MR images and signal-intensity time curves in different types of hyperemia. A, Slight hyperintensity of the left hemisphere was found on T2-weighted imaging and DWI, respectively, with remarkable enhancement on contrast-enhanced T1-weighted imaging (arrow head) in G1-1 and G3-1. Ten days after reperfusion, signal intensity returned to normal on T2-weighted imaging and DWI, and no enhancement was found on contrast-enhanced T1-weighted imaging in G1-2. However, the hyperintensity remained on T2-weighted imaging and DWI, with continuous enhancement on contrast-enhanced T1-weighted imaging in G3-2 (arrow head). B, Signal intensity plotted against time for the infarct region (dots in G1-1, triangles in G3-2) and homologous areas on the contralateral side (squares). The lines represent the curves derived by using the DCE pMRI. The return to baseline is lower in G3-2 than in G1-1, suggesting high permeability of the BBB. G1-1 = three hours after reperfusion of rats in group 1; G1-2 = ten days after reperfusion of rats in group 1; G3-1 = three hours after reperfusion of rats in group 3; G3-2 = ten days after reperfusion of rats in group 3; T1WI C+ = contrast-enhanced T1-weighted imaging; Con l = contralateral side; b hyp = benign hyperemia; m hyp = malignant hyperemia.