Some aspects of radiation safety for electron accelerators used for both x-ray and electron therapy.

Abstract This report concerns certain aspects of radiation safety for megavoltage electron accelerators used for both X-ray and electron therapy, particularly linear accelerators. 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 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 our relevant failures, the use of secondary emission monitors, beam loading and a number of peripheral consid...