Experimental Monitoring of Microwave-Induced Thermoacoustic Signals Generated During Pulsed Microwave Ablation

We experimentally investigate the evolution of microwave-induced thermoacoustic signals generated during pulsed microwave ablation in bovine liver tissue. Using an X-band interstitial ablation antenna and a microsecond pulsed microwave source operating at ~9.4 GHz with an average power of 5 - 10 W, we simultaneously heat tissue and generate thermoacoustic signals. We conduct ablation experiments in both fresh liver tissue as well as boiled liver tissue to decouple the impact of temperature and tissue coagulation on thermoacoustic signal characteristics. We find that the time of arrival of the thermoacoustic signals decreases over the course of microwave ablation due to the change in the temperature-dependent speed of sound as well as tissue shrinkage. Thus, the thermoacoustic time of arrival may be used to monitor microwave ablation in real-time.