How does film dosimetry work?
We use GafchromicTM EBT3 films from Ashland which is specifically designed for applications in radiotherapy. This film features symmetrical construction and anti-Newton ring coatings for enhanced ease-of-use and accuracy. Film dosimetry offers superior resolution and is a natural 2D dosimeter compared to detectors used for point measurements (e.g. ionisation chamber). The benefits of film dosimetry are:
- Dynamic dose range: 0.1 Gy to 20 Gy
- Optimum dose range: 0.2 Gy to 10 Gy, best suited for applications such as IMRT and VMAT
- Develops in real time without post-exposure treatment
- Energy-dependence: minimal response difference from 100keV into the MV range
- Near tissue equivalent
- High spatial resolution – can resolve features down to 25μm, or less
- Stable at temperatures up to 60°C
Irradiation causes darkening of the film, the degree of which depends on the amount of radiation dose. The evaluation of the films is commonly expressed in terms of Optical Density (OD) change, which can be measured by a flatbed scanner.
We use an Epson® 10000XL scanner in combination with the FilmQA software to analyse the films.