title: Angular distributions of absorbed dose of Bremsstrahlung and secondary electrons induced by 18-, 28- and 38-MeV electron beams in thick targets.
abstract: Angular distributions of absorbed dose of Bremsstrahlung photons and secondary electrons at a wide range of emission angles from 0 to 135°, were experimentally obtained using an ion chamber with a 0.6 cm(3) air volume covered with or without a build-up cap. The Bremsstrahlung photons and electrons were produced by 18-, 28- and 38-MeV electron beams bombarding tungsten, copper, aluminium and carbon targets. The absorbed doses were also calculated from simulated photon and electron energy spectra by multiplying simulated response functions of the ion chambers, simulated with the MCNPX code. Calculated-to-experimental (C/E) dose ratios obtained are from 0.70 to 1.57 for high-Z targets of W and Cu, from 15 to 135° and the C/E range from 0.6 to 1.4 at 0°; however, the values of C/E for low-Z targets of Al and C are from 0.5 to 1.8 from 0 to 135°. Angular distributions at the forward angles decrease with increasing angles; on the other hand, the angular distributions at the backward angles depend on the target species. The dependences of absorbed doses on electron energy and target thickness were compared between the measured and simulated results. The attenuation profiles of absorbed doses of Bremsstrahlung beams at 0, 30 and 135° were also measured.
authors: National Institute of Radiological Sciences, Chiba 263-8555, Japan. m_takada@nirs.go.jp
authors: Masashi
authors: M
authors: Takada
authors: Kazuaki
authors: K
authors: Kosako
authors: Koji
authors: K
authors: Oishi
authors: Takashi
authors: T
authors: Nakamura
authors: Kouichi
authors: K
authors: Sato
authors: Takashi
authors: T
authors: Kamiyama
authors: Yoshiaki
authors: Y
authors: Kiyanagi
mesh_terms: D000042:Absorption; D000535:Aluminum / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D003198:Computer Simulation; D003300:Copper / Q000737:chemistry; D004307:Dose-Response Relationship, Radiation; D004583:Electrons; D004867:Equipment Design; D006801:Humans; D007477:Ions; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy*; D010315:Particle Accelerators; D017785:Photons; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000295:instrumentation / Q000379:methods*; D014414:Tungsten / Q000737:chemistry
chemical_list: D007477:Ions; D002244:Carbon; D003300:Copper; D000535:Aluminum; D014414:Tungsten