Radiotherapy: external beam radiotherapy

Abstract

Design principles for radiotherapy facilities using X-ray, γ‎-ray, and electron beams are described, especially the requirements for primary and secondary shielding and maze and door entrances. These features are illustrated with reference to the shielded rooms (bunkers) required for linear accelerators, and example calculations are included for shielding and maze design to achieve required dose constraints. The impact of new clinical practices with intensity modulated radiation fields and flattening filter-free operation is also considered. Engineering controls and features for safe operation are described, and good practice in bunker construction and the provision of services to avoid weaknesses in the shielding is outlined. The principle shielding requirements for TomoTherapyTM, CyberKnifeTM, Gamma KnifeTM units, and kilovoltage X-ray units are also described. Finally, personnel monitoring, commissioning surveys, and environmental monitoring in radiation protection management in radiotherapy are discussed. Data for calculating shielding thickness and X-ray scatter for maze design are provided.