A flexible view ordering technique for high-quality real-time 2DFT MR fluoroscopy

A method to tailor the view order to the reconstruction cycle is introduced for real-time MRI. it is well known that view sharing and oversampling cen tral k-space views can improve the temporal resolution of gradient-echo pul se sequences. By ordering phase-encodes to synchronize k-space acquisition with the reconstruction cycle, apparent temporal resolution can match the f rame rate with as few as one-fourth of the phase-encodes sampled per recons truction. Spatial resolution is maintained by periodically updating high sp atial frequencies. In addition to apparent temporal resolution, three other criteria for real-time imaging are identified and evaluated: display laten cy, dispersion, and frame-to-frame consistency. Latency is minimized by ord ering views in a reverse-centric manner within each reconstruction interval , sampling high-energy views immediately prior to beginning reconstruction. Dispersion is kept low and consistent by synchronizing acquisition and rec onstruction, thus avoiding poorly timed reconstruction instances. Real-time implementation demonstrates pulsatile time-of-flight blood signal enhancem ent in humans. Magn Reson Med 42:69-81, 1999. (C) 1999 Wiley-Liss, Inc.