MR angiography (MRA) holds the potential to largely replace conventional angiography (XRA) for the evaluation of peripheral vascular disease (PVD). However, the pulse sequences and coils currently available need further improvement. This project addresses both of these issues, by accomplishing three goals: 1). The testing and use of an originally designed phased-array coil for use in the pelvis and lower extremities. 10 subjects will be utilized to compare image quality with the body coil and extremity coils. Contrast- to-Noise (CNR) calculations will be performed with the body coil, extremity, and phased array coil images, and the significance of differences in CNR assessed with the Wilcoxon signed-rank test. 2). Clinical evaluation of three original pulse sequences: gated three- dimensional (3D) segmented phase contrast (3D PCG) capable of axis specific variable velocity encoding, a 3D flow capture sequence using a 90x-180y-bipolar-90y preparation pulse, called """"""""FLOCAP"""""""", and an optimized gadolinium-enhanced 3D Time-of-Flight (TOF) sequence. FLOCAP uses a segmented k-space fast gradient echo readout. The FLOCAP sequence has significant potential advantage in imaging pulsatile vessels, improving venous suppression, and reducing velocity aliasing. Our preliminary data has shown good anatomic detail in tight stenoses with the short TE's of FLOCAP, with scan times of 3-4 minutes. 3D TOF gives high resolution images of all severities of disease, with no significant flow artifacts and scan times under one minute. 3D PCG gives 3D reprojections with reasonable scan times, and phase difference processing allows removal of veins and enhancement of arterial signal. All of these sequences image in-plane flow and, by various techniques, give excellent background suppression. 2D TOF will be compared to FLOCAP, 3D PcG, and 3D TOF in 24 patients, using ordinal regression to evaluate stenosis depiction, and analysis of covariance to evaluate the accuracy of stenosis length. Conventional angiography will be the gold standard. 3). Investigation of the hypothesis that the use of high dose (0.3 mm/kg cumulative) gadolinium will significantly improve the evaluation of PVD. The utility of high-dose gadolinium will also be assessed in the appropriate sequences in the above 24 patients, and results evaluated by the above methods. Only the best one of our original sequences is planned to be used along with 2D TOF in a larger study of 100 patients. Stenosis analysis will be as above and gadolinium will or will not be used as dictated by the 24 patient study. Thus, the possible advantages of 3D PC modified for peripheral vessels, the shorter TE's of FLOCAP, and the extremely fast scan times and lack of flow artifacts with 3D TOF will be explored. Furthermore, the value of gadolinium will be assessed, and a coil for imaging the peripheral vasculature will be evaluated.
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