Noninvasive Imaging of Carotid Arterial Strain Using Displacement-Encoded MRI

Citation

Lin, Alexander Pei-Den Peter (2009) Noninvasive Imaging of Carotid Arterial Strain Using Displacement-Encoded MRI. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Q7NT-XN05. https://resolver.caltech.edu/CaltechETD:etd-06072009-232351

Abstract

Stroke is the leading cause of disability in the United States and the third leading cause of death. These “brain attacks” occur when atherosclerosis, the progressive process of thickening and hardening of arterial walls, develops in the carotid arteries, leading to stenosis or thrombosis that cuts off the vital supply of blood and oxygen to the brain. These atherosclerotic plaques have been shown to form in regions of excessive stretching or strain. Furthermore, intravenous ultrasound studies (IVUS) have demonstrated that strain plays a role in determining those plaques most likely to rupture, the so-called vulnerable plaques. However, IVUS is an invasive technique that poses risks for patients and requires specialized methods that are not readily available in most hospitals. Therefore, the objective of this thesis is to develop a noninvasive method of measuring strain in the carotid artery that may provide an early diagnosis of stroke.

Magnetic resonance imaging (MRI) is a powerful noninvasive method of imaging the human body. An MRI technique called displacement encoding with stimulated echoes, or DENSE-MRI, has been shown to accurately measure strain in the human heart. This thesis describes the adaptation of the DENSE-MRI technique to the carotid arteries, validation and optimization of the DENSE-MRI pulse sequence, and in vivo strain measurements in human subjects. The results show the successful adaptation of this method in the carotid arteries and that strain measurements are accurate, reproducible, and robust. In particular, utilization of a single-shot pulse sequence effectively removes flow-sensitive artifacts that permit strain mapping at the bifurcation and in the internal and external carotid arteries, areas where plaque is most likely to form. Furthermore, it is shown that strain changes with age and may be a more sensitive diagnostic measure as patients with atherosclerosis show significantly lower strain values.

The primary contributions of this thesis are the achievement of quantitative measurements of strain in the carotid arteries and the development of a robust method of measuring strain in atherosclerosis that may facilitate the early diagnosis of stroke so that treatment can be provided before the devastating effects of the disease can take their course.

Thesis Files