OPTIMIZATION OF PARAMETERS IN 16-SLICE CT-SCAN PROTOCOLS FOR REDUCTION OF THE ABSORBED DOSE

In this study, the brain, abdomen, and thorax scaning was performed using Toshiba 16-slice scannerand standard AAPM and CTDI phantoms. AAPM phantom was used for the measurement of image-related parameters and CTDI phantom was utilized for the calculation of absorbed dose to patients. Imaging parameters including mA (50-400 mA), pitch factor (1 and 1.5) and rotation time (range of 0.5, 0.75, 1, 1.5 and 2 seconds) were considered as independent variables. The brain, abdomen and chest imaging was performed multi-slice and spiral modes. Changes in image quality parameters including contrast resolution (CR) and spatial resolution (SR) in each condition were measured and determined by MATLAB software. Results After normalizing data by plotting the full width at half maximum (FWHM) of point spread function (PSF) in each condition, it was observed that image quality was not noticeably affected by each cases. Therefore, in brain scan, the lowest patient dose was in 150 mA and rotation time of 1.5 seconds. Based on results of scanning of the abdomen and chest, the lowest patient dose was obtained by 011 mA and pitch factors of 1 and 1.5. Conclusion