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Acute changes in MRI diffusion, perfusion, T-1, and T-2, in a rat model of oligemia produced by partial occlusion of the middle cerebral artery.
MAGN RESON MED
706 - 712.
Oligemic regions, in which the cerebral blood flow is reduced without impaired energy metabolism, have the potential to evolve toward infarction and remain a target for therapy. The aim of this study was to investigate this oligemic region using various MRI parameters in a rat model of focal oligemia. This model has been designed specifically for remote-controlled occlusion from outside an MRI scanner. Wistar rats underwent remote partial MCAO using an undersize 0.2 mm nylon monofilament with a bullet-shaped tip. Cerebral blood flow (CBFASL) using an arterial spin labeling technique, the apparent diffusion coefficient of water (ADC), and the relaxation times T-1 and T-2 were acquired using an 8.5 T vertical magnet. Following occlusion there was a decrease in CBFASL to 35 +/- 5% of baseline throughout the middle cerebral artery territory. During the entire period of the study there were no observed changes in the ADC. On occlusion, T-2 rapidly decreased in both cortex and basal ganglia and then normalized to the preocclusion values. T-1 values rapidly increased (within approximately 7 min) on occlusion, In conclusion, this study demonstrates the feasibility of partially occluding the middle cerebral artery to produce a large area of oligemia within the MRI scanner. In this region of oligemic flow we detect a rapid increase in T-1 and decrease in T-2. These changes occur before the onset of vasogenic edema. We attribute the acute change in T-2 to increased amounts of deoxyhemoglobin; the mechanisms underlying the change in T-1 require further investigation. (C) 2000 Wiley-Liss, Inc.
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