Triple-TWIST MRA: high spatial and temporal resolution MR angiography of the entire peripheral vascular system using a time-resolved 4D MRA technique

Multi-station contrast-enhanced magnetic resonance angiography (MRA) is considered as the imaging investigation of first choice in patients suffering from peripheral arterial occlusive disease. In order to overcome venous overlay and to gain dynamic flow information as provided by digital subtraction angiography (DSA), we developed a triple injection protocol for high-resolution MRA of the entire peripheral vascular system, applying time-resolved (TR) four-dimensional (4D) MRA sequences. Ten patients underwent three-station TR-MRA of the pelvis and lower extremities with DSA as reference standard. Both investigations were compared concerning stenosis on a segment-by-segment basis. Furthermore, 28 consecutive patients underwent the same MR-only imaging protocol. All images were evaluated concerning image quality (1 = non-diagnostic, 4 = excellent), venous overlay (from none up to substantial) and time to venous enhancement (very early/early/normal/late). Three-station TR-MRA proved feasible and was comparable with DSA in 282 vessel segments, with underestimation grade of stenosis in four segments and overestimation in four segments, respectively. In 32/38 patients no venous overlay was noted; in six patients there was mild venous overlay. Image quality was rated excellent or good in most cases. TR-MRA provides morphological and functional information without any timing issues due to optimal arterial enhancement at high spatial resolution without venous overlay.