左侧乳腺癌保乳术后三种调强放疗的剂量学研究

Dosimetric Study of 3 Intensity-modulated Radiotherapy for Left Breast Cancer after Breast Conserving Surgery

目的比较左侧乳腺癌保乳术后3种不同射野数调强放疗方式(IMRT)的靶区及周围正常组织受照剂量的差异。方法选取8例左侧乳腺癌保乳术后患者,应用Pinnacle8.0计划系统分别设计3种不同射野数的调强计划:4野、5野、6野IMRT计划,用剂量体积直方图(DVH)和等剂量曲线评估3种计划的PTV和周围正常组织受照剂量。结果6F-IMRT靶区剂量分布最优,其剂量均匀性和适形度最好,5F-IMRT其次,4F-IMRT最差。与4F-IMRT比较,5F-IMRT和6F-IMRT的PTV最大剂量以及高剂量所包含的体积显著降低。3种计划左肺照射剂量差异较小,均不超过5%;然而心脏照射剂量4F-IMRT最小,与5F-IMRT和6F-IMRT比较,心脏V5、V10、V20、V30以及V40分别降低了42.37%、17.65%、5.87%、5.72%、23.38%和42.85%、30.84%、16.31%、6.45%、24.65%。结论左侧乳腺癌保乳放疗中,调强射野数的增加可以提高靶区PTV覆盖率、适形度和均匀性,但是也会增高左肺低剂量照射体积和平均剂量,右侧肺和心脏的受照剂量也会明显增高,故应根据患者实际情况应用合适的放疗计划进行放疗。

Objective To compare the dosimetric difference in target area and normal organs between 4F-IMRT,5F-IM-RT and 6F-IMRT for left breast cancer after breast conserving surgery .Methods For each of 8 randomly chosen patients ,3 IM-RT plans (4F-IMRT,5F-IMRT and 6F-IMRT) were designed with Pinnacle 8.0.95%of target volume received prescribed dose 50 Gy,the dose distributions in target area and normal organs with the DVH and isodose curves .Results The dose uniformity in target area was improved with increasing of the numbers of beam .Compared with 4F-IMRT,the maximum dose of 5F-IMRT and 6F-IMRT in PTV and high dose of the volume was significantly reduced .With regard to the normal organs for 3 plans,the ad-sorbed dose and volume in left lung were not significant different ,while in right lung and heart were obvious .With 5F-IMRT and 6F-IMRT,V5、V10、V20、V30 and the mean dose in 4F-IMRT were decreased by 42.37%,17.65%,5.87%,5.72%,23.38%and 42.85%,30.84%,16.31%,6.45%,24.65%,respectively.Conclusion For left breast cancer after breast conserving surgery treated with radiotherapy ,the increase in the number of intensity-modulated fields can improve conformality and homogeneity of PTV,while increase the low adsorbed dose volume of left lung and the dose volume of right lung and heart .Appropriate radiation plan should be choosed according to the actual situation of patients .