ABSTRACT
Background and purpose:As a new and important radiotherapy technique,intensity-modulated radiation therapy(IMRT) has been widely used in the clinic,but it requires longer time to deliver for one treatment session.The purpose of this study was to investigate the radiobiological effects of CNE and A549 cell lines irradiated by IMRT model.Methods:Part Ⅰ:The radiobiological characteristics of CNE and A549 cell lines were studied with standard clonogenic assays,using standard liner-quadratic model and incomplete repair model to fit the dose-survival curves.Part Ⅱ:a total dose of 8 Gy was given in two fractions with different interfraction intervals to compare the differences of cell surviving fractions(SF).Part Ⅲ:fractionated irradiation of 2 Gy,2 Gy?2,2 Gy?3,2 Gy?4 were given with one fraction per day simulating clinical dose-time-fractionation pattern in 2,20 and 40 min per fraction,respectively.Results:The ?/? of CNE and A549 was 1.76 and 12.41 Gy,respectively;the cell surviving fractions increased when the interfraction interval was longer,The values of SF2 were 0.0237 and 0.0243 in 2 min irradiation group,0.0304 and 0.0296 in 20 min irradiation group,and increased to 0.0378 and 0.0359 in 40 min irradiation group,respectively.Conclusion:The prolonged fraction delivery time would significantly decrease theradiobiological effects,it is strongly recommended that the delivery time be kept as short as possible,or do appropriate dose compensation.