Local Dose to Lung Tissue from Inhaled 238 PuO 2 Particles

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Abstract
A new method for computation of local dose to tissue from an .alpha.-emitting particle in deep lung is described. Syrian hamsters were exposed via inhalation to a monodisperse aerosol of 0.2 .mu.m real diameter 238PuO2 particles. At 8-35 days after exposure the animals were sacrificed, the lungs were inflated and fixed in situ, excised, paraffin embedded, sectioned at 5 .mu.m thickness and autoradiographs were prepared. Particles were chosen at random from these autoradiographs and the location of the particle and configuration of the tissue surrounding the particle were input to a computer. Local dose rate and fraction of .alpha.-particles which penetrated to a pass through tissue at a given distance from the source were computed. Local dose rate was used to compute the effect of this radiation pattern based on 4 empirical formulae. Average effects obtained were similar to those calculated assuming a structureless lung of uniform density 0.2 g/cm3, but different from calculated effects based on uniform dose over the irradiated region. Under the dose effect assumptions used, tumor induction probability per .alpha. disintegration of a 238PuO2 particle in deep lung was inversely related to particle activity.

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