Sound speed estimation and phase-aberration correction for medical ultrasound imaging
Abstract/Contents
- Abstract
- Pulse-echo ultrasound imaging is a medical imaging modality that constructs images based on the back-scatter of acoustic waves in tissue. Most ultrasound systems assume a spatially constant speed of sound when the time-of-flight of the acoustic wave is used to focus these back-scattered signals into medical images. However, the speed of sound in human tissue can vary spatially by tissue type and composition. The primary focus of this thesis is the estimation of a spatially-varying speed of sound in the tissue and using this speed of sound in order to optimally focus ultrasound signals into images, effectively correcting for phase aberrations resulting from an erroneous speed of sound during the focusing. We first develop a retrospective encoding and decoding scheme that enables us to reconstruct a multistatic synthetic aperture dataset from an arbitrary sequence of transmissions. The regularized inversion technique for the recovery of the multistatic dataset achieves a 99.36\% correlation between the multistatic dataset recovered from a walking-aperture focused-transmit sequence and the ground-truth. This technique is used to successfully demonstrate sound speed estimation and distributed aberration correction in abdominally-layered media. For sound speed estimation in layered media, the root mean-square error in simulations of two-layer media is 4.6 and 2.5 m/s at 4 and 8 MHz transmit frequency, respectively. These sound speed estimates are then used to optimally focus the multistatic synthetic aperture and achieve distributed aberration corrections. In phantom experiments, point target resolution improves from 0.58 to 0.26 and 0.27 mm, and lesion contrast improves from 17.7 to 23.5 and 25.9 dB, as a result of distributed aberration correction using the eikonal and wave-field correlation techniques, respectively. Then, we explore modeling and inversion techniques from ultrasound transmission tomography and seismic imaging, which we apply to pulse-echo ultrasound imaging. We demonstrate that shot-profile migration from seismic imaging can be used as a generalized synthetic aperture imaging technique for pulse-echo ultrasound imaging where it yields a 55\% improvement in point target resolution and 8.6 dB improvement in contrast over virtual source synthetic aperture. Shot-profile migration also lays the groundwork for an initial implementation of wave-equation migration velocity analysis (WEMVA) for pulse-echo ultrasound imaging. The complete investigation of WEMVA in pulse-echo ultrasound is left to future work.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2021; ©2021 |
| Publication date | 2021; 2021 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Ali, Rehman |
|---|---|
| Degree supervisor | Dahl, Jeremy J, 1976- |
| Thesis advisor | Dahl, Jeremy J, 1976- |
| Thesis advisor | Biondi, Biondo, 1959- |
| Thesis advisor | Kitanidis, P. K. (Peter K.) |
| Thesis advisor | Nishimura, Dwight George |
| Thesis advisor | Pauly, John (John M.) |
| Degree committee member | Biondi, Biondo, 1959- |
| Degree committee member | Kitanidis, P. K. (Peter K.) |
| Degree committee member | Nishimura, Dwight George |
| Degree committee member | Pauly, John (John M.) |
| Associated with | Stanford University, Department of Electrical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Rehman Ali. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2021. |
| Location | https://purl.stanford.edu/fc942dq0182 |
Access conditions
- Copyright
- © 2021 by Rehman Ali
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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