Quality assurance network: The European pilot study

Based on the IAEA/WHO experience in mailed dosimetry, a Quality Assurance (QA) Network, sponsored by the EC committee ''Europe against Cancer'', has been set up in 1991 for all European centres. Besides a survey of radiotherapy infrastructure, the project includes three measurement steps: primarily, a check of beam output and quality in reference conditions with a mailed TLD-procedure, in a second step, the mailed verification of other beam data and dose calculation procedures with multipurpose phantom, and finally in vivo dosimetry at the individual patient levels with mailed dosimeters. The results concerning 162 beams from 85 centres are analysed (58 60Co beams and 104 X-ray beams). 27 beams present minor deviations (3 to 6%) and 15 beams (4/58 60Co beams and 11/104 X-ray beams) from 11 centres present major deviations (≥ 6%). The analysis shows that 17/27 minor deviations and all major deviations have been detected in centres which have not benefited from an external check during the last five years; in 14 out of 15 large deviations, the measured dose is smaller than the stated dose. In most centres with major deviation, the physicists did not have the necessary experience and did not calibrate regularly the beams. In 6 centres out of 11 there was no dosimeter or the dosimeter available has not been calibrated recently. In 3 centres, the physicist did not give any explanations. The conclusions concerning the second step (multipurpose phantom), outline the larger magnitude of the deviations for off axis points, oblique surface and the use of wedge filters. (author). 32 refs, 7 figs, 2 tabs