Excitation of arbitrary shapes by gradient optimized random walk in discrete k-space

Igor Serša, Slobodan Macura

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


A new technique for the excitation of arbitrary shapes is proposed. It is based on a parallel sequence of small tip angle RF pulses and gradient pulses. The small tip angle rotations co-add yielding a 90°excitation pulse within the selected excitation profile while outside the profile, the rotations cancel each other. A full theory of the completely arbitrary regional volume excitation (CARVE) method is presented and experimentally verified. In CARVE, k-space is discrete because the RF is applied in pulses. The discrete character of k-space permits an arbitrary trajectory for the k- space walk. The optimal random trajectory is found by minimizing the gradient load using simulated annealing. It is shown, both theoretically and experimentally, that such a trajectory is much better than any other systematic or random trajectory in k-space.

Original languageEnglish (US)
Pages (from-to)920-931
Number of pages12
JournalMagnetic Resonance in Medicine
Issue number6
StatePublished - Jun 1997


  • Gradient load optimization
  • Volume selective excitation
  • k-space trajectories

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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