title: Diffusion-weighted imaging of the high-risk breast: Apparent diffusion coefficient values and their relationship to breast density.
abstract: OBJECTIVE
  To document the apparent diffusion coefficient (ADC) of fibroglandular breast tissue in women at high-risk of developing breast cancer and investigate the relationship between ADC and breast density.
  
  
  METHODS
  Local research ethics approval was obtained. A total of 33 high-risk women including 17 BRCA1/2 mutation carriers (mean age, 43 years) and 16 women postmantle irradiation (mean age 40 years) underwent diffusion-weighted MRI between days 6 and 16 of their menstrual cycle. ADC histograms from a region of interest in fibroglandular tissue and mammographic breast density measurements were obtained. Mean, percentile ADC values (10th, 25th, 50th, 75th, 90th) and skew were compared for the two groups; ADC and mammographic breast density were correlated.
  
  
  RESULTS
  Mean ADC values (×10(-6) mm(2) /s) were 2017 ± 197 in postmantle irradiated women and 1827 ± 289 in BRCA1/2 mutation carriers (P = 0.035) with significant differences at all percentiles (P < 0.0001) but not skew (P = 0.44). ADC values showed weak positive correlation with mammographic breast density in BRCA1/2 mutation carriers (r = 0.51, P = 0.043) but not in postmantle radiotherapy patients (r = 0.49, P = 0.13).
  
  
  CONCLUSIONS
  Higher ADC values seen in fibroglandular tissue postmantle irradiation compared with BRCA1/2 mutation carriers has potential to improve tumor detection in these patients. Lack of correlation between ADC and breast density postmantle irradiation may be a result of microstructural changes.
authors.affiliation: Clinical Magnetic Resonance Group, Cancer Research UK and EPSRC Cancer Imaging Centre, Royal Marsden NHS Foundation Trust, Downs Road, Sutton, Surrey, United Kingdom.
authors.forename: Elizabeth A M
authors.initials: EA
authors.lastname: O'Flynn
authors.forename: Robin M
authors.initials: RM
authors.lastname: Wilson
authors.forename: Steven D
authors.initials: SD
authors.lastname: Allen
authors.forename: Imogen
authors.initials: I
authors.lastname: Locke
authors.forename: Erica
authors.initials: E
authors.lastname: Scurr
authors.forename: Nandita M
authors.initials: NM
authors.lastname: deSouza
mesh_terms: D000328:Adult; D000465:Algorithms; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000503:physiopathology / Q000532:radiotherapy*; D003720:Densitometry / Q000379:methods*; 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; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016896:Treatment Outcome
keywords: BRCA1/2 mutation carrier; MRI; apparent diffusion coefficient; breast density; diffusion-weighted; high risk; mantle radiotherapy