Value Of Diffusion-weighted Imaging And Apparent Diffusion Coefficient In Differential Diagnosis Of Cervical Lymph Node Lesions At3.0T MRI

Objective To investigate the value of the diffusion-Weighted imaging（DWI） and apparent diffusion coeffient（ADC） values indifferential diagnosis of cervical lymph node lesions by applying a rage of bvalues，and try to find an optimal b value of DWI at3.T MRI for cervicallymph nodes.Materials and Methods Conventional MR imaging was performed in46patients with histologically proven by using GE3.0T scanner,28cases ofmalignant（20cases were metastatic nodes,8cases were lymphoma）,18caseswere benign lymph nodes（12cases were inflammatory swell-ing,6cases weretuberculosis）. The lesion detectability of T1WI,T2WI and DWI,Themorphology manifestation of the lesions were observed.ADC values weremeasured in the lymph node lesions.The b-value of DWI was0,20,50,100,200,400,600,1000,1500,2000s/mm²respectively.The SNR、ADC and the discrepancy of ADCvalues of the nodes were measured and compared at different bvalues,analyze the correlation between the b-value and ADC or SNR of eachimage,to determine an optimal b value.The optimal ADC threshold was determined by means of receiver operating characteristic（ROC） curve todifferentiate between the malignant and benign lymph nodes.Results1.Benign and malignant lymph nodes appeared iso-signalintensity on T1WI and high signal intensity on T2WI,compared with adjacentmuscle.On the DWI,all the lymph nodes were homogeneous high signalintensity.The differences of L、S、L/S and SLN/Mbetween the two groups werenot statistically significant（p>0.05）.2.When b-value≤1000s/㎜2，the SNR ofDWI increased as the b-value increased,and when b-value=1000s/㎜2theSNR reached its climax,when b-value>1000s/㎜2，the SNR of DWI decreasedas the b-value increased.3.The differences in mean ADC of Group malignantlymph nodes [（0.83±0.19）×10^-3mm²/s] and Group benign lymph nodes[1.57±0.27)×10^-3mm²/s] were statistically significant（p<0.05）.The ADCvalue of malignant lymph nodes was inferior to the begign lymph nodes,andthe difference was significant （p<0.05）.There were no statistically significantbetween metastatic nodes and lymphoma nodes （p>0.05）, inflammatoryswell-ing and tuberculosis（p>0.05）.4.The ADC value of begign and malignantlymph nodes decreased as the b-value increased,the maximum difference inADC between begign and malignant lymph nodes was observed when theb-value was1000s/㎜2.5.By means of ROC curve analyzing,the threshold ofADC within malignant and begign lymph nodes were contributory todifferentiate them,especially with b value of1000s/㎜2.The optimal threshold values of ADC was1.13,the Youden index was maximam,and its sensibilityand specifeicity was87.7%and81.4%respectively.Conclusions1.Routine MRI examination is limited to differentiatemalignant and benign lymph nodes through morphology criteria,includingsiza,shape,margin.2.For good image quality and valid differentiation betweenmalignant and begign lymph nodes,the optimized b value of DWI at3.0T forcervical lymph nodes was1000s/㎜2.3.ADC value acquired from DWI canhelp to differentiate malignant and benign lymph nodes with high differentialdiagnostic efficacy.