Objective:To investigate the value of enhanced MRI in evaluating the tissue permeability of pancreatic ductal adenocarcinoma (PDAC) animal model.Methods:The experimental animals were 27 female C57BL/6 mice. The mice were divided into 3 groups with 9 mice in each group by random number method. Murine pancreatic adenocarcinoma (Panc02) and embryonic fibroblasts (NIH/3T3) were implanted subcutaneously at the ratio of 2∶1 and 1∶1 to establish PDAC models with different tissue permeability, which were low fibroblast group and high fibroblast group, respectively, and simple Panc02 implantation model was control group. The positive expression rate of α-smooth muscle actin (α-SMA), the positive expression rate of fibroblast activating protein (FAP), the coverage rate of collagen fibers, number of blood vessels and the long/short diameter of tissue vessels were quantitatively evaluated by tissue staining, and the tissue permeation efficiency was quantified by the average optical density (AOD) of tissue sections stained by Evans blue (EB). Enhanced MRI was performed on mice, and the enhancement degree and the enhancement rate of 20 min were obtained. One-way ANOVA was used to compare the overall differences of tumor histological indexes and MRI enhancement parameters in each group, and the correlation between the indexes was analyzed by Pearson correlation analysis. Multiple linear stepwise regression analysis was conducted with 20 min enhancement rate as dependent variable, while α-SMA positive expression rate, collagen fiber coverage rate and vascular long/short diameter as independent variables.Results:There were significant differences in AOD value, α-SMA positive expression rate, FAP positive expression rate, collagen fiber coverage rate, vascular long/short diameter, 20 min enhancement degree and 20 min enhancement rate among the three groups ( P<0.001), but there was no significant difference in the number of blood vessels ( P=0.650). The AOD value was negatively correlated with the positive expression rate of α-SMA, the coverage rate of collagen fibers and the long/short diameter of blood vessels in PDAC model, respectively ( r=-0.888, P=0.001; r=-0.813, P=0.008; r=-0.915, P<0.001). The 20 min enhancement degree was positively correlated with AOD value ( r=0.954, P<0.001). The positive expression rate of α-SMA, collagen fiber coverage and vascular long/short diameter were negatively correlated with 20 min enhancement rate ( r=-0.901, P<0.001; r=-0.837, P=0.005; r=-0.880, P=0.002). The results of multiple linear stepwise regression analysis showed that the positive expression rate of α-SMA was an important influencing factor for the 20 min enhancement rate (R 2=0.813, P=0.001). Conclusions:The increase of fibroblast implantation ratio significantly decreased the permeation efficiency of tumor tissue. The positive expression rate of α-SMA, the coverage rate of collagen fibers and the long/short diameter of blood vessels were negatively correlated with the permeation efficiency of tumor tissue. The 20 min enhancement degree was positively correlated with tissue permeation efficiency.