Evaluation of Tomographic 3D Ultrasound in Vascular Disease

UoM administered thesis: Phd

Abstract

Objectives: The emerging use of Tomographic 3D Ultrasound (tUS) for vascular disease imaging is novel. This thesis aimed to establish whether tUS is the most accurate investigation for each indication, while demonstrating the potential value of tUS in vascular surgery. Methods: The validity of tUS for measurement accuracy was first established using a phantom model. Subsequently six studies were designed on different vascular disease modalities to determine diagnostic accuracy, utility, reproducibility and intra-/inter-observer agreement of tUS. The clinical areas investigated were, Abdominal Aortic Aneurysm, Endo-Vascular Aneurysm Repair (EVAR) completion imaging to detect renal patency and endoleak, Carotid Plaque Volume as a measure of vulnerability, Peripheral Artery Disease (PAD) angiography, potential autologous bypass mapping and Arterio-Venous Fistula surveillance. To establish measurement precision tUS was compared to current gold standard index tests. Results: Two broad tUS utilities emerged. tUS can be used with and without microbubble contrast and the implications of each are crucially important to implementation into daily use. tUS can readily be utilised to accurately measure artery geometry; namely, length, diameter and volume. When compared to CTa, there is greater variability in diameter measurements for patients who have had EVAR than AAA's pre-treatment. Anterior-Posterior diameters remain the most accurate method of measurement. Contrast-enhanced tUS (CEtUS) and CEUS were non-inferior to rotational angiography at detecting endoleak, particularly type II. The patient safety benefits and capacity of CEtUS may mean it is superior to rotational angiography in certain circumstances but 33% of renal vessels were not identified. This thesis reports the first investigation on the accuracy of CEtUS at the detection of clinically significant stenoses and occlusions of run-off vessels which proved highly reproducible with a significant degree of precision, but discrepancies between both CEtUS and angiography were found. tUS is also highly reproducible for measuring CPV with minimal bias and a high degree of precision with narrow confidence intervals. The relatively less skill and shorter time required to assess artery geometry, potential conduits or AVF by tUS, in comparison to the standard DUS, has added benefits for both the patient and the workforce representing a potential increased scanning capacity and decreased RSI risk. Due to capacity and availability, tUS could be the imaging modality of choice with the benefit of drastically reduce radiation and nephrotoxic contrast exposure possibly. Conclusion: We have shown that tUS is an accurate, reproducible and precise imaging modality for various disease modalities. This thesis has added evidence to the published literature while addressing it's aims, laying the foundations for future work with tUS for vascular disease. Based on the evidence available tUS can readily be utilised for arterial geometry assessment and vessel mapping/surveillance. Contrast-Enhanced tUS should be used as part of a careful imaging strategy on EVAR completion as well as for targeted angiographic imaging for PAD or careful CPV measurement.

Details

Original languageEnglish
Awarding Institution
Supervisors/Advisors
Award date31 Dec 2019