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Magn Reson Med. 2009 Jun;61(6):1471-9. doi: 10.1002/mrm.21950.

Time-optimal design for multidimensional and parallel transmit variable-rate selective excitation.

Author information

  • 1Department of Electrical Engineering, Magnetic Resonance Systems Research Laboratory, Stanford University, Stanford, California, USA. daeho@mrsrl.stanford.edu

Abstract

Variable-rate selective excitation (VERSE) is a radio frequency (RF) pulse reshaping technique. It is most commonly used to reduce the peak magnitude and specific absorption rate (SAR) of RF pulses by reshaping pulses and gradient waveforms to reduce RF magnitude while preserving excitation profiles. In this work, a general time-optimal VERSE algorithm for multidimensional and parallel transmit pulses is presented. Time optimality is achieved by translating peak RF limits to gradient upper bounds in excitation k-space. The limits are fed into a time-optimal gradient waveform design technique. Effective SAR reduction is achieved by reducing peak RF subject to a fixed pulse length. The presented method is different from other VERSE techniques in that it provides a noniterative time-optimal multidimensional solution, which drastically simplifies VERSE designs. Examples are given for 1D and 2D single channel and 2D parallel transmit pulses.

PMID:
19365849
[PubMed - indexed for MEDLINE]
PMCID:
PMC2764012
Free PMC Article

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