Numerical modeling of the impact on the vascular wall during endovenous ultrasound treatment

The article describes the research of a new treatment method of lower limb varicose vein using low-frequency ultrasound. To study the effectiveness of this method we analyzed the interaction between the ultrasound instrument and the venous wall and defined the mechanisms of action during endovenous ultrasound treatment (EUT): thermal, mechanical, and chemical. We developed three models to study the impact of different combinations of mechanisms of action on varicose venous wall. The first model describes the endothelial cell layer delamination during mechanical mechanism. Other models investigate the two main modes of EUT. The EUT mode 1 models mechanical and thermal mechanisms of action, while the EUT mode 2 also studies the impregnation process of sclerosant. During the finite element analysis of both EUT modes, the instrument with an axisymmetric tip was inserted inside the vein with varying blood flow velocity. The amplitude of ultrasound oscillations required for the endothelial cell layer delamination was equal to 40 µm. The ultrasound exposure induced the impregnation enhancement of sclerosant up to 6 times. The temperature distribution and the necrotic tissue fraction of the venous wall were also evaluated. The results of the study demonstrate uniform irreversible damage to the venous wall for both EUT modes.