运用CBCT测量肺癌放疗的摆位误差

Kilo-voltage Cone Beam CT for Radiotherapy Set-up Errors in Lung Cancer

目的用直线加速器机载千伏级锥形束CT扫描技术探讨肺癌患者的摆位误差,为实行肺癌放疗计划时CTV外放到PTV提供参考数据。方法 41例肺癌患者随机分为A、B两组,其中A组患者20例应用Elekta Synergy直线加速器治疗,B组21例用Varian Trilogy TX直线加速器治疗。全组患者在首次放疗前均用千伏级CBCT进行扫描,在治疗过程中根据情况每周进行扫描,将得到的千伏级CBCT扫描图像与计划CT图像进行匹配,记录并分析两组患者的靶区中心分别在Lateral左右(X)、Longitudinal头脚(Y)、Vertical背腹(Z)方向上的误差值及其误差分布情况,比较两台加速器摆位误差的差异,并计算两台治疗系统MPTV外放边界大小。结果 A、B两组患者的系统误差(均数)±随机误差(标准差)的平移误差在X、Y、Z方向分别为(1.79±0.15)mm、(2.16±0.17)mm;(3.71±0.28)mm、(4.29±0.32)mm;(1.66±0.15)mm、(1.96±0.18)mm。A组患者在X、Y、Z三个方向的摆位误差均小于B组患者,但差异无统计学意义(均P>0.05);用两种加速器治疗的患者在X、Y、Z方向的MPTV分别为X:4.36 mm、4.94 mm;Y:8.22 mm、9.20 mm;Z:4.38 mm、5.02 mm。结论利用CBCT能够比较准确的测算出肺癌靶区中心在X、Y、Z方向上的误差值。

Objective To investigate the set-up errors in lung cancer patients by kilo-voltage cone beam CT (kvCBCT) technology,and to provide the reference data for clinical target volume (CTV) to planning target volume (PTV) in radiotherapy.Methods Forty-one patients with lung cancer were divided randomly into two groups:Group A (20 cases) were treated with Synergy linear accelerator,and Group B (21 cases) were treated with Trilogy TX linear accelerator.All patients underwent kvCBCT before radiotherapy and every week during the treatment as needed.Set-up errors of kvCBCT were calculated according to its matched and planned CT images in left-right(X),superior-inferior(Y) and anterior-posterior(Z) axes.Difference of set-up errors was compared between two accelerators and margin of planning target volume (MPTV) was calculated.Results The set-up errors of Group A and B in X,Y and Z axes were (1.79±0.15) mm and (2.16±0.17) mm,(3.71±0.28) mm and (4.29±0.32) mm,(1.66±0.15) mm and (1.96±0.18) mm,respectively.Set-up errors in three axes in Group A were less than those in Group B(P＞0.05).MPTV of Group A and B in X,Y and Z axes were 4.36 mm and 4.94 mm,8.22 mm and 9.20 mm,4.38 mm and 5.02 mm,respectively.Conclusion Application of kvCBCT could significantly reduce the set-up errors of radiotherapy in patients with lung cancer.