Photoelectron enhancement of the absorbed dose from X rays to human bone marrow: experimental and theoretical studies.

A technique is described by which lithium fluoride powder is introduced into the marrow cavities in specimens of human trabecular bone to determine the excess photoelectron dose to marrow, when bone is irradiated by X rays of energies between 20 keV and 140 keV. Three specimens of trabecular bone, containing respectively 10, 15 and 25% bone by volume, were investigated and the results compared with those derived on the basis of earlier calculations for mono-energetic electrons by Whitwell. Reasonable agreement was found between the experimental and theoretical results, although there was some indication that scatter influenced the practical measurements at the higher photon energies. Theoretical calculations are then used to derive photoelectron dose enhancements for complete bones from the measured results on the bone specimens, and mean enhancements of the marrow dose for the whole human skeleton are calculated for subjects aged 44, 9 and 1.7 years.