Background: In radiotherapy treatments, it is crucial to monitor the performance of linac components including gantry, collimation system, and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method is suggested in conjunction with an algorithm to investigate the stability of these systems at various gantry angles with the aim of evaluating machine-related errors in treatments. Methods: The EPID sag, gantry sag, changes in source-to-detector distance (SDD), EPID and collimator skewness, EPID tilt, and the sag in leaf bank assembly due to linac rotation were separately investigated by acquisition of 37 EPID images of a simple phantom with five ball bearings at various gantry angles. A fast and robust software package was developed for automated analysis of image data. Three Siemens linacs were investigated. Results: The average EPID sag was within 1 mm for all tested linacs. Two machines showed > 1 mm gantry sag. Changes in the SDD values were within 7.5 mm. EPID skewness and tilt values were < 1° in all machines. The maximum sag in leaf bank assembly was < 1 mm. Conclusion: The method and software developed in this study provide a simple tool for effective investigation of the behavior of Siemens linac components with gantry rotation. Such a comprehensive study has been performed for the first time on Siemens machines.
CITATION STYLE
Rowshanfarzad, P., Häring, P., Riis, H. L., Zimmermann, S. J., & Ebert, M. A. (2015). Investigation of the mechanical performance of Siemens linacs components during arc: Gantry, MLC, and electronic portal imaging device. Medical Devices: Evidence and Research, 8, 457–466. https://doi.org/10.2147/MDER.S89725
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