Update on MR Enterography PMA GI Conference January 4, 2011 Alvin Yamamoto, MD Commonwealth...
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Transcript of Update on MR Enterography PMA GI Conference January 4, 2011 Alvin Yamamoto, MD Commonwealth...
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.