Sanders C L, Lauhala K E, McDonald K E, Sanders G A
Washington State University, Tri-Cities Laboratory, Richland 99352.
Health Phys. 1993 May;64(5):509-21. doi: 10.1097/00004032-199305000-00008.
Spatial-temporal dose-distribution patterns in the lung continually change following inhalation of radionuclides. Lung clearance, microdosimetry, and radiation dose were examined in female Wistar rats exposed to high-fired 169Yb2O3-239PuO2 aerosols. Whole-body counting for 169Yb at 14 d postexposure provided an accurate (r = 0.99) estimate of 239Pu lung content. Alpha irradiation of tracheal epithelium was at least 50 times less than for bronchiolar epithelium due principally to preferential retention of 239PuO2 in peribronchiolar alveoli as compared to other alveolar regions. The formation of large aggregates (> 25 particles) increased linearly with initial lung burden starting at 0.4 kBq; mean dose rate to these focal alveolar regions was 120 Gy d-1. Concentration of 239PuO2 in pulmonary macrophages and in aggregates, along with the limited penetration of alpha particles in tissue, resulted in a highly nonhomogeneous dose distribution pattern. Alveolar clearance was best represented by a biphasic clearance curve comprised of a rapid early phase (80% initial lung burden) and a slow late phase (20% initial lung burden). Studies with intratracheally instilled 237PuO2-239PuO2 and with inhaled 239PuO2 showed that alveolar clearance was inversely proportional to initial lung burden. A single clearance function was derived from experimentally determined clearance curves for inhaled 239PuO2 that was used to accurately estimate lung dose at all initial lung burden levels. Lung doses were calculated for 2,105 exposed lifespan rats based on individually determined initial lung burden, survival time, and individually computed clearance function.
吸入放射性核素后，肺内的时空剂量分布模式会持续变化。对暴露于高温烧制的169Yb2O3 - 239PuO2气溶胶的雌性Wistar大鼠进行了肺清除、微剂量测定和辐射剂量研究。暴露后14天对169Yb进行全身计数，准确估计了239Pu的肺含量（r = 0.99）。气管上皮的α辐射比细支气管上皮至少低50倍，这主要是因为与其他肺泡区域相比，239PuO2优先滞留在细支气管周围肺泡中。从0.4 kBq开始，大于25个颗粒的大聚集体的形成随初始肺负荷呈线性增加；这些局灶性肺泡区域的平均剂量率为120 Gy d-1。239PuO2在肺巨噬细胞和聚集体中的浓度，以及α粒子在组织中的穿透有限，导致了高度不均匀的剂量分布模式。肺泡清除最好用双相清除曲线表示，该曲线由快速早期阶段（初始肺负荷的80%）和缓慢晚期阶段（初始肺负荷的20%）组成。对气管内注入237PuO2 - 239PuO2以及吸入239PuO2的研究表明，肺泡清除与初始肺负荷成反比。从吸入239PuO2的实验测定清除曲线中得出了一个单一的清除函数，该函数用于准确估计所有初始肺负荷水平下的肺剂量。根据个体确定的初始肺负荷、存活时间和个体计算的清除函数，计算了2105只暴露的寿命期大鼠的肺剂量。
