Farfán Eduardo B, Huston Thomas E, Bolch W Emmett, Vernetson William G, Bolch Wesley E
Department of Nuclear and Radiological Engineering, University of Florida, Gainesville, FL 32611-8300, USA.
Health Phys. 2003 Apr;84(4):436-50. doi: 10.1097/00004032-200304000-00003.
This paper extends an examination of the influence of parameter uncertainties on regional doses to respiratory tract tissues for short-ranged alpha particles using the ICRP-66 respiratory tract model. Previous papers examined uncertainties in the deposition and clearance aspects of the model. The critical parameters examined in this study included target tissue depths, thicknesses, and masses, particularly within the thoracic or lung regions of the respiratory tract. Probability density functions were assigned for the parameters based on published data. The probabilistic computer code LUDUC (Lung Dose Uncertainty Code) was used to assess regional and total lung doses from inhaled aerosols of 239PuO2 and 238UO2/238U3O8. Dose uncertainty was noted to depend on the particle aerodynamic diameter. Additionally, dose distributions were found to follow a lognormal distribution pattern. For 239PuO2 and 238UO2/238U3O8, this study showed that the uncertainty in lung dose increases by factors of approximately 50 and approximately 70 for plutonium and uranium oxides, respectively, over the particle size range from 0.1 to 20 microm. For typical exposure scenarios involving both radionuclides, the ratio of the 95% dose fractile to the 5% dose fractile ranged from approximately 8-10 (corresponding to a geometric standard deviation, or GSD, of about 1.7-2) for particle diameters of 0.1 to 1 microm. This ratio increased to about 370 for plutonium oxide (GSD approximately 4.5) and to about 600 for uranium oxide (GSD approximately 5) as the particle diameter approached 20 microm. However, thoracic tissue doses were quite low at larger particle sizes because most of the deposition occurred in the extrathoracic airways. For 239PuO2, median doses from LUDUC were found be in general agreement with those for Reference Man (via deterministic LUDEP 2.0 calculations) in the particle range of 0.1 to 5 microm. However, median doses to the basal cell nuclei of the bronchial airways (BB(bas)) calculated by LUDUC were found to be approximately 6 times higher than LUDEP reference doses. The higher BB(bas) doses were directly attributed to discrepancies between the ICRP default thickness for the bronchial epithelium (55 microm) and the probability density function assumed within LUDUC (uniform distribution from 20 to 60 microm based upon detailed literature reviews).
本文扩展了一项研究，该研究使用国际辐射防护委员会（ICRP）第66号呼吸道模型，考察了参数不确定性对短程α粒子所致呼吸道组织区域剂量的影响。此前的论文研究了该模型在沉积和清除方面的不确定性。本研究考察的关键参数包括靶组织深度、厚度和质量，特别是呼吸道胸段或肺部区域内的这些参数。基于已发表的数据为这些参数指定了概率密度函数。使用概率计算机代码LUDUC（肺剂量不确定性代码）来评估吸入的239PuO2和238UO2/238U3O8气溶胶所致的区域肺剂量和总肺剂量。结果表明，剂量不确定性取决于颗粒的空气动力学直径。此外，发现剂量分布遵循对数正态分布模式。对于239PuO2和238UO2/238U3O8，本研究表明，在粒径从0.1到20微米的范围内，钚和铀氧化物的肺剂量不确定性分别增加约50倍和约70倍。对于涉及这两种放射性核素的典型暴露场景，对于粒径为0.1到1微米的情况，95%剂量分位数与5%剂量分位数之比约为8 - 10（对应几何标准差，或GSD，约为1.7 - 2）。当粒径接近20微米时，氧化钚的该比值增至约370（GSD约为4.5），氧化铀的该比值增至约600（GSD约为5）。然而，在较大粒径时胸段组织剂量相当低，因为大部分沉积发生在胸外气道。对于239PuO2，在粒径为0.1到5微米的范围内，发现LUDUC计算得到的中位剂量与参考人（通过确定性的LUDEP 2.0计算）的中位剂量总体一致。然而，发现LUDUC计算得到的支气管气道基底细胞核（BB(bas)）的中位剂量比LUDEP参考剂量高约6倍。较高的BB(bas)剂量直接归因于ICRP默认的支气管上皮厚度（55微米）与LUDUC中假设的概率密度函数（基于详细文献综述，为20到60微米的均匀分布）之间的差异。
