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Advancing Cardiovascular Shear Wave Elastography and Image Registration

Method Development and Safety Evaluation

Time: Mon 2024-05-20 10.00

Location: T1 (Emmy Rappesalen), Hälsovägen 11C, Huddinge

Language: English

Subject area: Medical Technology

Doctoral student: Tim Nordenfur , Medicinsk avbildning

Opponent: Associate professor Gabriel Kiss, NTNU

Supervisor: Professor Matilda Larsson, Medicinsk avbildning

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QC 2024-04-29


Cardiovascular disease remains the leading cause of death and disability worldwide, with its burden on health and healthcare systems projected to rise. In cardiovascular diagnostics and treatment strategy decisions, medical imaging plays a significant role. This thesis aims to improve diagnostic tools for stable coronary artery disease, assess the safety of techniques for guiding treatment decisions in carotid artery stenosis, and develop a novel technique for the elastic characterisation of anisotropic tissues.

Accurate diagnosis of stable coronary artery disease demands both anatomical information, on the location and severity of coronary plaques, and functional information, on their haemodynamic impact. A composite image of these types of information could offer greater diagnostic value than examining them separately.In this context, Study I explored image registration of 3D echocardiography with coronary computed tomography angiography. Three image registration algorithms were implemented and validated using patient data. Findings suggest that integrating images from these imaging modalities is feasible, and that iterative closest-point methods can be improved by incorporating orienting landmarks to avoid ventricular rotation.

In assessing carotid artery stenosis, plaque composition is increasingly recognised as an important factor for guiding treatment. Ultrasound-based shear wave elastography is emerging as a promising non-invasive method for plaque characterisation, although its mechanical impact on plaques and arterial walls is not completely understood. Studies II and III evaluated the safety of arterial shear wave elastography ex vivo in porcine models and in vivo in human carotid arteries. Results indicate that this technique exposes the arterial wall to significantly less strain than arterial pulsation, at strain rates comparable to those experienced during strenuous exercise.

In addition to arterial applications, shear wave elastography is increasingly used to measure elasticity of anisotropic tissues, such as the myocardium. However, current techniques can only fully characterise the elastic properties of isotropic tissues. In Study IV, a novel dual-probe shear wave elastography system was developed for elastic characterisation of transversely isotropic tissues, which exhibit multiple wave modes. Ex-vivo experiments successfully tracked all wave modes and demonstrated the system's feasibility to measure all elastic parameters.