title: Dose-response of EBT3 radiochromic films to proton and carbon ion clinical beams.
abstract: We investigated the dose-response of the external beam therapy 3 (EBT3) films for proton and carbon ion clinical beams, in comparison with conventional radiotherapy beams; we also measured the film response along the energy deposition-curve in water. We performed measurements at three hadrontherapy centres by delivering monoenergetic pencil beams (protons: 63-230 MeV; carbon ions: 115-400 MeV/u), at 0.4-20 Gy dose to water, in the plateau of the depth-dose curve. We also irradiated the films to clinical MV-photon and electron beams. We placed the EBT3 films in water along the whole depth-dose curve for 148.8 MeV protons and 398.9 MeV/u carbon ions, in comparison with measurements provided by a plane-parallel ionization chamber. For protons, the response of EBT3 in the plateau of the depth-dose curve is not different from that of photons, within experimental uncertainties. For carbon ions, we observed an energy dependent under-response of EBT3 film, from 16% to 29% with respect to photon beams. Moreover, we observed an under-response in the Bragg peak region of about 10% for 148.8 MeV protons and of about 42% for 398.9 MeV/u carbon ions. For proton and carbon ion clinical beams, an under-response occurs at the Bragg peak. For carbon ions, we also observed an under-response of the EBT3 in the plateau of the depth-dose curve. This effect is the highest at the lowest initial energy of the clinical beams, a phenomenon related to the corresponding higher LET in the film sensitive layer. This behavior should be properly modeled when using EBT3 films for accurate 3D dosimetry.
authors.affiliation: Dipartimento di Fisica 'Ettore Pancini', Università di Napoli Federico II, and INFN Sezione di Napoli, Napoli, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Castriconi
authors.forename: Mario
authors.initials: M
authors.lastname: Ciocca
authors.forename: Alfredo
authors.initials: A
authors.lastname: Mirandola
authors.forename: Carla
authors.initials: C
authors.lastname: Sini
authors.forename: Sara
authors.initials: S
authors.lastname: Broggi
authors.forename: Marco
authors.initials: M
authors.lastname: Schwarz
authors.forename: Francesco
authors.initials: F
authors.lastname: Fracchiolla
authors.forename: Mária
authors.initials: M
authors.lastname: Martišíková
authors.forename: Giulia
authors.initials: G
authors.lastname: Aricò
authors.forename: Giovanni
authors.initials: G
authors.lastname: Mettivier
authors.forename: Paolo
authors.initials: P
authors.lastname: Russo
mesh_terms: D002138:Calibration; D002244:Carbon / Q000627:therapeutic use*; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D061766:Proton Therapy; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods; D035501:Uncertainty; D014867:Water
chemical_list: D014867:Water; D002244:Carbon