There is an increased cancer risk when using computed tomography (CT) in pediatric patients. Thus, it is necessary to know precisely the X-rays doses used during CT examinations. Radiochromic film is the most suitable for performing these measurements, although thickness irregularities in the active layer remain a problem. In this study, we estimated ultraviolet (UV)-rays exposure using a double-exposure technique to compensate for nonuniformity errors. To identify any irregularities in density in the radiochromic film active layer, we exposed a radiochromic film to contraindicated UV-rays doses. Then, we compared profile curves for first and second UV-rays exposure images and a subtraction image from the radiochromic film. From this information, we analyzed the extent of removal of thickness irregularities in the active layer.Pixel levels for the standard deviations and the differences between the maximum and minimum values of the subtraction image were used as an index of active layer unevenness and were highly reduced compared with those of a pre-subtraction image.Using this method, it is possible to precisely and readily measure X-raysdoses, such as those used for CT examinations.