A new analytical method for estimating electron-absorbed fractions in soft-tissue biological volumes.

A new analytical methodology was developed for estimating electron-absorbed fractions in soft-tissue biological volumes from mono-energy emitters, uniformly distributed within these volumes. The approach was originally developed for soft-tissue spheres and was extended to ellipsoids. The method involves a procedure of size rescaling to the electron CSDA ranges. The rescaling was applied to large published datasets of electron-absorbed fractions in soft-tissue spheres. A new effect was demonstrated, i.e., that it is possible to describe the rescaled data on absorbed fractions by a single smooth 'universal curve'. A simple analytical formula is suggested, which describes the curve as a function of a single argument (the so-called rescaled radius) with saturation. Practical application of the method for estimating internal doses to non-human biota was demonstrated. It is concluded that the method provides an effective analytical tool for calculating the electron-absorbed fractions in soft-tissue bio-volumes relevant to various organisms and organs.