Development of a User-Friendly Correction Method for the Lateral Response Artifact From Flatbed Scanners in Radiochromic Film Dosimetry
G Guyer*, R Kueng, A Joosten, M K Fix, P Manser, S Mueller, Division of Medical Radiation Physics and Department of Radiation Oncology, Inselspital, Bern University Hospital and University Of Bern, Bern, CH
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PO-GePV-T-184 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: In radiochromic film dosimetry, it is common practice to scan films with a flatbed scanner. A known issue affecting the accuracy is the lateral response artifact (LRA). The aim of this work is to correct the LRA with a user-friendly graphical user interface (GUI).
Methods: This work is based on a LRA correction using a one-dimensional linear correction function. This approach was enhanced by increasing the resolution of correction function. For this purpose, two sheets of film, one blank and one irradiated uniformly with 2 Gy, were used, which enables correcting films by means of a user-friendly GUI. The films were scanned in the center of the scanner and subsequently shifted laterally in both directions. After averaging the resulting values longitudinally, the correction functions were obtained. For validation, dose measurements with films inside a solid water phantom of two VMAT plans with a prescribed dose of 1 Gy and 2 Gy were performed. The irradiated films were scanned once in the center of the scanner and shifted 5 cm and 10 cm laterally in both directions. Then, the enhanced LRA correction was applied. The corrected and uncorrected dose values were evaluated in FilmQA Pro™ (Ashland) using a gamma evaluation (3% global/ 2 mm, 20% dose threshold).
Results: The gamma passing rate for the uncorrected films was above 99% for the red color channel in the center of the scanner but decreased to values between 70% and 91% and between 22% and 44% when scanned 5 cm and 10 cm away from the center, respectively. For the corrected films, the passing rates improved for all situations with the lowest passing rate being 97%.
Conclusion: An enhanced correction method for LRA with a GUI was developed, validated for VMAT plans and lead to substantially reduced LRA compared to uncorrected films.
Funding Support, Disclosures, and Conflict of Interest: This work was funded by the Swiss National Science Foundation
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TH- External Beam- Photons: Quality Assurance - IMRT/VMAT
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