title: Evaluation of EBT radiochromic film using a multiple exposure technique.
abstract: Radiochromic film is a self developing two-dimensional dosimeter system that is widely used in radiotherapy. Since its development some 40 years ago many improvements have been made; however the sensitivity can vary across the film and a non-linear dose response remains. The former can be addressed using a double exposure technique; however this technique assumes that the response is linear so that the dose distribution is incorrectly measured. We are proposing the use of two homogenous exposures; one performed prior, the other after the irradiation to be measured. In this 'multiple exposure technique' (MET), the first homogenous exposure can be used to correct for variations in response in different parts of the film, while the second homogenous exposure allows correction for non-linearity of response with dose. The MET was tested with a 60° wedged field and an Intensity Modulated Radiation Therapy fluence map produced by a computerised treatment planning system. In the wedge field measurements, the MET profile showed agreement within 0.6 cGy for 80% of the field compared to ionisation chamber dose values. A comparison of a TPS generated fluence map dose distribution with one measured using conventionally calibrated EBT, and another measured with MET calibrated EBT, showed similar agreement. The MET would be particularly useful for the assessment of highly inhomogenous dose distributions with high maximum dose such as encountered in hypofractionated radiation therapy.
authors: Department of Physical Sciences, Peter MacCallum Cancer Centre, Melbourne, VIC 8081, Australia. Karl.Roozen@petermac.org
authors: Karl
authors: K
authors: Roozen
authors: Tomas
authors: T
authors: Kron
authors: Annette
authors: A
authors: Haworth
authors: Rick
authors: R
authors: Franich
mesh_terms: D000465:Algorithms; D004307:Dose-Response Relationship, Radiation; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods; D016014:Linear Models; D011835:Radiation Protection / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000295:instrumentation / Q000379:methods; D014962:X-Ray Film / Q000592:standards*