锥形束CT结合六维床HexaPOD验证及纠正放疗中摆位偏差的研究

Verification and Correction of Positioning Deviation in Radiotherapy with Cone Beam CT and HexaPOD Treatment Couch

目的探索用锥形束扫描CT(Cone Beam Computed Tomography,CBCT)验证放疗技师摆位偏差大小及六维床HexaPOD纠正摆位偏差的能力和稳定性,为临床提供数据参考。方法回顾性分析本院2018年6月至2019年6月经影像学和病理学证实的340例不同治疗部位的肿瘤患者,收集每位患者首次扫描CBCT后的摆位误差数据,验证不同部位摆位偏差的大小。另选取18例对摆位要求较高的特殊病例,收集每个病例首次摆位、首次六维床纠正偏差后及治疗分次间摆位偏差结果,分析CBCT和六维床HexaPOD纠正偏差的能力和治疗分次间验证的必要性。结果头颈部摆位偏差明显小于其他部位(P<0.05)。18例特殊病例,经首次摆位偏差纠正后,x、y、z平移方向和Rx、Rz旋转方向数值均减小(P<0.05)。分次间摆位偏差因人为摆位因素仍然存在且数值变大(P<0.05)。分次间纠正偏差后的残余偏差数值稳定,且无统计学差异(P>0.05),经纠正后的数值可达到亚毫米和亚度。结论CBCT和六维床HexaPOD联合验证、纠正摆位偏差,可使各方向摆位偏差减小;分次间建议合理安排CBCT扫描次数。

Objective To explore how to use cone beam computed tomography(CBCT)to verify the magnitude of position deviation of radiotherapy technician and the ability and stability of the HexaPOD treatment couch to correct the errors,so as to provide clinical reference data.Methods In a retrospective analysis of 340 patients with tumors at different sites confirmed by imaging and pathology in our hospital in the period from June 2018 to June 2019,the position deviation data of each patient after the initial scan of CBCT were collected to determine the magnitude of position deviation in different parts of the human body.In addition,18 special cases with more stringent positioning requirements were selected,of which the deviation corresponding to positions after initial positioning and after correction of HexaPOD treatment couch,and before the second treatment fraction were recorded.These data were used to assess the capability of CBCT and HexaPOD treatment couch to correct for the position deviation,and to confirm the need for verification between treatment fractions.Results The position deviation for head and neck were significantly smaller than other parts(P<0.05).As regards the 18 studied special cases,all initial position deviation were substantially reduced upon corrections,with statistical significance(P<0.05)in the translational directions of x,y,and z and rotational directions of Rx and Rz.However,after corrections of initial position deviation,these devotion would become significantly(P<0.05)larger again after the first treatment fraction due to human errors.The residual translational and rotational after each correction through CBCT were consistent,in that no statistically significant differences were observed(P>0.05).All translational and rotational position deviation after corrections were small,which reached the sub-millimeter and sub-degree levels,respectively.Conclusion Position deviation in all directions were reduced with the help of CBCT and HexaPOD treatment couch.Further corrections through CBCT scans between treatment fractions are recommended.