Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.790968
Title: Precision microfabrication of optical probes for intravascular diagnostics
Author: Poduval, Radhika Kallidil
ISNI:       0000 0004 8500 3197
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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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.
Supervisor: Papakonstantinou, I. ; Desjardins, A. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.790968  DOI: Not available
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