Technical Challenges and Clinical Applications of Magnetic Resonance Enteroclysis Nickolas Papanikolaou, M.Sc., Panos Prassopoulos, M.D., Ioannis Grammatikakis, M.D., Thomas Maris, Ph.D., and Nicholas C. Gourtsoyiannis, M.D. Summary: With the advent of gradient systems the image quality of ultrafast pulse sequences, i.e., half Fourier acquisition single shot turbo spin echo (HASTE), true fast imaging with steady-state processing and fast low angle shot (FLASH), improved sub- stantially and clinical applications including small bowel imaging became feasible. Within this context, magnetic resonance enteroclysis was developed as a comprehensive examination of the small bowel, providing luminal, transmural, and exoenteric diagnos- tic information of small bowel abnormalities. Clinical applications of magnetic reso- nance enteroclysis include diagnostic evaluation and follow-up of patients with inflam- matory or neoplastic diseases and small bowel obstruction. Key Words: Ultrafast MRI—True FISP—Enteroclysis—Crohn’s disease. SMALL BOWEL IMAGING TECHNIQUES Enteroclysis is well established for imaging evaluation of the small intestine, with an overall sensitivity of 93.1% and specificity of 96.9% in small bowel diseases (1,2). Distension of the entire small bowel lumen by barium contrast medium favors a detailed anatomic demonstration and identification of morphologic and functional abnor- malities. However, its inability to demonstrate extraintes- tinal pathology associated with small bowel diseases is the main limitation of the method. Cross-sectional imaging techniques may overcome this deficit and can be considered complementary to conven- tional enteroclysis in the radiologic evaluation of the small bowel. Computed tomography (CT) has been mainly used for evaluation of mural and extramural lesions and assess- ment of exoenteric manifestations of inflammatory or neo- plastic small intestinal diseases (3). In addition, when combined with duodenal intubation, CT enteroclysis (4) shares advantages of both conventional enteroclysis and cross-sectional imaging. The main clinical applications of CT enteroclysis, although based on limited prospective data, may include intestinal obstruction, known or sus- pected malignancy, and assessment of Crohn’s disease complications (5). Advances in CT technology, mainly with the introduction of multidetector systems, may fur- ther increase the role of CT in small bowel imaging (6). However, poor soft-tissue contrast inherent to CT, radia- tion exposure that may further increase in case of mul- tidetector CT examinations, and acquisition of axial slices only when single-slice CT scanners are used are inherent limitations of the method. Many investigators have assessed the potential of mag- netic resonance imaging (MRI) in examining the small bowel (7–16). This method possesses several virtues, in- cluding superb soft-tissue contrast, absence of radiation exposure, cross-sectional and projectional imaging capa- bilities in all three dimensions, and multiple contrast sources, which may favor a comprehensive morphologic and functional evaluation of the small bowel. Initially, the long acquisition times of conventional spin-echo se- quences in combination with intrinsic physiologic motion resulted in artifacts that hampered the diagnostic capabil- ity of MRI in the small bowel. Development of high- performance gradient and radiofrequency systems resulted in vast improvement of the image quality of fast pulse sequences that were not clinically acceptable in the past. High-resolution images of the entire small bowel free Departments of Radiology (N.P., P.P., I.G., N.C.G.) and Medical Physics (T.M.), University Hospital of Iraklion, University of Crete Medical School, Iraklion Crete, Greece. Address correspondence and reprint requests to Nickolas Papanikolaou, M.Sc., Department of Radiology, University Hospital of Iraklion P.O. Box 1352, 711 10 Iraklion Crete, Greece, or npapan@med.uoc.gr Topics in Magnetic Resonance Imaging 13(6): 397–408 © 2002 Lippincott Williams & Wilkins, Inc., Philadelphia 397