Simultaneous microwave ablation using multiple antennas in explanted bovine livers: relationship between ablative zone and antenna.

Purpose: Our purpose was to determine the optimal antenna spacing to achieve large ablative zones without indentations when microwave ablation is performed with simultaneous activation of two or three antennas.

Materials and methods: Microwave ablation was performed with single-antenna activation and simultaneous activation of two or three antennas with a spacing of 1.5, 2.0, 2.5, or 3.0 cm in explanted bovine livers. Microwave energy was applied for 10 min with a power of 45 W. The shapes and sizes of the ablative zones created were recorded and compared.

Results: The shape of the ablative zone was ellipsoid in the axial plane (along the antenna axis) and spherical in the transverse plane (perpendicular to the antenna axis) in single-antenna ablation. The ablative zones were spherical or ellipsoid in both the axial and transverse planes in two-and three-antenna ablation with an antenna spacing of 2.0 cm or less. Indentations were observed between the ablative zones created by the antennas when the spacing was 2.5 cm or more, reducing the minimum transverse diameter. When two-or three-antenna ablation was performed with a spacing of 2.0 cm or less, the axial and minimum transverse diameters were significantly larger than in single-antenna ablation. The largest volume (almost two or three times the single-activation volume) was achieved in two-or three-antenna ablation with an antenna spacing of 2.0 cm.

Conclusion: We found that simultaneous microwave ablation using multiple microwave antennas creates large ablative zones without indentations when multiple antennas are activated with an antenna spacing of 2.0 cm or less.