Development of quality assurance in radiation therapy in North America

Although diagnostic radiology developed rapidly following Roentgen's discovery, limitations on voltage delayed penetrating external radiation therapy until after World War II. Quality assurance has developed in both the USA and Canada in many different institutions. Tolerances for implementation of the prescribed tumor dose have been established. A series of quality assurance procedures for calibration, three dimensional dose distributions, the treatment planning process, and for treatment delivery have been formulated in protocols and their development is sketched briefly. The importance of computerized tomography in treatment planning and computerized record and verify systems in treatment delivery is emphasized.