Tomotherapy MVCT不同配准方式对头颈部摆位的影响

Effects of different registration methods for Tomotherapy MVCT on head and neck positioning

目的:评估螺旋断层放射治疗(Tomotherapy,TOMO)兆伏级CT(MVCT)不同配准方式对头颈部摆位的影响。方法:首先基于室内激光和体表标记对头颈部模体进行摆位,行MVCT图像引导并自动配准,误差修正后将其作为参考图像。随后进行单、双及3方向移床(-5~5 mm,步长1 mm),分别用Bone、Bone and Tissue和Full Image方式进行配准,最后记录左右(X)、头脚(Y)、腹背(Z)的摆位误差。结果:不同配准方式下,Bone的摆位误差最小。在Fine 1 mm模式下,Bone和Bone and Tissue配准存在显著差异,摆位误差分别为0.5(0.3,0.8)mm和0.6(0.4,0.8)mm;在Fine 2 mm模式下,Bone和Bone and Tissue配准同样存在显著差异,摆位误差分别为0.4(0.3,0.7)mm和0.5(0.4,0.8)mm。在Normal 2 mm和Coarse 3 mm模式下,3种配准方式均存在显著差异(P<0.05)。在Fine 2 mm和Normal 2 mm模式下,3种图像配准均无差异(P>0.05)。不同配准方式下,Y方向相关性最低。CTV-PTV外放Margin值在Bone配准方式下,X、Y、Z 3个方向分别为2.1、2.8、2.2 mm;Bone and Tissue配准方式下,X、Y、Z 3个方向分别为2.1、2.7、2.2 mm;Full Image配准方式下,X、Y、Z 3个方向分别为2.2、3.0、2.2 mm。结论:综合3种模式相同的扫描长度、扫描时间和剂量考虑,在TOMO临床治疗头颈部患者时,可选择Normal模式,优先选择Bone配准方式。

Objective To evaluate the effects of different registration methods for Tomotherapy megavoltage computed tomography(MVCT)on head and neck positioning.Methods The head-and-neck phantom was positioned based on indoor laser and body surface markers and then received MVCT scan.After automatic image registration and error correction,the obtained image was used as the reference.Subsequently,the treatment couch was artificially moved in single,2 and 3 directions(from-5 to 5 mm,with a step length of 1 mm).Three different kinds of methods,namely Bone,Bone and Tissue,Full Image,were adopted for image registration.The positioning errors in left-right(X),superior-inferior(Y)and anteriorposterior(Z)directions were recorded.Results When adopting Bone for image registration,the positioning errors were the smallest.In Fine 1 mm and 2 mm modes,there were significant variations for the positioning errors between registration using Bone and registration using Bone and Tissue,and the positioning errors were 0.5(0.3,0.8)mm and 0.6(0.4,0.8)mm for Fine 1 mm mode,and 0.4(0.3,0.7)mm and 0.5(0.4,0.8)mm for Fine 2 mm mode.In Normal 2 mm and Coarse 3 mm modes,there were significant differences among 3 registration methods(P<0.05);while in Fine 2 mm and Normal 2 mm modes,no significant difference was found(P>0.05).Whatever registration method was adopted,the correlation in Y direction was the lowest.The CTV-PTV Margin in X,Y and Z directions were 2.1,2.8,2.2 mm for Bone,2.1,2.7,2.2 mm for Bone and Tissue,and 2.2,3.0,2.2 mm for Full Image,respectively.Conclusion Based on the comprehensive consideration on 3 modes,with the same scan length,scan time and dose,Normal mode combined with Bone is preferentially recommended in clinical Tomotherapy for patients with head and neck cancer.