Quality control of radiotherapy centres in Europe: beam calibration.

A European Quality Assurance Network for external radiotherapy was set up. In this, several countries participated on a voluntary basis to elaborate common protocols, using joint infrastructure. The support for the co-ordination of the project was given by the EC committee 'Europe Against Cancer'. In the first step of the programme, beam outputs and beam qualities are checked with mailed thermoluminescent dosimeters following the protocol prepared by the IAEA. The results concerning 125 beams from 66 centres are analysed. Twenty-two beams presented minor deviations (3-6%) and 15 beams (4/48 60Co beams and 11/77 X-ray beams) from 11 centres presented major deviations (> or = 6%). The analysis shows that 16/22 minor deviations and all major deviations have been detected in centres which have not benefited from an external check during the last 5 years. In 14 out of 15 large deviations, the measured dose was smaller than the stated dose. In most centres with major deviation the physicists did not have the necessary experience and did not regularly calibrate the beams. In 6 out of 11 centres there was no dosimeter or the dosimeter available had not been calibrated recently. In 3 centres, the physicist did not give any explanation.