Dosimetric Comparison of Amorphous Silicon EPID and 2D Array Detector for Pre-Treatment Verification of Intensity Modulated Radiation Therapy

作     者：Ayman G. Ibrahim Ismail E. Mohamed Hamdy M. Zidan 

作者机构：Radiation Oncology & Nuclear Medicine Department Mansoura University Hospitals Mansoura Egypt Department of Biophysics Faculty of Medicine Ain Shams University Cairo Egypt Department of Physics Faculty of Science Damietta University Egypt 

出 版 物：《International Journal of Medical Physics, Clinical Engineering and Radiation Oncology》 (医学物理学、临床工程、放射肿瘤学（英文）)

年 卷 期：2018年第7卷第4期

页      面：438-452页

学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学] 

主　　题：IMRT EPID 2D Array Detector Gamma Index Quality Assurance 

摘      要：Purpose: To study the dosimetric characteristics of amorphous silicon Electronic Portal Imaging Device EPID and 2D array detector for dose verification of radiotherapy treatment plans, and the quality assurance QA testing of IMRT was investigated. Materials and methods: All measurements were done with Varian IX linear accelerator, aSi-1000 EPID and 2D array detector. The dose linearity, reproducibility, output factors, dose rate, SDD and response with slap phantom thickness have been measured and compared against those measured by ion chamber. Results: The characteristics of EPID and 2D array: the response of EPID agreed with 2D array and ion chamber 0.6cc. EPID and 2D array showed short-term output reproducibility with SD = 0.1%. The dose rates of 2D array SD = ±0.7%, EPID = ±0.4% compared with a 0.6 cc SD = ±0.5%. Output factor measurements for the central chamber of the EPID and 2D array showed no considerable deviation from ion chamber measurements. Measurement of beam profiles with the EPID and 2D array matched very well with the ion chamber measurements in the water phantom. The EPID is more sensitive to lower energy photons by increasing solid water phantom thickness. The mean and standard deviation passing rates (γ%≤1) for film, 2D array and EPID for 30 IMRT fields of five patients were 95.93 ± 0.96%, 99.05 ± 0.24%, and 99.37 ± 0.12%, respectively. Conclusion: The study shows that EPID and 2D array are a reliable and accurate dosimeter and a useful tool for quality assurance. We found that the EPID was more accurate compared with both 2D array and ion chamber. The gamma criterion of 3%/3 mm is the most suitable criteria for IMRT plans of QA.