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Reversibility of cerebral ischaemia. Dynamic and xenon computed tomography study on ischaemic cerebrovascular disease
Insights
Dynamic CT and xenon CT reveal chronic cerebral ischemia characteristics in stroke patients. Peak height/mean transit time accurately indexes blood flow in mild ischemia but not severe cases.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- Ischemic stroke, particularly in the middle cerebral artery territory, can lead to chronic cerebral ischemia.
- Assessing cerebral blood flow (CBF) in chronic stages is crucial for understanding stroke pathophysiology and patient outcomes.
Purpose of the Study:
- To define the clinical characteristics of chronic cerebral ischemia using dynamic CT and xenon (Xe) CT.
- To evaluate the utility of peak height/mean transit time (PH/MTT) from dynamic CT as an index of cerebral blood circulation.
Main Methods:
- Dynamic CT and xenon (Xe) CT were performed on 25 patients with chronic ischemic stroke in the middle cerebral artery territory.
- Cerebral blood flow (CBF) and PH/MTT were measured and analyzed.
- Correlation between CBF and PH/MTT was assessed across different severities of ischemia.
Main Results:
- PH/MTT from dynamic CT accurately indexed CBF in mild cerebral ischemia (>30 ml/100 g/min).
- In severe ischemia (20-30 ml/100 g/min), CBF changes were not consistently correlated with PH/MTT.
- Discrepancies between CBF and PH/MTT were observed, with some severe ischemia cases showing moderate PH/MTT values.
- Mild CBF reductions were noted in peri-infarct areas of centrum semiovale infarctions.
- Cortico-subcortical infarctions exhibited severe ischemia despite relatively sustained blood circulation.
Conclusions:
- PH/MTT is a reliable index for cerebral blood circulation in mild chronic ischemia but less so in severe cases.
- Xe CT can detect varied patterns of cerebral ischemia around chronic stroke lesions.
- The relationship between CBF and circulation indices like PH/MTT varies depending on ischemia severity and lesion location.
Abstract:
Flow studies using dynamic CT and xenon (Xe) CT were carried out in 25 patients with ischaemic stroke in the territory of the middle cerebral artery to define the clinical characteristics of cerebral ischaemia at a chronic stage. The parameter of peak height/mean transit time (PH/MTT) obtained from dynamic CT can provide an accurate index for blood circulation in the cerebral vascular bed. Xe CT measurements revealed various kinds of ischaemia around the infarction even in the chronic stages. In mild ischaemia of more than 30 ml/100 g/min, reduction of cerebral blood flow (CBF) was well correlated to the PH/MTT. However, in severe ischaemia between 20 and 30 ml/100 g/min, changes of CBF were no longer correlated with the PH/MTT. There were cases showing severe reduction of CBF but which showed sufficient blood circulation (moderate value of PH/MTT). Mild reductions of CBF in parallel with decreased blood supply were often found in the peri-infarct area of infarctions in the centrum semiovale. On the other hand, infarctions in the cortico-subcortical region showed severe ischaemia, in even where blood circulation was relatively well sustained.