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@ARTICLE{Blmer:276344,
      author       = {Blömer, Simon and Hingerl, Lukas and Marjańska,
                      Małgorzata and Bogner, Wolfgang and Motyka, Stanislav and
                      Hangel, Gilbert and Klauser, Antoine and Andronesi, Ovidiu C
                      and Strasser, Bernhard},
      title        = {{P}roton-free induction decay {MRSI} at 7 {T} in the human
                      brain using an egg-shaped modified rosette {K}-space
                      trajectory.},
      journal      = {Magnetic resonance in medicine},
      volume       = {93},
      number       = {4},
      issn         = {1522-2594},
      address      = {New York, NY [u.a.]},
      publisher    = {Wiley-Liss},
      reportid     = {DZNE-2025-00292},
      pages        = {1443 - 1457},
      year         = {2025},
      abstract     = {Proton (1H)-MRSI via spatial-spectral encoding poses high
                      demands on gradient hardware at ultra-high fields and
                      high-resolutions. Rosette trajectories help alleviate these
                      problems, but at reduced SNR-efficiency because of their
                      k-space densities not matching any desired k-space filter.
                      We propose modified rosette trajectories, which more closely
                      match a Hamming filter, and thereby improve SNR performance
                      while still staying within gradient hardware limitations and
                      without prolonging scan time.Analytical and synthetic
                      simulations were validated with phantom and in vivo
                      measurements at 7 T. The rosette and modified rosette
                      trajectories were measured in five healthy volunteers in 6
                      min in a 2D slice in the brain. An elliptical phase-encoding
                      sequence was measured in one volunteer in 22 min, and a 3D
                      sequence was measured in one volunteer within 19 min. The
                      SNR per-unit-time, linewidth, Cramer-Rao lower bounds
                      (CRLBs), lipid contamination, and data quality of the
                      proposed modified rosette trajectory were compared to the
                      rosette trajectory.Using the modified rosette trajectories,
                      an improved k-space weighting function was achieved
                      resulting in an SNR per-unit-time increase of up to $12\%$
                      compared to rosette's and $23\%$ compared to elliptical
                      phase-encoding, dependent on the two additional trajectory
                      parameters. Similar results were achieved for the
                      theoretical SNR calculation based on k-space densities, as
                      well as when using the pseudo-replica method for simulated,
                      in vivo, and phantom data. The CRLBs of γ-aminobutyric acid
                      and N-acetylaspartylglutamate improved non-significantly for
                      the modified rosette trajectory, whereas the linewidths and
                      lipid contamination remained similar.By optimizing the shape
                      of the rosette trajectory, the modified rosette trajectories
                      achieved higher SNR per-unit-time and enhanced data quality
                      at the same scan time.},
      keywords     = {Humans / Phantoms, Imaging / Brain: diagnostic imaging /
                      Algorithms / Signal-To-Noise Ratio / Adult / Magnetic
                      Resonance Imaging: methods / Protons / Computer Simulation /
                      Male / Reproducibility of Results / Female / Image
                      Processing, Computer-Assisted: methods / Healthy Volunteers
                      / 7 T (Other) / SNR efficiency (Other) / gradient hardware
                      restrictions (Other) / magnetic resonance spectroscopic
                      imaging (Other) / modified rosette trajectory (Other) /
                      non‐Cartesian trajectory (Other) / Protons (NLM
                      Chemicals)},
      cin          = {Patient Studies (Bonn)},
      ddc          = {610},
      cid          = {I:(DE-2719)1011101},
      pnm          = {353 - Clinical and Health Care Research (POF4-353)},
      pid          = {G:(DE-HGF)POF4-353},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:39568225},
      pmc          = {pmc:PMC11782714},
      doi          = {10.1002/mrm.30368},
      url          = {https://pub.dzne.de/record/276344},
}