title: Evaluation of Gafchromic EBT-XD film, with comparison to EBT3 film, and application in high dose radiotherapy verification.
abstract: There is renewed interest in film dosimetry for the verification of dose delivery of complex treatments, particularly small fields, compared to treatment planning system calculations. A new radiochromic film, Gafchromic EBT-XD, is available for high-dose treatment verification and we present the first published evaluation of its use. We evaluate the new film for MV photon dosimetry, including calibration curves, performance with single- and triple-channel dosimetry, and comparison to existing EBT3 film. In the verification of a typical 25 Gy stereotactic radiotherapy (SRS) treatment, compared to TPS planned dose distribution, excellent agreement was seen with EBT-XD using triple-channel dosimetry, in isodose overlay, maximum 1.0 mm difference over 200-2400 cGy, and gamma evaluation, mean passing rate 97% at 3% locally-normalised, 1.5 mm criteria. In comparison to EBT3, EBT-XD gave improved evaluation results for the SRS-plan, had improved calibration curve gradients at high doses, and had reduced lateral scanner effect. The dimensions of the two films are identical. The optical density of EBT-XD is lower than EBT3 for the same dose. The effective atomic number for both may be considered water-equivalent in MV radiotherapy. We have validated the use of EBT-XD for high-dose, small-field radiotherapy, for routine QC and a forthcoming multi-centre SRS dosimetry intercomparison.
authors.affiliation: Department of Physics, Faculty of Engineering and Physical Science, University of Surrey, GU2 7JP, UK. Medical Physics Department, F-Level, Queen Alexandra Hospital, Portsmouth Hospitals NHS Trust, Portsmouth, PO6 3LY, UK.
authors.forename: Antony L
authors.initials: AL
authors.lastname: Palmer
authors.forename: Alexis
authors.initials: A
authors.lastname: Dimitriadis
authors.forename: Andrew
authors.initials: A
authors.lastname: Nisbet
authors.forename: Catharine H
authors.initials: CH
authors.lastname: Clark
mesh_terms: D002138:Calibration; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D009369:Neoplasms / Q000601:surgery*; D017785:Photons; D011829:Radiation Dosage; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D015203:Reproducibility of Results