Coronary artery imaging in a 0.5-Tesla scanner: Implementation of real-time, navigator echo-controlled segmented k-space FLASH and interleaved-spiralsequences

Coronary angiography techniques have been implemented on a 0.5-Tesla scanne r with a view to performing coronary artery imaging, Slice-followed, segmen ted k-space FLASH sequences and interleaved-spiral sequences have been empl oyed with acquisitions under real-time navigator echo control with patient feed back, enabling poor signal-to-noise levels to be overcome by averaging data acquired over multiple, variable-length, reproducible breath holds. G ood-quality, millimetre-resolution coronary images were obtained in ten nor mal subjects with both techniques. The mean percent of data segments or int erleaves acquired with the navigator echo within the 5-mm diaphragm accepta nce window was 57% [standard deviation (S.D.), 11%; range, 38-85%], and the average image-acquisition times were 123 +/- 22 sec and 71 +/- 14 sec for segmented FLASH and interleaved-spiral imaging, respectively. In addition t o shorter acquisition times, the interleaved-spiral sequence has superior t emporal resolution, allowing the acquisition of limited, multislice data se ts. However, the sequence is particularly sensitive to the off-resonance ef fects of residual epicardial fat surrounding the artery and to field nonuni formities, both of which lead to image blurring and, unlike segmented FLASH acquisitions (which are very robust), the spiral data sets generally requi re postprocessing. (C) 1999 Wiley-Liss, Inc.