食管胸中段癌三维适形放疗中呼吸运动导致靶区剂量学变化的研究

Evaluation of respiration-induced dosimetric variance in three-dimensional conformal radiotherapy （3DCRT） for mid-thoracic esophageal carcinoma

目的 测量食管胸中段癌三维适形放疗中因呼吸运动而导致的靶区剂量学变化,为临床医师选择食管胸中段癌靶区外扩范围提供参考.方法 对10例食管胸中段癌患者行三维适形放疗定位时,分别于自由呼吸（FB）、自由吸气末屏气（IBH）及自由呼气末屏气（EBH）3个时相行相同范围的CT定位扫描.3套图像传输到计划系统并按照相同标准进行靶区的勾画.以FB时勾画的靶区制作计划Plan1,将其完全相同地移植到IBH和EBH扫描到CT上,分别得到计划Plan2和Plan3,观察呼吸运动导致的靶区剂量学变化.结果 对于GTV,3个计划仅V100之间有统计学差异（H=6.423,P=0.040）.对于CTV,3个计划仅V100、V95之间有统计学差异（F=3.992,P=0.030;H=9.920,P=0.007）.对PTV,3个计划仅Dmin、V100、V90之间有统计学差异（F=3.677,P=0.039;F=4.539,P=0.020;H=6.846,P=0.033）,脊髓、双肺在3个计划的各指标比较差异均无统计学意义.结论 按照常规标准对食管胸中段癌进行外扩时,呼吸运动导致靶区的受照剂量虽有变化,但遗漏不大,均能达到临床治疗要求.

Objective To evaluate the respiration-induced dosimetric variance in 3DCRT for midthoracic esophageal carcinoma, in order to guide the radiation oncologist to choose the expansion margin. Methods Ten patients with mid-thoracic esophageal carcinoma were scanned by multi-spiral CT simulator respectively in free breathing （ FB）, breath-hold after normal inspiration and expiration （ IBH and EBH ）with the same scanning range. Then the CT images of three series were transferred to the treatment planning system. The target volume was outlined following the same standard. Plan1 was designed in the images of FB and transported completely to the images of IBH and EBH as Plan2 and Plan3 respectively to observe the dosimetric variance in target volume. Results For GTV, there was a statistical difference only in V100 of the three plans （ H = 6.423, P = 0.040 ） and no significant difference was found in other indexes. For CTV, the V100 and V95 were better in Plan1 （F=3.992, P=0.030; H=9.920, P=0.007） and no significant difference was found in other indexes. While （）TV, the Dmin, V100 and V95 was better in Plan1 （ F = 3.677, P = 0.039; F = 4.539, P = 0.020; H = 6.846, P = 0.033 ） and no significant difference was found in other indexes. There were no significant differences in all the indexes for the spinal cord and lung in the three plans. Conclusions The change in dose distribution was not so much with the standard expansion. It can meet the needs of clinical treatment.