High-field NMR imaging provides improved ability to detect small contrast changes associated with physiological function (e.g. perfusion). Techniques have been developed and implemented at 4.1T which have demonstrated improved contrast characteristics for ventricular function imaging using RF tagging. RF tagging deposits a grid of lines in the field of view at the start of the cardiac cycle which then distort as the myocardium moves across the cardiac cycle. This grid can be used in automated analysis of ventricular motion. This improvement resulted from the reduced magnetic relaxation rate at 4.1T vs clinical field strengths, the improved signal-to-noise ratio inherent at the higher field, and to radio frequency excitations developed at UAB which themselves improve tag line persistence. Animal studies have been carried out at heart rates from 75 to 130bpm demonstrating persistence of tag lines to end diastole. Myocardial perfusion has been imaged using an arterial spin-inversion technique which provides a quantitative model for perfusion estimation by comparing images in which arterial blood is magnetically inverted vs a control image. Signal differences of 1-3% have been visualized with high field imaging of animal models.
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