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@ARTICLE{Emmerich:132884,
      author       = {J. Emmerich$^*$ and F. Laun$^*$ and A. Pfaffenberger$^*$
                      and R. Schilling and M. Denoix$^*$ and F. Maier$^*$ and F.
                      Sterzing$^*$ and T. Bostel$^*$ and S. Straub$^*$},
      title        = {{T}echnical {N}ote: {O}n the size of susceptibility-induced
                      {MR} image distortions in prostate and cervix in the context
                      of {MR}-guided radiation therapy.},
      journal      = {Medical physics},
      volume       = {45},
      number       = {4},
      issn         = {0094-2405},
      address      = {New York, NY},
      reportid     = {DKFZ-2018-00526},
      pages        = {1586 - 1593},
      year         = {2018},
      abstract     = {To investigate the extent of MR image distortions in the
                      pelvis caused by susceptibility-induced field
                      inhomogeneities in MR images in the context of a study on
                      MR-guided radiotherapy.Using a high-bandwidth double-echo
                      gradient echo sequence, field maps and distortion maps of
                      the pelvis were calculated and evaluated for 219 exams (92
                      of female and 127 of male patients) to investigate
                      patient-related image distortions caused by susceptibility
                      differences in an ongoing study on MR-guided radiotherapy.
                      The evaluation of distortions in the regions 'rectum',
                      'prostate', 'cervix', and in a reference region in the
                      gluteus maximus was based on masks drawn by two
                      readers.Distortions in the prostate and cervix were smaller
                      than 0.03 px (0.1 mm) for $99\%$ of voxels, and reached a
                      maximum value of 0.09 px (0.3 mm). In the reference
                      region, maximum distortions were smaller than in the
                      prostate and cervix.Using a geometric uncertainty of 0.2 px
                      (0.6 mm) in margin definition for organs that are close to
                      the rectum like the prostate and the cervix would be a
                      cautious choice to account for susceptibility-induced
                      distortions that can arise during MR-based treatment
                      guidance for the imaging setting used in this study. Since
                      distortions are inversely proportional to the readout
                      bandwidth of the sequence, safety margins need to be adapted
                      adequately. Additional sources of image distortions like
                      gradient nonlinearities are not included in our margin
                      recommendations and should be considered separately.},
      cin          = {E020 / E040 / E050},
      ddc          = {610},
      cid          = {I:(DE-He78)E020-20160331 / I:(DE-He78)E040-20160331 /
                      I:(DE-He78)E050-20160331},
      pnm          = {315 - Imaging and radiooncology (POF3-315)},
      pid          = {G:(DE-HGF)POF3-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:29394448},
      doi          = {10.1002/mp.12785},
      url          = {https://inrepo02.dkfz.de/record/132884},
}