Infrared Free Electron Laser Induced Angioplasty for Arteriosclerotic Region of Blood Vessels

In order to estimate the optimum laser conditions for efficient dissociation of cholesterol ester in an arteriosclerotic region of blood vessels, we have investigated the relationship between laser wavelength and power density on cholesterol ester dissociation using a mid infrared free electron laser (MIR‐FEL). In this study, cholesteryl oleate, which is a typical cholesterol ester found in arteriosclerotic regions, was irradiated with 5.75‐μm‐FELs, which cause vibration of ester bonds. Two results were obtained. (1) Ester dissociated depending on the absorption coefficient, and the macropulse duration was shorter than the thermal relaxation time, showing that ester bonds dissociated into carboxylic acid and cholesterol by macropulse‐induced thermal effects without accompanying thermal diffusion, (2) Using a wavelength of 5.75 μm, the maximum ester dissociation ratio was achieved under the optimum laser conditions of a macropulse energy density of 0.4–1.0 J/cm². We conclude that MIR pulsed‐lasers with a wavelength of 5.75 μm can be useful for removal of cholesteryl ester in an arteriosclerotic region of blood vessels.