Low-Dose MDCT and CT Enterography of Patients With Crohn Disease: Feasibility of Adaptive Statistical Iterative Reconstruction

The purpose of this study was to evaluate the image quality and diagnostic performance of low-dose MDCT and CT enterography with adaptive statistical iterative reconstruction (ASIR) in the evaluation of Crohn disease.Forty-eight patients (20 men, 28 women; mean age, 33.3 years; range, 17-83 years) with known or suspected Crohn disease who underwent low-dose MDCT and CT enterography with ASIR between December 2008 and December 2009 were included in the study. Twenty-seven patients had previously undergone standard-dose 64-MDCT and CT enterography with filtered back projection (FBP), and those images were used for comparison. The weight-based i.v. contrast protocol and scan parameters (120 kVp, 5-mm section thickness, 0.5-second rotation, pitch of 1.375, 64 × 0.625 mm detector configuration) were constant for the two techniques except for a higher noise index (×1.3) in the ASIR group. Two blinded readers reviewed 75 randomized MDCT-CT enterographic scans of 48 patients to assess image quality and diagnostic performance in the evaluation of Crohn disease, and the radiation dose for the studies was estimated.All 75 MDCT and CT enterographic scans had acceptable quality for diagnostic interpretation. Findings of Crohn disease were seen on 63 of 75 scans (84%). Low-dose scans in the ASIR group had optimal image quality and were rated comparable to or better than standard-dose FBP images (mean score, 4.2 vs 3.87; p = 0.007). The subjective image noise score (mean, 1.43 vs 1.58; p = 0.2) and objective image noise measurements were lower for ASIR images (p < 0.001). Low-dose studies with ASIR allowed average dose reduction of 34.5% compared with standard-dose scans with FBP (volume CT dose index for ASIR, 7.7 ± 2.1 mGy; for FBP, 12 ± 5.5 mGy; p < 0.01).Low-dose MDCT and CT enterographic studies reconstructed with ASIR were of appropriate quality for confident evaluation of the manifestations of Crohn disease while allowing approximately 34% dose reduction in comparison with FBP technique.