Endovenous Laser Treatment for Occlusion of Varicose Veins

Endovenous laser treatment (ELT) is a minimally invasive technique that uses laser energy to treat varicose veins. An optical fiber is inserted under the guidance of ultrasound and laser light is shone into the interior of the varicose vein. The optical fiber is withdrawn at a constant rate as, simultaneously, contraction of the vein occurs in response to heating induced by laser light exposure. Our goal is to model heat transfer between the laser and the vein wall and optimize laser power and pullback speed for ELT. Modeling was performed in COMSOL using Navier-Stokes fluid flow and transient state heat transfer. The problem geometry was simplified to a 2D axisymmetric model consisting of a lumen, vein wall and perivenous tissue. By modeling the ELT process, we were easily able to observe temperature changes and quantify cell death, a measure of tissue damage, in the vein wall and perivenous tissue while manipulating laser power and pullback speed. We analyzed cell death in the vein wall, where permanent damage is desirable, as compared to the perivenous tissue, where it is not, at various laser powers and pullback speeds. Our results indicate that several optimal laser power and pullback speed combinations exist for different criteria. For minimum damage to the perivenous tissue we recommend a laser power of 15 W and a pullback speed of 2 mm/s. If damage to approximately 100 mm2 of perivenous tissue is acceptable, the maximum amount of vein wall tissue can be destroyed using a laser power of 30 W and a pullback speed of 4 mm/s. Our model supports the effectiveness of the ELT procedure and enhances discussions on best treatment methods. Optimization of laser power and pullback speed improves the efficacy of the treatment and decreases risk associated with damage to the perivenous tissue. By improving the efficacy and safety of ELT we hope to improve treatment options for the vast number of people suffering from varicose veins. Our results may also be used as foundation for further comparative studies of ELT procedure