Pham, Khoa;
(2022)
Dual-mode photoacoustic and ultrasound imaging system based on a Fabry-Pérot scanner.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The planar Fabry-Pérot (FP) scanner is an ultrasound detector that simultaneously provides high sensitivity, a high density of small (sub-100 μm) acoustic elements, and a broad bandwidth (> 30 MHz). These features enable the FP scanner to acquire high-resolution 3D in vivo photoacoustic images of biological tissues up to depths of approximately 10 mm. The aim was to add complementary morphological ultrasound contrast to photoacoustic images to extend their clinical applicability. This was achieved by developing a dual-mode photoacoustic and ultrasound imaging system based on the FP scanner, which was modified to transmit optically generated ultrasound. The FP sensor head was coated with an optically absorbing polydimethylsiloxane(PDMS) composite layer, which was excited with nanosecond laser pulses to generate broadband planar ultrasound waves for pulse-echo imaging. First, an all-optical ultrasound system was developed using a highly absorbing carbon nanotube-PDMS composite coating. The system was characterised with a series of experiments, and its imaging performance was tested on tissue mimicking phantoms and ex vivo tissue samples. Second, the effect of the frequency content of the detected signals and the effect of spatial aliasing on the image quality were investigated in simulation. A broadband system was found to reduce the effect of spatial undersampling of high frequencies which results in a reduction of contrast due to the formation of grating lobe artefacts. Third, to improve the image quality, frequency and angle compounding were explored in simulations and experimentally. Coherent and incoherent compounding were considered, as well as the effect of the filter bandwidth on frequency compounded images, and the influence of the number and spread of angles used in angle compounded images. Finally, a dual- mode photoacoustic and ultrasound imaging system was demonstrated with a gold nanoparticle-PDMS composite which enabled wavelength-selective absorption of light. The system was shown to obtain high-resolution 3D dual-mode images providing complementary contrast from optically absorbing and acoustically scattering structures.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Dual-mode photoacoustic and ultrasound imaging system based on a Fabry-Pérot scanner |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2021. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10159167 |
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