title: Diagnostic value of ADC in patients with prostate cancer: influence of the choice of b values.
abstract: OBJECTIVE
  To evaluate the influence of the choice of b values on the diagnostic value of the apparent diffusion coefficient (ADC) for detection and grading of prostate cancer (PCa).
  
  
  METHODS
  Forty-one patients with biopsy-proven PCa underwent endorectal 3-T MRI before prostatectomy. Different combinations of b values (0-800 s/mm(2)) were used to calculate four representative ADC maps. Mean ADCs of tumours and non-malignant tissue were determined. Tumour appearance on different ADC maps was rated by three radiologists as good, fair or poor by assigning a visual score (VS) of 2, 1 or 0, respectively. Differences in the ADC values with the choice of b values were analysed using one-way ANOVA.
  
  
  RESULTS
  Choice of b values had a highly (P < 0.001) significant influence on the absolute ADC in each tissue. Maps using b = [50, 800] and [0, 800] were rated best (VS= 1.6 ± 0.3) and second best (1.1 ± 0.3, P < 0.001), respectively. For low-grade carcinomas (Gleason score ≤ 6, 13/41 patients), only the former choice received scores better than fair (VS = 1.4 ± 0.3). Mean tumour ADCs showed significant negative correlation (Spearman's ρ -0.38 to -0.46, P < 0.05) with Gleason score.
  
  
  CONCLUSIONS
  Absolute ADC values strongly depend on the choice of b values and therefore should be used with caution for diagnostic purposes. A minimum b value greater than zero is recommended for ADC calculation to improve the visual assessment of PCa in ADC maps.
  
  
  CONCLUSIONS
  • Absolute ADC values are highly dependent on the choice of b values. • Absolute ADC thresholds should be used carefully to predict tumour aggressiveness. • Subjective ratings of ADC maps involving b = 0 s/mm ( 2 ) are poor to fair. • Minimum b value greater than 0 s/mm ( 2 ) is recommended for ADC calculation.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Leipzig University Hospital, Liebigstrasse 20, 04103 Leipzig, Germany.
authors.forename: Gregor
authors.initials: G
authors.lastname: Thörmer
authors.forename: Josephin
authors.initials: J
authors.lastname: Otto
authors.forename: Martin
authors.initials: M
authors.lastname: Reiss-Zimmermann
authors.forename: Matthias
authors.initials: M
authors.lastname: Seiwerts
authors.forename: Michael
authors.initials: M
authors.lastname: Moche
authors.forename: Nikita
authors.initials: N
authors.lastname: Garnov
authors.forename: Toni
authors.initials: T
authors.lastname: Franz
authors.forename: Minh
authors.initials: M
authors.lastname: Do
authors.forename: Jens-Uwe
authors.initials: JU
authors.lastname: Stolzenburg
authors.forename: Lars-Christian
authors.initials: LC
authors.lastname: Horn
authors.forename: Thomas
authors.initials: T
authors.lastname: Kahn
authors.forename: Harald
authors.initials: H
authors.lastname: Busse
mesh_terms: D000368:Aged; D003952:Diagnostic Imaging / Q000379:methods / Q000592:standards; D004058:Diffusion; D017352:Echo-Planar Imaging / Q000379:methods; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000592:standards; D008297:Male; D008495:Medical Oncology / Q000379:methods*; D008875:Middle Aged; D060787:Neoplasm Grading; D015588:Observer Variation; D017430:Prostate-Specific Antigen / Q000096:biosynthesis; D011468:Prostatectomy / Q000379:methods; D011471:Prostatic Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D012189:Retrospective Studies
chemical_list: D017430:Prostate-Specific Antigen