Antenna optimization goals

Much has been written about microwave ablation antenna designs — more than this post can mention. Most of those designs have been conceived and evaluated with the objectives of (1) reducing reflected power and (2) achieving a pattern of heat deposition that matches the clinical goal (usually a spherical shape). As one example, we designed a dual-slot antenna to balance those two objectives. But does an antenna optimized for normal (unheated) tissue provide the optimal ablation zone after several minutes of heating?

Sevde Etoz’s new study considers this question more closely. She evaluated monopole and dual-slot designs, optimized for low reflected power, high sphericity in heat deposition, and high sphericity in the final ablation (using temperature-dependent tissue property models). Antennas were optimized in simulations and then tested in tissue.

The results were intriguing. Monopole designs optimized for high ablation sphericity were much longer than anything described in the literature. The take-home message is clear: optimizing for the entire heating process – not just reflected power or heating pattern alone – can improve antenna performance. However, based on discordance between simulated and experimental results with the dual-slot antenna, there is more work needed to improve tissue model accuracy if we want to perfect our antenna optimizations.

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