Speaker
Description
To assess the measurement capabilities of UK hospitals for commonly used radionuclides, and to identify any key areas of improvement, data has been collected during the routine calibration of hospital radionuclide calibrators. The calibration service operated by the NPL involves hospitals measuring a radioactive source in their calibrator before shipping it to the NPL for standardisation. The sources are calibrated using a secondary standard ionisation chamber with verification and purity measurements performed by gamma spectrometry. The results are returned to hospitals in the form of a calibration certificate and adjustments may be made if their measurement falls outside of acceptable limits (typically ±2 % for gamma emitters and ±5 % for pure beta emitters). This work was designed to complement the ongoing comparison exercises undertaken by NPL over the last decades.
Prior to receiving the calibration certificate, hospitals were asked to provide the make and model of calibrator, the dial setting used, the measured activity, measurement uncertainty and reference time. Once received at the NPL the sources sent were measured on two commercially available calibrators, using the manufacturer supplied settings for each radionuclide. Data was grouped by radionuclide and geometry to account for the different dial settings or calibration factors in use. The results show that even for routinely used and relatively simple to measure radionuclides such as 99mTc, differences of up to 15 % are observed. Results also show that geometry can have a significant effect on measurement accuracy when non geometry specific dial settings are used.
