Objective: Differentiation of potentially salvageable ischaemic penumbra and irreversibly injured infarct core using computed tomography perfusion (CTP) imaging of brain post-stroke is increasingly being applied in acute stroke imaging to guide thrombolysis decisions. Validation of thresholds used to define penumbra and core is urgently required, as are serial scanning studies to determine whether thresholds change with time (analogous to DWI reversal). The aim of these initial studies was to perform serial CTP studies in an animal model, and correlate CTP maps with 24 hour histology.
Methods: Stroke was induced by the middle cerebral artery thread-occlusion method in male Wistar rats (n=17). CTP scans were obtained on a 64-slice helical CT immediately pre- and post-occlusion and hourly for 3 hours in subgroups with and without reperfusion. Histological changes of infarction were assessed after 24 hours and corresponding CTP slices were coregistered for pixel-based analysis.
Results: Colour maps were generated for cerebral perfusion (TTP, MTT), flow (CBF) and blood volume (CBV) at multiple coronal planes. The ischaemic region was clearly demarcated on cerebral perfusion maps, and progressive reduction in the CBF was seen over time in the region destined to infarct. Interestingly, CBF increased from baseline in the non-ischaemic hemisphere following occlusion of the contralateral middle cerebral artery.
Conclusions: This study has demonstrated for the first time that CTP imaging of stroke is feasible in the most commonly used animal model of stroke. Definitive studies to determine optimal thresholds and reliability of CTP measures for infarct core and penumbra are in progress.