(she/her/hers)
University of Wisconsin-Madison
Microwave ablation, thermal therapy, thermoacoustic signals, dielectric spectroscopy
Audrey L. Evans received the B.S. degree with distinction in engineering physics from the University of Kansas, Lawrence, KS, USA in 2017. She is currently working toward the Ph.D. degree in electrical engineering at the University of Wisconsin-Madison, Madison, WI, USA. She is a recipient of a National Science Foundation Graduate Research Fellowship (2018-2021). She served as the elected president of the UW-Madison Electrical and Computer Engineering Graduate Student Association for the 2021-2022 academic year. She currently mentors two women undergraduate students in research.
Audrey's research interests include medical applications of applied electromagnetics, acoustics, and dielectric spectroscopy. Her dissertation research focuses on developing microwave-induced thermoacoustic monitoring techniques for microwave ablation. Her approach exploits the already present interstitial ablation antenna to simultaneously ablate tissue with microsecond pulses and generate thermoacoustic signals that can be detected with a surface ultrasound transducer. Audrey's work also includes the characterization of microwave dielectric properties healthy and malignant human lung tissue. She has presented her research through contributed and invited talks at conferences sponsored by the IEEE AP-S, USNC-URSI, IEEE EMB-S, and the Acoustical Society of America.
Upon the completion of her Ph.D. degree, Audrey intends to pursue a career in academic research and teaching. She hopes to continue mentorship of undergraduate women in electrical engineering.
The evolution of microwave-induced thermoacoustic signal characteristics generated during pulsed microwave ablation
Microwave-induced thermoacoustic (TA) signals are of emerging interest for monitoring microwave ablation (MWA) in real-time. TA signals can be generated using an interstitial ablation antenna with a pulsed microwave energy source. When a microsecond microwave pulse is absorbed by tissue, the tissue undergoes a small-scale temperature rise, inducing a thermoelastic expansion that leads to acoustic generation. TA signal characteristics are linked to the dielectric, thermal, and acoustic properties of the local ablation environment. These relevant properties evolve significantly during the ablation process.
We conducted a simulation-based study to examine the evolution of microwave-induced TA signal characteristics generated during pulsed microwave ablation. We experimentally validated our multi-physics simulation model for a spatially uniform temperature profile. Then, using the validated simulation model, we investigated TA signals generated in tissue exhibiting spatially nonuniform temperature profiles that arise during MWA. We find that TA signal characteristics are highly influenced by the local environment temperature within the region of initial TA generation, and thus contains rich information to be exploited for real-time ablation monitoring.
Current work involves experimentally measuring TA signals during MWA in liver tissue using a single-element ultrasound transducer. Our objective is to elucidate the relationship between temperature, tissue coagulation, and TA signal characteristics, with emphasis on tracking the evolution of TA energy and time of arrival.