utilization of gafchromic ebt3 films for postal dose audits of 6 mv x ray beam calibration of linear accelerator

Background: periodic dose quality audits of medical linear accelerators are essential to ensure proper calibration and accurate dose delivery. we aimed to assess the accuracy of 6 mv x-ray beam calibration through a postal dose audit using gafchromic ebt3 films. methods: the experiment was conducted at rsud pasar minggu hospital in jakarta, indonesia, in october 2023. a reference calibration curve for gafchromic ebt3 films was created by irradiating 3×3 cm² films at a 10 cm depth in a water phantom with a 10×10 cm² field and 100 cm source-to-surface distance, using doses 0-300 cgy with a 6 mv x-ray beam from a varian trilogy medical linear accelerator at rsud pasar minggu hospital in jakarta, indonesia. the films were scanned with a microtek tma1600-iii scanner, and optical density values were plotted against delivered doses. three unexposed films were sent to the hospital for irradiation to 2 gy in october 2023, and the returned films were analyzed by comparing their optical density values to the calibration curve. the measured dose was 1.92 gy, a -4.2% deviation from the prescribed 2 gy dose, within the ±5% tolerance. a parallel verification using optically stimulated luminescence dosimeters confirmed the gafchromic results. this study demonstrates the feasibility of using gafchromic ebt3 films for accurate, efficient calibration of linear accelerator x-ray beams in postal audits. results: the measured dose was 1.92 gy, representing a -4.2% deviation from the prescribed 2 gy dose, within the accepted ±5% tolerance. a parallel verification using optically stimulated luminescence dosimeters showed agreement with the gafchromic results. conclusion: the study confirms the feasibility of using gafchromic ebt3 films for accurate and efficient calibration of linear accelerator x-ray beams in postal audits.