TY  - JOUR
AU  - Herrler, Jürgen
AU  - Liebig, Patrick
AU  - Gumbrecht, Rene
AU  - Ritter, Dieter
AU  - Schmitter, Sebastian
AU  - Maier, Andreas
AU  - Schmidt, Manuel
AU  - Uder, Michael
AU  - Doerfler, Arnd
AU  - Nagel, Armin
TI  - Fast online-customized (FOCUS) parallel transmission pulses: A combination of universal pulses and individual optimization.
JO  - Magnetic resonance in medicine
VL  - 85
IS  - 6
SN  - 1522-2594
CY  - New York, NY [u.a.]
PB  - Wiley-Liss
M1  - DKFZ-2021-00030
SP  - 3140-3153
PY  - 2021
N1  - #LA:E020#2021 Jun;85(6):3140-3153
AB  - To mitigate spatial flip angle (FA) variations under strict specific absorption rate (SAR) constraints for ultra-high field MRI using a combination of universal parallel transmit (pTx) pulses and fast subject-specific optimization.Data sets consisting of B0 , B 1 + maps, and virtual observation point (VOP) data were acquired from 72 subjects (study groups of 48/12 healthy Europeans/Asians and 12 Europeans with pathological or incidental findings) using an 8Tx/32Rx head coil on a 7T whole-body MR system. Combined optimization values (COV) were defined as combination of spiral-nonselective (SPINS) trajectory parameters and an energy regularization weight. A set of COV was optimized universally by simulating the individual RF pulse optimizations of 12 training data sets (healthy Europeans). Subsequently, corresponding universal pulses (UPs) were calculated. Using COV and UPs, individually optimized pulses (IOPs) were calculated during the sequence preparation phase (maximum 15 s). Two different UPs and IOPs were evaluated by calculating their normalized root-mean-square error (NRMSE) of the FA and SAR in simulations of all data sets. Seven additional subjects were examined using an MPRAGE sequence that uses the designed pTx excitation pulses and a conventional adiabatic inversion.All pTx pulses resulted in decreased mean NRMSE compared to a circularly polarized (CP) pulse (CP =  28
KW  - 7 T (Other)
KW  - SPINS (Other)
KW  - kT points (Other)
KW  - parallel transmission (pTx) (Other)
KW  - ultra-high-field MRI (Other)
KW  - universal pulses (Other)
LB  - PUB:(DE-HGF)16
C6  - pmid:33400302
DO  - DOI:10.1002/mrm.28643
UR  - https://inrepo02.dkfz.de/record/166677
ER  -