Triple channel analysis of Gafchromic EBT3 irradiated with clinical carbon-ion beams. (July 2021)

• Record Type: Journal Article
• Authors: Holm, Kim Marina; Yukihara, Eduardo G.; Ahmed, Md Foiez; Greilich, Steffen; Jäkel, Oliver
• Is Part Of: Physica medica. Volume 87(2021)
• Page Start: 123
• Page End: 130
• Publication Date: 2021-07
• Subjects: Triple channel analysis -- Gafchromic EBT3 -- Carbon-ion beams; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2021.06.009
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: Good applicability of triple channel analysis for 12 C-irradiated EBT3 film specimens. Corrected film signal shows considerably improved image quality. Quantitative agreement of corrected film signal with simultaneously IC measured data. Maximum deviation in a 12 C field reduced by a factor of 3 with triple channel analysis. Possible applications of EBT3 for QA measurements in 12 C beams. Abstract: Self-developing radiochromic film is widely used in radiotherapy QA procedures. To compensate for typical film inhomogeneities, the triple channel analysis method is commonly used for photon-irradiated film. We investigated the applicability of this method for Gafchromic TM EBT3 (Ashland) film irradiated with a clinically used carbon-ion beam. Calibration curves were taken from EBT3 film specimens irradiated with monoenergetic carbon-ion beams of different doses. Measurements of the lateral field shape and homogeneity were performed in the middle of a passively modulated spread-out Bragg peak and compared to simultaneous characterization by means of a 2D ionization chamber array. Additional measurements to investigate the applicability of EBT3 for quality assurance (QA) measurement in carbon-ion beams were performed. The triple-channel analysis reduced the relative standard deviation of the doses in a uniform carbon ion field by 30% (from 1.9% to 1.3%) and reduced the maximum deviation by almost a factor of 3 (from 28.6% to 9.8%), demonstrating the elimination of film artifacts. The corrected film signal showed considerably improved image quality and quantitative agreement with the ionization chamber data, thus providing a clear rationale for the usage of the triple channel analysis in carbon-beam QA.