Determination of the electronic portal imaging device pixel-sensitivity-map for quality assurance applications. Part 1: Comparison of methods.
Autor: | Barnes MP; Department of Radiation Oncology, Calvary Mater Hospital Newcastle, Newcastle, New South Wales, Australia.; School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales, Australia., Sun B; Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, USA., Oborn BM; Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, Australia.; Illawarra Cancer Care Centre, Wollongong Hospital, Wollongong, New South Wales, Australia., Lamichhane B; School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales, Australia., Szwec S; School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, Australia., Schmidt M; Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, USA., Cai B; Department of Radiation Oncology, Washington University in St. Louis, St. Louis, Missouri, USA., Menk F; School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales, Australia., Greer P; Department of Radiation Oncology, Calvary Mater Hospital Newcastle, Newcastle, New South Wales, Australia.; School of Mathematical and Physical Sciences, University of Newcastle, Newcastle, New South Wales, Australia. |
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Jazyk: | angličtina |
Zdroj: | Journal of applied clinical medical physics [J Appl Clin Med Phys] 2022 Jun; Vol. 23 (6), pp. e13603. Date of Electronic Publication: 2022 Apr 15. |
DOI: | 10.1002/acm2.13603 |
Abstrakt: | Purpose: Calibration of a radiotherapy electronic portal imaging device (EPID) using the pixel-sensitivity-map (PSM) in place of the flood field correction improves the utility of the EPID for quality assurance applications. Multiple methods are available for determining the PSM and this study provides an evaluation to inform on which is superior. Methods: Three different empirical methods ("Calvary Mater Newcastle" [CMN], "Varian," and "WashU") and a Monte Carlo-based method of PSM determination were investigated on a single Varian TrueBeam STx linear accelerator (linac) with an aS1200 EPID panel. PSM measurements were performed for each empirical method three successive times using the 6 MV beam. The resulting PSM from each method was compared to the Monte Carlo method as a reference using 2D percentage deviation maps and histograms plus crossplane profiles. The repeatability of generated PSMs was also assessed via 2D standard deviation (SD) maps and histograms. Additionally, the Beam-Response generated by removal of the PSM from a raw EPID image for each method was visually contrasted. Finally, the practicality of each method was assessed qualitatively and via the measured time required to acquire and export the required images. Results: The median pixel-by-pixel percentage deviation between each of the empirical PSM methods and the Monte Carlo PSM was -0.36%, 0.24%, and 0.74% for the CMN, Varian, and WashU methods, respectively. Ninety-five percent of pixels were found to be repeatable to within -0.21%, 0.08%, 0.19%, and 0.35% (1 SD) for the CMN, Monte Carlo, Varian, and WashU methods, respectively. The WashU method was found to be quickest for data acquisition and export and the CMN the slowest. Conclusion: For the first time four methods of generating the EPID PSM have been compared in detail and strengths and weaknesses of each method have been identified. All methods are considered likely to be clinically acceptable and with similar practical requirements. (© 2022 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, LLC on behalf of The American Association of Physicists in Medicine.) |
Databáze: | MEDLINE |
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