AbstractThe presence of obstructions to blood ﬂow in the human cardiovascular system can lead to an inability to eﬃciently and eﬀectively perfuse downstream tissues and increase the work demand of the heart. In this scenario, the pressure drop through a vascular obstruction is a biomarker adopted in clinical guidelines for the management of several disease conditions, such as aortic coarctation and valvular stenosis. While extensively used clinically, current methods and tools to assess the pressure drop suﬀer from either the associated risks of invasive catheterization procedures, or potential inaccuracies from non-invasive pressure estimations due to simpliﬁed formulations or inter-observer variability.
The primary aim of this thesis is to further develop non-invasive methods to estimate pressure drops, increasing current robustness and accuracy. Using the comprehensive spatio-temporal hemodynamic information provided by Four Dimensional Phase-Contrast Magnetic Resonance Imaging, an existing ﬁnite element formulation to compute pressure diﬀerences is evaluated, illustrating its sensitivity to data when estimating viscous ﬂows and exploring potential approaches to address this. A novel formulation using the work-energy principle is then introduced and validated on in silico test cases, demonstrating an increased accuracy and robustness to noise and to the image segmentation process. Finally, the proposed method is applied for the assessment of the aortic valve function of a cohort of patients with various degree of stenosis, revealing a fundamental bias in the Bernoulli formulation taken in Doppler-based estimation.
|Date of Award||1 Jul 2016|
|Supervisor||Nicolas Smith (Supervisor), David Nordsletten (Supervisor) & Pablo Lamata de la Orden (Supervisor)|