Simultaneous determination of the dose and linear energy transfer (LET) of carbon-ion beams using radiochromic films.

Radiochromic films are useful as dosimeters in high-precision radiotherapy owing to their high spatial resolution. However, when a particle beam is measured using a radiochromic film, the dose cannot be estimated accurately because the film darkness varies with variations in linear energy transfer (LET). This paper proposes a novel method for estimating the LET and the dose based on the film darkness. In this method, after a high-LET particle beam, such as a carbon-ion beam, was incident on the film, the film was digitized and its net optical density was determined. Further, the non-linearity of the film response curve between the dose and the darkness, depending on LET, was used. Then, calibration curves were created using 290 MeV u