Evaluación del deterioro de la calidad del tomógrafo Siemens Emotion 6 del Hospital SOLCA Núcleo-Quito y su influencia en las dosis y calidad de imagen

Abstract

In this study, the dose variation and the image quality of the Siemens Emotion 6 computed tomograph during the life time of the X-ray tube was evaluated. For this, five clinical protocols for both adult and pediatric patients were studied. The evolution of the doses in the center of a CTDI phantom, the modulation transfer function (MTF) and the noise power spectrum (NPS) in the ACR phantom was studied, the latter is a measurement of the image quality and we found that, with 95% of confidence, it does not exist correlation between dose and time neither between time and the image parameters. The X ray tube state was monitored with the evaluation of the beam characteristics, that is, the measurement of the hemyreductive layer (HVL) decreased a maximum of 0.158 mmAl for 110 kV and 0.267 mmAl for 130 kV, in agreement of the tolerance limits of the quality control protocols in tomography, the distribution of the kerma in air along both the rotation axis of the tomograph and the transverse axis during the study is less than 8% with respect to the mean value. Therefore, the normal deterioration of the equipment during the life time of the X ray tube will not significantly afect the medical diagnosis.