Change in laser-induced arterial fluorescence during ablation of atherosclerotic plague

Analysis of the change in arterial fluorescence during plaque ablation may provide the basis for developing a fluorescence-guided ablation system capable of selective plaque ablation without risk of vessel perforation. Accordingly, fluorescence spectra were recorded from 91 normal and 91 atherosclerotic specimens of cadaveric human aorta. The ratio of the laser-induced fluorescence intensity at 382 nm to 430 nm (LIF ratio) was capable of classifying these specimens with an 89% accuracy with a threshold value of 1.8 (atherosclerotic greater than or equal to 1.8, normal less than 1.8). To characterize the change in fluorescence during plaque ablation, mechanical plaque ablation with a cold microtome was performed on 16 atherosclerotic aortic specimens. Fluorescence spectra were recorded serially after each 100 microns of plaque ablation; recordings revealed a change in fluorescence spectra from atherosclerotic to a normal pattern. With an LIF ratio of 1.8 to signal termination of plaque ablation, 15 of the atherosclerotic plaques had a residual plaque thickness less than 200 microns; one specimen had a residual plaque thickness of 300 microns. No specimen demonstrated ablation of the media. There was a statistically significant correlation between LIF ratio and plaque thickness (r = .73, P less than .001), but considerable variation in LIF ratio existed at each thickness. Therefore, laser-induced fluorescence spectroscopy is capable of discriminating atherosclerotic from normal aorta and of signaling completion of plaque ablation.