Characterization of the site dependency of normal canine arterial fluorescence

Abstract

The difference in fluorescence between normal and atherosclerotic artery has been proposed as a feedback mechanism to guide selective laser ablation of atherosclerotic plaque. This fluorescence difference is due to the relative difference in collagen:elas-tin content of normal artery and atherosclerotic plaque. However, normal arteries have site-dependent variation in collagen: elastin content which may affect their fluorescence spectra. To evaluate the site dependency of normal arterial fluorescence, helium-cadmium (325 nm) laser-induced fluorescence spectra were analyzed in vitro from the ascending aorta, abdominal aorta, and carotid, femoral, renal, and coronary arteries (N=57) of 12 normal mongrel dogs. Elastin and collagen contents were determined for a subset of these arteries (N=15). The spectral width of normal arterial Fluorescence varied by site and correlated with the measured collagen:elastin content at each site (r=-0.84, P < 0.005). Fluorescence spectra were decomposed into collagen and elastin spectral components by using a linear model with a least-squared error criterion fit. The derived collagen and elastin spectral coefficients correlated with the measured collagen and elastin tissue content (r=0.75 and 0.83 respectively, P < 0.005). Thus, the fluorescence spectra of normal arteries is site dependent and correlates with the collagen:elastin content. Therefore, spectral feedback algorithms for laser angioplasty guidance must be site specific.