This application is a competing renewal for a project titled """"""""High-resolution time- resolved contrast-enhanced MR angiography"""""""". The original project introduced the concept that projection acquisitions in MR could be undersampled in high contrast environments. Significant progress produced imaging techniques that deliver four times faster resolution per unit time than Fourier encoding. Several fast scan methods were developed for abdominal, pulmonary, cardiac, peripheral, phase-contrast and T2- weighed imaging. The focus of this competing renewal is on undersampling techniques that take the next step in high resolution 3D MR angiography by dramatically increasing its capabilities for time-resolved imaging. The original project used undersampled projections for the in- plane dimensions and Fourier encoding in the slice dimension. This project acquires 3D projections in all orientations, making the undersampled energy more diffuse and less noticeable. While the speedup factor is comparable with the original project for static imaging, temporal processing of the dataset allows speedup factors that vary with spatial frequency from 40 at the lowest spatial frequencies to 4 at the highest ones. Other features, including isotropic resolution, broad coverage, and insensitivity to contrast arrival time, make this an ideal technique for abdominal contrast-enhanced MR angiography.
The aims of the project include 1) shortening the acquisition time by increasing the efficiency of the sampling technique, 2) further developing and evaluating the temporal filtering algorithms for time-resolved imaging, 3) validating the technique against x-ray computed rotational angiography in a swine model of renal artery stenosis, and 4) validating the accuracy of the technique in patients with suspected abdominal vasculature disease. Successful completion of this work will produce an MR exam capable of evaluating the entire abdominal vasculature in a total exam time of less than five minutes.
