Evaluation of Measurement Accuracy and Inter-institutional Comparison for Dose Calibrators

Purpose: The aim of this study was to validate the reliability of dose calibrators for measuring the radioactivity of several radioisotopes in multi-institution. Methods: We evaluated the measurement accuracy of dose calibrators using a commercially available source (67 Ga, 99m Tc, 123 I, 201 TL). Nine dose calibrators (five models) in seven institutions were performed in this study. Each source was measured at least 3 times a day over a period of 4 half-life. Linearity of concentration (%error value) and percent difference values (%diff measurement) between measured and estimated radioactivity were calculated to evaluate the measurement accuracy. In addition, difference among institutions (%diff institution) was evaluated by the error values between measured and reference institution values. Results: Good linearity of concentration was found between measured and estimated radioactivity in 99mTc and 123I. However, %error value was increased in 67Ga and 201TL (maximum 19.3%). %diff measurements were 1.9 ± 0.3% for 67Ga, −0.9 ± 0.3% for 99mTc, 2.2 ± 0.4% for 123I, and −0.7 ± 0.3% for 201TL, respectively. Although there were no clear differences in six institutions, %diff institution in one institution tended to be higher than that obtained in other institutions. Conclusions: Our results indicated that measurement accuracy of nine dose calibrators (five models) was relatively stable. However, difference of measured values tended to be higher in a part of institution and source. It is important to perform quality assurance and quality control for dose calibrator using traceable source.