title: Computed diffusion-weighted MRI for prostate cancer detection: the influence of the combinations of b-values.
abstract: OBJECTIVE
  To evaluate the influence of the combinations of b-values on computed diffusion-weighted images (cDWIs) for prostate cancer (PCa) detection at b = 2000 s mm(-2).
  
  
  METHODS
  Diffusion-weighted imaging (DWIs) for 31 patients with PCa (65.2 ± 7.1 years) were obtained pre-operatively at different b-values (0, 100, 500, 1000 and 2000 s mm(-2)) on a 3-T MRI. cDWIs at b = 2000 were generated by using six b-value combinations: 0-100 s mm(-2) (cDWI0-100); 0-500 s mm(-2) (cDWI0-500); 100-500 s mm(-2) (cDWI100-500); 0-1000 s mm(-2) (cDWI0-1000); 100-1000 s mm(-2) (cDWI100-1000); and 500-1000 s mm(-2) (cDWI500-1000). These cDWIs and measured DWIs with b = 2000 s mm(-2) (mDWI2000) were evaluated in this setting. To assess image quality for each DWI, contrast ratios (CRs) of cancerous and non-cancerous lesions were evaluated. To compare the detectability of PCa for each DWI, receiver operating characteristic analysis was used.
  
  
  RESULTS
  CRs of all cDWIs were significantly higher than those of mDWI2000 (p < 0.05). Areas under the curve of cDWI0-100 (0.62) and cDWI0-500 (0.65) were significantly smaller (p < 0.05) than those of others (cDWI100-500, 0.72; cDWI0-1000, 0.73; cDWI100-1000, 0.71; cDWI500-1000, 0.74; mDWI2000, 0.72).
  
  
  CONCLUSIONS
  The combinations of b-values influenced image quality and diagnostic ability of cDWIs for PCa detection. The combinations of b ≥ 100 and b ≥ 500 s mm(-2), as well as b = 0 and b = 1000 s mm(-2), were optimal in this study.
  
  
  CONCLUSIONS
  For generating the useful cDWI for PCa detection, radiologists should take care of the combination of b-values when including low b-values.
authors.affiliation: 1 Department of Radiology, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Ueno
authors.forename: S
authors.initials: S
authors.lastname: Takahashi
authors.forename: Y
authors.initials: Y
authors.lastname: Ohno
authors.forename: K
authors.initials: K
authors.lastname: Kitajima
authors.forename: M
authors.initials: M
authors.lastname: Yui
authors.forename: Y
authors.initials: Y
authors.lastname: Kassai
authors.forename: F
authors.initials: F
authors.lastname: Kawakami
authors.forename: H
authors.initials: H
authors.lastname: Miyake
authors.forename: K
authors.initials: K
authors.lastname: Sugimura
mesh_terms: D000368:Aged; D001706:Biopsy; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D060787:Neoplasm Grading; D011237:Predictive Value of Tests; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D012189:Retrospective Studies; D012680:Sensitivity and Specificity