Journal of neuroimaging : official journal of the American Society of Neuroimaging
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The phenomenon known as neural flow coupling (NFC) occurs at the capillary level where there are no known pressure controlling structures. Recent developments in advanced magnetic resonance imaging technologies have made possible in vivo direct investigations of water physiology that have shed new insight on the water dynamics of the cortical pericapillary space and their complex functionality in relation to NFC. Neural activities initiate a chain of events that ultimately affect NFC. ⋯ Reduction of pericapillary water pressure results in a negative balance between pericapillary and intraluminal capillary pressure, allowing for capillary caliber expansion. Proton permeability through the tight junctions of the blood brain barrier is significantly high owing to the Grotthuss proton "tunneling" mechanism and, therefore, carbonic anhydrase (CA) type IV (CA-IV) anchored to the luminal surface of brain capillaries functions as scavenger of extracellular protons. CA-IV inhibition by acetazolamide or carbon dioxide results in the accumulation of extracellular protons, causing AQP-4 inhibition and a secondary increase in rCBF.
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Eddy current distortion is an important issue that may influence the quantitative measurements of diffusion tensor imaging (DTI). The corrections of eddy current artifacts could be performed using bipolar diffusion gradients or unipolar gradients with affine registration. Whether the diffusion pulse sequence affects the quantification of DTI indices and the technique that produces more reliable DTI indices in terms of reproducibility both remain unclear. ⋯ The results revealed that the reproducibility and mean values of DTI indices were significantly affected by the pulse sequence. Unipolar DTI exhibited significantly higher reproducibility than bipolar DTI even at the same TE, and the mean values of DTI indices were significantly different between them. Therefore, we concluded that the reproducibility and mean values of DTI indices were significantly influenced by diffusion pulse sequences.
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Ultrasonographic measurement of optic nerve sheath diameter (ONSD) can successfully be used to estimate intracranial pressure (ICP) elevation. Its utility in corroboration of brain death (BD) was herein studied. ⋯ ONSD is significantly greater in subjects with BD. However, quantification of ONSD cannot discriminate BD subjects from comatose ones with raised ICP with 100% certainty.
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Prognostic evaluation based on cortical vein score difference in stroke (PRECISE) score, a novel venous grading scale better predicted stroke outcomes. Henceforth, we aimed to describe and determine if a physiologically relevant combined arterial and venous grading scale (CRISP grading scale) is accurate in determining 90-day stroke outcomes in patients with proximal arterial occlusion in the anterior circulation. ⋯ CRISP grading was precise in predicting stroke outcomes when compared to individual imaging scales including arterial collateral grading, PRECISE score and CTA-SI ASPECTS in patients with proximal arterial occlusion in the anterior circulation.
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Though still debated, early reperfusion is increasingly used as a biomarker for clinical outcome. However, the lack of a standard definition hinders the assessment of reperfusion therapies and study comparisons. The objective was to determine the optimal early reperfusion criteria that predicts clinical outcome in ischemic stroke. ⋯ TTP and Tmax should be preferred to MTT in defining early reperfusion. GBTM provided a clinically relevant reperfusion classification that does not require prespecified delay thresholds or clinical outcomes.