The Impact of Scan Length on the Exposure Levels in 16- and 64-Row Multidetector Computed Tomography

Lower effective doses are obtained in 64-row MDCT compared to 16-row MDCT (0.5-mm slice thickness) provided that scan length exceeds 12.3, 30, and 25 cm, for 16-row MDCT slice thickness of 0.5, 1, and 2 mm, respectively. Reduced effective dosage in 64-row MDCT compared to 16-row MDCT has not been demonstrated before. Differences in object size may thus explain discrepancies between previous studies with regard to the exposure levels at 64-slice CT compared to 16-slice CT.