JP2019184446A - Neutron beam measurement device, and neutron beam measurement method - Google Patents

Abstract

To provide a neutron beam measurement device and a neutron beam measurement method each of which allows for improvement in the measurement accuracy of the amount of thermal neutrons included in the neutron beam.SOLUTION: The detection result acquiring unit 31 acquires a first detection result from a first detection unit 16 detecting the amount of a neutron beam including a thermal neutron beam and epithermal neutron beam. In addition thereto, the detection result acquiring unit 31 acquires a second detection result from the second detection unit 17 detecting the amount of neutron beams of which the thermal neutron beam is cut. The second detection result thus shows the amount of neutron beams in a state in which the thermal neutron beam is cut, so that the difference between the first detection result and the second detection result shows the amount of thermal neutron beams included in the neutron beams. Therefore, the calculation unit 32 calculates the amount of thermal neutron beams included in the neutron beams based on the first detection result and the second detection result.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a neutron beam measurement apparatus and a neutron beam measurement method.

  In recent years, there is a technique in which treatment is performed using a neutron beam. For example, boron neutron capture therapy (BNCT) using a boron compound is known as a neutron capture therapy for irradiating a neutron beam to kill cancer cells. In boron neutron capture therapy, neutrons are irradiated to boron that has been previously taken up by cancer cells, and the cancer cells are selectively destroyed by scattering of heavy charged particles generated thereby.

  In order to measure the amount of neutron beams used for treatment in this way, for example, a neutron beam measuring apparatus disclosed in Patent Document 1 is used. In the neutron beam measuring apparatus disclosed in Patent Document 1, a detection unit detects a neutron beam and calculates the amount of neutron beam based on the detection result.

Japanese Patent Laid-Open No. 2006-166777

  Here, when the target is irradiated with a charged particle beam to generate a neutron beam, the neutron beam includes both a thermal neutron and an epithermal neutron. Since thermal neutrons are used in therapy, it is necessary to know the amount of thermal neutrons. However, since the above-described neutron beam measurement apparatus measures thermal neutrons and epithermal neutrons without distinction, it has been required to measure thermal neutrons more accurately.

  Accordingly, an object of the present invention is to provide a neutron beam measurement apparatus and a neutron beam measurement method that can improve the measurement accuracy of the amount of thermal neutrons contained in a neutron beam.

  A neutron beam measurement apparatus according to the present invention is a neutron beam measurement apparatus that measures the amount of neutron beams generated by irradiation of a charged particle beam to a target, and acquires a detection result from a detection unit that detects neutron beams. A detection result acquisition unit, and a calculation unit that calculates the amount of neutrons based on the detection result acquired by the detection result acquisition unit, the detection result acquisition unit includes a thermal neutron beam and an epithermal neutron beam A first detection result from the first detection unit for detecting the amount of the neutron beam, and a second detection result from the second detection unit for detecting the amount of the neutron beam from which the thermal neutron beam is cut, And the calculation unit calculates the amount of thermal neutrons contained in the neutron beam.

  The neutron beam measurement apparatus according to the present invention calculates the amount of neutron beams based on a detection result acquisition unit that acquires a detection result from a detection unit that detects a neutron beam and a detection result acquired by the detection result acquisition unit. A calculating unit. Here, a detection result acquisition part acquires the 1st detection result from the 1st detection part which detects the quantity of the neutron beam containing a thermal neutron beam and an epithermal neutron beam. In addition, the detection result acquisition unit acquires the second detection result from the second detection unit that detects the amount of the neutron beam from which the thermal neutron beam has been cut. Thus, since the 2nd detection result has shown the quantity of the neutron beam in the state where the thermal neutron beam was cut, the difference of the 1st detection result and the 2nd detection result is contained in a neutron beam The amount of thermal neutrons is shown. Therefore, the calculation unit calculates the amount of thermal neutrons contained in the neutron beam based on the first detection result and the second detection result. As described above, the measurement accuracy of the amount of thermal neutrons contained in the neutron beam can be improved.

  The neutron beam measuring device can attach and detach a filter that cuts thermal neutron beams, and performs detection as the first detection unit when the filter is removed, and as the second detection unit when the filter is attached. Detection is performed as a first detector that performs detection and a third detection unit that detects the amount of neutron beams including thermal neutrons and epithermal neutrons, and is provided separately from the first detector. A detection result acquisition unit that performs the first detection at the time of the first irradiation of the charged particle beam to the target performed with the filter removed from the first detector. The first detection result from the unit and the third detection result from the third detection unit are acquired, and the second of the charged particle beam to the target is performed in a state where the filter is attached to the first detector. The second detection result from the second detector at the time of irradiation And a third detection result from the third detection unit, and the calculation unit calculates a difference between the first detection result at the first irradiation and the second detection result at the second irradiation. Then, based on the ratio between the third detection result at the first irradiation and the third detection result at the second irradiation, the difference may be corrected to calculate the amount of thermal neutrons. As described above, the first detector and the second detector are combined into one detector by attaching and detaching the filter to the first detector and performing the first irradiation and the second irradiation. Can be used in combination. Here, the irradiation amount itself of the neutron beam generated from the target may change between the first irradiation and the second irradiation. However, even in such a case, the irradiation amount of the neutron beam generated from the target during the first irradiation and the second irradiation by the second detector separate from the first detector Is detected as a third detection result. Further, the calculation unit, based on the ratio of the third detection result at the first irradiation and the third detection result at the second irradiation, the first detection result at the first irradiation, The amount of thermal neutrons is calculated by correcting the difference from the second detection result during the second irradiation. Thereby, the calculation unit can calculate the amount of thermal neutrons after performing correction in consideration of the change in the irradiation amount itself of neutron beams generated from the target.

The neutron beam measurement apparatus is abnormal based on a storage unit that stores a ratio between the amount of thermal neutrons and the amount of epithermal neutrons at each timing, and changes in the ratio at the first timing and the ratio at the second timing. And a determination unit that performs the determination. Thereby, the determination unit can monitor that the ratio of the amount of thermal neutrons and the amount of epithermal neutrons is within a predetermined range, and can detect that an abnormality has occurred. .

  A neutron beam measurement method according to the present invention is a neutron beam measurement method for measuring the amount of neutron beams generated by irradiation of a charged particle beam onto a target, and includes a neutron beam including a thermal neutron beam and an epithermal neutron beam. A first detection result acquisition step for acquiring a first detection result for detecting the amount, and a second detection result acquisition step for acquiring a second detection result for detecting the amount of the neutron beam with the thermal neutron beam cut. And a calculation step of calculating the amount of thermal neutron beam contained in the neutron beam based on the first detection result and the second detection result.

  According to the neutron beam measurement method of the present invention, the same actions and effects as those of the neutron beam measurement apparatus described above can be obtained.

  In the neutron beam measurement method, in the first detection result acquisition step, the detector detects the amount of neutron beams at the time of the first irradiation of the charged particle beam to the target, and in the second detection result acquisition step, the target At the time of the second irradiation of the charged particle beam, a detector with a filter for cutting the thermal neutron beam may detect the amount of the neutron beam. As described above, the first detection result and the second detection result can be obtained by one detector by attaching / detaching the filter to / from the detector and performing the first irradiation and the second irradiation. it can.

  ADVANTAGE OF THE INVENTION According to this invention, the neutron beam measuring apparatus and neutron beam measuring method which can improve the measurement precision of the quantity of the thermal neutron contained in a neutron beam can be provided.

It is the schematic which shows the neutron capture therapy apparatus which generate | occur | produces the neutron beam used as the measuring object of the neutron beam measuring apparatus which concerns on embodiment of this invention. It is a block diagram of the neutron beam measuring device concerning this embodiment. It is a schematic block diagram which shows the specific structure of the neutron beam measuring apparatus shown in FIG. It is a flowchart which shows the processing content of the neutron beam measuring method which concerns on this embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First, an outline of a neutron capture therapy apparatus that generates a neutron beam to be measured by a neutron beam measurement apparatus according to an embodiment of the present invention will be described with reference to FIG. A neutron capture therapy device 1 shown in FIG. 1 is a device that performs cancer treatment using boron neutron capture therapy (BNCT). In the neutron capture therapy apparatus 1, for example, a neutron beam N is irradiated to a tumor of a patient (irradiated body) 50 to which boron ( ¹⁰ B) is administered.

  The neutron capture therapy apparatus 1 includes an accelerator 2. The accelerator 2 accelerates charged particles such as negative ions and emits a charged particle beam R. The accelerator 2 is configured by, for example, a cyclotron. In the present embodiment, the charged particle beam R is a proton beam generated by stripping charges from negative ions. The accelerator 2 generates a charged particle beam R having a beam radius of 40 mm and 60 kW (= 30 MeV × 2 mA), for example. The accelerator is not limited to a cyclotron, and may be a synchrotron, a synchrocyclotron, a linac, an electrostatic accelerator, or the like.

  The charged particle beam R emitted from the accelerator 2 is sent to the neutron beam generation unit M. The neutron beam generation unit M includes a beam duct 9 and a target 10. The charged particle beam R emitted from the accelerator 2 passes through the beam duct 9 and travels toward the target 10 disposed at the end of the beam duct 9. A plurality of quadrupole electromagnets 4 and scanning electromagnets 6 are provided along the beam duct 9. The plurality of quadrupole electromagnets 4 adjust the beam axis of the charged particle beam R using, for example, an electromagnet.

  The scanning electromagnet 6 scans the charged particle beam R and controls irradiation of the charged particle beam R to the target 10. The scanning electromagnet 6 controls the irradiation position of the charged particle beam R with respect to the target 10.

  The neutron capture therapy apparatus 1 generates a neutron beam N by irradiating the target 10 with the charged particle beam R, and emits the neutron beam N toward the patient 50. The neutron capture therapy apparatus 1 includes a target 10, a shield 8, a moderator 39, and a collimator 20.

  The target 10 generates a neutron beam N when irradiated with the charged particle beam R. The target 10 is a solid member formed of a material that generates a neutron beam when irradiated with a charged particle beam. Specifically, the target 10 is made of, for example, beryllium (Be), lithium (Li), tantalum (Ta), or tungsten (W), and has a disk-like solid shape with a diameter of, for example, 160 mm. Note that the target 10 is not limited to a disk shape, and may have another shape.

  A cooling member 120 is connected to the target 10. The cooling member 120 has, for example, a plurality of grooves on a contact surface that contacts the target 10, and cools the target 10 by flowing a cooling fluid through the grooves.

  The moderator 39 decelerates the neutron beam N generated by the target 10 (decreases the energy of the neutron beam N). The moderator 39 may have a laminated structure including a layer 39A that mainly decelerates fast neutrons contained in the neutron beam N and a layer 39B that mainly decelerates epithermal neutrons contained in the neutron beam N. .

  The shield 8 shields the generated neutron beam N and the gamma rays generated by the generation of the neutron beam N so as not to be emitted to the outside. The shield 8 is provided so as to surround the moderator 39. The upper part and the lower part of the shield 8 extend upstream of the charged particle beam R from the moderator 39.

  The collimator 20 shapes the irradiation field of the neutron beam N, and has an opening 20a through which the neutron beam N passes. The collimator 20 is a block-shaped member having an opening 20a at the center, for example.

Next, a detailed configuration of the neutron beam measurement apparatus 100 according to the present embodiment will be described with reference to FIG. The neutron beam measurement apparatus 100 is a measurement apparatus that measures the amount of neutron beam N generated by irradiating the target 10 with the charged particle beam R. Here, the neutron beam N generated by the target 10 includes a thermal neutron beam and an epithermal neutron beam. Thermal neutrons and epithermal neutrons are distinguished by the energy (that is, velocity) of the neutrons. For example, “thermal neutron: 0 <energy ≦ 0.5 eV”, “thermal neutron: 0.5 eV <energy <10 keV”, “fast neutron: 10 keV <energy” thermal neutron. A neutron beam in a state where a thermal neutron beam and an epithermal neutron beam are mixed may be referred to as a “mixed neutron beam”. In the description of the present embodiment, when “detecting a neutron beam” is used, it is not particularly distinguished whether a mixed neutron beam is detected or a thermal neutron beam is detected. When it is referred to as “detecting mixed neutron radiation”, it indicates that thermal neutron radiation and epithermal neutron radiation are detected. When it is referred to as “detecting a thermal neutron beam”, it indicates that a thermal neutron beam is detected among mixed neutron beams. However, when detecting a thermal neutron beam, most of the measurement objects may be a thermal neutron beam, and may include an epithermal neutron beam or a neutron beam in another band within the range of error. In addition, “quantity” in the case of “detecting the quantity” or “measuring quantity” of a neutron beam or the like may indicate the number of neutrons (count number). As a physical quantity indicating the number of neutrons, fluence (n / cm ² ) may be used. The fluence indicates the total sum of neutrons that have passed per unit area. The number of neutrons is also affected by the sensitivity of the detector.

  The neutron beam measuring apparatus 100 can accurately measure a thermal neutron beam in a mixed neutron beam. As shown in FIG. 2, the neutron beam measurement apparatus 100 includes a first detector 11, a second detector 12, and a control unit 30.

  The first detector 11 is a device that detects the amount of neutron beams. The first detector 11 is mainly a detector for obtaining a detection result for the controller 30 to calculate the amount of thermal neutron rays. The first detector 11 outputs the detection result to the control unit 30. An example of a specific configuration of the first detector 11 will be described later. In this embodiment, the 1st detector 11 can attach or detach the filter 13 which cuts a thermal neutron beam. Therefore, the first detector 11 detects the amount of the mixed neutron beam when the filter 13 is removed. In a state where the filter 13 is attached, the first detector detects the amount of the neutron beam whose thermal neutron beam has been cut by the filter 13. Most of the neutrons whose thermal neutrons are cut by the filter 13 (for example, 99% or more) are epithermal neutrons. As the filter 13, a member that shields thermal neutron rays and transmits epithermal neutron rays may be employed. For example, a cadmium filter, a lithium fluoride filter, a gadolinium filter, or a boron filter may be employed. The cadmium filter can cut almost 100% of thermal neutron rays.

  The first detector 11 is a single component as a device. However, since the detection target can be different before and after the filter 13 is attached / detached, the first detector 11 functionally includes two detection units. Yes. Accordingly, the first detector 11 with the filter 13 removed as shown in FIG. 2A detects the amount of mixed neutrons (thermal neutrons and neutrons including epithermal neutrons). Functions as the first detection unit 16. The first detector 11 with the filter 13 attached as shown in FIG. 2B functions as a second detector 17 that detects the amount of neutron beam from which the thermal neutron beam has been cut.

  The second detector 12 is a device that detects the amount of neutron beams. The second detector 12 is a detector mainly for grasping the entire irradiation amount of the neutron beam generated by the target 10. The second detector 12 outputs the detection result to the control unit 30. An example of a specific configuration of the second detector 12 will be described later. The second detector 12 is provided as a separate device from the first detector 11. The 2nd detector 12 functions as the 3rd detection part 18 which detects the quantity of the neutron beam containing a thermal neutron beam and an epithermal neutron beam.

  The control unit 30 controls the neutron beam measuring apparatus 100 as a whole. The control unit 30 includes a processor, a memory, a storage, a communication interface, and a user interface, and is configured as a general computer. The processor is an arithmetic unit such as a CPU (Central Processing Unit). The memory is a storage medium such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The storage is a storage medium such as an HDD (Hard Disk Drive). The communication interface is a communication device that implements data communication. The user interface is an output device such as a liquid crystal or a speaker, and an input device such as a keyboard, a touch panel, or a microphone. The processor controls the memory, storage, communication interface, and user interface, and realizes the function of the control unit 30 described later. In the control unit 30, for example, various functions are realized by loading a program stored in the ROM into the RAM and executing the program loaded in the RAM by the CPU. The control unit 30 may be composed of a plurality of computers.

  The control unit 30 includes a detection result acquisition unit 31, a calculation unit 32, a determination unit 33, and a storage unit 34.

  The detection result acquisition unit 31 acquires detection results from the detection units 16, 17, and 18 (that is, the detectors 11 and 12). The detection result acquisition unit 31 includes a first detection result from the first detection unit 16 that detects the amount of neutrons including thermal neutrons and epithermal neutrons, and a neutron beam from which the thermal neutrons have been cut. The second detection result from the second detection unit 17 for detecting the amount and the third detection result from the third detection unit 18 for detecting the amount of neutron beams including thermal neutron rays and epithermal neutron rays And get.

  Here, at the time of measurement, the first detector 11 performs detection twice, that is, detection with the filter 13 removed and detection with the filter 13 attached. Therefore, irradiation of the charged particle beam R to the target 10 performed with the filter 13 removed from the first detector 11 is referred to as “first irradiation”. Irradiation of the charged particle beam R to the target 10 performed with the filter 13 attached to the first detector 11 is referred to as “second irradiation”.

  The detection result acquisition unit 31 includes the first detector 11 from which the filter 13 is removed at the time of the first irradiation, that is, the first detection result from the first detection unit 16, and the second detector 12. That is, the third detection result from the third detection unit 18 is acquired. In the second irradiation, the detection result acquisition unit 31 includes the first detector 11 to which the filter 13 is attached, that is, the second detection result from the second detection unit 17, and the second detector 12. That is, the third detection result from the third detection unit 18 is acquired.

  The calculation unit 32 calculates the amount of neutron beams based on the detection result acquired by the detection result acquisition unit 31. The calculation unit 32 calculates the amount of thermal neutron rays included in the neutron beam based on the first detection result and the second detection result acquired by the detection result acquisition unit 31. As described above, the first detection result indicates the amount of neutrons including both thermal neutrons and epithermal neutrons. The second detection result indicates the amount of neutron beam from which thermal neutrons are cut. Therefore, the calculation unit 32 calculates the difference between the first detection result at the first irradiation and the second detection result at the second irradiation. Thereby, the calculation part 32 can calculate the quantity of the thermal neutron beam contained in a neutron beam by calculating based on such a difference.

  Here, as described above, the calculation by the calculation unit 32 is performed based on the detection result of the first irradiation and the second irradiation. Therefore, when the irradiation amount of the neutron beam generated by the target 10 is different between the first irradiation and the second irradiation, the amount of the thermal neutron beam included in the neutron beam at the time of the first irradiation, There is a difference between the amount of thermal neutrons included in the neutron beam during the second irradiation. On the other hand, the second detector 12 constituting the third detection unit 18 measures the irradiation amount itself of the neutron beam generated by the target 10 in both the first irradiation and the second irradiation. That is, the calculation unit 32 refers to the third detection result from the third detection unit 18, so that the irradiation amount of the neutron beam generated by the target 10 between the first irradiation and the second irradiation. It is possible to grasp how different are. Specifically, the calculation unit 32 calculates the ratio between the third detection result at the first irradiation and the third detection result at the second irradiation, thereby calculating the first irradiation and the first irradiation. It is understood how much the irradiation amount of the neutron beam generated by the target 10 differs between the irradiation of 2 and the irradiation of 2. Therefore, the calculation unit 32 calculates the first detection result at the first irradiation based on the ratio between the third detection result at the first irradiation and the third detection result at the second irradiation. The amount of thermal neutrons is calculated by correcting the difference from the second detection result during the second irradiation. Thereby, the calculation unit 32 can calculate the amount of the corrected thermal neutron beam. The calculation unit 32 can display the calculation result on a display unit such as a monitor.

  Since the calculation part 32 can grasp | ascertain the quantity of a thermal neutron beam as mentioned above, it can grasp | ascertain the quantity of an epithermal neutron beam. Therefore, the calculation unit 32 can calculate the ratio between the amount of thermal neutrons and the amount of epithermal neutrons. The calculation unit 32 transmits the calculated ratio to the storage unit 34. The measurement and calculation as described above are repeatedly performed at each timing when the neutron capture therapy apparatus 1 is inspected. Therefore, the memory | storage part 34 memorize | stores the ratio of the quantity of the thermal neutron beam in each timing, and the quantity of an epithermal neutron beam.

  The determination unit 33 can make an abnormality determination based on the ratio between the amount of thermal neutrons stored in the storage unit 34 and the amount of epithermal neutrons. That is, the neutron beam generated by the target 10 has no significant variation in the ratio between the thermal neutron beam and the epithermal neutron beam included in the neutron beam unless there is an abnormality. If there is a large variation in the value, it can be determined that some abnormality has occurred. The determination unit 33 performs abnormality determination based on a change in the ratio at any arbitrary timing (first timing) and the ratio at any other timing (second timing). The determination unit 33 can determine that there is an abnormality in at least one of the neutron capture therapy apparatus 1 and the neutron beam measurement apparatus 100, but cannot detect until there is an abnormality. Therefore, when the determination unit 33 makes an abnormality determination, an abnormal location may be specified using a separate abnormality determination mechanism.

  Note that the determination unit 33 may perform not only the above-described abnormality determination but also various abnormality determinations. For example, it is assumed that the irradiation amount of the whole neutron beam at the time of the first irradiation and the second irradiation, that is, the detection value of the second detector 12 constituting the third detection unit 18 may be different. Even though the neutron capture therapy apparatus 1 was scheduled to have the same dose for the first irradiation and the second irradiation, the detection of the second detector 12 in each irradiation is different. Either the neutron capture therapy apparatus 1 or the neutron beam measurement apparatus 100 is in an abnormal state. Therefore, the determination unit 33 may determine the abnormality. For example, the control unit 30 acquires the irradiation amount scheduled at the time of the first irradiation and the irradiation amount scheduled at the time of the second irradiation. The calculation unit 32 calculates the ratio between the irradiation amount scheduled for the first irradiation and the irradiation amount scheduled for the second irradiation. After the irradiation is performed, the calculation unit 32 calculates the ratio of the irradiation amount related to the actual measurement during the first irradiation and the second irradiation. The determination unit 33 may compare the planned dose ratio with the actual dose ratio, and determine that the difference is greater than or equal to a predetermined allowable value (for example, 3%) as abnormal. . When such an abnormality determination is not made, the calculation unit 32 corrects the difference between the first detection result at the time of the first irradiation and the second detection result at the time of the second irradiation to correct thermal neutrons. Calculate the amount of In addition, since it uses for the above calculations, the memory | storage part 34 may memorize | store the value of the scheduled irradiation amount scheduled at the time of each irradiation. Further, when the storage unit 34 stores and accumulates the planned dose, the determination unit 33 can detect an abnormality by monitoring the measured value while referring to the stored data. For example, when the measured value of thermal neutrons when set to a certain planned irradiation amount is greatly different from the measured value when irradiation was performed with a similar planned irradiation amount in the past, the determination unit 33 performs abnormality determination Can do.

  An example of a specific configuration of the neutron beam measurement apparatus 100 will be described with reference to FIG. The first detector 11 includes a scintillator 41A, an optical fiber 42A provided at the tip of the scintillator 41A, and a photodetector 43A that detects light transmitted from the optical fiber 42A. The detection result by the photodetector 43A is input to the measuring device 46 via the electric cable 44A. The measurement device 46 converts the detection result from the first detector 11 into a predetermined measurement value, and then transmits it to the control unit 30. The control unit 30 acquires the measurement value as a detection result from the first detector 11. Note that the control unit 30 may directly receive the detection result from the first detector 11 and internally perform the processing performed by the measurement device 46.

  The scintillator 41A is a phosphor that converts incident neutron beams into light. The scintillator 41 is disposed at a position facing the opening 20a of the collimator 20 and in contact with the neutron beam emitted from the opening 20a. In the scintillator 41A, the internal crystal is in an excited state according to the dose of incident neutron rays, and generates scintillation light. Therefore, the control unit 30 can calculate the amount of neutron beams based on the light generated by the scintillator 41A. The scintillator 41 is provided with a mechanism that allows the filter 13 to be attached and detached. The filter 13 is provided so as to cover the scintillator 41. In addition to the scintillation detector, an ion chamber, a gas chamber, a semiconductor detector, a proportional coefficient tube, or the like may be employed as the first detector 11. The filter 13 may not completely cover the scintillator 41 for structural reasons. In this case, a trace amount of thermal neutrons enters the scintillator 41, but the calculation unit 32 may have a function of correcting and calculating such a trace amount of thermal neutrons.

  The second detector 12 includes a scintillator 41A, an optical fiber 42A, and a scintillator 41B having the same meaning as the photodetector 43A, an optical fiber 42B, and a photodetector 43B of the first detector 11. The second detector 12 has the same configuration as the first detector 11 except that the filter 13 is not attached to the scintillator 41B.

  Next, the processing content of the neutron beam measurement method according to the present embodiment will be described with reference to FIG. The process of FIG. 4 is a process executed by each component of the control unit 30. The content of the neutron beam measurement method is not limited to the example shown in FIG.

  First, the first measurement is performed in a state where the filter 13 is not attached to the first detector 11. The neutron capture therapy apparatus 1 irradiates the target 10 with a charged particle beam in this state (first irradiation). The first detector 11 detects the amount of neutrons including thermal neutrons and epithermal neutrons. During the first irradiation, the first detector 11 transmits the first detection result to the control unit 30 as the first detection unit 16. Thereby, the detection result acquisition part 31 performs the 1st detection result acquisition process which acquires the 1st detection result which detected the quantity of the neutron beam containing a thermal neutron beam and an epithermal neutron beam (step S10). . That is, in the first detection result acquisition step S10, the first detector 11 detects the amount of neutron beams at the time of the first irradiation of the charged particle beam to the target 10. During the first irradiation, the second detector 12 transmits a third detection result to the control unit 30 as the third detection unit 18. Therefore, the detection result acquisition unit 31 also acquires the third detection result at the time of the first irradiation.

  Next, the second measurement is performed with the filter 13 attached to the first detector 11. The neutron capture therapy apparatus 1 irradiates the target 10 with a charged particle beam in this state (second irradiation). The 1st detector 11 detects the quantity of the neutron beam from which the thermal neutron beam was cut. During the second irradiation, the first detector 11 transmits the second detection result to the control unit 30 as the second detection unit 17. Thereby, the detection result acquisition part 31 performs the 2nd detection result acquisition process which acquires the 2nd detection result which detected the quantity of the neutron beam from which the thermal neutron beam was cut (step S20). In the second detection result acquisition step S20, the first detector 11 with the filter 13 for cutting the thermal neutron beam attached at the time of the second irradiation of the charged particle beam to the target 10 determines the amount of neutron beam. To detect. During the second irradiation, the second detector 12 transmits a third detection result to the control unit 30 as the third detection unit 18. Therefore, the detection result acquisition unit 31 also acquires the third detection result at the time of the second irradiation.

  Next, the calculation unit 32 converts the neutron beam based on the first detection result acquired in the first detection result acquisition step S10 and the second detection result acquired in the second detection result acquisition step S20. A calculation step of calculating the amount of included thermal neutron rays is executed (step S30). In the calculation step S30, the calculation unit 32 calculates a difference between the first detection result acquired in the first detection result acquisition step S10 and the second detection result acquired in the second detection result acquisition step S20. Thus, the amount of thermal neutron beam is calculated.

  Next, the calculation unit 32 compares the third detection result acquired in the first detection result acquisition step S10 and the third detection result acquired in the second detection result acquisition step S20. A comparison process for grasping the difference in neutron dose between the first irradiation and the second irradiation is executed (step S40). In the comparison step S40, the calculation unit 32 calculates a ratio between the third detection result at the time of the first irradiation and the third detection result at the time of the second irradiation.

  Next, the calculation unit 32 performs the first irradiation based on the ratio between the third detection result at the first irradiation calculated in the comparison step S40 and the third detection result at the second irradiation. A correction step of correcting the difference between the first detection result at the time and the second detection result at the time of the second irradiation to calculate the amount of thermal neutrons is executed (step S50). Thereby, the calculation part 32 can calculate the quantity of the thermal neutron beam corrected in consideration of the difference in the irradiation quantity of the neutron beam at the time of the first irradiation and the second irradiation. Thus, the process shown in FIG. 4 ends.

  Next, operations and effects of the neutron beam measurement apparatus 100 and the neutron beam measurement method according to the present embodiment will be described.

  The neutron beam measurement apparatus 100 according to this embodiment includes a detection result acquisition unit 31 that acquires detection results from the detection units 16, 17, and 18 that detect neutron beams, and a detection result acquired by the detection result acquisition unit 31. And a calculation unit 32 that calculates the amount of neutron beam. Here, the detection result acquisition part 31 acquires the 1st detection result from the 1st detection part 16 which detects the quantity of the neutron beam containing a thermal neutron beam and an epithermal neutron beam. In addition, the detection result acquisition unit 31 acquires the second detection result from the second detection unit 17 that detects the amount of the neutron beam from which the thermal neutron beam is cut. Thus, since the 2nd detection result has shown the quantity of the neutron beam in the state where the thermal neutron beam was cut, the difference of the 1st detection result and the 2nd detection result is contained in a neutron beam The amount of thermal neutrons is shown. Therefore, the calculation unit 32 calculates the amount of thermal neutron rays contained in the neutron beam based on the first detection result and the second detection result. As described above, the measurement accuracy of the amount of thermal neutrons contained in the neutron beam can be improved.

  The neutron beam measuring apparatus 100 can attach and detach the filter 13 for cutting the thermal neutron beam. The neutron beam measuring apparatus 100 performs detection as the first detection unit 16 in a state in which the filter 13 is removed, and in the state in which the filter 13 is attached. The first detector 11 that performs detection as the second detection unit 17 and the third detection unit 18 that detects the amount of neutron beams including thermal neutron rays and epithermal neutron rays are used as the first detection. And the second detector 12 provided separately from the detector 11, and the detection result acquisition unit 31 charges the target 10 performed with the filter 13 removed from the first detector 11. At the time of the first irradiation of the particle beam, the first detection result from the first detection unit 16 and the third detection result from the third detection unit 18 are acquired, and the first detector 11 is filtered. 13 is performed with 13 attached. During the second irradiation of the charged particle beam to the get 10, the second detection result from the second detection unit 17 and the third detection result from the third detection unit 18 are acquired, and the calculation unit 32. Calculates the difference between the first detection result at the first irradiation and the second detection result at the second irradiation, the third detection result at the first irradiation, and the second irradiation The amount of thermal neutrons may be calculated by correcting the difference based on the ratio of the third detection result at the time. As described above, the filter 13 is attached to and detached from the first detector 11, and the first detection unit 16 and the second detection unit 17 are provided by performing the first irradiation and the second irradiation. One detector 11 can be used in combination. Here, the irradiation amount itself of the neutron beam generated from the target 10 may change between the first irradiation and the second irradiation. However, even in such a case, the neutron beam generated from the target 10 at the time of the first irradiation and the second irradiation by the second detector 12 separate from the first detector 11. Is detected as a third detection result. In addition, the calculation unit 32 calculates the first detection result at the first irradiation based on the ratio between the third detection result at the first irradiation and the third detection result at the second irradiation. The amount of thermal neutrons is calculated by correcting the difference from the second detection result during the second irradiation. Thereby, the calculation unit 32 can calculate the amount of thermal neutrons after performing correction in consideration of the change in the irradiation amount itself of the neutron beam generated from the target 10.

  The neutron beam measuring apparatus 100 is based on the storage unit 34 that stores the ratio of the amount of thermal neutron beam and the amount of epithermal neutron beam at each timing, and the change in the ratio at the first timing and the ratio at the second timing. And a determination unit 33 that performs abnormality determination. Thereby, the determination part 33 can monitor that the ratio of the amount of thermal neutrons and the amount of epithermal neutrons is within a predetermined range, and can detect that an abnormality has occurred. it can.

  The neutron beam measurement method according to the present embodiment is a neutron beam measurement method for measuring the amount of neutron beams generated by irradiation of a charged particle beam onto the target 10, and includes neutrons including thermal neutron beams and epithermal neutron beams. A first detection result acquisition step S10 for acquiring a first detection result for detecting the amount of rays, and a second detection for acquiring a second detection result for detecting the amount of neutron rays from which thermal neutron rays have been cut. A result obtaining step S20; and a calculation step S30 for calculating the amount of thermal neutron rays contained in the neutron beam based on the first detection result and the second detection result.

  According to the neutron beam measurement method of the present invention, the same actions and effects as those of the neutron beam measurement apparatus 100 described above can be obtained.

  In the neutron beam measurement method, in the first detection result acquisition step S10, the first detector 11 detects the amount of neutron beam at the time of the first irradiation of the charged particle beam to the target 10, and the second detection. In the result acquisition step S20, the first detector 11 with the filter for cutting the thermal neutron beam attached may detect the amount of neutron beam at the time of the second irradiation of the charged particle beam to the target 10. In this way, the filter 13 is attached to and detached from the first detector 11, and the first detection result and the second detection result are obtained by performing the first irradiation and the second irradiation. It can be obtained with one detector 11.

  The present invention is not limited to the embodiment described above.

  For example, in the above-described embodiment, the first detection unit 16 and the second detection unit 17 are shared by the single first detector 11. Instead of this, one detector functioning as the first detection unit 16 may be provided, and one detector functioning as the second detection unit 17 may be provided. In this case, the first detection result and the second detection result can be acquired simultaneously by one irradiation.

  DESCRIPTION OF SYMBOLS 1 ... Neutron capture therapy apparatus, 10 ... Target, 11 ... 1st detector, 12 ... 2nd detector, 13 ... Filter, 16 ... 1st detection part, 17 ... 2nd detection part, 18 ... 1st 3 detection units, 31 ... detection result acquisition unit, 32 ... calculation unit, 33 ... determination unit, 34 ... storage unit, 100 ... neutron beam measurement apparatus.

Claims (5)

A neutron beam measuring apparatus for measuring the amount of neutron beams generated by irradiation of a charged particle beam to a target,
A detection result acquisition unit for acquiring a detection result from a detection unit for detecting the neutron beam;
A calculation unit that calculates the amount of the neutron beam based on the detection result acquired by the detection result acquisition unit;
The detection result acquisition unit
A first detection result from a first detection unit that detects the amount of the neutron beam including a thermal neutron beam and an epithermal neutron beam, and a first detection unit that detects the amount of the neutron beam from which the thermal neutron beam has been cut. A second detection result from the two detection units,
The said calculation part is a neutron beam measuring apparatus which calculates the quantity of the said thermal neutron beam contained in the said neutron beam. A filter for cutting the thermal neutron beam is removable, and detection is performed as the first detection unit when the filter is removed, and detection is performed as the second detection unit when the filter is attached. A first detector for performing
A second detector that is detected as a third detection unit that detects the amount of the neutron beam including the thermal neutron beam and the epithermal neutron beam, and is provided separately from the first detector. And comprising
The detection result acquisition unit
The first detection result from the first detection unit at the time of the first irradiation of the charged particle beam to the target performed with the filter removed from the first detector, and the Obtaining a third detection result from the third detection unit;
The second detection result from the second detector at the time of the second irradiation of the charged particle beam to the target performed with the filter attached to the first detector, and the Obtaining the third detection result from the third detection unit;
The calculation unit
Calculating a difference between the first detection result at the time of the first irradiation and the second detection result at the time of the second irradiation;
Based on the ratio between the third detection result at the time of the first irradiation and the third detection result at the time of the second irradiation, the amount of the thermal neutron is calculated by correcting the difference. The neutron beam measuring apparatus according to claim 1. A storage unit for storing a ratio between the amount of the thermal neutron beam and the amount of the epithermal neutron beam at each timing;
The neutron beam measuring apparatus according to claim 1, further comprising: a determination unit configured to perform abnormality determination based on a change in the ratio at the first timing and the ratio at the second timing. A neutron beam measurement method for measuring the amount of neutron beams generated by irradiation of a charged particle beam to a target,
A first detection result acquisition step of acquiring a first detection result of detecting the amount of the neutron beam including a thermal neutron beam and an epithermal neutron beam;
A second detection result acquisition step of acquiring a second detection result obtained by detecting the amount of the neutron beam from which the thermal neutron beam has been cut;
A neutron beam measurement method comprising: a calculation step of calculating an amount of the thermal neutron beam included in the neutron beam based on the first detection result and the second detection result. In the first detection result acquisition step, at the time of the first irradiation of the charged particle beam to the target, a detector detects the amount of the neutron beam,
In the second detection result acquisition step, the detector in a state in which a filter for cutting the thermal neutron beam is attached at the time of the second irradiation of the charged particle beam to the target detects the amount of the neutron beam. The neutron beam measurement method according to claim 4.

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