title: Extraretinal induced visual sensations during IMRT of the brain.
abstract: BACKGROUND
  We observed visual sensations (VSs) in patients undergoing intensity modulated radiotherapy (IMRT) of the brain without the beam passing through ocular structures. We analyzed this phenomenon especially with regards to reproducibility, and origin.
  
  
  RESULTS
  Analyzed were ten consecutive patients (aged 41-71 years) with glioblastoma multiforme who received pulsed IMRT (total dose 60Gy) with helical tomotherapy (TT). A megavolt-CT (MVCT) was performed daily before treatment. VSs were reported and recorded using a triggered event recorder. The frequency of VSs was calculated and VSs were correlated with beam direction and couch position. Subjective patient perception was plotted on an 8x8 visual field (VF) matrix. Distance to the orbital roof (OR) from the first beam causing a VS was calculated from the Dicom radiation therapy data and MVCT data. During 175 treatment sessions (average 17.5 per patient) 5959 VSs were recorded and analyzed. VSs occurred only during the treatment session not during the MVCTs. Plotting events over time revealed patient-specific patterns. The average cranio-caudad extension of VS-inducing area was 63.4mm (range 43.24-92.1mm). The maximum distance between the first VS and the OR was 56.1mm so that direct interaction with the retina is unlikely. Data on subjective visual perception showed that VSs occurred mainly in the upper right and left quadrants of the VF. Within the visual pathways the highest probability for origin of VSs was seen in the optic chiasm and the optic tract (22%).
  
  
  CONCLUSIONS
  There is clear evidence that interaction of photon irradiation with neuronal structures distant from the eye can lead to VSs.
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Timo
authors: T
authors: Wilhelm-Buchstab
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Barbara Myrthe
authors: BM
authors: Buchstab
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Christina
authors: C
authors: Leitzen
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Stephan
authors: S
authors: Garbe
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Thomas
authors: T
authors: Müdder
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Susanne
authors: S
authors: Oberste-Beulmann
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Alois Martin
authors: AM
authors: Sprinkart
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Birgit
authors: B
authors: Simon
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Michael
authors: M
authors: Nelles
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Wolfgang
authors: W
authors: Block
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Felix
authors: F
authors: Schoroth
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Hans Heinz
authors: HH
authors: Schild
authors: University of Bonn, Department of Radiology, Radiooncology, Sigmund-Freud-Straße 25, 53105, Bonn, Deutschland, Germany.
authors: Heinrich
authors: H
authors: Schüller
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000473:pathology / Q000503:physiopathology / Q000528:radiation effects; D001932:Brain Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*; D005260:Female; D005909:Glioblastoma / Q000503:physiopathology / Q000532:radiotherapy*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012677:Sensation / Q000502:physiology / Q000528:radiation effects*; D014785:Vision, Ocular / Q000502:physiology / Q000528:radiation effects*; D014794:Visual Fields / Q000502:physiology / Q000528:radiation effects; D014795:Visual Pathways / Q000502:physiology / Q000528:radiation effects