MR angiography with a cardiac‐phase–specific acquisition window

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Abstract
A method for cardiac‐phase–specific magnetic resonance (MR) angiography is presented. An electronics module permits incrementing of phase‐encoding gradients and storage of incoming data only during a chosen portion of the cardiac cycle. Suppression of stationary material is maintained by delivering radio‐frequency pulses at constant TR throughout the cycle. Imaging of a pulsatile flow phantom demonstrates that acquiring data only during systole substantially increases the signal intensity of flowing material. In addition, phase‐encoding ghost artifacts are eliminated from the neighborhood of the vessel. Image acquisition time is minimized by acquiring only the low‐frequency phase‐encoding lines in the cardiac‐phase–specific mode. In healthy volunteers, greatly improved MR angiograms of the lower extremities are obtained. Fat saturation and magnetization transfer further enhance vessel/background contrast. Acquiring data only during systole ensures rapid inflow for all phase‐encoding lines, permitting a near‐longitudinal section orientation without in‐plane saturation. This substantially reduces total acquisition time relative to axial acquisition.