The Influence of Energy Absorption and Electron Range on Dosage in Irradiated Bone

Abstract

The problem of dosage in bone, irradiated with X and γ rays, is studied in terms of the ionization received by the soft tissues enclosed in the Haversian systems. The physical radiation dose, in ion pairs per cubic micron per röntgen, is arrived at by calculations of the electron emission of bone in relation to the size of the cavity irradiated. The dose is shown to depend on both cavity size and wavelength of the radiation used. The calculations are shown to be in accord with the relevant available experimental observations and their significance is discussed in relation to clinical experience. The results of the calculations suggest that, for the commonly used 200–250 kV X radiation, the tolerance dose of the soft tissue elements in bone may be only one half of that of soft tissues in other situations. For medium voltage and superficial X rays this relative tolerance may be no more than one-third. Only for short wavelengths, generated at about 1 MeV, does the ionization in the living elements in bone approach that in other soft tissues.