JP2010032451A - Particle beam irradiation system - Google Patents

Abstract

In a particle beam irradiation system capable of irradiating a plurality of types of particle beams, a means for confirming the irradiation position of the particle beam is provided by one type of device.
A particle beam generating device that generates a plurality of types of particle beams, an irradiation device that emits particle beams to an irradiation target, and gamma rays generated from the irradiation target are detected based on the particle beams emitted from the irradiation device. A plurality of gamma ray detectors 203a and 203b, a signal processing device 209 for discriminating whether the gamma ray detection signal from the gamma ray detector is caused by an prompt gamma ray or a pair annihilation gamma ray, and the signal processing device 209 are judged to be caused by the prompt gamma ray. An irradiation field confirmation device for obtaining an irradiation field of the particle beam from the gamma ray detection signal and obtaining the irradiation field of the particle beam from the gamma ray detection signal determined to be caused by the pair annihilation gamma ray.
[Selection] Figure 2

Description

  The present invention relates to a particle beam irradiation system capable of irradiating a plurality of types of particle beams.

  A method for treating cancer by irradiating a cancer patient with a charged particle beam such as a proton beam is known. The charged particle beam accelerated by the charged particle beam generation device reaches the irradiation device in the irradiation chamber through the beam transport system, and the distribution is expanded by the irradiation device 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 gamma rays from positron emitting nuclides generated in the irradiation field are measured by positron tomography (PET) [non- Patent Document 1, Patent Document 1]. In Patent Document 1, a patient is irradiated with a charged particle beam, gamma rays emitted from a position stopped after irradiation are detected, and the irradiation position is monitored by image processing with a PET apparatus. Furthermore, as another means of confirming the irradiation field of the charged particle beam, a method of measuring prompt gamma rays generated from excited nuclei of carbon, oxygen, and nitrogen generated in the irradiation field using a gamma camera has been proposed [ Non-patent document 2].

JP-A-9-189769 J. Pawelke et al., “In-Beam PET imagin for the Control of Heavy-Ion Tumor THerapy” IEEE Trans. Nucl. Sci. 44 No. 4 (1997) Chul-Hee Min and Chan Hyeong Kim et al., `` Prompt gamma measurements for locating the dose falloff region in the proton therapy '' Appl. Phys. Let. 89 183517 (2006) Kaita Parodi, et al., “PET / CT imaging for treatment verification after proton therapy: A study with plastic phantom and metallic implants” Med. Phys. 34 419 (2007)

  Consider the case where a carbon beam is used as the charged particle beam. The distribution of positron emitting nuclides generated in the irradiation field by irradiating the irradiation target (such as an affected part of a cancer) with a carbon beam has a strong correlation with the irradiation position of the carbon beam. The PET apparatus can identify the position of the positron emitting nuclide with high spatial resolution through detection of pair annihilation gamma rays. Therefore, in a particle beam therapy system using a carbon beam, measurement of annihilation gamma rays using a PET apparatus is appropriate as a means for confirming the irradiation position.

  On the other hand, when a proton beam is used as the charged particle beam, the correlation between the distribution of positron emitting nuclides generated by proton irradiation and the irradiation position of the proton beam is weak. For this reason, it is difficult to confirm the irradiation position of the proton beam by measuring pair annihilation gamma rays [Non-patent Document 3]. However, the distribution of gamma-ray radionuclides generated by proton beam irradiation has a strong correlation with the proton beam irradiation position. Even if prompt gamma rays generated from gamma-ray radionuclides are measured by PET, the position of gamma-ray radionuclides cannot be specified. However, since the Compton camera (CPT) can specify the direction of the prompt gamma ray, the position of the gamma ray nuclide can be specified. Therefore, as a means for confirming the irradiation position of the proton beam, prompt gamma ray measurement using CPT is appropriate.

  Thus, in order to accurately confirm the irradiation position of the particle beam in the irradiated body, different devices and means are required depending on the type of particle. Therefore, in a particle beam irradiation system that can irradiate different types of particle beams, it is necessary to prepare a plurality of devices in order to confirm the irradiation position of the particle beam. With such an increase in the number of devices, there is a concern that the time required for device setting and device maintenance performed before and after the irradiation will increase, which will be a burden on the operator.

  A feature of the present invention is based on a particle beam generator that generates a plurality of types of particle beams, an irradiation device that emits particle beams generated by the particle beam generator to an irradiation target, and a particle beam emitted from the irradiation device A plurality of gamma ray detectors for detecting gamma rays generated from the irradiation target, a signal processing device for determining whether a gamma ray detection signal output from the gamma ray detector is caused by prompt gamma rays or pair annihilation gamma rays, and a signal processing device; When a gamma ray detection signal determined to be caused by an prompt gamma ray is input, the generation position of the prompt gamma ray based on the first particle beam is obtained from the gamma ray detection signal, and the gamma ray detection signal determined to be caused by a pair annihilation gamma ray is input. Then, there is an irradiation field confirmation device for obtaining a generation position of a pair annihilation gamma ray based on the second particle beam from the gamma ray detection signal.

  In a particle beam irradiation system capable of irradiating a plurality of types of particle beams, an appropriate means for confirming the irradiation position of the particle beam is provided by one type of device regardless of the particles to be irradiated. An increase in equipment necessary for confirming the irradiation position of the particle beam can be suppressed, and the burden on the operator can be reduced.

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

  A proton / carbon beam irradiation system which is a kind of particle beam irradiation system, which is a preferred embodiment of the present invention, will be described with reference to FIG. The proton / carbon beam irradiation system includes a proton / carbon beam generation apparatus 101, a beam transport apparatus 102, and a rotary irradiation apparatus 103.

  The proton / carbon beam generator 101 includes an ion source (not shown), a pre-stage accelerator (for example, a linear accelerator) 101a, and a synchrotron 101b. The ion source generates proton ions and carbon ions, and can change the type of ions generated for each irradiation. Proton ions or carbon ions generated in the ion source are first accelerated by the former accelerator 101a, and the former becomes a proton beam and the latter becomes a carbon beam. The proton beam or carbon beam emitted from the front stage accelerator 101a is accelerated to a predetermined energy by the synchrotron 101b and then emitted from the deflector for emission 102a to the beam path 102b of the beam transport device 102.

  A proton beam or a carbon beam is guided to the rotary irradiation device 103 through the beam path 102b. The rotary irradiation device 103 includes a rotating gantry (not shown) and an irradiation field forming device (hereinafter referred to as irradiation nozzle) 104. The irradiation nozzle 104 is installed in the rotating gantry and rotates with the rotation of the rotating gantry. A part of the beam path 102b is attached to the rotating gantry.

  The proton beam or carbon beam guided to the rotary irradiation device 103 passes through the irradiation nozzle 104 and is irradiated to the cancer affected part of the patient 105 lying on the patient couch 106. A room where the patient 105 is irradiated with the particle beam is referred to as an irradiation room.

  The detailed configuration of the irradiation chamber will be described with reference to FIG. The irradiation chamber is provided with a pair of robot arms 201a and 201b. Compton cameras (CPT) 203a and 203b are installed at the tips of the robot arms 201a and 201b, respectively. A signal processing device 209 connected to the CPTs 203a and 203b is connected to an information processing device (computer) 210. The robot arms 201a and 201b include movable portions 202a and 202b having degrees of freedom, and the CPTs 203a and 203b can be installed at a free position and angle with respect to the patient 205 lying on the patient couch 204. The movable parts 202a and 202b of the robot arms 201a and 201b are driven by a motor (not shown). In order to control the drive of the motor, the robot arms 201a and 201b are provided with a drive control device 206. The drive control device 206 includes a user interface (not shown) for operating the robot arms 201a and 201b.

In this embodiment, a Compton camera (CPT) is used as a gamma ray detector mounted on the robot arms 201a and 201b. The CPT is a gamma ray detector using Compton scattering, and can identify the energy of gamma rays, the incident position of gamma rays at the detector, and the position of the gamma ray source viewed from the detector. Furthermore, CPT can detect high energy gamma rays.
If the gamma ray energy, the incident position of the gamma ray at the detector, the position of the gamma ray source viewed from the detector can be specified, and a high energy gamma ray can be detected, the same effect can be obtained with other gamma ray detectors other than CPT. It is done.

  The first CPT 203a includes a first detector 207a made of a material having a small atomic number and a second detector 208a made of a material having a large atomic number. The second CPT 203b includes a first detector 207b made of a material having a small atomic number and a second detector 208b made of a material having a large atomic number. The roles of the first detectors 207a and 207b are to generate Compton scattering in the incident gamma rays, to specify the generation position of Compton scattering, and to measure the total kinetic energy of the generated scattered electrons. The roles of the second detectors 208a and 208b are to measure the total energy of the gamma rays scattered by the first detectors 207a and 207b, and to measure the incident positions of the scattered gamma rays at the second detectors 208a and 208b. is there. Therefore, in order to measure gamma rays with the CPTs 203a and 203b, the gamma rays must be incident in the order of the first detectors 207a and 207b and the second detector. For these reasons, the first detectors 207a and 207b are directed toward the gamma ray source, and the second detectors 208a and 208b are disposed behind the first detectors 207a and 207b when viewed from the gamma ray source. That is, the first detectors 207a and 207b are directed toward the patient 205 receiving the particle beam therapy, and the second detectors 208a and 208b are located behind the first detectors 207a and 207b when viewed from the patient 205 receiving the particle beam therapy. To place.

  In general CPT, the probability of causing Compton scattering in the first detector is not so great. Therefore, gamma rays that have not caused Compton scattering in the first detector may be incident directly on the second detector and detected. In that case, the incident position and energy of the gamma rays in the second detector can be discriminated, but the incident angle cannot be discriminated. Therefore, the direction of the gamma ray source cannot be specified by the CPT alone. In order to specify the direction of the gamma ray source with a single CPT, it is necessary to cause Compton scattering in the first scatterer.

  Even with a fixed irradiation device that does not use a rotating gantry, the same effects as in the present embodiment using the rotating irradiation device can be obtained. In this embodiment, a synchrotron is used as the accelerator used in the proton / carbon beam generator 101 shown in FIG. 1. However, a charged particle beam accelerator such as a cyclotron or a linac can obtain the same effect as this embodiment. It is done.

  Next, the principle of confirming the irradiation position of the particle beam in the patient will be described.

  When a high-energy particle beam is incident on a material, the particle beam excites nuclei in the material and generates a large number of gamma-ray emitting nuclides. In addition, gamma-ray radionuclides are also generated by a spallation reaction between particle beams and nuclei in matter. The generated radionuclide decays with a half-life determined for each nuclide, and emits high energy gamma rays such as several hundred keV to several tens MeV. This gamma ray is called prompt gamma ray. Prompt gamma rays emitted from the radionuclide penetrate to the outside of the material.

  Therefore, by detecting prompt gamma rays from the outside of the substance with a gamma ray detector and specifying the source of the gamma rays in the substance, the irradiation position of the particle beam inside the substance can be confirmed. That is, by detecting prompt gamma rays using a gamma ray detector and specifying the source of prompt gamma rays in the patient, the irradiation position of the particle beam in the patient can be confirmed.

  The energy of prompt gamma rays is about several hundred keV to several tens MeV. Therefore, the gamma ray detector is required to be able to detect gamma rays having energy of several hundred keV to several tens MeV. Also, the gamma ray detector is required to be able to identify the energy and the flying direction of prompt gamma rays.

  In this embodiment, CPT is used as a prompt gamma ray detector. As described above, in order to measure prompt gamma rays with the CPT, the prompt gamma rays incident on the CPT need to cause Compton scattering in the first detector. The Compton scattering probability of prompt gamma rays in the first detector of the CPT is not so large. However, since the amount of prompt gamma rays generated in the patient body during the irradiation of the particle beam is sufficiently large, CPT can secure the number of prompt gamma rays necessary for confirming the irradiation position of the proton beam.

The irradiation position of the particle beam in the patient can also be confirmed by measuring the annihilation gamma ray.
When a high-energy particle beam is incident on a material, a variety of positron emitting nuclides are generated by a spallation reaction between the particle beam and nuclei in the material. The generated radionuclide decays with a half-life determined for each nuclide, and emits continuous energy positrons. The energy of the positron is not so large, and usually stops with a few millimeters or less and annihilates with the electrons in the material. The pair annihilation generates a pair of gamma rays having energy of 511 keV in opposite directions.

  When a pair of pair annihilation gamma rays generated in opposite directions to each other are simultaneously measured with a PET apparatus, the generation position of the pair annihilation gamma rays in the substance can be specified. That is, when the pair annihilation gamma rays generated from the irradiated body are simultaneously measured using the PET apparatus, the irradiation position of the particle beam in the irradiated body can be confirmed.

  In order to detect pair annihilation gamma rays, in this embodiment, a pair of CPTs 203a and 203b provided in the irradiation chamber is used as one PET camera. Details will be described later.

  However, since the generation probability of the positron emitting nuclide by the proton beam just before the stop is not so large, the generation position of the positron emitting nuclide does not show a strong correlation with the irradiation position of the proton beam. Therefore, when the irradiated particle beam is a proton beam, it is difficult to accurately estimate the irradiation position of the proton beam by measuring the pair annihilation gamma rays.

  Unlike positron emitting nuclides, the generation position of gamma-ray emitting nuclides has a strong correlation with the irradiation position of proton beams. For example, the generation position of the gamma-decaying nuclide O16 and the like shows a strong correlation with the irradiation position of the proton beam. These nuclides are thought to be generated by electromagnetic interaction between proton beams and material nuclei. Prompt gamma rays are not an event in which a pair of gamma rays are generated in opposite directions to each other like annihilation gamma rays. Therefore, prompt gamma rays cannot be measured with a PET camera, and the position of the gamma ray radionuclide cannot be specified. As described above, the CPT is a measuring device that can detect prompt gamma rays having high energy and specify the position of the prompt gamma ray source. Accordingly, prompt gamma ray measurement using CPT is effective as a means for confirming the irradiation position of proton beams.

  When the irradiated particle is a carbon beam, the irradiated carbon beam itself may be turned into a positron emitting nuclide C11 by a nuclear fragmentation reaction with a nucleus in the material. Therefore, there is a strong correlation between the position where the positron emitting nuclide is generated and the position irradiated with the carbon beam. In addition, regarding the measurement of pair annihilation gamma rays, the PET camera is superior to the CPT in terms of detection efficiency and generation position specifying accuracy. Therefore, as a means for confirming the irradiation position of the carbon beam, measurement of pair annihilation gamma rays using a PET camera is effective.

  In this example, a carbon beam is used as a particle beam that shares irradiation with a proton beam. However, if the particle beam becomes a positron emitting nuclide by a nuclear fragmentation reaction or has a high probability of generating a positron emitting nuclide immediately before stopping, A similar effect can be obtained.

  Then, the procedure in which the particle beam irradiation system of a present Example confirms the irradiation position of the particle beam in a patient body is demonstrated.

  When the patient positioning performed before the irradiation of the particle beam is completed, the treatment planning apparatus has three types of information, i) the type of particles used for irradiation, ii) the planned dose distribution, and iii) the gantry rotation angle shown in FIG. This is transmitted to the drive control device 206 of the arms 201a and 201b. Information i) The type of irradiated particles is further transmitted to the signal processor 209 and the computer 210 connected to the CPTs 203a and 203b. The signal processing device 209 is a device that extracts gamma ray data measured by the CPTs 203 a and 203 b from the CPTs 203 a and 203 b and transmits the data to the computer 210. The computer 210 is a device for storing and analyzing gamma ray measurement data received from the signal processing device 209. Based on the analysis result by the computer 210, the operator confirms the irradiation position of the particle beam.

  The case where a proton beam is used for irradiation will be described. When a proton beam is used for irradiation (when the particle beam generated by the proton / carbon beam generator 101 is a proton beam), the particle beam irradiation system of the present embodiment measures prompt gamma rays generated in the patient body, Check the irradiation position of the proton beam.

  First, when the treatment planning device outputs information i) the type of irradiated particles (here, proton beam), the drive control device 206 of the robot arms 201a and 201b confirms that the proton beam is used for irradiation. The drive control device 206 that has confirmed that a proton beam is used for irradiation calculates the installation positions of the CPTs 203a and 203b that are appropriate for confirmation of the irradiation position.

  FIG. 3 illustrates an appropriate installation position of the CPTs 203a and 203b particularly when it is desired to confirm the vicinity of the end of the proton beam range when the proton beam is irradiated.

  A position 304 is the deepest position with respect to the direction of the beam axis 303 obtained when the planned dose distribution 302 of the proton beam 301 is projected onto the beam axis 303. The appropriate installation position of the CPT 203 a is a position where a straight line 307 connecting the position 304 and the center position 306 of the gamma ray detection surface in the CPT 203 a is perpendicular to the beam axis 303. At this time, the gamma ray detection surface of the CPT 203 a is parallel to the beam axis 303. The gamma ray detection surface in the CPT 203a is a surface facing the gamma ray source, that is, the patient, on the surface of the first detector 207a of the CPT 203a. In addition, it is better that the drive control device 206 brings the CPT 203a as close to the patient as possible without touching the patient.

  In accordance with these conditions, the drive control device 206 of the robot arms 201a and 201b in FIG. 2 first calculates the beam axis 303 in FIG. 3 from the iii) gantry rotation angle information obtained from the treatment planning device. Furthermore, the drive control apparatus 206 calculates the position 304 from the information of ii) plan dose distribution. Using the calculated beam axis 303 and position 304, the drive control device 206 of the robot arms 201a and 201b calculates appropriate installation positions of the CPTs 203a and 203b. When calculating the installation positions of the CPTs 203a and 203b, the drive control devices 206 of the robot arms 201a and 201b have two different positions so that the pair of robot arms 201a and 201b do not install the CPTs 203a and 203b at the same position. calculate.

  When the accurate positions of the CPTs 203a and 203b are calculated, the drive control device 206 automatically drives the robot arms 201a and 201b, and the CPTs 203a and 203b are installed at appropriate positions calculated by the drive control device 206. When the installation of the CPTs 203a and 203b is completed, the drive control device 206 transmits to the computer 210 that the installation of the CPTs 203a and 203b is completed. Receiving the completion of installation of the CPTs 203a and 203b, the computer 210 turns on the CPTs 203a and 203b and the signal processing device 209.

  The appropriate installation position of the CPT described with reference to FIG. 3 is effective particularly when it is desired to confirm the vicinity of the end of the proton beam range. When it is desired to check other irradiation positions, it may be better to place the CPT at a position different from the position described with reference to FIG. In such a case, the operator can install the CPTs 203a and 203b at arbitrary positions using the user interface provided in the drive control device 206 of the robot arms 201a and 201b shown in FIG.

  Obstacle sensors (not shown) are attached to the robot arms 201a and 201b. When the robot arms 201a and 201b move, the CPT 203a and 203b and the robot arms 201a and 201b are the other robot arm and other devices. The patient 205 is controlled so as not to touch. As described above, when the CPTs 203a and 203b are installed at arbitrary positions, the operator inputs an instruction signal to the user interface. When receiving an instruction signal from the user interface, the drive control device 206 drives the robot arms 201a and 201b and installs the CPTs 203a and 203b at arbitrary positions.

  If an appropriate movable mechanism is added, even if the CPT is installed in the rotating gantry or the patient couch, the same effect as in this embodiment using the robot arm can be obtained. If the CPT can be installed at a position desired by the operator, there is no need for a movable mechanism. Therefore, the CPT may be installed directly by the operator.

  Even when two or more pairs of CPTs are used, the same effect as in the present embodiment using one pair of CPTs can be obtained. By installing a plurality of CPTs, the number of gamma rays that can be detected increases, so that the generation position of the gamma rays can be obtained more accurately.

  When the installation of the CPTs 203a and 203b is completed and the CPTs 203a and 203b are turned on, the patient 205 can be irradiated with a proton beam. When the operator instructs the particle beam irradiation system to start the particle beam irradiation to the patient from the console of the particle beam irradiation system, an irradiation start signal is transmitted to the computer 210 shown in FIG. When the computer 210 receives the irradiation start signal, it instructs the signal processing device 209 to acquire measurement data from the CPTs 203a and 203b and transmit the measurement data to the computer 210, and starts measuring gamma rays.

  When proton irradiation to the patient 205 is started, prompt gamma rays are generated from the position where the patient 205 is irradiated with the proton beam.

  A procedure for detecting prompt gamma rays by CPT will be described with reference to FIG. 4 using CPT 203a as an example.

  The gamma rays (in this case, prompt gamma rays) 401 shown in FIG. 4 first enter the first detector 207a of the CPT 203a. In the present embodiment, the first detector 207 a includes a time projection chamber (hereinafter referred to as TPC) 403 and a micropixel chamber (μPIC) 406. The TPC 403 is filled with a gas for detecting radiation. When the prompt gamma ray 401 causes Compton scattering in the TPC 403, scattered electrons 404 are generated from the Compton scattered position. The gas in the TPC 403 is ionized by the scattered electrons 404, and secondary electrons 405 are generated along the locus of the scattered electrons 404. The scattered electrons 404 lose kinetic energy and eventually stop inside the TPC 403.

  An electric field is applied in one direction inside the TPC 403, and secondary electrons 405 generated by ionization move in a direction opposite to the direction of the electric field. The intensity of the electric field is adjusted so that the moving speed of the secondary electrons 405 is constant. At the destination of the secondary electrons 405, a device that can read the position of the charges in two dimensions is installed. In this embodiment, a micropixel chamber (μPIC) 406 is used. When the secondary electrons 405 reach the μPIC 406, an electrical signal (gamma ray detection signal) having an intensity proportional to the charge amount of the secondary electrons 405 is output to the signal processing device 209 of the CPT 203a. Further, the CPT 203a reads out the charges of the secondary electrons 405 detected at each position of the μPIC 406 at regular intervals. Therefore, the secondary electrons 405 generated at a position far from the μPIC 406 are read out as an electrical signal detected by the μPIC 406 at a later time than the secondary electrons 405 generated at a close position. By such a device, the TPC 403 can obtain the locus of the scattered electrons 404 in three dimensions.

  The amount of secondary electrons 405 generated is proportional to the energy loss of the scattered electrons 404. Therefore, when all the electrical signals obtained from the μPIC 406 are integrated, the energy dropped by the scattered electrons 404 in the TPC 403 can be specified. That is, the kinetic energy of the scattered electrons 404 can be specified.

  Some thin semiconductor detectors using silicon or the like can detect the incident position of electrons and the energy loss of electrons in the detector. A configuration in which a large number of such semiconductor detectors are stacked can also measure the trajectory and kinetic energy of scattered electrons. In the present embodiment, the TPC 403 is used as the first detector 207a. However, the same effects as in the present embodiment can be obtained even when a large number of semiconductor detectors are stacked.

  The prompt gamma ray 401b that has caused Compton scattering by the first detector 207a is incident on the second detector 208a after being scattered. In this embodiment, a scintillation counter 407 using an inorganic scintillator is considered as the second detector 208a. In order to increase the energy resolution and detection efficiency of the scattered gamma rays 401b, the inorganic scintillator is desired to be a substance having a large light emission amount and a high stopping power. In this embodiment, a GSO crystal 408 is used as an inorganic scintillator. The scintillation counter 407 includes a GSO crystal 408 and a multi-anode type photomultiplier tube 409.

  If the scintillator has a high stopping power and a large light emission amount, the same effect can be obtained even if it is not a GSO crystal. For example, LSO crystal, BGO crystal, PWO crystal, NaI crystal, CsI crystal, LaBr crystal, YSO crystal, and the like. The same effect can be obtained with an organic scintillator as long as it has a high stopping power and a large light emission amount.

  A GSO crystal (scintillator) 408 is finely segmented, and a photoelectric element 1 channel (not shown) of a multi-anode type photomultiplier tube 409 is connected to one segment 408a of the GSO crystal. When the scattered gamma ray 401b is incident on the scintillation counter 407, an electromagnetic shower (not shown) is caused in the GSO crystal 408 and eventually all of the light is photoelectrically absorbed. The GSO crystal 408 generates a number of photons (not shown) proportional to the absorbed energy of the electromagnetic shower. The generated photons are converted into electric signals by the photomultiplier tube 409. The magnitude of the electrical signal is proportional to the number of converted photons. That is, the energy of the electromagnetic shower in each segment 408a can be specified by the magnitude of the electrical signal (gamma ray detection signal) obtained from the photomultiplier tube 409. The electric signal is output to the signal processing device 209.

  Further, the energy gravity center position of the electromagnetic shower can be calculated from the electromagnetic shower energy obtained in each segment 408a. The energy gravity center position of the electromagnetic shower is set as the incident position of the scattered gamma ray 401b. Further, by integrating the electromagnetic shower energy obtained in each segment 408a, the energy of the scattered gamma ray 401b can be specified.

  Even when the GSO crystal 408 is not segmented, the incident position of the scattered gamma ray 401b can be specified. When multiple photomultiplier tubes or multi-anode photomultiplier tubes are connected to the GSO crystal, the center of gravity of the photon generation position in the crystal is calculated from the difference in the intensity of the electrical signal obtained from each photomultiplier tube. it can. The center of gravity of the photon generation position should match the position of the center of gravity of the electromagnetic shower. Therefore, the center of gravity of the photon generation position is the incident position of the scattered gamma ray 401b.

  In this embodiment, the multi-anode type photomultiplier tube 409 is used for the second detector 208a. Instead, a semiconductor element that converts light into an electric signal, such as an avalanche photodiode (APD) or a silicon photo diode, is used. The same effect can be obtained by using a multiplier (SiPM).

  Even with a semiconductor detector using a semiconductor with high stopping power (for example, cadmium tellurium) and capable of detecting the incident position of gamma rays, the energy of the scattered gamma rays and the incident position of the scattered gamma rays in the second detector can be specified. Therefore, even when such a semiconductor detector is used instead of the scintillation counter of this embodiment, the same effect as that of this embodiment can be obtained.

  Next, the procedure from data acquisition to irradiation position confirmation will be described with reference to FIG.

  The signal processing device 209 includes a determination device 506, a switching control device 511, a gate signal generation circuit 508, and an analog / digital converter (ADC) 507. The determination device 506 includes noise determination units 509a, 509b, 509c, and 509d, signal determination units 510a, 510b, and 510c, and particle beam determination units 512a, 512b, and 512c. The first detector 207a of the CPT 203a is connected to the noise determination unit 509a, and the second detector 208a is connected to the noise determination unit 509b. The first detector 207b of the CPT 203b is connected to the noise determination unit 509c, and the second detector 208b is connected to the noise determination unit 509d. The determination device 506 includes a number of noise determination units corresponding to the number of CPT detectors. A discriminator circuit or the like can be considered as the noise determination unit. A signal determination unit 510a connected to the noise determination units 509a and 509b is connected to the particle beam determination unit 512a. A signal determination unit 510b connected to the noise determination units 509c and 509d is connected to the particle beam determination unit 512b. A signal determination unit 510b connected to the noise determination units 509b and 509d is connected to the particle beam determination unit 512b. The particle beam determination units 512a, 512b, and 512c are connected to the gate signal generation circuit 508. A switching control device 511 is connected to the particle beam determination units 512a, 512b, and 512c. The ADC 507 is connected to the first detectors 207a and 207b, the second detectors 208a and 208b, the gate signal generation circuit 508, and the computer 210. In this embodiment, the signal determination unit 510 and the particle beam determination unit 512 are provided separately, but a single determination unit may have both functions.

  When the CPT 203a detects prompt gamma rays, the first detector 207a and the second detector 208a output gamma ray detection signals (analog electrical signals, hereinafter referred to as analog data signals) to the signal processing device 209, respectively. Similarly, when the CPT 203b detects prompt gamma rays, the first detector 207b and the second detector 208b output gamma ray detection signals (analog data signals) to the signal processing device 209, respectively. The signal processing device 209 converts the input analog data signal into a digital value (hereinafter referred to as a digital data signal) and transmits it to the computer 210.

  The analog data signals read from the CPTs 203a and 203b are first divided into two, one being sent to the determination device 506 and one being sent to the ADC 507. As will be described later, the determination device 506 determines whether the input analog data signal is a signal caused by a valid gamma ray. If it is determined that the signal is valid, the determination device 506 converts the input analog data signal into a digital signal (hereinafter referred to as trigger signal) and outputs the digital signal to the gate signal generation circuit 508. The gate signal generation circuit 508 to which the trigger signal is input outputs the gate signal to the gate input 507a of the ADC 507. When the ADC 507 receives the gate signal, the ADC 507 obtains the integrated intensity of the analog data signal from the first detectors 207a and 207b and the second detectors 208a and 208b while the gate signal is being transmitted, and converts it to a digital data signal. . The obtained digital data signal is transmitted to the computer 210 and stored in a memory (not shown) of the computer 210. When the ADC 507 receives analog data signals from the first detectors 207a and 207b and the second detectors 208a and 208b without receiving the gate signal, the ADC 507 does not convert the analog signal into a digital signal and does not transmit it to the computer 210. . As described above, the ADC 507 outputs the gamma ray detection signals from the first detectors 207a and 207b and the second detectors 208a and 208b to the computer 210 based on the gate signal.

  The condition for generating the gate signal is called a trigger condition. The determination device 506 outputs a digital signal (trigger signal) when the trigger condition is satisfied. The trigger signal is input to the gate signal generation circuit 508. The gate signal generation circuit 508 having received the trigger signal transmits the gate signal to the ADC 507.

  The trigger condition is changed by a digital signal output from the switching control device 511 (hereinafter referred to as a switching signal). The switching control device 511 receives i) irradiation particle information from the treatment planning device and stores it in a memory (not shown) provided in the switching control device 511. When the irradiated particle is a proton beam, the switching control device 511 outputs a switching signal.

  The noise determination unit 509 determines whether the analog data signal from the CPTs 203a and 203b has an intensity equal to or higher than a threshold set by the operator (or an intensity of a value in a preset range), and exceeds the threshold (or The analog signal within the setting range) is converted into a digital signal and output. When an analog data signal less than the threshold value (or outside the set range) is input, the noise determination unit 509 does not output the signal. That is, the noise determination unit 509 determines whether or not the gamma rays detected by the CPTs 203a and 203b have predetermined energy, and processes an analog data signal resulting from gamma rays having energy less than the threshold (out of the setting range) as noise. The noise determination unit 509 that has input a gamma ray detection signal equal to or greater than the threshold value outputs the generated digital signal to the signal determination unit 510. The operator can change the threshold value of the noise determination unit 509. The signal determination units 510a, 510b, and 510c and the particle beam determination units 512a, 512b, and 512c have a function of newly outputting digital signals when a plurality of digital signals are simultaneously input. However, when a digital signal is input to the solid input, the signal determination units 510a, 510b, and 510c and the particle beam determination units 512a, 512b, and 512c do not output a new digital signal.

  The signal determination unit 510a outputs a digital signal when digital signals derived from the analog data signals output from the first detector 207a and the second detector 208a of the CPT 203a are simultaneously input. That is, when the first detector 207a and the second detector 208a of the CPT 203a simultaneously output analog data signals, the signal determination unit 510a determines that these analog data signals are effective signals due to one gamma ray. And a function of outputting a digital signal. “Simultaneous” in the present specification indicates a predetermined period, which is a period that can be determined to be simultaneous. The digital signal output from the signal determination unit 510a is input to the particle beam determination unit 512a. In addition, a switching signal from the switching control device 511 is input to the particle beam determination unit 512a. Therefore, when a switching signal is input to the particle beam determination unit 512a, a digital signal from the signal determination unit 510a is output from the determination device 506 as a trigger signal. That is, when the irradiated particle is a proton beam, a digital signal from the signal determination unit 510a is output from the determination device 506 as a trigger signal.

  The signal determination unit 510b outputs a digital signal when digital signals derived from the analog data signals output from the first detector 207b and the second detector 208b of the CPT 203b are input simultaneously. That is, when the first detector 207b and the second detector 208b of the CPT 203b simultaneously output analog data signals, the signal determination unit 510b determines that these analog data signals are effective signals due to one gamma ray. And a function of outputting a digital signal. The digital signal output from the signal determination unit 510b is input to the particle beam determination unit 512b. In addition, a switching signal from the switching control device 511 is input to the particle beam determination unit 512b. Therefore, when a switching signal is input to the particle beam determination unit 512b, a digital signal from the signal determination unit 510b is output from the determination device 506 as a trigger signal. That is, when the irradiated particle is a proton beam, a digital signal from the signal determination unit 510b is output from the determination device 506 as a trigger signal.

  The signal determination unit 510c outputs a digital signal when digital signals derived from the analog data signal output from the second detector 208a of the CPT 203a and the second detector 208b of the CPT 203b are simultaneously input. The digital signal output from the signal determination unit 510c is input to the particle beam determination unit 512c. In addition, a switching signal from the switching control device 511 is input to the particle beam determination unit 512c. Therefore, when the switching signal is not input to the particle beam determination unit 512c, the digital signal from the signal determination unit 510c is output from the determination device 506 as a trigger signal. That is, when the irradiated particle is a carbon beam, a digital signal from the signal determination unit 510c is output from the determination device 506 as a trigger signal.

  That is, the trigger condition is determined by whether or not the irradiated particle is a proton beam.

  Therefore, the trigger conditions in the case of proton beam irradiation are from the first detectors 207a and 207b (precisely μPIC) and the second detectors 208a and 208b (exactly photomultiplier tubes) in the CPT 203a and 203b. At the same time, an analog data signal is output to the signal processing device 209. That is, prompt gamma rays cause Compton scattering in the first detectors 207a and 207b of the CPTs 203a and 203b, and scattered gamma rays are detected by the second detectors 208a and 208b of the CPTs 203a and 203b.

  When the trigger condition is satisfied, the determination device 506 outputs a trigger signal. The trigger signal is input to the gate signal generation circuit 508, and the gate signal generation circuit 508 outputs a gate signal. When a gate signal is input to the gate input 507a of the ADC 507, the analog data signal input to the ADC 507 while the gate signal is being transmitted (that is, the electrical signal intensity and photomultiplier tube obtained at each position of the μPIC at each time). The integrated intensity of the electrical signal intensity obtained in each channel is converted into a digital data signal. The obtained digital data signal is transmitted to the computer 210 and recorded as measurement data in a memory (not shown) of the computer 210. That is, when the signal processing device 209 determines that the gamma ray detection signals (analog data signals) output from the CPTs 203a and 203b are caused by prompt gamma rays, the signal processing device 209 converts the gamma ray detection signals into digital signals and outputs them to the computer 210. .

If the next trigger signal is input to the gate signal generation circuit 508 while the gate signal generation circuit 508 transmits the gate signal or the measurement data is recorded in the memory of the computer 210, the measurement data is recorded normally. May not be. Therefore, during transmission of the gate signal and recording of the measurement data, the signal determination unit 510a or the particle beam determination unit 512a, the signal determination unit 510b or the particle beam determination unit 512b, the signal determination unit 510c, or the particle beam determination unit 512c A signal is emitted. Even if the trigger condition is satisfied, the trigger is generated when the signal is transmitted to the signal determination unit 510a or the particle beam determination unit 512a, the signal determination unit 510b or the particle beam determination unit 512b, the signal determination unit 510c, or the particle beam determination unit 512c. No signal is sent.
When the transmission of the gate signal and the recording of the measurement data are completed, the solid signal transmitted to the signal determination unit is canceled.

  The computer 210 analyzes the measurement data recorded in the memory and identifies the source of prompt gamma rays. The computer 210 first uses the measurement data recorded in the memory to a) a position where Compton scattering is generated, b) a locus of scattered electrons, c) energy of scattered electrons, d) an incident position of scattered gamma rays in a scintillation counter, e ) Calculate the energy of scattered gamma rays. Next, the computer calculates the energy of the incident gamma rays and the incident direction of the incident gamma rays using the information of a) to e).

  When the flying direction is calculated, the position of the source of prompt gamma rays viewed from the CPTs 203a and 203b can be specified. The source position of prompt gamma rays is displayed on a display (display device) provided in the computer 210 as a one-dimensional, two-dimensional or three-dimensional image. The operator confirms the position irradiated with the proton beam by looking at the generation position image of the prompt gamma ray displayed on the display provided in the computer 210. As described above, when the computer 210 receives the gamma ray detection signal determined to be caused by the prompt gamma ray by the signal processing device 209, the computer 210 generates a generation position (generation source) of the gamma ray generated by the proton beam irradiation based on the gamma ray detection signal. ) As a radiation field confirmation device.

  When irradiation is completed, an irradiation end signal is transmitted to each device of the particle beam irradiation system. When the computer 210 receives the irradiation end signal, the measurement data stored in the memory is written into a file and stored on a recording medium provided in the computer 210. By reading the measurement data file stored on the recording medium, the computer 210 obtains the prompt gamma ray generation position (corresponding to the irradiation position of the proton beam on the patient), and re-images the generation position distribution based on the result. On the display.

  Furthermore, the computer 210 turns off the power of the CPTs 203a and 203b and the signal processing device 209. When the drive control unit 206 of the robot arms 201a and 201b shown in FIG. 2 confirms that the powers of the CPT 203a and 203b and the signal processing unit 209 are turned off, the drive control unit 206 of the robot arms 201a and 201b is connected to the CPT 203a and 203b and the robot. The arms 201a and 201b are housed in predetermined places in the irradiation chamber.

  As described above, prompt gamma rays are measured mainly during irradiation with particle beams. Although the amount of prompt gamma rays generated after completion of irradiation is reduced as compared with that during irradiation, it is also possible to measure prompt gamma rays after completion of irradiation. In that case, after the irradiation end signal is received by the computer 210, the measurement of prompt gamma rays is continued until the time desired by the operator elapses. When the time desired by the operator has elapsed, the measurement data is stored in the recording medium of the computer 210 shown in FIG. 5, and the power supplies of the CPTs 203a and 203b are turned off.

  Next, the case where the particle used for irradiation is a carbon beam (when the particle beam generated by the proton / carbon beam generator 101 is a carbon beam) will be described. In the particle beam irradiation system of the present embodiment, when the particle used for irradiation is a carbon beam, the irradiation position of the carbon beam in the patient body is confirmed by simultaneously measuring the pair annihilation gamma rays generated from the patient body.

  First, information i) The drive control device 206 of the robot arms 201a and 201b shown in FIG. 2 confirms that a carbon beam is used for irradiation, depending on the type of irradiated particle (here, carbon beam). The drive control device 206 of the robot arms 201a and 201b that has confirmed that the carbon beam is used for the irradiation calculates the installation positions of the CPTs 203a and 203b suitable for measuring the pair annihilation gamma rays generated from within the patient.

  FIG. 6 illustrates the installation positions of the CPT 203a (605a in FIG. 6) and 203b (605b in FIG. 6) suitable for confirming the vicinity of the end of the range of the carbon beam, particularly when irradiating the carbon beam.

  The deepest position with respect to the beam axis 603 direction obtained when the planned dose distribution 602 of the carbon beam 601 is projected onto the beam axis 603 is defined as a position 604. Appropriate installation positions of the CPTs 203a and 203b are positions where line segments 607a and 607b connecting the position 604 and the center positions 606a and 606b of the gamma ray detection surfaces of the CPTs 203a and 203b are perpendicular to the beam axis 603. The gamma ray detection surfaces of the CPTs 203a and 203b are parallel to the beam axis 603. Further, the pair of CPTs 203a and 203b are arranged such that the line segment 607a and the line segment 607b exist on the same straight line. That is, the pair of CPTs 203a and 203b are installed at positions facing each other. In addition, it is desirable that the CPTs 203a and 203b be as close as possible to the extent that they do not come into contact with the patient.

  Under these conditions, the drive control device 206 of the robot arms 201a and 201b in FIG. 2 first calculates the beam axis 603 in FIG. 6 from the information of iii) gantry rotation angle obtained from the treatment planning device. Further, ii) a position 604 is calculated from the planned dose distribution. Using the calculated beam axis 603 and position 604, the drive control device 206 of the robot arms 201a and 201b calculates appropriate installation positions of the CPTs 203a and 203b.

  The appropriate installation position of the CPT described with reference to FIG. 6 is effective particularly when it is desired to confirm the vicinity of the end of the range of the carbon beam. When it is desired to check other irradiation positions, it may be better to set the center positions of the opposing pair of CPTs to positions different from the positions described in FIG. In such a case, the operator can install the CPTs 203a and 203b at arbitrary positions using the user interface provided in the drive control device 206 of the robot arms 201a and 201b shown in FIG.

  When the accurate positions of the CPTs 203a and 203b are calculated, the drive control device 206 automatically drives the robot arms 201a and 201b, and the CPTs 203a and 203b are installed at appropriate positions calculated by the drive control device 206. When the installation of the CPTs 203a and 203b is completed, the drive control device 206 transmits to the computer 210 that the installation of the CPTs 203a and 203b is completed. Receiving the completion of installation of the CPTs 203a and 203b, the computer 210 turns on the CPTs 203a and 203b and the signal processing device 209.

  When the installation of the CPTs 203a and 203b is completed and the CPTs 203a and 203b are turned on, the patient 205 can be irradiated with carbon rays. When the operator instructs the particle beam irradiation system to start the particle beam irradiation to the patient from the console of the particle beam irradiation system, an irradiation start signal is transmitted to the computer 210 shown in FIG. When the computer 210 receives the irradiation start signal, it instructs the signal processing device 209 to acquire measurement data from the CPTs 203a and 203b and transmit the measurement data to the computer 210, and starts measuring gamma rays.

  When the patient 205 is started to irradiate the carbon beam, a pair annihilation gamma ray is generated from the position where the patient 205 is irradiated with the carbon beam.

  Next, a procedure for detecting pair annihilation gamma rays by CPT will be described.

  When the pair annihilation gamma rays do not cause Compton scattering directly at the TPC 403 which is the first detector of the CPT 203a shown in FIG. 4 and directly enters the scintillation counter 407 which is the second detector of the CPT, an electromagnetic shower is caused in the GSO crystal 408, Eventually all will be photoelectrically absorbed. The GSO crystal 408 generates a number of photons (not shown) proportional to the absorbed energy of the electromagnetic shower. The generated photons are converted into electric signals by the photomultiplier tube 409. The magnitude of the electrical signal is proportional to the number of converted photons. That is, the energy of the electromagnetic shower in each segment 408a can be specified by the magnitude of the electrical signal obtained from the photomultiplier tube 409. The electric signal is output to the signal processing device 209. Further, the energy gravity center position of the electromagnetic shower can be calculated from the electromagnetic shower energy obtained in each segment 408a. The energy gravity center position of the electromagnetic shower is set as the incident position of the pair annihilation gamma ray. Further, by integrating the electromagnetic shower energy obtained in each segment 408a, the energy of the pair annihilation gamma ray 401b can be specified. In this manner, the energy and incident position of the pair annihilation gamma ray are specified based on the same principle as when measuring the prompt gamma ray that is Compton scattered by the first detector.

  As described above, the position of the source of gamma rays cannot be specified with only one second detector. However, in this embodiment, a pair of CPTs are arranged opposite to each other around the position 604 shown in FIG. Therefore, when the pair annihilation gamma ray passes through the first detector without causing Compton scattering and is detected by the second detector, the pair annihilation gamma ray is incident on the second detector in the other CPT, and the pair annihilation gamma ray Energy and incident position are specified.

  When the incident positions of the pair annihilation gamma rays simultaneously detected by the two opposing second detectors are connected with a straight line, the generation position of the pair annihilation gamma ray can be specified to be somewhere linear. Furthermore, the source position of the pair annihilation gamma ray can be specified by overlapping the straight lines obtained by a plurality of events. As described above, when the pair of second detectors is used, the position of the source of the pair annihilation gamma rays can be measured. This is the same as the measurement principle of the pair annihilation gamma ray by the PET apparatus.

  The energy of the pair annihilation gamma ray is 511 keV. However, when the pair annihilation gamma ray causes Compton scattering in the first detector, the energy of the pair annihilation gamma ray measured in the second detector becomes less than 511 keV. Such pair annihilation gamma ray data is discarded as noise data at the stage of analysis by the computer 210 shown in FIG. Therefore, there is a concern that the first detector placed in front of the second detector for a patient that is a pair of annihilation gamma ray sources may hinder measurement of pair annihilation gamma rays. However, the probability of Compton scattering at the first detector is sufficiently small relative to the detector efficiency of the second detector. Accordingly, the fact that the first detector is disposed in front of the second detector with respect to the patient that is the source of the pair annihilation gamma ray does not hinder the measurement of the pair annihilation gamma ray by the second detector.

  Next, the procedure from data acquisition to irradiation position confirmation will be described with reference to FIG.

  As described above, the switching control device 511 receives i) irradiation particle information from the treatment planning device and stores it in the memory provided in the switching control device 511. If the irradiated particle is a carbon beam, the switching control device 511 stops outputting the switching signal.

  The analog data signals of the CPTs 203a and 203b input to the determination device 506 are converted into digital signals by the noise determination units 509a, 509b, 509c, and 509d. The noise determination units 509a, 509b, 509c, and 509d output a digital signal when an analog signal having an intensity equal to or higher than a threshold set by the operator (or an intensity of a value within a preset range) is input. It has a function. The digital circuits output from the noise determination units 509a, 509b, 509c, and 509d are input to the signal determination units 510a, 510b, and 510c.

  The signal determination unit 510c outputs a digital signal when digital signals derived from the analog data signal output from the second detector 208a of the CPT 203a and the second detector 208b of the CPT 203b are simultaneously input. The digital signal output from the signal determination unit 510c is input to the particle beam determination unit 512c. In addition, a switching signal from the switching control device 511 is input to the particle beam determination unit 512c. Therefore, when the switching signal is not input to the particle beam determination unit 512c, the digital signal from the signal determination unit 510c is output from the determination device 506 as a trigger signal. That is, when the irradiated particle is a carbon beam, a digital signal from the signal determination unit 510b is output from the determination device 506 as a trigger signal.

  Therefore, the trigger condition in the case of carbon beam irradiation is that an analog data signal is simultaneously output to the signal processing device 209 from the second detector 208a (more precisely, a photomultiplier tube) of the CPT 203a and the second detector 208b of the CPT 203b. It is to be done. That is, when the second detectors 208a and 208b output analog data signals at the same time, these analog data signals are determined to be effective signals due to a pair of annihilation gamma rays and a digital signal is output.

  When the trigger condition is satisfied, the determination device 506 outputs a trigger signal. When the trigger signal is input to the gate signal generation circuit 508, the gate signal is output from the gate signal generation circuit 508. When a gate signal is input to the gate input 507a of the ADC 507, the analog data signal input to the ADC 507 while the gate signal is being transmitted (that is, the electric signal intensity and photomultiplier tube obtained at each position of the μPIC at each time). The integrated intensity of the electrical signal intensity obtained in each channel is converted into a digital data signal. The obtained digital data signal is transmitted to the computer 210 and recorded as measurement data in a memory (not shown) of the computer 210. As described above, when the signal processing device 209 determines that the gamma ray detection signals (analog data signals) output from the CPTs 203a and 203b are caused by the pair annihilation gamma rays, the signal processing device 209 converts the gamma ray detection signals into digital signals and outputs them to the computer 310. is doing.

  The computer 210 analyzes the measurement data recorded in the memory. Since the irradiation particle is received from the treatment planning apparatus that the irradiated particle is a carbon beam, the computer 210 analyzes the measurement data using an algorithm different from that used in the proton beam irradiation, and identifies the source of the pair annihilation gamma ray. . The generation source position of the pair annihilation gamma ray is displayed on a display provided in the computer 210 as a one-dimensional, two-dimensional or three-dimensional image. The operator looks at the generation position image of the pair annihilation gamma ray displayed on the display provided in the computer 210 and confirms the position irradiated with the carbon beam. As described above, when the computer 310 receives the gamma ray detection signal determined to be caused by the pair annihilation gamma ray by the signal processing device 209, the computer 310 generates the generation position (occurrence of the gamma ray generated by the irradiation of the carbon ray based on the gamma ray detection signal. It has a function as an irradiation field confirmation device for obtaining a source.

  During irradiation, the count rate of prompt gamma rays is higher than the count rate of annihilation gamma rays, and measurement of the pair annihilation gamma rays by the second CPT detector is obstructed. Therefore, the measurement of pair annihilation gamma rays is performed mainly after the end of irradiation with less prompt gamma rays. Since the lifetime of positron emitting nuclides is longer than that of gamma-ray emitting nuclides, measurement of pair annihilation gamma rays is possible even after the end of irradiation.

  When the irradiation end signal is received by the computer 210 shown in FIG. 5, the measurement of the annihilation gamma ray is continued until the time desired by the operator has elapsed. When the time desired by the operator elapses, the measurement data stored in the memory is written into a file and stored on a recording medium provided in the computer 210. By reading the measurement data file stored on the recording medium, the computer 210 obtains the generation position of the annihilation gamma ray (corresponding to the irradiation position of the carbon beam on the patient), and based on the result, re-images the generation position distribution. Can be displayed on the display.

  Furthermore, the computer 210 turns off the power of the CPTs 203a and 203b and the signal processing device 209. When the drive control device 206 of the robot arms 201a and 201b shown in FIG. 2 confirms that the power of the CPT 203a and 203b and the signal processing device 209 is turned off, the drive control device 206 of the robot arms 201a and 201b is connected to the CPT 203a and 203b and the robot. The arms 201a and 201b are housed in predetermined places in the irradiation chamber.

  Hereinafter, another embodiment of the present invention will be described by taking a proton beam / carbon beam irradiation system, which is a kind of particle beam irradiation system, as an example.

  The proton / carbon beam irradiation system of the present embodiment has the same configuration as the proton beam / carbon beam irradiation system of the first embodiment, but the function of the signal processing device 209 is different from that of the first embodiment. As shown in FIG. 5, the signal processing apparatus 209 according to the first embodiment changes the trigger condition depending on the type of particles to be irradiated (carbon beam, proton beam, or the like). As described in Example 1, prompt gamma rays measured during proton beam irradiation are mainly during irradiation (ie, during particle beam emission), and paired annihilation gamma rays measured during carbon beam irradiation are after irradiation (ie, , While the particle beam emission is stopped). Therefore, the signal processing device 209 according to the present embodiment changes the trigger condition depending on whether or not the particle beam is being emitted. Hereinafter, functions different from those of the first embodiment will be described in detail.

  The switching control device 511 of the present embodiment receives a particle beam emission on / off signal from a control device (not shown) of the particle beam irradiation system, and stores it in a memory provided in the switching control device 511. When the particle beam irradiation system is emitting a particle beam, the switching control device 511 outputs a switching signal. In the case of the synchrotron, the output on / off signal may be an output start signal (output on signal) and an output stop signal (output off signal) for a high-frequency beam application device installed in the synchrotron.

  The signal determination unit 510a outputs a digital signal when digital signals derived from analog data signals output from the first detector 207a and the second detector 208a of the CPT 203a are simultaneously input. The digital signal output from the signal determination unit 510a is input to the particle beam determination unit 512a. In addition, a switching signal from the switching control device 511 is input to the particle beam determination unit 512a. Therefore, when a switching signal is input to the particle beam determination unit 512a, a digital signal from the signal determination unit 510a is output from the determination device 506 as a trigger signal. That is, when the particle beam is being emitted, a digital signal from the signal determination unit 510a is output from the determination device 506 as a trigger signal.

  The signal determination unit 510b outputs a digital signal when digital signals derived from the analog data signals output from the first detector 207b and the second detector 208b of the CPT 203b are input simultaneously. The digital signal output from the signal determination unit 510b is input to the particle beam determination unit 512b. In addition, a switching signal from the switching control device 511 is input to the particle beam determination unit 512b. Therefore, when a switching signal is input to the particle beam determination unit 512b, a digital signal from the signal determination unit 510b is output from the determination device 506 as a trigger signal. That is, when the particle beam is being emitted, a digital signal from the signal determination unit 510b is output from the determination device 506 as a trigger signal.

  The signal determination unit 510c outputs a digital signal when digital signals derived from analog data signals output from the second detector 208a of the CPT 203a and the second detector 208b of the CPT 203b are simultaneously input. The digital signal output from the signal determination unit 510c is input to the particle beam determination unit 512c. In addition, a switching signal from the switching control device 511 is input to the particle beam determination unit 512c. Therefore, when the switching signal is not input to the particle beam determination unit 512c, the digital signal from the signal determination unit 510c is output from the determination device 506 as a trigger signal. That is, when the particle beam is stopped from being emitted, a digital signal from the signal determination unit 510b is output from the determination device 506 as a trigger signal.

  That is, the trigger condition is determined by whether or not the particle beam is being emitted.

  The computer 210 records measurement data during extraction and measurement data during extraction stop in a memory as separate data. When the proton beam is irradiated, the computer 210 analyzes the measurement data during the particle beam emission, identifies the generation position distribution of prompt gamma rays, and confirms the irradiation position of the proton beam. When the carbon beam is irradiated, the computer 210 analyzes the data when the particle beam emission is stopped, identifies the generation position distribution of the pair annihilation gamma rays, and confirms the irradiation position of the carbon beam. Here, the “measurement data when particle beam emission is stopped” in the case of irradiation with a carbon beam may be measurement data for a certain period after the end of irradiation after receiving the irradiation end signal.

  As described above, when the trigger condition of the determination device 506 is switched while the particle beam is being emitted and stopped, the irradiation position confirmation unit suitable for the irradiation particle can be obtained with one device (that is, a pair of CPTs 203a and 203b). realizable.

  According to the present embodiment, the same effect as in the first embodiment can be obtained.

It is a block diagram of the proton and carbon beam irradiation system which is one suitable Example of this invention. It is a block diagram of an irradiation chamber where the patient shown in FIG. 1 receives irradiation of a particle beam. It is a figure explaining the installation position at the time of proton beam irradiation of the Compton camera shown in FIG. It is a block diagram of the Compton camera shown in FIG. It is a block diagram of the circuit which reads measurement data from the Compton camera shown in FIG. It is a figure explaining the installation position at the time of carbon beam irradiation of the Compton camera shown in FIG.

Explanation of symbols

101 proton / carbon beam generator 101a front accelerator 101b synchrotron 102 beam transport device 102a exit deflector 102b beam path 103 rotary irradiation device 104 irradiation field forming device 105, 205 patient 106, 204 patient couch 201a, 201b robot arm 202a, 202b Movable part 203a, 203b Compton camera 206 Drive control device 207a, 207b First detector 208a, 208b Second detector 209 Signal processor 210 Computer 301 Proton beam 302 Proton beam dose distribution 303, 603 Beam axes 306, 606a , 606b Center position 307 of gamma ray detection surface in Compton camera Straight line 401 Gamma ray 403 Time projection chamber 404 Scattered electron 405 Secondary electron 406 Micro Pixel chamber 407 Scintillation counter 408 GSO crystal 409 Photomultiplier tube 506 Judgment device 507 Analog digital converter 507a Gate input 508 Gate signal generation circuit 509a, 509b, 509c, 509d Noise judgment unit 510a, 510b, 510c Signal judgment unit 511 Switching control device 512a, 512b, 512c Particle beam determination unit 601 Carbon beam 602 Planned dose distribution 607a, 607b of carbon beam

Claims (7)

A particle beam generator for generating multiple types of particle beams;
An irradiation device for emitting the particle beam generated by the particle beam generator to an irradiation target;
A plurality of gamma ray detectors for detecting gamma rays generated from the irradiation object based on the particle beam emitted from the irradiation device;
A signal processing device for determining whether a gamma ray detection signal output from the gamma ray detector is caused by prompt gamma rays or pair annihilation gamma rays;
When the gamma ray detection signal determined to be caused by the prompt gamma ray by the signal processing device is input, the generation position of the prompt gamma ray based on the first particle beam is obtained from the gamma ray detection signal, and caused by the pair annihilation gamma ray. A particle beam irradiation system comprising: an irradiation field confirmation device that obtains a generation position of a pair annihilation gamma ray based on a second particle beam from the gamma ray detection signal when the determined gamma ray detection signal is input. The signal processing device includes:
2. The particle according to claim 1, wherein it is determined whether the gamma ray detection signal is caused by an prompt gamma ray or an annihilation gamma ray in accordance with a type of particle beam generated by the particle beam generator. X-ray irradiation system. The signal processing device includes:
When the irradiation device emits a carbon beam, it is determined that the gamma ray detection signal output from the gamma ray detector after the irradiation is terminated due to the pair annihilation gamma rays,
The irradiation field confirmation device
The particle beam irradiation system according to claim 1 or 2, wherein a generation position of the pair annihilation gamma rays is obtained based on the determined gamma ray detection signal. The signal processing device includes:
A noise determination unit that determines whether the gamma ray detected by the gamma ray detector has a predetermined energy based on the gamma ray detection signal;
A particle beam discriminating unit for discriminating whether the gamma ray detection signal is caused by prompt gamma rays or annihilation gamma rays according to the type of particle beam generated by the particle beam generator. The particle beam irradiation system according to any one of claims 1 to 3. The gamma ray detector is a Compton camera having a first detector and a second detector, and the irradiation field confirmation device comprises:
Based on the gamma ray detection signals from the first detector and the second detector, the generation position of the prompt gamma ray based on the first particle beam is obtained,
2. The particle beam irradiation system according to claim 1, wherein a generation position of a pair annihilation gamma ray based on the second particle beam is obtained based on a gamma ray detection signal from the second detector. A particle beam generator for generating multiple types of particle beams;
An irradiation device for emitting the particle beam generated by the particle beam generator to an irradiation target;
A plurality of gamma ray detectors for detecting gamma rays generated from the irradiation object based on the particle beam emitted from the irradiation device;
A particle beam irradiation system, wherein conditions for acquiring measurement data from the gamma ray detector are switched according to irradiation particles generated by the particle beam generator. A particle beam generator for generating multiple types of particle beams;
An irradiation device for emitting the particle beam generated by the particle beam generator to an irradiation target;
A plurality of gamma ray detectors for detecting gamma rays generated from the irradiation object based on the particle beam emitted from the irradiation device;
A particle beam irradiation system, wherein conditions for acquiring measurement data from a gamma ray detector are switched while the particle beam is emitted and stopped.

Images