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Objective To compare the dosimetry of three different radiation therapy plans [threedimensional conformal radiation therapy (3DCRT),intensity modulated radiation therapy (IMRT),intensity modulated arc radiotherapy (IMAT)].Methods Selected 15 cases with middle thoracic esophageal cancer,Varian Eclipse 8.6 planning systems were designed with 3DCRT,IMRT,IMAT,3DCRT using 5-8 coplanar radiation fields,IMRT using 7 coplanar radiation fields,IMAT using 2 radians.Three planned dose difference were compared.Results Compared with 3DCRT,IMRT and IMAT were better with heterogeneity index (HI),conformality index (CI),VPTV 95 ％,V5,V20,V35 of total lung,and V30 of heart (t =2.531,P＜ 0.05).There was no statistically significant difference for the V10,V15,V25,V30 mean dose of total lung,the mean dose of heart,the maximum dose of spinal cord,and the minimum dose of PTV among the three plans (t =1.325,P ＞0.05).Conclusion IMAT and IMRT are similar in the middle thoracic esophageal cancer radiotherapy target volume dose coverage and organs at risk protection,they are better than 3DCRT.IMAT in the monitor units and delivery time are less than IMRT.
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Purpose To investigate the dosimetric differences among RapidArc (RA) plans which were designed on different target volumes in hepatocellular carcinoma (HCC).Methods A total of 10 HCC patients underwent 3D-CT scan under free breathing ( FB),end inspiration hold ( EIH ) associated with active breath coordinator (ABC) and 4D-CT scan.The 4D-CT were sorted into 10 sets of CT images according to respiratory cycle.The gross tumor volume (GTV) was manually contoured on different CT images.The individual internal gross target volume ( IGTV1 ) was obtained from 4D-CT,and the individual margins from GTVFB to IGTV1.IGTV2 were obtained from GTVFB using individual margins.The planned target volumes (PTV-1,PTV-2,PTV-3 and PTV-4 ) were obtained from GTVFB,IGTV1,IGTV2 and GTVEIA applying different margins.The RA plans (RA1,RA2,RA3 and RA4 ) were designed from different PTVs,and for RA1,RA2 and RA3 the simple 358° arc were used,while three 135° arcs were used for RA4.The dosimetric differences were compared.Results The PTV-1 and PTV-3 were larger than PTV-2 and PTV-4; the mean values of PtV-1/PTV-2 and PTV-1/PTV-4 were 2.5 and 1.9,respectively.There were no significant differences in conformal index,homogeneity index,maximum dose,and minimum dose of PTV among 4 RA plans.The irradiation dose of normal liver of RA3 and RA4 were 8.23 Gy and 7.63 Gy respectively,both significantly lower than those of RA1 and RA2 (10.21 Gy,9.62 Gy,x2 =10.68,P ＜0.05 ),and the V30of RA3 and RA4 were 5.24％ and 5.05％ respectively,both significantly lower than those of RA1 and RA2 (7.76％,6.12％,x2 =14.76,P ＜ 0.05 ).There were no significant differences in irradiation doses of stomach and duodenum among different plans.Conclusions Using 4D-CT or ABC technology with RapidArc in HCC can define the target volume accurately and achieve prefect dose distribution sparing more normal liver volume,compared to the traditional margins.4D-CT and ABC play similar roles in sparing normal liver.
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Objective To evaluate the performace of fixed field Intensity modulated radiation therapy (IMRT) and RapidArc in the radiotherapy for multiple intracranial metastases.Methods The clinical data of 10 patients with multiple intracranial metastases,8 male and 2 female,aged 65-73,were used to design 3 plans:fixed field IMRT,RapidArc with single Arc (RA1),and RapidArc with double Arc (Arc 2).Dose-volume-histogram analysis was used to compare dose results,monitor unit,and delivery time.Results All 3 plans met the clinical requirements.The best target conformity and homogeneity were observed in the RA2 plan (Z = -2.803,- 2.904,P ＜ 0.05) and there were no statistical differences between the IMRT plan and RA1 plan.The maximum doses to the lens,eyes,and brainstem of the two RapidArc plans were all significantly lower than those of the IMRT plan(Z = -2.803--2.191 ,P ＜0.05),and the maximum dose to the optic nerves of the RA2 plan was significantly lower than that of the IMRT plan (Z = -2.293,-2.701 ,P ＜0.05).Compared with the IMRT plan,the average monitor units of the RA1 and RA2 plans were reduced by 29% and 24%,respectively,and the delivery time of these plans were significantly shorter by 84% and 69%,respectively.Conclusions Compared to the IMRT plan,RapidArc plans with single or double Arcs show similar or better effects in the target dose distribution,reduction of irradiation doses on organs at risk and,moreover,significant decrease of the monitor units and delivery time.