目的 测量非小细胞肺癌(NSCLC)患者纵隔转移淋巴结分次内的位移,为NSCLC纵隔转移淋巴结内靶区的确定提供依据.方法 增强CT扫描显示纵隔淋巴结转移(短径≥1 cm)的24例NSCLC患者,在自由呼吸状态下,行大孔径CT模拟定位并获得四维CT(4D-CT)图像.在治疗计划系统中,分别勾画10个呼吸时相4D-CT图像上显示清楚的纵隔转移淋巴结及同侧膈肌顶层,并依据被勾画淋巴结所在的区域将其分为上、中、下纵隔3组,获得每个被勾画淋巴结在左右、前后和上下方向上的位移及三维运动矢量.比较同一区域纵隔淋巴结在不同方向上的位移差异、不同区域纵隔淋巴结在相同方向上的位移差异和三维运动矢量的差异,分析纵隔淋巴结位移与同侧膈肌位移的相关性.结果 全组53个纵隔淋巴结在左右、前后和上下方向上的位移分别为(2.24±1.55)mm、(1.87±0.92)mm和(3.28±2.59) mm.全组及上、中、下纵隔淋巴结的三维运动矢量分别为(4.70±2.66)mm、(3.87 ±2.45) mm、(4.97 ±2.75)mm和(5.23 ±2.67) mm.上纵隔淋巴结在左右、前后和上下方向上的位移差异均无统计学意义(均P＞O.05)；中纵隔淋巴结在前后与上下方向上的位移差异有统计学意义(P =0.005),而在左右与前后方向、左右与上下方向上的位移差异均无统计学意义(均P＞0.05)；全组及下纵隔淋巴结在左右与上下方向、前后与上下方向上的位移差异均有统计学意义(均P ＜0.05),而左右与前后方向间的位移差异则无统计学意义(均P＞0.05).上、中、下3组纵隔淋巴结在同一方向上的位移差异和三维运动矢量差异均无统计学意义(均P＞O.05).在上下方向上,不同区域纵隔淋巴结位移与同侧膈肌位移无明显相关性(均P ＞0.05).结论 在自由呼吸状态下,NSCLC患者纵隔转移淋巴结分次内在同一方向上的位移大小与所在纵隔的区域无关；各区域纵隔转移淋巴结在三维方向上的位移均为上下方向大于左右和前后方向,而且这种差异在中、下纵隔区域淋巴结表现更为显著；在上下方向上,不同区域纵隔转移淋巴结的位移均与同侧膈肌位移无关,即不能以膈肌位移来预测或判断纵隔转移淋巴结的位移.%Objective To measure the intrafraction displacement of the mediastinal metastatic lymph nodes of non-small cell lung cancer (NSCLC) based on four-dimensional computed tomography (4D-CT),and to provide the basis for the internal margin of metastatic mediastinal lymph nodes.Methods Twenty-four NSCLC patients with mediastinal metastatic lymph nodes confirmed by contrast enhanced CT (short axis diameter ≥1 cm) were included in this study.4D-CT simulation was carried out during free breathing and 10 image sets were acquired.The mediastinal metastatic lymph nodes and the dome of ipsilateral diaphragma were separately delineated on the CT images of 10 phases of breath cycle,and the lymph nodes were grouped as the upper,middle and lower mediastinal groups depending on the mediastinal station.Then the displacements of the lymph nodes in the left-right,anterior-posterior,superior-inferior directions and the 3-dimensional vector were measured.The differences of displacement in three directions for the same group of metastatic lymph nodes and in the same direction for different groups of metastatic lymph nodes were compared.The correlation between the displacement of ipsilateral diaphragma and mediastinal lymph nodes was analyzed in superior-inferior direction.Results The displacements in left-right,anterior-posterior and superior-inferior directions were (2.24 ± 1.55) mm,(1.87± 0.92) mm and (3.28 ± 2.59) mm for the total (53) mediastinal lymph nodes,respectively.The vectors were (4.70 ± 2.66) mm,(3.87 ± 2.45)mm,(4.97 ± 2.75) mm and (5.23 ± 2.67) mm for the total,upper,middle and lower mediastinal lymph nodes,respectively.For the upper mediastinal lymph nodes,the displacements in left-right,anterorposterior and superior-inferior directions showed no significant difference between each other (P ＞ 0.05).For the middle mediastinal lymph nodes,the displacements merely in anterior-posterior and superior-inferior directions showed significant difference (P =0.005),while the displacements were not significantly different in the left-right and anterior-posterior,left-right and superior-inferior directions (P ＞ 0.05).The displacements of the total and the lower mediastinal lymph nodes in left-right and superior-inferior,or anterior-posterior and superior-inferior directions were significantly different (P ＜ 0.05),but was not significantly different in left-right and anterior-posterior directions (P ＞ 0.05).The displacements of different group of mediastinal lymph nodes in a single direction or vector showed no significant difference (P ＞0.05).In the superior-inferior direction,the correlation between the displacements of ipsilateral diaphragma and mediastinal lymph nodes were not statistically significant (P ＞0.05).Conclusions During free breathing,the differences between the intrafractional displacement of mediastinal metastatic lymph nodes in the same direction and its station were not statistically significant.The displacements of the total mediastinal metastatic lymph nodes in the superior-inferior direction were greater than that in the left-right and anterior-posterior directions,especially for the middle and lower mediastinal metastatic lymph nodes.There was no significant correlation between the displacements of ipsilateral diaphragma and the mediastinal metastatic lymph nodes in the superior-inferior direction,so it was unreasonable to estimate and predict the displacement of mediastinal metastatic lymph nodes by the displacement of ipsilateral diaphragma.
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