Estudo da velocidade de exposição radioactiva de doentes submetidos a cintigrafia de perfusão do miocárdio após primeira e segunda injecção do radiofármaco, no mesmo dia

Abstract

The main aim of this study was to determine the exposure rate from patients who went through clinical routine myocardial perfusion imaging studies that include two injections of the requested radiopharmaceutical. Furthermore, there was an imminent interest in analysing the reduction of this value by applying the effect of “emptying bladder”, previously to patients’ exit from the hospital building. Searching for a comparative evaluation, the exposure rate from the recommended radioactive activities for these myocardial perfusion studies and oriented by the European Association of Nuclear Medicine (EANM) was also estimated. Additionally, the effect produced by increasing distance was analysed, both in evaluating the exposure rate variation, by emptying the bladder, and, in a last test, establishing the area as a study-case. Once there was a need to establish the protocol acquisition time, the present work compared the information that resulted from measures obtained during 10 and 60 seconds. On developing all research, the Geiger-Müller counter was used to collect all measures. Therefore, the basic implemented methods were due to measurements at thorax and bladder levels. Finally, a rectangular phantom and a point source were measured. The main results showed no differences between applying 10 or 60 seconds for the time during which the exposure rate was measured, and a significant decrease on exposure rate, whenever measures after “emptying bladder” were compared with measures before “emptying the bladder” (18.5 and 20.6% less than full bladder, near the thorax and bladder, respectively). The averaged exposure rates, found after a first injection, were 8.62 and 10.78 μSv/h. Following the second radiopharmaceutical administration, those rates were 25.15 and 30.85 μSv/h, at thorax and bladder levels, respectively. The use of the recommended activities of EANM leaded to a clear increase of the exposure rates, after both injections, i.e. at the end of the examination. Distance proved to be critical in the interpretation of the effect “emptying bladder”, as well as the introduction of the variable “area”, in measuring exposure rates, showed to be crucial in the applied context. This study showed that the exposure rates, in patients that underwent myocardial perfusion imaging, did not exceed the established limit value (50μSv/h) for release into the general environment. Nevertheless, adopting a systematic protocol obligation to recommend patients to empty their bladder before leaving the Nuclear Medicine facility can reduce exposure rate values even further and, therefore, reduce the potential environmental contamination.

Date of Award	2012
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Durval Campos Costa (Supervisor), Diogo Alexandre Borges de Faria (Co-Supervisor) & Joana Vale Ferreira da Silva (Co-Supervisor)