Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Physics

Language

English (en)

Date of Award

5-24-2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

James Miller

Abstract

The development, execution, and interpretation of studies investigating the physics of the interaction of ultrasound with normal and pathological coronary artery tissues are described in this dissertation. Ultrasound is a modality capable of visualizing and characterizing the lesions that define atherosclerosis. A better understanding of the physics underlying the mechanisms by which ultrasound interacts with arterial tissue and plaques may provide benefit to patients with coronary artery disease. The two-fold goal of the studies presented in this thesis was to better understand the fundamental physics of the relationship between ultrasound and coronary artery tissue and to use this knowledge to contribute to the advancement of techniques capable of improving the diagnosis and management of atherosclerosis. The work presented in this dissertation appears to represent the most comprehensive study of the fundamental ultrasonic properties of human coronary arteries to date. An acoustic microscopy system was developed, refined, and tested for the purposes of acquiring data from fresh: that is, not chemically fixed) coronary artery tissues and atherosclerotic plaques. Novel methods of preparing samples, imaging samples, and collecting data from samples were validated in studies of lamb tissue. A very large data set spanning the ultrasonic bandwidth of current and near-future intravascular ultrasound: 22 to 105 MHz) was acquired from human coronary artery tissues insonified in two orthogonal orientations. These data were analyzed to yield measurements of the apparent integrated backscatter from coronary arteries and atherosclerotic plaques. Studies of the radial apparent backscatter carried out in the acoustic microscope confirmed trends observed in clinical radial intravascular ultrasound; in contrast, acoustic microscopy studies of the axial apparent backscatter identified a substantially different trend. Specifically, these studies revealed that the anisotropy of apparent integrated backscatter of the media and adventitia is modest, but that the anisotropy of the apparent integrated backscatter from atherosclerotic plaque is quite substantial. The attenuation coefficient of coronary artery tissues and atherosclerotic plaques was measured across the wide bandwidth 22 to 105 MHz. It was shown that, in the axial orientation, the attenuation coefficient is lower in the media layer than in the intima/plaque or adventitia layers. The measured axial backscatter coefficient of coronary artery media was similar to that of coronary artery intima/plaque, and smaller than that of coronary artery adventitia. The results derived from these studies may serve to advance the understanding of the physics underlying ultrasound's interaction with coronary artery tissues. The data may provide insights for improved clinical devices and methods, as well as serve as the basis for future measurements of the physical properties of coronary artery tissues and atherosclerosis.

Comments

Permanent URL: http://dx.doi.org/10.7936/K7MG7MKC

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