MRI OF CORONARY ARTERY FLOW IN ISOLATED & IN VIVO HEARTS

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DESCRIPTION: (Adapted from the application) The main goal of this research is to develop techniques for MR coronary angiography by using phantoms, isolated heart preparations, and in-vivo animal models.The ability to image coronary arteries without iodinated contrast agents, indwelling catheters, and x-rays would represent a major improvement in patient comfort and safety. Several factors contribute to the unique difficulties encountered in MR coronary angiography. These include the substantial displacement of the vessels due to both cardiac and respiratory motion, the large body of flow in the ventricular cavities which are in close proximity, and the tortuous paths of vessels around the heart. The applicant proposes sequential evaluation of these problems. Flow compensated gradient echo sequences will first be applied to isolated isovolumic rat heart preparations in which respiratory motion, much of the bulk cardiac motion, and signal from the intraventricular flow are eliminated. Multislice acquisitions will be constructed as a 3D set. The sequences will be applied to an isolated working heart preparation, thus reintroducing the complicating intraventricular flow and cardiac motion. The intraventricular flow signal will be eliminated by post-processing before the 3D reconstruction. Fast imaging techniques, based on ultra-fast gradient echo imaging, will be developed to obtain an image within a single or several heartbeats. Contrast in the fast imaging sequences will be obtained with prepulses and variable excitation flip angles. Flow tagging techniques will also be investigated. Finally, the developed techniques will be applied to in-vivo control rats and rabbits. Watanabe heritable hyperlipidemic (WHHL) rabbits, which develop coronary atherosclerosis, will also be imaged. The MRI coronary angiograms will be compared with the results obtained from contrast angiograms performed with conventional cine angiography modified for use in rabbits. Post-mortem angiographic examination will confirm each of the individual animal experiments.