K-space sampling techniques for CE MRA
  The simplest approach is a sequential phase encoding order in which k-space lines are filled in sequence from bottom to top, with the start of the scan coinciding with the arrival of the bolus and continuous infusion of contrast throughout imaging. In a modification of this technique, sequential-order k-space filling is used but the start of scanning is timed so that peak arterial enhancement matches the acquisition of central k-space views. Another method involves centric or elliptical centric phase-encoding order; central k-space data are sampled earliest in the acquisition, which, if bolus timing is correct, will correspond to maximal peak arterial enhancement with minimal venous overlap.