Purpose: Although several approaches have been already used to
reduce radiation dose, CT doses are still among the high doses in
radio-diagnostic. Recently, General Electric introduced a new imaging
reconstruction technique, adaptive statistical iterative reconstruction
(ASIR), allows to taking into account the statistical fluctuation of noise.
The benefits of ASIR method were assessed through classic metrics
and the evaluations of cardiac structures by radiologists.
Methods and materials: A 64-row CT (MDCT) was employed.
Catphan600 phantom acquisitions and 10 routine-dose CT
examinations performed at 80 kVp were reconstructed with FBP and
with 50% of ASIR. Six radiologists then assessed the visibility of main
cardiac structures using the visual grading analysis (VGA) method.
Results: On phantoms, for a constant value of SD (25 HU), CTDIvol is
divided by 2 (8 mGy to 4 mGy) when 50% of ASIR is used. At constant
CTDIvol, MTF medium frequencies were also significantly improved.
First results indicated that clinical images reconstructed with ASIR had
a better overall image quality compared with conventional
reconstruction. This means that at constant image quality the radiation
dose can be strongly reduced.
Conclusion: The first results of this study shown that the ASIR method
improves the image quality on phantoms by decreasing noise and
improving resolution with respect to the classical one. Moreover, the
benefit obtained is higher at lower doses. In clinical environment, a dose
reduction can still be expected on 80 kVp low dose pediatric protocols
using 50% of iterative reconstruction. Best ASIR percentage as a
function of cardiac structures and detailed protocols will be presented
for cardiac examinations.