Laser‐induced fluorescence: III. Quantitative analysis of atherosclerotic plaque content

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Abstract
Background and Objective: Laser‐induced fluorescence (LF) spectroscopic analysis of the chemical composition of atherosclerotic plaque was examined. Study Design/Materials and Methods: The intima of 18 dog aortas was injected with chemical compounds found in atherosclerotic plaque. Spectra were recorded in air prior to and after injection of collagens I, III and IV, elastin, cholesterol, triglyceride, and β‐nicotinamide adenine dinucleotide (NADH). Results: Significant changes in LF intensity were detected after injection of collagens I and III, cholesterol and elastin in thoracic aorta (P < 0.001), but not with triglyceride or NADH. Minor changes were detected in abdominal aorta. Multiple regression analysis of LF intensity ratios demonstrated a clear correlation with the quantity of injected collagens I (R2 = 0.90–0.99) and III (R2 = 0.84–1.0), cholesterol (R2 = 0.72–0.76), and triglyceride (R2 = 0.68–0.80) in both thoracic and abdominal aorta. The correlation between LF and atherosclerotic plaque composition was confirmed in a rooster model of atherosclerosis where multiple regression analysis predicted the measured aortic cholesterol (R2 = 0.78) and triglyceride content (R2 = 0.96). Conclusions: (1) Fluorescence spectra recorded from dog aorta were significantly altered by injection of collagens I and III, cholesterol, and elastin. (2) LF may allow quantitative assessment of plaque chemical content.