Magnetic resonance imaging of cardiacvascular function

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Our lab has applied a high-power MRI technique called DENSE to image heart wall and carotid artery wall motion in detail. DENSE stands for Displacement ENcoding with Stimulated Echo and is pioneered in our lab. We successfully developed this year the scan protocol and data processing software for heart and blood vessel wall strain and motion mapping, and tested them in normal volunteers and patients. One application of this development is to measure the compliance or stiffness of the heart wall in early and mid diastole, which is a key factor in how the heart chambers rapidly fills to volume in diastole. We also used this technique to accurately measure the fluctuation of tissue volume in the heart wall due from the interaction between the oscillating intramyocardial blood pressure and coronary blood flow. These findings are published in the journal Magnetic Resonance in Medicine and presented in conferences. Our lab also observed a new phenomenon in spin-echo MRI of the heart when a blood-pool contrast agent is infused into the animal - a dependence of the image intensity on the direction of the scanner's magnetic field. We found the mechanism behind the phenomenon and with preliminary data in a rat model showed that it is a very effective way to map the capillary structure, and by inference muscle fiber structure, in a beating heart. This is probably the most effective way of imaging microvascular structure in vivo. This finding is also published in the journal Magnetic Resonance in Medicine.