Performance evaluation of the reference system for calibration of ipen activimeters
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PERFORMANCE EVALUATION OF THE REFERENCE SYSTEM FOR CALIBRATION OF IPEN ACTIVIMETERSElaine Wirney Martins and Maria da Penha A. Potiens
Instituto de Pesquisas Energéticas e Nucleares (IPEN / CNEN - SP) ewmartins@ipen.br, mppalbu@ipen.br @ipen.br
INTRODUCTION
The formation of good quality image in nuclear medicine services depends on several factors, including the radiopharmaceutical activity, which must be well determined by a specific apparatus, in perfect operating condition, called activimeter. Therefore, the establishment of a quality control program for measuring the radiopharmaceuticals radioactivity before being administered to the patient is crucial to the safe and effective use of the radiopharmaceuticals used in diagnostic and therapeutical procedures. Due to the large number of procedures performed with the use of ionizing radiation in medicine, it is necessary to use of a substantial number of activity equipment meters in order to cover all NMS, and concerns about the development of quality control programs as well as radiological safety are inevitable. Several factors influence the accuracy of the dose given by activimeters. Before becoming available for sale, the activimeter, after its manufacture, is submitted to calibration using a set of certified sources. The manufacturer limits its initial accuracy to a range between +/- 1% and +/- 5%. Over time this accuracy can vary due to pressure changes in the gas of its chamber and electronic attraction. To ensure the proper operation of the instrument, due to these variations, regular tests were established to be applied at specific intervals. There are three types of tests which are part of a quality control program: (I) acceptance tests, (II) reference tests, (III) operational tests.
RESULTS
Precision: the maximum percentage deviation between the individual activity measure (Ai) with respect to the measured mean activities (Ā) was less than 0,32% for all the tests performed, not exceeding the