Measuring device and measuring method for measuring boron neutron capture treatment effect

Abstract

Provided is a BNCT-SPECT technique with which instant gamma rays generated by a BNC reaction can be measured in real time with excellent accuracy in BNCT. A measurement device for measuring a therapeutic effect in boron neutron capture therapy, the measurement device being provided with: a collimator in which holes of a predetermined shape are formed at equal intervals in the vertical and horizontal directions; detectors that are disposed in the deepest portions of the holes and that detect gamma rays that are promptly emitted by the irradiation of neutrons to boron; and an arithmetic processing unit that, when the gamma-rays are detected by the detector, distinguishes between a case where the gamma-rays are not detected by the other surrounding detectors at the same time and a case where the gamma-rays are not detected by the other surrounding detectors at the same time, and performs a simultaneous counting process or a non-simultaneous counting process to create a wave height distribution. The overall gamma-ray intensity distribution is displayed three-dimensionally.

Description

Technical Field

[0001] The present invention relates to a measuring device for measuring the effect of boron neutron capture therapy, and a measuring method for measuring the effect of boron neutron capture therapy using the measuring device. Background Art

[0002] In recent years, research toward the practical application of boron neutron capture therapy (BNCT) as a new cancer treatment method that will take on the next generation has accelerated (e.g., Patent Document 1), and its global spread is expected.

[0003] BNCT is a method that selectively accumulates boron in tumor cells (cancer cells). 10 B) Radiation therapy using external neutron irradiation. As a result of nuclear reactions with neutrons (mainly epithermal neutrons), charged particles (α particles and Li nuclei) emitted from boron have a range comparable to that of cells. Therefore, it has attracted attention as a treatment method that can selectively kill only cancer cells without harming normal cells.

[0004] However, there are several unresolved issues with the widespread use of BNCT. One of these is the inability to determine the treatment effects in real time during treatment (neutron irradiation).

[0005] To address this issue, the Japan Society for Neutron Capture Therapy proposed the SPECT (Single Photon Emission Computed Tomography) device (BNCT-SPECT). This device measures the 478 keV gamma rays emitted by lithium nuclei accompanying boron neutron reactions, creates a three-dimensional image, and allows for on-site observation.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: WO2018 / 181395 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] However, BNCT-SPECT is a measurement during treatment, which is different from conventional diagnostic SPECT. It has many restrictions on the measurement of physical quantities, making it difficult to implement and has not yet reached practical use.

[0011] That is, in conventional diagnostic SPECT, only the radiation source for measurement is used, so there is no background noise, and the S / N (signal / noise) ratio during measurement can be improved, allowing measurement with excellent accuracy.

[0012] In contrast, in the case of BNCT-SPECT, instead of measuring neutrons irradiated as a single radiation for treatment, it is necessary to measure the neutrons generated by the BNC reaction ( 10 B(n,α) 7 However, the intensity of these prompt gamma rays is much smaller than that of the primary radiation (neutrons) that constitutes the background (noise), making it difficult to measure them in real time with high precision to determine the therapeutic effect.

[0013] Furthermore, BNCT faces various constraints, including the need to deliver neutrons from close to the patient, the installation of various devices and instruments around the tumor and patient, and the inevitable changes in the patient's posture during treatment. Therefore, unlike X-ray CT, MRI, and conventional SPECT diagnostics, the SPECT device cannot be moved 360°. Consequently, it is difficult to measure treatment effectiveness in real time with exceptional accuracy.

[0014] Therefore, an object of the present invention is to provide a BNCT-SPECT technique capable of measuring prompt gamma rays generated by BNC reactions in real time with excellent accuracy during BNCT.

[0015] Means for solving problems

[0016] The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and have found that the above-mentioned problems can be solved by the invention described below, thereby completing the present invention.

[0017] The invention described in technical solution 1 is a measuring device for measuring the therapeutic effect of boron neutron capture therapy in which boron irradiation neutrons accumulated in advance in tumor cells kill the tumor cells. The measuring device is characterized in that it comprises: a collimator having holes of a given shape formed at equal intervals in the vertical and horizontal directions; a detector arranged in the deepest part of each of the holes to detect gamma rays emitted promptly by the irradiation of the boron by the neutrons; and an operation processing unit, the operation processing unit performing the following processing: when a gamma ray is detected by the detector, (1) when no gamma ray is detected by other detectors in the surrounding area at the same time, a wave height distribution is generated by the detected gamma ray, and (2) at the same time When gamma rays are detected by other detectors in the surrounding area, (2-a) when the total number of detected gamma rays is 3 or more, all signals are discarded and wave height distribution is not performed (non-simultaneous counting); (2-b) when the total number of detected gamma rays is 2, (2-b-a) when the total value of the two wave heights is within a given peak range, these two signals are discarded and the photoelectric peak count is increased by 1 (simultaneous counting); (2-b-b) when the total value of the two wave heights is not within a given peak range, these two signals are discarded (non-simultaneous counting), and the overall gamma ray intensity distribution is displayed three-dimensionally.

[0018] The invention described in Technical Solution 2 is characterized in that, in the measuring device described in Technical Solution 1, an incident order determination mechanism for determining the incident order of the gamma rays on the detector is provided in the arithmetic processing unit, and is configured to perform simultaneous counting processing only when it is determined that the detector on which the gamma rays first enter is incident.

[0019] The invention described in Technical Solution 3 is a measuring device described in Technical Solution 1 or Technical Solution 2, wherein a detector of a size that covers the entire detector is further provided on the back side of the detector as a detector for detecting transmitted gamma rays, and the measuring device is configured such that, when gamma rays are detected simultaneously by the detector for detecting transmitted gamma rays and one of the detectors, (1) when the total value of the wave heights of the two detected gamma rays is within a given peak range of the wave height distribution, the two detected signals are discarded, and the count of the photoelectric peak value is set to be detected by the detector and increased by 1 (simultaneous counting); and (2) when the total value of the two wave heights is not within the given peak range, the two detected signals are discarded (non-simultaneous counting).

[0020] The invention described in claim 4 is the measuring device described in claim 1 or 2, wherein the collimator is a tungsten collimator.

[0021] The invention described in claim 5 is the measuring device described in claim 1 or 2, wherein the hole of the collimator is formed in a square tube shape or a cylindrical shape.

[0022] The invention described in claim 6 is the measuring device described in claim 5 , wherein the hole of the collimator is formed in a square tube shape with a side of 3 to 5 mm or a cylindrical shape with a diameter of 3 to 5 mm.

[0023] The invention described in claim 7 is the measuring device described in claim 5 , wherein the length of the hole of the collimator is 20 to 35 cm.

[0024] The invention described in claim 8 is the measuring device described in claim 1 or 2, wherein the detector is a semiconductor detector or a scintillator.

[0025] The invention described in claim 9 is the measuring device described in claim 8 , wherein the detector is a GAGG (Ce) scintillator.

[0026] The invention described in technical solution 10 is a measurement method for measuring the therapeutic effect of boron neutron capture therapy using the measurement device described in technical solution 1, and the measurement method is characterized in that it comprises: a detection step, in which the detector detects the gamma rays that are incident on the hole of the collimator after being emitted instantaneously through a nuclear reaction with boron due to neutron irradiation; an operation processing step; and a display step, in which the intensity distribution of the entire gamma rays is three-dimensionally prepared and displayed based on the result of the operation processing step, in which, when the gamma rays are detected in the detection step, (1) when the gamma rays are not detected by other detectors in the surrounding area at the same time, the gamma rays are detected. 1 gamma ray is used to create a wave height distribution, (2) when gamma rays are detected by other detectors in the surrounding area at the same time, (2-a) when the total number of detected gamma rays is 3 or more, all signals are discarded and wave height distribution is not performed (non-simultaneous counting), (2-b) when the total number of detected gamma rays is 2, (2-b-a) when the total value of the two wave heights is within a given peak range, the two signals are discarded and the photoelectric peak count is increased by 1 (simultaneous counting), (2-b-b) when the total value of the two wave heights is not within a given peak range, the two signals are discarded (non-simultaneous counting).

[0027] The invention described in Technical Solution 11 is a measurement method described in Technical Solution 10. When the measurement device described in Technical Solution 2 is used to perform simultaneous counting processing in the calculation step, the order of incidence of the gamma rays on the detector is determined, and only the gamma rays determined to have entered the detector first are subjected to simultaneous counting processing.

[0028] The invention described in claim 12 is a measurement method described in claim 10 or claim 11, wherein the measurement device described in claim 3 is used, and for gamma rays detected by a transmission gamma ray detection detector provided on the back side of the detector, when the gamma rays are detected simultaneously by the transmission gamma ray detection detector and one of the detectors, (1) when the total value of the wave heights of the two detected gamma rays is within a given peak range of the wave height distribution, the two detected signals are discarded, and the count of the photoelectric peak value is set to be increased by 1 (simultaneous counting), and (2) when the total value of the two wave heights is not within the given peak range, the two detected signals are discarded (non-simultaneous counting).

[0029] The invention described in claim 13 is the measurement method described in claim 10 , wherein an accelerator BNCT is used as the neutron irradiation source.

[0030] Effects of the Invention

[0031] According to the present invention, a BNCT-SPECT technique capable of measuring prompt gamma rays generated by a BNC reaction in real time with excellent accuracy in BNCT can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram illustrating the principle of BNCT-SPECT.

[0033] Figure 2 A diagram illustrating the Compton effect and the photoelectric effect in BNCT-SPECT.

[0034] Figure 3 This is a diagram showing an example of the wave height distribution obtained by one detector (scintillator) in BNCT-SPECT.

[0035] Figure 4 This is a diagram showing an example of wave height distribution actually measured in BNCT-SPECT.

[0036] Figure 5 It is a diagram explaining simultaneous counting in BNCT-SPECT.

[0037] Figure 6 It is a diagram explaining non-simultaneous counting in BNCT-SPECT.

[0038] Figure 7 is the Compton electron E during Compton scattering 1c The electron energy E el and optoelectronics E 2c Energy E hν’ A graph showing the relationship between the increase and decrease of and the scattering angle.

[0039] Figure 8 (a) of the figure illustrates a state where a detector (scintillator) for detecting transmitted gamma rays is provided in one embodiment of the present invention, and (b) of the figure illustrates a path of prompt gamma rays. DETAILED DESCRIPTION

[0040] [1] Basic idea of the present invention

[0041] Before describing the specific aspects of the present invention, the basic idea (mechanism) of the present invention will be described.

[0042] 1. Principle of BNCT-SPECT

[0043] Figure 1 This is a schematic diagram illustrating the principle of BNCT-SPECT. Figure 1 In the figure, 1 denotes BNCT-SPECT, 11 denotes a collimator, and 12 denotes a detector (scintillator). Collimator 11 has holes 11a of a predetermined shape formed at equal intervals vertically and horizontally, with detector (scintillator) 12 positioned at the deepest portion. Detector (scintillator) 12 is also coupled to a photomultiplier tube (not shown) or MPPC (Multi-Pixel Photon Counter).

[0044] like Figure 1 As shown, in the tumor (cancer cell) inside the human body, by pre-intravenous administration of boron ( 10 B) BPA (Boronophenylalanine: 4-dihydroxyborylphenylalanine), BSH (disodiumMercaptoundecahydrododecaborate: Borocaptate) and other agents to accumulate boron ( 10 B).

[0045] Then, if an external neutron supply unit (not shown) is supplied to the boron ( 10 B) Irradiation with neutrons n will cause the following BNC reaction ( 10 B(n,α) 7 Li).

[0046] 10 B+n→ 7 Li+α+2.79MeV(6.1%)

[0047] 7 Li * +α+2.31MeV(93.9%)

[0048] The energy of the charged particles generated at this time (Eα = 1.47 MeV, ELi = 0.84 MeV (93.9% branching)) kills tumor cells. However, these charged particles have a range of approximately 10 μm, which, as mentioned above, is roughly the same size as human cells, making them less likely to harm adjacent normal cells. Compared to other radiation therapies, their sharpness is significantly higher, making them considered the only radiation therapy method with tumor cell selectivity. Furthermore, compared to charged particles, neutrons have a limited effect that is virtually incapable of killing normal cells.

[0049] The Li generated with a branching ratio of 93.9% is in an excited state ( 7 Li * ), instantaneous (with 10 -14 seconds) to the ground state 7 Li transition, emitting 478keV gamma rays (prompt gamma rays).

[0050] The intensity of this prompt gamma ray is the number of BNC reactions. Since it is clearly proportional to the radiation dose to the boron accumulated in the tumor, as long as the intensity distribution (wave height distribution) of the prompt gamma ray can be measured three-dimensionally by the SPECT device, the number of BNC reactions occurring in tumor cells can be estimated.

[0051] Since the number of BNC reactions is a parameter directly proportional to the therapeutic effect, the therapeutic effect can be known with excellent accuracy.

[0052] 2. Specific BNCT-SPECT Techniques

[0053] Next, a specific BNCT-SPECT technique will be described.

[0054] like Figure 1 As shown, in BNCT-SPECT 1, a detector (scintillator) 12 is placed at the deepest part of each hole 11a of a collimator 11. The collimator 11 converges gamma rays generated by neutron irradiation in parallel, thereby detecting multiple secondary gamma rays generated by the Compton effect and the photoelectric effect from the gamma rays incident on a single detector (scintillator) 12. In some cases, Compton-scattered gamma rays may be detected simultaneously by multiple adjacent detectors (scintillators) (a phenomenon known as crosstalk).

[0055] Figure 2 It is a diagram explaining the Compton effect and the photoelectric effect in the above-mentioned BNCT-SPECT.

[0056] (a) Compton effect

[0057] like Figure 2As shown in the example in the upper right section, a primary gamma ray (Eγ=478keV) incident from the surface 12a of a detector (scintillator) 12 collides with an electron inside the detector (scintillator) 12, causing the Compton electron E 1c (energy = 278keV) is generated and scattered gamma rays are generated (Compton scattering).

[0058] After the scattered gamma rays enter the adjacent detector (scintillator) 12, the photoelectrons E 2c (energy = 200keV) is generated. In addition, photoelectrons E 2c The energy of the scattered gamma ray (E hν’ ).

[0059] Compton Electronics E 1c Wako Electronics E 2c Both move at the speed of light, so they are detected simultaneously. In addition, their total energy E sum It becomes 478 (=278+200) keV, which is equal to the energy of the incident gamma ray Eγ478keV.

[0060] (b) Photoelectric effect

[0061] On the other hand, Figure 2 As shown in the lower right layer of FIG, gamma rays (Eγ = 478 keV) incident from the surface 12a of a detector (scintillator) 12 may not be scattered by electrons inside the detector (scintillator) 12, but photoelectrons E1 (energy = 478 keV) are generated by the photoelectric effect.

[0062] Figure 3 This is a diagram showing an example of the wave height distribution obtained by one detector (scintillator) based on the above. Figure 3 In the case of the Compton continuous part up to 478keV, the photoelectric peak is obtained at 478keV. In this case, the photoelectric peak at 478keV is required to confirm the therapeutic effect. 1c 、E 2c It's just noise.

[0063] 3. Difficulty of actual measurement

[0064] But if Figure 4 As shown in the figure, the actual measured wave height distribution has a peak value of 478keV near the peak value. 1 The Compton continuous part of 2223keV gamma rays emitted by H(n,γ) reaction, electron pair generation, and β +There is a lot of background noise, such as the 511keV gamma rays generated by the decay. Therefore, it is very difficult to separate these background noises and selectively measure only the 478keV gamma rays to obtain the absolute value and spatial distribution of the radiation dose with excellent accuracy. 1 The H(n,γ) reaction is produced by the reaction of water in the human body with neutron rays.

[0065] Figure 4 The wave height distribution shown is formed by combining the number of counts (Net) of the signal based on 478 keV gamma rays and the number of counts of background noise (BG). Therefore, in order to obtain the absolute value and spatial distribution of the radiation dose with excellent accuracy, it is necessary to use a small detector with high detection efficiency and appropriate energy resolution to minimize the number of counts of background noise (BG).

[0066] Specifically, the measurement accuracy (precision) is known to be expressed by the following (Formula 1). Therefore, it can be seen that if Net is increased as much as possible and BG is reduced as much as possible, the calculation result of (Formula 1) becomes a small value, and excellent accuracy can be obtained.

[0067] [Mathematical formula 1]

[0068]

[0069] 4. The solution in the present invention

[0070] (1) Simultaneous use of simultaneous / non-simultaneous counting methods

[0071] The inventors of the present invention believe that the signals measured simultaneously in the above crosstalk phenomenon (in the case of two signals, E 1c and E 2c ), the peak value to be measured in the obtained wave height distribution is determined to be 478keV as described above. Therefore, unnecessary signals are excluded by appropriately applying the simultaneous counting method and the non-simultaneous counting method corresponding to the measured peak value to seek improvement in accuracy.

[0072] Specifically, in E sum In the case of a given peak value (here 478keV) in the range (for example, 35keV is given as the full width at half maximum FWHM, but other numerical widths can be used as needed), instead of discarding both, as shown in the following example: Figure 5 As shown, the count of the photoelectric peak at 478 keV is increased by one (simultaneous counting process).

[0073] On the other hand, in E sum If the given peak value range is exceeded, both are discarded, e.g. Figure 6 As shown, wave height distribution is not performed (non-simultaneous counting processing).

[0074] Specifically, when a gamma ray is detected by a detector,

[0075] (1) When no gamma ray is detected by other detectors in the surrounding area, a wave height distribution is generated based on the detected gamma ray.

[0076] (2) When gamma rays are detected by other detectors in the surrounding area at the same time,

[0077] (2-a) If the total number of gamma rays detected is three or more, all signals are discarded and no wave height distribution is performed (non-simultaneous counting).

[0078] (2-b) When the total number of detected gamma rays is 2,

[0079] (2-b-a) When the sum of the two wave heights is within a given peak range, the two signals are discarded and the photoelectric peak count is incremented by 1 (simultaneous counting).

[0080] (2-b) If the sum of the two wave heights does not fall within a given peak range, the two signals are discarded (non-simultaneous counting).

[0081] In this way, by simultaneously utilizing simultaneous counting processing and non-simultaneous counting processing in the analysis of the actual measured wave height distribution, the number of counts of the photoelectric peak can be increased while the number of counts of the Compton continuous part can be reduced. As a result, since the Net count can be increased while the BG count can be reduced, the accuracy can be improved.

[0082] (2) Determination of incident elements during simultaneous counting

[0083] In the present invention, in order to improve the accuracy during the coincidence counting process, it is necessary to know which detector (scintillator) the signal first enters.

[0084] That is, as described above, the coincidence counting process is to count two signals (E 1c 、E 2c ) is processed by summing up the wave height values of the signal, but as SPECT, since the detector (scintillator) where the signal first enters indicates the detection location, it is necessary to know which one it is. 2c +E 1c =478keV, this signal becomes the signal to be measured, but it is necessary to know which detector this signal first enters.

[0085] However, since the two signals are measured simultaneously, it is necessary to determine which one is incident first, that is, to determine E 1cThe detector (scintillator) is technically impossible to realize and almost impossible to realize in practice.

[0086] Therefore, the inventors of the present invention focused on the scattering angle during Compton scattering. In other words, they focused on the photoelectron energy E during Compton scattering. el and the energy E of the scattered gamma ray hν’ There is a specific relationship between the increase and decrease of and the scattering angle.

[0087] Figure 7 is the energy E of the photoelectron during Compton scattering mentioned above. el and the energy E of the scattered gamma ray hν’ The relationship between the increase and decrease of E and the scattering angle is plotted by plotting E against the scattering angle θ (degrees). el 、E hν’ The obtained figure.

[0088] according to Figure 7 It can be seen that in the area up to the scattering angle of 64.6 degrees, E hν’ Must be greater than E el , can clearly distinguish E el and E hν’ It can be seen that the detector (scintillator) that measures electrons (photoelectrons) in the area surrounded by the thick dotted line (<166.5keV) has a high sensitivity due to the detection of E el Therefore, it is sufficient to determine that it is the detector (scintillator) where the gamma ray first entered. On the other hand, at an angle greater than 64.6 degrees, even if an electron with an energy of 200 keV is measured, it is not known whether it is E el Or E hν’ , it cannot decide which one it will hit first.

[0089] Furthermore, integrating the Klein-Nishina theoretical formula reveals that the probability of scattering in this region is 57%. Therefore, by combining this knowledge with the aforementioned simultaneous counting method, further improvement in accuracy can be achieved.

[0090] (3) Installation of detectors (scintillators) for transmitted radiation detection

[0091] The simultaneous / non-simultaneous counting method described above essentially utilizes signals from detectors (scintillators) other than the one detector (scintillator) on which the gamma rays are incident. However, after the incident gamma rays are scattered by the detector (scintillator), the scattered gamma rays may pass through intact, causing a decrease in accuracy.

[0092] The inventors of the present invention have devised a method for detecting transmitted gamma rays by installing an additional detector (scintillator) on the back side of the detector (scintillator) that is large enough to cover the entire detector (scintillator). This detector (scintillator) can be used to detect transmitted gamma rays. The inventors have also confirmed that the accuracy is further improved when the simultaneous and non-simultaneous counting method described above is used.

[0093] Figure 8 (a) in the figure illustrates a state where an additional detector (scintillator) 13 for detecting transmitted gamma rays is provided, and (b) in the figure illustrates the path of prompt gamma rays. Figure 8 In (a), a 65th detector (scintillator) 13 for detecting transmitted gamma rays is provided on the back side of 8×8=64 detectors (scintillators) 12, 12, 12, ...

[0094] In this case, if Figure 8 As shown in (b), the transmitted gamma ray detection detector (scintillator) 13 detects only the gamma rays that have passed through the detectors (scintillators) 12, 12, 12, ... in front. Specifically, when the transmitted gamma ray detection detector 13 detects, if there is no detector that counts at the same time, the signal is discarded. If there is a detector that counts at the same time, the gamma ray that enters the detector before the transmitted gamma ray detection detector 13 is called the incident detector. In fact, due to Figure 8 The phenomenon of single scattering (as shown in (b)) is more common, so this treatment can improve accuracy. Meanwhile, multiple scattering (two or more times) is less common, but in this case, the signal is discarded. This is because with multiple scattering, it is unclear which signal is incident first.

[0095] [2] Specific implementation methods

[0096] Next, the present invention will be described in detail based on specific embodiments.

[0097] 1. Preparation of BNCT-SPECT

[0098] First, make Figure 1 BNCT-SPECT 1 shown. In this embodiment, considering that the processing time of conventional BNCT is less than 1 hour, the design goal of BNCT-SPECT is to obtain a measurement result of less than 5 mm in a spatial resolution of less than 5% in a measurement of about 60 minutes.

[0099] The above-mentioned accuracy is defined as statistical accuracy, which is closely related to the performance of the detector (scintillator) used and is rigorously calculated using the Monte Carlo code MCNP5.

[0100] On the other hand, spatial resolution is defined as the diameter of the observation area in the detector (scintillator) located at a position away from the center of the tumor. However, it is closely related to the performance of the collimator and is rigorously calculated using the Monte Carlo code MCNP5.

[0101] (1) Collimator

[0102] As the collimator 11, a tungsten-made collimator 11a with a diameter of 3.5 mm and a length of 26 cm is used, with a hole pitch of 4.0 mm to form 8×8=64 collimators (size: 3.75×3.75×26 cm). In addition, as the collimator 11, in addition to tungsten, a collimator made of lead or heavy metal can also be used as needed. In addition, the number of holes 11a can also be appropriately changed as needed. In addition, there is no particular limitation on the shape of the hole 11a. Preferably, it is a square tube shape with a side of 3 to 5 mm or a cylindrical shape with a diameter of 3 to 5 mm. As for the length, it is preferably 20 to 35 cm.

[0103] (2) Detector (scintillator)

[0104] As the detector (scintillator) 12, a 3.5 × 3.5 × 30 mm GAGG (Ce) scintillator (Gadolinium Aluminum Gallium Garnet: Gd3Al2Ga3O 12 (Ce)) are arranged at the deepest part of each hole 11a of the collimator 11 (a total of 64). And, as Figure 8 As shown, on the back side of the 64 detectors (scintillators) 12 , a 3.75×3.75×1 cm GAGG (Ce) scintillator is arranged at intervals of 5 mm as the 65th transmitted gamma ray detection detector (scintillator) 13 .

[0105] As a detector, there are no particular limitations on semiconductor detectors or scintillators as long as they can detect prompt gamma rays. However, GAGG (Ce) scintillators are preferably used in view of the following points: a high density of 6.63 g / cm 3， It has high detection efficiency; the luminescence amount is as high as 60,000 photons / MeV, which has sufficient energy resolution; it is not deliquescent or hygroscopic, can be used even in high humidity, and is easy to dispose of; it has a high melting point and excellent temperature stability, and can maintain high luminescence even at high temperatures.

[0106] 2. BNCT-based treatment

[0107] Next, the neutron irradiation port is brought into close proximity with the patient's tumor so that it follows the wall from which neutrons are emitted, and the affected area is irradiated with neutrons. Furthermore, boron is previously accumulated in the patient's tumor as described above.

[0108] As described above, a BNC reaction is induced, tumor cells are killed, and treatment progresses, and prompt gamma rays are emitted.

[0109] 3. BNCT-SPECT Measurement

[0110] In addition, the BNCT-SPECT system is placed in close proximity to the patient's tumor on the opposite side of the wall, capturing images within a 90- to 180-degree range. Furthermore, the BNCT-SPECT system is preferably positioned so that an angle of 0 degrees relative to the neutron beam irradiation direction is avoided to prevent damage to the detector (scintillator) from the transmitted neutron beam.

[0111] A three-dimensional image of 478 keV gamma rays is created by performing simultaneous utilization processing using the aforementioned simultaneous / non-simultaneous counting method on the wave height distribution obtained by imaging, and the accuracy is calculated based on the aforementioned formula (1).

[0112] As described above, the obtained three-dimensional image represents the intensity distribution of prompt gamma rays. The intensity is proportional to the radiation dose to boron. Therefore, by analyzing the image in real time, the therapeutic effect of BNCT can be easily confirmed.

[0113] The inventors of the present invention have confirmed that a spatial resolution of 5.1 mm and a statistical accuracy of 4.4% can be obtained as a result of calculation and evaluation according to the present embodiment described above, and that results close to the original target values can be obtained.

[0114] The present invention has been described above based on the embodiment, but the present invention is not limited to the above embodiment. In addition, various modifications can be made to the above embodiment within the same or equivalent scope as the present invention.

[0115] Industrial applicability

[0116] The present invention is a world-leading technology developed for measuring prompt gamma rays with exceptional accuracy in real time to understand their therapeutic effects in BNCT-SPECT, a technique that has many limitations in measuring physical quantities and has not yet reached practical application. By establishing and utilizing irradiation protocols that deliver a sufficient radiation dose to tumors while minimizing harm to normal cells, the effects of treatment can be determined in real time and in three dimensions, enabling appropriate control of BNCT, thereby significantly improving treatment reliability.

[0117] Furthermore, the BNCT-SPECT according to the present invention is expected to contribute significantly to the popularization of BNCT by combining it with accelerator BNCT that utilizes an accelerator neutron source, which is currently gaining popularity.

[0118] Explanation of symbols

[0119] 1: BNCT-SPECT

[0120] 11: Collimator

[0121] 11a: Hole formed in the collimator

[0122] 12: Detector (scintillator)

[0123] 12a: Surface of detector (scintillator)

[0124] 13: Detector (scintillator) for detecting transmitted gamma rays.

Claims

1. A measuring device for measuring the therapeutic effect of boron neutron capture therapy in which boron previously accumulated in tumor cells is irradiated with neutrons to kill the tumor cells. The measuring device is characterized by comprising: A collimator having holes of a given shape formed at equal intervals in the vertical and horizontal directions; a detector disposed at the deepest portion of each of the holes and detecting prompt gamma rays generated by irradiation of the boron with the neutrons; and Operation processing unit, The processing unit performs the following processing: In the case where gamma rays are detected by the detector, (1) When no gamma ray is detected by other detectors in the surrounding area, a wave height distribution is generated based on the detected gamma ray. (2) When gamma rays are detected by other detectors in the surrounding area at the same time, (2-a) When the total number of gamma rays detected is 3 or more, all signals are discarded and no wave height distribution is performed, that is, non-simultaneous counting is performed. (2-b) When the total number of detected gamma rays is 2, (2-b-a) When the sum of the two wave heights is within a given peak range, the two signals are discarded and the photoelectric peak count is increased by 1, i.e., simultaneous counting is performed. (2-b-B) If the sum of the two wave heights is not within the given peak range, the two signals are discarded, i.e., non-simultaneous counting is performed. The overall gamma-ray intensity distribution is displayed three-dimensionally.

2. The measuring device according to claim 1, characterized in that The arithmetic processing unit is provided with an incident order determination mechanism for determining the incident order of the gamma rays on the detector. The measurement device is configured to perform coincidence counting processing only when the detector into which the gamma ray first enters is identified.

3. The measuring device according to claim 1 or 2, characterized in that Furthermore, a detector having a size that covers the entire detector is provided on the back side of the detector as a detector for detecting transmitted gamma rays. The measuring device is configured so that, when gamma rays are detected simultaneously by the transmission gamma ray detection detector and one of the detectors, (1) When the sum of the wave heights of two detected gamma rays is within a predetermined peak range of the wave height distribution, the two detected signals are discarded, the detection is deemed to be by the detector, and the photoelectric peak count is incremented by 1, i.e., simultaneous counting is performed. (2) When the sum of the two wave heights is not within a given peak range, the two detected signals are discarded, i.e., non-simultaneous counting is performed.

4. The measuring device according to claim 1 or 2, characterized in that The collimator is a tungsten collimator.

5. The measuring device according to claim 1 or 2, characterized in that The hole of the collimator is formed in a square tube shape or a cylindrical shape.

6. The measuring device according to claim 5, characterized in that The hole of the collimator is formed in a square tube shape with a side of 3 to 5 mm or a cylindrical shape with a diameter of 3 to 5 mm.

7. The measuring device according to claim 5, characterized in that The length of the hole of the collimator is 20 to 35 cm.

8. The measuring device according to claim 1 or 2, characterized in that The detector is a semiconductor detector or a scintillator.

9. The measuring device according to claim 8, characterized in that The detector is a GAGG (Ce) scintillator.

10. A measurement method for measuring the therapeutic effect of boron neutron capture therapy using the measurement device according to claim 1. The measuring method is characterized by comprising: a detection step of detecting, by the detector, gamma rays that are emitted instantaneously by a nuclear reaction with boron due to neutron irradiation and then enter the hole of the collimator; computational processing steps; and a display step of creating and displaying the overall gamma-ray intensity distribution in three dimensions based on the result of the calculation processing step; In the arithmetic processing step, In the case where gamma rays are detected in the detecting step, (1) When no gamma ray is detected by other detectors in the surrounding area, a wave height distribution is generated based on the detected gamma ray. (2) When gamma rays are detected by other detectors in the surrounding area at the same time, (2-a) When the total number of gamma rays detected is 3 or more, all signals are discarded and no wave height distribution is performed, that is, non-simultaneous counting is performed. (2-b) When the total number of detected gamma rays is 2, (2-b-a) When the sum of the two wave heights is within a given peak range, the two signals are discarded and the photoelectric peak count is increased by 1, i.e., simultaneous counting is performed. (2-b) If the sum of the two wave heights does not fall within a given peak range, the two signals are discarded, i.e., non-simultaneous counting is performed.

11. The measuring method according to claim 10, characterized in that: When the measurement device according to claim 2 is used to perform the simultaneous counting process in the calculation step, The order in which the gamma rays enter the detectors is determined, and coincidence counting is performed only on the gamma rays determined to have entered the detectors first.

12. The measuring method according to claim 10 or 11, characterized in that: According to the measuring device of claim 3, when the gamma rays detected by the transmission gamma ray detection detector provided on the rear side of the detector are detected simultaneously by the transmission gamma ray detection detector and one of the detectors, (1) When the sum of the wave heights of two detected gamma rays is within a predetermined peak range of the wave height distribution, the two detected signals are discarded, the detection is deemed to be by the detector, and the photoelectric peak count is incremented by 1, i.e., simultaneous counting is performed. (2) When the sum of the two wave heights is not within a given peak range, the two detected signals are discarded, i.e., non-simultaneous counting is performed.

13. The measuring method according to claim 10, characterized in that: As the neutron irradiation source, an accelerator BNCT was used.

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