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@ARTICLE{Herrler:166677,
      author       = {J. Herrler and P. Liebig and R. Gumbrecht and D. Ritter and
                      S. Schmitter and A. Maier and M. Schmidt and M. Uder and A.
                      Doerfler and A. Nagel$^*$},
      title        = {{F}ast online-customized ({FOCUS}) parallel transmission
                      pulses: {A} combination of universal pulses and individual
                      optimization.},
      journal      = {Magnetic resonance in medicine},
      volume       = {85},
      number       = {6},
      issn         = {1522-2594},
      address      = {New York, NY [u.a.]},
      publisher    = {Wiley-Liss},
      reportid     = {DKFZ-2021-00030},
      pages        = {3140-3153},
      year         = {2021},
      note         = {#LA:E020#2021 Jun;85(6):3140-3153},
      abstract     = {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 = $~28\%,$ UPs = $~17\%,$ and IOPs = $~12\%).$ UPs
                      and IOPs improved homogeneity for all subjects. Differences
                      in NRMSE between study groups were much lower than
                      differences between different pulse types.UPs can be used to
                      generate fast online-customized (FOCUS) pulses gaining lower
                      NRMSE and/or lower SAR values.},
      keywords     = {7 T (Other) / SPINS (Other) / kT points (Other) / parallel
                      transmission (pTx) (Other) / ultra-high-field MRI (Other) /
                      universal pulses (Other)},
      cin          = {E020},
      ddc          = {610},
      cid          = {I:(DE-He78)E020-20160331},
      pnm          = {315 - Bildgebung und Radioonkologie (POF4-315)},
      pid          = {G:(DE-HGF)POF4-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:33400302},
      doi          = {10.1002/mrm.28643},
      url          = {https://inrepo02.dkfz.de/record/166677},
}