Accuracy Testing of Dose Calibrators

Current methods for testing a dose calibrator's accuracy use measurements of /sup 60/Co, /sup 137/Cs, /sup 57/Co, and /sup 133/Ba sources but do not directly measure the accuracy of clinical radionuclides such as /sup 99m/Tc, /sup 123/I, /sup 111/In, /sup 67/Ga, or /sup 201/Tl. It is possible that some dose calibrators inaccurately determine the activity of these clinical radiopharmaceuticals. To correct this possible deficiency, the authors have devised a method to test the accuracy of each radionuclide setting on a dose calibrator using a single long-lived calibration source. Differences in emission characteristics of assayed radionuclides are incorporated in the ionization current-to-activity conversion factors (CAF) that are determined experimentally by the manufacturer. The correct functioning of a dose calibrator requires that each CAF be accurately reproduced electronically by the calibrator circuitry and that the measured ionization current be consistent and precise. The results have shown that their procedure tests the total function of the dose calibrator for detecting all radionuclides specified by the manufacturer including the accuracy of the electron representations of the CAF. The procedure is easily implemented for all dose calibrator systems using one of several possible sources available in most laboratories (e.g., /sup 57/Co, /sup 137/Cs, or /supmore » 133/Ba).« less