IAEA-SSDL bilateral comparisons for diagnostic level air kerma measurement standards

Comparisons of national standard of air kerma for conventional and mammographic diagnostic X-ray radiation qualities were conducted by the IAEA. Eleven secondary standards dosimetry laboratories provided calibration data for Exradin A3 and Radcal RC6M transfer ionization chambers circulated. Each comparison result expressed as the ratio of the participant and IAEA calibration coefficient were within the acceptance limit of ±2.5%. From the 67 results of 11 participants and 10 available beam qualities, the comparison result was within its standard uncertainty in 63 cases, and within the expanded (k = 2) uncertainty in four cases. Detailed calibration uncertainty budgets from participant laboratories are presented. The relative standard calibration uncertainty of each participant was in the range of 0.5-1.3%. These results indicate that the calibration related uncertainty component is reasonable low for a clinical measurement. In addition to the calibration coefficient, other corrections should be applied for clinical measurement to achieve the recommended accuracy.