| Peripheral artery disease (PAD) affects approximately 8 million Americans and is associated with significant morbidity and mortality. The current "gold standard" for diagnosing PAD, x-ray angiography, is an invasive, costly procedure and uses ionizing radiation and nephrotoxic contrast media. While contrast-enhanced MR angiography (CE-MRA) is being accepted as a routine non-invasive diagnostic tool, safety concerns of gadolinium contrast agent in patients with severe renal insufficiency have recently triggered regrowing interests in noncontrast MRA (NC-MRA). Furthermore, MR imaging (MRI) techniques can non-invasively interrogate artery wall to identify patients at high risk for acute cardiovascular events and assess the total atherosclerotic plaque burden and lesion composition. Hence, MRI is potentially a viable modality to provide a comprehensive evaluation of PAD.;The first aim of this work was to develop a three-dimensional (3D) NC-MRA technique. First, a segmented balanced steady-state free precession (SSFP) sequence combined with ECG-triggering, flow-sensitive dephasing (FSD) magnetization preparation, and subtraction techniques was implemented and tested on the calf station. Second, the FSD-prepared NC-MRA technique was translated to the hand arterial system by comparing with CE-MRA in terms of image quality and evaluation of degree of stenosis in control and patient groups. Third, a two-dimensional (2D) method was developed to rapidly identify an optimal FSD parameter, prior to 3D NC-MRA, to achieve better suppression of blood flow signal when an FSD preparation is applied. Fourth, a multi-directional FSD preparative scheme was developed to ensure reliable signal suppression of flows in multiple directions.;The second aim of this work was to explore the applications of a recently proposed 3D vessel wall MRI technique, SPACE, and make some technical improvements. First, the feasibility of using the SPACE sequence for high-spatial-resolution vessel wall imaging of the superficial femoral artery was investigated on control volunteers and patients. Second, carotid vessel wall imaging at 3.0T was improved in the suppression of residual blood signal at carotid bifurcation by implementing an FSD-prepared SPACE sequence. Last, to address image artifacts secondary to swallowing motion during carotid SPACE imaging, a self-gating (SG) technique was developed. All above technical developments will benefit the long-term goal -- development of a strategy for the comprehensive evaluation of PAD with NC-MRA and BB vessel wall MRI and improve the prognosis of patients. |
