title: Luminescence imaging of water during proton-beam irradiation for range estimation.
abstract: OBJECTIVE
  Proton therapy has the ability to selectively deliver a dose to the target tumor, so the dose distribution should be accurately measured by a precise and efficient method. The authors found that luminescence was emitted from water during proton irradiation and conjectured that this phenomenon could be used for estimating the dose distribution.
  
  
  METHODS
  To achieve more accurate dose distribution, the authors set water phantoms on a table with a spot scanning proton therapy system and measured the luminescence images of these phantoms with a high-sensitivity, cooled charge coupled device camera during proton-beam irradiation. The authors imaged the phantoms of pure water, fluorescein solution, and an acrylic block.
  
  
  RESULTS
  The luminescence images of water phantoms taken during proton-beam irradiation showed clear Bragg peaks, and the measured proton ranges from the images were almost the same as those obtained with an ionization chamber. Furthermore, the image of the pure-water phantom showed almost the same distribution as the tap-water phantom, indicating that the luminescence image was not related to impurities in the water. The luminescence image of the fluorescein solution had ∼3 times higher intensity than water, with the same proton range as that of water. The luminescence image of the acrylic phantom had a 14.5% shorter proton range than that of water; the proton range in the acrylic phantom generally matched the calculated value. The luminescence images of the tap-water phantom during proton irradiation could be obtained in less than 2 s.
  
  
  CONCLUSIONS
  Luminescence imaging during proton-beam irradiation is promising as an effective method for range estimation in proton therapy.
authors.affiliation: Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya 461-8673, Japan.
authors.forename: Seiichi
authors.initials: S
authors.lastname: Yamamoto
authors.affiliation: Department of Proton Therapy Physics, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya 462-8508, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Toshito
authors.affiliation: Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya 461-8673, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Okumura
authors.affiliation: Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya 461-8673, Japan.
authors.forename: Masataka
authors.initials: M
authors.lastname: Komori
mesh_terms: D008027:Light; D008163:Luminescent Measurements / Q000379:methods*; D061766:Proton Therapy / Q000379:methods*; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D013819:Thermoluminescent Dosimetry / Q000379:methods*; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water