title: Value of diffusion-weighted imaging when added to magnetic resonance enterographic evaluation of Crohn disease in children.
abstract: BACKGROUND
  MR enterography is increasingly utilized for noninvasive evaluation of disease activity in young patients with Crohn disease and has great impact on clinical management. Diffusion-weighted imaging (DWI) is a rapid MR imaging technique that measures molecular diffusion of water and is sensitive to the inflammatory process; however, its value to MR enterography has not been rigorously evaluated.
  
  
  OBJECTIVE
  To determine whether the addition of DWI to MR enterography is helpful in evaluating Crohn disease activity in young patients when compared to a histological reference.
  
  
  METHODS
  In this single-institution retrospective study, we searched an imaging database for the period January 2010 to December 2012 to identify patients age 19 years and younger who had MR enterography with diffusion-weighted imaging (DWI). We used an electronic medical record search to identify those who had MR enterography and colonoscopy performed within 28 days of each other. All MR enterography scans were performed on a 1.5-T or 3-T clinical MR scanner with phased-array torso coil configuration using standard pulse sequences as well as axial DWI with b values of 50, 400 and 800. Bowel segments were evaluated for disease activity based on standard MR enterography sequences; in addition, segmental apparent diffusion coefficient (ADC) values were calculated based on DWI. Histological reference for disease activity was based on assessment for mucosal inflammatory changes on endoscopic biopsy. MR enterography and DWI evaluation were performed in a blinded fashion with respect to histological results.
  
  
  RESULTS
  We included imaging of 78 bowel segments from 27 patients (mean age 14.5 ± 3.02 years) with known Crohn disease in the study. The mean ADC for bowel segments with active disease was 1.56 ± 0.7 × 10(3) mm(2)/s compared with 2.58 ± 1.4 × 10(3) mm(2)/s for segments without active disease, a difference that was statistically significant (P < 0.01, Student's t-test). Using a threshold value of 2.0 × 10(3) mm(2)/s, DWI demonstrated lower accuracy (64.1%) but higher sensitivity (78.8%) for detecting active disease compared with standard MR enterography (69.2% and 54.6%, respectively). Combining DWI with MR enterography, using DWI as the initial screen and MR enterography afterward to reduce false negativity, led to a significant increase in accuracy (76.9%; P = 0.03, McNemar's test) compared with either imaging technique alone.
  
  
  CONCLUSIONS
  Although DWI does not perform as well as standard MR enterography for detection of active Crohn disease, the combination of DWI and MR enterography increases imaging accuracy for determining disease activity compared with either technique alone. These results indicate that DWI adds value to MR enterography and supports the incorporation of DWI into MR enterography protocols for evaluation of Crohn disease in young patients.
authors.affiliation: Division of Abdominal Imaging/Community Radiology, Shapiro Clinical Center, Beth Israel Deaconess Medical Center, 330 Brookline Ave., 4th Floor, Boston, MA, 02215, USA. abhangle@bidmc.harvard.edu.
authors.forename: Anuradha S
authors.initials: AS
authors.lastname: Shenoy-Bhangle
authors.affiliation: Division of Pediatric Imaging, Department of Radiology, Massachusetts General Hospital for Children, Boston, MA, USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Nimkin
authors.affiliation: Queen Elizabeth II Health Sciences Centre, Halifax, Nova Scotia, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Aranson
authors.affiliation: Division of Pediatric Imaging, Department of Radiology, Massachusetts General Hospital for Children, Boston, MA, USA.|Division of Abdominal Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Gee
mesh_terms: D000293:Adolescent; D002648:Child; D003287:Contrast Media; D003424:Crohn Disease / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007421:Intestine, Small / Q000473:pathology*; D008297:Male; D064847:Multimodal Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D003287:Contrast Media
keywords: Children; Crohn disease; Diffusion-weighted imaging; Histology; Magnetic resonance enterography