Light-radiation congruence with gantry angle using the electronic portal imaging device
Keywords:
Quality assurance, x-ray/Light field congruence, electronic portal imaging device, EPIDAbstract
In the present work, a template and an own software are presented in order to perform the light-radiation congruence test in linear accelerators (LINAC) in a fast and precise way, using the electronic portal imaging device (EPID). The validation of the set template-software is carried out by means of comparison with radiographic film, an external software and displacing the collimation system. Subsequently, a study of the influence of the gantry rotation on the coincidence test in three LINACs is carried out. For the assessment of the coincidence with the gantry angle, in addition to the traditional parameters, a new parameter is proposed that evaluates the coincidence of the light and radiated areas. The variation of the coincidence with the gantry angle obtained for the three employed LINACs is not significant. The results of the study allow us to conclude that a single series of measurements (for 0º, 90º and 270º gantry) is enough to perform an evaluation of the congruence with an uncertainty of less than 1 mm. In other words, the developed set allows an evaluation of the test for several gantry angles with an assumable uncertainty.
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