title: Understanding the contributions of NADH and collagen to cervical tissue fluorescence spectra: modeling, measurements, and implications.
abstract: OBJECTIVE
  At 380 nm excitation, cervical tissue fluorescence spectra demonstrate characteristic changes with both patient age and the presence of dysplasia. A Monte Carlo model was developed in order to quantitatively examine how intrinsic NADH and collagen fluorescence, in combination with tissue scattering and absorption properties, yield measured tissue spectra.
  
  
  METHODS
  Excitation-emission matrices were measured for live cervical cells and collagen gel phantoms. Fluorescence microscopy of fresh tissue sections was performed to obtain the location and density of fluorophores as a function of patient age and the presence of dysplasia. A Monte Carlo model was developed which incorporated measurements of fluorophore line shapes and spatial distributions.
  
  
  RESULTS
  Modeled spectra were consistent with clinical measurements and indicate that an increase in NADH fluorescence and decrease in collagen fluorescence create clinically observed differences between normal and dysplastic tissue spectra. Model predictions were most sensitive to patient age and epithelial thickness.
  
  
  CONCLUSIONS
  Monte Carlo techniques provide an important means to investigate the combined contributions of multiple fluorophores to measured emission spectra. The approach will prove increasingly valuable as a more sophisticated understanding of in vivo optical properties is developed.
authors.affiliation: Biomedical Engineering Program, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: R
authors.initials: R
authors.lastname: Drezek
authors.forename: K
authors.initials: K
authors.lastname: Sokolov
authors.forename: U
authors.initials: U
authors.lastname: Utzinger
authors.forename: I
authors.initials: I
authors.lastname: Boiko
authors.forename: A
authors.initials: A
authors.lastname: Malpica
authors.forename: M
authors.initials: M
authors.lastname: Follen
authors.forename: R
authors.initials: R
authors.lastname: Richards-Kortum
mesh_terms: D000328:Adult; D000367:Age Factors; D002584:Cervix Uteri / Q000737:chemistry*; D003094:Collagen / Q000032:analysis*; D005260:Female; D006801:Humans; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D008954:Models, Biological; D009010:Monte Carlo Method; D009243:NAD / Q000032:analysis*; D013050:Spectrometry, Fluorescence; D002578:Uterine Cervical Dysplasia / Q000737:chemistry* / Q000175:diagnosis; D002583:Uterine Cervical Neoplasms / Q000737:chemistry* / Q000175:diagnosis
chemical_list: D009243:NAD; D003094:Collagen