Quality assurance in radiation therapy: clinical and physical aspects. Radiation protection

One usually thinks of radiation safety as keeping patient and personnel exposure as low as reasonably achievable; however, radiation protection activities play an important role in quality assurance for both the clinical and physical aspects. Radiation protection has several aspects: The first step is the design of the irradiation device and its shielding. While this step is out of the hands of the user, the location and level of leakage radiation must be verified by the user. Periodic leak testing of sealed sources is required. Room shielding design is based on the leakage levels specified by the manufacturer and on levels of scatter and primary radiation impinging on the radiation barriers. The addition of shielding for photoneutrons should be planned for accelerators producing photons above 10 MeV. Integrity and adequacy of shielding should be verified by survey after unit installation. Installation and periodic testing of interlocks are necessary to assure that nonirradiation conditions can be restored as soon as necessary. Personnel monitoring serves two purposes; to provide a record of personnel exposures and to alert one to unsuspected changes that may have taken place in procedure, shielding integrity, or source location. Area monitoring and survey on a periodic basis also provides knowledge of unsuspected changes in procedure, shielding integrity, or source location. Brachytherapy and the transport of small radiation sources require additional precautionary actions. Protection of patient anatomy not being treated reduces the chance of normal tissue damage and the possibility of carcinogenic effects.