Normal brain function depends critically on moment-to-moment regulation of oxygen supply by the bloodstream to meet changing metabolic needs. Neurovascular coupling, a range mechanisms that converge arterioles adjust local cerebral blood flow (CBF), represents our current framework for understanding this regulation. We modeled combined effects CBF and capillary transit time heterogeneity (CTTH) maximum extraction fraction (OEF(max)) rate can biophysically be supported, given tissue tension....

Pulsed field gradient diffusion sequences (PFG) with multiple encoding blocks have been indicated to offer new microstructural tissue information, such as the ability detect nonspherical compartment shapes in macroscopically isotropic samples, i.e. samples negligible directional signal dependence on gradients standard experiments. However, current acquisition schemes are not rotationally invariant sense that derived metrics depend orientation of sample, and affected by interplay sampling...

Diffusion MRI (dMRI) provides contrast that reflect diffusing spins' interactions with microstructural features of biological systems, but its specificity remains limited due to the ambiguity relation underlying microstructure. To improve specificity, biophysical models white matter (WM) typically express dMRI signals according Standard Model (SM) and have more recently in gray (GM) attempted incorporate cell soma (the SANDI model). The validity assumptions these models, however, largely...

We consider L\'evy flights subject to external force fields. This anomalous transport process is described by two approaches, a Langevin equation with noise and the corresponding generalized Fokker-Planck containing fractional derivative in space. The cases of free flights, constant force, linear Hookean are analyzed detail, we corroborate our findings results from numerical simulations. discuss non-Gibbsian character stationary solution for case i.e., deviation Boltzmann equilibrium long...

As neurons of the developing brain form functional circuits, they undergo morphological differentiation. In immature cerebral cortex, radially-oriented cellular processes undifferentiated impede water diffusion parallel, but not perpendicular, to pial surface, as measured via diffusion-weighted magnetic resonance imaging, and give rise anisotropy. cortex matures, loss anisotropy accompanies A quantitative relationship is proposed here relate measurements directly characteristics neuronal...

Abstract Purpose Results from several recent studies suggest the magnetic resonance diffusion‐derived metric mean kurtosis (MK) to be a sensitive marker for tissue pathology; however, lengthy acquisition and postprocessing time hamper further exploration. The purpose of this study is introduce evaluate new MK rapid protocol its estimation. Methods requires 13 standard diffusion‐weighted images, followed by linear combination log diffusion signals, thus avoiding nonlinear optimization. method...

The regional availability of oxygen in brain tissue is traditionally inferred from the magnitude cerebral blood flow (CBF) and concentration arterial blood. Measurements CBF are therefore widely used localization neuronal response to stimulation evaluation patients suspected acute ischemic stroke or flow-limiting carotid stenosis. It was recently demonstrated that capillary transit time heterogeneity (CTH) limits maximum extraction fraction (OEF(max)) can be achieved for a given CBF. Here we...

Diffusion kurtosis imaging (DKI) is an extension of diffusion tensor that accounts for leading non‐Gaussian effects. In DKI studies, a wide range different gradient strengths ( b ‐values) used, which known to affect the estimated diffusivity and parameters. Hence there need assess accuracy precision parameters as function ‐value. This work examines error in estimation mean (MKT) with respect ground truth, using simulations based on biophysical model both gray (GM) white (WM) matter. Model...

Purpose Microscopic fractional anisotropy (µFA) can disentangle microstructural information from orientation dispersion. While double diffusion encoding (DDE) MRI methods are widely used to extract accurate µFA, it has only recently been proposed that powder‐averaged single (SDE) signals, when coupled with the standard model (SM) and a set of constraints, could be for µFA estimation. This study aims evaluate as derived spherical mean technique (SMT) well more generally SM signals. Methods...

Diffusional Kurtosis Imaging (DKI) is a sensitive biomarker for microstructure in health and disease. However, DKI not specific to any microstructural property since it may emerge from several different sources. Q-space trajectory encoding has been proposed decoupling isotropic anisotropic kurtosis. Still, this method assume that the system comprised of multiple Gaussian diffusion components. Here, we develop more general framework resolving underlying kurtosis We introduce Correlation...

To develop a denoising strategy leveraging redundancy in high-dimensional data.The SNR fundamentally limits the information accessible by MRI. This limitation has been addressed host of techniques, recently including so-called MPPCA: principal component analysis signal followed automated rank estimation, exploiting Marchenko-Pastur distribution noise singular values. Operating on matrices comprised data patches, this popular approach objectively identifies components and, ideally, allows to...

Glioblastomas are aggressive brain tumors with dismal prognosis. One of the main bottlenecks for developing more effective therapies glioblastoma stems from their histologic and molecular heterogeneity, leading to distinct tumor microenvironments disease phenotypes. Effectively characterizing these features would improve clinical management glioblastoma. Glucose flux rates through glycolysis mitochondrial oxidation have been recently shown quantitatively depict proliferation in mouse models...

Antiangiogenic therapies are being pursued as a means of starving tumors their energy supply. Although numerous studies show that such render hypoxic, just many have, surprisingly, shown improved tumor oxygenation. These contradicting findings challenge both the original rationale for antiangiogenic therapy and our understanding physiology tissue The flow-diffusion equation, which describes relation between blood flow extraction freely diffusible molecules in tissue, was recently extended to...

Abstract The influence of drugs, active on 5-hydroxytryptamine (5-HT) mechanisms, has been examined the anorexigenic activity fenfluramine and (+)-amphetamine in rats trained to consume their daily food ration during 6 h. Chlorimipramine, which inhibits re-uptake mechanisms central 5-HT neurons, blocking drugs methergoline methysergide were used. Fenfluramine, 7.5 mg kg−1, amphetamine, 2.5 given 1/2 h before feeding reduced intake following 2 approximately 40% compared with control days....

We recently extended the classic flow-diffusion equation, which relates blood flow to tissue oxygenation, take capillary transit time heterogeneity (CTH) into account. Realizing that cerebral oxygen availability depends on both (CBF) and patterns, we have speculated CTH may be actively regulated changes in morphology function, as well rheology, involved pathogenesis of conditions such dementia ischemia-reperfusion injury. The first equation simplifying assumptions not hold tissue. Here,...