title: Proton therapy of uveal melanomas: intercomparison of MRI-based and conventional treatment planning.
abstract: OBJECTIVE
  Proton therapy for uveal melanoma provides high-conformal dose application to the target volume and, thus, an optimal saving of the organs at risk nearby. Treatment planning is done with the model-based treatment-planning system EYEPLAN. Tumor reconstruction is based only on a fundus composite, which often leads to an overestimation of the clinical target volume (CTV). The purpose was to exploit MRI on trial in a proton therapy-planning system by using the novel image-based treatment-planning system OCTOPUS.
  
  
  METHODS
  Ten patients with uveal melanomas received both a high-resolution planning CT and MRI of the eye. MR examinations were made with an eye coil. EYEPLAN requires eye geometry data for modeling, and tantalum marker clips for submillimeter positioning and additional information from ultrasound and 3-D imaging. By contrast, OCTOPUS provides the full integration of 3-D imaging (e. g., CT, MRI). CTVs were delineated in each slice. For all patients, CTVs (EYEPLAN vs. OCTOPUS) were compared intraindividually.
  
  
  RESULTS
  OCTOPUS planning led to a mean reduction of the target volume by a factor of 1.7 (T1-weighted [T1w]) and 2.2 (T2w) without compromising safety. The corresponding field size could be scaled down on average by a factor of 1.2 (T1w) and 1.4 (T2w), respectively.
  
  
  CONCLUSIONS
  Compared with the conventional EYEPLAN, MRI-based treatment planning of ocular tumors with OCTOPUS could be a powerful tool for reducing the CTV and, consequently, the treatment volume and the field size. This might be translated into a better patient compliance during treatment and a decreased late toxicity.
authors.affiliation: Department of Radiooncology, Charité University Medicine, Berlin, Germany. simone.marnitz@charite.de
authors.forename: Simone
authors.initials: S
authors.lastname: Marnitz
authors.forename: Dino
authors.initials: D
authors.lastname: Cordini
authors.forename: Rolf
authors.initials: R
authors.lastname: Bendl
authors.forename: Arne-Jörn
authors.initials: AJ
authors.lastname: Lemke
authors.forename: Jens
authors.initials: J
authors.lastname: Heufelder
authors.forename: Ioannis
authors.initials: I
authors.lastname: Simiantonakis
authors.forename: Heinz
authors.initials: H
authors.lastname: Kluge
authors.forename: Nikolaos E
authors.initials: NE
authors.lastname: Bechrakis
authors.forename: Michael H
authors.initials: MH
authors.lastname: Foerster
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hinkelbein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008545:Melanoma / Q000532:radiotherapy*; D008875:Middle Aged; D061766:Proton Therapy; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D014604:Uveal Neoplasms / Q000532:radiotherapy*; D011522:Protons
chemical_list: D011522:Protons