title: Clinical usefulness of diffusion-weighted imaging using low and high b-values to detect rectal cancer.
abstract: OBJECTIVE
  The purpose of this study was to assess the potential role of diffusion-weighted imaging (DWI) using low and high b-values to detect rectal cancer.
  
  
  METHODS
  The subjects were 15 patients diagnosed endoscopically with rectal cancer (m in 1 patient, sm in 0, mp in 3, ss in 7, se in 1, a in 3) and 20 patients diagnosed endoscopically with colon cancer and no other lesions (control group). Magnetic resonance imaging was performed using a 1.5T system. DWI was performed in the axial plane using echo planar imaging sequence (repetition time/echo time 1200/66, field of view 306x350 mm, reconstruction matrix 156x256, pixel size 2.0x1.4x8.0 mm) and acquired with 2 b-values (50 and 800 s/mm2). Low and high b-value DW images were analyzed visually. A lesion was positive by detection of a focal area of high signal in the rectum in high b-value images. The apparent diffusion coefficient (ADC) values of areas of high signal in high b-value images were calculated from the low and high b-value images.
  
  
  RESULTS
  High b-value images enabled visualization of all 15 rectal cancers. In the control group, 13 cases were classified as negative and 7 cases as positive for rectal cancer. Sensitivity for detection of rectal cancer was 100% (15/15), and specificity was 65% (13/20). The mean ADC values in 7 patients with false-positive lesions and in 15 patients with rectal cancer were 1.374x10(-3) mm2/s (standard deviation [SD]: 0.157) and 1.194x10(-3) mm2/s (SD: 0.152), respectively (P=0.026).
  
  
  CONCLUSIONS
  DWI with low and high b-values may be used to screen for rectal cancer.
authors.affiliation: Department of Surgery, Jikei University School of Medicine, Tokyo, Japan. hosonuma@jikei.ac.jp
authors.forename: Tomonori
authors.initials: T
authors.lastname: Hosonuma
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Tozaki
authors.forename: Noriatsu
authors.initials: N
authors.lastname: Ichiba
authors.forename: Tohru
authors.initials: T
authors.lastname: Sakuma
authors.forename: Daichi
authors.initials: D
authors.lastname: Hayashi
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yanaga
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Fukuda
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000175:diagnosis*; D012007:Rectum / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity