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Update on MR Enterography
PMA GI Conference January 4, 2011
Alvin Yamamoto, MDCommonwealth Radiology Associates
Disclosure
• No financial disclosures
Introduction
• MR enterography (MRE) is a focused evaluation of the small bowel and surrounding soft tissues
• Aim of this presentation is to discuss MRE for evaluation of pts with known or suspected Crohns disease
What is the best radiologic study?
• Fluoroscopy– Small bowel follow-through (SBFT)– Enteroclysis
• CTE
• MRE
Fluoroscopic exams
• Real time imaging• Enteroclysis
– Double contrast = “gold standard” imaging– Limited availability– Very uncomfortable
• SBFT – Single contrast = limited mucosal detail– Operator dependent, greater interobserver
variation
Fluoroscopy is a dying art
CTE
• Advantages– Scan time < 1 min– Greater spatial resolution– Less expensive than MRI
• Disadvantages– Exposure to ionizing radiation
• Pediatric patients• Multiple exams
– Contrast induced nephrotoxicity (CIN)
MRE
• Advantages– No ionizing radiation– Greater contrast resolution
• Disadvantages– Exam time 30 minutes– Requires greater pt compliance– Requires anti-peristaltic agent– More expensive than CT– Nephrogenic systemic fibrosis (NSF)
Image quality
• CT greater spatial resolution
• MR greater contrast resolution– Greater signal-to-noise ratio (SNR)– Fat suppression sequences– Subtraction imaging
• MR may be more sensitive– Fistulizing disease– Inflammatory vs fibrotic strictures
Reference: Al-Hawary M, et al. MRE: Why, When and How. SGR Abdominal Radiology Course 2010
CTE vs MRE vs SBFT
• Lee et al (2009) - 30 consecutive pts• CTE + MRE + SBFT • Ileocolonoscopy reference standard• Active small bowel CD
– Accuracy: CT 87%, MR 87%, SBFT 76%– Kappa: CT 0.8, MR 0.7, SBFT 0.5
• Extraenteric complications (fistula, sinus tract, abscess)– Sensitivity: CT & MR 100%, SBFT 35%
Lee SS, et al. Crohn Disease of the Small Bowel: Comparison of CT Enterography, MR Enterography, and Small-Bowel Follow-Through as Diagnostic Techniques. Radiology 2009; 251: 751-761.
CTE vs MRE
• Siddiki et al (2008) - 30 consecutive pts
• CTE + MRE
• Ileocolonoscopy reference standard
• Active small bowel CD– Sensitivity: CT 95%, MR 91%– Specificity: CT 89%, MR 67%– Kappa: CT 0.76, MR 0.63
• Image quality scores higher with CTSiddiki HA, et al. Prospective Comparison of State-of-the-Art MR Enterography and CT Enterography in Small-Bowel Crohn’s Disease. AJR 2008; 193:113–121.
Why choose MR over CT?
Radiation exposure
• Effective dose, millisievert (mSv)
• Whole body doses– Background: 3 mSv– Upper GI: 6 mSv– CT A/P: 15 mSv
• Approximate additional risk of fatal cancer for an adult from a single x-ray or CT is 1 in 10,000 to 1 in 1000
References: www.fda.gov and www.radiologyinfo.org (ACR and RSNA)
Radiation risk in pediatrics
• Children are considerably more sensitive to radiation than adults
• Larger window of opportunity for expressing radiation damage over a lifetime
• In the non-emergent setting, MRE should be considered over CTE for pediatric patients or young adults
Other patients to consider…
• If a non-IV contrast is necessary– Stage IV CKD (GFR < 30) – Pregnant patient
• MRE preferred over CTE– Provides increased SNR– Avoids ionizing radiation
Potential risk of MR?
Nephrogenic Sytemic Fibrosis
• NSF a potential complication of gadolinium (MRI) based IV contrast in pts with renal dysfunction
• Multisystem fibrosis, mainly skin• Relative risk of NSF (MR) << CIN (CT)
– MR contrast: Only a handful of cases reported in pts w/stage III CKD
– CT contrast: is the 3rd most common cause of hospital-acquired renal failure
• MR contrast is the lesser of the 2 evils
Reference: ACR Manual on Contrast Media – Version 7, 2010
MRE technique
Oral and IV contrast
• CTE and MRE use the same enteric contrast prep to distend the small bowel – VoLumen (2% sorbitol)– Locust bean gum + mannitol– Water is suboptimal
• CTE and MRE require IV contrast – Peak enhancement mucosa @ 40 sec– Progressive bowel wall p 60 sec
Oral contrast agent
• Adequate small bowel distension is crucial • We use 1350 mL of VoLumen (E-Z-EM)
– Sipped continuously over 45-60 minutes– Frequent monitoring of patient– Begin scanning 60 min from start of oral
contrast
• Pts informed about side effects, including abdominal spasms and diarrhea (2% sorbitol)
Suboptimal small bowel distension
Adedquate small bowel distension
Spasmolytic agents
• Glucagon 1 mg IM – preferred– or
• Hyocyamine (Levsin) 0.25 mg SL
• Administered immediately prior to scanning
• T1 post-contrast sequences are most susceptible to image degradation
From: Fidler JL. MRE Protocol Optimization. SGR Abdominal Radiology Course 2010
Without glucagon With glucagon
MRI sequences
• Pre-contrast sequences– Ultrafast T2 – Steady state free precession – With and w/o fat supression
• Post IV contrast sequences– Coronal T1 (0, 40, 60, 80 sec)– Axial T1 (100 sec)
• Total scan time < 30 minutes
Coronal T2
w/o fat suppression w/fat suppression
Axial T2
w/o fat suppression w/fat suppression
Coronal FIESTA
w/o fat suppression w/fat suppression
Axial FIESTA
Coronal T1
0 sec
Coronal T1
40 sec post contrast
Coronal T1
60 sec post contrast
Coronal T1
80 sec post contrast
40 sec 60 sec 80 sec
Coronal T1 post-contrast
~ 100 sec
Axial T1 post contrast
Steady state free precession MRI
• Also known as – FIESTA (GE)– True FISP (Siemens)– Balanced FFE (Philips)
• Signal is determined by ratio of T2/T1
• High resolution, high SNR– Exquisite evaluation of mesenteric
vasculature and lymph nodes
Bhosale P, et al. Utility of the FIESTA Pulse Sequence in Body Oncologic Imaging. AJR 2009;192:S83–S93.
Coronal FIESTA
w/o fat suppression w/fat suppression
Initial experience at NSMC
Initial experience at NSMC
• 17 patients– 5 known CD - 4 positive, 1 negative– 8 suspected CD - all negative– 4 anemia - all negative
• 5 pts w/CD– 3 pts - distal ileal inflammation– 2 pts - skip segments– 1 pt - ? jejunal inflammation
• 1 CD pt scanned at PMA– Fibrotic stricture of TI
Case 1
33 yo with abdominal pain and diarrhea, negative prior CT
Normal exam
T2 MRICT (H20)
Normal exam
FIESTA MRICT (H20)
Normal exam
CT (H20) T1+C MRI
Case 2
48 yo w/CD, on Entocort, CT 2 mo earlier showing partial SBO w/inflammatory stricture
CT T1+C MRIT2 MRI
Distal ileum inflammation
CT T1+C MRIT2 MRI
Skip segment in distal ileum
Case 3
67 yo newly dx’d CD, asymptomatic
TI inflammation at prior colonoscopy
T2 T1+C
TI inflammation
T2 T1+C
Skip segment in pelvis
Case 4
19 yo w/ CD on Pentasa and 6-MP,
Decreased appetite,
Strictured cecum on colonoscopy
Thickened cecum and TI
T2 T1+C
Thickened appendix
T2 T1+C
“comb sign” and adenopathy
FIESTA FIESTA w/FS
Chronic / treated RLQ inflammation
T2 T1+CFIESTA
Prior SBFT in 2006
Case 5
38 yo w/CD on 6-MP,Wt loss, fatigue, abd pain,
Gastric bypass 2008,Negative EGD up to G-J
T2 T1+CFIESTA
Wall thickening at J-J anastomosis
T2 T1+CFIESTA
Wall thickening at J-J anastomosis
f/u CT Prior MRI
CT 3 wks later…
Transient enteritis vs intussusception?
NSMC case
Transient intussusception?
From: Leyendecker JR, et al. MR Enterography in the Management of Patients with Crohn Disease. RadioGraphics 2009; 29:1827–1846
Case 6 - PMA
39 yo w/CD, on Humira
Bloating, distension, RLQ pain,
Strictured ICV at colonoscopy
Mild thickening/narrowing of TI
T2
No enhancement
T1 + C
Inflammatory vs fibrotic stricture
From: Al-Hawary M, et al. MRE: Why, When and How. SGR Abdominal Radiology Course 2010
Follow up colonoscopy
• Mild narrowing and inflammation of ICV
• Scope passed through ICV
Extraenteric complications
Enteroenteric fistula
From: Leyendecker JR, et al. MR Enterography in the Management of Patients with Crohn Disease. RadioGraphics 2009; 29:1827–1846
Ileocolic fistula
From: Leyendecker JR, et al. MR Enterography in the Management of Patients with Crohn Disease. RadioGraphics 2009; 29:1827–1846
Enterovesical fistula
From: Leyendecker JR, et al. MR Enterography in the Management of Patients with Crohn Disease. RadioGraphics 2009; 29:1827–1846
Abscess
From: Al-Hawary M, et al. MRE: Why, When and How. SGR Abdominal Radiology Course 2010
In the acute setting… CT with IV and positive oral contrast should be obtained
Other possible indicationsfor MRE?
• Small bowel tumors
• Large bowel pathology
CT or fluoroscopy is preferred
Summary
• MRE is an established technique with nearly equivalent accuracy to CTE
• The principle benefit of MRE is the ability to safely image patients without the use of ionizing radiation
• This is particularly relevant in young patients that will potentially undergo multiple imaging evaluations
Conclusions
• MR is the study of choice– Pts with established CD– Young/pediatric pts– Pts with stage III, IV CKD– Pregnant pts
• CT is the study of choice– Older pts with suspected CD– Large or claustrophobic pts – Suspected colitis or small bowel tumor
Thank you• Al-Hawary M, et al. MRE: Why, When and How. SGR Abdominal Radiology Course
2010.• Lee SS, et al. Crohn Disease of the Small Bowel: Comparison of CT Enterography,
MR Enterography, and Small-Bowel Follow-Through as Diagnostic Techniques. Radiology 2009; 251: 751-761.
• Siddiki HA, et al. Prospective Comparison of State-of-the-Art MR Enterography and CT Enterography in Small-Bowel Crohn’s Disease. AJR 2008; 193:113–121.
• www.fda.gov• www.radiologyinfo.org• ACR Manual on Contrast Media – Version 7, 2010.• Fidler JL. MRE Protocol Optimization. SGR Abdominal Radiology Course 2010.• Bhosale P, et al. Utility of the FIESTA Pulse Sequence in Body Oncologic Imaging.
AJR 2009;192:S83–S93.• Leyendecker JR, et al. MR Enterography in the Management of Patients with Crohn
Disease. RadioGraphics 2009; 29:1827–1846.