Download - 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 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
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
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
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
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
haste – non FS
spair - FS
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
trufi
space - pelvis
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
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
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***
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
Deep ulcerations
Bowel wall thickening
> 3 mm abnormal Most patients in
crohn’s 5-10 mm
Marked wall thickening terminal ileum
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).
Mesenteric changes
TrueFISP Small mesenteric
lymph nodes Comb sign
Small lymph nodes seen in active and chronic disease
Enhancement LN suggest active disease
Mesenteric changes
T1 and true FISP – comb sign and creeping fat
Mesenteric changes
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
haste
haste
Post gad
Post gad
Ileal and appendix dz
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
Active vs Chronic
hastePost gad venous
Spair/haste FS
-enhancing abnl loop post gad
-no edema on spair
-thus FIBROTIC disease
Enhancement
Stratified enhancement (c,d) indicative of active disease.
Stratified Enhancement – active disease
Complications - strictures
Coronal images good for looking for strictures
> 3 cm bowel distention upstream indicates functional obstruction
Complications“Star sign” – internal fistula
HASTE
Post gad
Star sign of internal fistula
Patient had entero-entero fistula
Complications – perianal dz
HASTE
FS post gad
Fistula post gad
Complications – perianal fistula
spair Post gad
Complications – perianal fistula on T2 images
Complications – perianal abscess
Complications – phelgmon/abscess
trueFISPPost-gad
Medial wall of terminal ileum is partially indistinct and bulging medially suggesting phlegmon/early abscess.
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
Pitfalls
True FISP MR image shows extensive susceptibility artifacts generated by trapped endoluminal air
Susceptibility artifact Signal dropout Bright spots Spatial distortion
Pitfalls – artifacts
TruFISP HASTE
Arrowheads – black boundary
Arrow – susceptibility artifact from trapped air*curved arrow on both – TI thickening
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
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
Good resource
http://lakeside2007.rsna.org/#
Electronic posters and papers through RSNA website Lakeside Learning Center Radiographics password