Ungated radial quiescent-inflow single-shot (UnQISS) magnetic resonance angiography using optimized azimuthal equidistant projections

Abstract

Purpose: We hypothesized that non-contrast-enhanced MR angiography (NEMRA) could be performed without cardiac gating by using a variant of the quiescent-inflow single-shot (QISS) technique. Methods: Ungated QISS (UnQISS) MRA was evaluated in eight patients with peripheral arterial disease at 1.5T. The radial acquisition used optimized azimuthal equidistant projections, a long quiescent inflow time (1200 ms) to ensure replenishment of saturated in-plane spins irrespective of the cardiac phase, and a lengthy readout (1200 ms) so that a complete cardiac cycle was sampled for each slice. Venous and background tissue suppression was obtained using frequencyoffset-corrected inversion radiofrequency pulses. Results: Scan time for UnQISS was 15.4 min for an eightstation whole-leg acquisition. The appearance of UnQISS MRA acquired using the body coil was comparable to electrocardiographic-gated QISS MRA using phased array coils. A small radial view angle increment minimized eddy current-related artifacts, whereas image quality was inferior with a golden view angle radial increment or Cartesian trajectory. In patient studies, ≥50% stenoses were consistently detected. Conclusion: Using UnQISS, peripheral NEMRA can be performed without the need for cardiac gating. The use of fixed imaging parameters and body coil for signal reception further simplifies the scan procedure.