title: [Report on the 13th European Congress of Radiology (ECR): Comparison of primary proton beams and secondary charged-particles].
abstract: OBJECTIVE
  In the proton radiotherapy, primary proton beams contribute to the absorbed dose and the share of secondary charged-particles is small. The purpose is to discuss about the ratio of average dose of primary proton beams and secondary charged-particles.
  
  
  METHODS
  We performed the dosimetry of 70 MeV proton beams in water using ionization chamber. The ratio of average dose for secondary charged-particles in some range shifter was calculated by the dose ratio of primary and scatter. To exclude the influence of lateral secondary charged-particles, the ratio of average dose for secondary charged-particles was extrapolated to zero field size of each.
  
  
  RESULTS
  The ratio of average dose for secondary charged-particles was extrapolated to zero field size by the bi-exponential fit. The ratio of average dose for longitudinal secondary charged-particles for zero fields at each depth is almost the same; the different at the shallow depth is decreased.
  
  
  CONCLUSIONS
  The secondary charged-particles from collimator is affected by the dose of shallow depth. The influence of lateral secondary charged-particles in water phantom was excluded with the extrapolation method for zero field size in each depth.
authors.affiliation: Tokyo Metropolitan University of Health Sciences.
authors.forename: H
authors.initials: H
authors.lastname: Ohtani
authors.forename: T
authors.initials: T
authors.lastname: Irifune
authors.forename: T
authors.initials: T
authors.lastname: Hiraoka
authors.forename: K
authors.initials: K
authors.lastname: Satoh
authors.forename: S
authors.initials: S
authors.lastname: Urahashi
mesh_terms: D000512:Alpha Particles; D006801:Humans; D019047:Phantoms, Imaging; D011522:Protons; D011874:Radiometry; D011879:Radiotherapy Dosage; D014867:Water
chemical_list: D011522:Protons; D014867:Water