On energy dependency, spectral properties, and orientation dependency of EBT3, EBT-XD, MD-V3, and HD-V2 radiochromic films

<i>Objective</i>. Radiochromic films (RCFs) are indispensable dosimeters for two-dimensional and small field dosimetry. Different models of RCFs with associated dynamic ranges are commercially available to support various dosimetry needs. Here, we study energy dependency, absorption spectra, and orientation dependency of EBT3, EBT-XD, MD-V3, and HD-V2 RCFs.<i>Approach</i>. RCF pieces were irradiated at various dose levels, depending on their dynamic range, using a 6 MV photon beam and a 220 kVp x-ray beam. Films were scanned using a flatbed scanner to obtain the optical density at red, green, and blue color channels. A visible spectrometer was used to measure the absorption spectra of the films. A subset of RCF pieces were scanned at various orientation to investigate the orientation dependency.<i>Main results</i>. In all four models an under-response to the kV beam was observed compared to the MV beam. A noticeable dose-dependent shift in the peak absorption spectrum was noted in MD-V3 and HD-V2 films. An orientation dependency was noted in all models which can be modeled by assuming a polarization axis in the films.<i>Significance</i>. The presented work provides valuable information on the characteristics of different models of RCF.