Microwave-induced thermacoustic signal characteristics during pulsed microwave ablation

Abstract

Microwave ablation (MWA) is a minimally invasive thermal therapy in which an interstitial antenna delivers microwave power locally to diseased tissue to cause cell death. Thermoacoustic (TA) signals can be generated with internally pulsed microwave energy that simultaneously ablates tissue. When pulsed microwave energy is absorbed by tissue, the tissue undergoes an incremental temperature rise which leads to thermoelastic expansion and the generation of an acoustic wave that can be detected by ultrasound transducers. The characteristics of the TA signals are linked to features of the local ablation environment from which they are generated, and thus can be exploited for ablation monitoring. In this experimental and computational study, we examine the fundamental characteristics of TA signals generated from within the ablation zone and observe how the TA signal changes as the ablation zone evolves. We performed pulsed microwave heating experiments in non-coagulating and coagulating liquids and measured the resulting TA signals. We also performed multiphysics simulations of the MWA process that encompass the electromagnetic, thermal, and acoustics physics. This study provides insights into TA signal generation and propagation during MWA and establishes the feasibility of using the TA signals for ablation monitoring.