Microwave Antenna Design for Cardiovascular Applications: A Comparison Between a Balanced and Unbalanced Microwave Ablation Antenna

Objective:To determine whether an irrigatedunbalanced antenna can create larger ablations than a conventional microwave antenna without overheating.Method:The microwave and ablation characteristics of a previously published multi-ring slot array (MRSA) ablation antenna, optimized for intravascular environments, were compared with a dielectric-insulated monopole antenna with no matching or balancing elements, creating the unbalanced monopole antenna. The two antennae were numerically simulated in an intravascular environment and tested inside a gel phantom for five repetitions for comparison. Each antenna assembly was900 mmlong, with a2.45 GHzablatingfrequency, with a microwave input power of60 Wfor120 svia a patient cable.Results:Gel experiments were consistent with numerical simulations, with the unbalanced monopole antenna possessing better microwave and ablative characteristics than the MRSA in a biological environment. Microwave input power to the device connector was attenuated from60 Wto40 Wdue to patient cable losses. Removing matching elements improved input impedance at the test plane (Real, 52.20±5.90 \;Ω$vs. 74.22$±43.25 \;Ω, p = 0.05648; Imaginary, −23.50±2.63 \;Ω$vs. 14.92$±51.10 \;Ω, p = 0.1333) and the return loss (−12.79±0.45 dB$vs. 6.51$±0.25 dB, p =2.521 × 10⁻⁷). The unbalanced monopole antenna created wide (18.28±0.57 mm$vs. 13.38$±0.60 mm, p =2.482 × 10⁻⁵) and deeper (11.87±0.88 mm$vs. 9.41$±0.98 mm, p =1.616 × 10⁻²) ablation lesions than the MRSA.Clinical Impact:Removing elements from an MRSA created an unbalanced monopole antenna that creates larger ablation lesions with improved microwave characteristics.