title: Proton beam dosimetry: a comparison between a plastic scintillator, ionization chamber and Faraday cup.
abstract: In this study, a comparison was made between a plastic scintillator (BC400), a Faraday Cup (FC) and an ionization chamber (IC) used for routine proton dosimetry. Thin scintillators can be applied to proton dosimetry and consequently to proton therapy as relative dosimeters because of their water-equivalent nature, high energy-light conversion efficiency, low dimensions and good proportionality to the absorbed dose at low stopping powers. To employ such scintillators as relative dosimeters in proton therapy, the corrective factors must be applied to correct the quenching luminescence at the Bragg peak. A fine linear proportionality between the luminescence light yield Y and the proton flux in a thin (0.5 mm) scintillator for the 20 and 30 MeV proton beams were observed. The experimental peak/plateau ratios of Bragg Curve for 2, 1 and 0.5 mm scintillators with an accuracy of 0.5% were obtained to be 1.87, 1.91 and 2.30, respectively. With combination of the Markus chamber and the CR-39 detector, the peak/plateau ratio was improved to 3.26. The obtained data of the luminescence yield as a function of the specific energy loss is in agreement with the Craun-Birk's theory. Results show that the FC and Markus ionization chamber are in agreement within 4%, while the FC gives a lower dose evaluation. For a defined beam, the data for the fluence measurements are reproducible within a good accuracy.
authors.affiliation: Department of Nuclear Engineering & Physics, Amirkabir University of Technology, Tehran, Iran.
authors.forename: Mitra
authors.initials: M
authors.lastname: Ghergherehchi
authors.forename: Hossein
authors.initials: H
authors.lastname: Afarideh
authors.forename: Mohammad
authors.initials: M
authors.lastname: Ghannadi
authors.forename: Ahmad
authors.initials: A
authors.lastname: Mohammadzadeh
authors.forename: Golam Reza
authors.initials: GR
authors.lastname: Aslani
authors.forename: Behzad
authors.initials: B
authors.lastname: Boghrati
mesh_terms: D055592:Biophysical Phenomena; D003198:Computer Simulation; D006801:Humans; D008962:Models, Theoretical; D010969:Plastics; D061766:Proton Therapy; D011874:Radiometry / Q000295:instrumentation* / Q000706:statistics & numerical data; D011882:Radiotherapy, High-Energy; D012588:Scintillation Counting / Q000295:instrumentation / Q000706:statistics & numerical data; D012984:Software
chemical_list: D010969:Plastics