To develop boron neutron capture therapy (BNCT), it is desired to measure ¹⁰B concentration and obtain a two-dimensional ¹⁰B distribution in animal studies. In this research, we develop a prompt gamma-ray imaging detector to measure ¹⁰B distribution using a 50 mm × 50 mm x 10 mm LaBr₃(Ce) scintillator and a multi-pixel photon counter (MPPC). To measure a two-dimensional ¹⁰B distribution, the 478 keV gamma-ray emitted from ¹⁰B(n,α)⁷Li reaction should be measured with the discrimination from 511 keV background gamma rays in each MPPC. Furthermore, as a characteristic of the detector, it is necessary to investigate whether the 478 keV events individually incident on the MPPC can be measured in two dimensions. In this study, we evaluated the energy resolution and performed a two-dimensional distribution measurement using a thermal neutron beam and prompt gamma rays from a boron sample.

This system was able to obtain energy resolution as full width at half maximum at 511 keV of 5.0 ± 0.2% in all MPPC pixels, better than the 6.5% energy resolution required to discriminate between 478 and 511 keV gamma rays.

When the region of interest (ROI) was set up from -3σ to – σ (first ROI) and -3σ to the median (second ROI) for the Gaussian distribution of a 478 keV gamma-ray peak using a 6.25 ppm sample, the detector count rate of the 478 keV gamma rays was 0.03 and 0.11 cps, respectively, without a collimator. Moreover, the effect due to the overlapping 511 keV gamma ray peak was approximately 2.0% in the first ROI and approximately 3.2% in the second ROI. In addition, the counts of 478 keV gamma rays were visualized in two-dimensional.

为了开发硼中子俘获疗法 (BNCT)，需要在动物研究中测量¹⁰ B 浓度并获得二维¹⁰ B 分布。在这项研究中，我们开发了一种快速伽马射线成像探测器，使用 50 mm × 50 mm x 10 mm LaBr ₃ (Ce) 闪烁体和多像素光子计数器 (MPPC)来测量¹⁰ B 分布。为了测量二维¹⁰ B 分布，从¹⁰ B(n,α) ⁷发射的 478 keV 伽马射线锂反应的测量应区分每个 MPPC 中的 511 keV 背景伽马射线。此外，作为探测器的一个特性，有必要研究是否可以在两个维度上测量单独入射到 MPPC 上的 478 keV 事件。在这项研究中，我们评估了能量分辨率，并使用来自硼样品的热中子束和瞬发伽马射线进行了二维分布测量。

该系统能够在所有 MPPC 像素中获得 511 keV 的 5.0 ± 0.2% 的半高全宽能量分辨率，优于区分 478 和 511 keV 伽马射线所需的 6.5% 能量分辨率。

当使用 6.25 ppm 样本的 478 keV 伽马射线峰值的高斯分布将感兴趣区域 (ROI) 从 -3σ 设置为 – σ（第一个 ROI）和 -3σ 到中值（第二个 ROI）时，在没有准直器的情况下，478 keV 伽马射线的探测器计数率分别为 0.03 和 0.11 cps。此外，由于重叠的 511 keV 伽马射线峰造成的影响在第一个 ROI 中约为 2.0%，在第二个 ROI 中约为 3.2%。此外，478 keV 伽马射线的计数在二维中可视化。