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Objective To investigate the influence of intensity-modulated radiation pattern on ra-diobiological effects of nasopharyngeal carcinoma cell line CNE2.Methods Colony formation assay was used to calculate cell surviving fraction, and compare the cell survival curves and the surviving fraction with single-hit multi-target model fitting survival curves to different delivery time and dose rates.Results ⑴Nasopharyngeal carcinoma cell line CNE2 was irradiated on two models:conventional radiation ( CR) mod-el;intensity modulated radiation model ( IMRT model, which was divided into 10 min IMRT irradiated group, 15 min irradiated group, and 20 min irradiated group) .Except that the parameters of radiation biol-ogy did no significantly differ between CR model and 10 min IMRT irradiated group ( P >0.05) , the other groups among radiobiology parameters surviving fraction (SF2), quasi-threshold dose(Dq) and extrapolation number(N) were all significant differences ( P SF2 600 Mu/min ( P <0.05) when the CNE2 cells were treated with dose rates of 300 Mu /min and 600 Mu/min.Conclusions ⑴There were not significant changes in the biological effects until the delivery time prolonged to more than 10 minutes.When the delivery time extended to more than 15 minutes, the survival fraction was increasing with the radiation time risen.⑵The dose rates used in the experiment did not show any effect on the radiobiology parameters without SF2 .
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Objective To compare the planning quality and volume of organ at risk (OAR) between volumetric-modulated arc therapyv (VMAT) and nine-field dynamic intensity-modulated radiation therapy (IMRT) in radiotherapy for cervical cancer patients,explore the best way to cervical cancer radiotherapy,Methods Selected 20 patients with cervical cancer were divided into 2 groups,10 cases for each group.Cervical cancer patients with no surgery was performed for A group (group A),received the radical radiotherapy,prescription dose gross tumor volume (GTV) 56 Gy,clinical target volume (CTV) 50 Gy.Another group of patients with cervical cancer radical surgery (group B),giving the whole basin lymph node auxiliary radiation therapy,prescription dose CTV 50 Gy.Each cervical cancer patient received VMAT and IMRT program designs,the differences in dose volume histogram (DVH),irradiated volume of organ at risk (OAR),heterogeneity index (HI),conformity index (CI),maximum dose (PTVmax),minimum dose (PTVmin) and mean dose (PTV mean) were compared between two plans in 2 groups.Results Two kinds of radiation technology in target area dosimetry were not statistical difference between two groups (P ＞ 0.05).In endanger organs on the protection of two groups of VMAT planning groups in the small intestine V20 and left femoral head V20 had obvious advantages with statistically significance (P ＜ 0.05).Conclusions Two groups of dosimetry between VMAT and IMRT program design are similar in cervical cancer.Two groups of VMAT planning groups to protect endanger organ slightly better than that of IMRT group,but VMAT planning group shortens treatment time and improves the accuracy and efficacy of treatment.