In order to ensure adequate radiation protection of critical groups such as staff, caregivers and the general public coming into proximity of nuclear medicine (NM) patients, it is necessary to consider the impact of the radiation emitted by the patients during their stay at the hospital or after leaving the hospital. Current risk assessments are based on ambient dose rate measurements in a single position at a specified distance from the patient and carried out at several time points after administration of the radiopharmaceutical to estimate the whole-body retention. The limitations of such an approach are addressed in this study by developing and validating a more advanced computational dosimetry approach using Monte Carlo (MC) simulations in combination with flexible and realistic computational phantoms and time activity distribution curves from reference biokinetic models. Measurements of the ambient dose rate equivalent Ḣ*(10) at 1 m from the NM patient have been successfully compared against MC simulations with 5 different codes using the ICRP adult reference computational voxel phantoms, for typical clinical procedures with 99mTc-HDP/MDP, 18FDG and Na131I. All measurement data fall in the 95% confidence intervals, determined for the average simulated results. Moreover, the different MC codes (MCNP-X, PHITS, GATE, GEANT4, TRIPOLI-4®) have been compared for a more realistic scenario where the effective dose rate Ė of an exposed individual was determined in positions facing and aside the patient model at 30 cm, 50 cm and 100 cm. The variation between codes was lower than 8% for all the radiopharmaceuticals at 1 m, and varied from 5 to 16% for the face-to face and side-by-side configuration at 30 cm and 50 cm. A sensitivity study on the influence of patient model morphology demonstrated that the relative standard deviation of Ḣ*(10) at 1 m for the range of included patient models remained under 16% for time points up to 120 min post administration. The validated computational approach will be further used for the evaluation of effective dose rates per unit administered activity for a variety of close-contact configurations and a range of radiopharmaceuticals as part of risk assessment studies. Together with the choice of appropriate dose constraints this would facilitate the setting of release criteria and patient restrictions.

中文翻译：

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EURADOS-EANM 联合倡议，建立先进的计算框架，用于评估核医学患者的外部剂量率

为了确保对接近核医学（NM）患者的工作人员、护理人员和公众等关键群体提供充分的辐射防护，有必要考虑患者在医院期间发出的辐射的影响或出院后。目前的风险评估基于在距患者指定距离的单个位置处进行的环境剂量率测量，并在施用放射性药物后的几个时间点进行，以估计全身保留。本研究通过使用蒙特卡罗（MC）模拟结合灵活且现实的计算模型和来自参考生物动力学模型的时间活动分布曲线来开发和验证更先进的计算剂量测定方法，解决了这种方法的局限性。对于使用 99mTc-HDP/MDP 的典型临床程序，使用 ICRP 成人参考计算体素模型，成功地将距离 NM 患者 1 m 处的环境剂量率当量 Ḣ*(10) 测量值与 5 种不同代码的 MC 模拟进行了成功比较。 18FDG 和 Na131I。所有测量数据均落在 95% 置信区间内，该区间是根据平均模拟结果确定的。此外，还对不同的 MC 代码（MCNP-X、PHITS、GATE、GEANT4、TRIPOLI-4®）进行了比较，以实现更真实的场景，其中暴露个体的有效剂量率 Ė 在面向患者模型和侧面的位置确定30 厘米、50 厘米和 100 厘米。对于所有放射性药物，在 1 m 处，代码之间的差异均低于 8%；对于面对面和并排配置，在 30 cm 和 50 cm 处，代码之间的差异为 5% 至 16%。关于患者模型形态影响的敏感性研究表明，对于所包含的患者模型范围，在 1 m 处的 Ḣ*(10) 相对标准偏差在给药后 120 分钟以内的时间点仍保持在 16% 以下。作为风险评估研究的一部分，经过验证的计算方法将进一步用于评估各种密切接触配置和一系列放射性药物的每单位管理活动的有效剂量率。与适当剂量限制的选择一起，这将有助于制定放行标准和患者限制。