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目的基于锥形束CT(CBCT)配准误差研究鼻咽癌治疗次间摆位误差变化和治疗工作人员主观因素对误差的影响。方法20例鼻咽癌患者,其中男性12例,女性8例;年龄31～65岁,中位年龄44岁。对其进行放射治疗,每周1次治疗前摆位CBCT扫描,在X射线容积成像(XVI)系统中与计划CT图像进行匹配,获得X、Y、Z轴平移和绕各轴旋转误差。与误差限值(平移方向<2 mm,旋转方向<2°)对比,任意一个方向大于阈值,通过六维遥控床进行自动的摆位误差校正。误差调整后再次扫描并配准获取调整后的误差。分析鼻咽癌摆位误差随着治疗变化的趋势。同时根据工作人员分组(4组)统计摆位校正的频率,分析治疗人员的主观因素对摆位误差的影响。结果在20例的第1周至第6周的数据中,Y轴和Z轴平移摆位误差及Y轴旋转有逐步减少的趋势。对4组工作人员摆位校正频率统计对比,第1组为45.61%,第3组为16.13%,差异有统计学意义(P<0.05);第2组与第4组差别不大(58.82%vs 50.00%)。结论基于CBCT校正鼻咽癌摆位误差随着治疗的进行,有一定的减小。而工作人员主观因素对误差的产生有一定的影响,应采取积极可行的措施减少这一影响。
Objective To study the effect of subjective errors on errors of nasopharyngeal carcinoma (NPC) treatment based on cone beam computed tomography (CBCT) registration error. Methods Twenty patients with nasopharyngeal carcinoma, including 12 males and 8 females, were aged 31-65 years with a median age of 44 years. Radiotherapy was performed and CBCT scans were placed once per week prior to treatment and matched with planned CT images in an X-ray volumetric imaging (XVI) system to obtain X, Y, Z axis translation and rotation errors around each axis. Compared with the error limit (<2 mm in translation direction, <2 ° in rotation direction), any one direction is greater than the threshold value, and automatic setup error correction is performed by six-dimensional remote control bed. After adjusting for errors, scan again and register for the adjusted error. Analysis of nasopharyngeal carcinoma set error as treatment trends. At the same time, according to the frequency of staffing group (4 groups), the influence of subjective factors of treatment staff on setting error was analyzed. Results In the data from the first week to the sixth week of 20 cases, the Y-axis and Z-axis translation setup errors and Y-axis rotation tended to decrease gradually. There were statistically significant differences between the four groups in terms of frequency of calibration and correction, with 45.61% in the first group and 16.13% in the third group (P <0.05). The difference between the second group and the fourth group was not significant (58.82% vs 50.00%). Conclusion The correction of nasopharyngeal carcinoma based on CBCT setup error with the treatment, a certain decrease. The subjective factors of staff have a certain impact on the production of errors, and measures should be taken to reduce the impact.