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@ARTICLE{Schwerter:862711,
      author       = {Schwerter, Michael and Hetherington, Hoby and Moon, Chan
                      Hong and Pan, Jullie and Felder, Jörg and Tellmann, Lutz
                      and Shah, N. J.},
      title        = {{I}nterslice current change constrained {B} 0 shim
                      optimization for accurate high‐order dynamic shim updating
                      with strongly reduced eddy currents},
      journal      = {Magnetic resonance in medicine},
      volume       = {82},
      number       = {1},
      issn         = {1522-2594},
      address      = {New York, NY [u.a.]},
      publisher    = {Wiley-Liss},
      reportid     = {FZJ-2019-02962},
      pages        = {263 - 275},
      year         = {2019},
      abstract     = {PurposeTo overcome existing challenges in dynamic B0
                      shimming by implementing a shim optimization algorithm which
                      limits shim current amplitudes and their temporal variation
                      through the application of constraints and regularization
                      terms.Theory and MethodsSpherical harmonic dynamic B0
                      shimming is complicated by eddy currents, ill‐posed
                      optimizations, and the need for strong power supplies. Based
                      on the fact that eddy current amplitudes are proportional to
                      the magnitude of the shim current changes, and assuming a
                      smoothness of the B0 inhomogeneity variation in the slice
                      direction, a novel algorithm was implemented to reduce eddy
                      current generation by limiting interslice shim current
                      changes. Shim degeneracy issues and resulting high current
                      amplitudes are additionally addressed by penalizing high
                      solution norms. Applicability of the proposed algorithm was
                      validated in simulations and in phantom and in vivo
                      measurements.ResultsHigh‐order dynamic shimming
                      simulations and measurements have shown that absolute shim
                      current amplitudes and their temporal variation can be
                      substantially reduced with negligible loss in achievable B0
                      homogeneity. Whereas conventional dynamic shim updating
                      optimizations improve the B0 homogeneity, on average, by a
                      factor of 2.1 over second‐order static solutions, our
                      proposed routine reached a factor of 2.0, while
                      simultaneously providing a 14‐fold reduction of the
                      average maximum shim current changes.ConclusionsThe proposed
                      algorithm substantially reduces the shim amplitudes and
                      their temporal variation, while only marginally affecting
                      the achievable B0 homogeneity. As a result, it has the
                      potential to mitigate the remaining challenges in dynamic B0
                      shimming and help in making its application more readily
                      available.},
      cin          = {INM-11 / INM-4 / JARA-BRAIN},
      ddc          = {610},
      cid          = {I:(DE-Juel1)INM-11-20170113 / I:(DE-Juel1)INM-4-20090406 /
                      $I:(DE-82)080010_20140620$},
      pnm          = {573 - Neuroimaging (POF3-573)},
      pid          = {G:(DE-HGF)POF3-573},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:30883909},
      UT           = {WOS:000481978800019},
      doi          = {10.1002/mrm.27720},
      url          = {https://juser.fz-juelich.de/record/862711},
}