INSTITUTE OF PHYSICS PUBLISHING PHYSICS IN MEDICINE AND BIOLOGY Phys. Med. Biol. 46 (2001) 1665–1678 www.iop.org/Journals/pb PII: S0031-9155(01)19136-0 Photothermal coagulation of blood vessels: a comparison of high-speed optical coherence tomography and numerical modelling Jennifer Kehlet Barton 1 , Andrew Rollins 2 , Siavash Yazdanfar 3 , T Joshua Pfefer 4 , Volker Westphal 3 and Joseph A Izatt 2,3 1 Division of Biomedical Engineering, The University of Arizona, 1230 E. Speedway Blvd, Tucson, AZ 85721, USA 2 Department of Medicine, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106, USA 3 Department of Biomedical Engineering, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106, USA 4 Wellman Laboratories of Photomedicine, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA E-mail: barton@u.arizona.edu Received 16 November 2000 Abstract Optical-thermal models that can accurately predict temperature rise and damage in blood vessels and surrounding tissue may be used to improve the treatment of vascular disorders. Verification of these models has been hampered by the lack of time- and depth-resolved experimental data. In this preliminary study, an optical coherence tomography system operating at 4–30 frames per second was used to visualize laser irradiation of cutaneous (hamster dorsal skin flap) blood vessels. An argon laser was utilized with the following parameters: pulse duration 0.1–2.0 s, spot size 0.1–1.0 mm, power 100–400 mW. Video microscopy images were obtained before and after irradiations, and optical- thermal modelling was performed on two irradiation cases. Time-resolved optical coherence tomography and still images were compared with predictions of temperature rise and damage using Monte Carlo and finite difference techniques. In general, predicted damage agreed with the actual blood vessel and surrounding tissue coagulation seen in images. However, limitations of current optical-thermal models were identified, such as the inability to model the dynamic changes in blood vessel diameter that were seen in the optical coherence tomography images. 1. Introduction Laser irradiation is the modality of choice for the treatment of vascular disorders, including port wine stains (PWS), telangiectasias and superficial spider veins (van Gemert et al 1995, 0031-9155/01/061665+14$30.00 © 2001 IOP Publishing Ltd Printed in the UK 1665