Use of Near-Infrared Raman Spectroscopy for Identification of Atherosclerotic Plaques in the Carotid Artery

Objectives: The aim of this work was to identify the presence of atherosclerotic plaque in the human carotid artery using near infrared Raman spectroscopy. Background Data: Atherosclerosis is the most common and serious pathology of the cardiovascular system. Raman spectroscopy is an analytical tool that can be used to gather information about both the morphology and chemical composition of tissues. Methods: A Ti:sapphire laser operating at the near-infrared wavelength of 830 nm pumped by an argon laser was used for excitation of the samples, and the Raman scattering was detected by an optical spectrometer with a liquid-nitrogen-cooled CCD detector. Carotid artery samples were classified into five groups: normal, intimal thickening, fatty plaque, fibrous-fatty plaque, and fibrous-calcified plaque. Results: It was observed that the Raman spectrum of atheromatous plaque was different that that of normal tissue. The spectra of atheromatous plaques had bands due to the presence of cholesterol and its esters, with major bands at 1439 and 1663 cm⁻¹, respectively. In normal tissues a peak related to C-H bending appears at 1451 cm⁻¹. Calcified atheromatous plaques had primary bands at 961 and 1071 cm⁻¹, which were due to the presence of phosphate and carbonate in the accumulated calcium. Peaks were seen at 1451 and 1655 cm⁻¹ in the non-atherosclerotic tissue, which were shifted to 1439 and 1663 cm⁻¹ in the atherosclerotic plaque. Conclusions: Our results indicate that this technique could be used to detect the presence of atherosclerotic plaques in carotid arterial tissue.