title: Clinical results of an EPID-based in-vivo dosimetry method for pelvic cancers treated by intensity-modulated radiation therapy.
abstract: The purpose of our work was to investigate the feasibility of using an EPID-based in-vivo dosimetry method initially designed for conformal fields on pelvic dynamic IMRT fields. The method enables a point dose delivered to the patient to be calculated from the transit signal acquired with an electronic portal imaging device (EPID). After defining a set of correction factors allowing EPID pixel values to be converted into absolute doses, several tests on homogeneous water-equivalent phantoms were performed to estimate the validity of the method in reference conditions. The effects of different treatment parameters, such as delivered dose, field size dependence and patient thickness were also studied. The model was first evaluated on a group of 53 patients treated by 3D conformal radiotherapy (3DCRT) and then on 92 patients treated by IMRT, both for pelvic cancers. For each measurement, the dose was reconstructed at the isocenter (DREC) and compared with the dose calculated by our treatment planning system (DTPS). Excellent agreement was found between DREC and DTPS for both techniques. For 3DCRT treatments, the mean deviation between DREC and DTPS for the 211 in-vivo dose verifications was equal to -1.0  ±  2.2% (1SD). Concerning IMRT treatments, the averaged deviation for the 418 fields verified was equal to -0.3 ± 2.6% (1SD) proving that the method is able to reconstruct a dose for dynamic IMRT pelvic fields. Based on these results, tolerance criteria and action levels were established before its implementation in clinical routine.
authors.affiliation: INSERM, Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Service de radiothérapie, groupe Oncorad-Garonne, Clinique Pasteur, L'Atrium, 1, rue de la petite-vitesse, 31000 Toulouse, France. Electronic address: Camilleri.jeremy@gmail.com.
authors.forename: J
authors.initials: J
authors.lastname: Camilleri
authors.affiliation: Service de radiothérapie, groupe Oncorad-Garonne, Clinique Pasteur, L'Atrium, 1, rue de la petite-vitesse, 31000 Toulouse, France.
authors.forename: J
authors.initials: J
authors.lastname: Mazurier
authors.affiliation: Service de radiothérapie, groupe Oncorad-Garonne, Clinique Pasteur, L'Atrium, 1, rue de la petite-vitesse, 31000 Toulouse, France.
authors.forename: D
authors.initials: D
authors.lastname: Franck
authors.affiliation: Service d'oncologie, groupe Oncorad-Garonne, Clinique du Pont-de-Chaume, 330, avenue Marcel-Unal, 82000 Montauban, France.
authors.forename: P
authors.initials: P
authors.lastname: Dudouet
authors.affiliation: Service de radiothérapie, groupe Oncorad-Garonne, Clinique Pasteur, L'Atrium, 1, rue de la petite-vitesse, 31000 Toulouse, France.
authors.forename: I
authors.initials: I
authors.lastname: Latorzeff
authors.affiliation: INSERM, Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France; Université de Toulouse, UPS, INPT, LAPLACE Laboratoire Plasma et Conversion d'Energie, 118 route de Narbonne, F-31062 Toulouse Cedex 9, France; Université de Toulouse, UPS, Imagerie cérébrale et handicaps neurologiques, UMR 825, F-31059 Toulouse, France.
authors.forename: X
authors.initials: X
authors.lastname: Franceries
mesh_terms: D055615:Electrical Equipment and Supplies; D005240:Feasibility Studies; D006801:Humans; D010386:Pelvic Neoplasms / Q000532:radiotherapy*; D019047:Phantoms, Imaging; D011874:Radiometry / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated
keywords: Electronic portal imaging device; IMRT quality assurance; In-vivo transit dosimetry