四维CT前瞻式呼吸门控技术在肺部肿瘤放疗中的应用研究

Application of prospective respiratory gating based on 4D-CT in precise radiotherapy for lung cancer

目的研究使用基于四维CT呼吸门控技术时的肿瘤靶区脱靶情况,探索放疗过程中门控准确性。方法收集2018—2019年在南京医科大学附属肿瘤医院放疗科行四维CT呼吸门控放疗的18例肺部肿瘤患者资料,获取患者治疗时的呼吸波形数据,对比分析各治疗工作周期中体表波形与采集四维CT时的体表波形,研究肺癌患者放疗过程中是否存在脱靶的可能。结果18例患者共154个治疗分次、20790个治疗呼吸周期,其中7例患者共95个治疗呼吸周期门控开束脱靶振幅阈值Δm-en>0,占所有周期的0.46%,有13例患者共1419个治疗呼吸周期的门控关束脱靶振幅阈值Δm-dis>0,占所有周期的6.83%。13例Δm-dis>0的患者,实际肿瘤运动范围值(R_(G))均大于靶区外放范围值(M)与计划靶区运动范围值(R_(T))之和,R_(G)大于M+R_(T)值1.5倍以上者为7例,出束时相中含有处于呼吸曲线急速上升和下降时相者也为7例。R_(G)-M-R_(T)值与开束脱靶周期百分比(T_(en)%)、关束脱靶周期百分比(T_(dis)%)的相关系数分别为0.41、0.57。结论呼吸门控放射治疗时,R_(G)大于M+R_(T)值1.5倍以上且门控出束时相中含有处于呼吸曲线急速上升和下降中的时相,将导致放射治疗脱靶的可能性大幅增加。

Objective The respiratory waveform of lung cancer patients based on 4D-CT respiratory gating was analyzed to evaluate the accuracy of gating during radiotherapy,and to explore the off-target in the 4D-CT respiratory gating radiotherapy.Methods Clinical data of 18 patients with lung cancer admitted to Radiotherapy Department of Jiangsu Cancer Hospital were collected to obtain the respiratory waveform data during 4D-CT respiratory gating radiotherapy.The waveform in each treatment working cycle was compared with the waveform in 4D-CT scan to study whether there was a possibility of the off-target in the treatment of lung cancer patients.Results There were 154 treatment sessions and 20,790 treatment breathing cycles in 18 patients,among which the threshold of gated opening beam miss amplitude(Δm-en)was greater than 0 in 95 treatment breathing cycles in 7 patients,accounting for 0.46%of all breathing cycles,and the threshold of gated closing beam miss amplitude(Δm-dis)was greater than 0 in 1419 treatment breathing cycles in 13 patients,accounting for 6.83%of all cycles.Among the 13 patients withΔm-dis greater than 0,actual tumor range of motion(R_(G))was greater than the sum of the value of target margin(M)and the value of plan tumor range of motion(R_(T))in 7 patients,R_(G)was more than 1.5 times of M+R_(T)in 7 patients,and there were also 7 patients in the phase of rapid rise and fall of respiratory curve.The correlation efficients between R_(G)-M-R_(T)and the percentage of beam on miss phase(T_(en)%)and the percentage of beam closing off phase(T_(dis)%)were 0.41 and 0.57,respectively.Conclusion When R_(G)is more than 1.5 times of M+R_(T)value and the gating beam on phase contains the phases in the rapid rise and fall of the respiratory curve,the possibility of the off-target during radiotherapy is significantly increased.