Calibration of patient dose monitoring devices in diagnostic radiology has
become increasingly important in the light of new legislation that requires
monitoring of patient dose against local and national diagnostic reference
levels. An investigation was conducted into the long-term stability of 41
dose-area product (DAP) meters over a period of approximately 5 years, to a
ssess the suitability of an annual calibration regimen. For DAP meters fitt
ed to overcouch X-ray tubes, 77% of calibrations were within 10%, whilst fo
r undercouch tubes only 50% of calibrations were within 10%. These findings
suggest that annual calibration may be too infrequent. Suitable calibratio
n frequencies for different clinical workloads are discussed.