鼻咽癌放疗中红外定位系统与锥形束CT的摆位精度比较

Comparison of positioning accuracy between optical positioning system and cone beam CT in nasopharyngeal carcinoma radiotherapy

目的评价红外定位系统(OPS)在鼻咽癌放疗摆位中的应用价值。方法以36例行放疗的鼻咽癌患者为研究对象,采用个性化头枕与头颈肩热塑膜进行体位固定,CT扫描前于热塑膜上固定6个红外光反射定位球。首次治疗时采用锥形束CT(CBCT)(千伏级)进行位置验证与移床校正。以CBCT肿瘤中心摆位值为参考,对OPS与室内激光定位系统肿瘤中心摆位值进行比较与分析。记录OPS与CBCT摆位的一致性、摆位时间,并分析OPS摆位误差的稳定性。结果OPS与CBCT在左右方向(X轴)、腹背方向(Y轴)、头脚方向(Z轴)的摆位一致性分别为94.4%、75.0%与97.2%,室内激光定位系统在X轴、Y轴、Z轴的摆位一致性分别为69.4%、72.2%与44.4%。OPS与CBCT在X轴、Z轴的摆位一致性高于室内激光定位系统,差异有统计学意义(P<0.05),在Y轴的一致性二者无统计学差异(P>0.05)。OPS摆位时首次与第二次摆放X轴的摆位平移误差(Bone-T-LR)、Y轴的摆位平移误差(Bone-T-AP)、Z轴的摆位平移误差(Bone-T-CC)、X轴的摆位旋转误差(Bone-R-LR)、Y轴的摆位旋转误差(Bone-R-AP)与Z轴的摆位旋转误差(Bone-R-CC)均无统计学差异(P>0.05)。OPS摆位与CBCT摆位的平均时间分别为(1.8±0.6)min与(9.4±3.1)min;OPS摆位时间显著短于CBCT(t=14.442,P=0.000<0.05)。结论鼻咽癌放疗时采用OPS摆位与CBCT具备较好的一致性,且稳定性好,摆位时间明显缩短,也可避免CBCT导致的额外辐射,可提升鼻咽癌放疗的安全性和操作效率,具备较高的应用价值。

Objective To evaluate the application value of optical positioning system(OPS)in radiotherapy positioning of nasopharyngeal carcinoma.Methods 36 patients with nasopharyngeal carcinoma receiving radiotherapy were studied.Personalized head pillow and head,neck and shoulder thermoplastic film were used for body position fixation,and 6 infrared light reflection positioning balls were fixed on the thermoplastic film before CT scan.Cone beam CT(CBCT)(kV level)was used for position verification and shift bed correction during the first treatment.Based on CBCT tumor center positioning values,OPS and indoor laser positioning system tumor center positioning values were compared and analyzed.The alignment and positioning time of OPS and CBCT were recorded,and the stability of the OPS positioning error was analyzed.Results The alignment of OPS and CBCT in left and right direction(X-axis),abdominal and dorsal direction(Y-axis)and head and foot direction(Z-axis)were 94.4%,75.0%and 97.2%,and those of the indoor laser positioning system in X-axis,Y-axis and Z-axis were 69.4%,72.2%and 44.4%.The alignment in X-axis and Z-axis of OPS and CBCT was significantly higher than that of indoor laser positioning system,and the difference was statistically significant(P<0.05),and the alignment in Y axis was not statistically significant(P>0.05).There was no statistically significant difference(P>0.05)in translation errors of the X-axis(Bone-T-LR),Y-axis(Bone-T-AP),Z-axis(Bone-T-CC),and rotation errors of X-axis(Bone-R-LR),Y-axis(Bone-R-AP),and Z-axis(Bone-R-CC)during the first and second OPS positioning.The average time of OPS positioning was(1.8±0.6)min,which was significantly shorter than(9.4±3.1)min of CBCT positioning(t=14.442,P=0.000<0.05).Conclusion In nasopharyngeal carcinoma radiotherapy,OPS positioning has good consistency with CBCT,with good stability and significantly shortened positioning time,which can avoid additional radiation caused by CBCT,improve the safety and operation efficiency of nasopharyngeal carcinoma radiotherapy,and have high application value.