Eclipse系统的通量平滑技术在头颈部肿瘤放疗中的应用

Application of fluence-smoothing technique of Eclipse system in intensity-modulated radiotherapy for head and neck tumors

目的:基于Edge系统,评估通量平滑技术在头颈部放疗中的应用。方法:采用Eclipse v13.6计划系统对40例头颈部肿瘤患者做回顾性分析,每位患者制定6组逆向调强计划,包括对照组(Smooth 0,0)即X和Y平滑值为0、实验Ⅰ组(Smooth 20,20)、实验Ⅱ组(Smooth 40,40)、实验Ⅲ组(Smooth 60,60)、实验Ⅳ组(Smooth 80,80)和实验Ⅴ组(Smooth 100,100)。评估各组计划靶区及危及器官的剂量学差异,分析平均叶片对展宽(ALPO)、MU factor及γ通过率。结果:与对照组相比,实验组的PCTV60和PCTV54的HI、PCTV60 CI和喉V50均存在统计学差异(P<0.05);实验Ⅱ~Ⅴ组脊髓Dmax存在统计学差异(P<0.05);实验Ⅳ与实验Ⅴ组喉Dmean存在统计学差异(P<0.05);实验Ⅲ与实验Ⅴ组左侧腮腺V30存在统计学差异(P<0.05);实验Ⅱ与实验Ⅳ组左侧腮腺Dmean存在统计学差异(P<0.05);实验V组右侧腮腺V30与Dmean具有统计学差异(P<0.05)。随着通量平滑值的增加,PCTV60 CI呈现先增加后降低趋势(Smooth 40,40最大),PCTV60和PCTV54的HI则呈现先减小后增加低趋势(Smooth 40,40最小)。MU factor则先呈现降低趋势(Smooth 0,0到Smooth 60,60),随后呈现增加趋势(Smooth 60,60到Smooth 100,100)。γ通过率、喉V50和ALPO随平滑度增长呈现增长趋势,而机器跳数呈现下降趋势。结论:适度的平滑值降低了计划投照复杂性,过度的平滑则影响靶区覆盖率并且提高危及器官的受量。基于临床需求及硬件限制,头颈部放疗计划的X和Y平滑值建议设为40。

Objective To analyze and evaluate fluence-smoothing technique in the radiotherapy for head and neck tumors based on Edge system.Methods The clinical information of 40 postoperative patients with head and neck tumors were retrospectively analyzed,and 6 reverse intensity-modulated radiotherapy(IMRT)plans were designed for each patient with Eclipse v13.6 system.The 6 groups of plans included control group(Smooth 0,0)which were optimized with the smoothing values of X,Y at 0,experimentalⅠgroup(Smooth 20,20),experimentalⅡgroup(Smooth 40,40),experimentalⅢgroup(Smooth 60,60),experimentalⅣgroup(Smooth 80,80)and experimentalⅤgroup(Smooth 100,100).The dosimetric differences of target areas and organs-at-risk were evaluated among different groups,and the average leaf pair opening(ALPO),MU factor and gamma passing rate were also analyzed.Results Compared with the dosimetric parameters in control group,there were statistical differences in the HI and CI of PCTV60,the HI of PCTV54 and the V50 of larynx in experimental groups(P<0.05),the Dmax of spinal cord in experimentalⅡtoⅤgroups(P<0.05),the Dmean of larynx in experimentalⅣandⅤgroups(P<0.05),the V30 of parotid-L in experimentalⅢandⅤgroups(P<0.05),the Dmean of parotid-L in experimentalⅡandⅣgroups(P<0.05),and the V30 and Dmean of parotid-R in experimentalⅤgroup(P<0.05).With the increase of smoothing values,the CI of PCTV60 showed an increasing and then decreasing trend(reaching the maximum in Smooth 40,40 plan),while the HI of PCTV60 and PCTV54 presented a decreasing and then increasing trend(reaching the minimum in Smooth 40,40 plan).MU factor also showed a decreasing(Smooth 0,0 to Smooth 60,60)and then increasing tendency(Smooth 60,60 to Smooth 100,100).Moreover,gamma passing rate,the V50 of larynx and ALPO were increased as the increase of smoothing values,while MU showed a decreasing tendency.ConclusionModerate fluence-smoothing reduces the complexity of plan delivery,but excessive fluence-smoothing affects target coverage and increases the dose of OAR.Based on clinical demands and linac limitations,the smoothing values of X,Y should be set at 40.