Some Aspects of Radiation Safety for Electron Accelerators Used for both X-ray and Electron Therapy

Abstract

Aspects of radiation safety for megavoltage electron accelerators used for both X-ray and electron therapy, particularly linear accelerators are discussed. Such accelerators pose a specific radiation hazard. The hazard arises in ensuring that the devices and procedures required for the large reduction in electron beam current associated with the electron therapy modality are sufficiently rigorous, both technically and operationally, to render it exceedingly unlikely for patients to be exposed to excessive electron doses as a result of a technical failure and/or an operational inadvertence. This note describes some of the radiation safety features of a 5 MeV [million electron volts] accelerator used routinely for both X-ray and electron therapy. Included are a description of the X-ray/electron therapy changeover procedure, the radiation monitoring system, the accelerator electron gun design, data on relevant failures, the use of secondary emission monitors, beam loading and a number of peripheral considerations relating to radiation safety.