Results of an inquiry among end users and calibration labs about the use of medium energy X-rays for therapy throughout Europe – A metrexrt work program

Abstract

Introduction, material and method A work package of the European metrological joint research project (JRP) entitled ‘‘Metrology for radiotherapy using complex radiation fields – MetrExRT” is aimed at studying radiation qualities, measurement conditions and beam quality index suitable for dosimeter calibration in terms of Dw in the conditions of the IAEA protocol 398 for medium-energy X-rays. A survey was undertaken among European end users and calibration labs to select the most relevant beam qualities for dosimeter calibrations and international comparison. It is also aimed at gathering information about the use of medium energy X-rays for therapy. Two electronic questionnaires were circulated, one for the end users, and one for the calibration labs (32 and 9 answers respectively). Results and Conclusions Most of the X-ray generators of the end users were bought before 2000. High voltages lie between 7.5 and 300 kV while for treatment the range is between 10 and 250 kV. Addition filtration is up to 1 mm Cu (150 kV). Dose rates lie between 0.3 and 25 Gy/min, about 80% of the dose rates are below 5 Gy/min and about 10% are below 0.5 Gy/min. Concerning therapeutic indications, 54% are for contact therapy (rectum; skin; eyes; gynecology; etc.), 11% for intra-operative (breast; etc.), benign diseases are also treated. The largest numbers of treatments per year for a given service were found for contact therapy and benign diseases (from 50 to more than 500). Radiation qualities for calibration are chosen mainly in ISO 4037 and IEC 61267 and 60731. The calibration lab facilities cover the range of high voltage used for treatments. Radiation qualities are similar to those mentioned above, as it might have been foreseen, CCRI qualities are more used by metrological labs. Absorbed dose to water for 60Co is mentioned by the end users. The dose rates available at calibration labs are low compare to most of those used for the treatments. This suggests that saturation effect has to be studied to introduce a correction factor if needed. A comparison of the treatment spectra with the ones used by calibration labs will be shown. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union.