The dependence of CO cerebrovascular reactivity (CVR) on caffeine.

Cerebrovascular reactivity (CVR) represents an important marker of brain vascular health, particularly in the context of small and large vessel diseases. However, an undesired feature of this measure is that there exist large variations in CVR values across individuals, which is mainly attributed to physiological factors. Here, we test the hypothesis that caffeine, a widely consumed neurostimulant, has a significant effect on CVR measured with MRI.

Diminished Cerebral Oxygen Extraction and Metabolic Rate in Neonates With Hypoxic Ischemic Encephalopathy.

Background: Hypoxic ischemic encephalopathy (HIE), which is associated with perinatal disruption of cerebral oxygen supply and utilization, is a leading cause of neonatal mortality and severe neurological impairment in childhood. The present study investigated whether key physiological parameters of cerebral oxygen utilization, specifically oxygen extraction fraction (OEF), cerebral blood flow, and cerebral metabolic rate of oxygen (CMRO), were altered in neonates with HIE, and whether these parameters were associated with clinical indices.

Methods: In this case-control study, neonates with HIE and healthy control newborns were enrolled from the Johns Hopkins Children's Center and the Children's Hospital at the University of Maryland Medical Center.

Noninvasive quantification of renal venous oxygenation with field-insensitive T preparation and fast acquisition.

Purpose: The development of a reliable MRI technique to quantify renal oxygen extraction fraction and metabolism can help in the evaluation of tissue hypoxia in kidney diseases. This study aims to develop a field inhomogeneity-insensitive and motion-robust method for noninvasive renal oxygenation quantification.

Methods: A new sequence using adiabatic T preparation (B-insensitive-rotation-n) with Fourier transform-based velocity-selective saturation and echo-planar imaging readout was proposed, referred to as TRUFIFA (T relaxation under field-insensitive preparation and fast acquisition).

Simultaneous Multiparametric Estimation of Arteriovenous Malformations Hemodynamics Using MR Fingerprinting ASL (MRF-ASL).

Background And Purpose: Accurate hemodynamic characterization of cerebral AVMs is critical for treatment planning, risk stratification, and post-treatment monitoring but remains challenging due to their abnormal angioarchitecture. MR-fingerprinting (MRF) arterial-spin-labeling (ASL) is a novel, non-invasive technique that enables simultaneous quantification of cerebral blood flow (CBF), arterial cerebral blood volume (aCBV), and bolus arrival time (BAT) within a single 5-minute scan. This study evaluates the feasibility of MRF-ASL in assessing AVM hemodynamics and compares its sensitivity for AVM detection with CBF measurements obtained using single-delay pseudo-continuous ASL (pCASL).

Elevated cerebral oxygen extraction in patients with post-COVID conditions.

Objectives: Dysfunction of cerebral microcirculation due to SARS-CoV-2 infection has been postulated to be a plausible mechanism for the neurological symptoms of post-COVID-19 conditions (neuro-PCC), affecting oxygen homeostasis in the brain. In this study, we aimed to investigate the balance between cerebral oxygen delivery and consumption, measured by oxygen extraction fraction (OEF), in patients with neuro-PCC.

Methods: 25 participants with neuro-PCC (8 previously hospitalized and 17 not hospitalized) and 59 age-matched healthy controls were studied.

High-Fidelity MRI Assessment of Cerebral Perfusion in Healthy Neonates Less Than 1 Week of Age.

Background: Perfusion imaging of the brain has important clinical applications in detecting neurological abnormalities in neonates. However, such tools have not been available to date. Although arterial-spin-labeling (ASL) MRI is a powerful noninvasive tool to measure perfusion, its application in neonates has encountered obstacles related to low signal-to-noise ratio (SNR), large-vessel contaminations, and lack of technical development studies.

MR Assessment of Acute Changes of Cerebral Perfusion, Metabolism, and Blood-Brain Barrier Permeability in Response to Aerobic Exercise.

Background: It remains unclear how a single bout of exercise affects brain perfusion, oxygen metabolism, and blood-brain barrier (BBB) permeability. Addressing this unresolved issue is essential to understand the acute changes in cerebral physiology induced by aerobic exercise.

Purpose: To dynamically monitor the acute changes in cerebral physiology subsequent to a single aerobic exercise training session using noninvasive MRI measurements.

Vessel-specific quantification of cerebral venous oxygenation with velocity-encoding preparation and rapid acquisition.

Purpose: Non-invasive measurement of cerebral venous oxygenation (Y) is of critical importance in brain diseases. The present work proposed a fast method to quantify regional Y map for both large and small veins.

Methods: A new sequence was developed, referred to as TRU-VERA (T relaxation under velocity encoding and rapid acquisition, which isolates blood spins from static tissue with velocity-encoding preparation, modulates the T weighting of venous signal with T-preparation and utilizes a bSSFP readout to achieve fast acquisition with high resolution.

CO cerebrovascular reactivity measured with CBF-MRI in older individuals: Association with cognition, physical function, amyloid and tau proteins.

Vascular pathology is the second leading cause of cognitive impairment and represents a major contributing factor in mixed dementia. However, biomarkers for vascular cognitive impairment and dementia (VCID) are under-developed. Here we aimed to investigate the potential role of CO2 Cerebrovascular Reactivity (CVR) measured with phase-contrast quantitative flow MRI in cognitive impairment and dementia.

Comparison of cerebral oxygen extraction fraction using ASE and TRUST methods in patients with sickle cell disease and healthy controls.

Abnormal oxygen extraction fraction (OEF), a putative biomarker of cerebral metabolic stress, may indicate compromised oxygen delivery and ischemic vulnerability in patients with sickle cell disease (SCD). Elevated OEF was observed at the tissue level across the brain using an asymmetric spin echo (ASE) MR method, while variable global OEFs were found from the superior sagittal sinus (SSS) using a T2-relaxation-under-spin-tagging (TRUST) MRI method with different calibration models. In this study, we aimed to compare the average ASE-OEF in the SSS drainage territory and TRUST-OEF in the SSS from the same SCD patients and healthy controls.

VICTR: Venous transit time imaging by changes in T relaxation.

Purpose: Abnormalities in cerebral veins are a common finding in many neurological diseases, yet there is a scarcity of MRI techniques to assess venous hemodynamic function. The present study aims to develop a noncontrast technique to measure a novel blood flow circulatory measure, venous transit time (VTT), which denotes the time it takes for water to travel from capillary to major veins.

Methods: The proposed sequence, venous transit time imaging by changes in T relaxation (VICTR), is based on the notion that as water molecules transition from the tissue into the veins, they undergo a change in T relaxation time.

Brain Frontal-Lobe Misery Perfusion in COVID-19 ICU Survivors: An MRI Pilot Study.

Post-acute COVID-19 syndrome (PCS) is highly prevalent. Critically ill patients requiring intensive care unit (ICU) admission are at a higher risk of developing PCS. The mechanisms underlying PCS are still under investigation and may involve microvascular damage in the brain.

Blood-brain barrier breakdown in COVID-19 ICU survivors: an MRI pilot study.

Objectives: Coronavirus disease 2019 (COVID-19) results in severe inflammation at the acute stage. Chronic neuroinflammation and abnormal immunological response have been suggested to be the contributors to neuro-long-COVID, but direct evidence has been scarce. This study aims to determine the integrity of the blood-brain barrier (BBB) in COVID-19 intensive care unit (ICU) survivors using a novel MRI technique.

Automatic Rejection based on Tissue Signal (ARTS) for motion-corrected quantification of cerebral venous oxygenation in neonates and older adults.

Objective: Cerebral venous oxygenation (Y) is a key parameter for the brain's oxygen utilization and has been suggested to be a valuable biomarker in various brain diseases including hypoxic ischemic encephalopathy in neonates and Alzheimer's disease in older adults. T-Relaxation-Under-Spin-Tagging (TRUST) MRI is a widely used technique to measure global Y level and has been validated against gold-standard PET. However, subject motion during TRUST MRI scan can introduce considerable errors in Y quantification, especially for noncompliant subjects.

Quantification of T and T of subarachnoid CSF: Implications for water exchange between CSF and brain tissues.

Purpose: To quantify the T and T values of CSF in the subarachnoid space (SAS) at 3 T and interpret them in the context of water exchange between CSF and brain tissues.

Methods: CSF T was measured using inversion recovery, and CSF T was assessed using T -preparation. T and T values in the SAS were compared with those in the frontal horns of lateral ventricles, which have less brain-CSF exchange.

Dependence of resting-state-based cerebrovascular reactivity (CVR) mapping on spatial resolution.

Cerebrovascular reactivity (CVR) is typically assessed with a carbon dioxide (CO) stimulus combined with BOLD fMRI. Recently, resting-state (RS) BOLD fMRI has been shown capable of generating CVR maps, providing a potential for broader CVR applications in neuroimaging studies. However, prior RS-CVR studies have primarily been performed at a spatial resolution of 3-4 mm voxel sizes.

Deep-learning-enabled brain hemodynamic mapping using resting-state fMRI.

Cerebrovascular disease is a leading cause of death globally. Prevention and early intervention are known to be the most effective forms of its management. Non-invasive imaging methods hold great promises for early stratification, but at present lack the sensitivity for personalized prognosis.

Toward vendor-independent measurement of cerebral venous oxygenation: Comparison of TRUST MRI across three major MRI manufacturers and association with end-tidal CO.

Cerebral venous oxygenation (Y ) is a valuable biomarker for a variety of brain diseases. T relaxation under spin tagging (TRUST) MRI is a widely used method for Y quantification. In this work, there were two main objectives.

MRI assessment of cerebral oxygen extraction fraction in the medial temporal lobe.

The medial temporal lobe (MTL) is a key area implicated in many brain diseases, such as Alzheimer's disease. As a functional biomarker, the oxygen extraction fraction (OEF) of MTL may be more sensitive than structural atrophy of MTL, especially at the early stages of diseases. However, there is a lack of non-invasive techniques to measure MTL-OEF in humans.

Longitudinal changes in brain oxygen extraction fraction (OEF) in older adults: Relationship to markers of vascular and Alzheimer's pathology.

Introduction: Oxygen extraction fraction (OEF) reflects the balance between oxygen delivery and consumption. We longitudinally measured OEF in older adults to examine the relationship with markers of Alzheimer's disease (AD) and vascular pathology.

Methods: One hundred thirty-seven participants were studied at two time-points at an interval of 2.

Blood-brain barrier permeability in response to caffeine challenge.

Purpose: Caffeine is known to alter brain perfusion by acting as an adenosine antagonist, but its effect on blood-brain barrier (BBB) permeability is not fully elucidated. This study aimed to dynamically monitor BBB permeability to water after a single dose of caffeine tablet using a non-contrast MRI technique.

Methods: Ten young healthy volunteers who were not regular coffee drinkers were studied.

Age-Related Tortuosity of Carotid and Vertebral Arteries: Quantitative Evaluation With MR Angiography.

Background And Purpose: The vascular tortuosity (VT) of the internal carotid artery (ICA), and vertebral artery (VA) can impact blood flow and neuronal function. However, few studies involved quantitative investigation of VT based on magnetic resonance imaging (MRI). The main purpose of our study was to evaluate the age and gender effects on ICA and VA regarding the tortuosity and flow changes by applying automatic vessel segmentation, centerline tracking, and phase mapping on MR angiography.

Cerebral oxygen extraction fraction MRI: Techniques and applications.

The human brain constitutes 2% of the body's total mass but uses 20% of the oxygen. The rate of the brain's oxygen utilization can be derived from a knowledge of cerebral blood flow and the oxygen extraction fraction (OEF). Therefore, OEF is a key physiological parameter of the brain's function and metabolism.