MR Enterography
Inflammatory Bowel Disease
Why? What the clinician wants
to know
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Presence, localization, and extent of
disease
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Complications – strictures, abscesses,
fistulas
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Disease activity – active vs fibrotic
How to do it?
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Patient prep
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Bowel prep day before – low residue diet, fluids, laxative
Overnight fasting or NPO 4-6 hrs prior to study
Oral contrast
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Water results in inadequate distention, long transit time
Biphasic oral contrast agents
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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
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Can cause N/V, diarrhea, cramping
How to do it?
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Prone positioning
Glucagon IM or IV
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Timing –
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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
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to stop peristalsis
½ dose before study starts, ½ dose prior to contrast
not generally used unless incomplete colonoscopy
MR Entercolysis – improved bowel distention (esp jejunum)
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Invasive, time consuming
Egleston Protocol
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No patient prep
Oral contrast – Kool-aide with gastroview
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Powerade/gatorade cannot be used due to susceptibility artifact
Timing
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2 doses – first dose wait one hour, then drink ½ scan 30 minutes
later
Ex : 24/12
Volume and timing same as CT guidelines
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No glucagon
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Supine position
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Magnevist
Sequences
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T2w HASTE (haste, spair)
TrueFISP (trufi, space)
Post contrast
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Axial and coronal planes
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Coronal plane good for terminal ileum,
appy; good overview
Sagittal thru pelvis
haste – non FS
HASTE
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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
spair - FS
trufi
TrueFISP
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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
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Occurs in pixels with fat &
water
Improved with FS
space - pelvis
Post contrast VIBE & FLASH
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Venous, delayed for bowel (enteric phase at 75 sec post gad)
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VIBE 3D more motion sensitive
FLASH 2D, thicker slices, but relatively motion insensitive
(Shiran insurance plan)
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Combination of FS and low SI intraluminal contrast increase
the ability to detect wall enhancement
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Active vs fibrotic disease
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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
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Post gad T1 images are better for the
pelvis than the gradient echo (VIBE
and FLASH)
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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
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Transmural bowel wall thickening, thickened folds
Cobblestone
Submucosal Edema – use spair images; indicates active dz
Mesenteric changes
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Fat wrapping/creeping fat
Lymphadenopathy
Vascular hyperemia – comb sign
Complications
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Strictures
Fistulas
Abscess
***Early disease with mucosal ulceration
and nodularity is not well seen on MR***
Fold thickening & ulceration
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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
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> 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
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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
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Post contrast images
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Fibrosis – low level, mild to moderate
inhomogeneous enhancement
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Active disease – homogeneous intense
enhancement or stratified enhancement
Ileal and appendix dz
haste
Post gad
haste
Post gad
Active vs Chronic
Submucosal Edema
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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
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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
haste
Post gad venous
-enhancing abnl loop post gad
-no edema on spair
-thus FIBROTIC disease
Spair/haste FS
Enhancement
Stratified enhancement (c,d) indicative of active disease.
Stratified Enhancement –
active disease
Complications - strictures
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Coronal images good for looking for
strictures
> 3 cm bowel distention upstream
indicates functional obstruction
Complications
“Star sign” – internal fistula
Post gad
Star sign of internal fistula
HASTE
Patient had entero-entero
fistula
Complications – perianal dz
HASTE
Fistula post gad
FS post gad
Complications – perianal
fistula
spair
Post gad
Complications – perianal
fistula on T2 images
Complications – perianal
abscess
Complications –
phelgmon/abscess
trueFISP
Post-gad
Medial wall of terminal ileum is partially indistinct and
bulging medially suggesting phlegmon/early abscess.
Pitfalls
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Incomplete luminal distention
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Black border artifact on trueFISP can over
estimate wall thickness
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use HASTE for wall thickness
Intraluminal flow artifact on HASTE can
simulate cobblestone
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Can mimic bowel wall thickening
Check TrueFISP
Fistula can be missed since not dynamic
Pitfalls
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True FISP MR image
shows extensive
susceptibility artifacts
generated by trapped
endoluminal air
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Susceptibility artifact
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Signal dropout
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Bright spots
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Spatial distortion
Pitfalls – artifacts
TruFISP
Arrowheads – black boundary
Arrow – susceptibility artifact from trapped air
HASTE
*curved arrow on both – TI
thickening
Summary
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Haste, trufi and post contrast images to identify
abnormal bowel
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Look for associated mesenteric changes
Active vs fibrotic
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Coronal images good for terminal ileum, overall picture
Evaluate for strictures
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
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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
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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
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Darge K, Anupindi S, Jaramillo D. MR Imaging of the Bowel: Pediatric
Applications. MRI Clinics N America.2008;16(3):467-478
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Toma P, Granata C, Magnano G, Barabino A. CT and MRI of paediatric Crohn
disease. Pediatr Radiol. 2007;37:1065-1189.
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Greenhalgh R, Punwani S, Austin C; Halligan S, Taylor S. The MRI
manifestations of small bowel Crohn’s disease revealed. Presented at RSNA
2007.
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Udayasankar U, Lauenstein T, Martin D. Role of SPAIR T2 fat suppressed MR
imaging in active inflammatory bowel disease. Presented at RSNA 2007.
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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
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http://lakeside2007.rsna.org/#
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Electronic posters and papers through
RSNA website
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Lakeside Learning Center
Radiographics password
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