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@ARTICLE{Vlzke:273901,
      author       = {Völzke, Yannik and Akbey, Suzan and Löwen, Daniel and
                      Pracht, Eberhard Daniel and Stirnberg, Rüdiger and Gras,
                      Vincent and Boulant, Nicolas and Zaiss, Moritz and Stöcker,
                      Tony},
      title        = {{C}alibration-free whole-brain {CEST} imaging at 7{T} with
                      parallel transmit pulse design for saturation homogeneity
                      utilizing universal pulses ({PUSHUP}).},
      journal      = {Magnetic resonance in medicine},
      volume       = {93},
      number       = {2},
      issn         = {1522-2594},
      address      = {New York, NY [u.a.]},
      publisher    = {Wiley-Liss},
      reportid     = {DZNE-2024-01380},
      pages        = {630 - 642},
      year         = {2025},
      abstract     = {Chemical exchange saturation transfer (CEST) measurements
                      at ultra-high field (UHF) suffer from strong saturation
                      inhomogeneity. Retrospective correction of this
                      inhomogeneity is possible to some extent, but requires a
                      time-consuming repetition of the measurement. Here, we
                      propose a calibration-free parallel transmit (pTx)-based
                      saturation scheme that homogenizes the saturation over the
                      imaging volume, which we call PUlse design for Saturation
                      Homogeneity utilizing Universal Pulses
                      (PUSHUP).Magnetization transfer effects depend on the
                      saturation B 1 rms $$ {\mathrm{B}}_1^{\mathrm{rms}} $$ .
                      PUSHUP homogenizes the saturation B 1 rms $$
                      {\mathrm{B}}_1^{\mathrm{rms}} $$ by using multiple
                      saturation pulses with alternating B 1 $$ {\mathrm{B}}_1 $$
                      -shims. Using a database of B 1 $$ {\mathrm{B}}_1 $$ maps,
                      universal pulses are calculated that remove the necessity of
                      time-consuming, subject-based pulse calculation during the
                      measurement.PUSHUP was combined with a whole-brain
                      three-dimensional-echo planar imaging (3D-EPI) readout. Two
                      PUSHUP saturation modules were calculated by either applying
                      whole-brain or cerebellum masks to the database maps. The
                      saturation homogeneity and the group mean CEST amplitudes
                      were calculated for different B 1 $$ {\mathrm{B}}_1 $$
                      -correction methods and were compared to circular polarized
                      (CP) saturation in five healthy volunteers using an
                      eight-channel transmit coil at 7 Tesla.In contrast to CP
                      saturation, where accurate CEST maps were impossible to
                      obtain in the cerebellum, even with extensive B 1 $$
                      {\mathrm{B}}_1 $$ -correction, PUSHUP CEST maps were
                      artifact-free throughout the whole brain. A 1-point
                      retrospective B 1 $$ {\mathrm{B}}_1 $$ -correction, that
                      does not need repeated measurements, sufficiently removed
                      the effect of residual saturation inhomogeneity.The
                      presented method allows for homogeneous whole-brain CEST
                      imaging at 7 Tesla without the need of a repetition-based B
                      1 $$ {\mathrm{B}}_1 $$ -correction or online pulse
                      calculation. With the fast 3D-EPI readout, whole-brain CEST
                      imaging with 45 saturation offsets is possible at 1.6 mm
                      resolution in under 4 min.},
      keywords     = {Humans / Brain: diagnostic imaging / Magnetic Resonance
                      Imaging: methods / Algorithms / Image Processing,
                      Computer-Assisted: methods / Phantoms, Imaging / Calibration
                      / Adult / Male / Female / CEST (Other) / magnetization
                      transfer (Other) / parallel transmit (Other) / ultra‐high
                      field (Other) / universal pulses (Other)},
      cin          = {AG Stöcker},
      ddc          = {610},
      cid          = {I:(DE-2719)1013026},
      pnm          = {354 - Disease Prevention and Healthy Aging (POF4-354)},
      pid          = {G:(DE-HGF)POF4-354},
      typ          = {PUB:(DE-HGF)16},
      pmc          = {pmc:PMC11604840},
      pubmed       = {pmid:39301770},
      doi          = {10.1002/mrm.30305},
      url          = {https://pub.dzne.de/record/273901},
}