MRI of the Small Bowel in Patients with Crohn's Disease

Ellen M. Zimmermann; Mahmoud M. Al-Hawary

Disclosures

Curr Opin Gastroenterol. 2011;27(2):132-138. 

In This Article

Abstract and Introduction

Abstract

Purpose of review To highlight the advances in MRI of the small intestine in patients with Crohn's disease. MRI of the gut has become more feasible with improved spatial resolution and speed of the MR sequences allowing parallel evaluation for both disease activity and extra-enteric complications.
Recent findings Recent literature highlights excellent diagnostic accuracy of MR enterography (MRE) that is comparable to computed tomography enterography (CTE). Compared to CTE the image quality is not quite as good, and there is slightly more interobserver variability in interpretation. Despite these performance characteristics, the overall diagnostic yield of MRE is comparable to CTE. The lack of radiation exposure related to MRE is a significant strength, especially in Crohn's population that by virtue of their younger age, body habitus and potential need for repeated imaging, is at highest risk of potential cancer from radiation exposure due to diagnostic imaging. MRE should not be viewed as a 'safer' version of a CTE. The physics of MRI allows the application of unique sequences that add novel insights not possible with other imaging modalities.
Summary MRE is a highly effective technique for assessing Crohn's disease. We are only starting to explore new MRI sequences and the future of this technology is extremely exciting.

Introduction

Mucosal healing is becoming the standard for assessing therapeutic benefit in Crohn's disease replacing composite clinical measures such as Crohn's disease activity index. Endoscopic evaluation and radiographic imaging are the two techniques currently at our disposal for assessing the mucosa of the gut. The various endoscopic and radiographic techniques are complementary and are best applied with a clear understanding of the goals of the evaluation with consideration of the strengths and weaknesses of each technique. Because of its broad availability and high spatial resolution, computed tomography (CT)-based imaging, especially CT enterography (CTE), has become the most widely used cross-sectional imaging technology for Crohn's disease and has nearly completely replaced small-bowel follow-through at many centers.[1,2] CTE has become the 'gold standard' to which other radiographic imaging techniques are compared. Growing concern and increased awareness about the potential risks associated with the cumulative radiation exposure, particularly in young patients, have led to growing interest in alternative imaging modalities.[3] At the same time, improved spatial resolution of magnetic resonance (MR)-based techniques, along with more effective methods to deal with bowel motion and improved technique availability, have driven a rapid increase in the use of MR enterography (MRE) for Crohn's imaging. Some consider MRI-based imaging, specifically MRE and pelvic MRI, the primary modalities for cross-sectional imaging in Crohn's disease. However, technical limitations and practical considerations such as patients' acceptance, availability, and cost have caused others to choose CT over MRI for all but specific circumstances. In the past year the advances in MRI technology for assessing Crohn's disease have centered around two areas: comparing MRE to other diagnostic imaging techniques to assess test characteristics including interobserver and intermodality agreement, sensitivity and specificity; and assessing the usefulness of specific sequences such as diffusion and magnetization transfer that are unique to MRI and may offer novel insight into Crohn's not available with other technologies. These studies have added to the mounting academic research validating the appropriateness of using the radiation-free MR technique to answer important clinical questions in the management of patients with Crohn's disease.

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