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

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