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Update on MR Enterography

Update on MR Enterography. PMA GI Conference January 4, 2011 Alvin Yamamoto, MD Commonwealth Radiology Associates. Disclosure. No financial disclosures. Introduction. MR enterography (MRE) is a focused evaluation of the small bowel and surrounding soft tissues

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Update on MR Enterography

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  1. Update on MR Enterography PMA GI Conference January 4, 2011 Alvin Yamamoto, MD Commonwealth Radiology Associates

  2. Disclosure • No financial disclosures

  3. 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

  4. What is the best radiologic study? • Fluoroscopy • Small bowel follow-through (SBFT) • Enteroclysis • CTE • MRE

  5. 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

  6. 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)

  7. 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)

  8. 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

  9. 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.

  10. 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 CT 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.

  11. Why choose MR over CT?

  12. 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)

  13. 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

  14. 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

  15. Potential risk of MR?

  16. 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

  17. MRE technique

  18. 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

  19. 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)

  20. Suboptimal small bowel distension

  21. Adedquate small bowel distension

  22. 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

  23. Without glucagon With glucagon From: Fidler JL. MRE Protocol Optimization. SGR Abdominal Radiology Course 2010

  24. 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

  25. Coronal T2 w/o fat suppression w/fat suppression

  26. Axial T2 w/o fat suppression w/fat suppression

  27. Coronal FIESTA w/o fat suppression w/fat suppression

  28. Axial FIESTA

  29. Coronal T1 0 sec

  30. Coronal T1 40 sec post contrast

  31. Coronal T1 60 sec post contrast

  32. Coronal T1 80 sec post contrast

  33. Coronal T1 post-contrast 40 sec 60 sec 80 sec

  34. Axial T1 post contrast ~ 100 sec

  35. 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.

  36. Coronal FIESTA w/o fat suppression w/fat suppression

  37. Initial experience at NSMC

  38. 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

  39. Case 1 33 yo with abdominal pain and diarrhea, negative prior CT

  40. Normal exam CT (H20) T2 MRI

  41. Normal exam CT (H20) FIESTA MRI

  42. Normal exam CT (H20) T1+C MRI

  43. Case 2 48 yo w/CD, on Entocort, CT 2 mo earlier showing partial SBO w/inflammatory stricture

  44. Distal ileum inflammation CT T2 MRI T1+C MRI

  45. Skip segment in distal ileum CT T2 MRI T1+C MRI

  46. Case 3 67 yo newly dx’d CD, asymptomatic TI inflammation at prior colonoscopy

  47. TI inflammation T2 T1+C

  48. Skip segment in pelvis T2 T1+C

  49. Case 4 19 yo w/ CD on Pentasa and 6-MP, Decreased appetite, Strictured cecum on colonoscopy

  50. Thickened cecum and TI T1+C T2

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