Author: Jadon O Buller, Yankun Lang, Liangzhong Xiang, Andrea Paulina Yanez 👨🔬
Affiliation: University of Maryland School of Medicine, University of California, Irvine 🌍
Purpose: With the widespread adoption of electroporation, there is growing interest in deep-tissue electric field monitoring. Electroporation therapy ablates target regions by generating electric fields that induce reversible or irreversible cell membrane poration. Electroacoustic Tomography (EAT), a novel real-time 3D ultrasound imaging method, visualizes the electric field during pulsed energy deposition. Our goal is to help clinicians verify that ablation energy ensures consistent targeted cell fate.
Methods: A three-dimensional matrix array transducer was used to visualize the volumetric electric field distribution with EAT. Square pulses ranging from 600–1000V and 60–150ns were generated and delivered via electrodes, inducing broadband ultrasound waves through various media, including saline and soft tissues of varied homogeneity. A custom 256-channel transducer array connected to a 256-parallel channel DAQ (Photosound) captured the emitted ultrasound waves, and signals were processed in MATLAB. To showcase EAT's real-time capabilities, a large frame buffer was filled by discrete pulse trains from 50–1000V, in 50V increments.
Results: Universal back-projection reconstructions effectively visualize source pressure, with dynamic reconstructions demonstrating clear growth in electric field energy as voltage increases, showcasing EAT's 4D imaging capabilities. Experiments with homogeneous and heterogeneous tissues show visual correlation to experimental results, indicating accurate energy distribution visualization. However, due to the limited-view nature of 3D ultrasound transducers, volumetric reconstructions face depth limitations. To address this, multiple reconstructions from different viewing angles are combined to refine depth information.
Conclusion: Using a planar ultrasound transducer system, experimental electroporation was volumetrically reconstructed for the first time, demonstrating that Electroacoustic Tomography (EAT) is a viable system for deep-tissue volumetric monitoring during therapeutic electroporation. Future in vivo experiments will aim to correlate imaging intensity with quantitative dose.