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@ARTICLE{Lutz:302139,
      author       = {M. Lutz and S. Flassbeck and C. S. Aigner and F. Krueger
                      and T. Schaeffter and S. Schmitter$^*$},
      title        = {{A}ccurate {MRF}-{B}ased 3{D} {M}ulti-{C}hannel {B}1 +
                      {M}apping in the {H}uman {B}ody at 7 {T}.},
      journal      = {NMR in biomedicine},
      volume       = {38},
      number       = {8},
      issn         = {0952-3480},
      address      = {New York, NY},
      publisher    = {Wiley},
      reportid     = {DKFZ-2025-01257},
      pages        = {e70080},
      year         = {2025},
      note         = {#LA:E020#},
      abstract     = {This work proposes a 3D multi-transmit channel B1 + mapping
                      approach based on magnetic resonance fingerprinting (MRF)
                      for the human abdomen at 7 T. A stack-of-stars acquisition
                      is employed to achieve motion-robust 3D encoding, along with
                      a hybrid method where transmit (Tx) channel-wise B1 +
                      information is obtained through low flip angle GRE images.
                      B1 + mapping at ultra-high field (UHF) in the human abdomen
                      is particularly challenging due to the large dynamic range
                      of B1 +, the extensive field of view (FOV), and the effects
                      of respiratory motion. Few methods have been proposed to
                      address these challenges, with a significant limitation
                      being the relatively low RF power available at UHF,
                      especially for pTx systems with a 8 × 1 kW power
                      configuration. This limitation makes it difficult to achieve
                      FAs greater than 30° in central body regions, which are
                      required for accurate results with classical methods. In
                      contrast, Tx channel-combined MRF-based B1 + mapping has
                      been validated as accurate for FAs greater than 6°,
                      offering improved accuracy at low FAs. Here, two Tx
                      channel-combined MRF-based B1 + maps (B1-MRF) are acquired
                      using two tailored complementary phase shims to obtain
                      absolute B1 + information across the entire FOV. The 3D
                      hybrid approach was validated against a 2D reference using
                      phantoms and in vivo free-breathing scans in three subjects
                      with varying BMIs, where only one Tx channel was active at a
                      time. The comparison showed strong agreement, with the 3D
                      hybrid acquisition demonstrating improved performance in
                      regions affected by flow, low FAs, or low signal-to-noise
                      ratio compared to the 2D implementation. The higher accuracy
                      and level of detail provided by the proposed method, in
                      contrast to existing methods, are particularly relevant for
                      several applications, including the validation of faster
                      approaches, validation of electromagnetic simulations (which
                      are safety-critical), and the creation of B1 + map libraries
                      for applications such as AI-based B1 + mapping or universal
                      pulse calculations.},
      keywords     = {Humans / Imaging, Three-Dimensional / Magnetic Resonance
                      Imaging / Phantoms, Imaging / Adult / Male / Female / 7
                      Tesla (Other) / B1+ mapping (Other) / MRF (Other) / body MRI
                      (Other) / ultrahigh field MRI (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:40533359},
      pmc          = {pmc:PMC12176530},
      doi          = {10.1002/nbm.70080},
      url          = {https://inrepo02.dkfz.de/record/302139},
}