title: Diffusion-weighted MR imaging for detection of extrahepatic cholangiocarcinoma.
abstract: OBJECTIVE
  To measure the sensitivity of diffusion-weighted imaging (DWI) and determine the most appropriate b value for DWI; to explore the correlation between the apparent diffusion coefficient (ADC) value and the degree of extrahepatic cholangiocarcinoma differentiation.
  
  
  METHODS
  Preoperative diffusion-weighted imaging and magnetic resonance examinations were performed for 31 patients with extrahepatic cholangiocarcinoma. Tumor ADC values were measured, and the signal-to-noise ratio, contrast-to-noise ratio, and signal-intensity ratio between the diffusion-weighted images with various b values as well as the T2-weighted images were calculated. Pathologically confirmed patients were pathologically graded to compare the ADC value with different b values of tumor at different degrees of differentiation, and the results were statistically analyzed by using the Friedman test.
  
  
  RESULTS
  A total of 29 cases of extrahepatic cholangiocarcinoma were detected by DWI. As the b value increased, tumor signal-to-noise ratio and contrast-to-noise ratio between the tumor and normal liver gradually decreased, but the tumor signal-intensity ratio gradually increased. When b=800 s/mm2, contrast-to-noise ratio between tumor and normal liver, tumor signal-intensity ratio, and tumor signal-to-noise ratio of diffusion-weighted images were all higher than those of T2-weighted images; the differences were statistically significant (P<0.05). As the b value increased, the tumor ADC value gradually declined. As the degree of differentiation decreased, the tumor ADC value declined.
  
  
  CONCLUSIONS
  The b value of 800 s/mm2 was the best in DWI of extrahepatic cholangiocarcinoma; the lesion ADC value declined as the degree of cancerous tissue differentiation decreased.
authors.affiliation: Department of Radiology, Wuxi People's Hospital, Nanjing Medical University, No. 299, QingYang Rd, Wuxi 214023, Jiangsu Province, China. cuixingyu76@hotmail.com
authors.forename: Xing-Yu
authors.initials: XY
authors.lastname: Cui
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Chen
authors.forename: Song
authors.initials: S
authors.lastname: Cai
authors.forename: Jian
authors.initials: J
authors.lastname: Bao
authors.forename: Qun-Feng
authors.initials: QF
authors.lastname: Tang
authors.forename: Li-Yuan
authors.initials: LY
authors.lastname: Wu
authors.forename: Xiang-Ming
authors.initials: XM
authors.lastname: Fang
mesh_terms: D000328:Adult; D000368:Aged; D001650:Bile Duct Neoplasms / Q000473:pathology*; D017734:Bile Ducts, Extrahepatic / Q000473:pathology*; D018281:Cholangiocarcinoma / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity