Attenuation of Monoenergetic Gamma Rays in Tissues

Using gamma-emitting radioisotopes and a crystal spectrometer we measured linear attenuation coefficients for a variety of tissues at photon energies of 27, 60, 122, 279, and 662 kev. The fractional standard deviations of the observed values varied with tissue thickness, but were about 0.5 per cent in most of the cases. Specific gravities of the tissue samples were measured wherever feasible. Our results indicate that the attenuation coefficients of different parts of the same organ may vary by up to 1 per cent. For most of the tumors investigated, no significant differences were found between the attenuation coefficients of cancerous tissues and their normal parenchyma.