SU‐F‐T‐265: Calibration of EBT2 Film Using the Microtek ScanMaker 9800XL Plus Flatbed Scanner with a Modified One Red‐Channel After Three‐Channel Method

摘要

Purpose: In this study, we propose a technique to accurately calibrate the film using the Microtek ScanMaker 9800XL plus flatbed scanner following the “one red‐channel after three‐channel method” [Chang et al., Med. Phys. 42, 5838–5847 (2015)], which would be modified for this application. Methods: Following the PDD method, 6‐MV photon beams of two different MUs were delivered to eight EBT2 films (four films for each MU), where each film was tightly sandwiched in a 30‐cm cubic polystyrene phantom and parallel to the beam central axis. Before and after irradiation, all films were scanned through the Microtek 9800XL plus scanner, and the pixel values for red, green, and blue channels were extracted along the beam central axis on the film and fitted to the corresponding depth doses. Before performing the “one red‐channel after three‐channel method”, the irradiated film image first needs to be modified with a template matrix, which was generated through the pre‐scanned background images. The calibrated results were compared with the traditional one red‐channel method based on the net optical density. Results: Without using the template matrix, the three channel method cannot be correctly performed, since the pixel values did not follow the rational fitting form. Through our proposed method, the differences between the fitted dose and the delivered dose were within 2%, while that of the traditional one red channel method would be higher than 3%. Conclusion: We proposed a new technique that the one‐red channel after three‐channel method can be applied to the films scanned on a Microtek 9800XL plus scanner, and in this way, the calibration accuracy was improved. This method could also be used for other brand scanner to improve the calibration accuracy. MOST No. 104‐2221‐E‐214‐014