磁共振体素内不相干运动成像技术（IVIM）在肺癌术前判断纵隔淋巴结转移的作用初探

A Preliminary exploration of the intravoxel incoherent motion applied in the preoperative mediastinal lymph node metastasis of lung cancer

目的探讨磁共振体素内不相干运动成像技术（IVIM）在肺癌术前纵隔淋巴结转移的诊断价值，以期提高术前N分期的准确性，为患者选择最适合的治疗手段。方法研究纳入了2015年10月至2016年6月在首都医科大学附属北京朝阳医院胸外科接受手术治疗的66例肺癌患者。所有患者均未行术前新辅助放化疗、免疫治疗及相关靶向治疗，术前完善了包括胸部磁共振扫描在内的全部辅助检查。测量MRI纵隔淋巴结的短径及IVIM相关参数，包括表观扩散系数（apparent diffusion coefficient，ADC）、扩散系数（diffusion coefficient，D）、伪扩散系数（pseudo-diffusion coefficient，D＊）和灌注分数（perfusion fraction，f）。手术方式为肺叶切除或肺楔形切除，系统淋巴结清扫或采样。根据术后病理结果，统计分析转移淋巴结与非转移淋巴结的IVIM参数，绘制ROC曲线并找出诊断的最佳界值。其中42例比较了胸部CT和MRI判断纵隔淋巴结转移的临床价值。结果研究中MRI共测量184组纵隔淋巴结，其中164组无转移，20组有转移。非转移性淋巴结组的ADC及D值明显高于转移性淋巴结组（2．880±0．785）×10^-3mm^2／s对（1．897±0．657）×10^-3mm^2／s和（0．670±0．210）×10^-3mm^2／s对（0．472±0．179）×10^-3mm^2／s；P〈0．01）。两组D＊、f及淋巴结短径差异无统计学意义，三者分别为（0．383±0．123）×10^-3mm^2／s对（0．354±0．130）×10^-3mm^2／s、（0．422±0．119）对（0．412±0．090）和（6．546±1．932）mm对（7．510±2．773）mm。绘制ADC的ROC曲线：曲线下面积（AUC）为0．871，最佳诊断界值为1．890×10^-3mm^2／s，诊断敏感性92．7％，特异性80．0％；D的ROC曲线：曲线下面积（AUC）为0．740，最佳诊断界值为0．648×10^-3mm^2／s，诊断敏感性70．0％，特异性84．1％。结论IVIM扫描序列有助于肺癌术前纵隔淋巴结分期，其中ADC和D更为敏感，可用于术前纵隔淋巴结转移的诊断。

Objective The aim of this study was to investigate the diagnostic value of the intravoxel incoherent motion （IVIM） for discriminating nonmetastatic from metastatic mediastinal lymph nodes in lung cancer. Methods IVIM was per- formed preoperatively on 66 patients with lung cancer during October 2015 to June 2016 in Capital Medical University Affiliated Beijing Chaoyang Hospital. Preoperative examination including the chest MRI scan, chest CT, head MRI, bone scan-ning and the cardiopulmonary function. None of the patients was undergone any kind of treatment about the cancer before the examinations, the neoadjuvant chemotherapy or radiation therapy, immunotherapy and gene targeted therapy were included. Measured the short axis diameter and the IVIM parameters of the mediastinal lymph nodes, apparent diffusion coefficient（ ADC）, diffusion coefficient（ D）, pseudo-diffusion coefficient（ D ＊ ）, and perfusion fraction（f）. All the patients underwent the lobectomy or wedge resection and lymph node dissection or systematic sampling. By comparing the IVIM parameters of the nonmetastatic and metastatic mediastinal lymph nodes according to the pathological examination, draw the ROC curves to find the best cutoff value for diagnosis. And 42 cases were used to comparing the value of the MRI and CT in differential diagnosis. Results MRI measured 184 groups mediastiual lymph nodes, including 164 groups without metastasis, 20 groups with metastasis. The ADC, D, D ＊ , f values and short axis diameter of the nonmetastatic lymph nodes （ n = 164 ） were （2. 880 ± 0. 785 ）×10^-3mm^2/s,（0. 670 ±0. 179）×10^-3mm^2/s, （0. 383 ±0. 123）×10^-3mm^2/s, 0. 422 ±0. 119, （6. 546 ± 1. 932） mm, respectively, and （ 1,897±0. 657 ） ×10^-3mm^2/s, （0. 472 ±0.210 ） ×10^-3mm^2/s, （0. 354± 0. 130） ×10^-3mm^2/s, 0. 412 ± 0. 090, （7.510 ±2. 773 ）mm respectively for the metastatic lymph nodes （ n = 20）. The ADC and D value of the nonmetastatic lymph nodes were significantly higher than the metastatic lymph nodes （ P 〈 0.01 ）. While the other parameters （ D ＊ , f, and short axis diameter ） between the two groups did not show significantly different. Optimal cutoff values （ area under the curve, sensitivity, and specificity） for distinguishing metastatic from nonmetastatic lymph nodes were as follows： ADC = 1. 890 ×10^-3mm^2/s （0.871, 92.7%, 80.0%）; and D=0.648 ×10^-3mm^2/s（0.740, 70.0%, 84.1%）. Conclusion IVIM is useful to dis- tinguish metastatic from nonmetastatic lymph nodes in lung cancer. The ADC and the D values are significant higher in metastatic lymph nodes, which more sensitive than the other parameters（ D ＊ , f, and short axis diameter）. As a result, IVIM can be used in the N-stage diagnosis of lung cancer.