title: Diffusion weighted imaging of the normal breast: reproducibility of apparent diffusion coefficient measurements and variation with menstrual cycle and menopausal status.
abstract: OBJECTIVE
  To establish the reproducibility of apparent diffusion coefficient (ADC) measurements in normal fibroglandular breast tissue and to assess variation in ADC values with phase of the menstrual cycle and menopausal status.
  
  
  METHODS
  Thirty-one volunteers (13 premenopausal, 18 postmenopausal) underwent magnetic resonance twice (interval 11-22 days) using diffusion-weighted MRI. ADC(total) and a perfusion-insensitive ADC(high) (omitting b = 0) were calculated. Reproducibility and inter-observer variability of mean ADC values were assessed. The difference in mean ADC values between the two phases of the menstrual cycle and the postmenopausal breast were evaluated.
  
  
  RESULTS
  ADC(total) and ADC(high) showed good reproducibility (r% = 17.6, 22.4). ADC(high) showed very good inter-observer agreement (kappa = 0.83). The intraclass correlation coefficients (ICC) were 0.93 and 0.91. Mean ADC values were significantly lower in the postmenopausal breast (ADC(total) 1.46 ± 0.3 × 10(-3) mm(2)/s, ADC(high) 1.33 ± 0.3 × 10(-3) mm(2)/s) compared with the premenopausal breast (ADC(total) 1.84 ± 0.26 × 10(-3) mm(2)/s, ADC(high) 1.77 ± 0.26 × 10(-3) mm(2)/s; both P < 0.001). No significant difference was seen in ADC values in relation to menstrual cycle (ADC(total)                            P = 0.2, ADC(high)                            P = 0.24) or between postmenopausal women taking or not taking oestrogen supplements (ADC(total)                            P = 0.6, ADC(high)                            P = 0.46).
  
  
  CONCLUSIONS
  ADC values in fibroglandular breast tissue are reproducible. Lower ADC values within the postmenopausal breast may reduce diffusion-weighted contrast and have implications for accurately detecting tumours.
  
  
  CONCLUSIONS
  • ADC values from fibroglandular breast tissue are measured reproducibly by multiple observers.                                                                              • Mean ADC values were significantly lower in postmenopausal than premenopausal breast tissue.                                                                              • Mean ADC values did not vary significantly with menstrual cycle.                                                                              • Low postmenopausal ADC values may hinder tumour detection on DW-MRI.
authors.affiliation: Clinical Magnetic Resonance Group, Cancer Research UK and ESPSRC Cancer Imaging Centre, Downs Road, Sutton, Surrey, UK, SM2 5PT. lizoflynn@doctors.org.uk
authors.forename: Elizabeth A M
authors.initials: EA
authors.lastname: O'Flynn
authors.forename: Veronica A
authors.initials: VA
authors.lastname: Morgan
authors.forename: Sharon L
authors.initials: SL
authors.lastname: Giles
authors.forename: Nandita M
authors.initials: NM
authors.lastname: deSouza
mesh_terms: D000328:Adult; D000368:Aged; D001940:Breast / Q000033:anatomy & histology* / Q000502:physiology*; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008593:Menopause / Q000502:physiology*; D008597:Menstrual Cycle / Q000502:physiology*; D015588:Observer Variation; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity