宫颈癌内外照射中基于CBCT外照射摆位误差分析

目的 利用CBCT数据分析研究宫颈癌内外照射中的摆位误差以指导临床工作。方法选取2015年3—6月间肿瘤医院收治的Ⅱ_A—Ⅲ_B期宫颈癌内外联合照射患者60例，以及同期收治的常规宫颈癌外照射Ⅱ_A—Ⅲ_B期患者60例。统计每例患者首次治疗的CBCT摆位误差，即x、y、z轴向摆位误差及计算的三维向量偏差。采用独立样本t检验比较两种技术误差。结果 将数据线性拟合后发现，随定位参考点与靶区中心点距离变大，x、y、z轴向摆位误差均有增大趋势。与常规外照射摆位误差相比，内外联合照射的分别在x、y、z轴向缩小，分别为0.13±0.12∶0.31±0.24(P=0.000)、0.23±0.18∶0.47±0.36(P=0.001)、0.18±0.11∶0.27±0.18(P=0.001)。结论 为更好减少摆位误差，定位CT扫描时除尽可能靠近肿瘤治疗中心位置设定参标记点外，还应尽量选择更精确可靠的体位固定技术。

Setup errors of external-beam and intracavitary radiotherapy for cervical cancer:an analysis based on cone-beam computed tomography

Objective To analyze the setup errors of external-beam and intracavitary radiotherapy for cervical cancer based on the data of cone-beam computed tomography (CBCT), and to provide a basis for clinical practice. Methods Sixty patients with stage Ⅱ_A-Ⅲ_B cervical cancer who were admitted to our hospital and underwent external-beam and intracavitary radiotherapy from March to June, 2015 were enrolled as subjects. Sixty patients with stage Ⅱ_A-Ⅲ_B cervical cancer undergoing conventional external-beam radiotherapy within the same period were also enrolled. The CBCT-based setup errors, containing setup errors in x, y, and z directions and three-dimensional vector deviation, in the initial treatment were obtained from each patient. Comparison of errors between the two treatment approaches was made by independent-samples t test. Results Fitting the data to a linear model revealed that the setup errors in x, y, and z directions increased with the increase in the distance between the position reference point and the center point of the target volume. External-beam radiation combined with intracavitary radiation had significantly reduced setup errors in x, y, and z directions than the conventional external-beam radiation (0.13±0.12 vs. 0.31±0.24, P=0.000;0.23±0.18 vs. 0.47±0.36, P=0.001;0.18±0.11 vs. 0.27±0.18, P=0.001). Conclusions In order to reduce the setup errors, CT scan needs not only a reference marker as close as possible to the center of the tumor, but also a reliable and accurate approach for postural fixation.