Struelens Lara, Huet Christelle, Broggio David, Dabin Jérémie, Desorgher Laurent, Giussani Augusto, Li Wei Bo, Nosske Dietmar, Lee Yi-Kang, Cunha Lidia, Carapinha Maria J R, Medvedec Mario, Covens Peter
Belgian Nuclear Research Center (SCK CEN), Nuclear Medical Applications, Boeretang 200, 2400, Mol, Belgium.
Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-SANTE/SDOS, 31 Avenue de La Division Leclerc, 92260, Fontenay-Aux-Roses, France.
EJNMMI Phys. 2024 Apr 22;11(1):38. doi: 10.1186/s40658-024-00638-y.
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 Tc-HDP/MDP, FDG and NaI. 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.
为确保对诸如工作人员、护理人员以及接近核医学（NM）患者的普通公众等关键人群提供充分的辐射防护，有必要考虑患者在住院期间或出院后所发射辐射的影响。当前的风险评估基于在距患者特定距离处的单个位置进行的环境剂量率测量，并在给予放射性药物后的多个时间点进行，以估计全身滞留情况。本研究通过开发和验证一种更先进的计算剂量学方法来解决这种方法的局限性，该方法使用蒙特卡罗（MC）模拟，并结合灵活且逼真的计算体模以及来自参考生物动力学模型的时间活度分布曲线。
对于使用锝 - 亚甲基二膦酸盐（Tc - HDP/MDP）、氟代脱氧葡萄糖（FDG）和碘化钠（NaI）的典型临床程序，已成功将距NM患者1米处的环境剂量率当量Ḣ(10)测量值与使用国际辐射防护委员会（ICRP）成人参考计算体素体模的5种不同代码的MC模拟结果进行比较。所有测量数据均落在为平均模拟结果确定的95%置信区间内。此外，针对更现实的场景比较了不同的MC代码（MCNP - X、PHITS、GATE、GEANT4、TRIPOLI - 4®），在该场景中，在距离患者模型前方和侧面30厘米、50厘米和100厘米处确定受照个体的有效剂量率Ė。对于所有放射性药物，在1米处代码之间的差异低于8%，在30厘米和50厘米处面对面和并排配置时差异在5%至16%之间。对患者模型形态影响的敏感性研究表明，对于给药后长达120分钟的时间点，在所纳入患者模型范围内，1米处Ḣ(10)的相对标准偏差保持在16%以下。
经过验证的计算方法将进一步用于评估各种近距离接触配置和一系列放射性药物每单位给药活度的有效剂量率，作为风险评估研究的一部分。连同选择适当的剂量约束，这将有助于制定释放标准和患者限制措施。
