Bodian, Semyon; (2023) Fabrication of Composite Materials for Medical Imaging and Device Characterisation. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis describes the investigation of composite materials to design and fabricate imaging devices and their subsequent characterisation, in the context of image guidance for minimally invasive surgical interventions. Medical ultrasound is a widely used imaging modality that utilises high frequency sound waves to map a tissue’s shape and size. Optical ultrasound (OpUS) generation enables miniaturised ultrasound transmitters to be formed using facile syntheses, demonstrating high-resolution ultrasound imaging. First, fibre-optic OpUS transmitters capable of dual-modality ultrasound/photoacoustic imaging as integrated imaging probes are presented. The OpUS transmitters were formed from bilayer wavelength-selective quantum dot composites. Combined with a Fabry-Pérot hydrophone, these composites illustrated high-resolution overlaid ultrasound/photoacoustic images of a gel wax phantom. Two composite materials were then designed and synthesised to produce aorta and femoral artery phantoms, suitable for characterisation using particle image velocimetry and ultrasound imaging, respectively, with composites' Young Modulus and refractive indices characterised. Quantum dot composites were also deployed onto planar macroscale substrates using doctor-blading and spin-coating deposition techniques. These composites yielded clinically useful ultrasound pressures and bandwidths equivalent to those used in diagnostic ultrasound imaging. Fibre-optic OpUS transmitters comprising broadband optically absorbing candle-soot composites were fabricated. These composites performed high-resolution ultrasound imaging of lamb brain tissue. A fibre-optic OpUS transmitter was integrated into a candle-soot-coated needle. Visual enhancements of the needle shaft and tip were observed during in and out-of-plane needle insertions into ex vivo animal tissue. The work presented here, through interdisciplinary research, illustrates facile fabrication strategies for composite materials deposited onto miniaturised fibre-optic and macroscale substrates, that could easily be translated into clinical settings in the near future. These devices facilitate both high-resolution single and multi-modality imaging, and augmented imaging resolutions of surgical instruments. Further, synthesising patient-specific phantoms with material properties functionalised for specific imaging modalities illustrates the potential comprehensive characterisation of these imaging devices.

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