Lung Irradiation with Static Plutonium Microspheres

Abstract

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Lung tumor induction in Syrian hamsters with internally deposited particulate Pu: A synthesis based on microscopic dose distribution

“…Since the microspheres did not move around in the lung, the dose distribution remained constant throughout the lifetime of the animals. Movement of the lung caused by breathing might result in slightly different dose distributions than those predicted from a static lung configuration, but the differences should be minor since the dose rate at a given point depends only on the tissue penetrated to reach that point; this distance through tissue should not change much with the contraction and expansion of the lung: The 1 MeV self-absorption in the 10 ~m diameter microspheres (Anderson et al 1974) was taken into account in these calculations by using the measured Bragg curve for a particle with a loss of 0.7 MeV per emission (Harley et al 1975). All lung tumors were included in this analysis.…”

“…Syrian hamsters exposed to alpha irradiation from internally deposited randomly distributed stationary microspheres containing Pu (Anderson et al 1974;Anderson et al 1979) furnished an ideal model to obtain a dose-effect relationship for randomly distributed particles in lung. Since the microspheres did not move around in the lung, the dose distribution remained constant throughout the lifetime of the animals.…”

“…Dose-effect data for Syrian hamsters injected with Pu-labeled microspheres in the jugular vein (Anderson et al 1979) were used to determine the constants appropriate for these two expressions. The microspheres injected in this way lodged in the microvasculature of the lung resulting in a static random distribution of the microspheres, which for any given injection group were all of the same activity per microsphere (Anderson et al 1974). Random simulations at the appropriate microsphere specific activity and average concentration of microspheres per unit volume of lung were used and the total dose to target tissue at any point in the lung was computed by multiplying the dose rate to tissue at that point, computed as outlined above, times the median lifespan of the animals in that group since the microspheres were retained in the same position for the total lifetime of the animal.…”

“…The dose and tissue-at-risk distributions measured were used with existing dose-effect models to compare the results of several studies in which Syrian hamsters had long-term burdens of Pu particles in lung. The best model of lung tumor induction obtained from an "ideal" experiment (Anderson et al 1974;Anderson et al 1979) was found to fit lung tumor induction results from experiments in several laboratories involving a variety of exposure aerosols.…”