The results of the 25 participants of the EUROMET.RI(I)-K1 and EUROMET.RI(I)-K4 key comparisons are reported to support their relevant CMC claims being published or going to be published by the participant laboratories. The measured quantities were the air kerma (Kair) and the absorbed dose to water (Dw) in Co-60 radiotherapy beams. The comparison was conducted by MKEH in a star-shaped arrangement from January 2005 to December 2008. The calibration coefficients of the four transfer chambers were measured using two electrometers and the associated uncertainty budgets were reported by the participants, enabling the calculation of degrees of equivalence (DoE), the differences and their uncertainties of each national standard with respect to the key comparison reference values determined the BIPM for both quantities. The largest deviation between any two respective calibrations coefficients for the four chambers in tem of air kerma and absorbed dose to water was 2.7% and 3.3% respectively. The BIPM.RI(I)-K1 and EUROMET.RI(I)-K4 comparisons in the key comparison database (KCDB) will include eleven new Kair and fourteen newDw DOE values enable them to update their participants having primary standards and DoE values, the new linked DOE values enable them to update their previous values while assessing their calibration techniques and uncertainty budgets. The pair-wise degrees of equivalence of participants are calculated. The comparison program also delivered experimental determinations of NDw/NK2 ratios in Co-60 gamma radiation for the four principal transfer chambers used in radiotherapy worldwide.
Pub Type: Journals
absrobed dose, air kerma, cobalt-60, comparison, ionization chamber, Euramet