FIG 2. Representative CBV maps from (A) a grade II fibrillary astrocytoma, (B) a grade III anaplastic astrocytoma, and (C) a grade IV glioblastoma multiforme. The white boxes enclose the tumor area in each image. The normal cerebral vasculature is clearly seen on these maps, particularly the superior sagittal sinus and other major vessels. The grade II tumor in panel A homogeneously shows very low blood volume, which is below the measurement accuracy of the technique. The necrotic core is clearly evident in the middle of the tumor in panel C. The heterogeneity of CBV is clearly evident in the enhancing tumor portion in panels B and C and shows very different distributions to those in Fig 1 (A and B).