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MR Enterography

MR Enterography. Inflammatory Bowel Disease. Why? What the clinician wants to know. Presence, localization, and extent of disease Complications – strictures, abscesses, fistulas Disease activity – active vs fibrotic. How to do it?. Patient prep

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MR Enterography

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  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 • ½ dose before study starts, ½ 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 ½ 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 haste – non FS spair - FS • 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 trufi space - pelvis • 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 ***Early disease with mucosal ulceration and nodularity is not well seen on MR***

  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 Marked wall thickening terminal ileum

  15. Bowel wall thickening Coronal 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).

  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 T1 and true FISP – comb sign and creeping fat

  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

  20. Ileal and appendix dz haste Post gad haste Post gad

  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 haste Post gad venous -enhancing abnl loop post gad -no edema on spair -thus FIBROTIC disease Spair/haste FS

  23. Enhancement Stratified enhancement (c,d) indicative of active disease.

  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 Post gad Star sign of internal fistula Patient had entero-entero fistula HASTE

  27. Complications – perianal dz HASTE Fistula post gad FS post gad

  28. Complications – perianal fistula spair Post gad

  29. Complications – perianal fistula on T2 images

  30. Complications – perianal abscess

  31. Complications – phelgmon/abscess Post-gad trueFISP Medial wall of terminal ileum is partially indistinct and bulging medially suggesting phlegmon/early 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 HASTE TruFISP Arrowheads – black boundary Arrow – susceptibility artifact from trapped air *curved arrow on both – TI thickening

  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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