Estimation of oxygen extraction fraction based on hemodynamic measurements using DSC-MRI

\ua9 2025 The Authors. Published under a Creative Commons Attribution 4.0 International (CC BY 4.0) license. Oxygen availability in brain tissue is closely linked to local hemodynamics and even slight disturbances in the cerebral microcirculation may damage cells due to the brain’s high energy demands. In addition to local cerebral blood flow, knowledge of the oxygen extraction fraction (OEF) is critical when assessing brain tissue oxygenation. A biophysical model that relates the brain’s microvascular hemodynamics to OEF has previously been proposed. Here, we aimed to calibrate and compare this model with OEF measurements determined by [15O]-based positron emission tomography imaging (PET). Local brain hemodynamics were assessed in 68 healthy elderly individuals using dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI). Average DSC-MRI-based mean transit time and capillary transit time heterogeneity were compared to PET OEF to calibrate the model parameters. The calibrated biophysical model produced OEF estimates in the range of PET OEF with a moderate correlation (r = 0.31, p = 0.009), albeit with a tendency to overestimate smaller PET OEF values and underestimate larger PET OEF values. We discuss the assumptions made when modeling oxygen transport in measurements of local hemodynamics and in [15O]-based tracer uptake, respectively, and propose that the biophysical model provides a valuable tool to link hemodynamic changes to oxygen uptake in the human brain

Umbau einer Wanderrostfeuerung zum Einsatz von Feinkohlen mit hohem Feinkornanteil Schlussbericht

With 6 refs., 15 figs.Copy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Neurovascular Coupling During Cortical Spreading Depolarization And - Depression

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Increased deoxythymidine triphosphate levels is a feature of relative cognitive decline

Mitochondrial bioenergetics, mitochondrial reactive oxygen species (ROS) and cellular levels of nucleotides have been hypothesized as early indicators of Alzheimer’s disease (AD). Utilizing relative decline of cognitive ability as a predictor of AD risk, we evaluated the correlation between change of cognitive ability and mitochondrial bioenergetics, ROS and cellular levels of deoxyribonucleotides. Change of cognitive abilities, scored at ages of approximately 20 and 57 was determined for a cohort of 1985 male participants. Mitochondrial bioenergetics, mitochondrial ROS and whole-cell levels of deoxyribonucleotide triphosphates were measured in peripheral blood mononuclear cells (PBMCs) from a total of 103 selected participants displaying the most pronounced relative cognitive decline and relative cognitive improvement. We show that relative cognitive decline is associated with higher PBMC content of deoxythymidine-triphosphate (dTTP) (20%), but not mitochondrial bioenergetics parameters measured in this study or mitochondrial ROS. Levels of dTTP in PBMCs are indicators of relative cognitive change suggesting a role of deoxyribonucleotides in the etiology of AD

Transit time homogenization in ischemic stroke – A novel biomarker of penumbral microvascular failure?

Cerebral ischemia causes widespread capillary no-flow in animal studies. The extent of microvascular impairment in human stroke, however, is unclear. We examined how acute intra-voxel transit time characteristics and subsequent recanalization affect tissue outcome on follow-up MRI in a historic cohort of 126 acute ischemic stroke patients. Based on perfusion-weighted MRI data, we characterized voxel-wise transit times in terms of their mean transit time (MTT), standard deviation (capillary transit time heterogeneity – CTH), and the CTH:MTT ratio (relative transit time heterogeneity), which is expected to remain constant during changes in perfusion pressure in a microvasculature consisting of passive, compliant vessels. To aid data interpretation, we also developed a computational model that relates graded microvascular failure to changes in these parameters. In perfusion–diffusion mismatch tissue, prolonged mean transit time (&gt;5 seconds) and very low cerebral blood flow (≤6 mL/100 mL/min) was associated with high risk of infarction, largely independent of recanalization status. In the remaining mismatch region, low relative transit time heterogeneity predicted subsequent infarction if recanalization was not achieved. Our model suggested that transit time homogenization represents capillary no-flow. Consistent with this notion, low relative transit time heterogeneity values were associated with lower cerebral blood volume. We speculate that low RTH may represent a novel biomarker of penumbral microvascular failure. </jats:p