Abstract: Objective: To explore the value of the volume transfer constant(Ktrans) and volume fraction of extravascular extracellular space(Ve) of dynamic contrast enhanced MRI(DCE-MRI) in evaluating the microvascular permeability of glioma,and correlation of the Ktrans and Ve values and pathological grade of tumor.Methods: The values of Ktrans and Ve of DCE-MRI in 26 patients with glioma(including grade Ⅱin 12 cases,grade Ⅲ in 8 cases and grade Ⅳ in 6 cases) diagnosed by pathology after operation were obtained before operation.The differences of the values of Ktrans and Ve in different grades gliom were compared using One-way AVOVA.Pearson correlation analyses were used to determine relationship between Ktrans,Ve,and glioma grade.Receiver operating characteristic curve analyses were performed to determine the threshold of Ktrans and Ve to distinguish different grades of gliomas.Results: The values of Ktrans and Ve in grade Ⅱ were significantly lower than those in grade Ⅲ or grade Ⅳ gliom(P<0.01),the differences of whose between grade Ⅲ and Ⅳ glioms were not statistically significant(P>0.05).The thresholds of Ktrans and Ve for 0.054/min & 0.296 and 0.084/min & 0.345 could distinguish grade Ⅱ from Ⅲ and Ⅱ from Ⅳ glioma,respectively.The values of Ktrans and Ve and glioma grade,and Ktrans and Ve were positive correlations(P<0.01).Conclusions: DCE-MRI can be used to distinguish grade Ⅱ from Ⅳ glioma and grade Ⅱ from Ⅲ glioma by testing the microvascular permeability of tumor,which can provide the important information for clinical diagnosis.