Laser induced fluorescence as a diagnostic tool in atherosclerosis

Experiments on atherosclerotic plaque diagnosis were carried out using laser induced fluorescence (LIF). Different excitation wavelengths were tested: 488 nn and 457.9 nm of a c.w. Ar+ laser as well as 476 Mn and 407 nn of a c.w. Kr+ laser. Over 15 samples were examined and several spectra were obtained from each sample. Results were crossed-examined with conventional clinical techniques, such as histopathological diagnosis, which showed three main components of the atherosclerotic plaque: fibrous tissue, lipid constituents and calcified plaque. An effort was made to distinguish the composition of the sample from the obtained spectra. Fluorescence spectra corresponding to calcified plaque present their maximum in the area of 530 nn - 550 mn. However, there was not observed a specific wavelength where spectra corresponding to fibrous tissue and lipid constituents present maximum. Full width half maximum (FWHM) of the fluorescence spectra was also measured and the ratio of the fluorescence intensity at 600 nn over the intensity at 576 nm, I(600)/I(576), was calculated.