Use of spin echo T-2 BOLD in assessment of cerebral misery perfusion at 1.5 T

Inadequate blood supply relative to metabolic demand, a haemodynamic condit ion termed as misery perfusion, often occurs in conjunction with acute isch aemic stroke. Misery perfusion results in adaptive changes in cerebral phys iology including increased cerebral blood volume (CBV) and oxygen extractio n ratio (OER) to secure substrate supply for the brain. It has been suggest ed that the presence of misery perfusion may be an indication of reversible ischaemia, thus detection of this condition may have clinical impact in ac ute stroke imaging. The ability of single spin echo T-2 to detect misery pe rfusion in the rat brain at 1.5 T owing to its sensitivity to blood oxygena tion level dependent (BOLD) contrast was studied both theoretically and exp erimentally. Based on the known physiology of misery perfusion, tissue morp hometry and blood relaxation data. T, behaviour in misery perfusion was sim ulated. The interpretation of these computations was experimentally assesse d by quantifying T, in a rat model for cerebral misery perfusion. CBF was q uantified with the H-2 clearance method. A drop of CBF from 58 +/- 8 to 17 +/- 3 ml/100 g/min in the parieto-frontal cortex caused shortening of T-2 f rom 66.9 +/- 0.4 to 64.6 +/- 0.5 ms. Under these conditions, no change in d iffusion MRI was detected. In contrast, the cortex with CBF of 42 +/- 7 ml/ 100 g/min showed no change in T-2. Computer simulations accurately predict ed these T-2 responses. The present study shows that the acute drop of CBF by 70% causes a negative BOLD that is readily detectable by T-2 MRI at 1.5 T. Thus BOLD may serve as an index of misery perfusion thus revealing viabl e tissue with increased OER. (C) 2001 Elsevier Science B.V. All rights rese rved.