Figure 3. Trans-axial images from a patient with an anaplastic astrocytoma, acquired on day 0 (top) and day 2 (bottom). (a) T₁ weighted images in a contrast enhanced dynamic series 41 s after contrast agent (CA) bolus injection, approximately at the beginning of first recirculation of the CA bolus to the sagittal sinus. (b) Colour rendered volume transfer constant between blood plasma and interstitial tissue (k_fp) maps. Dark blue, k_fp=0-0.05 min^-1; green, k_fp 0.05-0.10 min^-1; red, k_fp 0.10–0.17 min^-1; yellow, k_fp 0.17–0.25 min^-1. (c) Normalized relative cerebral blood volume calculated from T₁ weighted dynamic images and corrected for contamination by CA leakage () (equal to , where C_p(t) is the plasma CA concentration–time course curve and was measured from superior sagittal sinus). Dark blue, normalized ; green, normalized ; red, normalized ; yellow, normalized . (d) Relative cerebral blood volume calculated from T₂* weighted images (rCBV^T₂) maps. Dark blue, rCBV^T₂=0-1.9 A.U.; green, rCBV^T₂=1.9-2.3 A.U.; red, rCBV^T₂=2.3-4.1 A.U.; yellow, rCBV^T₂=4.1-6.5 A.U. A.U. is a unit of normalized rafe of change of Iq* (R2*). rCBV^T₂=R2*(t)/R2*_{normal brain}(t), where R2*_{normal brain}(t) was measured from the hemisphere contralateral to the tumour, excluding cerebrospinal fluid. (a) There is marked enhancement of the astrocytoma (arrow) and blood vessels (arrowheads) and choroid plexus. The tumour and choroid plexus are best distinguished in the permeability maps (b) owing to high k_fp values. Since normal brain tissue with intact brain–blood barrier is not permeable to gadodiamide, both normal brain tissue and blood vessels have low k_fp values. Large blood vessels are clearly depicted on the blood volume maps (c). On the normalized maps, the grade III glioma shows heterogeneous increases of blood volume (yellow, red and green representing tumour blood volume ranging from 0.06 to 0.14). Maps of (c) and (d) rCBV^T₂, show close agreement in appearance, although blood vessels are slightly narrower on maps.