A Handheld Bias-Switchable Top-Orthogonal-to-Bottom Electrode (TOBE) 2D Array for Ultrasound and Photoacoustic Applications
Creators: Rahim Sobhani, Mohammad
Publisher: name: University of Alberta Library
Year: 2024

<p>Ultrasound imaging is a noninvasive and widely utilized technique for soft tissue imaging<br>
in various medical diagnostic and treatment applications. However, conventional<br>
ultrasound machines face challenges regarding imaging speed and quality due to their<br>
small probe size, whereas a bigger probe requires many electrical channels for data<br>
acquisition and processing.<br>
Deploying a fully-connected 2D array in ultrasound probes is critical for achieving<br>
high-quality 2D/3D ultrasound images. However, this approach becomes impractical<br>
when dealing with larger ultrasound arrays. On the other hand, the acquisition and<br>
processing of data with a higher number of channels result in a reduction in imaging<br>
speed. Numerous strategies have been developed to address this issue, employing<br>
multiplexing techniques to limit the number of active elements on arrays. Nevertheless,<br>
these methods still suffer from lower signal-to-noise ratios (SNR) compared to<br>
fully connected arrays, leading to smaller aperture sizes and, consequently, restricted<br>
spatial resolution.<br>
This doctoral dissertation endeavors to overcome these limitations by pioneering<br>
the fabrication of unprecedented large bias-sensitive arrays. The focus is on<br>
top-orthogonal-to-bottom electrode (TOBE) arrays, also called row-column arrays,<br>
which have demonstrated significant potential as an alternative to fully-wired 2D<br>
arrays. They offer a substantial reduction in the number of channels required. Previous<br>
research has shown that innovative imaging techniques involving bias-switchable<br>
TOBE arrays hold promise compared to earlier non-bias-switchable row-column imaging<br>
methods and existing Explososcan approaches. However, they often relied on extensive coherent compounding.<br>
In this work, along with TOBE array fabrication, we introduce ”Ultra-Fast Orthogonal<br>
Row-Column Electronic Scanning” (uFORCES), an ultrafast coded synthetic<br>
aperture imaging method. Unlike its FORCES precursor, uFORCES can<br>
achieve coherent compounding with only a few transmit events, potentially making<br>
it more robust in the presence of tissue motion. We demonstrate that uFORCES<br>
has the potential to offer enhanced resolution when compared to Matrix probes with<br>
beamformers constrained by paraxial approximation. Additionally, unlike current<br>
Matrix probe technology incorporating microbeamforming, uFORCES enables ultrafast<br>
imaging at speeds of thousands of frames per second using only row- and<br>
column-based addressing when coupled with bias-switchable TOBE arrays.<br>
A hand-held form factor of the TOBE array has been developed and successfully<br>
tested on cyst phantom targets, and the results are compared with commercial ultrasound<br>
machines. Also, the feasibility of fabricating a transparent/translucent variant<br>
of the TOBE array has been briefly investigated, along with reporting some preliminary<br>
through-illumination photoacoustic imaging from crossed gold wires. This<br>
bias-switchable TOBE innovation promises to significantly improve ultrasound imaging<br>
systems’ efficiency and image quality.</p>