Role of “the frame cycle time” in portal dose imaging using an aS500-II EPID |
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| Authors: | Zeina Al Kattar Elbalaa Jean Noel Foulquier Alexandre Orthuon Hanna Elbalaa Emmanuel Touboul |
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| Institution: | 1. JNTU College of Engineering, Anantapur, Andhara Pradesh, India;2. School of Energy Science & Engineering, Indian Institute of Technology Kharagpur, West Bengal 721302, India;3. Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, West Bengal 721302, India;4. Fuels and Combustion Engines Lab, Energy Resources Engineering Department – Egypt-Japan University of Science and Technology (E-JUST), Egypt;5. Mechanical Engineering Department, Faculty of Engineering, Alexandria University, Alexandria 21544, Egypt;1. Department of Physics, Bharathiar University, Coimbatore, India;2. Department of Medical Physics, Bharathiar University, Coimbatore, India;1. Department of Social and Administrative Pharmacy, School of Pharmacy, Jimma University, Jimma, Oromia, Ethiopia;2. Gembella Regional Health Bureau, Gambella, Ethiopia;3. Department of Social Pharmacy and Pharmaceutics, School of Pharmacy, College of Medicine and Health Sciences, Mizan-Tepi University, Mizan-Aman, Ethiopia |
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| Abstract: | IntroductionThis paper evaluates the role of an acquisition parameter, the frame cycle time “FCT”, in the performance of an aS500-II EPID.Materials and methodsThe work presented rests on the study of the Varian EPID aS500-II and the image acquisition system 3 (IAS3). We are interested in integrated acquisition using asynchronous mode. For better understanding the image acquisition operation, we investigated the influence of the “frame cycle time” on the speed of acquisition, the pixel value of the averaged gray-scale frame and the noise, using 6 and 15 MV X-ray beams and dose rates of 1–6 Gy/min on 2100 C/D Linacs.ResultsIn the integrated mode not synchronized to beam pulses, only one parameter the frame cycle time “FCT” influences the pixel value. The pixel value of the averaged gray-scale frame is proportional to this parameter. When the FCT <55 ms (speed of acquisition Vf/s > 18 frames/s), the speed of acquisition becomes unstable and leads to a fluctuation of the portal dose response. A timing instability and saturation are detected when the dose per frame exceeds 1.53 MU/frame. Rules were deduced to avoid saturation and to optimize this dosimetric mode.ConclusionThe choice of the acquisition parameter is essential for the accurate portal dose imaging. |
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