The Accurate Radiotherapy Biological Effects Of Image-Guided Radiotherapy

Image-guided radiotherapy (IGRT) is one style of accurate radiotherapy, in which imaging is performed within the treatment room prior to irradiation to improve geometric irradiation accuracy. IGRT makes use of many different imaging techniques, using modalities ranging from portal imaging to fluoroscopy to megavoltage cone-beam computed tomography and following regimens as simple as a single setup image or as comples as intrafraction tumor tracking. Despite the promises, one major concern often raised on the imaging radiation daily at diagnostic dose as compared to conventional radiotherapy, which could potentially increase the risk of radiation-induced carcinogenesis, particularly in long-term survivors. Focusing on solving these situations, we will invstigate the radiobiological effects induced by Image-Guided Radiotherapy.The radiobiological effects induced after exposed to cone-beam CT (CBCT) radiation in primary human lung fibroblast cells MRC-5had been studied. Both the double strand breaks (DSBs) and cytokinesis-block micronucleus (CBMN) were detected. The result of this study revealed that even single CBCT imaging radiation can increase the foci of y H2AX in vitro, and after three days’CBCT raidation, the cytokinesis-block micronucleus frequency was found to be closed to the micronucleus frequency after exposed to the0.5Gy dose irradiation.The cell cycle effects of the CBCT were detected in human lung cancer cells A549. As compared to non-exposed groups, there were no differences in the cell cycle distribution after incubation. Furthermore, patient will exposed to prescription dose radiation after reposition by exposed to CBCT radiation. This special raidation mode may induce the adaptive response. In this research, we compared the apoptosis frequency of A549cells in2Gy irradiation group to the group both accepted CBCT and2Gy irradiation. No difference of apoptosis frequency was found in these groups. These results indicated that the special mode of IGRT did not induce the adaptive response in A549cells, which means that it will impair the outcome of IGRT.A new method based on the treatment planning system to estimate the risk of second cancers was introduced in this paper. The risk of second primary cancer was estimated over two treatment plans for a patient with pancreatic cancer. A better plan was chosen by the analysis of second primary cancer risk.These data will provide some bases and might give some hints to for clinical IGRT application.