Purpose: Near-infrared Raman spectroscopy provides an important new means of analyzing the chemical composition of the arterial wall. The objective of this study was to show that Raman spectroscopy can be used to evaluate the lipid and calcium salt contents of human peripheral arteries. The results extend a recently developed Raman-based method for analyzing the chemical composition of coronary arteries.Methods and Results: We studied 167 segments of carotid and femoral artery wall in various pathologic states. The Raman spectra from these samples was accurately modeled. The resulting chemical concentrations were compared with the amounts of cholesterol and calcium mineral determined at histologic evaluation by an experienced cardiovascular pathologist. Strong correlations between spectroscopic measurements and morphologic findings were demonstrated and validated the applicability of the method to peripheral arteries.Conclusions: Raman spectroscopy can provide reliable histochemical information about peripheral and coronary arteries. Such information may help identify rupture-prone plaques before the onset of symptoms and allow aggressive and directed intervention. Accurate knowledge of the chemical composition of a lesion may be useful in selecting the most appropriate treatment.

Healthy artery tissue is composed of three layers: intima, media, and adventitia. With the onset of atherosclerosis, fatty and fibrous deposits build up in the intimai layer, narrowing the lumen for blood flow, leading to stroke and heart attack. Laser radiation of modest power can vaporize these deposits, restoring normal flow [l]. This can be accomplished without open heart surgery, using a catheter containing optical fibers to deliver the laser light to the obstruction. However, without appropriate control, arterial perforation can occur. As part of our efforts in this area [2, 3], we are developing a spectroscopic guidance system to diagnose the presence and control the removal of atherosclerotic blockages.

Controlled delivery of light is necessary for the precise removal of tissue in laser angiosurgery. We describe an optical fiber laser catheter incorporating a transparent, protective optical shield which provides such control. Tissue removal data characterizing the performance of the device are presented.