Medical application of an infrared free-electron laser: selective removal of cholesterol ester in carotid artery atheromatous plaques

Abstract

Object The purpose of this study was to determine the effectiveness of infrared free-electron laser (FEL) irradiation of cholesterol esters in human carotid artery (CA) atheromas. Methods The degradation of cholesterol ester was estimated from changes in the infrared absorption spectra acquired using microscopic transmission Fourier transform infrared spectroscopy. An FEL emitting radiation at 5.75-μm wavelengths and a power density of 15.9 W/cm2 was used to treat intimal slices of extirpated human arterial atherosclerotic plaques. Peak signals derived from an ester bond of cholesterol ester decreased in height as irradiation time increased and disappeared completely after 180 seconds. No other change was observed in the infrared absorption spectrum after 180 seconds of irradiation, and no histological damage was noted. Conclusions The authors concluded that FEL irradiation can remove cholesterol ester selectively from human atheromatous CA plaques. This novel technique differs from previous approaches involving conventional lasers.