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@ARTICLE{LpezMartnez:304493,
      author       = {I. N. López-Martínez$^*$ and M. E. Ladd$^*$ and R.
                      Schmidt and S. Orzada$^*$},
      title        = {{C}omparison of {B} 1 + and {SAR} efficiency for a
                      high-impedance metamaterial shield with different remote
                      {RF} arrays at 7 {T} {MRI}: {A} simulation study.},
      journal      = {Magnetic resonance materials in physics, biology and
                      medicine},
      volume       = {nn},
      issn         = {0968-5243},
      address      = {Heidelberg},
      publisher    = {Springer},
      reportid     = {DKFZ-2025-01882},
      pages        = {nn},
      year         = {2025},
      note         = {#EA:E020#LA:E020# / epub},
      abstract     = {This study explores high-impedance surface (HIS)
                      metamaterial shields for enhancing the transmit field in
                      whole-body MRI at 7 T. We studied the possibility of placing
                      a metamaterial layer between the gradient coil and bore
                      liner using electromagnetic simulations to evaluate B1+ and
                      SAR efficiency across different impedances.Simulations were
                      performed in three stages, first metamaterial design and
                      characterization, then single-element dipole simulations
                      with a homogenous phantom, and finally, simulations
                      including a four-element arrays with a virtual body model,
                      including the whole scanner geometry. Four antenna types
                      were evaluated for B1+ and SAR efficiency.Due to space
                      constraints the metamaterial does not reach high enough
                      impedance, resulting in minimal performance gains for most
                      antennas. However, fractionated dipole arrays with
                      inductances showed increased SAR efficiency and a larger
                      field of view. Higher impedance values (above 1000 Ω)
                      reduced losses and enabled higher-order wave modes,
                      improving efficiency. Intermediate impedances (10⁻2-103
                      Ω) introduced significant losses, potentially causing
                      heating and detuning.HIS metamaterials can enhance transmit
                      performance in 7 T MRI but require careful optimization of
                      impedance, material losses, and antenna design. These
                      factors must be considered to ensure both efficacy and
                      safety in ultra-high-field applications.},
      keywords     = {Electromagnetic simulations (Other) / MRI (Other) /
                      Metamaterials (Other) / Ultra-high field (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:40931282},
      doi          = {doi:10.1007/s10334-025-01295-7},
      url          = {https://inrepo02.dkfz.de/record/304493},
}