Enhancing Fraction in Glioma and Its Relationship to the Tumoral Vascular Microenvironment: A Dynamic Contrast-Enhanced MR Imaging Study

BACKGROUND AND PURPOSE: EnF is a newly described measure of proportional tumor enhancement derived from DCE-MR imaging. The aim of this study was to assess the relationship between EnF and the more established DCE-MR imaging parameters: K trans , v e , and v p . MATERIALS AND METHODS: Forty-two patients with 43 gliomas (16 grade II, 3 grade III, and 24 grade IV) were studied. Imaging included pre- and postcontrast T1-weighted sequences through the lesion and T1-weighted DCE-MR imaging. Parametric maps of EnF, K trans , v e , and v p were generated. Voxels were classified as enhancing if the IAUC was positive (EnF IAUC 60>0 ). A threshold of IAUC > 2.5 mmol.s was used to generate EnF IAUC 60>2.5 . Both measures of EnF were compared with the DCE-MR imaging parameters ( K trans , v e , and v p ). RESULTS: In grade II gliomas, EnF IAUC60>0 and EnF IAUC60>2.5 correlated with v p ( R 2 = 0.6245, P R 2 = 0.4727, P = .003) but not with K trans or v e . In grade IV tumors, both EnF IAUC60>0 and EnF IAUC60>2.5 correlated with K trans ( R 2 = 0.3501, P = .001; and R 2 = 0.4699, P v p ( R 2 = 0.1564, P = .01; and R 2 = 0.2429, P = .007), but not with v e . Multiple regression analysis showed K trans as the only independent correlate of both EnF IAUC60>0 and EnF IAUC60>2.5 for grade IV tumors. CONCLUSIONS: This study suggests that in grade II tumors, EnF reflects v p and varies due to changes in vascular density. In grade IV gliomas, EnF is affected by K trans with secondary associated changes in v p .