Evaluation of MLC performance in VMAT and dynamic IMRT by log file analysis |
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| Institution: | 1. Medical Physics Department, OSI Araba, Hospital Universitario Araba, Cl. Jose Atxotegi s/n, Vitoria-Gasteiz, Araba, Spain;2. Medical Physics Department, Centro de Investigación Biomédica de La Rioja, Cl. Piqueras 98, Logroño, La Rioja, Spain;3. Medical Physics Department, Complejo Hospitalario de Navarra, Cl. Irunlarrea 3, Pamplona, Navarra, Spain;4. Medical Physics Department, Hospital Universitario de Cruces, Plz. Cruces, Barakaldo, Vizcaya, Spain;1. Department of Radiation Oncology, University of Groningen, University Medical Center Groningen, Netherlands;2. OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Germany;3. INFN Rome, Italy;4. University of Cambridge, UK;5. MGH, USA;6. HollandPTC, Delft, Netherlands;7. Hokkaido University, Japan;8. University Medical Center Hamburg-Eppendorf, Germany;9. ETH, Zuerich, Switzerland;10. Paul Scherrer Institut (PSI), Villigen, Switzerland;11. The Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, London, UK;12. Strahlenklinik, Universitätsklinikum Erlangen, Germany;13. Lyon 1 University and CNRS/IN2P3, UMR 5822, 69622 Villeurbanne, France;14. Centre for Medical Image Computing, Dept. Medical Physics and Bioengineering, University College London, London, UK;1. Department of Oncology, Section of Radiotherapy, Rigshospitalet, Copenhagen, Denmark;2. Niels Bohr Institute, Faculty of Science, University of Copenhagen, Denmark;3. Paul Scherrer Institute, 5232 Villigen PSI, Switzerland;4. Faculty of Medical Sciences, University of Copenhagen, Denmark;1. Department of Medical Physics, Tom Baker Cancer Centre, 1331 29 Street NW, Calgary, AB T2N 4N2, Canada;2. Department of Physics & Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada;3. Department of Oncology, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada;1. Department of Radiology, Takeda General Hospital, Aizuwakamatsu, Japan;2. Department of Radiation Oncology, Tohoku University Graduate School of Medicine, Sendai, Japan;3. Department of Radiation Oncology, Tokai University Graduate School of Medicine, Isehara, Japan;4. Department of Radiological Technology, Tohoku University Graduate School of Medicine, Sendai, Japan |
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| Abstract: | PurposeThis multi-institution study assessed the positioning accuracy of multileaf collimators (MLC) by analyzing log files. It determined the main machine parameters that affect MLC positioning errors for pre-TrueBeam (Clinac) and TrueBeam linacs.MethodsAround 30,000 dIMRT and VMAT log files belonging to 6 linacs from 4 different centers were analyzed. An in-house software was used to calculate 95th percentile and RMS error values and their correlation with certain parameters such as maximum leaf speed, mean leaf speed and gantry angle. The effect of MLC communication delay on error statistics was assessed in Clinac linacs. To that end MLC positioning error statistics were calculated with and without the delay effect.ResultsFor dIMRT treatments in Clinac linacs the mean leaf RMS error was 0.306 mm with and 0.030 mm without the delay effect. Leaf RMS error was closely linked to maximum and mean leaf speeds, but without the delay effect that link was weaker. No trend was observed between bank RMS error and gantry angle. Without the delay effect larger bank RMS errors were obtained for gantry angles with leaf movements against gravity. For VMAT treatments in TrueBeam linacs the mean leaf RMS error was 0.038 mm. A link was also observed between leaf RMS error and maximum and mean leaf speeds.ConclusionTrueBeam MLC positioning errors are substantially lower than those of Clinac linacs. In Clinac machines the analysis of dynalogs without the delay effect allows us to study the influence of factors that are masked by the delay effect. |
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| Keywords: | Trajectory log file Dynalog IMRT VMAT |
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