目的 应用Elekta Synergy 加速器的千伏级锥形束CT(KV-CBCT) (kilovoltage cone-beam computed tomography)精确量化分析非小细胞肺癌 患者在立体定向放射治疗中的体位变化情 况，为临床医生设计非小细胞肺癌立体定 向放疗计划时临床靶体积CTV(clinical target volume，CTV)到计划靶体积 PTV(planning target volume，PTV)的 外放数据提供参考。方法 选取2013年3 月-2014年2月使用ELEKTA Synergy 加速 器进行放射治疗的10例非小细胞肺癌的患 者，在放射治疗前进行千伏级锥形束CT 即KV-CBCT的扫描，获得患者在X轴左右 (left-right，LR)，Y轴头脚(superiorinferior，SI)和Z轴前后(anteriorposterior，AP)三个方向的摆位误差数 据，并对误差进行校正，然后进行统计 学的比较。结果 患者在左右(X)，头脚 (Y)，前后(Z)三个方向上的摆位误差分别 为(0.34±0.21)cm，(0.47±0.17)cm和 (0.37±0.19)cm。校正后的摆位误差在 X，Y和Z三个方向上分别为(0.09±0.14) cm，(0.11±0.15)cm和(0.06±0.12)cm， 得出X，Y，Z方向的Mptv 值分别为X为 0.41cm，Y为0.58cm，Z为0.43cm。结论 通过KV-CBCT对非小细胞肺癌立体定向放 疗摆位误差的校正，可以缩小各种系统误 差和随机误差，为临床医生制定放疗计划 时提供扩边数据。

Objective To quantitative analyze the change of the position accurately using Elekta synergy accelerator by KV-CBCT (kilovoltage cone-beam computed tomography) for patients of non-small cell lung cancer(NSCLC) with stereotactic body radiation therapy(SBRT), design plan of NSCLC with SBRT from CTV to PTV to offer reference to external data, to provide for a reasonable margin of PTV the basis for clinical doctors. Methods To collect from March 2013 to February 2014, using Elekta synergy accelerator radiotherapy for 10 cases of patients with NSCLC, using KV-CBCT scans before radiotherapy, acquired the XVI were registered to planning CT and the set up errors were obtained on the X axis (left-right, LR), the Y axis (superior-inferior, SI) and Z axis (anterior-posterior, AP) and the errors correction, then compared statistically. Results The set up errors on the X axis (left-right, LR), the Y axis (superior-inferior, SI) and Z axis (anterior-posterior, AP) were (0.34±0.21)cm, (0.47±0.17)cm and (0.37±0.19)cm, in three dimensional directions, respectively; the set up errors correction on X, Y, Z were(0.09±0.14)cm, (0.11±0.15)cm and (0.06±0.12)cm, respectively. According to vanHerk formula Mptv=2.5Σ+0.7σ, calculated Mptv of X, Y, Z were 0.41cm, 0.58cm, 0.43 cm directions, respectively. Conclusion By the KV-CBCT for set up errors correction of NSCLC with SBRT, can greatly reduce all kinds of system error and random error, to provide the margin data when design the radiotherapy plan. According to the results of residual set up errors evaluation, 0.6cm should be applied to the margin of PTV.