title: Optimization of b-value distribution for biexponential diffusion-weighted MR imaging of normal prostate.
abstract: OBJECTIVE
  To determine the optimal b-value distribution for biexponential diffusion-weighted imaging (DWI) of normal prostate using both a computer modeling approach and in vivo measurements.
  
  
  METHODS
  Optimal b-value distributions for the fit of three parameters (fast diffusion Df, slow diffusion Ds, and fraction of fast diffusion f) were determined using Monte-Carlo simulations. The optimal b-value distribution was calculated using four individual optimization methods. Eight healthy volunteers underwent four repeated 3 Tesla prostate DWI scans using both 16 equally distributed b-values and an optimized b-value distribution obtained from the simulations. The b-value distributions were compared in terms of measurement reliability and repeatability using Shrout-Fleiss analysis.
  
  
  RESULTS
  Using low noise levels, the optimal b-value distribution formed three separate clusters at low (0-400 s/mm2), mid-range (650-1200 s/mm2), and high b-values (1700-2000 s/mm2). Higher noise levels resulted into less pronounced clustering of b-values. The clustered optimized b-value distribution demonstrated better measurement reliability and repeatability in Shrout-Fleiss analysis compared with 16 equally distributed b-values.
  
  
  CONCLUSIONS
  The optimal b-value distribution was found to be a clustered distribution with b-values concentrated in the low, mid, and high ranges and was shown to improve the estimation quality of biexponential DWI parameters of in vivo experiments.
authors.affiliation: Department of Diagnostic Radiology, University of Turku, Turku, Finland; 2nd Department of Radiology, Comenius University and St. Elisabeth Oncology Institute, Bratislava, Slovakia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Jambor
authors.forename: Harri
authors.initials: H
authors.lastname: Merisaari
authors.forename: Hannu J
authors.initials: HJ
authors.lastname: Aronen
authors.forename: Jukka
authors.initials: J
authors.lastname: Järvinen
authors.forename: Jani
authors.initials: J
authors.lastname: Saunavaara
authors.forename: Tommi
authors.initials: T
authors.lastname: Kauko
authors.forename: Ronald
authors.initials: R
authors.lastname: Borra
authors.forename: Marko
authors.initials: M
authors.lastname: Pesola
mesh_terms: D000328:Adult; D000465:Algorithms; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015233:Models, Statistical; D011467:Prostate / Q000033:anatomy & histology*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016008:Statistical Distributions
keywords: MRI; Monte-Carlo simulations; Shrout-Fleiss analysis; diffusion-weighted imaging; normal prostate