Graduate School of Engineering, Kyoto University, Kyoto, Japan.
Institute for Integrated Radiation and Nuclear Science, Kyoto University, Osaka, Japan.
Appl Radiat Isot. 2020 Sep;163:109214. doi: 10.1016/j.apradiso.2020.109214. Epub 2020 May 19.
To develop boron neutron capture therapy (BNCT), it is desired to measure B concentration and obtain a two-dimensional B distribution in animal studies. In this research, we develop a prompt gamma-ray imaging detector to measure B distribution using a 50 mm × 50 mm x 10 mm LaBr(Ce) scintillator and a multi-pixel photon counter (MPPC). To measure a two-dimensional B distribution, the 478 keV gamma-ray emitted from B(n,α)Li 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治疗（BNCT），在动物研究中，期望测量硼浓度并获得二维硼分布。在这项研究中，我们开发了一种瞬发伽马射线成像探测器，使用 50mm×50mm×10mm LaBr(Ce)闪烁体和多像素光子计数器（MPPC）来测量硼分布。为了测量二维硼分布，应该测量来自 B(n,α)Li 反应的 478keV 伽马射线，并在每个 MPPC 中从 511keV 背景伽马射线中进行区分。此外，作为探测器的一个特征，有必要研究 478keV 事件是否可以在两个维度上单独入射到 MPPC 上。在这项研究中，我们评估了能量分辨率，并使用热中子束和硼样品的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 511keV 的全宽半最大值为 5.0±0.2%的能量分辨率，优于区分 478 和 511keV 伽马射线所需的 6.5%能量分辨率。当使用 6.25ppm 样品的 478keV 伽马射线峰的高斯分布在第一 ROI 中从-3σ 设置到-σ（第一 ROI）和在第二 ROI 中从-3σ 设置到中位数时，探测器对 478keV 伽马射线的计数率分别为 0.03 和 0.11 cps，没有准直器。此外，在第一 ROI 中，511keV 伽马射线峰重叠的影响约为 2.0%，在第二 ROI 中约为 3.2%。此外，478keV 伽马射线的计数以二维形式可视化。
