Source and detector polarization effects on radiographic film dosimetry

Kodak X-Omat V radiographic film has been tested for its polarization properties when using polarized and non-polarized light sources and detectors. The radiographic film has been shown to produce a relatively small but not negligible (less than 5%) variation in 90 degrees cycles in measured optical density within the visible spectrum when the light source is fully linear polarized and the film is rotated through 360 degrees angle. Negligible variations are seen when the detector is linearly polarized. If both light source and detector are linearly polarized, variations in measured optical density can reach 35% when the film is rotated through 360 degrees angle. This seems to be due to variations in the degree and axis of rotation in polarized light caused by the radiographic film and is independent of exposure level as the intensity of variation in absolute optical density is relatively the same for all film exposures. We recommend that a polarization test be performed on a densitometry system to establish the extent of its polarization properties before accurate dosimetry is performed with radiographic film.