Quantitative magnetic resonance imaging assessment of cerebral ischemia in rat using on-resonance T1 in the rotating frame

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Abstract
Sensitivity of T1 in the rotating frame (T1ρ) to both transient cerebral ischemia and cortical hypoperfusion was studied in rats. T1ρ is believed to probe water in close contact with macromolecules, revealing water spins with restricted rotational mobility relative to bulk water. It is shown that T1ρ increases within minutes of occlusion, thereby demonstrating it as a new, sensitive indicator of ischemia. After reperfusion at 90 minutes of middle cerebral artery occlusion, T1ρ remains elevated or increases in tissue destined to neuronal damage but returns to the normal level if no neuronal damage develops within 24 hours. T1ρ determined during the first 2 hours of reperfusion shows a significant positive correlation with the ultimate neuronal damage score. However, T1ρ is not affected by acute hypoperfusion. These data show that, by combining three magnetic resonance imaging coefficients, i.e. T1ρ, T2, and diffusion, viable hypoperfused areas that do not develop neuronal damage within 24 hours can be distinguished correctly from tissue already destined for neuronal damage. Magn Reson Med 42:268–276, 1999.