Comparative characterisation of different types of Gafchromic films for radiotherapy use.

Different types of Gafchromic films, for radiotherapy use, are recommended for different dose ranges. Ashland Specialty Ingredients has aimed to continuously develop its products to improve their practical application. Thus, EBT3 was replaced by EBT4, intended to provide better signal to noise ratio (SNR); while MD-V3 was introduced for use at higher dose ranges, in addition to EBT-XD. At present there are limited studies on MD-V3. This study aimed to investigate some relevant characteristics of EBT4 and MD-V3, compared with those of EBT3 and EBT-XD. The parameters investigated were dose response, optical density change with post-irradiation time, orientation effect, signal to noise ratio, polarisation, and lateral response artefact (LRA). EBT4 is similar to EBT3 however it provides better SNR and larger response change with post-irradiation time. EBT-XD and MD-V3 are recommended by the suppliers for high dose range, although the sensitivity curves show that EBT3 and EBT4 could also be used for relatively high dose ranges. All films have orientation effects, with EBT3 the worst. An important characteristic of MD-V3 is that the LRA remains similar, irrespective of delivered dose. These comparative characteristics are intended to be informative for clinical practice involving Gafchromic film use in high dose therapy applications. Recommendations from this study are to use EBT4 for dosimetry in lower-dose applications, provided that both calibration and clinical timings post-irradiation are kept similar, while MD-V3 is the preferred film for high-dose procedures.