Room: Exhibit Hall | Forum 7
Purpose: To propose and investigate an efficient protocol of combining calibration and flatbed scanner lateral response artifact correction in a single scan for radiochromic film dosimetry.
Methods: Seven film strips were taken from one single sheet of Gafchromicâ„¢ EBT3 film. Film strips were irradiated by a 25Ã—25 cmÂ² open field at depth 5 cm with 6 different doses, together with an unexposed film strip. Three plans were chosen to validate the method: 1) simple geometry 20Ã—20 cmÂ² plan with high dose 850 cGy, 2) a clinical IMRT QA plan with a large exposed area and 3) a SBRT QA plan. The SBRT QA plan was laterally positioned on the scanner window to stress any lateral response artifact. All QA plans were generated using the RayStation TPS (RaySearch Labs). Plans were delivered by a Versa HD linear accelerator (Elekta). EBT3 films were handled per AAPM TG-55. All films were scanned by an Expression 10000XL (Epson) scanner using both transmission and reflective scanning modes. Portrait scanning positioning was adopted. The unexposed film strip and an exposed film strip were scanned along with the application films to eliminate scan-to-scan differences between the calibration scan and application scan.
Results: The method exploits each pixel value of raw projected dose map at lateral directions, aiming to provide more accurate results on lateral response artifact correction. The method was designed to handle both non-uniform open field output and film active layer non-uniform thickness through the novel sampling of calibration strips. Algorithm implementation is currently underway. Dose profiles and gamma index analysis will be used to evaluate the proposed method before and after the correction against TPS plans.
Conclusion: A novel method combines flatbed scanner calibration and correction of lateral response artifact in a single scan, proposed to improve the accuracy and efficiency of radiochromic film dosimetry.