Thermoacoustic Thermometry Assisted Focused Microwave Therapy

Abstract

In recent years, there has been a progressive trend towards minimally invasive methods with less morbidity and better cosmetic appearance for treating breast cancer. Non-invasive focused microwave therapy (FMT) is a cutting-edge approach for treating breast cancer that employs an array of antennas to focus electromagnetic energy deep into tissue at microwave frequencies. FMT offers better penetration and larger ablation zones (> 2 cm) than interstitial laser therapy (ILT), radiofrequency ablation (RFA), and cryoablation. In addition, because FMT depends on tissue dielectric properties, microwaves preferentially heat and damage high-water content breast carcinomas instead of healthy breast tissue. We develop and evaluate a focused microwave therapy (FMT) system and integrate it with thermoacoustic thermometry (TAT) for mapping temperature, quantifying the heat zone and guiding the delivery of focused heat. The thesis showcases the development of actual antenna arrays to transmit microwave power while the excitation signals are derived from the time-reversal (TR) beamforming algorithm to generate power distributions and thermal profiles in the patient-specific breast models. The first study based on 2D antenna arrays and patient-specific breast models demonstrates a nuanced analysis of the intricacies of the TR beamforming algorithm. Time reversal beamforming performs significantly well within a heterogeneous non-dissipative environment. An improved FMT approach for breast cancer treatment, overcoming the limitations of previously analyzed techniques, is also introduced. In this approach, a multi-ring 3D array is developed and FMT simulation is conducted in a 3D environment that allows targeting microwave power to tumors located at various locations by using a fixed antenna array. A figure of merit is identified which demonstrates significant improvement from 2D to 3D time reversal in heterogeneous breast as compared to homogeneous breast model. A proof of concept prototype is then developed for validating the time-reversal beamforming algorithm. The experimental system is implemented in two phases, where the first phase corresponds to a 4-element one-ring prototype, and the second phase is the three-dimensional multi-ring array of 32 patch antennas operating at the ISM frequency band (915 MHz). Additionally, to control thermal dosage at tumor location, while maintaining normal temperatures in healthy tissue and monitoring the progress during treatment, Thermoacoustic Thermometry (TAT) assisted FMT prototype is developed.