Utilization of Gafchromic ebt3 Films for Postal Dose Audits of 6 mv X Ray Beam Calibration of Linear Accelerator

Abstract

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.