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 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:

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.

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: and (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 3 rd 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 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 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 glucagonWith 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 suppressionw/fat suppression

Axial T2 w/o fat suppressionw/fat suppression

Coronal FIESTA w/o fat suppressionw/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 sec60 sec80 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 suppressionw/fat suppression

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 (H 2 0)

Normal exam FIESTA MRICT (H 2 0)

Normal exam CT (H 2 0)T1+C MRI

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

CTT1+C MRIT2 MRI Distal ileum inflammation

CTT1+C MRIT2 MRI Skip segment in distal ileum

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

T2T1+C TI inflammation

T2T1+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 FIESTAFIESTA w/FS

Chronic / treated RLQ inflammation T2T1+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

T2T1+CFIESTA Wall thickening at J-J anastomosis

T2T1+CFIESTA Wall thickening at J-J anastomosis

f/u CTPrior 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 indications for 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 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: 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– ACR Manual on Contrast Media – Version 7, Fidler JL. MRE Protocol Optimization. SGR Abdominal Radiology Course 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.