BackgroundIn modern radiotherapy, it is crucial to monitor the performance of all linac components including gantry, collimation system and electronic portal imaging device (EPID) during arc deliveries. In this study, a simple EPID-based measurement method has been introduced in conjunction with an algorithm to investigate the stability of these systems during arc treatments with the aim of ensuring the accuracy of linac mechanical performance.MethodsThe Varian EPID @entity11373 , gantry @entity11373 , changes in source-to-detector distance (SDD), EPID and collimator skewness, EPID tilt, and the @entity11373 in @entity3097 carriages as a result of linac rotation were separately investigated by acquisition of EPID images of a simple phantom comprised of 5 ball-bearings during arc delivery. A fast and robust software package was developed for automated analysis of image data. Twelve Varian linacs of different models were investigated.ResultsThe average EPID @entity11373 was within 1  mm for all tested linacs. All machines showed less than 1  mm gantry @entity11373 . Changes in SDD values were within 1.7  mm except for three linacs of one centre which were within 9  mm. Values of EPID skewness and tilt were negligible in all tested linacs. The maximum @entity11373 in @entity3097 leaf bank assemblies was around 1  mm. The EPID @entity11373 showed a considerable improvement in TrueBeam linacs.ConclusionThe methodology and software developed in this study provide a simple tool for effective investigation of the behaviour of linac components with @entity717 . It is reproducible and accurate and can be easily performed as a routine test in clinics.

An EPID-based method for comprehensive verification of gantry, EPID and the XXXX carriage positional accuracy in Varian linacs during arc treatments.

@entity717 :: ('MESH:D009069', 'Disease') :: ['gantry rotation'] @entity3097 :: ('23209', 'Gene') :: ['MLC'] @entity11373 :: ('6295', 'Gene') :: ['sag']
@entity3097 :: (23209,Gene) :: ['MLC']
