| BackgroundAt present,there are still difficulties in the detection of suspected recurrence or metastasis in the patients with thyroid papillary carcinoma(PTC)after operation.Conventional computed tomographic(CT)and MRI are difficult to characterize metastatic lymph nodes.Meanwhile,ultrasonography is limited to superficial lymph nodes with high specificity but low sensitivity.Therefore more accurate techniques are needed in the diagnosis of cervical lymph node metastasis.PurposeThis study aims to quantitatively assess the diagnostic performance of 18F-fluorodeoxyglucose-positron emission tomography/computed tomography(18FDG-PET/CT),diffusion-weighted imaging(DWI)with background body signal suppression(DWIBS)and other morphological indexes for cervical lymph nodes(LN)metastasis in the patients with papillary thyroid cancer(PTC).MethodsThe postoperative patients with thyroid papillary carcinoma who received multidisciplinary consultation in our hospital from November 2018 to November 2019 were collected.18F-FDG-PET/CT examination,DWIBS sequence scan and routine MRI scan were performed before reoperation.The target lymph nodes were selected after multidisciplinary consultation and the inclusion and exclusion criteria were strictly established.The ADCmean and SUVmax values of the whole target lymph nodes were measured.The circle index was calculated by the maximum long diameter and maximum short diameter of the target lymph nodes which were measured at the maximum level.The pathological results after reoperation was regarded as the gold standard.The relationship between these parameters and lymph node metastasis was analyzed by single factor using two independent samples t-test,Mann-Whitney U test or chi-square test.ROC curve analysis was used to confirm the cut off value and evaluate the diagnostic efficiency of each parameter.Pearson was used to analyze the correlation between the parameters which were normal,and Spearman was used to analyze the correlation between parameters which were non-normal.Multiple factor analysis using Logistic regression analysis.ResultsIn this study,a total of 60 postoperative patients with papillary thyroid carcinoma met the inclusion criteria.A number of 115 lymph nodes were successfully matched and labeled during surgery,including 61 metastatic lymph nodes and 54 non-metastatic lymph nodes.(1)Result of single factor analysis:The ADCmax and roundness index of metastatic lymph nodes were lower than those of non-metastatic lymph nodes,the difference was statistically significant(P<0.0001);the SUVmax and short diameter of metastatic lymph nodes were larger than those of non-metastatic lymph nodes,and the difference was statistically significant(P<0.0001);the long diameter of metastatic lymph nodes was larger than that of non-metastatic lymph nodes,but the difference was not statistically significant(P=0.782).The cut off value of lymph node ADCmean is 0.974×10-3 mm2/s,(AUC is 0.949,sensitivity is 95.08%,specificity is 90.74%,and specificity is 90.74%,P<0.0001).The cut off value of lymph node SUVmax is 2.622(AUC is 0.883,sensitivity is 90.16%,specificity is 81.48%,P<0.0001).And the cut off value of roundness index is 1.819(AUC is 0.910,sensitivity is 95.08%,specificity is 81.48%,P<0.0001).The cut off value of the maximum short diameter is 0.45cm(AUC is 0.774,sensitivity is 90.16%,specificity is 51.85%,P<0.0001).In addition to the long diameter,there is a correlation between every other two parameters,while there is only a positive correlation between the long diameter and the short diameter.(2)Result of multiple factor analysis:The parameters which was statistical significance in single factor analysis were analyzed by Logistic regression analysis.According to cut off point obtained by the ROC curve,the lymph nodes were divided into high risk group(ADCmean≤0.974×10-3 mm 2/s,roundness index≤1.819)and low risk group(ADCmean>0.974×10-3 mm 2/s,roundness index>1.819).The only variables included in the equation were ADCmean and roundness index.The coefficients of the equation are-2.259(P=0.003)and-3.573(P=0.008),OR>0(95%confidence interval is 0.000～0.001)and OR=0.028(95%confidence interval is 0.002-0.393),respectively.ConclusionsADCmean and roundness index of lymph node are independent risk factors of cervical lymph node metastasis in postoperative patients with papillary thyroid carcinoma,which are more accurate than SUVmax,short diameter and long diameter.They play a certain qualitative role in the diagnosis of cervical lymph node metastasis,providing a basis for the selection of treatment and surgical methods. |
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