IGRT在颈段、胸上段食管癌放疗中的应用

The application of image-guided radiotherapy in cervical and upper-thoracic esophageal cancer radiotherapy

目的:应用kV-CBCT技术分析颈段、胸上段放疗时的摆位误差,并对其最佳配准方式和CTV-PTV外放间距进行初步探讨。方法:对11例接受3DCRT或IMRT的颈段、胸上段食管癌患者进行每周1-2次kV-CBCT扫描,分别按手动配准、骨性配准和灰度配准进行匹配,比较三种配准方式的差异,分析摆位误差,计算并比较校位前后CTV-PTV的外放间距。结果:手动、骨性和灰度配准在X轴、Y轴、Z轴的平移误差分别为(0.04±0.34)cm/(0.06±0.36)cm/(-0.02±0.29)cm、(-0.11±0.53)cm/(-0.10±0.53)cm/(0.04±0.55)cm、(0.08±0.16)cm/(0.06±0.21)cm/(-0.03±0.26)cm,三种配准方式结果均显示Y轴平移误差最大,其次为Z轴,X轴的最小;骨性配准和手动配准结果较为相近(P>0.05),灰度配准的误差值均明显小于以上两者(P<0.05);手动、骨性和灰度配准在X轴、Y轴、Z轴的旋转误差分别为(1.21±1.07)°/(1.20±1.06)°/(1.33±1.11)°、(-0.11±0.53)°/(-0.10±0.53)°/(0.04±0.55)°、(0.08±0.16)°/(0.06±0.21)°/(-0.03±0.26)°,三种配准方式结果均显示X轴旋转最大,其次为Z轴,Y轴最小,三种配准方式间无明显差异(P<0.05);骨性配准任一方向平移误差>0.3cm者,校位前X轴、Y轴、Z轴的平移误差分别为0.05±0.31cm、0.19±0.42cm、-0.06±0.37cm,校位后分别缩小至0.01±0.16cm、0.08±0.17cm、0.03±0.12cm,(P<0.05);校位前X轴、Y轴、Z轴CTV-PTV外放间距分别为0.29cm、1.03cm、0.60cm,校位后缩小至0.09 cm、0.23 cm、0.16 cm,(P<0.05)。结论:本组颈段、胸上段食管癌病例放疗时以Y轴平移误差最为明显,应用kV-CBCT实施IGRT可缩小摆位误差及CTV-PTV外放间距,配准方式以骨性配准为首选,必要时进行手动微调。

Objective： To assess the set - up errors, optimal alignment methods and optimal planning target volume （PTV） margins in cervical and upper - thoracic esophageal cancer by using kilo - voltage cone - beam CT （ kV - CBCT） guided radiotherapy. Methods： kV -CBCT scan was performed 1 -2 times per week for 11 patients with cervical and upper - thoracic esophageal cancer. Manual alignment, bone and grey alignment were performed with the same registration areas respectively, and then compared the difference between them. Set - up errors and optimal CTV -PTV margins were also analyzed. Results： The set -up errors on X,Y,Z axis were （0.04±0.34）/（0.06±0.36）/（ -0.02 ±0.29）cm,（ -0.11±0.53）/（ -0.10±0.53）/（0.04 ±0.55）cm,（0.08 ±0.16）cm/（0.06±0. 21 ）cm/（ -0. 03±0. 26）cm presented by manual alignment, bone alignment and grey alignment respectively.Set - up errors on Y axis were maximum compared with X and Z axis, bone alignment was most close to manual align- ment（P 〉 0.05）, and the set- up errors obtained by grey alignment were less than the other two alignment methods （P 〈0.05）. The rotational errors on X,Y,Z axis were（1.21 ±1.07）°/（1.20 ±1.06）°/（1.33±1.11）°,（ -0.11±0.53）°/ （-0.10±0.53） °/ （0.04±0.55） °,（0.08 ±0.16）°/（0.06 ±0.21） °/（ -0.03±0.26） ° pres- ented by manual alignment, bone alignment and grey alignment respectively. The rotational errors on X axis were maxi- mum,the Y axis were minimum. There were no significant differences between the three alignment methods for rota- tional errors（ P 〈 0.05 ）. Set - up errors more than 0.3cm in any direction need to be correct by bone alignment. The set - up errors were 0.05± 0.31 cm,0.19±0.42cm, - 0.06 ± 0.37 cm in X, Y, Z axis before correction and were re- duced to 0.01±0.16cm, 0.08 ± 0. 17cm, 0.03 ± 0. 12cm respectively （ P 〈 0.05 ） after correction. The CTV - PTV margins before correction were 0.29cm,1.03cm,0.60cm in X,Y,Z axis and were reduced to 0.09cm,0.23 cm, 0.16 cm respectively（P 〈0.05）after correction. Conclusion： The set -up errors on Y axis were more obviously in cervical and upper - thoracic esophageal cancer. The application of kV - CBCT IGRT can reduce set - up error and CTV - PTV margin. Bone alignment should be the first choice and manual turning can be applied if needed.