准直器有无转角对乳腺癌保乳术后动态调强放疗剂量学的影响OA

Objective:To compare effect of collimator with and without rotation angle on dosimetric parameters of dynamic intensity modulated radiation therapy(D-IMRT)plan after breast-conserving surgery.Methods:A retrospective collection of medical records was conducted on 30 patients who underwent breast-conserving surgery for breast cancer at the Department of Radiotherapy of Beijing Luhe Hospital,Capital Medical University,from November 2022 to March 2024.Among them,15 cases had breast cancer on left side and 15 cases had that on right side.Two kinds of radiotherapy plans were formulated for all patients,which included Plan-A(without rotation angle plan)and Plan-B(with rotation angle plan).The dosimetric parameters of target volume[Conformity Index(CI)and Homogeneity Index(HI)]and organs at risk(breast of healthy side,heart,esophagus,trachea,and spinal cord)of two kinds of plans were compared.Statistical analysis of dosimetry parameters was performed using SSPS27.0 software.Results:The D2%(6215.78±46.219)cGy and HI(0.237±0.014)of planning target volume(PTV)in Plan-B were lower than those[D2%(6232.723±49.148)cGy and HI(0.241±0.013)]in Plan-A,and the differences were statistical significance(t=4.032,2.626,P<0.05).There were not significant differences at D98%,Dmean,and CI between the two plans(P>0.05).There were significant differences at D2%,Dmean,and CI of planning gross target volume(PGTV)between Plan-B and Plan-A(t=2.451,3.870,-3.063,P<0.05),respectively.However,there were not statistically significant differences at D98%and HI between the two kinds of plans(P>0.05).The V5,V10,and Dmean values at lung of the affected side of Plan-B were lower than those of Plan-A,and the differences were significant(t=6.315,3.694,3.780,P<0.05).There were not significant differences at V20 and V30 between the two plans(P>0.05).The maximum dose(Dmax)of the healthy side of breast,and Dmean of heart of Plan-B were lower than those of Plan-B,and the differences were significant(t=5.233,5.099,P<0.05).There were not significant at esophagus,spinal cord,trachea,and machine unit(MU)between two kinds of plans(P>0.05).Conclusion:For IMRT after breast-conserving surgery for breast cancer,rotating angle of collimator not only can obtain better conformity in the target volume,but also the exposure of low dose on lung of affected side,the breast of healthy side and heart can be further decreased.