Year: 2019
Type: dissertation
Abstract: There is a need for imaging modalities capable of more fully visualizing the features of atherosclerotic plaque and monitoring treatments. Currently, only invasive modalities are able to precisely assess fibrous cap thickness, plaque size, the extent of positive remodelling, and the correct expansion of stents. No individual modality can visualize all of these features at the present time, and considerable effort has been made to develop hybrid imaging catheters for broader capabilities. In line with that goal, this thesis describes the development of a dual frequency intravascular ultrasound (DF IVUS) catheter incorporating a bidirectional transducer stack with centre frequencies of 30 and 80 MHz. 30 MHz is within the range of currently available clinical IVUS, and 80 MHz was chosen to provide the desired superficial resolution. The prototype was designed to have a clinically-relevant size and form factor to ensure its applicability for this purpose. The design and fabrication process are explained in detail, and the characterization results show the successful performance of the prototype with respect to the design criteria. Imaging of phantoms, in vitro human atherosclerotic coronary arteries and in vivo healthy porcine coronary arteries demonstrate that the prototype is able to provide complementary, coplanar images; with superficial axial resolution as low as 16 μm, lower-resolution depth penetration up to 6 mm, penetration through blood at both 30 and 80 MHz, and improved visualization of a stent relative to the vessel wall. Features of plaque and the vessel wall were well-visualized compared with conventional IVUS (30 MHz). These results suggest that DF IVUS is technologically and clinical feasible as a technique for improved coronary imaging. Other design approaches to DF IVUS may provide additional benefits, including contrast-enhanced imaging, and the procedures described here may be relevant to the development of these and other sub-millimetre ultrasound devices.
Source: TSpace (University of Toronto)
Author: Chelsea E. Munding
Language: English
Subfield: Cardiology and Cardiovascular Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3104813886