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Objective To study the step aceuracy of 252Cf neutron afterloading radiotherapy machine and the dose deviation caused by step deviation.Methods EBT3 film was used to measure the steps of the 252Cf neutron source,and then the center of each 252Cf neutron source was identified by measuring the optical density value by using the ImageJ software.Double ion chambersmethod was used to measure the dose deviation dlue to the 252 Cf neutron source position shift.Results 252 Cf neutron source step accuracy may amount to 0.01 mm using EBT3 film measurement,when 252Cf neutron source position deviation is less than 3 mm,the dose deviation is less than 2.5％.Conclusions The study on the step accuracy and position deviation of the 252Cf neutron source can provide a reference for the quality control standard of the 252Cf neutron afterloading radiotherapy machine.
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Objective To compare the efficacy between californium?252 ( 252 Cf ) neutron intraluminal brachytherapy combined with external?beam radiotherapy with lead?shielding pelvic parallel opposing field technique and non?lead?shielding four?field box technique for cervical cancer. Methods A total of 52 patients with stage Ⅱa?Ⅲb cervical squamous cell carcinoma who were admitted to our hospital from 2004 to 2007 were enrolled as subjects and paired by clinical stage, age, tumor size, and degree of anemia. The 26 pairs of patients were divided into lead?shielding pelvic parallel opposing field group (lead?shielding group) and non?lead?shielding four?field box group (non?lead?shielding group). For all patients in both groups, 252 Cf neutron brachytherapy was added in external?beam radiotherapy. The local control (LC), overall survival (OS), and disease?free survival (DFS) rates were calculated using the Kaplan?Meier method and analyzed using the log?rank test. The difference in the incidence of late complications was analyzed using the McNemar method. Results There were significant differences in 5?year LC, OS, and DFS rates between the lead?shielding group and the non?lead?shielding group (85% vs. 81%, P= 0?? 014;89% vs. 73%, P=0?? 013; 89% vs. 73%, P= 0?? 013 ). There was also significant difference in the incidence of late complications between the lead?shielding group and the non?lead?shielding group ( 12% vs. 23%, P=0?? 008). Conclusions When intraluminal brachytherapy combined with external?beam radiotherapy is used to treat cervical cancer, the centers of the front and back fields should be shielded by lead, regardless of whether the parallel opposing field technique or the four?field box technique is used.
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Objective:To study the dose measurements methods of neutron andγ-ray for 252Cf neutron after-load radiotherapy machine. Methods:To measure the neutron-γmixed field with one ion chamber that have the similar sensitivities of neutron andγ-ray, another ion chamber that only have sensitivities for γ-ray, little sensitivity for neutron. Verification measurement results with calculated values. Results:Calculate key parameters, measure neutron andγ-ray dose rate at the position of 2.5cm, 5cm, 7.5cm and 10cm from the 252Cf, the Maximum deviation is-5.22%compared with calculated values. Conclusion:The method of twin ion chamber can measure the neutron andγ-ray mixed field dose.
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Objective To explore the relationship between esophageal carcinoma extensive infiltration and lesion length and 252 Cf intracavitary brachytherapy,and to evaluate its prognostic influence.Methods Thirty-two patients with esophageal carcinoma were treated by external beam and 252Cf intracavitary radiation.The patients were first treated with conventional fractionated radiation to a dose of 38 Gy over 4 weeks,with 5 daily fractions of 2 Gy per week,and then treated with external and intracavitary radiation concomitantly (4.0 Gy per fraction,once a week on every Saturday to 12 Gy in 3 fractions).The total dose of external irradiation was 50 Gy.Results The local control rate (LCR) at 1,3 and 5 years was 93.75％,76.70％ and 65.75％ in the patients with ≤5 cm lesion (NMT5 group),and 60.94％,27.08％ and 27.08％ in the patients with ＞5 cm lesion (MT5 group),respectively (x2 =7.01,P ＜ 0.05).The 1-,3-and 5-year survival rate (SR) was 93.75％,56.25％ and 43.75％ in the NMT5 group,and 75.00％,18.75％,12.50％ in the MT5 group,respectively (x2 =5.96,P ＜ 0.05).The LCR at 1,3 and 5 years was 92.31％,73.85％ and 61.54％ in the patients with ≤1.5 cm infiltration depth (NMT1.5 group),and 67.67％,35.45％ and 35.45％ in the patients with ＞ 1.5 cm infiltration depth (MT1.5 group),respectively (x2 =3.87,P ＜ 0.05).The 1-,3-and 5-year SR was 92.31％,61.54％ and 46.15％ in the NMT1.5 group,and 73.68％,21.05％ and 15.79％ in the MT1.5 group,respectively (x2 =6.24,P ＜ 0.05).LCR and SR in the patients with ≤5 cm lesion and ≤2 cm infiltration depth were significantly better than those with ＞ 5 cm lesion and ＞ 2 cm infiltration depth (x2 =10.09,7.97,P ＜ 0.05).Conclusions The patients with ≤5 cm lesion length or those with ≤ 1.5 cm infiltration depth,might become the most adaptable indication for 252 Cf intracavitary radiation.In addition,those patients with ≤2 cm infiltration depth and ≤5 cm lesion length were also suitable for 252Cf intracavitary radiation.
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Objective To investigate the specific activity of 24Na per unit neutron fluence,AB/Φ,in blood produced for Chinese reference man irratiaded by 252Cf neutron source,and to analyze the effects of scattering neutrons from ground,wall,and ceiling in irradiation site on it.MethodsA 252Cf neutron source of 3 × 108 n/s and the anthropomorphic phantom were used for experiments.The phantom was made from 4 mm thick of outer covering by perspex and the liquid tissue-equivalent substitute in it.The data of phantom dimensions fit into Chinese reference man.The weight ratios of H,N,O and C in substitute equal from source to long axis of phantom were 1.1,2.1,3.1 and 4.1 m,respectively.Both the neutron source and the position of xiphisternum of the phantom were 1.6 m above the floor.ResultsThe average specific activity of 24Na per unit neutron fluence was related to the irradiation-distances,d,and its The AB/ΦM corresponds to that of phantom irradiated by plane-parallel beams,and the value is about more 3% than that by BOMAB phantom reported in literature.It has shown that floor-( wall-)scattered neutrons in irradiation site have significant contribution to the specific activity of 24Na ,but they contributed relatively little to the induced neutron doses.Consequently,using the specific activity of 24 Na for assessing accidental neutron doses received by an individual,the contribution of scattered neutrons in accident site will lead dose to be overestimated,and need to be correct.
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Objective To investigate the potential effect of 4-amino-pynidine(4-AP)on human cervical carcinoma cell line HeLa to 252Cf neutron ray.Methods HeLa cells were treated with 4-AP(0,1,5,10,20 mmol/L,respectively)and then exposed to 0.67 Gy 252Cf neutron ray.The effect of 4-AP on proliferation of HeLa cells was assessed by MTT assay.Cell apoptosis were detected by flow cytometry.Reverse transcription polymerase chain reaction(RT-PCR)and Western blotting were used to investigate the levels of HIF-1? mRNA and protein of HeLa cells treated with 4-AP(0,20 mmol/L)and 0.67 Gy 252Cf neutron ray.Results After HeLa cells treated with 0,1,5,10,20 mmol/L 4-AP were exposed to 0.67 Gy 252Cf neutron ray for 48 h,their inhibitory rate was 0,(38.81 ?3.45)%,(46.63?3.88)%,(63.58?6.19)%,(77.51?8.87)%,and their apoptotic rate was(3.15?0.85)%,(8.01?1.19)%,(16.00?1.58)%,(47.20?3.18)%,(62.56?4.27)%,respectively,suggesting 4-AP may inhibit the proliferation of HeLa cells and induce their apoptosis in a dose-dependent manner(P0.05).However,after treated with 20 mmol/L 4-AP and exposed to 0.67 Gy 252Cf neutron ray for 24,48 and 72 h,the optical density ratio of HIF-1? mRNA/?-actin of HeLa cells was(0.401?0.121),(0.364?0.142),(0.257?0.137),(0.165?0.099),while the optical density ratio of HIF-1? protain/?-actin were(0.879?0.117),(0.645?0.115),(0.312?0.114),(0.130?0.118),showing that the levels of HIF-1? mRNA and protein both declined(P
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Objective Apuinic/apyrimidic endonuclease/redox effector factor-1(APE1/Ref-1,abbreviated as APE1) is a major member of the base excision repair(BER) pathway involved in oxidative DNA damage repair.To knock down APE1 gene expression in HOS cells with pSilence APE1,and explore its effect in combination with 252Cf neutron ray radiotherapy.Methods The constructed APE1 siRNA expression vector pSilence APE1 was transfected into HOS cells by SuperFect Transfection liposome,and it was used to knock down the expression of APE1.The HOS cells and transfected HOS cells were respectively irradiated by 252Cf neutron ray,then the cell survival(D0),DNA single strand breaks(SSB) and cell apoptosis were determined by clone formation assay,alkaline comet assay and flow cytometer.Results The cell-survival curve was plotted by clone formation assay,the D0 value was 2.80 vs.1.89 and Dq value was 2.66 vs.2.00 for the control and transfected HOS cells,respectively,after being irradiated by 252Cf neutron ray.The tail moments at 2,5 and 10 Gy were 6.664?0.648 vs.7.997?0.542,20.322?1.433 vs.25.238?1.185 and 33.909?1.245 vs.39.191?1.052,respectively,for the control and transfected HOS cells,and the cell apoptosis rate at 2,5 and 10 Gy was 4.00 vs.5.68,5.91 vs.7.55 and 9.63 vs.13.51,respectively,for the control and transfected HOS cells.All these findings showed significant difference between the two groups(P