Blood clots or emboli constitute the most common causes of clinical stroke. Brain injury in thromboembolic stroke is extensive and variable. Brain injury is monitored using a combination of high-resolution, multi-slice DWI and PWI methods. Methods A single embolus was injected into the cerebral circulation and DWI was acquired in 3 minutes, covering the brain. ADC maps were obtained and was followed by PWI to track contrast bolus transit. Multi-slice acquisition sequentially sampled 4 adjacent slices from front to back every 2 seconds. Following contrast administration by bolus injection, Tl-wt. SE multi-slice images were acquired to observe the presence of significant Tl-shortening associated with bleeds and hemorrhages. Results The extent of stroke varied widely in both total volume and location of lesions at both the 60 and 120 minute observations in Figure 24. Within each infarcted tissue, perfusion was decreased to near zero. Occurrence of infarct at 60 minutes resulted in a variety of outcomes: later resolution of lesions, evolution of lesions distal to the original stroke and lesions in the contralateral hemisphere, all similar to the clinical setting. The synthesized relative perfusion maps proved to be essential in understanding the complex patterns of stroke formations and ADC decreases. In animals exhibiting collateral routes of flow, maps of the relative bolus arrival time between regions were most useful, particularly in the ischemic tissues not exhibiting ADC decreases. Use of Ti-shortening contrast as a T2* bolus-tracking agent proved to be useful on Ti-weighted SE MRI in establishing the presence and extent of hemorrhage in an unusually large number (50%) of animals studied. Location and severity of bleeds correlated well with gross pathology. Discussion This study establishes that DWI and PWI methods arc effective for routine use in the clinics.
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