Laser Raman spectrum of calcified human aorta.

Raman spectra of highly calcified areas of human aorta were obtained using long wavelength excitation at 740 nm to minimize background fluorescence interference. Raman spectra resembling that of hydroxyapatite were obtained for segments of highly calcified aorta that were thawed frozen samples, from which the surface layer had been removed, or were dried. These are the first reported spectra obtained in air or in normal saline solution showing the hydroxyapatite peak in calcified plaque for samples which were untreated except for freezing, which is encouraging for the application of Raman spectroscopy as a method of detection of plaque during laser angioplasty. Spectra obtained from calcified aorta using excitation at 514.5 nm did not show evidence of the hydroxyapatite band because of the severe interference by background fluorescence generated at this wavelength.