| Object:Pancreatic cancer is a common malignant tumor of digestive system,its morbidity and mortality rate are increasing over the years.The symptoms of pancreatic cancer are not obvious in early stage.The diagnosis and treatment of pancreatic cancer are urgent problems to be solved.18F-FDG is the most common imaging agent for PET/CT,which can reflect the level of glucose metabolism of cells.Malignant tumors have higher glucose metabolism rate and uptake more FDG,therefore,PET can be used for the differential diagnosis of pancreatic lesions.Dual-phase PET/CT has showed an important significance in the diagnosis of pancreatic diseases.But the differential diagnostic standard for dual-phase 18F-FDG PET/CT has not yet achieved consensus.SUV has showed correlations with patient age,blood glucose,tumor pathological type,tumor size,cell differentiation,metastasis and prognosis,but conclusions are not consistent.In order to explore the differential diagnostic value of 18F-FDG PET/CT in pancreatic lesions and the relationship between clinical factors and SUV,RI,this subject is divided into two parts:the first part is to investigate the differential diagnostic value of dual-phase PET/CT for primary pancreatic lesions,looking for the optimum threshold of SUVeariy, SUV delay and RI;the second aspect aims to analyze the correlations between SUV, RI and tumor size,age,degree of cell differentiation,metastasis of primary pancreatic ductal adenocarcinoma cancer.Methods:122 cases with suspected pancreatic lesions tested from January 2009 to October 2015 underwent 18F-FDG PET/CT examination at Qilu hospital of Shandong university were analyzed retrospectively.68 cases had abdominal delayed imaging.All patients without operation,radiotherapy and chemotherapy before PET/CT examination,were confirmed by histological pathology or clinical follow-up.The primary benign pancreatic lesions in 41 cases(10 cases diagnosed by pathology,31 cases by diagnostic therapy and clinical follow-up),including pancreatic islet cell tumor was found in 2 cases,intraductal papillary mucinous neoplasm was found in 1 case,solid pseudopaillary neoplasm was found in 2 cases,autoimmune pancreatitis was found in 3 cases,cystadenoma was found in 6 cases,pancreatic endocrine tumor was found in 2 cases,chronic pancreatitis was found in 8 cases,acute pancreatitis was found in 3 cases,pancreatic pseudocyst was found in 13 cases,true cyst was found in 1 case;81 cases were malignant pancreatic lesions (26 cases by pathology,55 cases by diagnostic treatment and clinical follow-up),primary pancreatic ductal adenocarcinoma was found in 78 cases,mucinous cystadenocarcinoma was found in 3 cases.1.Outlined the region of interest(ROI)in the PET/CT imaging of 122 cases,and measured the maximum standard uptake value for early and delayed phase(SUVearly,SUVdeiay)and retention index(RI).SPSS17.0 statistical software was used for statistical analysis.Through Receiver Operating Characteristic(ROC) curve,the best cut-off point value of SUVearly,SUVdelay and RI were explored based on Youden index.X2-test was used to calculate the sensitivity,specificity and accuracy. T-test was used for the comparison of SUVearly,SUVdeiay and RI.2.78 cases of primary pancreatic ductal adenocarcinoma were divided into different groups according to age, tumor size, tumor cell differentiation and metastasis.SPSS17.0 statistical software was used for statistical analysis. T-test was used for the comparison between groups;Pearson and Spearman tests were used for correlation analysis.Results:1.18F-FDG PET/CT in differential diagnosis of primary pancreatic lesions(1)Comparison of SUVearly and SUVdelay between primary pancreatic benign and malignant lesionsSUVearly and SUVdelay of pancreatic malignant lesions were significantly higher than that of benign group(P<0.05).The difference between SUVearly and SUVdelay in the benign cases was not significant(P>0.05);while SUVjeiay was much higher than SUVearly in malignant cases(.P<0.05).(2)Diagnostic efficacy of SUVearly, SUVdelay and RI in primary pancreatic malignant lesionsThe areas under ROC curve of SUVearly,SUVdelay and RI were 0.853±0.034,0.780±0.059 and 0.753±0.072.The diagnostic efficacy of SUVearly was higher than SUVdelay and RI.The best cut-off values of SUVearly,SUVdelay and RI were2.75,3.85 and 12.00%,the Youden index were 0.632,0.514 and 0.553.The sensitivities of SUVearly,SUVdelay and RI were 82.72%,69.57% and 82.61%;the specificities were 80.49%,81.82%,72.72%;the accuracies were 81.97%、73.53% and 79.41% respectively.(3)Diagnostic efficacy of SUV combined with RI in primary pancreatic malignant lesionsUsing the parallel tests,When SUVearly=2.75 joined with RI=12.00%,the sensitivity,specificity and accuracy were 93.48%-59.09% and 82.35%.When SUVdelay=3.85 joined with RI=12.00%,the sensitivity,specificity and accuracy were 91.30%、68.18% and 83.82%.When SUVearly=2.75 joined with SUVdelay=3.85,the sensitivity,specificity and accuracy were 73.91%、68.18% and 72.06%.2.The relationship between SUV, RI and clinical factors of primary pancreatic ductal adenocarcinoma(1)The relationship between tumor size and SUV,RISUVearly and tumor maximum diameter had a positive correlation in pancreatic ductal adenocarcinoma(r=0.252, P=0.035).The difference between SUVearLy in different tumor size groups(≤ 3cm vs>3cm) was statistically significant (t=-2.538, P=0.014).SUVdelay and the maximum diameter also had positively correlation,but there was no statistical significance (r=0.250, P=0.129).RI and the maximum diameter showed no statistical correlation(r=-0.206, P=0.214).(2)The relationship between age and SUV,RIand SUVdelay were positively correlated with age in pancreatic ductal adenocarcinoma(r=0.261, P=0.021; r=0.437, P=0.003).SUVearly and SUVdelay were significantly different in two age groups (≤62.5 years old vs>62.5 years old;t=-2.073, P= 0.042;t=-2.766, P=0.010).RI and the maximum diameter of the lesions showed no statistical correlation (r=-0.044, P=0.780).(3)The relationship between cell differentiation and SUV,RISUVearly,SUVdelay and the differentiation of the tumor cells showed a strong negative correlation in pancreatic ductal adenocarcinoma (r=-0.824,P=0.000;r=-0.743,P= 0.006).There was no statistical correlation between RI and tumor differentiation(r=0.201 P=0.531).SUVearly and RI in poorly differentiated group were significantly greater than moderately differentiated group (t=2.245, P= 0.041;t=3.130, P=0.020);SUVearly and SUVdelay in moderately differentiated group were greater than well differentiated group,but the difference wasn’t statistically significant (t=2.200, P=0.059;t=1.291,P=0.238).(4)The comparison between metastasis and SUV,RI of pancreatic ductal adenocarcinomaSUVearly and SUVdelay of metastasis group were higher than that of non metastasis group (t=3.012, P=0.004;t=3.254, P=0.002);but there was no significant difference of RI between the two groups(t=-1.266,P=0.230).Conclusion:1.18F-FDG PET/CT plays an important role in the diagnosis of primary pancreatic lesions,delayed imaging has a supplementary significance in diagnosis of pancreatic lesions.2.The best cut-off value of SUVearly is 2.75,SUVdelay 3.85 and RI 12.00% respectively.3.The combination of SUV and RI is helpful to improve the diagnostic efficiency of PET/CT in primary pancreatic lesions.4.SUVearly and SUVdelay have positive correlations with age in pancreatic ductal adenocarcinoma.The older patient is,the higher SUVearly and SUVdelay the tumor has.5.SUVearly has a positive correlation with tumor size in pancreatic ductal adenocarcinoma.The larger tumor is more likely to have the higher6.There are strong negative correlations between SUVearly,SUVdelay and the differentiation of pancreatic tumor cells.The pancreatic lesion with higher SUVearly and SUVdelay is more likely to be the poorly differentiation.7.The higher SUVearly and SUVdelay pancreatic ductal adenocarcinoma has,the larger possibility of lymph node or organ metastases occurs. |
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