Background & objective: Due to its good dosimetric properties, amorphous silicon electronic portal imaging device (a-Si EPID), as a rapid two-dimensional dosimetric measurement device, presents an attractive prospect in routine quality assurance (QA) test, dosimetric verification of intensity-modulated radiotherapy treatment (IMRT) and in vivo dose monitoring. This study was to explore the application of a-Si EPID as a detector for dosimetric QA of linear accelerator radiotherapy, and setup the calibration module.
Methods: The imaging calibration procedure of conventional a-Si EPID was modified for dosimetric measurement by acquiring the traditional "flush field" from integrated subfields to correct the dosimetric responding difference in pixel sensitivity. The energy dependence of the a-Si EPID detectors was analyzed through off-axis dose response curves. Calibrated dose profile obtained with a-Si EPID was compared with the measuring results of ion chamber in a 3-D water phantom.
Results: The calibrated dose profiles measured with a-Si EPID showed a deviation within 2% in high dose regions, but dropped much steeply in the penumbra region, as compared with that scanned using ion chamber in water.
Conclusion: With the modeling management set up in this research, a-Si EPID can be applied for dosimetric QA of linear accelerator in radiotherapy.