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@ARTICLE{JorisHubmann:300267,
      author       = {M. Joris Hubmann and S. Orzada$^*$ and R. Kowal and J.
                      Anton Grimm$^*$ and O. Speck and H. Maune},
      title        = {{T}owards {L}arge {D}iameter {T}ransmit {C}oils for 7-{T}
                      {H}ead {I}maging: {A} {D}etailed {C}omparison of a {S}et of
                      {T}ransmit {E}lement {D}esign {C}oncepts.},
      journal      = {NMR in biomedicine},
      volume       = {38},
      number       = {5},
      issn         = {0952-3480},
      address      = {New York, NY},
      publisher    = {Wiley},
      reportid     = {DKFZ-2025-00720},
      pages        = {e70030},
      year         = {2025},
      abstract     = {Many different transmit (Tx) coil concepts and designs for
                      7-T magnetic resonance imaging of the head have been
                      proposed. Most of them are placed close to the head and in
                      combination with the receive coils creating a helmet-like
                      structure. This limits the space for additional equipment
                      for external stimuli. A large diameter transmit coil can
                      increase the ease using supplementary measurement devices.
                      Therefore, this study systematically evaluated nine
                      different Tx elements regarding their performance within a
                      large diameter transmit coil with a diameter > $$ > $$ 350
                      mm. Each Tx element was examined regarding its power and
                      specific absorption rate (SAR) efficiencies, its loading
                      dependence, intrinsic decoupling, and its radio frequency
                      (RF) shimming capability. Additionally, an experimental
                      validation of | B 1 + | $$ \mid {B}_1^{+}\mid $$ -maps was
                      performed. The loop-based Tx elements (circular and
                      rectangular loop) provided the highest power and SAR
                      efficiency with at least 15.5\% and 21.2\% higher
                      efficiencies for a single channel and 22.1\% and 18.0\% for
                      the eight-channel array, respectively. In terms of
                      voxel-wise power efficiency, the circular loop was the
                      superior Tx element type within most of the head. Looking at
                      the voxel-wise SAR efficiency, the loop-based elements
                      manifest themselves as the most efficient type within most
                      of the central brain. The mutual coupling was lowest for the
                      passively fed dipole ( - $$ - $$ 31.23 dB). The highest RF
                      shimming capability in terms of sum of normalized singular
                      values was calculated for the rectangular (4.21) and the
                      circular loop (4.36), whereby the L-curve results showed
                      that the arrays have only minor | B 1 + | $$ \mid
                      {B}_1^{+}\mid $$ shimming performance differences for the
                      transversal slice. For the hippocampus, the meander element
                      provided the highest overall homogeneity with a minimal
                      coefficient of variation (CoV) of 5.1\%. This work provides
                      extensive and unique data for single and eight-channel Tx
                      elements applying common performance benchmarks and enables
                      further discourse on multi-channel evaluations towards large
                      diameter Tx coils at 7-T head imaging. On the bases of the
                      provided results, the preferable Tx element type for this
                      specific application is loop-based.},
      keywords     = {Magnetic Resonance Imaging: instrumentation / Head:
                      diagnostic imaging / Equipment Design / Humans / Phantoms,
                      Imaging / Brain: diagnostic imaging / 7 T MRI (Other) / EM
                      simulations (Other) / RF coils (Other) / RF shimming (Other)
                      / UHF (Other) / antennas (Other) / hardware (Other) / head
                      imaging (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:40186518},
      pmc          = {pmc:PMC11971727},
      doi          = {10.1002/nbm.70030},
      url          = {https://inrepo02.dkfz.de/record/300267},
}