应用千伏级锥形束CT对非小细胞肺癌立体定向放疗PTV外放边界研究

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。

Study on the Margin of PTV using KV-CBCT for Non-small Cell Lung Cancer with Stereotactic Body Radiation Therapy

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.