Fig 2. A and B, Postcontrast T1-weighted (TR/TE, 3059/6.35 ms) axial image (A) and base image from perfusion CT study (B) in 32-year-old woman with WHO grade II astrocytoma showing a nonenhancing right frontal tumor with no surrounding perilesional edema. C and D, PS (C) and CBV (D) perfusion CT maps showing low permeability (PS = 0.7 mL/100 g per minute) and low blood volume (CBV = 1.01 mL/100 g) within the tumor.