradiation device 20. Control the amount of excitation.

In step S110, helium ion irradiation is performed. The control device 30 applies a high frequency to the emission high-frequency electrode 11. Helium ions circulating around the synchrotron 6b with a predetermined energy are emitted to the beam transport system 300 and reach the irradiation device 20 via the path switching device 40. The helium ions that have reached the irradiation device 20 are scanned by the

scanning electromagnets

21A and 21B, pass through the dose monitor 22 (FIG. 3) and the position monitor 23 (FIG. 3), reach the affected area 18 of the patient 17, and determine the dose distribution. Form. The dose monitor 22 and the position monitor 23 measure the amount and position of the helium ions that have passed, and transmit the measurement results to the control device 30. When the amount of helium ions measured by the dose monitor 22 reaches the target irradiation amount of the spot data, the control device 30 stops the application of the high frequency to the extraction high-frequency electrode 11 and stops the emission of helium ions. The control device 30 collates the position of the helium ions measured by the position monitor 23 with the target irradiation position, and confirms that they match.

In step S111, it is determined whether there is an unirradiated spot with the same energy in the spot data. When it is determined in step S111 that there is an unirradiated spot (yes), the

scanning electromagnets

21A and 21B are excited so that the helium ions reach the next unirradiated spot (step S109), and the high-frequency electrode 11 for emission has a high frequency. To emit helium ions from the synchrotron 6b (step S110). The helium ions emitted from the synchrotron 6b reach the affected part 18 of the patient 17 similarly to the previous spot, and form a dose distribution. Thereafter, steps S109 to S111 are repeated until it is determined in step S111 that there is no unirradiated spot (no), thereby completing the irradiation of helium ions with the same energy.

In step S112, it is determined whether or not the spot data includes unirradiated energy of helium ions. If it is determined in step S112 that there is unirradiated energy (yes), the process returns to step S104. As in the case of irradiation with helium ions having the previous energy, the helium ions are accelerated to the next energy by the synchrotron 6b (step S104). The control device 30 controls the route switching device 40 to excite the electromagnet of the route switching device 40 so that helium ions reach the nuclide discrimination device 50 in the same manner as the previous energy (step S105), and then the high frequency electrode for emission A high frequency is applied to 11 and helium ions are emitted toward the nuclide discrimination device 50. The helium ions that have reached the nuclide discriminating device 50 lose energy while passing through the metal plate 53, and eventually stop in any of the metal plates 53 when the energy is lost. Since the energy of helium ions is lower than that in the previous irradiation, the number of metal plates 53 that pass through until the helium ions stop is smaller than in the previous time. The nuclide determination unit 52 determines the nuclide based on the energy per nucleon and the helium ion stop position (range) measured by the nuclide determination device 50 (step S106), and transmits the determination result to the control device 30. . After confirming that the ion source nuclide selected in step S102 matches the nuclide determined in step S106 (step S107), the control device 30 performs the same energy unirradiated spot in step S111 as in the previous energy. By repeating steps S109 to S111 until it is determined that there is no (no), irradiation of helium ions with the same energy is completed. Thereafter, the irradiation of helium ions is completed by repeating steps S103 to S112 until it is determined in step S112 that there is no unirradiated energy (no).

In step S113, it is determined whether or not there is an unirradiated nuclide in the spot data. In this embodiment, in order to irradiate carbon ions subsequent to helium ions, it is determined in step S113 that there is an unirradiated nuclide (yes), and the process returns to step S102.

In step S102, the carbon ion source 2 is selected. The controller 30 closes the helium ion source shutter 3 so that the carbon ions emitted from the carbon ion source 2 enter the linac 6a, controls the ion source switching device 5, and controls the carbon ion source shutter 4. open.

In step S103, the carbon ions are accelerated in the previous stage. The control device 30 accelerates the carbon ions emitted from the carbon ion source 2 with the linac 6a and emits them to the synchrotron 6b. The carbon ions incident on the synchrotron 6b go around in the synchrotron 6b.

In step S104, carbon ions are accelerated later. The control device 30 applies a high frequency to the high frequency acceleration electrode 10 and controls the amount of excitation of the deflection electromagnet 9 and a quadrupole magnet (not shown) to accelerate carbon ions to a predetermined energy.

In step S105, the control device 30 excites the electromagnet of the path switching device 40 such that the carbon ions reach the nuclide discrimination device 50.

In step S106, the ion nuclide is determined. The control device 30 applies a high frequency to the high frequency electrode 11 for emission, and emits carbon ions circulating in the synchrotron 6 b to the beam transport system 300 via the extraction deflector 12. The carbon ions emitted to the beam transport system 300 reach the nuclide discrimination device 50 via the path switching device 40. The carbon ions that have reached the nuclide discriminating device 50 lose energy while passing through the metal plate 53 (FIG. 2) like the helium ions, and eventually stop in any of the metal plates 53 when the energy disappears. The position (negation) of the metal plate 53 where the carbon ions are stopped is detected by the nuclide discrimination unit 52 as an electric signal flowing through the metal plate 53. The nuclide discrimination unit 52 enters the nuclide discrimination device 50 based on the energy per nucleon determined by the acceleration condition of the accelerator 200 (the synchrotron 6b) and the stop position (range) of the carbon ion measured by the nuclide measurement unit 51. The nuclide of the charged particles is discriminated, and the discrimination result is transmitted to the control device 30. Note that the number of metal plates 53 through which carbon ions pass is smaller than the number of helium ions through when compared under the condition that the energy per nucleon is equal. This is due to the property of charged particles that the heavier particles have a smaller range when the energy per nucleon is equal. After receiving the nuclide discrimination result, the controller 30 stops the emission of carbon ions from the synchrotron 6b to the beam transport system 300 by stopping the application of the high frequency to the extraction high-frequency electrode 11.

In step S107, it is determined whether or not the nuclide of the carbon ion source 2 selected in step S102 matches the nuclide determined in step S106. In step S106, the nuclide is determined to be a carbon ion, and in step S107, if it is determined to be coincident (yes) (normal), the affected part 18 of the patient 17 is irradiated with the carbon ion after step S109. On the other hand, if the nuclide is determined to be a nuclide other than the carbon ion in step S106 and it is determined that there is a mismatch (no) in step S107 (abnormal), the application of the high frequency to the high frequency electrode for emission 11 is stopped and irradiation is interrupted ( Step S108).

scanning electromagnets

21A and 21B in the irradiation device 20 according to the target irradiation position of the spot data, and controls the excitation amount of the electromagnet of the path switching device 40 so that the carbon ions reach the irradiation device 20. To do.

In step S110, irradiation with carbon ions is performed. The control device 30 applies a high frequency to the emission high-frequency electrode 11. Carbon ions circulating around the synchrotron 6b with a predetermined energy are emitted to the beam transport system 300 in the same manner as the helium ions, and reach the irradiation device 20 via the path switching device 40. The carbon ions that have reached the irradiation device 20 are scanned by the

scanning electromagnets

21A and 21B, pass through the dose monitor 22 and the position monitor 23, reach the affected area 18 of the patient 17, and form a dose distribution. Thereafter, similarly to helium ions, the irradiation of carbon ions is completed by repeating steps S105 to S112 until it is determined in step S112 that there is no unirradiated energy (no). In this embodiment, since there is no charged particle to be irradiated following the carbon ion, it is determined in step S113 that there is no unirradiated nuclide (no), and irradiation is completed (step S114).

In the present embodiment, the process for performing nuclide discrimination (steps S105 to S108) is performed after the energy change (step S104). However, the process may be performed after setting the irradiation position (step S109). As a result, the frequency of nuclide discrimination in treatment increases, and irradiation with higher reliability becomes possible.

~ Effect ~
Thus, every time the acceleration period of the synchrotron 6b is updated (the type or energy of the charged particles is changed), the charged particles are emitted toward the nuclide discriminating device 50, and the nuclide of the selected ion source and the synchrotron 6b are used. By confirming that the nuclides of the emitted charged particles coincide with each other, it is possible to reliably irradiate the charged particles determined in the treatment plan in the treatment of irradiating a plurality of types of charged particles.

~ Modification ~
Note that the nuclide measurement unit 51 of the nuclide discrimination apparatus 50 may be formed of a laminated ionization chamber as shown in FIG. The laminated ionization chamber 51 has a structure in which an air layer and a resin plate 54 coated with metal (or carbon) are alternately laminated in a beam path. A laminated ionization chamber power supply 55 is connected to one side of the metal (or carbon) coated on the resin plate 54, and since a voltage is applied, an electric field is generated in the air layer. The charged particles incident on the laminated ionization chamber 51 lose energy by mainly passing through the resin plate 54 and stop after passing through any of the resin plates 54. The charged particles ionize the air when passing through the air layer sandwiched between the resin plates 54. The ionized charge reaches the metal (or carbon) coated on the resin plate 54 under the influence of the electric field. The reached charge is detected by the nuclide discrimination unit 52. The nuclide discrimination unit 52 discriminates the type of charged particles based on the number (range) of the resin plates 54 from which charges are detected and the energy per nucleon. As described above, the nuclide measuring unit 51 configured of the laminated ionization chamber can amplify the detection signal of the nuclide discrimination unit 52 by the ionization action of the air layer, and therefore, the range can be measured with high accuracy even with a small amount of incident charged particles.

Further, the nuclide measurement unit 51 of the nuclide discrimination device 50 may be configured to include an ionization chamber 56 and a scintillator 57 as shown in FIG. The ionization chamber 56 and the scintillator 57 are each connected to the nuclide discrimination unit 52. When the charged particles pass through the ionization chamber 56, the ionized gas that fills the ionization layer of the ionization chamber 56 is ionized to generate charges. Since the charge generation amount is proportional to the energy loss dE / dx of the charged particles in the ionosphere, the energy loss dE / dx of the charged particles in the ionosphere is measured by detecting the charge amount. Furthermore, the amount of light emitted when the charged particles stop is detected in the scintillator 57 that is configured to be sufficiently thicker than the range of the charged particles. Since the amount of luminescence is proportional to the kinetic energy E of the charged particles, the kinetic energy E of the charged particles is measured by detecting the amount of luminescence. Here, the kinetic energy E of the charged particles corresponds to a value obtained by multiplying the energy per nucleon by the number of nucleons. The kinetic energy dE / dx of the charged particle at the kinetic energy E varies depending on the nuclide. Accordingly, the nuclide determination unit 52 determines the nuclide of the charged particle based on the energy loss dE / dx of the charged particle and the total energy E measured by the nuclide measurement unit 51. Alternatively, it is determined whether or not the desired nuclide is accelerated by comparing the charged particle energy Ecalc determined from the operation pattern of the accelerator with the measured total energy E of the charged particles.

In the nuclide discriminating apparatus 50, when the intensity of the beam is large and measurement for each particle is difficult, the following method is also effective. If the number of charged particles is N, the amount of energy loss measured by the ionization chamber 56 is N × dE / dx, and the total energy of the charged particles measured by the scintillator 57 is N × E. The nuclide determination unit 52 obtains (dE / dx) / E by dividing the energy loss amount N × dE / dx by the energy N × E. Next, the charged particle energy Ecalc is obtained based on the operation pattern of the accelerator, and the charged particle energy loss amount (dE / dx) calc in the charged particle energy Ecalc is calculated based on the Bethe calculation formula. Further, (dE / dx) calc is divided by Ecalc to obtain ((dE / dx) / E) calc. Finally, by comparing (dE / dx) / E and ((dE / dx) / E) calc, the nuclide determination unit 52 determines whether or not the desired nuclide is accelerated. Since the nuclide measurement unit 51 is configured to include the ionization chamber 56 and the scintillator 57 in this manner, the signal line connected to the nuclide determination unit 52 can be suppressed to two for the ionization chamber and the scintillator. The determination unit 52 can be manufactured at low cost.

Furthermore, as the nuclide measuring unit 51, a radiation measuring device capable of measuring the dose distribution in the transverse direction of the beam may be used. Radiation measuring instruments include wire chambers such as MWPC (Multi-Wire Proportional Chamber) and MWIC (Multi-Wire Ionization Chamber) and FPD (Flat-panel detector) that arranges measurement elements in a two-dimensional array. In this case, the same effect can be achieved. Hereinafter, a case where a wire chamber is used will be described as an example.

FIG. 9 is an enlarged configuration diagram of a nuclide discrimination device 50 including a wire chamber as the nuclide measurement unit 51. In FIG. 9, the wire chamber 51 includes a plurality of conducting wires 58 arranged at equal intervals perpendicular to the beam traveling direction in the ionosphere as charge collection electrodes, and each of the plurality of conducting wires 58 is connected to the nuclide discrimination unit 52. Has been. The nuclide discriminating unit 52 obtains a lateral distribution of the beam with the position of each conducting wire 58 as the horizontal axis and the charge collected by each conducting wire 58 as the vertical axis, and approximates this lateral distribution with a Gaussian distribution. A standard deviation σ is calculated. Next, the nuclide determination unit 52 compares the standard deviation σ and σtable, and searches for a nuclide that matches within the range of measurement accuracy of the wire chamber 51. Here, σtable is the standard deviation of the lateral distribution of the beam obtained by calculation or measurement for each combination of the nuclide type and the charged particle energy Tcalc determined by the operation pattern of the accelerator, and the nuclide type and energy Tcalc. As a two-dimensional table, the nuclide determination unit 52 is registered in advance. If the lateral distribution of the beam cannot be approximated by a Gaussian distribution, the distribution itself is registered instead of the standard deviation, the degree of coincidence with the measured distribution is obtained by gamma analysis, etc., and the nuclide is based on the degree of coincidence. May be determined. As described above, the nuclide discrimination device 50 can discriminate the nuclide of charged particles based on the lateral distribution of the beam measured by the radiation measuring instrument. Further, since the radiation measuring instrument can reduce the thickness in the beam traveling direction, the nuclide determination device 51 can be downsized by configuring the nuclide measuring unit 51 with the radiation measuring instrument.

<Second Embodiment>
FIG. 10 is an overall configuration diagram of a charged particle beam irradiation system according to the second embodiment of the present invention. 10, the difference from the charged particle beam irradiation system in the first embodiment shown in FIG. 1 is that the path switching device 40 and the nuclide discrimination device 50 are connected to the linac 6a and the synchrotron 6b. 7 is the point. In the present embodiment, the nuclide is discriminated using the nuclide discriminating apparatus 50 before entering the synchrotron 6b.

FIG. 11 is a flowchart showing irradiation control by the control device 30 in the present embodiment. In FIG. 11, the difference from the irradiation control in the first embodiment shown in FIG. 6 is that the process accompanying the nuclide discrimination (steps S105 to S108) is performed before the process of accelerating charged particles (step S104). It is a point to execute.

The nuclide discrimination unit 52 in the present embodiment is based on the energy per nucleon determined by the acceleration condition of the accelerator 200 (linac 6a) and the stop position (range) of helium ions measured by the nuclide measurement unit 51. The nuclide of charged particles incident on the device 50 is determined, and the determination result is transmitted to the control device 30. This makes it possible to determine the nuclide before accelerating the charged particles with the synchrotron 6b, and to suppress energy consumption until an abnormality (nuclide mismatch) is detected.

Further, since the charged particles incident on the nuclide discriminating apparatus 50 in the present embodiment are charged particles before being accelerated by the synchrotron 6b, the energy is lower than that of the charged particles accelerated and emitted by the synchrotron 6b. Therefore, the excitation amount of the electromagnet of the path switching device 40 can be reduced. In order to prevent the measurement accuracy of the range from deteriorating due to a decrease in the energy of incident charged particles and a decrease in the number of passing metal plates 53, the nuclide discrimination device 50 according to the present embodiment has a thickness. Needs to be configured to include a plurality of metal plates 53 (which are about a thin film).

<Third Embodiment>
FIG. 12 is a diagram showing an overall configuration diagram of a charged particle beam irradiation system according to the third embodiment of the present invention. 12 is different from the charged particle beam irradiation system in the first or second embodiment shown in FIG. 1 or 10 in that a nuclide discriminating apparatus 50 is installed in the irradiation apparatus 20. In FIG. 13, the expanded block diagram of the irradiation apparatus 20 in this Embodiment is shown. As shown in FIG. 13, in the configuration in which the nuclide discrimination device 50 is installed in the irradiation device 20, the beam path 25 reaching the affected part 18 of the patient 17 is changed by changing the excitation amount of the scanning electromagnets 21 A and 21 B. The beam path 26 reaches 50. Thereby, it is not necessary to provide the path switching device 40 in the first and second embodiments, and the configuration of the charged particle irradiation system is simplified.

FIG. 14 is a flowchart showing irradiation control by the control device 30 in the present embodiment. In FIG. 14, the difference from the irradiation control in the first embodiment shown in FIG. 6 is that the excitation amounts of the

scanning electromagnets

21A and 21B (FIG. 13) are changed in step S105.

<Other embodiments>
In the first to third embodiments, the example in which the present invention is applied to the treatment in which carbon ions and helium ions are combined has been described. However, the scope of the present invention is not limited to this, and other than these examples. The present invention can also be applied to treatment using a combination of charged particles. For example, when protons and deuterons are combined, a dose distribution that matches the shape of the affected area 18 can be formed with a small system by irradiating deuterons at shallow positions and irradiating protons at deep positions. In addition, deuterons composed of one proton and one neutron reach a range approximately twice that of helium ions when the energy per nucleon is equal. Therefore, when helium ions and deuterons are combined, helium ions are irradiated at shallow positions and deuterons are irradiated at deep positions, thereby forming a dose distribution that matches the shape of the affected area 18 in a small system. Can do.

In the first to third embodiments, the present invention is applied to a treatment that makes it particularly difficult to determine the type of charged particle, that is, a treatment that combines charged particles (carbon ions and helium ions) having the same charge mass ratio. However, the scope of application of the present invention is not limited to this example, and the present invention is applicable to treatments in which charged particles having different charge mass ratios are combined. In that case, it is necessary to provide a linac 6a for each type of charged particle. For example, a helium ion source that generates helium ions having a mass number of 4 and a charge number of 2 (charge mass ratio of 1/2) and a carbon ion that generates carbon ions of a mass number of 12 and a charge number of 4 (charge mass ratio of 1/3). Each ion source is provided with a linac, and the number of carbon ion charges is converted from 4 to 6 by a charge conversion device installed at the exit of the linac for carbon ions so that it enters the synchrotron. It is necessary to unify the charge mass ratio of charged particles to be ½.

In the first to third embodiments, an example using a synchrotron as an accelerator has been described. However, the present invention can also be applied to a system using a cyclotron.

In the first to third embodiments, the example in which the present invention is applied to the treatment in which a plurality of types of charged particles are irradiated from one direction has been described. However, the scope of the present invention is limited to this. Instead, the present invention can be applied to a treatment in which irradiation is performed from a plurality of directions. In that case, it is not always necessary to irradiate a plurality of types of charged particles from each direction, and may be limited to one type depending on the direction. Further, the number of charged particles irradiated to the same patient 17 may be one or plural.

In the first to third embodiments, the example in which the present invention is applied to the treatment of irradiating two types of charged particles (helium ions and carbon ions) has been described. However, the scope of the present invention is limited to this. However, the present invention can be applied to a treatment in which three or more kinds of charged particles are irradiated.

1: Helium ion source 2: Carbon ion source 3: Helium ion source shutter 4: Carbon ion source shutter 5: Ion source switching device 6a: Linac (pre-accelerator)
6b: Synchrotron (second stage accelerator)
7: Beam duct 8: Beam duct 9: Deflection electromagnet 10: High-frequency accelerating electrode 11: Extraction high-frequency electrode 12: Extraction deflector 13: Beam duct 14: Deflection electromagnet 15: Rotating gantry 16: Couch 17: Patient 18: Affected part 20 :

Irradiation devices

21A, 21B: Scanning electromagnet 22: Dose monitor 23: Position monitor 24: Beam axis 25: Beam path 26: Beam path 30: Controller 31: Database 40: Path switching device 50: Nuclide discrimination device 51: Nuclide measurement Unit 52: nuclide discrimination unit 53: metal plate 54: resin plate 55: power source 56 for laminated ionization chamber 56: ionization chamber 57: scintillator 58: conductor 60: dose distribution 61: dose distribution 70: Bragg peak 71: helium ion irradiation region 72 : Carbon ion irradiation region 73: Dose distribution 100: Charged particle generator 200: Accelerator 300: Beam Transmission system

Claims

An ion generator that generates multiple types of ions with different nuclides;
An accelerator for accelerating the ions supplied from the ion generator and emitting them as an ion beam;
A beam transport system for transporting an ion beam emitted from the accelerator;
An irradiation apparatus for irradiating an irradiation target with an ion beam transported by the beam transport system;
A charged particle irradiation system comprising: a nuclide discrimination device configured to discriminate a nuclide of ions supplied from the ion generation device.
The charged particle irradiation system according to claim 1,
The nuclide discrimination apparatus includes a nuclide measurement unit that measures a predetermined parameter depending on an ion nuclide.
The charged particle irradiation system according to claim 2.
The charged particle irradiation system, wherein the nuclide discriminating apparatus discriminates ion nuclides based on the predetermined parameter measured by the nuclide measuring unit and energy per nucleon determined by acceleration conditions of the accelerator.
The charged particle irradiation system according to claim 2.
The charged particle irradiation system, wherein the nuclide measuring unit is a radiation measuring instrument that measures a lateral distribution of an ion beam as the predetermined parameter.
The charged particle irradiation system according to claim 1,
A charged particle irradiation system, further comprising: a path switching device that switches a path from which ions generated by the ion generator reach the irradiation apparatus to a path to the nuclide discrimination apparatus.
The charged particle irradiation system according to claim 5.
The charged particle irradiation system, wherein the path switching device is installed in the beam transport system.
The charged particle irradiation system according to claim 5.
The accelerator includes a front stage accelerator and a rear stage accelerator,
The charged particle irradiation system, wherein the path switching device is installed in a path portion that connects the front-stage accelerator and the rear-stage accelerator.
The charged particle irradiation system according to claim 1,
The charged particle irradiation system, wherein the nuclide determination device is installed in the irradiation device.
The charged particle irradiation system according to claim 3.
The charged particle irradiation system, wherein the nuclide measurement unit is configured to measure a range until the ion beam stops as the predetermined parameter.
The charged particle irradiation system according to claim 9.
The nuclide measurement unit includes a plurality of metal plates arranged in an ion beam path, and measures the range based on a position of a metal plate where the ion beam is stopped among the plurality of metal plates. Charged particle irradiation system.
The charged particle irradiation system according to claim 9.
The nuclide measurement unit includes a plurality of resin plates coated with metal or carbon arranged in an ion beam path, and the range is based on the number of resin plates through which the ion beam passes among the plurality of resin plates. Charged particle irradiation system characterized by measuring
The charged particle irradiation system according to claim 2.
The charged particle irradiation system, wherein the nuclide measurement unit is configured to measure an energy loss and a total energy per unit thickness of the ion beam as the predetermined parameters.
The charged particle irradiation system according to claim 12,
The charged particle irradiation system according to claim 1, wherein the nuclide measurement unit includes an ionization chamber that detects an energy loss per unit thickness of the ion beam and a scintillator that detects the total energy of the ion beam.