title: Quantitative analysis of diffusion-weighted magnetic resonance imaging in malignant breast lesions using different b value combinations.
abstract: OBJECTIVE
  To explore how apparent diffusion coefficients (ADCs) in malignant breast lesions are affected by selection of b values in the monoexponential model and to compare ADCs with diffusion coefficients (Ds) obtained from the biexponential model.
  
  
  METHODS
  Twenty-four women (mean age 51.3 years) with locally advanced breast cancer were included in this study. Pre-treatment diffusion-weighted magnetic resonance imaging was performed using a 1.5-T system with b values of 0, 50, 100, 250 and 800 s/mm(2). Thirteen different b value combinations were used to derive individual monoexponential ADC maps. All b values were used in the biexponential model.
  
  
  RESULTS
  Median ADC (including all b values) and D were 1.04 × 10(-3) mm(2)/s (range 0.82-1.61 × 10(-3) mm(2)/s) and 0.84 × 10(-3) mm(2)/s (range 0.17-1.56 × 10(-3) mm(2)/s), respectively. There was a strong positive correlation between ADCs and Ds. For clinically relevant b value combinations, maximum deviation between ADCs including and excluding low b values (<100 s/mm(2)) was 11.8 %.
  
  
  CONCLUSIONS
  Selection of b values strongly affects ADCs of malignant breast lesions. However, by excluding low b values, ADCs approach biexponential Ds, demonstrating that microperfusion influences the diffusion signal. Thus, care should be taken when ADC calculation includes low b values.
authors.affiliation: Department of Radiation Biology, Norwegian Radium Hospital, Oslo University Hospital, P.O. Box 4959, Nydalen 0424, Oslo, Norway. line.nilsen2@rr-research.no
authors.forename: Line B
authors.initials: LB
authors.lastname: Nilsen
authors.forename: Anne
authors.initials: A
authors.lastname: Fangberget
authors.forename: Oliver
authors.initials: O
authors.lastname: Geier
authors.forename: Therese
authors.initials: T
authors.lastname: Seierstad
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001943:Breast Neoplasms / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity