<title>Fluorescence characteristics of atherosclerotic plaque and malignant tumors</title>

Abstract

Two series of investigations utilizing laser-induced fluorescence (LIF) in characterizing diseased tissue are presented. In one in vitro investigation we studied the fluorescence from normal and atheroscierotically diseased arteries. In another, clinical, study we investigated the fluorescence in vivo from superficial urinary bladder malignancies in patients who had received a low-dose injection of Hematoporphyrin Derivative (HpD). Additionally, the fluorescence properties of L-tryptophan, collagen-I powder, elastin powder, nicotinamide adenine dinucleotide and i3-carothene were investigated and compared with the spectra from the tissue samples. A nitrogen laser (337 nm) alone or in connection with a dye laser (405 urn) was used together with an optical multichannel analyzer (OMA) to study the fluorescence spectra. The fluorescence decay characteristics of atherosclerotic plaque were examined utilizing a mode locked argon ion laser, synchronously pumping a picosecond dye laser. A fast detection system based on photon counting was employed. The fluorescence decay curves were evaluated on a PC computer allowing up to three lifetime components to be determined. A fluorescence peak at 390 nm in fibrotic plaque was identified as due to collagen fibers, while a fluorescence peak at 520 nm was connected to i3-carothene. The in vivo measurements of urinary bladder malignancies were performed with the optical fiber of the OMA system inserted through the biopsy channel of a cystoscope during the diagnostical procedure. The spectral recordings from urinary bladders, obtained at 337 nm and 405 nm excitation, revealed fluorescence features which can be used to demarcate tumor areas from normal mucosa. The fluorescence emission might also be useful to characterize different degrees of dysplasia.

Discrimination of Human Coronary Artery Atherosclerotic Lipid-Rich Lesions by Time-Resolved Laser-Induced Fluorescence Spectroscopy

“…In addition, by showing that parameters derived from time-resolved spectra can enhance the discrimination of atherosclerotic lesions, this study demonstrates that the TR-LIFS technique can be used for characterization of arterial tissue and advances a paradigm that may be applicable for other disease states, such as neoplasms. Baraga et al 8 Andersson-Engels et al 15 …”

“…Also, 2 lipopigments, ceroid and carotenoids, were related to atherosclerotic lesion fluorescence emission. 15,31,32 Ceroid, an end product of lipoprotein oxidation, is found in macrophages and in lesions with lipid-rich necrotic cores. Carotenoids are present in lipid-rich lesion cores.…”

“…Tryptophan fluorescence induced by excitation wavelengths Ͻ310 nm was shown to strongly influence the emission of arterial wall at wavelengths Ͻ360 nm, 8 but it had minimal influence on the emission at Ͼ360 nm. 8,15 Calcium exhibits sharp fluorescence peaks in the 350-to 650-nm range on 308-nm excitation, 28 but its emission on longer excitation wavelengths (325 nm) was not reliably detected. 25 Consequently, these components are less likely to significantly influence the fluorescence characteristics reported in our study (excitation 337 nm).…”

“…Baraga et al 8 Laifer et al 25 Andersson-Engels et al 15 Maarek et al Baraga et al 8 Laifer et al 25 Andersson-Engels et al 15 Maarek et al 17 Collagen Yan et al 26 Laifer et al 25 Marcu et al 27 Cholesterols Morguet et al 28 Yan et al 26 Laifer et al 25 Marcu et al 29 Maarek et al 37 Cholesteryl …”

Fluorophore Analyses of Vulnerable Atherosclerotic Plaque and Its Early Detection

“…TIME-RESOLVED FLUORESCENCE SPECTROSCOPY FOR TISSUE DIAGNOSIS TR-LIFS, which uses a time-domain technique and laser excitation, was first introduced by Baraga et al [7] in 1989 and further investigated by Andersson-Engels et al in the early 1990s [8,9]. As the lifetime defines the time available for the fluorophore to interact with its environment, time-resolved technique is sensitive to micro-environmental parameters in tissue, such as pH, enzymatic activity and temperature.…”