Skeletal absorbed fractions for electrons and alpha particles in the adult male – considerations of a revised 50-μm definition of the bone endosteum.

In 1995, the International Commission on Radiological Protection (ICRP) issued ICRP Publication 70 which provided an extensive update to the physiological and anatomical reference data for the skeleton of adults and children originally issued in ICRP Publication 23. While ICRP Publication 70 has been a valuable document in the development of reference voxel computational phantoms, additional guidance is needed for dose assessment in the skeletal tissues beyond that given in ICRP Publication 30. In this study, we present a CT and μCT based model of the skeletal tissues which (1) considers a 50-μm depth in marrow for the osteoprogenitor cells, (2) considers electron escape from trabecular spongiosa to the surrounding cortical bone, (3) considers cortical bone to spongiosa cross-fire for electrons, and (4) considers variations in specific absorbed fraction with changes in bone marrow cellularity for both electrons and alpha-particles. Two representative data sets are given: electron dosimetry cranium and alpha-particle dosimetry lumbar vertebrae