Hamby D M, Palmer T S
Nuclear Engineering and Radiation Health Physics, Oregon State University, Corvallis 97331-5902, USA.
Health Phys. 2001 Oct;81(4):426-37. doi: 10.1097/00004032-200110000-00007.
Internal dosimetry models that currently drive regulatory compliance decisions assume that tritium retention kinetic behavior can be modeled by a single exponential function. This is contrary to the results of a number of modeling techniques, which indicate that while elemental tritium (HT) and tritiated water (HTO) are the most commonly released forms of tritium, organically-bound tritium (OBT) doses can be quite significant. In this paper, a unified two-compartment model of the retention kinetics of HTO and OBT is examined for the purpose of investigating the importance of metabolic routes not considered in the ICRP one- and two-exponent models; namely the transfer of tritium from the HTO compartment to the OBT compartment and vice versa. In particular, the effect of intake ratio is investigated, and a detailed analysis of dosimetric implications is performed. For typical combined intakes of HTO and OBT, the number of disintegrations from the two tritium forms can be roughly equal. This result, when combined with the suggested greater biological effectiveness of OBT, indicates effective doses will be greater than those obtained from a single exponential model. The results of this study corroborate previous findings using the two-compartment model for the cases of HTO-only and or OBT-only intakes and compare well with data taken from studies on animals and human subjects.
当前用于驱动监管合规决策的内照射剂量学模型假定，氚的滞留动力学行为可用单一指数函数来模拟。这与许多建模技术的结果相悖，这些结果表明，虽然元素氚（HT）和氚化水（HTO）是最常见的氚释放形式，但有机结合氚（OBT）的剂量可能相当可观。本文研究了一个统一的两室模型，用于描述HTO和OBT的滞留动力学，目的是研究国际辐射防护委员会（ICRP）单指数和双指数模型中未考虑的代谢途径的重要性；即氚在HTO室和OBT室之间的转移，反之亦然。特别地，研究了摄入比的影响，并对剂量学意义进行了详细分析。对于HTO和OBT的典型联合摄入量，两种氚形式的衰变次数大致相等。这一结果，再加上OBT具有更高生物有效性的观点，表明有效剂量将大于单指数模型得出的剂量。本研究结果证实了先前使用两室模型对仅摄入HTO和仅摄入OBT情况的研究结果，并且与来自动物和人类受试者研究的数据比较吻合。
