Specific Energy Distributions for alpha Emitters in the Dog Lung

摘要

The radiation dose to lung tissue from inhaled alpha-emitting materials is nonuniformly distributed. Dose nonuniformity at the cellular level is due primarily to the particulate nature of inhaled aerosols and the short range of the highly ionizing alpha particle tracks. This nonuniformity can be observed as alpha particle stars in tissue autoradiographs. For a more detailed analysis of the importance of dose distribution, particle size effects, and specific activity of inhaled particles, a microdosimetric approach is needed. For specific energy distributions to be calculated using computer codes, one must characterize the particle size distribution of the inhaled aerosol, consider deposition probabilities in the lung for various particle sizes, and relate the physical size of inhaled particles with their aero-dynamic diameters. Next, one must consider the distribution of target sites and the probability of an alpha particle intersecting one of these sites as it passes through tissue and air space. Finally, the range, energy loss, straggling characteristics and delta ray production of alpha particle tracks must be accounted for. Specific energy distributions provide a graphic display of the dose distribution, and a means for comparing different exposure conditions. The probability density function includes the probability that the target sites are completely missed and remain unirradiated. Similarly, hit probabilities for irradiated sites may also be calculated. Information obtained from specific energy distributions may provide a better understanding of the relationship between dose and biological effects. 15 refs., 8 figs., 2 tabs. (ERA citation 11:010123)