The transformation method for the MIRD absorbed fraction as applied to various physiques.

A transformation method was investigated for applying the MIRD absorbed fraction to internal dose calculations for an individual. The transformation method consists of two parts, transformation of the target organ mass, and of the distance between source and target organs. The variation of the specific absorbed fraction with distance in the human body was approximated with the traditional exponential form. To examine the transformation method, experiments were carried out for cobalt-60 gamma rays, using LiF-TLD, with the thyroid and ovaries as source organs. The transformed values of the MIRD absorbed fractions agreed well with the experimental values. Some results obtained from the MIRD values by these transformation methods were also compared with those for younger age groups calculated by Snyder.