title: Breast tissue composition and its dependence on demographic risk factors for breast cancer: non-invasive assessment by time domain diffuse optical spectroscopy.
abstract: BACKGROUND
  Breast tissue composition is recognized as a strong and independent risk factor for breast cancer. It is a heritable feature, but is also significantly affected by several other elements (e.g., age, menopause). Nowadays it is quantified by mammographic density, thus requiring the use of ionizing radiation. Optical techniques are absolutely non-invasive and have already proved effective in the investigation of biological tissues, as they are sensitive to tissue composition and structure.
  
  
  METHODS
  Time domain diffuse optical spectroscopy was performed at 7 wavelengths (635-1060 nm) on 200 subjects to derive their breast tissue composition (in terms of water, lipid and collagen content), blood parameters (total hemoglobin content and oxygen saturation level), and information on the microscopic structure (scattering amplitude and power). The dependence of all optically-derived parameters on age, menopausal status, body mass index, and use of oral contraceptives, and the correlation with mammographic density were investigated.
  
  
  RESULTS
  Younger age, premenopausal status, lower body mass index values, and use of oral contraceptives all correspond to significantly higher water, collagen and total hemoglobin content, and lower lipid content (always p < 0.05 and often p < 10-4), while oxygen saturation level and scattering parameters show significant dependence only on some conditions. Even when age-adjusted groups of subjects are compared, several optically derived parameters (and in particular always collagen and total hemoglobin content) remain significantly different.
  
  
  CONCLUSIONS
  Time domain diffuse optical spectroscopy can probe non-invasively breast tissue composition and physiologic blood parameters, and provide information on tissue structure. The measurement is suitable for in vivo studies and monitoring of changes in breast tissue (e.g., with age, lifestyle, chemotherapy, etc.) and to gain insight into related processes, like the origin of cancer risk associated with breast density.
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Milano, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Taroni
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Milano, Italy.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Quarto
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Milano, Italy; Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milano, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pifferi
authors.affiliation: European Institute of Oncology, Breast Imaging Unit, Milano, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Abbate
authors.affiliation: European Institute of Oncology, Department of Radiology, Milano, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Balestreri
authors.affiliation: European Institute of Oncology, Breast Imaging Unit, Milano, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Menna
authors.affiliation: European Institute of Oncology, Breast Imaging Unit, Milano, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Cassano
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano, Milano, Italy; Istituto di Fotonica e Nanotecnologie, Consiglio Nazionale delle Ricerche, Milano, Italy.
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Cubeddu
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001940:Breast / Q000473:pathology*; D000071060:Breast Density; D001943:Breast Neoplasms / Q000473:pathology*; D003710:Demography / Q000379:methods; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000002:abnormalities / Q000473:pathology; D008593:Menopause / Q000502:physiology; D008875:Middle Aged; D055095:Optics and Photonics / Q000379:methods; D017697:Premenopause / Q000502:physiology; D012307:Risk Factors; D041622:Tomography, Optical / Q000379:methods