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目的:利用融合图像观察食管癌适形放疗过程中肿瘤区(GTV)的移位及体积变化情况,分析靶区变化对其受照剂量的影响,探讨食管癌三维适形放疗(3D-CRT)中二次定位的必要性及可行性。方法:40例食管癌患者接受3D-CRT,照射30Gy后行二次CT模拟定位。制定两套计划,治疗计划1(Plan1)按前半程追加处方剂量至60Gy;治疗计划2(Plan2)将后半程与前半程进行图像融合,总处方剂量60Gy,观察两套计划中GTV、CTV和PTV的受照剂量。结果:1)40例患者GTV几何中心在X、Y、Z轴上的移位分别为0.3、0.7和0.3cm,二次定位后的GTV体积、CT最大横径、最大前后径均较治疗前明显缩小,长度无明显缩短。2)Plan1中PTV2D95较PTV1D95减少约8.38%。3)Plan2中PTV2D95>PTV1D95。4)肿瘤长度>7cm、主动脉受侵者在Plan1中PTV2D95明显小于长度≤7cm及主动脉受侵阴性者。结论:食管癌3D-CRT过程中同时存在靶区移位及靶区缩小两种情况,由于靶区移位,可能会使PTV95%体积接受的剂量减少约8.38%,肿瘤长度较大合并主动脉受侵者建议行疗中二次CT定位以修正靶区剂量。
OBJECTIVE: To observe the displacement and volume change of tumor area (GTV) during the conformal radiotherapy of esophageal cancer using fusion images and to analyze the effect of the change of target area on the dose of three-dimensional conformal radiation therapy (3D-CRT) Necessity and Feasibility of Secondary Location. Methods: 40 cases of esophageal cancer patients underwent 3D-CRT, 30Gy irradiation after the second CT simulation positioning. Plan two plans to add prescription dose to 60Gy in the first half; plan 2 (Plan2) combines the second half and the first half of the image with a total prescription dose of 60Gy to observe two plans of GTV, CTV And the dose of PTV. Results: 1) The displacement of GTV geometric centers in X, Y and Z axis of the 40 patients were 0.3, 0.7 and 0.3 cm respectively. The volume of GTV, the maximum transverse diameter and the maximum anteroposterior diameter of the GTV after the second positioning were significantly lower than those before treatment Significantly reduced, no significant shortening of the length. 2) PTV2D95 is about 8.38% less than PTV1D95 in Plan1. 3) Plan2 in PTV2D95> PTV1D95.4) tumor length> 7cm, aortic invaders in Plan1 PTV2D95 was significantly shorter than the length ≤ 7cm and aortic invasion negative. CONCLUSIONS: There are two cases of target area shift and target reduction in 3D-CRT of esophageal cancer. Due to the shift of the target area, the dose of 95% of PTV volume may be reduced by about 8.38%, and the tumor length is larger with the aorta The invaders recommended second CT in the treatment to correct the target dose.