4D-CT检测非小细胞肺癌立体定向放疗中呼吸运动引起危及器官剂量的变化

Changes of dose to organs at risk caused by respiratory movement in stereotactic body radiotherapy for non-small cell lung cancer with 4D-CT

目的采用四维计算机断层扫描(4D-CT)检测研究非小细胞肺癌(NSCLC)体部立体定向放射治疗(SBRT)中10个呼吸时相肺、脊髓等危及器官(OAR)的剂量变化。方法收集2020年1至10月浙江省人民医院22例未进行手术的NSCLC患者的临床影像学资料。根据肿瘤位置分为内部肿瘤组(肿瘤完全位于肺内部且与胸壁距离≥1 cm)11例和边缘肿瘤组(肿瘤位于肺内靠近胸壁且距离胸壁<1 cm)11例。均行4D-CT扫描,分别在4D-CT的10个呼吸时相图像上进行肿瘤靶区(GTV)勾画,叠加生成内靶区(IGTV),将其外放生成计划靶区(PTV)。在平均密度投影(AIP)图像上进行放疗计划的设计,将AIP图像上计划形变配准到10个呼吸时相,记录并比较肺5 Gy、20 Gy以及30 Gy剂量下的绝对体积V_(5)、V_(20)、V_(30)以及肺平均剂量(Dmean-lung),体5 Gy、20 Gy以及30 Gy剂量下的绝对体积V_(5)、V_(20)、V_(30)以及体平均剂量(D_(mean-external))、脊髓最大剂量(D_(max-sp))和体最大剂量(D_(max-external))。结果两组患者肺V_(20)、肺V_(30)、体V_(20)、D_(mean-external)的变化差异均有统计学意义(均P<0.05),而肺V_(5)、Dmean-lung、体V_(5)、体V_(30)、D_(max-sp)、D_(max-external)变化的差异均无统计学意义(均P>0.05)。内部肿瘤组肺体积变化和各个肺、体剂量变化的差异均有统计学意义(均P<0.05),边缘肿瘤组肺体积变化和各个肺、体剂量变化的差异均无统计学意义(均P>0.05)。结论4D-CT检测可以更加精确地计算和评估肿瘤组织和OAR剂量,为患者个体化精确放疗的实施提供依据。

Objective To investigate the dose changes to organs at risk(OAR)caused by respiratory movement in stereotactic body radiotherapy(SBRT)for non-small cell lung cancer(NSCLC)detected with four-dimensional computed tomography(4D-CT).Methods The clinical imaging data of 22 patients with NSCLC who were not admitted in Zhejiang Provincial People's Hospital from January 2020 to October 2020 were retrospectively analyzed.All patients underwent conventional 4D-CT scans.The gross tumor volume(GTV)was drawn on the images of 10 breathing phases of 4D-CT,then the internal gross tumor volume(IGTV)was generated,and planning target volume(PTV)was generated by outward expansion.The radiotherapy plan was designed on the average intensity projection(AIP)images,and then the plan on the AIP image deformation was registered to 10 breathing phases to compare the dose changes in lung,spinal cord and other organs at risk and the dosimetry was analyzed.Results There were significant differences in the changes of lung volume and lung and body dose in lung internal tumor group(P<0.05).There was no significant difference in the changes of lung volume and lung and body dose in lung marginal tumor group(P>0.05).The changes of lung dose were greater than that of body dose in each group,and there was no significant difference between the maximum dose of spinal cord and body(P>0.05).Conclusion There are dosimetric differences among different breathing phases,and respiratory movement has a certain impact on the dose,Therefore,the time factor should be taken into account for four dimensional dose calculation to make the dose more accurate.