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.