Tese
Redução de dose em varreduras de tomografia computadorizada de tórax - otimização de protocolos utilizando objetos simuladores adultos e pediátricos
Fecha
2021-04-22Autor
Wadia Namen Aburjaile
Institución
Resumen
Computed tomography (CT) images are very detailed and used for medical diagnosis, being
considered relevant in ionizing radiation applications. Due to the continuous increase in the
demand for these tests, CT has become the diagnostic procedure that most contributes to the
increase in the dose absorbed by the population. The optimization of the image acquisition
process aimed at reducing the dose in patients and maintaining the diagnostic quality of the
image has become an object of research in recent years, mainly in pediatric applications. For
this work, Iive human chest phantoms representing different volumes of patients were made,
one in cylindrical shape and the other four oblong, two for adult and three for pediatric
patients. The objects are made of polymethylmethacrylate and have openings that allow the
measurement of absorbed dose values using a pencil-type ionization chamber. The CT scans of
the phantoms were performed on two devices using different acquisition protocols, always
starting from the routine chest protocol used by the diagnostic service. The tested protocols
used different voltage values (80, 100, 120, 135 and 140 kV) and from the test results, the best
acquisition protocol was deIined for each phantom in each CT device. The absorbed dose
values recorded using the optimized protocols generated considerably lower doses in patient
than those received with the routine protocol. In order to maintain the diagnostic quality of the
image, an analysis of the noise generated in the image of the central slice was made. The noise
value was kept below 1%. This noise index value is considered very good for homogeneous
materials, such as phantoms. The new optimized protocols were implemented and used in
patient scans and allowed to generate images with very good diagnostic quality.