食管癌自适应放疗不同累加方法对危及器官受照剂量的差异比较

目的比较食管癌自适应放疗时,三种累加方法所得危及器官(Organs at Risk,OARs)受照剂量的差异。方法回顾性分析50例根治性食管癌自适应放疗计划,PTV:50 Gy/25 f,PGTV:60 Gy/30 f。在治疗20~25 f期间重新CT模拟定位,根据肿瘤靶区退缩情况制定自适应放疗计划。通过人工计算(A组)、治疗计划系统(B组)和MIM多模态形变配准系统(C组)三种方法分别计算双肺、心脏及脊髓的累加受照剂量。结果方差分析显示双肺V5差异有统计学意义(F=8.933,P<0.001),A组最小为(51.95±12.67)%;V20差异无统计学意义(P>0.05)。心脏V40差异有统计学意义(F=3.590,P<0.05),A组最大为(17.69±12.48)%。脊髓Dmax差异有统计学意义(F=5.587,P<0.001),A组最大为(43.98±2.23)Gy。结论食管癌自适应放疗时,人工计算方法会低估双肺的低剂量受照体积,并会高估脊髓的最大受照剂量。建议采用TPS计算或MIM多模态形变配准系统进行OARs受照剂量的累加计算。

Comparison of Different Cumulative Methods of Adaptive Radiotherapy for Esophageal Cancer on the Dose of Exposed Organs at Risk

Objective To compare the dose differences among organs at risk(OARs)from the three cumulative methods of adaptive radiotherapy for esophageal cancer.Methods A total of 50 cases of radical esophageal cancer with adaptive radiotherapy plan,PTV:50 Gy/25 f,PGTV:60 Gy/30 f were retrospectively analyzed.During the treatment of 20~25 f,the CT simulation was repositioned,and the adaptive radiotherapy plan was developed according to the tumor target area retreat.The cumulative dose of double lung,heart and spinal cord was calculated by manual calculation(group A),treatment planning system(group B)and MIM multi-modal deformation registration system(group C).Results The difference of V5 in both lungs was statistically significant(F=8.933,P<0.01),and the smallest was(51.95±12.67)% in group A.There was no significant difference in V20(P>0.05).The cardiac V40 difference was statistically significant(F=3.590,P<0.05),and the maximum value in group A was(17.69±12.48)%.The difference of spinal cord Dmax was statistically significant(F=5.587,P<0.01),and the maximum was(43.98±2.23)Gy in group A.Conclusion In the adaptive radiotherapy of esophageal cancer,the artificial calculation method may underestimate the low dose exposure volume of both lungs and overestimate the maximum dose exposure of spinal cord.It is suggested to use TPS calculation or MIM multi-modal deformation registration system to calculate the cumulative dose of OARs.