Comparison Of Conventional MRI,DWI,and DSC-PWI Between Low-grade And Anaplastic Intracranial Extraventricular Ependymoma

Objective:To investigate and compare conventional MRI,diffusion-weighted imaging（DWI）and dynamic susceptibility contrast-enhanced perfusion-weighted imaging（DSC-PWI）features of low-grade（WHO grade II）and anaplastic（WHO grade III）extraventricular ependymomas,and to improve the accuracy of preoperative diagnosis and grade stratification of these entities.Materials and Methods:We reviewed 26 patients（7 patients with low-grade extraventricular ependymomas and 19 patients with anaplastic extraventricular ependymomas）who underwent preoperative MR imaging confirmed by pathology between October 2009 and February 2019 in this retrospective study.Conventional MRI and DWI were performed in all patients;and DSC-PWI was performed in 15 patients（11 with anaplastic ependymoma and 4 with low-grade ependymoma）.Demographics（sex and age）,conventional imaging characteristics（location,side,size,peritumoral edema,necrotic and cystic degeneration,enhancement,pial and cortical involvement,ependymal extension,and deep white matter invasion）,minimum relative apparent diffusion coefficient ratio(r ADC_min),and maximum relative cerebral blood volume ratio(r CBV_max)were compared between the low-grade ependymoma and anaplastic groups.All quantitative data were compared by Student’s t test or Mann-Whitney U test between groups.All categorical variables were compared by Fisher’s exact test.The diagnostic performance with optimal cutoff values was determined by receiver operating characteristic（ROC）curves and multivariate logistic regression analysis.Interobserver variabilities of conventional MRI features were evaluated by Kappa statistics.Results:Low-grade extraventricular ependymomas commonly located in the peri-trigonum of lateral ventricle（P=0.001）with ependymal extension（P=0.005）,while anaplastic extraventricular ependymomas were more likely to locate in superficial supratentorial cerebral hemisphere（P=0.026）,present with pial and cortical involvement（P=0.028 and 0.013,respectively）,and necrotic degeneration（P=0.014）.The r ADC_minvalue was significantly lower in anaplastic ependymoma than in low-grade ependymoma（0.8±0.2 versus 1.2±0.3,P=0.002）.The r CBV_max value was significantly higher in anaplastic ependymoma than in low-grade ependymoma（15.7±5.3 versus 9.0±4.4,P=0.042）.The cutoff values in grading extraventricular ependymoma were 1.02 for r ADC_min,and 10.43 for r CBV_max,respectively.Combination of conventional MRI,DWI and DSC-PWI can achieve the best discriminative ability with the area under the curve（AUC）of 1.00.Conclusions:Conventional MRI,DWI,and DSC-PWI techniques may aid in improving the accuracy of preoperative diagnosis and grade stratification of extraventricular ependymomas.