Understanding the contributions of NADH and collagen to cervical tissue fluorescence spectra: modeling, measurements, and implications.

Objective: At 380 nm excitation, cervical tissue fluores- cence spectra demonstrate characteristic changes with both patient age and the presence of dysplasia. A Monte Carlo model was devel- oped in order to quantitatively examine how intrinsic NADH and collagen fluorescence, in combination with tissue scattering and ab- sorption properties, yield measured tissue spectra. Methods: Excitation-emission matrices were measured for live cervical cells and collagen gel phantoms. Fluorescence microscopy of fresh tissue sec- tions 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 fluores- cence create clinically observed differences between normal and dys- plastic 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 understand- ing of in vivo optical properties is developed. © 2001 Society of Photo- Optical Instrumentation Engineers. (DOI: 10.1117/1.1413209)