MR Enterography

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MR Enterography

• Inflammatory Bowel Disease

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Why? What the clinician wants to know

• Presence, localization, and extent of disease
• Complications strictures, abscesses, fistulas
• Disease activity active vs fibrotic

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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

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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

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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

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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

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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

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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

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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

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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

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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
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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

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Deep ulcerations
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Bowel wall thickening

• gt 3 mm abnormal
• Most patients in crohns 5-10 mm

Marked wall thickening terminal ileum
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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).
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Mesenteric changes

• TrueFISP
• Small mesenteric lymph nodes
• Comb sign
• Small lymph nodes seen in active and chronic
  disease
• Enhancement LN suggest active disease

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Mesenteric changes
T1 and true FISP comb sign and creeping fat
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Mesenteric changes
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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

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Ileal and appendix dz
haste
Post gad
haste
Post gad
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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

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Active vs Chronic
haste
Post gad venous
-enhancing abnl loop post gad -no edema on
spair -thus FIBROTIC disease
Spair/haste FS
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Enhancement
Stratified enhancement (c,d) indicative of active
disease.
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Stratified Enhancement active disease
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Complications - strictures

• Coronal images good for looking for strictures
• gt 3 cm bowel distention upstream indicates
  functional obstruction

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Complications Star sign internal fistula
Post gad
Star sign of internal fistula Patient had
entero-entero fistula
HASTE
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Complications perianal dz
HASTE
Fistula post gad
FS post gad
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Complications perianal fistula
spair
Post gad
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Complications perianal fistula on T2 images
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Complications perianal abscess
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Complications phelgmon/abscess
Post-gad
trueFISP
Medial wall of terminal ileum is partially
indistinct and bulging medially suggesting
phlegmon/early abscess.
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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

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Pitfalls

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

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Pitfalls artifacts
HASTE
TruFISP
Arrowheads black boundary Arrow
susceptibility artifact from trapped air
curved arrow on both TI thickening
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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

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References

• Prassopoulos P, Papanikolaou N, Grammatikakis J,
  Rousomoustakaki M, Maris T, Gourtsoyiannis N. MR
  enteroclysis imaging of Crohn disease.
  RadioGraphics 200121(Spec Issue)S161S172
• Essary B, Kim J, Anupindi S, et al. Pelvic MRI in
  children with Crohn disease and suspected
  perianal involvement. Pediatr Radiol.
  200737201208
• Darge K, Anupindi S, Jaramillo D. MR Imaging of
  the Bowel Pediatric Applications. MRI Clinics N
  America.200816(3)467-478
• Toma P, Granata C, Magnano G, Barabino A. CT and
  MRI of paediatric Crohn disease. Pediatr Radiol.
  2007371065-1189.
• Greenhalgh R, Punwani S, Austin C Halligan S,
  Taylor S. The MRI manifestations of small bowel
  Crohns 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.
  200641239241

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Good resource

• http//lakeside2007.rsna.org/
• Electronic posters and papers through RSNA
  website
• Lakeside Learning Center
• Radiographics password

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