Effects of chemical processing time on the reproducibility of film dosimetry and its optimization / 中华放射肿瘤学杂志

ABSTRACT

Objective To monitor the performance constancy of the HS-126E automatic X-ray film processor and to investigate the effects of chemical processing time on the reproducibility of film dosimetry.Methods With films having identical exposure,15 ready-pack Kodak X-omat-V films from the same batch were divided into 5 groups and exposed one by one under the identical conditions.One group of test film was processed per day from Monday to Friday with identical temperature and time.All films were digitized with a Vidar VXR-16 bit film digitizer. The average optical density(A) at irradiation field center was analyzed with RIT113 film dosimetry system software.At the same time,another 10 films in 5 groups from the same batch were exposed with vertical method and processed to get the calibration data and sensitometric curves.The film sensitivities,i.e.,ratio of A to delivered dose,were calculated and compared between groups.Another 15 films in 5 groups were exposed with horizontal method and processed similarly to the test films,the point dose at 1.5?cm depth on the central axis was calculated with sensitometric curve and compared with the value measured by ion chamber.Results Variations of A value in each group was less than 2%.During the processing period,a trend of decrease along with time in mean A value decreased day by day was observed.Both the standard deviations and coefficients of variation in all groups were within 2%.One-way ANOVA showed that there was a significant difference of the mean A value among all films from Monday to Friday(P