联合ExactTrac X-Ray与Cone Beam CT在NSCLC-SBRT中的应用分析

The application of ExactTrac X-Ray and Cone Beam CT in non-small cell lung cancer treated with stereotactic body radiotherapy

目的探讨应用ExactTrac x-Ray(ETX)与Cone Beam CT(CBCT)分析非小细胞肺癌立体定向放疗(NSCLC-SBRT)中分次间及分次内的误差差异。方法随机选取22例行SBRT的NSCLC患者,所有患者治疗前行CBCT扫描,图像配准范围为肺部肿块并兼顾胸腔轮廓与脊柱等骨性标记,获得移位误差后进行修正并开始治疗。在治疗开始及结束分别选择0°与1800进行2次ETX拍片验证(ETX-0,etx-180),从而获得分次内移位误差,图像配准范围为胸腔轮廓及脊柱等骨性标志。CBCT获得图像与定位CT图像配准得到左右(X)、上下(Y)、前后(Z)方向的平移误差和绕前后(R)方向的旋转误差,ETX拍摄获得双斜位片,与计划DRR配准后得到平移误差和旋转误差,记录两种验证方式的移位误差值,对CBCT及ETX验证进行组间配对t检验。结果分次间CBCT扫描在X、Y、Z、R方向的平均移位误差分别为(0.38±0.26)cm,(0.49±0.37)cm,(0.32±0.19)cm,(0.85±0.60)cm。分次内在X与Y方向,ETX_180较ETX_0平均移位误差分别增加21.7%与19.2%,且差异有统计学意义(P<0.05),在Z与R方向,ETX验证间差异无统计学意义(P>0.05)。结论NSCLC-SBRT分次间行CBCT图像引导能明显减少摆位误差,分次内行ETX拍片验证能有效监测单个治疗过程中的移位误差,提高治疗精度。

Objective To analyze the setup errors of interfraction and intrafraction for patients with non-small cell lung cancer treated with stereotactic body radiotherapy(NSCLC-SBRT)by using the ExactTrac X-ray(ETX)and Cone Beam CT(CBCT).Methods 22 NSCLC patients treated with SBRT were randomly selected and all patients were scanned by CBCT before radiotherapy,the treatment was started when setup errors obtained and corrected.The gantry angle of 0 and 180 degree were selected for ETX verification"at the beginning and end of the treatment,so as to obtain the intrafractional setup errors.The translational setup errors of left-right direction(X),cranio-caudal direction(Y),anterior-posterior direction(Z)and rotational setup error of round anterior-posterior direction(R)were obtained by image registration between CBCT with CT and ETX with CT,the comparison of setup errors was made using the paired t test.Results The mean setup errors by interfractional CBCT scanning in X,Y,Z and R directions were(0.38±0.26)cm,(0.49±0.37)cm,(0.32±0.19)cm,and(0.85±0.60)cm,respectively.In the intrafractional X and Y directions,the mean setup errors of ETX-180 were increased by 21.7%and 19.2%respectively compared with that ofETX_0,and the difference was statistically significant(P=0.012,P=0.013).There was no statistical difference between ETX validation in Z and R directions.Conclusion The image guidance by CBCT can significandy reduce the setup errors in NSCLC-SBRT,and the real-time ETX verification can effectively momtor the setup errors in a real-time treatment process and improve the treatment accuracy.