FIG 4. A–C, Correlation between fBV (A), k^PS (B), and total permeability, k, (C) and histologically determined tumor grade. While the data points in A are very scattered, reflective of a weak correlation (r = .39) between fBV and tumor grade, the slope is nonetheless positive, suggesting a tendency toward increased fBV in higher-grade tumors. For k^PS, the tendency is more pronounced, with reduced scatter (r = .76). In comparison, total permeability, k, yielded a similar correlation (r = .83), with a steeper slope and less overlap between tumor grade groups.