title: A model for the lateral penumbra in water of a 200-MeV proton beam devoted to clinical applications.
abstract: An experimental approach for modeling the lateral penumbra of a proton beam has been investigated. Measurements were made with a silicon diode in a water tank. Several geometrical configurations (phantom position, collimator-to-surface distance, collimator diameter, bolus thickness, air gap, etc.) and beam characteristics (range, modulation, etc.) have been studied. The results show that the lateral penumbra is almost independent of the beam modulation and the diameter of the collimator. The use of scaled variables for depth and penumbra allows us to represent the increase in penumbra with depth for any configuration with a second order polynomial function, provided that the penumbra at the entrance of the medium and at the depth of the range are known.
authors.affiliation: Centre de Protonthérapie d'Orsay, France.
authors.forename: R
authors.initials: R
authors.lastname: Oozeer
authors.forename: A
authors.initials: A
authors.lastname: Mazal
authors.forename: J C
authors.initials: JC
authors.lastname: Rosenwald
authors.forename: R
authors.initials: R
authors.lastname: Belshi
authors.forename: C
authors.initials: C
authors.lastname: Nauraye
authors.forename: R
authors.initials: R
authors.lastname: Ferrand
authors.forename: S
authors.initials: S
authors.lastname: Biensan
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D006801:Humans; D008962:Models, Theoretical; D019047:Phantoms, Imaging; D061766:Proton Therapy; D011882:Radiotherapy, High-Energy / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D011522:Protons
chemical_list: D011522:Protons