Fluorescent heterogeneities in turbid media: limits for detection, characterization, and comparison with absorption

摘要

The fundamental limits for detection and characterization of fluorescent (phosphorescent) inhomogene-ities embedded in tissuelike highly scattering turbid media are investigated. The absorption and fluorescence contrast introduced by exogenous fluorophores are also compared. Both analyses are based on practical signal-to-noise ratio considerations. For an object with fivefold fluorophore concentration and lifetime contrast with respect to the background tissue, we find the smallest detectable fluorescent object at 3-cm depth in tissuelike turbid media to be ～0.25 cm in radius, whereas the smallest characterizable object size is ～0.75 cm in radius, given a model with 1% amplitude and 0.5° phase noise. We also find that, for fluorescence extinction coefficients ε ≤ 0.5×10↑(5) cm↑(-1) M↑(-1), the fluorescence measurement mode is superior to the absorption mode for detecting an inhomogeneity. The optimal choice of modulation frequency for the frequency-domain fluorescence measurements is also discussed. # 1998 Optical Society of America OC1S codes: 170.3650, 170.5270, 260.2570, 290.1990, 290.4210, 290.7050.