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

OBJECTIVE: 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. SUBJECTS AND METHODS: 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. RESULTS: 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). CONCLUSION: 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.