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

Abstract

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 performed 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 mediastinal 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)×10-3mm2/s, (0.670±0.179)×10-3mm2/s, (0.383±0.123)×10-3mm2/s, 0.422±0.119, (6.546±1.932) mm, respectively, and(1.897±0.657)×10-3mm2/s, (0.472±0.210)×10-3mm2/s, (0.354±0.130)×10-3mm2/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=1.890×10-3mm2/s(0.871, 92.7%, 80.0%); and D=0.648×10-3mm2/s(0.740, 70.0%, 84.1%). Conclusion IVIM is useful to distinguish 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. Key words: Intravoxel incoherent motion(IVIM) Lung cancer Mediastinal lymph nodes N-stage Aapparent diffusion coefficient(ADC) Diffusion coemcient(D)