Dual applicator thermal ablation at 2.45 GHz: a numerical comparison and experiments on synchronous versus asynchronous and switched-mode feeding

Abstract

Purpose: This paper compares the results obtained with numerical simulations and ex vivo experiments involving a dual applicator microwave thermal ablation system operating at a 2.45 GHz frequency, both in synchronous and asynchronous modes. Our purpose was to demonstrate that at this frequency an asynchronous or switched-mode system performs essentially as well as the synchronous one, in spite of the prevailing belief that coherence would assure better thermal (TH) synergy. Numerical analysis: The calculations of temperature fields were based on the Pennes bioheat equation, taking into account the effects of blood perfusion by means of a full-wave 3D simulator that allows numerical electromagnetic (EM) and TH analyses. Materials and methods: Experiments were done using a 100 W microwave (MW) power generator and a fast switched-mode sequential ‘active’ power splitter. By adding a further passive power splitter we arranged a test bed for an accurate experimental comparison of synchronous versus switched-mode TH ablations. Results: The experimental ablation zones produced by a dual applicator array on ex vivo swine tissue corresponded well with the simulated ones, confirming that the simplifications assumed in the full-wave analysis were compatible with the aim of our work. Conclusions: Numerical simulations and experiments show that at a 2.45 GHz industrial, scientific and medical (ISM) frequency, synchronous, asynchronous and switched-mode multi-probe systems are substantially equivalent in terms of ablative performance. Moreover, the switched-mode solution offers simpler operation along with lesser sensitivity to the placement of applicators in the tissue.

• Asynchronous feeding
• fast sequential switching
• microwave thermal ablation
• multi-applicator system
• synchronous feeding

Acknowledgements

We would like to thank the Centro Interdipartimentale Sviluppo di Nuove Tecnologie Mini-invasive in Chirurgia Oncologica for the highly skilled support they provided in the ex vivo experiments.

Declaration of interest

Cosimo Ignesti discloses his current cooperation with Biomedical, of Florence, Italy, to actively continue the project and its related studies. Guido Biffi Gentili has no relevant relationship to disclose. The authors alone are responsible for the content and writing of the paper.