PhD defence by Lars Haslund

On Tuesday 10 September 2024, Lars Emil Haslund will defend his PhD thesis "Pressure Gradient Estimations".

Time: 13:00
Place: Building 101, meeting room S07

Principal supervisor: Professor Jørgen Arendt Jensen
Co-supervisor: Title Marie Sand Traberg
Co-supervisor: Matthias Bo Stuart

Examiners:
Associate Professor Billy Yiu, DTU Health Tech
Professor Lasse Løvstakken, NTNU
Research director Damien Garcia,CREATIS

Chairperson at defence:
Professor Erik V. Thomsen, DTU Health Tech 

Abstract:

High blood pressure, smoking, diabetes, and high cholesterol levels are common risk factors for developing atherosclerosis and, thus, the build-up of fatty materials inside the blood vessels. Atherosclerosis development can lead to a stroke, which is one of the most common causes of death. Different techniques exist to assess the severity of atherosclerotic development and depend on the region of interest. Pressure gradients are often measured in the coronary arteries using pressure-sensitive catheters, whereas, in the carotid arteries, the North American Symptomatic Carotid Endarterectomy Trial and The European Carotid Surgery Trial have been used to measure stenosis percentage. These methods are invasive, expensive, and not without risk.

In this project, it is hypothesized that non-invasive, precise, and accurate pressure differences can be estimated in the carotid arteries using synthetic aperture ultrasound with a precision better than invasive catheters. Here, pressure differences can be used for analyzing the blood flow along a streamline, where high gradients indicate stenotic development. The estimator uses the unsteady Bernoulli equation and relies on precise calculations of blood velocities and accelerations, which are attained using synthetic aperture ultrasound, a new interleaved ultrasound sequence, and directional cross-correlation. The estimator allows for angle-independent estimations of high blood flow velocities and is evaluated on simulations and phantom measurements, compared to pressure catheters, and applied to ten healthy volunteers.

The result shows that non-invasive precise pressure differences can be estimated in a realistic clinical setup using ultrasound. Contrary to invasive catheters, the ultrasound method is risk-free, allows for repeated measurements, and can achieve pressure differences without introducing changes to the flow, which is the case for invasive catheters.