The broad, long-term objective of this proposal is to improve the prognosis of patients with arterial disease, one of the leading causes of death in the United States. Contrast-enhanced imaging is the clinically accepted conventional method for MRA. However, patients with renal insufficiency who receive gadolinium- based agents are at risk for developing a debilitating and a potentially fatal disease known as nephrogenic systemic fibrosis. The purpose of the proposed project is to develop a new non-contrast-enhanced MRA technique. Two sets of ECG-triggered, cardiac phase-resolved 3D images will be acquired with and without flow sensitized dephasing (FSD) preparation, respectively. In systole, steady state free precession (SSFP) imaging generates bright blood signals for both arteries and veins, independent of flow, while images acquired with FSD preparation show black blood arteries and bright blood veins because FSD preparation causes dramatic signal loss to fast flowing arterial blood but has little effect on slow flowing venous blood and background tissue. Subtraction of the two image sets will show arteries only. The """"""""black-blood"""""""" images can also be used for arterial wall evaluation to quantify plaque burden. Therefore, this technique has the potential for simultaneous MRA and arterial wall imaging of the entire body.
Specific aims of the project are: (1) To develop the cardiac phase-resolved, FSD-prepared, self-gated 3D SSFP technique for simultaneous MRA and arterial wall imaging. Four tasks will be performed: (a) A self-gating method will be developed to eliminate potential image artifacts due to motion (e.g., swallowing during carotid MRA and respiratory motion for renal MRA). (b) SSFP will be improved for consistent bright blood MRA in the presence of flow. (c) FSD preparation and data acquisition schemes will be optimized to maximize contrast to noise ratio between arterial blood and background/vein for MRA and vessel wall imaging in carotid, renal, and peripheral arteries. (d) k-t parallel imaging will be optimized to improve the speed of cardiac phase-resolved MRA and vessel wall imaging. (2) To verify that the non-contrast MRA and vessel wall imaging technique can accurately depict artery stenoses and quantify plaque burden in patients. Three groups of patients with carotid, renal, and peripheral artery disease, respectively, will be studied. Contrast-enhanced MRA and single-slice turbo spin echo techniques will be used as the reference methods for MRA and wall imaging, respectively. The end point of the project is the development and initial clinical validation of a new non-contrast- enhanced MRA approach capable of simultaneous MRA and arterial wall imaging of the entire body.
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