Rapid generation of preview images for real-time 3D MR angiography

In 3D real-time MR angiography the reconstruction of images from large raw datasets via Fourier transforms with minimal delays is problematic. In this study strategies for reconstructing time-resolved three-dimensional (3D) datasets at a rate substantially faster than conventional 3D MR image reconstruction were investigated on general-purpose computer hardware. Moderate quality 'preview images' were generated from k-space subsets to reduce image reconstruction times from more than 50 s to 0.3 s per image volume. A blinded review of 3D TRICKS patient examinations showed that these moderate-quality images were sufficient for providing immediate feedback and guiding the subsequent reconstruction of selected time frames (p < 0.05). Fourier projection (reconstruction from a central k-space slice) was the most efficient reconstruction technique. However, the reduction of the reconstructed volume in all three dimensions resulted in higher contrast and better image quality while allowing reconstruction in near-to-real-time (less than 1 s per image volume). The use of such preview images in a real-time system allows for fast feedback from dynamic 3D datasets, enables scanner interaction with minimal latencies and can substantially reduce the postprocessing times.