Benchmarking a new radiochromic film type for photon and proton beam dosimetry

Background and Purpose: EBT4 Radiochromic films (RCFs) are replacing the well-described EBT3 type. This study aimed to benchmark the EBT4 type against its predecessor for photon (kV and MV) and proton beam dosimetry. Materials and Methods: ) on the response of both film types was compared within a proton spread-out Bragg peak (SOBP). Furthermore, the relative response in low-kV X-rays was studied and the effect of long-term storage on both film types. Results: The SNR of EBT4 films was statistically superior for MV-photon irradiations above 1.5 Gy in the red channel by up to 29 %. For low-dose proton irradiations, the SNR of EBT3 was higher. The underresponse of both film types in a proton SOBP reached 5 to 7 %. In low kV X-ray beams, EBT4 deviated from EBT3 on average by 2.5 %. For irradiations of films with a dose of 2 Gy or less after 216 days of storage, smaller differences in terms of pixel values were observed for films placed at 10°C. Conclusions: The presented results are in accordance with recent studies on EBT4 films and extend the knowledge on this film type, especially regarding proton beams and film storage.