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Precision Microfabrication of Optical Probes for Intravascular Diagnostics

Poduval, Radhika Kallidil; (2019) Precision Microfabrication of Optical Probes for Intravascular Diagnostics. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis details a collection of design, optimisation, fabrication and characterisation work to form fiber-optic probes and optical phantom devices for intravascular diagnostics in minimally invasive surgery (MIS). Optically generated ultrasound is an emerging technique to create broadband high frequency ultrasound via the photoacoustic effect. In the first segment of this thesis, the development of a novel miniature fiber-optic ultrasound transmitter is detailed. A morphologically controlled coating was formed at the endface of a multimode optical fiber by controlled electrospinning of a carbon-nanotube composite. Efficient optical ultrasound generation was realised, with signal amplitude, bandwidth and device form factor suited to clinical intravascular imaging applications. Thereafter, precision microfabricated extrinsic fiber-optic interferometric sensors for MIS intravascular pressure and temperature evaluation were developed. In a first demonstration, two-photon polymerisation (TPP) was used to form a high resolution freeform microscale extrinsic sensing element in a fiber-optic interferometric sensor, comprising of optical lensing elements, a confined gas cavity and a distal deformable membrane. These devices were interrogated using low-coherence interferometry and their performance evaluated in simulated intravascular conditions. Pressure and temperature sensitivities in the biomedical range of interest were observed with these devices. Characterisation and clinical validation of precision microfabricatied probes possessing unconventional sensing geometries used in MIS require complex imaging phantoms. In the final project, high resolution mesoscale intravascular optical coherence tomography (IVOCT) phantoms were created using TPP and micro-injection of tissue-mimicking materials to simulate healthy and diseased tissue morphology. Sub-resolution IV-OCT phantoms with anatomic features were realised and verified using a clinical IV-OCT system. The devices and techniques developed in this thesis pave the way for precision microfabrication of fiber-optic probes in intravascular ultrasound imaging, multi-parameter physiological sensing, and the associated 3D mesoscale imaging phantoms. These devices and fabrication paradigms lend themselves well to prototyping and design optimisation of miniature medical devices, with potential for clinical translation in the near future.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Precision Microfabrication of Optical Probes for Intravascular Diagnostics
Event: University College London, Dept. of Electronic and Electrical Engineering
Language: English
Additional information: Copyright © The Author 2019. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/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 > Provost and Vice Provost Offices
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 Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10080640
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