title: Diffusion-weighted MRI for evaluating perianal fistula activity: feasibility study.
abstract: OBJECTIVE
  To assess the feasibility of using diffusion-weighted magnetic resonance (MR) imaging (DWI) for evaluating perianal fistula activity.
  
  
  METHODS
  This study retrospectively assessed 24 patients with clinically suspected perianal fistula who underwent a total of 28 MR examinations after conservative treatment with antibiotics. DWI was performed at 1.5 T, using b-values of 0 and 1000 s/mm(2). Apparent diffusion coefficient (ADC) maps were created and ADCs of the lesions were measured. Lesions were classified into two groups based on the need for surgery and surgical findings: positive inflammation activity (PIA) and negative inflammation activity (NIA). ADCs of both groups were compared using an unpaired t-test, and Receiver Operating Characteristic (ROC) analysis was performed.
  
  
  RESULTS
  The ADC (in 10(-3) mm(2)/s) of the PIA group (0.908±0.171) was significantly lower (P=0.0019) than that of the NIA group (1.124±0.244). The area under the ROC curve was 0.749. An optimal cut-off ADC of 1.109 yielded a sensitivity of 95.7%, a specificity of 50%, a positive predictive value of 71%, and a negative predictive value of 90%.
  
  
  CONCLUSIONS
  DWI is a feasible method for evaluating perianal fistula activity. The diagnostic performance of this technique should be established in future, larger prospective studies.
authors.affiliation: Department of Radiology, Shimane University Faculty of Medicine, P.O. Box 00693-8501, 89-1 Enya Izumo, Japan. yoshizako@med.shimane-u.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yoshizako
authors.forename: Akihiko
authors.initials: A
authors.lastname: Wada
authors.forename: Taro
authors.initials: T
authors.lastname: Takahara
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Kwee
authors.forename: Megumi
authors.initials: M
authors.lastname: Nakamura
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
authors.forename: Shinji
authors.initials: S
authors.lastname: Hara
authors.forename: Peter R
authors.initials: PR
authors.lastname: Luijten
authors.forename: Hajime
authors.initials: H
authors.lastname: Kitagaki
mesh_terms: D000328:Adult; D000368:Aged; D001003:Anal Canal / Q000002:abnormalities* / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007412:Intestinal Fistula / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity