The Diagnostic Value Of Diffusion-weighted Imaging Based On Monoexponential And Biexponential Model In Metastatic Cervical Lymph Nodes Of Nasopharyngeal Carcinoma

Objective To investigate the diagnostic value of diffusion weighted imaging based on monoexponential and biexponential model in metastatic cervical lymph nodes of nasopharyngeal carcinoma.Methods Conventional MRI,DWI and IVIM-DWI scans were performed in 40 patients with histopathologically proven nasopharyngeal carcinoma and 25 healthy volunteers with GE 3.0T MRI. The long /short diameter ratio(L/S), Lymph nodes/muscle signal intensity ratio( SLN/M) in STIR of which large metastatic cervical lymph nodes group, small metastatic cervical lymph nodes group and benign cervical lymph nodes group were analysed.The ADC, D, D*and f value were measured accurately and compared. Receiver operating characteristic curve was performed to analysis and compare the ability of the ADC, D, D*and f value for the differential diagnosis small metastatic lymph nodes and benign lymph nodes. The statistical process of the datas were analyzed with SPSS 19.0 software. P<0.05 was considered statistically significant.Results Totally 101 metastatic lymph nodes of nasopharyngeal carcinoma accorded with the inclusion criteria, of which 55 large metastatic lymph nodes, 46 metastatic small lymph nodes. 62 benign lymph nodes met the inclusion criteria.There was significant differences among large metastatic lymph nodes group, small metastatic lymph nodes group and benign lymph nodes group in L/S(F=8.031,P=0.000), and there was no statistical difference among the three groups in SLN/M(F=0.677,P=0.513). Further comparison between two, the L/S of large metastatic lymph nodes group was less than that of small metastatic lymph nodes group and benign lymph nodes group(P<0.05), and no statistical significance existed between small metastatic lymph nodes group and benign lymph nodes group(P>0.05).There were significant differences in ADC value( F=18.456,P=0.000), D value(F=22.173,P=0.000), D* value(F=7.186,P=0.002)and there was no significant differences in f value(F=1.765, P=0.179)among large metastatic lymph nodes group, small metastatic lymph nodes group and benign lymph nodes group. Further pairwise comparison, D and ADC value were significantly lower in large metastatic lymph nodes group and small metastatic lymph nodes group than in benign lymph nodes group(P<0.05), whereas D* was significantly higher(P<0.05). There were no significant differences in ADC value, D value, D* value between large metastatic lymph nodes group and small metastatic lymph nodes group( P >0.05).D value was less than the ADC value in three groups(P<0.05). The AUC of ADC value, D value, D* value for the differential diagnosis of Small metastatic lymph nodes and benign lymph nodes were 0.893、0.934、0.752 respectively. The AUC of D value was the biggest. The optimal cut-off value of ADC value, D value, D* value for the differential diagnosis of small metastatic lymph nodes and benign lymph nodes were 0.910×10-3mm/s2、0.717×10-3mm/s2、22.350×10-3mm/s2. The sensitivity of ADC value, D value and D* value were 80.8%、88.5%、73.1%, and the specificity were 87.5%、91.7%、66.7%.Conclusions 1. Conventional MRI has some limitations in diagnosing Small metastatic lymph nodes of nasopharyngeal carcinoma.2. Both ADC obtained with monoexponential model and D, D* obtained with biexponential model can help to differentiate benign and metastatic lymph nodes in nasopharyngeal carcinoma patients.3. D obtained with biexponential model demonstrates the highest diagnostic efficacy in Small metastatic lymph nodes of nasopharyngeal carcinoma.