Dose Calibrator Performance and Quality Control

Two different dose calibrators were studied and their performance measured using the following tests: (A) linearity of response over all activity ranges, (B) accuracy when measuring some commonly used radionuclides, (C) the effect of container configuration on the accuracy of measurement, and (D) daily and long-term stability of the instrument. For each instrument tested, a good linear response was observed for activity measurements below 100 mCi, but there was evidence of nonlinearity at higher activity levels. The accuracy of each instrument was checked using radionuclide standards from two different sources. The measurements indicated a significant difference between standards that was not possible to resolve. Additionally, assessment of accuracy for a dose calibrator with any standard is difficult unless the manufacturer's calibration procedure is known. The effect of container configuration and photon energy on the accuracy of measuring 99 .. Tc, 13IJ, and I25J indicated that large correction factors may be necessary when making measurements of 125/. The measurement of a long-lived standard such as radium, cross calibrated for several radionuclide settings, is an effective means for assurring instrument stability and quality control on a daily and longterm basis.