ances in the field of intravascular imaging have provided clinicians with power ful tools to aid in the assessment and treatment of vascular pathology. Optical Ultra sound (OpUS) is an emerging modality with the potential to offer significant bene fits over existing commercial technologies such as intravascular ultrasound (IVUS)
or optical coherence tomography (OCT). With this paradigm ultrasound (US) is
generated using pulsed or modulated light and received by a miniaturised fibre-optic
hydrophone (FOH). The US generation is facilitated through the use of engineered
optically-absorbing nanocomposite materials. To date pre-clinical benchtop stud ies of OpUS have shown significant promise however further study is needed to
facilitate clinical translation.
The overall aim of this PhD was to develop a pathway to clinical translation
of OpUS, enabled by the development of a catheter-based device capable of high
resolution vascular tissue imaging during an in-vivo setting.
A forward-viewing OpUS imaging probe was developed using a 400 µm mul timode optical fibre, dip-coated in a multi-walled carbon nanotube-PDMS com posite, paired with a FOH comprising a 125 µm single mode fibre tipped with a
Fabry-Perot cavity. With this high US pressures were generated (21.5 MPa at the
transducer surface) and broad corresponding bandwidths were achieved (−6 dB of
39.8MHz). Using this probe, OpUS imaging was performed of an ex-vivo human
coronary artery. The results demonstrated excellent correspondence, in the detec tion of calcification and lipid infiltration, with IVUS, OCT and histological analysis.
A side-viewing OpUS imaging probe, employing a reflective 45 °angle at the dis tal fibre surface, was used to demonstrate rotational B-mode imaging of a vascular structure for the first time. This provided high-resolution imaging (54 µm axial
resolution) with deep depth penetration (>10.5 mm). Finally the clinical utility of
this technology was demonstrated during an in-vivo endovascular procedure. An
OpUS imaging probe, incorporated into an interventional device, allowed guidance
of in-situ fenestration of an endograft during a complex abdominal aortic aneurysm
repair.
Through this work the potential clinical utility of OpUS, to assess pathology
and guide vascular intervention, has been demonstrated. These results pave the way
for translation of this technology and a first in man study.