Suitability of radiochromic films for dosimetry of low energy X‐rays

This study examined the response characteristics of three commercially available radiochromic films when exposed to low energy (50 kVp) X‐rays. The aim was to evaluate the films for potential use in 2D dosimetry for a low‐kV intraoperative radiotherapy (IORT) device known as the ‘Intrabeam’. Dose‐response relationships were obtained for Gafchromic EBT, XR‐RV2, and XR‐QA film in water at several distances from the Intrabeam device. It was found that the dose rates from the source were excessive for use of the XR‐QA film, and that all three film types showed significant energy dependence within the limits of measurement uncertainty. Basic modeling of primary X‐ray spectra indicated large changes in the lower energy components with distance from the source, and it is hypothesized that the changes in film response are a result of changes in film energy response. This is in contrast to previous studies indicating less or negligible energy response. All films showed non‐linearity in response over the ranges examined. These results imply significant limitations for the use of these films for low‐kV dosimetry. PACS number: 87.53.Bn