Effect of the setting of control point of Monaco radiotherapy planning system on dosimetry of dIMRT plan for esophageal cancer of middle and lower segment
Objective:To study the dosimetry effects of differently selected values of control point(CP)in Monaco radiotherapy planning system on dynamic intensity modulated radiation therapy(dIMRT)for esophageal cancer of middle and lower segment.Methods:Thirteen patients with esophageal cancer at middle and lower segment who received dIMRT in Shangluo Central Hospital from January to June 2023 were selected.In the Monaco radiotherapy planning system,nine groups of dIMRT plans were designed for each patient according to the 9 kinds of CP limit values(10,20,30,40,50,60,70,80 and 90).There were not changes in other optimized parameters except CP parameter.The differences of the dosimetry between target region and organs at risk(OAR)included lung,heart and spinal cord were analyzed.Results:With the increase of the CP limit value,the maximum dose of the target region which was radiation dose(D2%)of 2%volume of target region,the mean dose,which was radiation dose(D50%)of 50%volume of target region,and the homogeneity index(HI)appeared a trend of gradual stability after reduction,and the radiation dose(D98%)of 98%volume of target region which was the minimum dose of target region and the conformance index(CI)appeared a trend of gradual stability after increase.There was not significant in each dose indicator of OAR(P>0.05).The variation ranges of lung at 5,10,20,30 Gy dose(V5,V10,V20 and V30)were respectively 1.13%,0.75%,0.29%and 0.19%,and the maximum deviation of mean dose(Vmean)of lung was 18.7 cGy.The variation ranges of V10,V20,V30 and V40 in the heart were respectively 2.2%,1.23%,1.39%and 1.12%,and the maximum deviation of Vmean in the heart was 63.85 cGy,and the maximum deviation of Dmax in the spinal-cord was 70.78 cGy.There were statistically significant differences in the actual CP number(CPs),execution time(DT)of plan,and ratio value of machine unit(MU)of the complexity of plan to CPs(MU/CPs)among the plans of 9 groups(F=2.857,25.145,135.467,P<0.05),respectively.Conclusion:In the dIMRT plan of esophageal cancer of middle and lower segment,the maximum CP value is set at between 40-50,which can reduce the optimization time of the plan,the number of subfields and the treatment time of patients under the premise of meeting the dose of the target region and the OAR.
Control point(CP)Esophageal cancer of middle and lower segmentDynamic intensity modulated radiotherapy(dIMRT)planDosimetry
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