Optical density of healthy human arterial vessel wall and atheromatous plaque as a basis for pulsed laser angioplasty

Transmissions spectra of healthy human arterial vessel wall (intima, media, adventitia), lipid plaque as well as calcified plaque were obtained from 245 autopsy specimens (25 patients) by znicrospectrophotometry (25 jim sections, wavelength 240 nm - 1070nm). Lipid plaques showed moderately increased optical density over normal tissue in the visible and near infrared spectral range with maximal values in the blue spectral range (440 nm to 530 nm). At these wavelengths, extinction was about a factor of S compared to intima, a factor of 3 higher than in media, and a factor of 7 higher with respect to adventitia. Over the whole spectral range investigated, calcified plaque exhibited a significantly higher optical density compared to all layers of normal vessel wall. The maximum differences were found between 300 and 450 am for intima (6 to 7 fold), between 440 and 1070 for media (3 fold) and above 550am for adventitia (10 to 12 fold).