Routine performance (Constancy) testing of radionuclide imaging activity ('Dose') calibrators.

Abstract

Objectives: The purpose of this study was to set up and implement a constancy testing programme for the radionuclide (dose) calibrator found in the local radiopharmacy, to verify whether the mentioned calibrator is working as it should, thus ensuring that the right activities are being administered to the patients, and to obtain baseline values against which routine measurements and future studies can be compared. Research Design: The methodology involved the development of a constancy testing protocol consisting of a set of Performance Indicators based on IEC standards 61303 ('Medical Electrical Equipment- Radionuclide Calibrators') and TR 61948-4 ('Nuclear Medicine instrumentationRoutine Tests - Radionuclide Calibrators ') as suggested by The Ionizing Radiation Medical Exposure Regulations 2004. Initial Manual Check comprising a Self-Test, Inherent Background Response and Constancy of Instrument Response were investigated on each day of use of the dose calibrator for a two-month period. The System Linearity Test was carried out once as suggested by the IEC standards. An innovative procedure for the latter test was developed and this is referred to as the 'Modified Method'. Results: The results acquired during the data collection period were represented mainly as QC charts. With respect to the Atomlab Dose Calibrator under study: i) No errors were registered by the Self-Test ii) The Initial Manual Check and Inherent Background Response presented a relatively large number of values which exceeded their corresponding acceptable limit. iii) The Constancy of Instrument Response presented values which were constant during the period under investigation but these were all well above the acceptable limit. iv) The dose calibrator is linear in measuring radioactive decay for the activities tested. Conclusions: A protocol for Constancy Testing of the radionuclide calibrator was developed as requested by the Maltese Legislation, and this would serve as a basic protocol for the development of a full protocol for the calibrator under study. Moreover, the acquired results for the tested Performance Indicators would serve as reference data against which routine measurements and future studies can be compared. Finally, it can be conclude that the results obtain do not guarantee that the dose calibrator is working as it should and therefore accuracy of dose administration is in serious doubt.