Adaptive Statistical Iterative Reconstruction (ASIR) is a new imaging reconstruction technique recently introduced by
General Electric (GE). This technique, when combined with a conventional filtered back-projection (FBP) approach, is
able to improve the image noise reduction. To quantify the benefits provided on the image quality and the dose reduction
by the ASIR method with respect to the pure FBP one, the standard deviation (SD), the modulation transfer function
(MTF), the noise power spectrum (NPS), the image uniformity and the noise homogeneity were examined.
Measurements were performed on a control quality phantom when varying the CT dose index (CTDIvol) and the
reconstruction kernels. A 64-MDCT was employed and raw data were reconstructed with different percentages of ASIR
on a CT console dedicated for ASIR reconstruction. Three radiologists also assessed a cardiac pediatric exam
reconstructed with different ASIR percentages using the visual grading analysis (VGA) method. For the standard, soft
and bone reconstruction kernels, the SD is reduced when the ASIR percentage increases up to 100% with a higher
benefit for low CTDIvol. MTF medium frequencies were slightly enhanced and modifications of the NPS shape curve
were observed. However for the pediatric cardiac CT exam, VGA scores indicate an upper limit of the ASIR benefit.
40% of ASIR was observed as the best trade-off between noise reduction and clinical realism of organ images. Using
phantom results, 40% of ASIR corresponded to an estimated dose reduction of 30% under pediatric cardiac protocol
conditions. In spite of this discrepancy between phantom and clinical results, the ASIR method is as an important option
when considering the reduction of radiation dose, especially for pediatric patients.