Our goal is to develop novel imaging techniques to improve the repeatability and consistency of assessment of carotid artery atherosclerosis. During the past 3 years we have developed methods to improve the repeatability of quantitative measurements of carotid artery lesion morphology in carotid magnetic resonance imaging (MRI) and angiography (MRA) at 1.51. During the next four years we will perform three specific tasks to develop major improvements in carotid MRI/MRA. 1) We will implement efficient MRA and blood suppressed MRI sequences at 3.0T with special attention to reduced RF heating (SAR) to attain maximum efficiency and reduction or elimination of motion effects. Very few, if any, carotid imaging studies have been performed at 3.0T because of SAR limitations and motion effects. 2) We will develop a novel high resolution diffusion weighted imaging (DWI) technique applicable to the cervical carotid artery. Although in vitro studies demonstrate that diffusion weighted imaging helps discriminate between necrotic core, fibrous tissue, and hemorrhage, a pulse sequence adequatefor high resolution DWI of the cervical carotid in vivo does not yet exist. 3) We will develop improved multi-coil imaging techniques, including a novel technique to obtain the complete complex coil sensitivities and the noise covariance matrix without a reference scan, and thereby allow the first image-based direct implementation of the optimal multi- coil reconstruction algorithm. This proposal includes development of efficient carotid MRI/MRA techniques at 3.0T, carotid DWI, optimized RF coils, a fully optimal phased array reconstruction technique, and improved post processing techniques. Thus this proposal represents a comprehensive approach to developing a complete set of tools to diagnose, evaluate, and monitor the evolution of this important disease. With improved signal to noise ratio and the capability of diffusion weighted imaging, we will assess the improvements gained at 3.0T over 1.5T. About 90% of our work will be to develop and test carotid imaging technology at 3.0T. The remaining 10% effort, at 1.5T, will provide a valid baseline for comparison with 3.0T. We believe that each aspect of this work will help open the door for improved longitudinal studies of the carotid artery at 3.0T.
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