Evaluation of shear wave elastography for the characterisation and diagnosis of vascular disease

Abstract

Shear wave elastography (SWE) is an emerging ultrasound technology used for non-invasively quantifying the mechanical properties of soft tissues. This thesis focuses on applications of shear wave elastography in vascular disease. Our systematic review showed that there is limited vascular shear wave studies and also the need for studies that investigate scanner performance to assess the accuracy of SWE measurements. Therefore, two in vitro studies were designed using test phantoms to investigate factors that might cause SWE measurement variability and to assess and quantify scanner performance over different settings with depth. These studies showed that SWE measurements in different settings was possible. Results from the Leicester elastography phantom (LEPP) demonstrated its ability to quantify the SWE measurement over depth providing a potential performance metric index called a Summative Performance Index (SPI). A healthy volunteer study involving 73 healthy participants was conducted to provide normative reference for carotid artery wall elasticity and investigate factors that may lead to SWE measurements variability. Although SWE measurements were found to be highly variable across the general population, none of the demographic or physiological factors (Age, sex, BMI, pp, map) we investigated explained the high variability in YM values observed between participants. Finally, our observational clinical study involving 89 spontaneous coronary artery dissection (SCAD) patients and 38 controls were assessed the potential of SWE imaging of the common carotid arteries (CCA) in patients with spontaneous coronary artery dissection (SCAD). It revealed that Young’s modulus (YM) estimates ranged from 17 to 133 kPa in SCAD patients compared to 34 to 87 kPa in non-dissection controls, but due to large variance there was no significant difference between groups. In conclusion, although results from this thesis indicate that vascular SWE is possible, however, variability were found associated with YM measurement which need to be addressed before clinical implementation.