We investigate the fundamental time-resolved fluorescence processes induced by excimer lasers in order to develop quantitative criteria for reliable fluorophore characterization. Our approach involves laser-induced time-resolved fluorescence measurements for the purpose of identification of spectro-temporal patterns characteristic of different fluorophores, that can be used as ``signatures'' for unique and unambiguous characterization. We have been able to obtain such characteristic ``signatures'' in the form of spectro-temporal kernels for various fluorophores (collagen, elastin, NAD and NADH) in vitro, which offers the exciting prospect of unambiguous tissue or compound characterization in vivo, when certain practical impediments are overcome. Samples of human arteries at five different levels of calcification were tested and characterized uniquely by spectro-temporal kernel measurements as a demonstration of the efficacy of this approach. This approach was extended to estimation procedures for fluorescence decay time-constants. The initial results suggest potentially useful clinical implications. The reliability of these measurements in vivo is currently examined in order to assess their clinical applicability.
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