MR Enterography

1. MR Enterography Inflammatory Bowel Disease

2. Why? What the clinician wants to know Presence, localization, and extent of disease Complications � strictures, abscesses, fistulas Disease activity � active vs fibrotic

3. How to do it? Patient prep Bowel prep day before � low residue diet, fluids, laxative Overnight fasting or NPO 4-6 hrs prior to study Oral contrast Water results in inadequate distention, long transit time Biphasic oral contrast agents Different 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 water Can cause N/V, diarrhea, cramping

4. How to do it? Prone positioning Glucagon IM or IV to stop peristalsis � dose before study starts, � dose prior to contrast Timing � Typical adult 1-1.5 L over 45-90 min Child 1 L one hour prior to exam Filling of TI occurs in kids at 20-25 minutes, adults 1 hour Rectal contrast � water enema for better distention of colon, TI not generally used unless incomplete colonoscopy MR Entercolysis � improved bowel distention (esp jejunum) Invasive, time consuming

5. Egleston Protocol No patient prep Oral contrast � Kool-aide with gastroview Powerade/gatorade cannot be used due to susceptibility artifact Timing 2 doses � first dose wait one hour, then drink � scan 30 minutes later Ex : 24/12 Volume and timing same as CT guidelines No glucagon Supine position Magnevist

6. Sequences T2w HASTE (haste, spair) TrueFISP (trufi, space) Post contrast Axial and coronal planes Coronal plane good for terminal ileum, appy; good overview Sagittal thru pelvis

7. HASTE Fast High contrast between bowel lumen and wall Best sequence for determining bowel wall thickness Fluid collections Submucosal edema (spair) Sensitive to intraluminal flow voids Poor evaluation of mesentery

8. TrueFISP Fast Relatively motion insensitive High contrast between small bowel lumen and bowel walls Homogeneous endoluminal opacification Good mesenteric anatomy (LAN, comb sign, vessels) Susceptibility artifacts from intraluminal air Chemical shift artifacts � black boundary Occurs in pixels with fat & water Improved with FS

9. Post contrast VIBE & FLASH Venous, delayed for bowel (enteric phase at 75 sec post gad) VIBE 3D more motion sensitive FLASH 2D, thicker slices, but relatively motion insensitive (Shiran insurance plan) Combination of FS and low SI intraluminal contrast increase the ability to detect wall enhancement Active vs fibrotic disease Bowel wall enhancement in active disease and fibrotic disease Stratification can indicate active disease Enhancing mesenteric adenopathy � sign of active disease Complications � fistulas, abscess best seen post gad

10. Pelvis � 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 images Motion is not usually a big issue in pelvis

11. MR Features IBD Transmural bowel wall thickening, thickened folds Cobblestone Submucosal Edema � use spair images; indicates active dz Mesenteric changes Fat wrapping/creeping fat Lymphadenopathy Vascular hyperemia � comb sign Complications Strictures Fistulas Abscess

12. Fold thickening & ulceration Deep ulcerations � focal linear areas of high SI through thickened bowel wall Normal bowel wall and folds are low SI on both the true FISP and HASTE images

13. Deep ulcerations

14. Bowel wall thickening > 3 mm abnormal Most patients in crohn�s 5-10 mm

15. Bowel wall thickening

16. Mesenteric changes TrueFISP Small mesenteric lymph nodes Comb sign Small lymph nodes seen in active and chronic disease Enhancement LN suggest active disease

17. Mesenteric changes

18. Mesenteric changes

19. Active vs. Chronic post contrast images Post contrast images Fibrosis � low level, mild to moderate inhomogeneous enhancement Active disease � homogeneous intense enhancement or stratified enhancement

21. Active vs ChronicSubmucosal Edema D. Martin RSNA 2007 TI post gad very sensitive for detection of IBD but spair better for determining active vs chronic Submucosal edema classic finding in active inflammation Use spair images (haste fs) to detect submucosal edema Study found many false positives for post gad T2 images better correlated with active vs inactive disease

22. Active vs Chronic

23. Enhancement

24. Stratified Enhancement � active disease

25. Complications - strictures Coronal images good for looking for strictures > 3 cm bowel distention upstream indicates functional obstruction

26. Complications �Star sign� � internal fistula

27. Complications � perianal dz

28. Complications � perianal fistula

29. Complications � perianal fistula on T2 images

30. Complications � perianal abscess

31. Complications � phelgmon/abscess

32. Pitfalls Incomplete luminal distention Can mimic bowel wall thickening Black border artifact on trueFISP can over estimate wall thickness use HASTE for wall thickness Intraluminal flow artifact on HASTE can simulate cobblestone Check TrueFISP Fistula can be missed since not dynamic

33. Pitfalls True FISP MR image shows extensive susceptibility artifacts generated by trapped endoluminal air Susceptibility artifact Signal dropout Bright spots Spatial distortion

34. Pitfalls � artifacts

35. Summary Haste, trufi and post contrast images to identify abnormal bowel Coronal images good for terminal ileum, overall picture Evaluate for strictures Look for associated mesenteric changes Active vs fibrotic Haste vs spair ?submucosal edema Stratification of edema post contrast Use space, T1 post gad high res images to look for perianal disease Post contrast images for fistula, abscess

36. References Prassopoulos P, Papanikolaou N, Grammatikakis J, Rousomoustakaki M, Maris T, Gourtsoyiannis N. MR enteroclysis imaging of Crohn disease. RadioGraphics 2001;21(Spec Issue):S161�S172 Essary B, Kim J, Anupindi S, et al. Pelvic MRI in children with Crohn disease and suspected perianal involvement. Pediatr Radiol. 2007;37:201�208 Darge K, Anupindi S, Jaramillo D. MR Imaging of the Bowel: Pediatric Applications. MRI Clinics N America.2008;16(3):467-478 Toma P, Granata C, Magnano G, Barabino A. CT and MRI of paediatric Crohn disease. Pediatr Radiol. 2007;37:1065-1189. Greenhalgh R, Punwani S, Austin C; Halligan S, Taylor S. The MRI manifestations of small bowel Crohn�s disease revealed. Presented at RSNA 2007. Udayasankar 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

37. Good resource http://lakeside2007.rsna.org/# Electronic posters and papers through RSNA website Lakeside Learning Center Radiographics password

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