Abstract The establishment of an in vivo internal monitoring programme requires the use of phantoms to represent an activity distribution of an incorporated radionuclide within the body. The aim of this study was to quantify the impact of the phantom geometry on the minimum detectable activity (MDA) of an incorporated radionuclide. The MDA was assessed for two instruments: a conventional radiation protection instrument and a portable gamma-spectrometer. Four phantoms were considered: two physical phantoms, a simplified torso phantom and a commercial whole body phantom, as well as two numerical phantoms, the reference adult male and female voxel phantoms published by the International Commission on Radiological Protection (ICRP). The phantoms were loaded with activity at the level of the thorax and abdomen using reference sources of 57Co, 133Ba, 137Cs, 60Co and 152Eu. The MDA for both instruments was experimentally assessed using the two physical phantoms. The experimental setup was modelled in GEANT4 and the simulated instrument responses were validated by the experimental data. The Monte Carlo model was then used to compute the instruments response and corresponding MDA when using the ICRP voxel phantoms. The simplified torso phantom provided one of the highest MDA estimates, up to a factor of 5 higher than the ones obtained with the voxel phantoms when considering a 57Co source. Depending on the considered source distribution within the phantoms, physical phantoms may lead to an underestimation of the MDA when compared to more complex and anatomically accurate numerical phantoms. This work presents a quantitative comparison between the MDA obtained with different phantoms and radionuclide distributions.

中文翻译：

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体模几何对放射性核素摄入后最小可检测活动评估的影响：从物理到数值体模

摘要 体内内部监测程序的建立需要使用体模来表示体内掺入的放射性核素的活动分布。本研究的目的是量化体模几何形状对掺入的放射性核素的最小可检测活性 (MDA) 的影响。MDA 评估了两种仪器：传统的辐射防护仪器和便携式伽马光谱仪。考虑了四个体模：两个物理体模、一个简化的躯干体模和一个商业全身体模，以及两个数字体模，即国际放射防护委员会 (ICRP) 发布的参考成年男性和女性体素体素体模。使用 57Co、133Ba、137Cs、60Co 和 152Eu。两种仪器的 MDA 都使用两个物理模型进行了实验评估。实验设置在 GEANT4 中建模，模拟仪器响应由实验数据验证。当使用 ICRP 体素体模时，然后使用蒙特卡罗模型来计算仪器响应和相应的 MDA。简化的躯干体模提供了最高的 MDA 估计值之一，在考虑 57Co 源时，比使用体素体模获得的高出 5 倍。根据体模内考虑的源分布，与更复杂和解剖学上准确的数值体模相比，物理体模可能会导致对 MDA 的低估。