ABSTRACT
Radiotherapy is a form of treatment that is directed towards the eradication of tumour
cells and it has the inherent potential to damage normal tissue also. Calibration errors can
lead to injury in a large number of patients. A systematic approach to the quality assurance
of the whole radiotherapy process is therefore essential (WHO 1988; AAPM 1994a;
Thwaites et al. 1995).
