Intravoxel Incoherent Diffusion-weighted Imaging In Evaluating The Clinical Value Of Pancreatic Ductal Adenocarcinoma

Clinical value of intravoxel incoherent diffusion weighted imaging in pancreatic ductal adenocarcinomaPartⅠObjectives:To explore the differences between intravoxel incoherent motion-diffusion weighted imaging（IVIM-DWI）and diffusion weighted imaging（DWI）in evaluation of the histopathological characters of PDAC.Methods:This retrospective study enrolled 50 patients with PDAC confirmed by pathology from December 2018 to May 2020.All patients underwent DWI and IVIM-DWI before operations.Patients were classified into low and high fibrosis group.Apparent diffusion coefficient（ADC）,diffusion coefficient（D）,false diffusion coefficient（D^*）,and perfusion fraction（f）were measured by two radiologists respectively.The tumor tissue was stained with sirius red,CD34,and CK19 in order to evaluate fibrosis,microvascular density（MVD）,and tumor cell density.Furthermore,ADC,D,D^*,and f values were compared with histopathological results.Results:The D values were lower in the high fibrosis group（1.26±0.16μm²/ms）than in the low fibrosis group（1.36±0.18μm²/ms）while the f values were opposite[（18.80±4.98）%vs（13.03±6.22）%].Further,no statistically significant differences were found in ADC and D^*values between the high and low fibrosis groups.The AUC of D and f values was 0.69 and 0.74,respectively,which had high evaluation efficacy in the high and low fibrosis groups.A significant negative correlation between D values and fibrosis（r=-0.35,P=0.01）and a significant positive correlation between f values and fibrosis were observed（r=0.42,P=0.01）.Conclusions:D and f values derived from the IVIM model had higher sensitivity and diagnostic performance for grading fibrosis in PDAC compared with the conventional DWI model.IVIM-DWI could serve as an imaging biomarker for predicting the fibrosis grade of PDAC.PartⅡPurpose:To investigate the value of evaluating the resectability of pancreatic ductal adenocarcinoma（PDAC）before surgery by intravoxel incoherent motion diffusion weighted imaging（IVIM-DWI）.Methods:The clinical and imaging data of 39 cases of pancreatic ductal adenocarcinoma diagnosed pathologically from November 2018 to September 2019were analyzed retrospectively.The D^*,D,f values of the ROIs of tumor and normal tissue were measured by GE post-processing.Interobserver reliability was assessed with intraclass correlation coefficient（ICC）.Mann-Whitney U-test was used to compare the differences of parameters between the resectable and unresectable pancreatic ductal adenocarcinoma.The counting data were compared between groups byχ²test.The binary Logistic regression analysis was conducted with the statistical characteristics as the independent variable,resectability as the factor variable,established the regression model,and used the subject working feature（ROC）curve to evaluate the efficiency.Significance threshold was set as P<0.05.Results:The D,D^*and f values of resectable pancreatic ductal adenocarcinoma were（1.66±0.39）×10^-3mm²/s,（1.91±2.29）×10^-2mm²/s,35.2±15.6%,respectively,and the D,D^*and f values of unresectable PDAC were（1.30±0.33）×10^-3mm²/s,（1.14±1.82）×10^-2mm²/s,21.3±10.2%.D value and f values between resectable and unresectable PDAC were statistically significant（P<0.05）.The measurement of each parameter value has good repeatability（ICC>0.75,P<0.001）.The lesion diameter,lesion morphology,boundary,vascular invasion,or distant metastatic images were statistically different between resectable and unresectable PDAC.Logistic regression showed that lesion diameter and f values were independent imaging factors of resectability.The area under the curve of regression model was 0.921.The sensitivity of predicting resectability of pancreatic ductal adenocarcinoma was 100%when P value>0.482,and the specificity was 90%.Conclusion:The IVIM-DWI quantitative parameter D,f values help to predict resectability of PDAC,especially the regression models can achieve higher diagnostic efficacy.