Effect of Hemoglobin and Blood Glucose Levels on CT Perfusion Ischemic Core Estimation: A Post Hoc Analysis of the ESCAPE-NA1 Trial

Dual-modal super-resolution ultrasound and NIR-II fluorescence imaging of ischemic stroke with ICG-doped porous PLGA microspheres

Ischemic stroke, resulting from the obstruction of blood flow to the brain, remains a leading cause of morbidity and mortality worldwide. Traditional imaging modalities, such as magnetic resonance imaging and computed tomography, while effective for identifying stroke locations, are often limited in their ability to detect early pathological changes due to constraints in spatial resolution and sensitivity. This study introduces a novel dual-modal imaging approach that employs indocyanine green-doped porous poly (lactic-co-glycolic acid) (PLGA) microspheres (ICG-pPLGA MPs) for super-resolution ultrasound and near-infrared II (NIR-II) fluorescence imaging of ischemic stroke. The porous structure of ICG-pPLGA MPs enhances their stability, prolongs their circulation time, and improves ultrasound contrast compared to commercial lipid microbubbles. Additionally, the NIR-II fluorescence allows for high-resolution and noninvasive visualization of superficial vasculature. In a rat model of ischemic stroke, we demonstrate the capability of ICG-pPLGA MPs to achieve high-resolution imaging of cerebrovascular structures and functions, surpassing the imaging performance of standard diffusion-weighted imaging. Our findings underscore the potential of this dual-modal imaging technique using ICG-pPLGA MPs to accurately characterize microvascular changes during ischemic events, thus offering valuable insights for early diagnosis and therapeutic monitoring.

Cerebral Infarct Growth: Pathophysiology, Pragmatic Assessment, and Clinical Implications

Cerebral ischemic injury occurs when blood flow drops below a critical level, resulting in an energy failure. The progressive transformation of hypoperfused viable tissue, the ischemic penumbra, into infarction is a mechanism shared by patients with ischemic stroke if timely reperfusion is not achieved. Yet, the pace at which this transformation occurs, known as the infarct growth rate (IGR), exhibits remarkable heterogeneity among patients, brain regions, and over time, reflecting differences in compensatory collateral flow and ischemic tolerance. We review (1) the pathophysiology of infarct growth, (2) the advantages and pitfalls of different approaches of IGR measurement, (3) research gaps for future studies, and (4) the clinical implications of stroke progressor phenotypes. The estimated average IGR in patients with acute large vessel occlusion stroke is 5.4 mL/h although there is wide variability based on ischemic stroke subtype, occlusion location, presence of collaterals, and patient baseline status. The IGR can be calculated using various pragmatic strategies, mostly either quantifying the extension of the infarct at a particular time and dividing this measure by the time that elapsed from symptom onset to imaging assessment or by using collateral blood flow status as a radiological surrogate marker. The IGR defines a spectrum of clinical stroke phenotypes, often dichotomized into fast and slow progressors. An IGR ≥10 mL/h and the perfusion metric hypoperfusion intensity ratio ≥0.5 are commonly used definitions of fast progressors. A nuanced understanding of the IGR and stroke progressor phenotypes could have clinical implications, including informing prognostication, acute decision-making in peripheral-to-comprehensive transfer patients eligible for thrombectomy, and selection for adjuvant neuroprotective agents.