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@ARTICLE{Wild:127790,
      author       = {E. Wild$^*$ and M. Bangert$^*$ and S. Nill and U.
                      Oelfke$^*$},
      title        = {{N}oncoplanar {VMAT} for nasopharyngeal tumors: {P}lan
                      quality versus treatment time.},
      journal      = {Medical physics},
      volume       = {42},
      number       = {5},
      issn         = {0094-2405},
      address      = {New York, NY},
      reportid     = {DKFZ-2017-03812},
      pages        = {2157 - 2168},
      year         = {2015},
      abstract     = {The authors investigated the potential of optimized
                      noncoplanar irradiation trajectories for volumetric
                      modulated arc therapy (VMAT) treatments of nasopharyngeal
                      patients and studied the trade-off between treatment plan
                      quality and delivery time in radiation therapy.For three
                      nasopharyngeal patients, the authors generated treatment
                      plans for nine different delivery scenarios using dedicated
                      optimization methods. They compared these scenarios
                      according to dose characteristics, number of beam
                      directions, and estimated delivery times. In particular, the
                      authors generated the following treatment plans: (1) a 4π
                      plan, which is a not sequenced, fluence optimized plan that
                      uses beam directions from approximately 1400 noncoplanar
                      directions and marks a theoretical upper limit of the
                      treatment plan quality, (2) a coplanar 2π plan with 72
                      coplanar beam directions as pendant to the noncoplanar 4π
                      plan, (3) a coplanar VMAT plan, (4) a coplanar step and
                      shoot (SnS) plan, (5) a beam angle optimized (BAO) coplanar
                      SnS IMRT plan, (6) a noncoplanar BAO SnS plan, (7) a VMAT
                      plan with rotated treatment couch, (8) a noncoplanar VMAT
                      plan with an optimized great circle around the patient, and
                      (9) a noncoplanar BAO VMAT plan with an arbitrary trajectory
                      around the patient.VMAT using optimized noncoplanar
                      irradiation trajectories reduced the mean and maximum doses
                      in organs at risk compared to coplanar VMAT plans by $19\%$
                      on average while the target coverage remains constant. A
                      coplanar BAO SnS plan was superior to coplanar SnS or VMAT;
                      however, noncoplanar plans like a noncoplanar BAO SnS plan
                      or noncoplanar VMAT yielded a better plan quality than the
                      best coplanar 2π plan. The treatment plan quality of VMAT
                      plans depended on the length of the trajectory. The delivery
                      times of noncoplanar VMAT plans were estimated to be 6.5 min
                      in average; 1.6 min longer than a coplanar plan but on
                      average 2.8 min faster than a noncoplanar SnS plan with
                      comparable treatment plan quality.The authors' study
                      reconfirms the dosimetric benefits of noncoplanar
                      irradiation of nasopharyngeal tumors. Both SnS using
                      optimized noncoplanar beam ensembles and VMAT using an
                      optimized, arbitrary, noncoplanar trajectory enabled dose
                      reductions in organs at risk compared to coplanar SnS and
                      VMAT. Using great circles or simple couch rotations to
                      implement noncoplanar VMAT, however, was not sufficient to
                      yield meaningful improvements in treatment plan quality. The
                      authors estimate that noncoplanar VMAT using arbitrary
                      optimized irradiation trajectories comes at an increased
                      delivery time compared to coplanar VMAT yet at a decreased
                      delivery time compared to noncoplanar SnS IMRT.},
      cin          = {E040},
      ddc          = {610},
      cid          = {I:(DE-He78)E040-20160331},
      pnm          = {315 - Imaging and radiooncology (POF3-315)},
      pid          = {G:(DE-HGF)POF3-315},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:25979010},
      doi          = {10.1118/1.4914863},
      url          = {https://inrepo02.dkfz.de/record/127790},
}