title: Technical considerations for noncoplanar proton-beam therapy of patients with tumors proximal to the optic nerve.
abstract: OBJECTIVE
  To investigate technical feasibilities of noncoplanar proton-beam therapy (PBT) on dose reduction to critical organs.
  
  
  METHODS
  The degree of mechanical precision, rotational limitations of the gantry and the treatment couch were evaluated, and dose-volume histograms were compared for noncoplanar and coplanar PBT. Following these studies, three patients with tumors proximal to the optic nerve underwent noncoplanar PBT.
  
  
  RESULTS
  Noncoplanar PBT offered advantage in dose reduction to the optic nerve when compared to coplanar therapy. This advantage was more significant if the tumor reduced in size during treatment. None experienced radiation injury to the optic nerve during a short follow-up time of 7-12 months.
  
  
  CONCLUSIONS
  Noncoplanar PBT appears to reduce doses to organs at risk.
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan. mizumoto1717@hotmail.com.|Proton Medical Research Center, University of Tsukuba, Tennoudai, Tsukuba, Ibaraki, 305-8575, Japan. mizumoto1717@hotmail.com.
authors.forename: Masashi
authors.initials: M
authors.lastname: Mizumoto
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan.
authors.forename: Hidetsugu
authors.initials: H
authors.lastname: Nakayama
authors.affiliation: Alpert Medical School of Brown University, Providence, RI, USA.
authors.forename: Mari
authors.initials: M
authors.lastname: Tokita
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Sugahara
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan.
authors.forename: Haruko
authors.initials: H
authors.lastname: Hashii
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan.
authors.forename: Takeji
authors.initials: T
authors.lastname: Sakae
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Tsuboi
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Sakurai
authors.affiliation: Proton Medical Research Center, University of Tsukuba, Ibaraki, Japan.|Department of Radiology, Tokyo Medical University, Tokyo, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Tokuuye
mesh_terms: D008949:Adenoma, Pleomorphic / Q000532:radiotherapy*; D001932:Brain Neoplasms / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D005142:Eyelid Neoplasms / Q000532:radiotherapy*; D005260:Female; D005625:Frontal Lobe / Q000528:radiation effects*; D005909:Glioblastoma / Q000532:radiotherapy*; D006801:Humans; D008577:Meningeal Neoplasms / Q000532:radiotherapy*; D008579:Meningioma / Q000532:radiotherapy*; D008875:Middle Aged; D009897:Optic Chiasm / Q000528:radiation effects; D009900:Optic Nerve / Q000528:radiation effects*; D010315:Particle Accelerators; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012160:Retina / Q000528:radiation effects; D017356:Synchrotrons; D011522:Protons
chemical_list: D011522:Protons