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@ARTICLE{Freedman:130781,
      author       = {J. N. Freedman and D. J. Collins and H. Bainbridge and C.
                      Rank$^*$ and S. Nill and M. Kachelrieß$^*$ and U. Oelfke
                      and M. O. Leach and A. Wetscherek},
      title        = {{T}2-{W}eighted 4{D} {M}agnetic {R}esonance {I}maging for
                      {A}pplication in {M}agnetic {R}esonance-{G}uided
                      {R}adiotherapy {T}reatment {P}lanning.},
      journal      = {Investigative radiology},
      volume       = {52},
      number       = {10},
      issn         = {0020-9996},
      address      = {Philadelphia, Pa.},
      publisher    = {Lippincott Williams $\&$ Wilkins},
      reportid     = {DKFZ-2017-05859},
      pages        = {563 - 573},
      year         = {2017},
      abstract     = {The aim of this study was to develop and verify a method to
                      obtain good temporal resolution T2-weighted 4-dimensional
                      (4D-T2w) magnetic resonance imaging (MRI) by using motion
                      information from T1-weighted 4D (4D-T1w) MRI, to support
                      treatment planning in MR-guided radiotherapy.Ten patients
                      with primary non-small cell lung cancer were scanned at 1.5
                      T axially with a volumetric T2-weighted turbo spin echo
                      sequence gated to exhalation and a volumetric T1-weighted
                      stack-of-stars spoiled gradient echo sequence with golden
                      angle spacing acquired in free breathing. From the latter,
                      20 respiratory phases were reconstructed using the recently
                      developed 4D joint MoCo-HDTV algorithm based on the
                      self-gating signal obtained from the k-space center. Motion
                      vector fields describing the respiratory cycle were obtained
                      by deformable image registration between the respiratory
                      phases and projected onto the T2-weighted image volume. The
                      resulting 4D-T2w volumes were verified against the 4D-T1w
                      volumes: an edge-detection method was used to measure the
                      diaphragm positions; the locations of anatomical landmarks
                      delineated by a radiation oncologist were compared and
                      normalized mutual information was calculated to evaluate
                      volumetric image similarity.High-resolution 4D-T2w MRI was
                      obtained. Respiratory motion was preserved on calculated
                      4D-T2w MRI, with median diaphragm positions being consistent
                      with less than 6.6 mm (2 voxels) for all patients and less
                      than 3.3 mm (1 voxel) for 9 of 10 patients. Geometrical
                      positions were coherent between 4D-T1w and 4D-T2w MRI as
                      Euclidean distances between all corresponding anatomical
                      landmarks agreed to within 7.6 mm (Euclidean distance of 2
                      voxels) and were below 3.8 mm (Euclidean distance of 1
                      voxel) for 355 of 470 pairs of anatomical landmarks.
                      Volumetric image similarity was commensurate between 4D-T1w
                      and 4D-T2w MRI, as mean percentage differences in normalized
                      mutual information (calculated over all respiratory phases
                      and patients), between corresponding respiratory phases of
                      4D-T1w and 4D-T2w MRI and the tie-phase of 4D-T1w and
                      3-dimensional T2w MRI, were consistent to $0.41\%$ ±
                      $0.37\%.$ Four-dimensional T2w MRI displayed tumor extent,
                      structure, and position more clearly than corresponding
                      4D-T1w MRI, especially when mobile tumor sites were adjacent
                      to organs at risk.A methodology to obtain 4D-T2w MRI that
                      retrospectively applies the motion information from 4D-T1w
                      MRI to 3-dimensional T2w MRI was developed and verified.
                      Four-dimensional T2w MRI can assist clinicians in
                      delineating mobile lesions that are difficult to define on
                      4D-T1w MRI, because of poor tumor-tissue contrast.},
      cin          = {E020 / E025},
      ddc          = {610},
      cid          = {I:(DE-He78)E020-20160331 / I:(DE-He78)E025-20160331},
      pnm          = {315 - Imaging and radiooncology (POF3-315)},
      pid          = {G:(DE-HGF)POF3-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:28459800},
      pmc          = {pmc:PMC5581953},
      doi          = {10.1097/RLI.0000000000000381},
      url          = {https://inrepo02.dkfz.de/record/130781},
}