3.1\ Introduction

Unlike the upper and lower gastrointestinal tract, the diagnostic access to the small bowel is not as easy. Therefore, it is of utmost importance to find a diagnostic tool to evaluate this more “hidden” gastrointestinal part with high sensitivity and specificity. Indeed, capsule endoscopy is now available for diagnosing the small bowel, but this tool is cost-intensive and there are certain contraindications, especially bowel strictures or obstruction [1]. Furthermore, capsule endoscopy only allows visualization of the surface, which is the mucosal layer, and deeper tissues cannot be evaluated, not to mention the surrounding tissues and other abdominal organs. Over the past years, cross-sectional imaging techniques like computed tomography (CT) and magnetic resonance imaging (MRI) have evolved considerably and changed the diagnostic approach of the small bowel. Both techniques are now optimized for small bowel imaging and play a more and more increasing role in the diagnosis of small bowel pathologies. CT is burdened with a still not negligible amount of radiation exposure, which is especially of importance for patients who are to undergo multiple examinations during their life due to the recurrent character of their underlying disease. As a result, MR imaging has become an increasingly used diagnostic tool and nowadays is an important imaging modality for evaluating small bowel pathologies. Besides the already in-place sequences like balanced steady state free precession, T2-weighted images with and without fat saturation and T1-weighted images unenhanced and dynamically acquired after the injection of a gadolinium-based contrast agent, diffusion-weighted imaging (DWI) has gained more and more importance in the last decade within the MR imaging protocol of the small bowel [2]. As DWI relies on the diffusion of water in tissue and

S. Kinner

Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany

e-mail: sonja.kinner@uk-essen.de

S. Gourtsoyianni, N. Papanikolaou (eds.), Diffusion Weighted Imaging of the Gastrointestinal Tract, https://doi.org/10.1007/978-3-319-92819-7_3