Assessment of intracranial arterial collateralisation and venous microperfusion profile to predict infarct evolution in patients with early ischemic stroke and endovascular treatment using machine learning models

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Acute ischemic stroke (AIS) is defined as disruption of blood flow to the brain caused by an occlusion of a supplying vessel and subsequent oxygen deficiency of the dependent brain tissue. All AIS treatments seek to restore blood flow to the brain by dissolving or removing the clot blocking blood flow to the brain. Intravenous thrombolysis (tPA) has been the predominant treatment of AIS for over two decades. More recently, a minimally-invasive surgery called thrombectomy has been used to effectively remove the blood clot from the artery in the brain. In order to evaluate treatment options, the brain tissue and its blood circulation need to be examined by means of computer tomography or magnetic resonance imaging. On medical imaging, patients with a large amount of salvageable tissue usually show distinctive vessels called intracranial collaterals (IC). During AIS, IC refer to a subsidiary network of vascular channels and robust IC may temporarily preserve blood flow to otherwise critically hypoperfused brain areas thus pivotally effecting the quality of tissue perfusion. Consequently, tissue perfusion is governed by the in-flow of arterial blood to the brain tissue and its outflow into the cerebral veins. In recent years, most studies have focused on the arterial component of this conduit, but very little is known about the draining venous side of it. It has been proposed that determining the blood flow within the venous part of the microvascular system of AIS patients may even better reflect the overall quality of brain tissue perfusion, as it reflects blood flow after passing the brain tissue. It would be highly desirable to properly assess the venous microvascular perfusion status with medical imaging, as it holds crucial information about brain’s pathophysiology during AIS and may serve as an important biomarker for treatment decision making and patients’ clinical outcome. Another critical, yet unresolved question is, whether distinct medical treatment approaches would have notable effects on the robustness of venous microcirculation and treatment outcome. We have established a strong international collaboration between Stanford University (USA) and the University Medical Center Hamburg-Eppendorf (Germany) and generated one of the largest prospectively maintained databases of currently 650 AIS patients treated with tPA and thrombectomy. We propose to investigate the microvascular perfusion profile in AIS patients with a focus on venous out-flow microcirculation using multi-parametric CT and MRI prior to thrombectomy treatment. We aim to determine whether robust cortical venous microcirculation is influenced by intravenous thrombolysis and whether this parameter influences patient outcome. Our results will augment the understanding of cerebral microvascular pathophysiology during AIS and we strive to contribute to a better individual treatment selection and improved medical care to optimize clinical outcome for stroke patients.