3-DIMENSIONAL STEADY-STATE MR-ANGIOGRAPHY OF THE LOWER-EXTREMITIES

Volume steady-state black-blood magnetic resonance imaging was evaluat ed as a method for depicting lower extremity vasculature. In steady-st ate imaging, flow has low signal intensity because motion destroys the coherence of transverse magnetization. To optimize image contrast, co mputations and measurements were obtained for the three-dimensional (3 D) GRASS (gradient-recalled acquisition in the steady state) and 3D SS FP (steady-state free precession) sequences and a range of TRs and fli p angles to determine optimal vessel-muscle contrast. The best results were achieved with a 3D GRASS sequence with a TR msec/TE msec of 25/5 and a flip angle of 30-degrees. Coronal images of the femoral and pop liteal vessels were obtained in healthy volunteers with various fields of view and voxel sizes. Inflow of unsaturated spins from outside the image region, yielding high signal intensity, could be a potential dr awback in steady-state black-blood imaging; however, problems can be a voided by using coronal acquisitions and large fields of view. Steady- state black-blood imaging depicts vessels with high accuracy and is fa ster and free of flow artifacts.