A Survey of Depth Dose Data

A survey has been made of published depth dose and backscatter data. The influence of (1) focal-skin distance, (2) quality of radiation expressed as half-value layer in copper, and (3) area of field on percentage depth dose has been investigated. In the light of this analysis published data have been corrected to standard radiation conditions, and mean values obtained. Tables have been drawn up giving the percentage depth dose for qualities of radiation from 1·0 to 5·0 mm. copper half-value layer at depths to 20 cm. for field areas up to 400 cm.2 and focal-skin distances from 40 to 100 cm. A less comprehensive survey has been made of radiations up to 17 mm. copper half-value layer, the results of which are embodied in curves and tables. Mean values of percentage surface backscatter have been derived from the literature for field areas up to 400 cm.2 for qualities up to 14 mm. copper half-value layer. Information is also given whereby one may derive half-value layers in copper from the radiation conditions.