一种实用的照射方式在胸中段食管癌中的应用

摘要

We designed a practical radiotherapy method to compare the dose distribution of normal tis-sue for the middle esophageal cancer patients. Methods:Thirty patients of middle esophageal cancer who refused op-eration received the CT positioning in order to contour their target area,then designed two groups of radiotherapy plan. Group A treated by 3D - CRT in combination with IMRT(10 fractions and 20 fractions with five fields),but the last 20 fractions must reduce the included angle between the first two beam angles and the zero angle,so we fixed the beams at 0°,42°,144°,216°,318°. IMRT for group B treated with the equal distribution of five beam angles(30 frac-tions). 2Gy per fraction and 30 fractions in total for both group A and B. Finally after normalizing the 60Gy prescrip tion dose attained by 95% of the PTV volume,compare the following parameters the dose volume histogram(DVH), the maximum dose of spinal cord(Dmax ). The respective volume of heart when given 50Gy,40Gy,30Gy,20Gy and mean heart dose(Mheart )(the volume values of this article were all expressed as a percentage),the volumes of the lungs when given 50Gy,40Gy,35Gy,30Gy,25Gy,20Gy,15Gy,10Gy,5Gy and mean lung dose(Mlung ). Results:The maximum dose of spinal cord in group A increased compared with group B(P ﹤ 0. 05);The volumes of heart in group A indicated only V40 and V50 increased compared with group B(P ﹤ 0. 05);Besides V35 and V40 in group A,the rest of the lungs'data were reduced compared with group B(P ﹤ 0. 02). Conclusion:The middle esophageal cancer patients treated with the radiotherapy of group A,and the irradiation volume significantly decreased in low dose region for the bilateral lungs,the dose of heart and spinal cord were all in the tolerant range.%目的：在胸中段食管癌的放疗中我们设计了一种实用的照射方式，并与正常组织的剂量分布情况进行比较，为临床胸中段食管癌放疗计划的选择提供参考。方法：选择30例胸中段食管癌且拒绝手术的患者进行 CT 定位扫描，并由主治医师勾画出放疗靶区，每例患者均由物理师设计两组放疗计划，其中 A 组为调强与适形放疗相结合的方式（先给予适形放疗10次，而后行5野照射的调强放疗20次），但在后20次的调强放疗计划中需减少两前斜野与零度野之间的夹角，因此我们将 A 组调强计划的照射野固定为0°、42°、144°、216°、318°；B 组为5野均分的调强放疗（30次），A、B 两组的单次剂量均为2Gy，放疗30次。最后均以95% PTV 体积获得60Gy 处方剂量进行剂量归一，再利用剂量体积直方图（DVH）对以上两组计划进行正常组织受量的比较：脊髓最大点受量（Dmax ）；心脏受量为50Gy、40Gy、30Gy、20Gy 及心脏平均受量（Mheart ）的体积值（本文中的体积值均以百分比表示）；双侧肺受量分别为50Gy、40Gy、35Gy、30Gy、25Gy、20Gy、15Gy、10Gy、5Gy 及肺部平均受量 Mlung时的体积值。结果：A 组脊髓 Dmax受量较 B 组增加（P ﹤0.05）；A 组心脏受量仅 V40及 V50较 B 组增加（P ﹤0.05）；A 组双侧肺部受量除 V35及 V40外，其余各组数据均较 B 组降低（P ﹤0.02）。结论：采用 A 组方法照射的胸中段食管癌患者，其双侧肺部的低剂量区受照射体积显著降低，心脏及脊髓的受量均在耐受范围内。