2Why? What the clinician wants to know Presence, localization, and extent of diseaseComplications – strictures, abscesses, fistulasDisease activity – active vs fibrotic
3How to do it? Patient prep Oral contrast Bowel prep day before – low residue diet, fluids, laxativeOvernight fasting or NPO 4-6 hrs prior to studyOral contrastWater results in inadequate distention, long transit timeBiphasic oral contrast agentsDifferent signal intensities on different sequences (low T1, bright T2)VoLumen - a low-conc barium (0.1% weight/volume) that contains sorbitol (CHOP, Emory 2007)Mannitol, sorbitol and polyethylene glycol have been used to slow down intestinal reabsorption of waterCan cause N/V, diarrhea, cramping
4How to do it? Prone positioning Glucagon IM or IV Timing – to stop peristalsis½ dose before study starts, ½ dose prior to contrastTiming –Typical adult L over minChild 1 L one hour prior to examFilling of TI occurs in kids at minutes, adults 1 hourRectal contrast – water enema for better distention of colon, TInot generally used unless incomplete colonoscopyMR Entercolysis – improved bowel distention (esp jejunum)Invasive, time consuming
5Egleston Protocol No patient prep Oral contrast – Kool-aide with gastroviewPowerade/gatorade cannot be used due to susceptibility artifactTiming2 doses – first dose wait one hour, then drink ½ scan 30 minutes laterEx : 24/12Volume and timing same as CT guidelinesNo glucagonSupine positionMagnevist
6Sequences T2w HASTE (haste, spair) TrueFISP (trufi, space) Post contrastAxial and coronal planesCoronal plane good for terminal ileum, appy; good overviewSagittal thru pelvis
7HASTE haste – non FS spair - FS Fast High contrast between bowel lumen and wallBest sequence for determining bowel wall thicknessFluid collectionsSubmucosal edema (spair)Sensitive to intraluminal flow voidsPoor evaluation of mesentery
8TrueFISP trufi space - pelvis Fast Relatively motion insensitive High contrast between small bowel lumen and bowel wallsHomogeneous endoluminal opacificationGood mesenteric anatomy (LAN, comb sign, vessels)Susceptibility artifacts from intraluminal airChemical shift artifacts – black boundaryOccurs in pixels with fat & waterImproved with FS
9Post contrast VIBE & FLASH Venous, delayed for bowel (enteric phase at 75 sec post gad)VIBE 3D more motion sensitiveFLASH 2D, thicker slices, but relatively motion insensitive (Shiran insurance plan)Combination of FS and low SI intraluminal contrast increase the ability to detect wall enhancementActive vs fibrotic diseaseBowel wall enhancement in active disease and fibrotic diseaseStratification can indicate active diseaseEnhancing mesenteric adenopathy – sign of active diseaseComplications – fistulas, abscess best seen post gad
10Pelvis – T1 axial FS, high res Post gad T1 images are better for the pelvis than the gradient echo (VIBE and FLASH)Gas/stool in rectum degrade images thru the pelvis due to susceptibility artifact on the gradient echo imagesMotion is not usually a big issue in pelvis
11MR Features IBD Transmural bowel wall thickening, thickened folds CobblestoneSubmucosal Edema – use spair images; indicates active dzMesenteric changesFat wrapping/creeping fatLymphadenopathyVascular hyperemia – comb signComplicationsStricturesFistulasAbscess***Early disease with mucosal ulceration and nodularity is not well seen on MR***
12Fold thickening & ulceration Deep ulcerations – focal linear areas of high SI through thickened bowel wallNormal bowel wall and folds are low SI on both the true FISP and HASTE images
14Bowel wall thickening > 3 mm abnormal Most patients in crohn’s 5-10 mmMarked wall thickening terminal ileum
15Bowel wall thickeningCoronal true-FISP (A) and axial HASTE (B) images shows polypoid thickening of the cecal wall (arrows). Compare this with the normal wall thickness of the descending colon (arrowhead).
16Mesenteric changes TrueFISP Small mesenteric lymph nodes Comb sign Small lymph nodes seen in active and chronic diseaseEnhancement LN suggest active disease
17Mesenteric changesT1 and true FISP – comb sign and creeping fat
21Active vs Chronic Submucosal Edema D. Martin RSNA 2007TI post gad very sensitive for detection of IBD but spair better for determining active vs chronicSubmucosal edema classic finding in active inflammationUse spair images (haste fs) to detect submucosal edemaStudy found many false positives for post gadT2 images better correlated with active vs inactive disease
22Active vs Chronic haste Post gad venous -enhancing abnl loop post gad -no edema on spair-thus FIBROTIC diseaseSpair/haste FS
23EnhancementStratified enhancement (c,d) indicative of active disease.
31Complications – phelgmon/abscess Post-gadtrueFISPMedial wall of terminal ileum is partially indistinct and bulging medially suggesting phlegmon/early abscess.
32Pitfalls Incomplete luminal distention Can mimic bowel wall thickeningBlack border artifact on trueFISP can over estimate wall thicknessuse HASTE for wall thicknessIntraluminal flow artifact on HASTE can simulate cobblestoneCheck TrueFISPFistula can be missed since not dynamic
34Pitfalls – artifacts HASTE TruFISP Arrowheads – black boundary Arrow – susceptibility artifact from trapped air*curved arrow on both – TI thickening
35SummaryHaste, trufi and post contrast images to identify abnormal bowelCoronal images good for terminal ileum, overall pictureEvaluate for stricturesLook for associated mesenteric changesActive vs fibroticHaste vs spair ?submucosal edemaStratification of edema post contrastUse space, T1 post gad high res images to look for perianal diseasePost contrast images for fistula, abscess
36ReferencesPrassopoulos P, Papanikolaou N, Grammatikakis J, Rousomoustakaki M, Maris T, Gourtsoyiannis N. MR enteroclysis imaging of Crohn disease. RadioGraphics 2001;21(Spec Issue):S161–S172Essary B, Kim J, Anupindi S, et al. Pelvic MRI in children with Crohn disease and suspected perianal involvement. Pediatr Radiol. 2007;37:201–208Darge K, Anupindi S, Jaramillo D. MR Imaging of the Bowel: Pediatric Applications. MRI Clinics N America.2008;16(3):Toma P, Granata C, Magnano G, Barabino A. CT and MRI of paediatric Crohn disease. Pediatr Radiol. 2007;37:Greenhalgh R, Punwani S, Austin C; Halligan S, Taylor S. The MRI manifestations of small bowel Crohn’s disease revealed. Presented at RSNAUdayasankar U, Lauenstein T, Martin D. Role of SPAIR T2 fat suppressed MR imaging in active inflammatory bowel disease. Presented at RSNA 2007.Herrmann K, Michaely H, Seiderer J, et al. The “star-sign” in magnetic resonance enteroclysis: a characteristic finding of internal fistulae in Crohn's disease. Scand J Gastroenterol. 2006;41:239–241
37Good resource http://lakeside2007.rsna.org/# Electronic posters and papers through RSNA websiteLakeside Learning CenterRadiographics password