Dosimetria em tomografia computadorizada e avaliação das doses nos órgãos em varreduras de tronco

Abstract

Computed tomography has promoted improvement of the diagnostic process by producing anatomical cut images with high quality and contrast between soft tissues which have very similar absorption of the X-ray beams. The objective of this study is to evaluate the technological park of CT in Brazil correlated with the wide world, and carry out studies of experimental dosimetry to understand the dose distribution featureusing phantoms and different methods of measurement of kerma index, as well as perform measures of local doses in sensitive organs. To study the scanner geographic distribution and supply of computed tomography tests in Brazil, a comparison has been made with results found with the specified reference by Brazilian law (Ordinance GM / MS No. 1101, 2002; Resolution RE nº1016, 2006). For dosimetry studies, It was used a standard chest phantom and the anthropomorphic phantom. For image quality evaluation, it was used the CATPHAN-600 phantom. Scans were performed in a GE scanner, Discovery model with 64 channels. Dose measurements have been performed by using a pencil ionization chamber, thermoluminescent dosimeters and radiochromicfilm strips. Sensitive organ shielding devices were evaluated in order to verify their efficiency in organ dose reduction and its influence in the quality of image. Considering Brazilian population, the scanner park showed a greater amount than the minimum parameter recommended by Brazilian law. Dose measurements using three different methods showed the correct procedure of metrological reliability of themeasurement system. The findings and conclusions of this study may contribute to the improvement of local practices in Computed Tomography tests, inserted in context of radiological protection in order to define reference levels for optimized diagnosis, and image quality control.