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A Handheld Bias-Switchable Top-Orthogonal-to-Bottom Electrode (TOBE) 2D Array for Ultrasound and Photoacoustic Applications
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- Author / Creator
- Rahim Sobhani, Mohammad
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Ultrasound imaging is a noninvasive and widely utilized technique for soft tissue imaging
in various medical diagnostic and treatment applications. However, conventional
ultrasound machines face challenges regarding imaging speed and quality due to their
small probe size, whereas a bigger probe requires many electrical channels for data
acquisition and processing.
Deploying a fully-connected 2D array in ultrasound probes is critical for achieving
high-quality 2D/3D ultrasound images. However, this approach becomes impractical
when dealing with larger ultrasound arrays. On the other hand, the acquisition and
processing of data with a higher number of channels result in a reduction in imaging
speed. Numerous strategies have been developed to address this issue, employing
multiplexing techniques to limit the number of active elements on arrays. Nevertheless,
these methods still suffer from lower signal-to-noise ratios (SNR) compared to
fully connected arrays, leading to smaller aperture sizes and, consequently, restricted
spatial resolution.
This doctoral dissertation endeavors to overcome these limitations by pioneering
the fabrication of unprecedented large bias-sensitive arrays. The focus is on
top-orthogonal-to-bottom electrode (TOBE) arrays, also called row-column arrays,
which have demonstrated significant potential as an alternative to fully-wired 2D
arrays. They offer a substantial reduction in the number of channels required. Previous
research has shown that innovative imaging techniques involving bias-switchable
TOBE arrays hold promise compared to earlier non-bias-switchable row-column imaging
methods and existing Explososcan approaches. However, they often relied on extensive coherent compounding.
In this work, along with TOBE array fabrication, we introduce ”Ultra-Fast Orthogonal
Row-Column Electronic Scanning” (uFORCES), an ultrafast coded synthetic
aperture imaging method. Unlike its FORCES precursor, uFORCES can
achieve coherent compounding with only a few transmit events, potentially making
it more robust in the presence of tissue motion. We demonstrate that uFORCES
has the potential to offer enhanced resolution when compared to Matrix probes with
beamformers constrained by paraxial approximation. Additionally, unlike current
Matrix probe technology incorporating microbeamforming, uFORCES enables ultrafast
imaging at speeds of thousands of frames per second using only row- and
column-based addressing when coupled with bias-switchable TOBE arrays.
A hand-held form factor of the TOBE array has been developed and successfully
tested on cyst phantom targets, and the results are compared with commercial ultrasound
machines. Also, the feasibility of fabricating a transparent/translucent variant
of the TOBE array has been briefly investigated, along with reporting some preliminary
through-illumination photoacoustic imaging from crossed gold wires. This
bias-switchable TOBE innovation promises to significantly improve ultrasound imaging
systems’ efficiency and image quality. -
- Graduation date
- Spring 2024
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.