Array-compressed parallel transmit pulse design.
To design array-compressed parallel transmit radiofrequency (RF) pulses and compare them to pulses designed with existing transmit array compression strategies.



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 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.



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.



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.
Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.|Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.
Zhipeng
Z
Cao
Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.|Department of Radiology, Vanderbilt University, Nashville, Tennessee, USA.
Xinqiang
X
Yan
Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA. will.grissom@vanderbilt.edu.|Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA. will.grissom@vanderbilt.edu.|Department of Radiology, Vanderbilt University, Nashville, Tennessee, USA. will.grissom@vanderbilt.edu.|Department of Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA. will.grissom@vanderbilt.edu.
William A
WA
Grissom
D000465:Algorithms; D044962:Data Compression / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted
RF pulse design; RF shimming; array compression; kT points pulses; optimization; parallel transmission; selective excitation; singular value decomposition; spokes pulses; tailored excitation