Effects of blood-flow velocity and direction on coagulation zone symmetry induced by microwave ablation using ECO antenna

BACKGROUND AND OBJECTIVE: Microwave ablation is a well-established therapy for liver tumors, but its efficacy is strongly influenced by blood perfusion. Most computational studies simplify perfusion as an isotropic sink, neglecting flow orientation. This work introduces the Antenna-Blood flow Relative Angle (ABRA) to quantify the effects of flow direction and velocity on ablation zone geometry using a commercial ECO Ceramic 14 G antenna. METHODS: bovine liver experiments were performed under standardized conditions and used to calibrate and validate a computational model. The antenna was reverse engineered to reproduce its electromagnetic and thermal characteristics. A local thermal non-equilibrium framework incorporating directional perfusion was implemented to simulate microwave ablation for different ABRA values and blood flow velocities. RESULTS: Both blood flow orientation and velocity significantly affected lesion morphology. Upward-directed flow (0° ABRA) caused elongation of the coagulation zone along the flow axis, while downward-directed flow (180° ABRA) produced more compact and symmetric lesions. Increasing flow velocity amplified these effects, displacing the lesion and reducing its sphericity. Computational results showed strong agreement with experimental measurements, with mean discrepancies below 4%. CONCLUSIONS: The findings demonstrate that ABRA and perfusion velocity are key determinants of ablation zone size, shape, and symmetry. Incorporating these parameters into computational modeling and treatment planning could improve lesion predictability and completeness, supporting more personalized and effective strategies for liver tumor ablation.