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Array‐compressed parallel transmit pulse design
Author(s) -
Cao Zhipeng,
Yan Xinqiang,
Grissom William A.
Publication year - 2016
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.26020
Subject(s) - sparse array , parallel communication , compressed sensing , computer science , electromagnetic coil , pulse (music) , radio frequency , acoustics , pulse compression , excitation , electronic engineering , optics , physics , transmission (telecommunications) , algorithm , telecommunications , electrical engineering , engineering , radar , detector
Purpose To design array‐compressed parallel transmit radiofrequency (RF) pulses and compare them to pulses designed with existing transmit array compression strategies. Theory and Methods Array‐compressed parallel RF pulse design is proposed as the joint optimization of a matrix of complex‐valued compression weights that relate a full‐channel physical array to a reduced‐channel virtual array, along with a set of RF pulses for the virtual array. In this way, the physics of the RF pulse application determine the coil combination weights. Array‐compressed pulse design algorithms are described for four parallel transmit applications: accelerated two‐dimensional spiral excitation, multislice RF shimming, small‐tip‐angle k T ‐points excitation, and slice‐selective spokes refocusing. Array‐compressed designs are compared in simulations and an experiment to pulses designed using four existing array compression strategies. Results In all cases, array‐compressed pulses achieved the lowest root‐mean‐square excitation error among the array compression approaches. Low errors were generally achieved without increasing root‐mean‐square RF amplitudes or maximum local 10‐gram specific absorption rate. Leave‐one‐out multisubject shimming simulations demonstrated that array‐compressed RF shimming can identify useful fixed coil combination weights that perform well across a population. Conclusion Array‐compressed pulse design jointly identifies the transmit coil array compression weights and RF pulses that perform best for a specific parallel excitation application. Magn Reson Med 76:1158–1169, 2016. © 2015 Wiley Periodicals, Inc.