A method for calculating the dose due to capture gamma rays in accelerator mazes.

An empirical technique for calculation of the capture gamma ray dose in the maze of high-energy medical accelerators is described. The total photon dose was measured along the maze centre line and by use of a graphical technique the capture gamma dose and the low-energy photon dose component were determined. Tenth-value lengths for both photon dose components are reported for four medical accelerators operating with megavoltages in the range 16.8-22.0 MV. The capture gamma dose and the low-energy photon dose in the maze were related to the following parameters: the room surface area, the distance from the isocentre to the inner maze entrance, and the neutron head leakage at a fixed distance from the target.