註釋 Background and Aims:Collateral blood flow is believed to be pivotal in large-artery steno-occlusive disease to prevent ischemic tissue damage, which may involve the cerebral cortex. At an early stage, pathological structural alterations may be subtle or subclinical and not detected on conventional magnetic resonance imaging (MRI). The aim of this study was to investigate microstructural cortical tissue damage in chronic cerebral hypoperfusion, which may reasonably be assumed to depend on leptomeningeal collateral supply.Methods:30 patients with high-grade unilateral internal carotid artery (ICA) or middle cerebral artery (MCA) stenosis/occlusion were included. Microstructural changes of normal-appearing hypoperfused cerebral cortex were assessed with quantitative (q)T2 mapping. The volumetric abundance of leptomeningeal collaterals was directly quantified based on perfusion-weighted imaging (PWI), which was also used to determine intravascular hemodynamic properties of collateral vessels. In patients with ICA pathology, flow velocity in the poststenotic MCA was determined with duplex ultrasonography.Results:Cortical qT2 values were significantly increased within the dependent vascular territory compared to the contralateral unaffected side (p=0.0001). While volumetric abundance of adjacent leptomeningeal collaterals was significantly increased (p 