Characteristic bowel-wall changes suggesting active inflammation include bowel-wall thickening, high T2 mural signal, mural hyper enhancement with mural stratification, and hyperemic vasa recta [55-64]. MR cine imaging is potentially useful, allowing for assessment of decreased bowel motility in the affected segments with CD [65]. Besides inflammation, MRI can detect complications for CD including obstruction, abscess, or fistula. Test performance characteristics for complications are similar to CT enterography [27,28,35,40,68,69]. MR enterography has been shown to correlate with response to therapy and mucosal healing [111,112]. One prospective multicenter study (n = 48) showed 90% accuracy of ulcer healing determination at MR enterography, utilizing ileocolonoscopy as the reference standard [113]. In addition, MR is able to utilize natural tissue contrast at T2W imaging to help in the determination between active inflammation and fibrosis, which is not possible with CT-based modalities. DWI, magnetization transfer imaging, and cine sequences at MR enterography can also be helpful. [111]. MR enterography without IV contrast has been investigated because of emerging concerns with IV gadolinium use and potential long-term accumulation in the body and brain. Noncontrast techniques such as DWI have been used to evaluate evidence for CD. There is growing literature examining its promise in detecting active disease versus quiescent disease for complication evaluation and disease monitoring [77]. Overall, DWI appears to have moderate sensitivity but low specificity, leading to increased false positives for disease activity [77]. Thus, the current consensus is that noncontrast only techniques such as DWI can be done but there is likely improved performance with the information gained from post IV contrast series.
Crohn Disease. Characteristic bowel-wall changes suggesting active inflammation include bowel-wall thickening, high T2 mural signal, mural hyper enhancement with mural stratification, and hyperemic vasa recta [55-64]. MR cine imaging is potentially useful, allowing for assessment of decreased bowel motility in the affected segments with CD [65]. Besides inflammation, MRI can detect complications for CD including obstruction, abscess, or fistula. Test performance characteristics for complications are similar to CT enterography [27,28,35,40,68,69]. MR enterography has been shown to correlate with response to therapy and mucosal healing [111,112]. One prospective multicenter study (n = 48) showed 90% accuracy of ulcer healing determination at MR enterography, utilizing ileocolonoscopy as the reference standard [113]. In addition, MR is able to utilize natural tissue contrast at T2W imaging to help in the determination between active inflammation and fibrosis, which is not possible with CT-based modalities. DWI, magnetization transfer imaging, and cine sequences at MR enterography can also be helpful. [111]. MR enterography without IV contrast has been investigated because of emerging concerns with IV gadolinium use and potential long-term accumulation in the body and brain. Noncontrast techniques such as DWI have been used to evaluate evidence for CD. There is growing literature examining its promise in detecting active disease versus quiescent disease for complication evaluation and disease monitoring [77]. Overall, DWI appears to have moderate sensitivity but low specificity, leading to increased false positives for disease activity [77]. Thus, the current consensus is that noncontrast only techniques such as DWI can be done but there is likely improved performance with the information gained from post IV contrast series.