Assessment of the Performance of the Dose Calibrator Used in Radioactivity Measurement.

Aims: This study aimed to evaluate the principal technical characteristics of a well-type gas-filled ionization chamber dose calibrator used in measuring radiopharmaceutical activity, namely accuracy, repeatability, and linearity. Furthermore, this work also explored the correlation between the device's response and the position and volume of the radiopharmaceutical I-131.

Materials and methods: Experimental measurements were conducted on the ATOMLAB 500 dose calibrator using NIST traceable Cs-137 source to determine the accuracy and repeatability. For the linearity test, the Tc-99m solution produced at the Dalat Nuclear Research Institute, Vietnam was utilized to examine the performance of the device over a wide measurement range. Effects resulting from different volumes and measuring positions were also determined by experiments and Monte Carlo simulations.

Results: Based on acceptance test results, it is revealed that the dose calibrator's characteristics comply with international standards, where the deviations of accuracy, repeatability, and linearity are all lower than 1.0%. The response of the dose calibrator to different measuring positions and volumes was well controlled. To rectify the discrepancy in the response to the changes in solution volume, correction functions were proposed.

Conclusions: It is concluded that the dose calibrator is suitable for radioactivity quantification and adheres to standards recommended by international organizations for nuclear medicine activities. The outcome of this work will serve as the foundation for establishing a standard for I-131 radiopharmaceuticals' radioactivity in Vietnam.