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@ARTICLE{Eberhardt:878351,
      author       = {Eberhardt, Boris and Poser, Benedikt A. and Shah, N. Jon
                      and Felder, Jorg},
      title        = {{A}pplication of {E}volution {S}trategies to the {D}esign
                      of {SAR} {E}fficient {P}arallel {T}ransmit {M}ulti-{S}poke
                      {P}ulses for {U}ltra-{H}igh {F}ield {MRI}},
      journal      = {IEEE transactions on medical imaging},
      volume       = {39},
      number       = {12},
      issn         = {1558-254X},
      address      = {New York, NY},
      publisher    = {IEEE},
      reportid     = {FZJ-2020-02798},
      pages        = {4225 - 4236},
      year         = {2020},
      abstract     = {We present an evolution-strategy based approach to solve
                      the magnitude least squares (MLS) design problem of low
                      flip-angle slice-selective parallel transmit RF pulses for
                      ultra-high field MRI using SAR and peak-RF-constraints. A
                      combined transmit k-space trajectory and RF pulse weight
                      optimization is proposed in two algorithmic steps. The first
                      step is a coarse grid search to find an initial solution
                      that fulfills all constraints for the subsequent multistage
                      optimization. This avoids convergence to the next nearest
                      local minimum. The second step attempts to refine the
                      results using multiple evolution strategies. We compare the
                      performance of our approach with the non-convex optimization
                      methods described in the literature. The proposed algorithm
                      converges for phantom and in vivo data and only requires an
                      initial estimate of the range of suitable regularization
                      parameters. It demonstrates improved excitation homogeneity
                      compared to published spoke-design methods and allows
                      optimization for homogeneity with a subsequent reduction in
                      the SAR burden. Moreover, excitation homogeneity and the SAR
                      burden can be balanced against each other, enabling a
                      further reduction in SAR at the cost of minor relaxations in
                      excitation homogeneity. This feature makes the algorithm a
                      good candidate for SAR limited sequences in ultra-high field
                      imaging. The algorithm is validated using phantom and in
                      vivo measurements obtained with a 16-channel transmit array
                      at 9.4T.},
      cin          = {INM-4 / INM-11 / JARA-BRAIN},
      ddc          = {620},
      cid          = {I:(DE-Juel1)INM-4-20090406 / I:(DE-Juel1)INM-11-20170113 /
                      I:(DE-Juel1)VDB1046},
      pnm          = {573 - Neuroimaging (POF3-573)},
      pid          = {G:(DE-HGF)POF3-573},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:32763849},
      UT           = {WOS:000595547500041},
      doi          = {10.1109/TMI.2020.3013982},
      url          = {https://juser.fz-juelich.de/record/878351},
}