Our purpose in this study was to evaluate the image quality of low-radiation-dose CT using hybrid iterative reconstruction (HIR), and to compare the results with those of filtered back projection (FBP) at routine doses. We measured the mean values and standard deviation of the CT numbers within and outside a 15-mm low-contrast object cylinder at 1.0 % contrast level. The noise reduction levels of the HIR were 1 (weak) to 7 (strong). Visual inspection of the low-contrast detectability was done by six radiologic technologists. The low-contrast detectability of the cylinder at the 1.0 % contrast level with HIR at all mAs levels was equal to that obtained with FBP, and thus the use of HIR did not result in any improvement of low-contrast detectability.
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