Model-Based Iterative Reconstruction in CT Enterography

OBJECTIVE. The purpose of this study was to analyze the performance of pure model-based iterative reconstruction (MBIR) in low-dose CT enterography. SUBJECTS AND METHODS. Forty-four patients with Crohn disease referred for CT enterography were included. Low-dose modified-protocol and conventional-protocol CT datasets were contemporaneously acquired. Conventional-protocol image formation was performed with 40% adaptive statistical iterative reconstruction (ASIR). Modified-protocol data were reconstructed with 100% MBIR and 40% ASIR. Image quality was assessed subjectively and objectively at six levels. Independent clinical interpretations by two fully blinded radiologists were compared with reference standard consensus reviews by two nonblinded readers who had access to clinical information, previous imaging studies, and medical records. RESULTS. A 74.7% average radiation dose reduction was seen: low-dose modified-protocol effective dose, 1.61 +/- 1.18 mSv (size-specific-dose-estimate, 2.47 +/- 1.21 mGy); conventional-protocol effective dose, 6.05 +/- 2.84 mSv (size-specific-dose-estimate, 9.25 +/- 2.9 mGy). Image quality assessment yielded 9372 data points. Objective noise on modified-protocol MBIR images was superior (p < 0.05) to that with the conventional protocol at three of six levels and comparable at the other three levels. Modified-protocol images were superior to conventional-protocol ASIR images (p < 0.05 in all cases) for subjective noise, spatial resolution, contrast resolution, streak artifact, and diagnostic acceptability on coronal reconstructions. Axial diagnostic acceptability was superior for conventional-protocol ASIR (p = 0.76). For both readers, modified-protocol MBIR clinical readings agreed more closely with reference standard readings than did conventional-protocol ASIR readings with regard to bowel wall disease assessment (kappa = 0.589 and 0.700 vs 0.583 and 0.564). Overall Crohn disease activity grade (kappa = 0.549 and 0.441 vs 0.315 and 0.596) and detection of acute complications (kappa = 1.0 and 0.689 vs 0.896 and 0.896) were comparable when evaluated on conventional-protocol ASIR and modified-protocol MBIR images. CONCLUSION. Low-dose CT enterography with MBIR yields images that are comparable to or superior to conventional images.