剂量-体积联合等效均匀剂量优化在舌癌放疗中的应用研究

Application of dose-volume combined with equivalent uniform dose optimizationin to tongue cancer radiotherapy

目的:分析和评估广义等效均匀剂量(equivalent uniform dose,EUD)优化在舌癌放疗中的剂量学优势。方法:选取16例舌癌术后患者,对每位患者制订3组逆向调强计划,第一组计划使用传统物理剂量-体积优化(Plan-DV);第二组计划在Plan-DV基础上对高危亚计划靶区(PTV60 )及侧颈部低危预防区(PTV54)增加靶区EUD目标函数(Target g-EUD);第三组计划在Plan-DV基础上对危及器官(organ at risk,OAR)增加EUD目标函数(Upper g-EUD)。分析各组计划中靶区和OAR剂量学差异。结果:相较于Plan-DV,Target g-EUD计划在靶区的适形性和均匀性上表现更好(P<0.05),在OAR保护中,两者无显著性差异。Upper g-EUD与Plan-DV计划比较,PTV60的靶区均匀性具有显著性差异(P<0.05),其他靶区剂量学参数无显著性差异;Upper g-EUD计划的脊髓和脑干的最大剂量(Dmax)分别降低了52.15和166.02 cGy,两者均呈现显著性差异(P<0.05);喉部50 Gy剂量受照体积(V50)降低了0.321%且具有统计学差异(P<0.05);左侧腮腺的平均剂量(Dmean)和30 Gy剂量受照体积(V30)、右侧腮腺V30及喉的Dmean均小于Plan-DV,两者呈现显著性差异(P<0.05)。结论:剂量-体积联合EUD目标函数不仅可以显著地改善靶区的适形度和均匀度,也可以较好地约束OAR的高剂量区域体积,在临床应用上具有指导意义。

Objective To analyze and evaluate the dosimetric advantage of equivalent uniform dose(EUD) in tongue cancer radiotherapy. Methods Sixteen postoperative patients with tongue cancer were selected and provided with three plans. The first group applied physical dose-volume(Plan-DV) optimization. Based on physical dose-volume optimization, the second group was designed through adding target g-EUD for PTV60 and PTV54. In the third group, the physical optimization combined with Upper g-EUD was used in organ at risk(OAR). All the groups had the dosimetric differences in target area and OAR analyzed statistically. Results The conformity index and homogeneity index of Target g-EUD were better than those in Plan-DV(P <0.05), while the dose distribution in OAR were trivial. The upper g-EUD and Plan-DV had no obvious differences in target dosimetry except HI of PTV60(P<0.05). In organ at risk, the maximum dose of spinal-cord in Upper g-EUD was reduced by 52.15 cGy, the maximum dose of brainstem was decreased by 166.02 cGy, and all the differences were statistically significant. The V50 for larynx was significantly lowered by 0.321%(P<0.05). The Dmean and V30 of parotid-L, the V30 of parotid-R and the Dmean of larynx were statistically lower than those of Plan-DV(P <0.05). Conclusion Combined with physical opti-mization, EUD objective function could significantly influence not only conformity and homogeneity in target,but also "hot points" in OAR, which is of obvious guiding significance in clinical application.