Determinants of the fluorescence emission spectrum of atheromatous plaques treated with haematoporphyrin in vitro

Studies were carried out on atheromatous plaques which had been incubated with the fluorescent dye haematoporphyrin. By varying the wavelength of excitation, it was possible to obtain fluorescence signals from different depths in plaque, since enhanced tissue penetration occurs when the wavelength of exciting light is increased. Moreover, the presence of ulcerated regions altered both excitation and emission spectra. These results suggest that corresponding measurements using laser/fibre-optic systems may be used to characterize plaques in vivo.