• Zhipeng Cao, Xinqiang Yan, and William A Grissom.
• Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.
• Magn Reson Med. 2016 Oct 1; 76 (4): 1158-69.

PurposeTo design array-compressed parallel transmit radiofrequency (RF) pulses and compare them to pulses designed with existing transmit array compression strategies.Theory And MethodsArray-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 kT -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.ResultsIn 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.ConclusionArray-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.© 2015 Wiley Periodicals, Inc.

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