title: Gafchromic EBT-XD film: Dosimetry characterization in high-dose, volumetric-modulated arc therapy.
abstract: Radiochromic films are important tools for assessing complex dose distributions. Gafchromic EBT-XD films have been designed for optimal performance in the 40-4,000 cGy dose range. We investigated the dosimetric characteristics of these films, including their dose-response, postexposure density growth, and dependence on scanner orientation, beam energy, and dose rate with applications to high-dose volumetric-modulated arc therapy (VMAT) verification. A 10 MV beam from a TrueBeam STx linear accelerator was used to irradiate the films with doses in the 0-4,000 cGy range. Postexposure coloration was analyzed at postirradiation times ranging from several minutes to 48 h. The films were also irradiated with 6 MV (dose rate (DR): 600 MU/min), 6 MV flattening filter-free (FFF) (DR: 1,400 MU/ min), and 10 MV FFF (DR: 2,400 MU/min) beams to determine the energy and dose-rate dependence. For clinical examinations, we compared the dose distribu-tion measured with EBT-XD films and calculated by the planning system for four VMAT cases. The red channel of the EBT-XD film exhibited a wider dynamic range than the green and blue channels. Scanner orientation yielded a variation of ~ 3% in the net optical density (OD). The difference between the film front and back scan orientations was negligible, with variation of ~ 1.3% in the net OD. The net OD increased sharply within the first 6 hrs after irradiation and gradually afterwards. No significant difference was observed for the beam energy and dose rate, with a variation of ~ 1.5% in the net OD. The gamma passing rates (at 3%, 3 mm) between the film- measured and treatment planning system (TPS)-calculated dose distributions under a high dose VMAT plan in the absolute dose mode were more than 98.9%.
authors.affiliation: Hiroshima High-Precision Radiotherapy Cancer Center. miura@hiprac.jp.
authors.forename: Hideharu
authors.initials: H
authors.lastname: Miura
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ozawa
authors.forename: Fumika
authors.initials: F
authors.lastname: Hosono
authors.forename: Naoki
authors.initials: N
authors.lastname: Sumida
authors.forename: Toshiya
authors.initials: T
authors.lastname: Okazue
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Yamada
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Nagata
mesh_terms: D002138:Calibration; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D009369:Neoplasms / Q000532:radiotherapy*; D010315:Particle Accelerators; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation* / Q000379:methods