Scattered Radiation from Beam Modifiers Used with Megavoltage Therapy Units

Abstract

The magnitude and distribution of scattered radiation produced by scatterers inserted into megavoltage therapy beams, including the beams from an 8MV medical linear accelerator and a 60Co teletherapy unit, were investigated. The intensity distribution of scatter depended on the distance from the scatterer to the measurement plane (retraction distance) and also, to a lesser extent, on the atomic number of the scattering material. The effective energy of the scattered radiation was determined by depth dose measurements in tissue equivalent material using thermoluminescent dosimeters and increased with photon beam energy.