The study of two-dimensional dosimetric verifications of volumetric intensity-modulated arc therapy based on electronic portal imaging devices

Objective: To develop an accurate 2D dose reconstruction model using electronic portal imaging device (EPID). 2D dosimetric verifications of volumetric intensity-modulated arc therapy (VIMAT) were done using the model. And the results were compared to other dosimeters. Methods: The EPID-based dose reconstruction model was using convolve, deconvolve and correction function. The dose profiles which were obtained by the ion chamber were used to determine the model parameters. A total of 12 VIMAT plans for the treatment of anatomical sites of various complexities were chosen. The results obtained from EPID were compared to other dosimeters and treatment planning system (TPS). The ion chamber was used to measure the central point absolute doses. Other dosimeters were used to measure the plane dose distributions. All dosimeters measured the dose at 10 cm depth. The results were analyzed using #gamma#-evaluation method. Results: Regarding absolute central point doses, the ion chamber results were within 1.5% of the EPID results. For the comparison to Seven29 and Matrixx, the average #gamma# pass rates with 2% and 2 mm criteria were 98.9% and 99.8% respectively. For the dose distributions measured by EPID and calculated by TPS, the 7 pass rates with 3% and 3 mm criteria were 99.9%. Conclusions: The presented results which were obtained from the comparison of measured and calculated doses show the reliability of our EPID-based dose reconstruction model. With the model, EPID can be a reliable and fast tool for IMRT plan dosimetric verification. The model expanded to the 3D dosimetric verification in the uniform phantom will be considered as the next work. (authors)