Controlo automático de exposição (CAE)

: dose no doente e qualidade de imagem

Abstract

The automatic exposure control (AEC) is the system that supports the definition of the parameters that will lead to exposure and dose to the patient. Whereas the measuring circuit system that is unique and is calculated (and consequent cutting) by averaging the received signal, without regard to the asymmetry of the density gradient coincident with the field of the respective exposure detectors, formulated as objective to determine the influence of various configurations of the EAC in the patient dose and image quality in a system of Computed Radiography (CR) in three regions of an anthropomorphic phantom: chest, abdomen and pelvis. Followed the criteria recommended by international Guidelines and the images were saved in Dicom and identified for further analysis in software OsiriX. The values for each exposure were treated in the Statistical Package for Social Sciences (SPSS) and determined the mean, standard deviation, standard error, variance and performed the Tukey test (HSD). In the thorax, it was found that, using the obtained lower right AEC absorbed dose in other configurations: – 6,1% on the left – 39,7% than when using the central and – 8,6% and – 26,8% compared to the use of two to three sides and at the same time, respectively. The abdomen was obtained using the lowest dose absorbed AEC left: on the right – 6,4%, relative to center – 22,2% on the two sides and three simultaneous – 2,5% and – 8,2%. In the lower bowl the absorbed dose was obtained by selection of AEC central, both in relation to any of the three sides and simultaneously, with values – 55,2% and – 30.8%, respectively. Whereas a partial prosthesis on the left hip accentuate differences in relation to the selection of the two and three detectors for simultaneously – 58,1% and – 30,1% and coincident with a value of the prosthesis – 83,3%. It is concluded that the importance given to the selection detector/s AEC has direct action in reducing the dose to the patient, without changing the image quality and that the recommendations of the Guidelines are not always in accordance with the Principle of Optimization (Directive 97/43 Euratom). The results indicate the need to review the settings suggested by AEC Dimond III and European Guidelines which can be proven with a study correlating the values obtained in the phantom with a corpse, which is suggested as future work.

Date of Award	2012
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Francisco José Cerqueira Alves (Supervisor)