Candidate Biomarkers of Extravascular Extracellular Space: A Direct Comparison of Apparent Diffusion Coefficient and Dynamic Contrast-Enhanced MR Imaging—Derived Measurement of the Volume of the Extravascular Extracellular Space in Glioblastoma Multiforme

BACKGROUND AND PURPOSE: ADC measurements have been shown to have an inverse relationship with tumor cell density. DCE-MR imaging modeling techniques can produce a measurement of the v_e, which would also be expected to have an inverse relationship with cell density. The objective of this study was to test the hypothesis that areas of increased cellularity, and therefore low ADC, would be expected to have a small EES (low v_e).

MATERIALS AND METHODS: Nineteen patients with GBM were recruited. All imaging was performed before surgery on a 3T MR imaging scanner. Imaging included diffusion tensor imaging, T1-weighted DCE-MR imaging, and anatomic sequences. Tumor VOIs were defined on the anatomic images and modified to contain only enhancing voxels. Parametric maps of ADC and v_e were generated. Statistical analysis of ADC and v_e was performed on both a voxel-by-voxel basis and comparison of median values.

RESULTS: No correlation was demonstrated between ADC and v_e in either a voxel-by-voxel analysis or comparison of median values (P = .124).

CONCLUSIONS: This study failed to demonstrate a correlation between ADC and v_e. This is important because it suggests that though the mechanisms underlying these parameters are theoretically similar, they actually reflect different aspects of tumor microenvironment. Consequently ADC and v_e should be considered to provide independent information about the properties of the EES.