Simulation and measurement of air generated electron contamination in radiotherapy

Monte Carlo simulations using MCNP4A and experimental work have been perfor med to evaluate the contribution of electrons that are produced in air from a 6 MV x-ray beam produced by a medical linear accelerator. Results show t hat up to 9% of applied dose is delivered to a patient's skin surface from electrons excited in the irradiated air column. For most field sizes this c onstitutes approximately 30% of dose delivered to this region. This study g ives clinically relevant information on the origins and quantity of electro ns at the skin of patients undergoing radiation therapy. (C) 2000 Elsevier Science Ltd. All rights reserved.