Dynamic Contrast-enhanced Ultrasound Imaging for Cerebral Perfusion Measurement in Acute Ischemic Stroke

Detailed Summary

Stroke, a personal, familial, and social disaster, is the first cause of acquired disability, the second cause of dementia, and the third cause of death worldwide. Its associated socio-economic costs are astronomic. The burden of stroke is likely to increase, given the aging of the population and the growing incidence of many vascular risk factors. Therefore, apart from further development of stroke prevention and treatment strategies, rational and effective tools for diagnosis, monitoring, and follow-up for stroke patients have potential high long-term clinical and economic consequences. For neuroradiological work-up, computed tomography (CT) or magnetic resonance imaging (MRI) are used as gold standard techniques to detect presence or absence, effective state, and extent of stroke. However, these techniques achieve simply a baseline study of ischemia occurred and can deliver only a snapshot of brain parenchyma and vessels. Furthermore, their rapid and actual availability, especially in primary hospitals, and their dynamic capabilities and predictive values for further infarction are poor with critically ill patients have to be repeatedly transferred to the scanning unit for each measurement. Whereas CT examination is associated with x-ray radiation and may miss early detection of stroke, MRI is associated with higher costs and not generally routinely and around-the clock available in all the hospitals. Therefore, a simple, fast, repeatable, non-hazardous, and non-invasive dynamic bedside tool for the detection of acute brain tissue hypoperfusion and monitoring for potential further infarction or efficacy of thrombolysis either by systemic intravenous thrombolytic therapy with recombinant tissue plasminogen activator (rt-PA) or by selective intraarterial fibrinolysis and mechanical recanalization, both combined with or without bridging after acute ischemic stroke, is strongly needed. A promising alternative method of diagnosing stroke represents contrast-enhanced ultrasound perfusion imaging (UPI). What makes UPI so valuable is the advantage of repeatedly and non-invasively detecting brain tissue at risk for infarction by dynamic direct brain tissue perfusion assessment and not by surrogate parameters, like blood flow velocity or vessel diameter. Because of the possibility to screen and repeatedly measure the state of perfusion, the chances increase to diagnose and monitor ischemic stroke and to define the appropriate window for treatment. The perfusion analysis would also allow determination of treatment results and guidance of rapid and adequate further therapy. Therefore, the present pilot study in 40 patients is initiated. The objectives of this observational diagnostic cohort trial are to evaluate feasibility and practicability of repeated bedside assessments by contrast enhanced UPI in acute ischemic stroke patients and to assess whether UPI can detect alterations in brain tissue perfusion before and after recanalising therapy of strokes. Assessment of cerebral perfusion by CT or MRI serves as reference and its results are compared to UPI data.

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