Microdosimetry of alpha-emitting bone seekers.

Microdosimetric probability distributions of specific energy f(z) in cell nuclei at alpha-contaminated bone surfaces are determined. The calculations are based on autoradiographic measurements of specific endosteal surface activities of rats injected with 239-Pu. The effect of a variation of the surface activity and target density and a correlation of both is discussed. A mathematical description of trabecular bone remodeling is given and the dependence of specific energy deposition on remodeling processes is demonstrated. For non-age-dependent remodeling and relatively large numbers of hits (greater than 20) the main contribution to the variation of f(z) comes from the variation of residual lifetimes and specific surface activities. With small numbers of hits (less than 1) the variation is mainly determined by the Poisson hit statistics and the width of the single event spectrum.