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[目的]研究鼻咽癌患者在调强放疗过程中两次模拟定位CT之间的剂量融合中的关键技术:模体移位。[方法]28例接受调强放疗的鼻咽癌患者,在照射25次时再次CT模拟定位,利用CORVUS6.3调强治疗计划系统,比较模体移位前后二次融合方法中剂量分布的变化。[结果]28例患者不同方向上的位移均值分别为:右/左(R/L):X=-2.19±20.91mm(-50.22～43.21mm);前/后(A/P):X=-2.14±8.61mm(-16.76～16.28mm);脚/头(I/S):X=6.85±20.51mm(-30.11～48.98mm)。Plan2中GTVnx处方剂量体积比和CTV处方剂量体积比均较Plan1和Plan3中减少;而所有的周围危及器官剂量均较Plan1和Plan3中增加。Plan2与Plan3配对t检验发现,GTVnx处方剂量体积比的差异、CTV处方剂量体积比的差异、脊髓最大剂量的差异、脊髓V40的差异均有统计学意义(P<0.0001)。[结论]在二次模拟定位CT之间,有较大的模体移位,可以通过CORVUS6.3调强治疗计划系统自动纠正模体移位方式,消除严重的模体移位,得到实际的融合靶区剂量分布。
[Objective] To study the key technology of phacoemulsification in pharyngeal radiation therapy for twice-simulated-dose CT in patients with nasopharyngeal carcinoma (NPC): phantom shift. [Methods] Twenty-eight patients with nasopharyngeal carcinoma undergoing intensity modulated radiotherapy were retrospectively analyzed by CT. The intensity of treatment planning system was adjusted by CORVUS 6.3 and the changes of dose distribution in the two fusion methods were compared . [Result] The average displacement of 28 patients in different directions were: right / left (R / L): X = -2.19 ± 20.91mm (-50.22 ~ 43.21mm) -2.14 ± 8.61mm (-16.76 ~ 16.28mm); feet / head (I / S): X = 6.85 ± 20.51mm (-30.11 ~ 48.98mm). Plan2 GTVnx prescription dose volume ratio and CTV Prescription dose volume ratio than Plan1 and Plan3 to reduce; and all peripheral organ dose than Plan1 and Plan3 increased. The paired t-test between Plan2 and Plan3 showed that there were significant differences (P <0.0001) in the dose-volume ratio of GTVnx prescription, the dose-volume ratio of CTV prescription, the maximum dose of spinal cord and spinal cord V40. [Conclusion] There is a large phantom shift between secondary simulated CT and CORVUS6.3 IMRT planning system, which can automatically correct the phantom displacement and eliminate the severe phantom shift, and obtain the actual Fusion target dose distribution.