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@ARTICLE{Thummerer:165913,
      author       = {A. Thummerer and B. A. de Jong and P. Zaffino and A.
                      Meijers and G. G. Marmitt and J. Seco$^*$ and R. J. H. M.
                      Steenbakkers and J. A. Langendijk and S. Both and M. F.
                      Spadea and A.-C. Knopf},
      title        = {{C}omparison of the suitability of {CBCT}- and {MR}-based
                      synthetic {CT}s for daily adaptive proton therapy in head
                      and neck patients.},
      journal      = {Physics in medicine and biology},
      volume       = {65},
      number       = {23},
      issn         = {1361-6560},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {DKFZ-2020-02470},
      pages        = {235036},
      year         = {2020},
      abstract     = {CBCT- and MR-images allow a daily observation of patient
                      anatomy but are not directly suited for accurate proton dose
                      calculations. This can be overcome by creating synthetic CTs
                      (sCT) using deep convolutional neural networks (DCNN). In
                      this study, we compared sCTs based on CBCTs and MRs for head
                      and neck cancer patients in terms of image quality and
                      proton dose calculation accuracy. A dataset of 27
                      $H\&N-patients,$ treated with proton therapy, containing
                      planning CTs, repeat CTs, CBCTs and MRs were used to train
                      two neural networks to convert either CBCTs or MRs into
                      synthetic CTs. Image quality was quantified by calculating
                      mean absolute error (MAE), mean error (ME) and dice
                      similarity coefficient (DSC) for bones. The dose evaluation
                      consisted of a systematic non-clinical analysis and a
                      clinical recalculation of actually used proton treatment
                      plans. Gamma analysis was performed for non-clinical and
                      clinical treatment plans. For clinical treatment plans also
                      dose to targets and organs at risk (OARs) and normal tissue
                      complication probabilities (NTCP) were compared. CBCT-based
                      sCTs resulted in higher image quality with an average MAE of
                      40±4 HU and a DSC of 0.95, while for MR-based sCTs a MAE of
                      65±4 HU and a DSC of 0.89 was observed. Also in clinical
                      proton dose calculations, sCTCBCT achieved higher average
                      gamma pass ratios $(2\%/2mm$ criterion) than sCTMR $(96.1\%$
                      vs. $93.3\%).$ Dose-volume histograms for selected OARs and
                      NTCP-values showed a very small difference between sCTCBCT
                      and sCTMR and a high agreement with the reference
                      planning-CT. CBCT- and MR-based sCTs have the potential to
                      enable accurate proton dose calculations valuable for daily
                      adaptive proton therapy. Significant image quality
                      differences were observed but did not affect proton dose
                      calculation accuracy in a similar manner. Especially the
                      recalculation of clinical treatment plans showed high
                      agreement with the planning CT for both sCTCBCT and sCTMR.},
      cin          = {E041},
      ddc          = {530},
      cid          = {I:(DE-He78)E041-20160331},
      pnm          = {315 - Imaging and radiooncology (POF3-315)},
      pid          = {G:(DE-HGF)POF3-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:33179874},
      doi          = {10.1088/1361-6560/abb1d6},
      url          = {https://inrepo02.dkfz.de/record/165913},
}