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@ARTICLE{Orzada:303374,
      author       = {S. Orzada$^*$ and T. M. Fiedler$^*$ and J. Kesting$^*$ and
                      M. J. Hubmann and M. Ladd$^*$},
      title        = {{O}n the measurement errors in {SAR} supervision introduced
                      by directional couplers.},
      journal      = {Magnetic resonance materials in physics, biology and
                      medicine},
      volume       = {nn},
      issn         = {0968-5243},
      address      = {Heidelberg},
      publisher    = {Springer},
      reportid     = {DKFZ-2025-01623},
      pages        = {nn},
      year         = {2025},
      note         = {#EA:E020#LA:E020# / epub},
      abstract     = {This study proposes a framework for determining the
                      calculation error in online SAR supervision introduced by
                      directional couplers.A mathematical framework is introduced
                      showing how the error in the measured excitation vector
                      compared to the actual excitation vector can be rewritten as
                      a new set of virtual observation points (VOPs). By comparing
                      the new set of VOPs to the original VOPs through an
                      optimization, the maximum underestimation of SAR can be
                      calculated. The framework is then applied to five different
                      RF arrays.The results show that the error in SAR calculation
                      is very dependent on the position of the reference plane of
                      the directional coupler measurements and the S-parameters of
                      the array. To have an error of less than $5\%,$ directional
                      couplers with a directivity better than 40 dB are necessary
                      for the worst case of the investigated arrays.The framework
                      presented in this paper provides an approach for calculating
                      a safety factor to account for the inaccuracies introduced
                      by directional coupler measurements in online SAR
                      supervision. The framework can also be adapted to other
                      types of measurements.},
      keywords     = {Directional couplers (Other) / MRI (Other) / Measurement
                      error (Other) / SAR (Other) / Virtual observation points
                      (Other) / pTx (Other)},
      cin          = {E020},
      ddc          = {530},
      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:40759812},
      doi          = {10.1007/s10334-025-01287-7},
      url          = {https://inrepo02.dkfz.de/record/303374},
}