Dose enhancement from backscattered radiation at tissue–metal interfaces irradiated with high energy electrons

Abstract

Irradiation of a tissue-metal interface with 13-20 MeV electrons results in an increased dose to the tissue on the entrance side of the metal. Ionization measurements were made with a thin-window parallel-plate chamber to determine the magnitude of the dose enhancement as a function of incident electron energy, thickness and atomic number of metals introduced into the electron beam. The presence of a metal resulted in a dose ranging from 6% to .apprx. 50% greater than that measured with no metal in the beam. Most of this increase in dose may be eliminated by the addition of 1-2 g/cm2 of low Z [atomic number] material between tissue and metal. [Electron beams are frequently used in the treatment [in humans]].