Microdistribution and Localized Dosimetry of²⁴¹Am in Bones of Beagle Dogs

Abstract

The microdistribution of 241Am in selected bones of seven beagle dogs was analysed using a computer controlled microscope photometer. Four of the animals receiving between 102.5 and 165 kBq/kg were killed between 7 and 20 days after injection, and three animals receiving 32.9-34.0 kBq/kg were killed between 1300 and 1569 days. Using the photometric scanning technique, the concentrations of 241Am in several anatomical regions, as well as the specific surface activities and their variations, dose rates, accumulated radiation doses, burial depths and morphometric parameters, were derived. Dose rates to the 0-10 micron marrow band adjacent to surfaces were found to be between 8.6 and 15.7 times higher than the average skeletal dose. Accumulated radiation doses from initial deposits to lining cells were estimated to be between 87 and 252 Gy. The average burial depth in the animals killed at later times was around 8 micron. Morphometric parameters showed that radiation damage occurred in these animals, resulting in abnormal trabecular architecture. A positive correlation between specific surface activity and local turnover rates was established.

Internal microdosimetry of alpha-emitting radionuclides

“…Thus, the microdistribution of the alphaemitting radionuclides in the bone is a major determinant of the microdosimetry in bone target cells. Experimental methods to determine such microdistributions are photographic emulsion autoradiography (Polig 1978), solid-state nuclear track detector (SSNTD) autoradiography (Polig et al 1984b;Austin et al 1999Austin et al , 2000, and, most recently, digital autoradiography using an ionizing-radiation quantum imaging detector (iQID) camera (Miller et al 2014;Tabatadze et al 2016) for alpha particles, and neutron-induced autoradiography (NIAR) in the case of the fissionable nuclides 239 Pu and 241 Am (Polig 1978;Polig et al 1998;Austin et al 1999Austin et al , 2000.…”

“…A summary of microdistribution studies for 226 Ra, 241 Am and 239 Pu prior to about 1975 can be found in Polig (1978). Since then, animal studies on injected 241 Am and 239 Pu in beagle dogs (Polig et al 1984b(Polig et al , 1998 and injected 241 Am, 239 Pu and 233 U in mice (Austin et al 1999(Austin et al , 2000 have been reported, while the USTUR case 246 (Priest et al 1995) refers to the 241 Am contamination of a radiation worker in an americium recovery factory who was involved in a glove-box explosion. Due to the process of bone remodeling, the initial microdistribution of 239 Pu, 241 Am and 233 U changes with time after injection (Austin et al 1999(Austin et al , 2000.…”