Comparative Study between Electronic Portal Imaging Device (EPID) and Cone Beam Computed Tomography (CBCT) for Radiation Treatment Verifications

Introduction: Electronic Portal Imaging Device (EPID) and Cone Beam Computed Tomography (CBCT) are the preferred tools of Image Guided Radiotherapy (IGRT) and Dose Guided Radiotherapy (DGRT) which have been used for Radiotherapy treatment verifications. As a result, the number of publications dealing with these two tools for radiation treatment verification has increased considerably over the past years. This paper aims to compare and contrast the overall differences and similarities of EPID and CBCT tools based on their set-up verification accuracy, dosimetric verification accuracy, calibration and quality control methods, image quality, dose measurement, calculation, and evaluation methods for radiation treatment verifications.   Materials and Methods: The relevant articles published in English were searched based on the keywords of EPID and CBCT for radiation treatment verifications using PubMed, EMBASE, Scopus, and Web of Science databases and finally exported to EndNote for screening, downloading, and reference management processes.   Results: A total of 2512 articles were searched and subsequently screened by removing duplications and reading title and abstract to identify original articles that directly related with radiation treatment verifications using EPID and CBCT for different cases. This yielded 226 relevant articles. After downloaded and read full articles, only compared results between EPID and CBCT treatment verifications were selected. This yielded, a final total of 23 articles to be included for this work. Conclusion: EPID and MV-CBCT have almost equal potential to indicate the set-up error but since they used the LINAC’s energy, no cross-calibration procedure is needed because the imaging geometry is the same as the treatment geometry though both of them have poor image quality. The image quality of KV-CBCT is superior to both EPID and MV-CBCT and is better to indicate the set-up error. CBCT in conjunction with energy fluence maps from EPID could be used to verify the dose delivered. In this instance, a cross-calibration between the KV CBCT and EPID would be required which would not be necessary with MV CBCT. Though MV CBCT handles inhomogeneity better, soft tissue visualization is superior with KV CBCT. EPID is used to calibrate the LINAC machine. Generally, both EPID and CBCT have their own different advantages and need further study to solve their limitations.