Do fluorescence decays remitted from tissues accurately reflect intrinsic fluorophore lifetimes?

Fluorescence spectroscopy and imaging methods, including fluorescence lifetime sensing, are being developed for noninvasive tissue diagnostics. The purpose of this study was to identify and quantify those factors affecting the accurate recovery of fluorophore lifetimes from inhomogeneous tissues in vivo. A Monte Carlo code was developed to numerically simulate time-resolved fluorescence measurements on layered epithelial tissues. Simulations were run with experimental parameters matching previously reported clinical studies in the gastrointestinal tract. The results demonstrate that variations in fluorescence decay time as large as those detected clinically between normal and premalignant tissues (approximately 2 ns) could be simulated by variations in tissue morphology or biochemistry, even when intrinsic fluorophore lifetimes were held constant.