Quality assurance in radiation therapy: clinical and physical aspects. Quality assurance in dosimetry and treatment planning.

The considerations of tissue response to radiation absorbed dose suggest a need for an accuracy of +/- 5% in its delivery. This is very demanding and its regular achievement requires careful quality control. There are three distinct phases to the delivery of the planned treatment: calibration of the radiation beam in a reference situation, calculation of the dose distribution for a patient relative to the reference dose and the delivery of the radiation to the patient as planned. Each has distinctly different quality assurance requirements and must be diligently observed if the desired accuracy is to be achieved.