[P174] Study for the amendment of sensitivity quenching in carbon-ion dose images acquired with Gafchromic films. (August 2018)

• Record Type: Journal Article
• Authors: Gambarini, Grazia; Barzon, Giorgio; Bettega, Daniela; Bettinelli, Lorenzo; Camoni, Gabriele; Carrara, Mauro; Mirandola, Alfredo; Ciocca, Mario
• Is Part Of: Physica medica. Volume 52(2018)Supplement 1
• Page Start: 149
• Page End: 150
• Publication Date: 2018-08
• Subjects: Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2018.06.474
• Languages: English
• ISSNs: 1120-1797

Abstract

Abstract : Purpose: Gafchromic films could be valid detectors for in-phantom dose controls in hadrontherapy but the quenching of their sensitivity with increasing the linear energy transfer (LET) of radiation brings a limit to their utilisation. This effect is manifest in the case of exposures to protons but it is really noticeable for carbon ions, whose LET is high also at the beam-entrance position. A method for correcting dose images acquired with films irradiated with proton beams has been initially proposed and tested with high approximations[1] and then developed with more exhaustive procedure[2] . In this work, studies aimed at applying the method, in his final structure, to carbon ions are carried out. Methods: Gafchromic EBT3 films that were suitably placed in a solid-water phantom and exposed to carbon ion beams at the synchrotron of CNAO (Pavia, Italy). Optical analyses were performed with conventional scanner or laboratory-made instrument for light-transmittance detection. The method for amending dose images evaluates, in each image point, a correction coefficient obtained evaluating, for each pencil beam (PB) giving dose contribution in the considered position, both the absorbed dose and the measured one and, finally, their ratio. Dedicated software in MATLAB has been developed for attaining the corrected images. Results: Correction algorithms require 3D knowledge of both absorbed and measured doses for each PB. Measurements and calculations have been performed with PBs of various energies and fitting parameters were deduced. Conclusions: The proposed method for amending the experimental images has proved to be promising and, upon completion of the software, will be suitable for the use in clinical practice.