Endovenous Laser Coagulation: Experimental Modeling with Blood Plasma

The results of the experiments on modeling the processes occurring during endovenous laser coagulation (EVLC, EVLA) using laser radiation with wavelengths λ = 1.55 and 1.94 µm are presented. The application of blood plasma, which is transparent in the visible range and similar to blood in thermophysical properties and absorption coefficient at the selected wavelengths, made it possible to study these processes in detail using video filming. The experiments were carried out using fibers with end and radial radiation output, which are most often used in phlebological practice for EVLC. The results obtained on the vein model showed the following. (i) Heating of the venous wall is mainly due to convection and boiling of the liquid. When a radial fiber is used, additional heating may occur as a result of the direct action of laser irradiation due to the Moses effect. (ii) For laser radiation with λ = 1.94 µm, effective heat transfer begins at lower power levels as compared to λ = 1.55 µm. (iii) Heat transfer in EVLC occurs asymmetrically, predominantly upward. The exception is direct heating by laser radiation due to the Moses effect, which sometimes occurs when using a fiber with a radial output (iv) Periodic events of explosive boiling help to clean the radiation output area from adhered coagulate particles, which cause undesirable carbonization. The intensity of this process increases with increasing radiation power and its absorption coefficient. The results obtained may help to improve the EVLC technology.