Scintillator evaluation method

Abstract

To provide a scintillator evaluation method capable of evaluating the time response of a scintillator with high accuracy in a short time.SOLUTION: A scintillator evaluation method includes steps S1 to S5. In step S2, a waveform f(t) of an electric signal output from a photodetector that has received scintillation light generated by a scintillator, is acquired. In step S3, computation is performed to deconvolve the electric signal waveform f(t) with an impulse response function i(t) of the photodetector. In step S4, a result of the computation in step S3 is fitted with a model function represented by the convolution of a time response function s(t) of the scintillator, including information on both rising and falling the generation of scintillation light due to interactions with radiation, and a function p(t) representing single photon time resolution of the photodetector. In step S5, the time response of the scintillator is evaluated on the basis of a fitting result.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a method for evaluating the time response of a scintillator. [Background technology]

[0002] A scintillator generates scintillation light by interacting with high-energy radiation (e.g., gamma rays, X-rays, alpha rays, etc.), and may generate Cherenkov light in addition to scintillation light. A scintillator is used together with a photodetector that receives the scintillation light (and Cherenkov light). Photodetectors used here include, for example, photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs). PMTs and SiPMs are capable of photon counting measurements, and also allow analog measurements.

[0003] SiPMs capable of photon counting measurements (digital SiPMs) can obtain information on all detected scintillation photons, making it possible to detect the time when radiation interacts with the scintillator with a time resolution that is increased to the theoretical limit. Digital SiPMs can obtain information on Cherenkov photons, which are believed to be the first to be generated when radiation interacts with the scintillator. In addition, by adding up the output signals from the digital SiPMs, it is possible to evaluate the characteristics of the scintillator and also to evaluate the single photon time resolution (SPTR) of the SiPM with high precision.

[0004] On the other hand, compared to digital SiPMs, SiPMs capable of analog measurement (analog SiPMs) are still in use because they have higher photon detection efficiency, are easier to manufacture, have easier output signal processing, and are easier to handle.

[0005] Radiation detectors including scintillators and photodetectors can be used in a variety of devices that detect radiation, as well as radiation tomography devices such as Positron Emission Tomography (PET) devices and Single Photon Emission Computed Tomography (SPECT) devices.

[0006] Scintillators made of various materials are known, and new materials are also being developed. One of the important evaluation items for the properties of scintillators is the time response of scintillation light generation due to interaction with radiation. In addition, the Time-Correlated Single Photon Counting (TCSPC) method and the averaging method (Non-Patent Documents 1, 2) are known as methods for evaluating the time response of scintillators.

[0007] In the TCSPC method, when one of a pair of gamma-ray photons generated by an RI source traveling in opposite directions is incident on a scintillator to be evaluated, the scintillation light generated by the scintillator is detected by a photodetector and a signal pulse is output from the photodetector, and the other photon is detected by a reference radiation detector and a synchronization pulse is output from the radiation detector. The time difference between the signal pulse and the synchronization pulse is obtained for each of the many photon pairs generated by the RI source, and the time response of the scintillator to be evaluated is evaluated based on a histogram of these time differences.

[0008] In the averaging method, when gamma-ray photons generated by an RI source are incident on a scintillator to be evaluated, the scintillation light generated by the scintillator is detected by a photodetector, and the waveform of the electrical signal output from the photodetector is obtained. The signal waveforms obtained for each of the many photons generated by the RI source are averaged, and the time response of the scintillator to be evaluated is evaluated based on the averaged waveform. [Prior art documents]

Non-licensed literature

[0009]

Non-licensed literature 1

Non-licensed Document 4

Non-licensed Document 5

[0010] Although the TCSPC method can evaluate the time response of the scintillator with high accuracy, it takes a long time (e.g., more than 10 days or about one month) to obtain a histogram of the time difference between the signal pulse and the synchronization pulse. The average method can obtain an average waveform for a large number of photons incident on the scintillator in a relatively short time (e.g., less than 30 minutes), but the evaluation precision is low because the information includes the time response of the photodetector.

[0011] The present invention has been made to solve the above problems, and has an object to provide a scintillator evaluation method that can evaluate the time response of a scintillator with high accuracy in a short period of time. [Means for solving the problem]

[0012] The scintillator evaluation method of the present invention is a method for evaluating the time response of a scintillator that generates scintillation light by interacting with radiation.

[0013] A first aspect of the scintillator evaluation method of the present invention includes: (1) a signal waveform acquisition step of acquiring the waveform of an electrical signal output from a photodetector that receives scintillation light generated by the scintillator; (2) a deconvolution calculation step of deconvoluting the impulse response function of the photodetector with the electrical signal waveform; (3) a fitting step of fitting a result of the deconvolution calculation step with a model function that indicates a probability density distribution of scintillation light components represented by a convolution of a time response function of the scintillator that includes information on both the rise and fall of scintillation light generation due to interaction with radiation and a function that represents the single-photon time resolution of the photodetector; and (4) an evaluation step of evaluating the time response of the scintillator based on the fitting result of the fitting step.

[0014] In a second aspect of the scintillator evaluation method of the present invention, in addition to the first aspect, in the signal waveform acquisition step, the waveform of the electrical signal is acquired multiple times, and in the deconvolution calculation step, a deconvolution calculation is performed on each of the waveforms of the multiple electrical signals, and in the fitting step, fitting is performed on the sum or average of the results of the deconvolution calculation on each of the waveforms of the multiple electrical signals in the deconvolution calculation step.

[0015] In a third aspect of the scintillator evaluation method of the present invention, in addition to the first aspect, in the signal waveform acquisition step, the waveform of the electrical signal is acquired multiple times, and in the deconvolution calculation step, a deconvolution calculation is performed on the sum or average of the waveforms of the multiple electrical signals.

[0016] In a fourth aspect of the scintillator evaluation method of the present invention, in addition to any one of the first to third aspects, in the fitting step, the calculation result from the deconvolution calculation step is fitted with a model function represented by the sum of the probability density distribution of the scintillation light component and the probability density distribution of the Cherenkov light component.

[0017] A fifth aspect of the scintillator evaluation method of the present invention is similar to any one of the first to fourth aspects, and further comprises using a photomultiplier tube as the photodetector in the signal waveform acquiring step.

[0018] In a sixth aspect of the scintillator evaluation method of the present invention, in addition to any one of the first to fourth aspects, a silicon photomultiplier is used as the photodetector in the signal waveform acquiring step. Effect of the Invention

[0019] According to the present invention, the time response of a scintillator can be evaluated with high accuracy in a short time. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing a measurement system for acquiring the impulse response function i(t) of a photodetector. [Diagram 2] FIG. 2 is a diagram showing a measurement system for acquiring the waveform f(t) of an electrical signal output from a photodetector that receives scintillation light generated by a scintillator under evaluation. [Diagram 3] FIG. 3 is a diagram showing an example of a waveform f(t) of an electrical signal output from a photodetector. [Figure 4] FIG. 4 is a diagram showing an example of the time response function s(t) of the scintillator. [Diagram 5] FIG. 5 is a diagram showing an example of a function p(t) representing the single-photon time resolution of a photodetector. [Figure 6] FIG. 6 is a diagram showing an example of the impulse response function i(t) of the photodetector. [Figure 7] FIG. 7 is a diagram showing an example of the result of the deconvolution operation of i(t) with respect to f(t). [Figure 8] FIG. 8 is a flowchart of the scintillator evaluation method of this embodiment. [Figure 9] FIG. 9 is a diagram showing the results obtained by evaluating the time response of the BGO in the example. [Figure 10]FIG. 10 is an enlarged view of a portion of FIG. [Figure 11] FIG. 11 is a diagram showing the results of evaluating the time response of the BGO in the embodiment in comparison with the results of evaluation by the TCSPC method. [Figure 12] FIG. 12 is a diagram showing the results of evaluating the time response of the BGO in the example, in comparison with the evaluation results described in Non-Patent Document 3. [Figure 13] FIG. 13 is a diagram showing the results obtained by evaluating the time response of LYSO in the examples in comparison with the evaluation results by the TCSPC method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicated descriptions are omitted. The present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0022] The scintillator evaluation method of this embodiment evaluates the time response of a scintillator based on the waveform f(t) of an electrical signal output from a photodetector that receives scintillation light generated by the scintillator to be evaluated, and the impulse response function i(t) of the photodetector. t is a variable indicating time. First, an example of a measurement system for acquiring i(t) and f(t) will be described.

[0023] Fig. 1 is a diagram showing a measurement system for acquiring the impulse response function i(t) of a photodetector. Photodetector 12 outputs an electrical signal in response to the incidence of a photon v. The electrical signal output from photodetector 12 is input to an oscilloscope 40, and the waveform of the electrical signal is acquired. Photodetector 12 is, for example, a PMT or a SiPM. As shown in Fig. 2, photodetector 12 constitutes radiation detector 10 together with scintillator 11, which is the subject of evaluation.

[0024] In the measurement system shown in Fig. 1, the impulse response function i(t) of the photodetector 12 is obtained, for example, as follows. The voltage applied to the photodetector 12 is set as high as possible (for example, an overvoltage from the breakdown voltage to +8.0 V) so that single photons can be visually recognized by the oscilloscope 40 without an amplifier. The range is set so that the entire waveform of the single photon falls within the voltage range of the oscilloscope 40 (for example, 1 mV / div). The trigger threshold of the oscilloscope 40 is set to 0.5 photons. Then, the waveform is obtained repeatedly until statistical noise is no longer a problem, and the waveform is averaged to obtain the impulse response function i(t) of the photodetector 12.

[0025] 2 is a diagram showing a measurement system for acquiring the waveform f(t) of an electrical signal output from a photodetector that receives scintillation light generated by a scintillator under evaluation. The scintillator 11 under evaluation and photodetector 12 constitute a radiation detector 10. Furthermore, the scintillator 21 and photodetector 22 constitute a radiation detector 20. The photodetector 22 is, for example, a PMT or a SiPM.

[0026] The radiation detector 10 and the radiation detector 20 are disposed opposite to each other. An arbitrary RI radiation source (for example 22 A pair of gamma ray photons γ with energy of 511 KeV generated by annihilation of an electron and a positron in the RI source travel in opposite directions and are counted by the radiation detectors 10 and 20.

[0027] When one type of gamma ray photon γ is incident on the scintillator 11 of the radiation detector 10, scintillation light is generated in the scintillator 11. The scintillation light is received by the photodetector 12, and an electrical signal is output from the photodetector 12. The electrical signal output from the photodetector 12 is input to the oscilloscope 40 as a signal whose waveform f(t) is to be acquired.

[0028] When the other gamma ray photon γ is incident on the scintillator 21 of the radiation detector 20, scintillation light is generated in the scintillator 21. The scintillation light is received by the photodetector 22, and an electrical signal is output from the photodetector 22. The electrical signal output from the photodetector 22 is input to the oscilloscope 40 as a signal indicating the timing of coincidence counting of the photon pair.

[0029] In addition, the electrical signal output from the photodetector 22 is also input to a CFD (Constant Fraction Discriminator) circuit 30. An energy discrimination signal indicating whether or not the photon incident on the scintillator 21 of the radiation detector 20 is a gamma ray photon with energy of 511 KeV is output from the CFD circuit 30, and this energy discrimination signal is also input to the oscilloscope 40.

[0030] In the oscilloscope 40, when the energy discrimination signal indicates that the photon incident on the scintillator 21 of the radiation detector 20 is a gamma ray photon with energy of 511 KeV, the waveform f(t) of the electrical signal output from the photodetector 12 is acquired using the time indicated by the timing signal output from the photodetector 22 as the reference time.

[0031] In the measurement system shown in FIG. 2, the waveform f(t) of the electrical signal output from the photodetector 12 is obtained, for example, as follows: The amount of light is reduced to an extent that the saturation effect of the photodetector 12 is not visible, or the detection efficiency is reduced by reducing the applied voltage to the photodetector 12. i(t) is scaled according to the applied voltage. The applied voltage is reduced to an extent that the crosstalk probability of the photodetector 12 is sufficiently negligible. When the oscilloscope 40 is operated in coincidence counting mode, the timing signal output from the photodetector 22 is delayed from the signal from the photodetector 12 so that the trigger time of the photodetector 12 does not depend on the rise time. The voltage range of the oscilloscope 40 is increased so that the entire waveform of the electrical signal output from the photodetector 12 can be seen.

[0032] In radiation detector 10 including scintillator 11 and photodetector 12 to be evaluated, the time response function of scintillator 11 is s(t), a function representing the single-photon time resolution of photodetector 12 is p(t), and the impulse response function of photodetector 12 is i(t). The waveform f(t) of the electrical signal output from photodetector 12 is expressed by the convolution of s(t), p(t), and i(t), as shown in the following equation (1).

[0033]

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[0034] Fig. 3 shows an example of the waveform f(t) of an electrical signal output from a photodetector. Since f(t) is expressed by the convolution of s(t), p(t), and i(t), it is difficult to obtain information on s(t), p(t), and i(t) from f(t) alone. f(t) can be obtained by the measurement system described using Fig. 2.

[0035] FIG. 4 is a diagram showing an example of the time response function s(t) of a scintillator. s(t) includes information on both the rise r and fall d of the scintillation light generated by the interaction with radiation. The rise r and fall d differ depending on the material of the scintillator. The rise r is often 1 ns or less. The fall d is 1 ns or less for BGO (Bi4Ge3O 12 ) is about 300 ns, and LYSO(Lu 2-x Y x In the case of SiO5, it is about 30 to 40 ns. s(t) can generally be expressed as a weighted sum of multiple basic equations (equation (2) below). t0 is the time when radiation interacts with the scintillator.

[0036]

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[0037] FIG. 5 shows an example of a function p(t) that represents the single-photon time resolution of a photodetector. p(t) can be approximately represented by a Gaussian function. The single-photon time resolution (SPTR) is given by the full width at half maximum of this function. The SPTR is about 100 to 300 ps, ​​which is short compared to the response of s(t).

[0038] FIG. 6 shows an example of the impulse response function i(t) of a photodetector. i(t) can be expressed as the sum of two types of exponential functions. i(t) can be obtained using the measurement system described with reference to FIG. 1. i(t) is a function specific to the photodetector, does not change for each interaction event of radiation in the scintillator, and can be easily measured. Compared to SiPM, the current fluctuation of i(t) is large in PMT.

[0039] By performing a deconvolution operation of i(t) with respect to f(t), the convolution of s(t) and p(t) is obtained, as shown in the following equation (3). The convolution of s(t) and p(t) is expressed by the model function shown in the following equation (4). This model function indicates the probability density distribution of the scintillation light components generated in the scintillator and detected by the photodetector. In this equation, σ corresponds to the SPTR of the photodetector. ρ i are the weighting coefficients when s(t) is expressed as a weighted sum of multiple basic equations (above equation (2)). A is a coefficient.

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[0042] In addition, when the light generated by the scintillator contains a Cherenkov light component in addition to the scintillation light component, the result obtained by deconvoluting i(t) with f(t) can be expressed by the model function F(t) shown in the following equation (5). This model function F(t) is the probability density distribution F of the scintillation light component generated by the scintillator. s (t) and the probability density distribution F of the Cherenkov light component generated by the scintillator. c (t) and the probability density distribution F s (t) is expressed by the following equation (6). The probability density distribution F of the Cherenkov light component c (t) is expressed by the following equation (7) (see Non-Patent Document 5). In equation (7), erfc is a complementary error function expressed by the following equation (8). ρ3 is a coefficient indicating the proportion of the Cherenkov light component. λ is a parameter representing the interaction depth fluctuation of the photodetector. μ is a parameter representing the expected value of the emission time of Cherenkov light. Δ is a parameter representing the time fluctuation of the photodetector.

[0043]

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[0047] FIG. 7 is a diagram showing an example of the result of the deconvolution of i(t) with respect to f(t). The result of the deconvolution based on f(t) and i(t) obtained by measurement is expressed by the model function of the above formula (4). Therefore, by fitting the result of this deconvolution with the model function of the above formula (4), each parameter (ρ i , r i , d i , σ) can be obtained.

[0048] 8 is a flowchart of the scintillator evaluation method of this embodiment. The scintillator evaluation method of this embodiment is a method for evaluating the time response of a scintillator that generates scintillation light by interacting with radiation, and includes an impulse response function acquisition step S1, a signal waveform acquisition step S2, a deconvolution calculation step S3, a fitting step S4, and an evaluation step S5.

[0049] In the impulse response function acquisition step S1, the impulse response function i(t) of the photodetector is acquired. If the impulse response function i(t) of the photodetector is known, the impulse response function acquisition step S1 does not need to be performed. In the signal waveform acquisition step S2, the waveform f(t) of the electrical signal output from the photodetector that receives the scintillation light generated by the scintillator is acquired.

[0050] In the deconvolution step S3, the impulse response function i(t) of the photodetector is deconvoluted with respect to the electrical signal waveform f(t). This results in the convolution of s(t) and p(t). In the fitting step S4, the result of the deconvolution step S3 is fitted with the model function of the above formula (4).

[0051] In the evaluation step S5, the time response (rising r, falling d) of the scintillator is evaluated based on the fitting result in the fitting step S4. Also, the SPTR(σ) of the photodetector can be evaluated.

[0052] In the signal waveform acquisition step S2, the electric signal waveform f(t) may be acquired multiple times (for example, several hundred times to 1000 times). In this case, in the deconvolution calculation step S3, the impulse response function i(t) is deconvoluted for each of the multiple electric signal waveforms f(t), and in the fitting step S4, fitting is performed for the sum or average of the results of the deconvolution calculation for each of the multiple electric signal waveforms f(t) in the deconvolution calculation step S3 (hereinafter referred to as "evaluation flow 1"). Alternatively, in the deconvolution calculation step S3, the impulse response function i(t) is deconvoluted for the sum or average of the multiple electric signal waveforms f(t) (hereinafter referred to as "evaluation flow 2"). In this way, the time response of the scintillator can be evaluated with higher accuracy.

[0053] Next, the advantages of the scintillator evaluation method of this embodiment compared to conventional methods will be described. In the TCSPC method, the time difference between the signal pulse and the synchronization pulse is obtained for each of a large number of photon pairs generated by an RI source, and the time response of the scintillator to be evaluated is evaluated based on a histogram of these time differences, so the evaluation takes a long time. In contrast, the scintillator evaluation method of this embodiment evaluates the time response of the scintillator based on the waveform of an electrical signal output from a photodetector that receives scintillation light generated by the scintillator to be evaluated. In this respect, the scintillator evaluation method of this embodiment is similar to the averaging method, and can evaluate the time response of the scintillator in a short time.

[0054] In both the scintillator evaluation method and the averaging method of this embodiment, the time response of the scintillator is evaluated based on the waveform of the electrical signal output from the photodetector that receives the scintillation light generated by the scintillator to be evaluated. However, in the averaging method, the contribution of the impulse response function i(t) of the photodetector and the function p(t) representing the single photon time resolution of the photodetector is not taken into consideration in the waveform f(t) of the electrical signal output from the photodetector. In addition, in the averaging method, the falling edge d is taken into consideration in the time response function s(t) of the scintillator, but the rising edge r is not taken into consideration. Therefore, the accuracy of the falling edge d obtained by the averaging method is poor. In contrast, in the scintillator evaluation method of this embodiment, a fitting process is performed assuming that the waveform f(t) of the electrical signal output from the photodetector is expressed by the model function of the above formula (4), so that the time response (rising edge r, falling edge d) of the scintillator can be evaluated with high accuracy.

[0055] In the method described in Non-Patent Document 4, the impulse response function i(t) of the photodetector is taken into consideration, but the function p(t) representing the single-photon time resolution of the photodetector is not taken into consideration. Also, in the time response function s(t) of the scintillator, the falling edge d is taken into consideration, but the rising edge r is not taken into consideration. Therefore, the accuracy of the method described in Non-Patent Document 4 is poor.

[0056] Next, an example will be described. In this example, in the measurement system shown in FIG. 2, a scintillator 11 having a size of 3×3×15 mm was used as the evaluation target. 3 BGO or size 3×3×10mm 3 A SiPM (S13360-3050 manufactured by Hamamatsu Photonics K.K.) was used as the photodetector 12 for detecting the scintillation light generated by the scintillator 11 to be evaluated. 3LYSO was used, and a SiPM (S13360-3075 manufactured by Hamamatsu Photonics K.K.) was used as the photodetector 22. The time response of the scintillator to be evaluated was evaluated by evaluation flow 2 (number of times the electric signal waveform f(t) was acquired in the signal waveform acquisition step S2=1000).

[0057] Figures 9 and 10 are diagrams showing the results obtained by evaluating the time response of the BGO in the embodiment. Figure 10 shows an enlarged view of the area enclosed by the dashed rectangle in Figure 9. Figures 9 and 10 show the results of the deconvolution of i(t) with f(t) and the fitting results using the model function (Equation (5) above). Figure 10 also shows the probability density distributions of the Cherenkov light component and the scintillation light component in the fitting results. The probability density distributions of the Cherenkov light component and the scintillation light component were obtained by fitting the results of the deconvolution of i(t) with f(t) using the model function F(t) in Equation (5) above.

[0058] The results obtained in this example are as follows. The time response of the BGO was d1 = 339ns, d2 = 24.7ns, and the rise time was r1 = r2 = 0.050ns. The SPTR of the SiPM was 0.498ns. In addition, the ratio of Cherenkov light components to scintillation light components of the light incident on the SiPM (ρ3 / (ρ1 + ρ2)) was 0.53%.

[0059] FIG. 11 is a diagram showing the results of evaluating the time response of the BGO in the embodiment in comparison with the evaluation results by the TCSPC method. This diagram shows the fitting results of the fitting step S4 in the embodiment for the BGO to be evaluated, and the distribution of the time difference between the signal pulse and the synchronization pulse obtained for each of a large number of photon pairs in the TCSPC method. As shown in this diagram, the scintillator evaluation method of this embodiment can accurately reproduce the evaluation results by the TCSPC method. In addition, the time required for the evaluation of the BGO by this embodiment was 15.9 minutes, which was significantly shorter than the 27.4 days required for the evaluation by the TCSPC method.

[0060] 12 is a diagram showing the results of evaluating the time response of BGO in the embodiment in comparison with the evaluation results described in Non-Patent Document 3. In this figure, the evaluation results described in Non-Patent Document 3 are shown in a histogram, and the fitting results in fitting step S4 in the embodiment are shown in a solid line superimposed thereon. Non-Patent Document 3 describes that when radiation interacts with a scintillator, the photon detected by the photodetector first has the highest probability of being Cherenkov light. As shown in this figure, the scintillator evaluation results of this embodiment are in good agreement with the evaluation results described in Non-Patent Document 3, and the peak surrounded by a dashed ellipse in the figure is considered to indicate Cherenkov light detection.

[0061] FIG. 13 is a diagram showing the results obtained by evaluating the time response of LYSO in the embodiment in comparison with the evaluation results by the TCSPC method. This diagram shows the fitting results by the fitting step S4 in the embodiment for the LYSO to be evaluated, and the distribution of the time difference between the signal pulse and the synchronization pulse obtained for each of a large number of photon pairs in the TCSPC method. As shown in this diagram, the scintillator evaluation method of this embodiment can accurately reproduce the evaluation results by the TCSPC method even for a relatively fast scintillator such as LYSO. In addition, the time required for the evaluation of LYSO by this embodiment was 14.7 minutes, which was significantly shorter than the 9.7 days required for the evaluation by the TCSPC method. [Explanation of symbols]

[0062] 10...radiation detector, 11...scintillator, 12...photodetector, 20...radiation detector, 21...scintillator, 22...photodetector, 30...CFD circuit, 40...oscilloscope.

Claims

1. 1. A method for evaluating the time response of a scintillator that generates scintillation light by interacting with radiation, comprising: a signal waveform acquiring step of acquiring a waveform of an electrical signal output from a photodetector that receives scintillation light generated by the scintillator; a deconvolution step of deconvoluting an impulse response function of the photodetector with respect to a waveform of the electrical signal; a fitting step of fitting a calculation result from the deconvolution calculation step with a model function indicating a probability density distribution of scintillation light components expressed by a convolution of a time response function of the scintillator including information on both the rising and falling edges of scintillation light generated by an interaction with radiation and a function indicating a single-photon time resolution of the photodetector; an evaluation step of evaluating a time response of the scintillator based on a fitting result from the fitting step; A scintillator evaluation method comprising:

2. In the signal waveform acquisition step, the waveform of the electrical signal is acquired a plurality of times; In the deconvolution step, a deconvolution operation is performed on each of the waveforms of the plurality of electrical signals; In the fitting step, fitting is performed on a sum or an average of results of the deconvolution operation performed on each of the waveforms of the plurality of electrical signals in the deconvolution operation step. The scintillator evaluation method according to claim 1 .

3. In the signal waveform acquisition step, the waveform of the electrical signal is acquired a plurality of times; In the deconvolution step, a deconvolution operation is performed on a sum or an average of waveforms of the plurality of electrical signals. The scintillator evaluation method according to claim 1 .

4. in the fitting step, fitting a calculation result from the deconvolution calculation step with a model function represented by a sum of a probability density distribution of a scintillation light component and a probability density distribution of a Cherenkov light component; The scintillator evaluation method according to claim 1 .

5. a photomultiplier tube is used as the photodetector in the signal waveform acquiring step; The scintillator evaluation method according to claim 1 .

6. a silicon photomultiplier is used as the photodetector in the signal waveform acquisition step; The scintillator evaluation method according to claim 1 .

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