The 1998 radionuclide dose calibrator survey

Australian Radioisotopes (ARI) is appointed as a Verifying Authority under the Regulations to the National Measurement Act, 1960, which means that the calibration sources are directly traceable to the national standard. ARI is able to issue calibration sources of 99mTc and 1'31I, with a least uncertainty of two per cent, and 67Ga and 201Tl, with a least uncertainty of five per cent, in an activity range of 100 - 6000 MBq. As in the previous surveys the following sources were available: 99mTc -600 MBq in 5 mL; 131I-600 MBq m 3 mL; 131I-6 GBq in 3 mL; 67Ga-200 MBq in 2 mL and 201Tl-125 MBq in 1 mL. Participants were asked to measure each source ten times, repositioning the source between each measurement. Those institutions which received the 6 GBq source of 131I remeasured it when it had decayed to 600 MBq. The minimum, maximum and mean of the ten readings were recorded. After correcting for decay between the time of calibration and the time of measurement, the difference between the calibrated activity and the measured activity was expressed as a percentage of the calibrated activity. The ANSI Standard for dose calibrators (Calibration and usage of 'dose calibrator' ion ionisation chambers for the assay of radionuclides) states that the measured activity shall be within ±10 per cent of the stated activity. The reproducibility of the measurement was calculated as (max-min)/2 as a percentage of the mean value. The ANSI Standard states that all the results of the ten consecutive measurements shall be within ±five per cent of the average. Copyright (1999) The Australian and New Zealand Society of Nuclear Medicine Inc