Noise comparison in optimized head CT protocols using two phantoms

Computed tomography has been widely used in radiological imaging diagnostics, but it generates higher doses of radiation in patients. The growth in demand for tomography exams has generated concern from the scientific community in increasing the population dose generated by this technique. For this reason, there is a concern to reduce the absorbed dose generated by the exam and maintain the diagnostic quality of the medical image. In this work, two head phantoms, one cylindrical made of PMMA and another Alderson's anthropomorphic, were used for tests on a CT scanner Ge, light Speed VCT model of 64-channel. Different acquisition protocols were tested in order to observe the brain structure region. Measurements of CTDI_vol values using a pencil ionization chamber were performed on the PMMA phantom in order to define the lowest dose protocols. The selected protocols were applied in helical scans of the phantoms and the image noise, in the cerebral region, of the central slice was calculated. For each protocol, the noise between the phantoms was compared. The study showed a reduction of up to 82.7% in the dose between the suggested new acquisition protocol and routine protocol obtaining a noise value close to 1%. (Author)