Photothermal coagulation of blood vessels: a comparison of high-speed optical coherence tomography and numerical modelling

Optical-thermal models that can accurately predict temperature rise and dam age in blood vessels and surrounding tissue may be used to improve the trea tment of vascular disorders. Verification of these models has been hampered by the lack of time- and depth-resolved experimental data. In this prelimi nary study, an optical coherence tomography system operating at 4-30 frames per second was used to visualize laser irradiation of cutaneous (hamster d orsal skin flap) blood vessels. An argon laser was utilized with the follow ing parameters: pulse duration 0.1-2.0 s, spot size 0.1-1.0 mm, power 100-4 00 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 dif ference techniques. In general, predicted damage agreed with the actual blo od vessel and surrounding tissue coagulation seen in images. However, limit ations of current optical-thermal models were identified. such as the inabi lity to model the dynamic changes in blood vessel diameter that were seen i n the optical coherence tomography images.