Desenvolvimento de fantoma para teste de controle de qualidade da modulação de corrente em tomografia computadorizada

Abstract

The automatic tube current modulation (ATCM) system in computed tomography (CT) is an essential function in CT scanners that is intended to reduce the dose delivered to the patient during the examination. A phantom is needed to perform quality control testing of the current modulation, evaluating how the CT scanner system adapts the xray tube current to the size of the object. Commercial phantom options have a low costbenefit in the national scenario since most phantoms are available only with high-value imports. Based on international quality control recommendations and national standards/ legislation, a relatively low-cost phantom was developed using nationally available materials for the automatic current modulation test, and a methodology was developed to carry out this quality control test. The phantom was built with material that mimics biological tissue when exposed to X-rays, an in a cylindrical shape and easy to transport, and it is composed of three modules and two fixation bases. To verify the applicability of this phantom, automatic current modulation tests were performed in CT scanners from different manufacturers (Toshiba, Philips, and General Electric). The results showed that with a discrete change (abrupt/sudden) in the phantom size, there was a corresponding change in the X-ray tube current. This indicates that the CT systems could adapt the tube current using a discrete change in attenuation, but in some cases, the results exceeded the reference value of the national legislation of 20% in compensation of the automatic tube current modulation for testing with phantoms of different thicknesses. It was concluded that the developed phantom presented as a national option with affordable cost and ease to use can be used in quality control tests of automatic current modulation.