title: Comparison of Dixon Sequences for Estimation of Percent Breast Fibroglandular Tissue.
abstract: OBJECTIVE
  To evaluate sources of error in the Magnetic Resonance Imaging (MRI) measurement of percent fibroglandular tissue (%FGT) using two-point Dixon sequences for fat-water separation.
  
  
  METHODS
  Ten female volunteers (median age: 31 yrs, range: 23-50 yrs) gave informed consent following Research Ethics Committee approval. Each volunteer was scanned twice following repositioning to enable an estimation of measurement repeatability from high-resolution gradient-echo (GRE) proton-density (PD)-weighted Dixon sequences. Differences in measures of %FGT attributable to resolution, T1 weighting and sequence type were assessed by comparison of this Dixon sequence with low-resolution GRE PD-weighted Dixon data, and against gradient-echo (GRE) or spin-echo (SE) based T1-weighted Dixon datasets, respectively.
  
  
  RESULTS
  %FGT measurement from high-resolution PD-weighted Dixon sequences had a coefficient of repeatability of ±4.3%. There was no significant difference in %FGT between high-resolution and low-resolution PD-weighted data. Values of %FGT from GRE and SE T1-weighted data were strongly correlated with that derived from PD-weighted data (r = 0.995 and 0.96, respectively). However, both sequences exhibited higher mean %FGT by 2.9% (p < 0.0001) and 12.6% (p < 0.0001), respectively, in comparison with PD-weighted data; the increase in %FGT from the SE T1-weighted sequence was significantly larger at lower breast densities.
  
  
  CONCLUSIONS
  Although measurement of %FGT at low resolution is feasible, T1 weighting and sequence type impact on the accuracy of Dixon-based %FGT measurements; Dixon MRI protocols for %FGT measurement should be carefully considered, particularly for longitudinal or multi-centre studies.
authors.affiliation: CR-UK Cancer Imaging Centre, The Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Araminta E W
authors.initials: AE
authors.lastname: Ledger
authors.affiliation: Department of Radiology, Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Erica D
authors.initials: ED
authors.lastname: Scurr
authors.affiliation: Department of Radiology, Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Julie
authors.initials: J
authors.lastname: Hughes
authors.affiliation: Department of Radiology, Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Alison
authors.initials: A
authors.lastname: Macdonald
authors.affiliation: Department of Radiology, Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Toni
authors.initials: T
authors.lastname: Wallace
authors.affiliation: Clinical Research and Development, Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Thomas
authors.affiliation: Department of Radiology, Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Robin
authors.initials: R
authors.lastname: Wilson
authors.affiliation: CR-UK Cancer Imaging Centre, The Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Martin O
authors.initials: MO
authors.lastname: Leach
authors.affiliation: CR-UK Cancer Imaging Centre, The Institute of Cancer Research and Royal Marsden NHS Foundation Trust, London, United Kingdom.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Schmidt
mesh_terms: D000328:Adult; D001940:Breast / Q000473:pathology; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008327:Mammography / Q000379:methods*; D008875:Middle Aged