Abstract

We have developed an optothermal model for the interaction of laser light and the tissue of arterial walls and have checked its validity with animal experiments. The mathematical model consists of a laser diffusing tip positioned intraluminally in a cylindrical artery, in which the diffused laser light is incident on a blood–tissue interface at a distance from the tip. A temperature profile throughout the interface is obtained by considering the optical interaction and the thermal conduction and convection of the blood and tissue. The distribution of light in the media is determined using both Beer’s law and the Kubelka-Munk two-flux theory in cylindrical coordinates. For experimental in vivo verification, a diffusing tip was inserted in canine arteries and the temperature profile varied by restricting the volume of blood; this simulated degrees of occlusion to determine the influence of blood flow on heat transport. The measured temperature profiles compared favorably to the theoretical results. Temperature profiles are also predicted for a water-filled lumen. The theoretical model will be useful in predicting the depth of ablation and extent of normal tissue damage during laser angioplasty treatment of atherosclerosis.

© 1989 Optical Society of America

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