【摘要】 目的:研究放射治疗摆位时旋转、平移误差的相关性,探索减少分次放疗摆位误差的方法,以提高肿瘤放疗摆位的稳定性与精确性。方法:收集2015年7月至2017年12月期间接受调强放疗的70位鼻咽癌患者,按首次摆位旋转误差值进行分类:将旋转误差<2°设为对照组;旋转误差≥2°设为研究组。所有病例连续1周行锥形束CT扫描。首次放疗前对校正前、后分别进行一次锥形束CT扫描。结果:对照组首次摆位测得X、Y、Z方向校正前、后误差为:(1.05±0.73)、(1.20±0.74)、(1.44±1.20)mm;(0.43±0.29)、(0.41±0.25)、(0.39±0.30)mm。研究组首次摆位测得X、Y、Z方向校正前、后误差为:(1.17±0.91)、(1.61±1.27)、(1.43±0.82)mm;(0.62±0.35)、(0.83±0.39)、(0.77±0.44)mm。校正前摆位误差无显著性差异(P>0.05);校正后研究组摆位误差显著大于对照组(P<0.05)。对照组首次摆位、分次间摆位通过率为:88.57%、82.86%、71.43%和97.10%、97.10%、94.86%。研究组首次摆位、分次间摆位通过率为:71.43%、60.00%、68.57%和89.71%、82.29%、83.43%。放疗前首次摆位X、Y轴方向摆位误差通过率对照组高于研究组(P<0.05),Z轴无显著性差别(P>0.05);分次间摆位X、Y、Z轴方向摆位误差通过率对照组都高于研究组(P<0.05)。在X、Y、Z方向上研究组外放边界较对照组分别增大0.84、1.19、1.30 mm。旋转误差分布结果显示RX与Z轴有强相关,与Y轴中等相关;RY与X、Y、Z轴均为中等相关;RZ与X轴有强相关,与Y轴中等相关。结论:放射治疗过程中旋转误差对平移误差影响较大,旋转误差较大时平移误差也较大,尤其在放疗过程中分次间误差显著增大。减少旋转误差能有效地提高鼻咽癌放疗摆位精确度与稳定性。更多还原

【Abstract】 Objective To study the correlation between rotational errors and translational errors in the intensity-modulated radiotherapy(IMRT) of nasopharyngeal carcinoma(NPC), and explore the method to reduce the setup error of fractionated radiotherapy for improving the stability and accuracy of patient positioning in radiotherapy. Methods Seventy patients receiving IMRT for NPC between July 2015 and December 2017 were enrolled in this study. According to the rotational errors at the first setup, the patients were assigned into control group(rotational errors<2°) and study group(rotational error≥2°). All patients received cone beam CT for a week. Before the first radiotherapy, cone beam CT was performed before and after correction. Results The first setup errors in X, Y, Z directions before and after correction were(1.05±0.73),(1.20±0.74),(1.44±1.20) mm and(0.43±0.29),(0.41±0.25),(0.39±0.30) mm in control group;(1.17±0.91),(1.61±1.27),(1.43±0.82) mm and(0.62±0.35),(0.83±0.39),(0.77±0.44) mm in study group. There was no significant difference in the setup error before correction(P>0.05). After correction, the setup errors of study group were significantly greater than those of control group(P<0.05). Significant differences were found in the passing rates of the first setup errors in X and Y directions which were higher in control group than in study group(88.57% vs 71.43%, 82.86% vs 60.00%, all P<0.05),not in the passing rates of the first setup errors in Z direction(71.43% vs 68.57%, P>0.05). The passing rates of the setup errors in fractionated radiotherapy in control group were 97.10%, 97.10%, 94.86%, respectively, significantly higher than89.71%, 82.29%, 83.43% in study group(P<0.05). MPTV in X, Y, and Z directions in control group were increased by 0.84,1.19, and 1.3 mm, compared with those values in control group. The analysis of rotational errors showed that Rxwas strongly correlated with the Z axis, moderately correlated with the Y axis, and that RYwas moderately correlated with the X,Y, and Z axes, and that Rzhad a strong correlation with the X axis and a moderate correlation with the Y-axis. Conclusion Rotational errors have remarkable effects on the translational errors during radiotherapy. When the rotational error is large,the translational error is also large. Reducing the rotational error can effectively improve the accuracy and stability of patient positioning in radiotherapy for NPC.更多还原