Treatment of leg veins with indocyanine green and lasers investigated with mathematical modelling.

PURPOSE: The treatment of leg veins is routinely performed in clinical practice using near infrared (NIR) lasers. However, due to low absorption of NIR light in blood vessels, the clinical results are still suboptimal. The absorption of the NIR light can be significantly increased with intravenous introduction of an indocyanine green (ICG) dye. In this work a mathematical model was used to delineate clinically valid settings for ICG and NIR lasers for the treatment of leg veins.

METHODS: A finite element commercial package was used to simulate light propagation and absorption and heat generation in a skin-like geometry. The simulations were conducted for 755 nm and 810 nm light wavelengths, which are emitted by alexandrite and diode lasers, respectively. Five different laser settings, six different vessel diameters (0.1-2 mm) and three ICG concentrations (0, 1 or 2 mg/kg body weight (BW)) were used to calculate the temperature field spatial distribution as a function of time.

RESULTS: The diameter of the blood vessels affects the temperature distribution during and following laser irradiation, with and without ICG. Adding 1 or 2 mg/kg bw of ICG will cause significant temperature increase (15-35°C, p ≤ 0.001) in blood vessels with a diameter of 0.1-1 mm and steep temperature gradients in 1.5-2 mm diameter blood vessels.

CONCLUSIONS: Intravenous application of ICG at 1-2 mg/kg may improve coagulation of blood vessels with 0.1-1 mm diameter irradiated with either a diode or alexandrite laser. This should be confirmed with clinical trials in the near future.