title: 3D VMAT Verification Based on Monte Carlo Log File Simulation with Experimental Feedback from Film Dosimetry.
abstract: A model based on a specific phantom, called QuAArC, has been designed for the evaluation of planning and verification systems of complex radiotherapy treatments, such as volumetric modulated arc therapy (VMAT). This model uses the high accuracy provided by the Monte Carlo (MC) simulation of log files and allows the experimental feedback from the high spatial resolution of films hosted in QuAArC. This cylindrical phantom was specifically designed to host films rolled at different radial distances able to take into account the entrance fluence and the 3D dose distribution. Ionization chamber measurements are also included in the feedback process for absolute dose considerations. In this way, automated MC simulation of treatment log files is implemented to calculate the actual delivery geometries, while the monitor units are experimentally adjusted to reconstruct the dose-volume histogram (DVH) on the patient CT. Prostate and head and neck clinical cases, previously planned with Monaco and Pinnacle treatment planning systems and verified with two different commercial systems (Delta4 and COMPASS), were selected in order to test operational feasibility of the proposed model. The proper operation of the feedback procedure was proved through the achieved high agreement between reconstructed dose distributions and the film measurements (global gamma passing rates > 90% for the 2%/2 mm criteria). The necessary discretization level of the log file for dose calculation and the potential mismatching between calculated control points and detection grid in the verification process were discussed. Besides the effect of dose calculation accuracy of the analytic algorithm implemented in treatment planning systems for a dynamic technique, it was discussed the importance of the detection density level and its location in VMAT specific phantom to obtain a more reliable DVH in the patient CT. The proposed model also showed enough robustness and efficiency to be considered as a pre-treatment VMAT verification system.
authors.affiliation: Dpto. Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain.|Instituto de Biomedicina de Sevilla, IBIS, Sevilla, Spain.
authors.forename: A R
authors.initials: AR
authors.lastname: Barbeiro
authors.affiliation: Dpto. Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain.|Instituto de Biomedicina de Sevilla, IBIS, Sevilla, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Ureba
authors.affiliation: Dpto. Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain.
authors.forename: J A
authors.initials: JA
authors.lastname: Baeza
authors.affiliation: Servicio de Radiofísica, Hospital Infanta Luisa, Seville, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Linares
authors.affiliation: Servicio de Radiofísica, Hospital Infanta Luisa, Seville, Spain.|Instituto de Biomedicina de Sevilla, IBIS, Sevilla, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Perucha
authors.affiliation: Dpto. Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain.|Instituto de Biomedicina de Sevilla, IBIS, Sevilla, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Jiménez-Ortega
authors.affiliation: Servicio de Radiofísica, Hospital Virgen del Rocío, Seville, Spain.|Instituto de Biomedicina de Sevilla, IBIS, Sevilla, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Velázquez
authors.affiliation: Dpto. Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain.|Servicio de Radiofísica, Hospital Virgen del Rocío, Seville, Spain.
authors.forename: J C
authors.initials: JC
authors.lastname: Mateos
authors.affiliation: Dpto. Fisiología Médica y Biofísica, Universidad de Sevilla, Seville, Spain.|Instituto de Biomedicina de Sevilla, IBIS, Sevilla, Spain.
authors.forename: A
authors.identifier: http://orcid.org/0000-0002-0687-5305
authors.initials: A
authors.lastname: Leal
mesh_terms: D003198:Computer Simulation; D005246:Feedback; D005373:Film Dosimetry / Q000379:methods*; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation*