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目的:评估热塑面罩固定鼻咽个体化施源器剂量的准确性及其应用价值。方法:选择10例后装放疗患者,分别制作鼻咽个体化施源器并使用面罩固定。每次治疗前均行CT扫描,并在计划系统中重建出施源器位置,获取铱源驻留位点坐标,通过与计划CT比较,计算出施源器位移偏差,进而评估后装治疗剂量的准确性。结果:非面罩固定最远端源驻留位点(P1)平均偏差在X、Y、Z三个方向为(1.62±0.24)、(2.32±0.22)和(2.50±0.28)mm,近端(P5)为(1.13±0.11)、(1.22±0.20)和(1.80±0.15)mm。经面罩固定后个体化施源器最远端源驻留位点(P1)平均位移则分别为(0.82±0.06)、(0.70±0.07)和(0.94±0.08)mm,近端(P5)为(0.70±0.02)、(0.46±0.01)和(0.60±0.03)mm。面罩固定施源器位移偏差导致的感兴趣点(源旁2cm)剂量误差<1.2%。结论:使用热塑面罩固定个体化施源器剂量准确,适合鼻咽癌腔内后装治疗。
OBJECTIVE: To evaluate the accuracy and application value of thermoplastic masks for the fixation of nasopharyngeal individualized applicators. Methods: Ten cases of post-radiotherapy were selected, and individualized nasal and nasopharyngeal devices were prepared and masked. CT scanning was performed before each treatment, and the location of the source device was reconstructed in the planning system to obtain the coordinates of the site where the iridium source resided. By comparing with the planned CT, the displacement deviation of the source device was calculated, and then the therapeutic dose Accuracy Results: The mean deviation of the maximum residing point (P1) in non-mask fixation was (1.62 ± 0.24), (2.32 ± 0.22) and (2.50 ± 0.28) mm in X, Y and Z directions, P5) were (1.13 ± 0.11), (1.22 ± 0.20) and (1.80 ± 0.15) mm, respectively. (0.82 ± 0.06), (0.70 ± 0.07) and (0.94 ± 0.08) mm, respectively. The proximal end (P5) of the individualized applicator was (0.70 ± 0.02), (0.46 ± 0.01) and (0.60 ± 0.03) mm respectively. The dose error (<2%) of the point of interest (2 cm proximal to the source) due to the displacement of the mask fixed applicator. Conclusion: The use of thermoplastic mask fixed individual source dose accurate, suitable for nasopharyngeal cavity afterloading treatment.