Cerebral Blood Flow Measurements Research Articles

Changes in Cerebral Hemodynamics and Progression of Subclinical Vascular Brain Disease: A Population-Based Cohort Study.

Cerebral hypoperfusion is associated with vascular brain injury and neurodegeneration, but their longitudinal relationship is largely unknown, especially in healthy older adults. We investigated the longitudinal relationship between cerebral hemodynamics and subclinical vascular brain disease in community-dwelling older adults without stroke or dementia at baseline. Participants underwent brain magnetic resonance imaging scans every 3 to 4 years between 2005 and 2016. Cerebral blood flow (CBF) was measured through 2-dimensional phase-contrast magnetic resonance imaging; the cerebrovascular resistance index (CVRi) was defined as the ratio of mean arterial blood pressure to total CBF. Simultaneous progression in subclinical brain disease was evaluated through repeated magnetic resonance imaging assessment of white matter hyperintensities (WMH), cerebral microbleeds, lacune, and brain atrophy. The longitudinal relationship was estimated using generalized estimating equations, with adjustment for age, sex, smoking habits, body mass index, systolic blood pressure (for CBF measures), lipid level, history of diabetes and cardiovascular disease, and the baseline burden of magnetic resonance imaging markers. Among 3623 older adults (mean age, 61.4±9.3 years; 54.6% women), large decreases and increases in CBF and increases in CVRi over time were associated with white matter hyperintensity progression. The risk ratios for white matter hyperintensity progression were 1.36 (95% CI, 1.19-1.55) for large decreases in total CBF (lowest quartile), 1.02 (95% CI, 0.91-1.14) for moderate decreases (second quartile), and 1.28 (95% CI, 1.14-1.45) for large increases (highest quartile), compared with stable CBF (third quartile). The corresponding risk ratios for changes in CVRi were 1.13 (95% CI, 1.00-1.30), 1.25 (95% CI, 1.09-1.43), and 1.33 (95% CI, 1.16-1.52) for the second to fourth (versus lowest) quartiles, respectively, showing a dose-response relationship. The changes in CBF also demonstrate a similar U-shaped association with the progression of brain atrophy and incident microbleeds, whereas increases in CVRi were associated with lower microbleed risk. Longitudinal changes in CBF and CVRi may capture distinct pathophysiologies linking cerebral hemodynamics to subclinical brain disease, extending beyond single-time point measurements.

A Novel Self-Supervised Learning-Based Method for Dynamic CT Brain Perfusion Imaging.

Dynamic computed tomography (CT)-based brain perfusion imaging is a non-invasive technique that can provide quantitative measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). However, due to high radiation dose, dynamic CT scan with a low tube voltage and current protocol is commonly used. Because of this reason, the increased noise degrades the quality and reliability of perfusion maps. In this study, we aim to propose and investigate the feasibility of utilizing a convolutional neural network and a bi-directional long short-term memory model with an attention mechanism to self-supervisedly yield the impulse residue function (IRF) from dynamic CT images. Then, the predicted IRF can be used to compute the perfusion parameters. We evaluated the performance of the proposed method using both simulated and real brain perfusion data and compared the results with those obtained from two existing methods: singular value decomposition and tensor total-variation. The simulation results showed that the overall performance of parameter estimation obtained from the proposed method was superior to that obtained from the other two methods. The experimental results showed that the perfusion maps calculated from the three studied methods were visually similar, but small and significant differences in perfusion parameters between the proposed method and the other two methods were found. We also observed that there were several low-CBF and low-CBV lesions (i.e., suspected infarct core) found by all comparing methods, but only the proposed method revealed longer MTT. The proposed method has the potential to self-supervisedly yield reliable perfusion maps from dynamic CT images.

Method for detection of cerebral blood flow in neurointensive care using longitudinal arterial spin labeling MRI.

Cerebral blood flow (CBF) is carefully monitored in the Neurointensive Care Unit (NICU) to prevent secondary brain insults in patients who have suffered subarachnoid hemorrhage. Including absolute MRI measurements of CBF in the NICU monitoring protocol could add valuable information and potentially improve patient outcomes. This is particularly feasible at Linköping University Hospital, which uniquely has an MRI scanner located in the NICU, enabling longitudinal CBF measurements while eliminating medical transportation risks. Arterial spin labeling is a subtraction-based MRI technique that can measure CBF globally in the brain without the use of contrast agents, and thus is suitable for repeated measurements over short time periods. Therefore, this work aims to develop and implement a methodological workflow for the acquisition, analysis, absolute quantification, and visualization of longitudinal arterial spin labeling MRI measurements acquired in the clinical NICU setting. At this initial stage, the workflow was implemented and tested using acquired test-retest data and longitudinal data from two healthy participants. Subsequently, the workflow was tested in clinical practice on an intubated and ventilated patient monitored in the NICU after suffering a subarachnoid hemorrhage. To ensure accurate day-to-day comparisons between the repeated measurements, the selection of processing and analysis methods aimed to obtain CBF maps in absolute units of ml/min/100g. These CBF maps were quantified using both the FMRIB Software Library and an openly available flow territory atlas. The test-retest data showed small variations (4.4 ml/min/100g between sessions), and the longitudinal measurement resulted in low CBF variability over 12 days. Despite the greater complexity of clinical data, the quantification and chosen visualization tools proved helpful in interpreting the results. In conclusion, this workflow including repeated MRI measurements could help detect changes in CBF between different measurement days and complement other conventional monitoring techniques in the NICU.

Impaired iron metabolism and cerebral perfusion patterns in unilateral middle cerebral artery stenosis or occlusion: Insights from quantitative susceptibility mapping

Background and purposeCerebral hypoperfusion caused by stenosis or occlusion of the middle cerebral artery (MCA) may be followed by impaired iron metabolism. We explored the association between iron changes of gray matter (GM) nuclei subregions and different cerebral perfusion patterns in patients with chronic unilateral middle cerebral artery (MCA) stenosis or occlusion using quantitative susceptibility imaging (QSM). MethodsSixty-one patients with unilateral MCA stenosis or occlusion were recruited and scored with Alberta-Stroke-Program-Early-CT-Score (ASPECTS) based on relative cerebral blood flow (rCBF) measurements to calculate the number of corresponding hypoperfusion subregions, and then divided into an extensive-hypoperfusion group (EH group), regional-hypoperfusion group (RH group), and normal-perfusion group (Control group) accordingly. The measured magnetic susceptibility of GM nuclei subregions was compared between the lesion and contralateral side for each group and among the three groups. Correlation analysis was performed to assess the relationships of magnetic susceptibility of GM nuclei with mean rCBF, National-Institutes-of-Health-stroke-scale (NIHSS) and modified-Rankin-scale (mRS) scores. ResultsMagnetic susceptibility in the putamen (PU) and globus pallidus (GP) at the lesion side was higher in the EH and RH groups compared with the contralateral side (all P < 0.05). Susceptibility in the lesion side PU and GP showed negative correlations with mean rCBF and positive correlations with NIHSS and mRS scores (all P < 0.05). ConclusionOur findings demonstrate that chronic cerebral hypoperfusion might be one cause of cerebral abnormal iron metabolism. In addition, magnetic susceptibility of PU and GP seems to be correlated with stroke scale scores, suggesting that iron deposition may play an important role in neurologic deficits after ischemic stroke.

Portable Six-Channel Laser Speckle System for Simultaneous Cerebral Blood Flow and Volume Measurement with Potential Application for Characterization of Brain Injury.

In regional cerebrovascular monitoring, cerebral blood flow (CBF) and cerebral blood volume (CBV) are key metrics. Simultaneous, non-invasive measurement of CBF and CBV at different brain locations would advance cerebrovascular monitoring and pave the way for brain injury detection, as current brain injury diagnostic methods are often constrained by high costs, limited sensitivity, and reliance on subjective symptom reporting. This study's aim is to develop a multi-channel non-invasive optical system for measuring CBF and CBV at different regions of the brain simultaneously with a cost-effective, reliable, and scalable system capable of detecting potential differences in CBF and CBV across different regions of the brain. The system is based on speckle contrast optical spectroscopy (SCOS) and consists of laser diodes and board cameras which have been both tested and investigated for safe use on the human head. Results on a cohort of five healthy subjects indicated that the dynamics of both CBF and CBV were synchronized and exhibited similar cardiac period waveforms across all six channels. As a preliminary investigation, we also explored the potential use of our six-channel system for detecting the physiological sequela of brain injury, involving a subject with significant structural brain damage compared to another with lesser structural brain damage. The six-point CBF and CBV measurements were compared to MRI scans, revealing that regions with altered blood dynamics closely correlated with the injury sites identified by MRI.

Catheter ablation increases cerebral blood flow and cognitive function in elderly patients with atrial fibrillation

Abstract Background Atrial fibrillation (AF) has been considered to have an increased risk for cognitive impairment independent of a stroke and a silent micro-infarction. The mechanism of this interaction is unclear. One of the potential explanations is brain hypoperfusion due to a reduced cardiac output. To date, there are no reports focusing on the cerebral blood flow and cognitive impairment in patients undergoing AF ablation. Purpose The purpose of this study was to investigate whether catheter ablation of AF would increase cerebral blood flow and restore cognitive impairment. Methods AF patients aged 75 years or older with mild or more cognitive impairment were selected. The assessment of cognitive function using Mini-Mental State Examination (MMSE) and Hasegawa's Dementia Scale-Revised (HDS-R), and measurement of cerebral blood flow using 99mTc-ECD SPECT imaging were examined before and 3 months after ablation. Results A total of 25 elderly patients (mean age 83, 14 males and 11 females) were included in this study. Of them, 23 patients had persistent AF. Twenty-three patients (92%) maintained sinus rhythm after ablation. There was a significant improvement in MMSE score (from 24.6±4.5 to 25.9±4.0, p&amp;lt;0.05) and HDS-R (from 23.2±5.5 to 24.8±5.1, p&amp;lt;0.05) after ablation. Cerebral blood flow also significantly increased after ablation (right lobe: from 34.4±4.6 to 38.5±4.4 ml/100g/min, p&amp;lt;0.01, left lobe: from 35.3±9.7 to 38.8±3.7 ml/100g/min, p&amp;lt;0.01). Overall average cerebral blood flow increased by 10.1±9.4% after ablation. There was a positive correlation between the changes in MMSE score and the changes in cerebral blood flow (r=0.65, p&amp;lt;0.05). Conclusion AF ablation in elderly patients increased cerebral blood flow and cognitive function. AF ablation would be one of the therapeutic options to improve cognitive function in elderly patients with cognitive impairment.

Intraoperative transfontanelle ultrasonography for pediatric patients.

Cerebral blood flow (CBF) plays a vital role in delivering cerebral oxygen, and the accurate assessment of CBF is crucial for the intraoperative management of critically ill infants. Although the direct measurement of CBF is challenging, CBF velocity (CBFV) can be assessed using transcranial Doppler. Recent advances in point-of-care ultrasound have introduced brain ultrasound as a feasible intraoperative option, in which transfontanelle ultrasonography (TFU) has been applied to measure the CBFV through the anterior fontanelle. However, the intraoperative application of TFU in pediatric patients remains limited. The present review highlights the procedural aspects and clinical applications of TFU for anesthetic and intensive care management in pediatric patients. TFU facilitates the visualization of cerebral vessels and allows a noninvasive assessment of cerebral hemodynamics. The clinical significance of TFU involves its usefulness in various clinical scenarios, including monitoring CBF during cardiac surgery, assessing fluid responsiveness, and estimating intracranial pressure. TFU also enables the detection of cerebral emboli and the evaluation of anatomical abnormalities such as hydrocephalus or intracranial hemorrhage. TFU has demonstrated potential as an invaluable tool in pediatric care, despite limited familiarity among anesthesiologists. Additional research is needed to explore the associations between CBF and clinical outcomes, focusing on autoregulation, the impact of physiological changes, the associations of TFU findings with other brain monitoring tools such as electroencephalography, cerebral oximetry, and the implications of microemboli. TFU is a significant advancement and valuable tool for noninvasively assessing cerebral hemodynamics and CBF in pediatric patients with open fontanelles.

I feel your pain: higher empathy is associated with higher posterior default mode network activity

Abstract Empathy is characterized as the ability to share one's experience and is associated with altruism. Previous work using blood oxygen level–dependent (BOLD) functional MRI (fMRI) has found that empathy is associated with greater activation in brain mechanisms supporting mentalizing (temporoparietal junction), salience (anterior cingulate cortex; insula), and self-reference (medial prefrontal cortex; precuneus). However, BOLD fMRI has some limitations that may not reliably capture the tonic experience of empathy. To address this, the present study used a perfusion-based arterial spin labeling fMRI approach that provides direct a quantifiable measurement of cerebral blood flow (1 mL/100 g tissue/min) and is less susceptible to low-frequency fluctuations and empathy-based “carry-over” effects that may be introduced by BOLD fMRI–based block designs. Twenty-nine healthy females (mean age = 29 years) were administered noxious heat (48°C; left forearm) during arterial spin labeling fMRI. In the next 2 fMRI scans, female volunteers viewed a stranger (laboratory technician) and their romantic partner, respectively, receive pain-evoking heat (48°C; left forearm) in real-time and positioned proximal to the scanner during fMRI acquisition. Visual analog scale (0 = “not unpleasant”; 10 = “most unpleasant sensation imaginable”) empathy ratings were collected after each condition. There was significantly (P = 0.01) higher empathy while viewing a romantic partner in pain and greater cerebral blood flow in the right temporoparietal junction, amygdala, anterior insula, orbitofrontal cortex, and precuneus when compared with the stranger. Higher empathy was associated with greater precuneus and primary visual cortical activation. The present findings indicate that brain mechanisms supporting the embodiment of another's experience is associated with higher empathy.

Measurement of Cerebral Blood Flow Using Transcranial Doppler Ultrasonography: Comparison of Two Populations of Patients on Chronic Hemodialysis

Measurement of Cerebral Blood Flow Using Transcranial Doppler Ultrasonography: Comparison of Two Populations of Patients on Chronic Hemodialysis

All-optics technique for monitoring absolute cerebral blood flow: validation against magnetic resonance imaging perfusion.

The ability to monitor cerebral blood flow (CBF) at the bedside is essential to managing critical-care patients with neurological emergencies. Diffuse correlation spectroscopy (DCS) is ideal because it is non-invasive, portable, and inexpensive. We investigated a near-infrared spectroscopy (NIRS) approach for converting DCS measurements into physiological units of blood flow. Using magnetic resonance imaging perfusion as a reference, we investigated the accuracy of absolute CBF measurements from a bolus-tracking NIRS method that used transient hypoxia as a flow tracer and hypercapnia-induced increases in CBF measured by DCS. Twelve participants (7 female, years) completed a hypercapnia protocol with simultaneous CBF recordings from DCS and arterial spin labeling (ASL). Nine participants completed the transient hypoxia protocol while instrumented with time-resolved NIRS. The estimate of baseline CBF was subsequently used to calibrate hypercapnic DCS data. Moderately strong correlations at baseline ( and ) and during hypercapnia ( and ) were found between CBF values from calibrated DCS and ASL (range 34 to ). Results demonstrated the feasibility of an all-optics approach that can both quantify CBF and perform continuous perfusion monitoring.

Brain perfusion alterations in patients and survivors of COVID‐19 infection using arterial spin labeling: A systematic review

AbstractCoronavirus disease (COVID‐19) has been shown to impact the central nervous system, leading to various neurological complications. Arterial spin labeling (ASL), a non‐invasive magnetic resonance imaging technique, enables the measurement of cerebral blood flow and perfusion abnormalities. This systematic review aims to synthesize ASL findings in patients with COVID‐19 and assess the potential role of ASL in diagnosing and managing neurological complications. A comprehensive search was conducted on PubMed and Scopus for studies related to ASL in individuals with COVID‐19 or post‐COVID‐19 syndrome published between December 2019 and August 2024. Extracted data encompassed study characteristics, ASL protocols, cognitive assessments, and principal findings. The most consistent observation across studies was hypoperfusion detected in various brain regions, particularly within the frontal lobes, which may correlate with cognitive impairment and olfactory dysfunction. Additionally, some investigations reported hyperperfusion localized to the leptomeninges. These results may reflect underlying mechanisms such as hypoxic–ischemic injury, inflammation, vascular dysfunction, and neuronal damage attributable to COVID‐19. In conclusion, ASL has emerged as a valuable tool for evaluating brain perfusion among patients affected by or recovering from COVID‐19 since it offers critical insights into cerebral hemodynamics and metabolism. Further research is warranted to validate these ASL findings and elucidate whether post‐COVID‐19 syndrome contributes to persistent brain perfusion issues.

Sex Disparities in Mortality After Endovascular Therapy in Large Core Infarcts

Background In recent large core endovascular therapy (EVT) trials of large vessel occlusion acute ischemic stroke (AIS), treatment was associated with reduced rates of mortality. Because post‐AIS mortality can be influenced by societal and biological factors that differ between women and men, we investigate sex‐based differences in mortality outcomes following EVT in large core AIS. Methods From our prospectively collected multicenter registry across 4 comprehensive stroke centers in the Greater Houston area, we identified patients from 2017 to 2022 with large vessel occlusion AIS and large infarct core. Large infarct core was defined by computed tomography perfusion exceeding 70 mL (by regional cerebral blood flow measurements using automated postprocessing) or computed tomography Alberta Stroke Program Early CT [Computed Tomography] Score&lt;6. The primary outcome of this study was the likelihood of mortality at 90 days, determined through multivariable logistic regression adjusted for EVT, sex, and EVT/sex interaction term. Secondary outcomes included 90‐day disability outcomes and intracerebral hemorrhage. Results Among 190 patients who met inclusion criteria, 50% were female and 45.3% received EVT. Demographic differences between the sexes were largely balanced apart from the older age of presentation for women compared with men (75 versus 67, women versus men; P &lt;0.01). In univariable analysis, women who did not receive EVT had greater mortality (27.4% difference; P &lt;0.001) compared with men, with comparable rates in EVT‐treated cohorts. In multivariable analysis, non‐EVT management was strongly associated with mortality in women compared with men at discharge (odds ratio [OR] 5.81, 95% CI [1.96–17.23]) and 90‐days (OR 6.77, 95% CI [2.09–21.94]). In the secondary analysis, which additionally adjusted the model for age and National Institutes of Health Stroke Scale score, these findings were unchanged. The sex/EVT interaction term showed significant interaction for mortality both at discharge and 90 days ( P &lt;0.01). Conclusion EVT in large core AIS populations may disparately reduce mortality in women compared to men.

Noninvasive Monitoring of Changes in Cerebral Hemodynamics During Prolonged Field Care for Hemorrhagic Shock and Hypoxia-Induced Injuries With Portable Diffuse Optical Sensors.

Achieving simultaneous cerebral blood flow (CBF) and oxygenation measures, specifically for point-of-care injury monitoring in prolonged field care, requires the implementation of appropriate methodologies and advanced medical device design, development, and evaluation. The near-infrared spectroscopy (NIRS) method measures the absorbance of light whose attenuation is related to cerebral blood volume and oxygenation. By contrast, diffuse correlation spectroscopy (DCS) allows continuous noninvasive monitoring of microvascular blood flow by directly measuring the degree of light scattering because of red blood cell (RBC) movement in tissue capillaries. Hence, this study utilizes these two optical approaches (DCS-NIRS) to obtain a more complete hemodynamic monitoring by providing cerebral microvascular blood flow, hemoglobin oxygenation and deoxygenation in hemorrhage, and hypoxia-induced injuries. Piglet models of hemorrhage and hypoxia-induced brain injury were used with DCS and NIRS sensors placed over the preorbital to temporal skull regions. To induce hemorrhagic shock, up to 70% of the animal's total blood volume was withdrawn through graded hemorrhage serially via a syringe from a femoral artery cannula in 10 mL/kg aliquots over 1 minute every 10 minutes. A second group of animals was subjected to hypoxia for ∼1 hour through graded hypoxia by serial titration from normoxic fraction inspired oxygen of 21% to hypoxic fraction inspired oxygen of 6%. A subset of animals served as sham-controls undergoing anesthesia, instrumentation, and ventilation as the injury groups, yet experiencing no blood loss or hypoxia. We first investigated the relationship between hemorrhagic shock and no shock by using measured biomarkers, including blood flow index from DCS associated with CBF and oxygenated (HbO) and de-oxygenated hemoglobin from NIRS. The statistical analysis revealed a significant difference between no shock and hemorrhagic shock (P < .01). The HbO decreased with each blood loss as expected, yet the de-oxygenated hemoglobin was slightly changed. During hypoxia-induced global hypoxic-ischemic injury tests, the CBF results from graded hypoxia were consistent with the response previously measured during hemorrhagic shock. Moreover, HbO decreased when the animal was hypoxic, as expected. A statistical analysis was also conducted to compare the results with those of the sham controls. There is a consistency in blood flow measures in both injury mechanisms (hemorrhagic shock and hypoxia), which is significant as the new prototype system provides similar measures and trends for each brain injury type, suggesting that the optical system can be used in response to different injury mechanisms. Notably, the results support the idea that this optical system can probe the hemodynamic status of local cerebral cortical tissue and provide insight into the underlying changes of cerebral tissue perfusion at the microvascular level. These measurement capabilities can improve shock identification and monitoring of medical management of injuries, particularly hemorrhagic shock, in prolonged field care.

A generalized signal model for dual-module velocity-selective arterial spin labeling.

To develop a generalized signal model for dual-module velocity-selective arterial spin labeling (dm-VSASL) that can integrate arbitrary saturation and inversion profiles. A recently developed mathematical framework for single-module VSASL is extended to address the increased complexity of dm-VSASL and to model the use of realistic velocity-selective profiles in the label-control and vascular crushing modules. Expressions for magnetization difference, arterial delivery functions, labeling efficiency, and cerebral blood flow (CBF) estimation error are presented. Sources of error are examined and timing requirements to minimize quantification errors are derived. For ideal velocity-selective profiles, the predicted signals match those of prior work. With realistic profiles, a CBF-dependent estimation error can occur when velocity-selective inversion (VSI) is used for the labeling modules and velocity-selective saturation (VSS) is used for the vascular crushing module. The error reflects a mismatch between the leading and trailing edges of the delivery function for the second bolus and can be minimized by choosing a nominal labeling cutoff velocity that is lower than the nominal saturation cutoff velocity. In the presence of and inhomogeneities, the labeling efficiency of dual-module VSI is more attenuated than that of dual-module VSS. The proposed signal model will enable researchers to more accurately assess and compare the performance of realistic dm-VSASL implementations and improve the quantification of dm-VSASL CBF measures.

Shifting concepts of autoregulation: Commentary to ‘Static autoregulation in humans'

Advances in imaging techniques have transformed our understanding of cerebral autoregulation. Older imaging techniques provided measurements of cerebral blood flow (CBF) that reflected the average CBF over a window of 10–20 minutes. A key finding, dating back to 1959, was that CBF remained more or less stable over a remarkably wide range of changes in blood pressure. Modern techniques can measure changes in CBF within the time frame of a heartbeat. They have revealed, paradoxically, a remarkable instability of CBF. This commentary attempts to reconcile these seemingly contradictory observations.

Simultaneous and cumulative effects of tDCS on cerebral metabolic rate of oxygen in multiple sclerosis.

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique with simultaneous (during stimulation) and cumulative effects (after repeated sessions) on blood flow and neuronal metabolism. These effects remain mostly unclear especially in multiple sclerosis (MS). This work aims to elucidate brain metabolic and hemodynamic underpinnings of tDCS and its potential therapeutic impact in MS patients using quantitative tDCS-MRI. MS participants (n = 20; age = 45.4 ± 12.3 years, 7 males) underwent 3 T MRI scans before and after 20 daily sessions of dorsolateral prefrontal cortex (DLFPC) tDCS (2.0 mA, left anodal) paired with adaptive cognitive training (aCT). During both visits, imaging measurements of cerebral blood flow (CBF), cerebral venous blood oxygenation (Yv) and calculated cerebral metabolic rate of oxygen (CMRO2) were obtained at pre-tDCS, during-tDCS and post-tDCS. At baseline, significant increase from pre- to during-tDCS was observed in CMRO2 (7.6%; p = 0.002), CBF (11.0%; p < 0.0001) and Yv (1.9%; p = 0.006). At follow up, we observed an increase in pre-tDCS CMRO2 (140.59 ± 13.83 μmol/100 g/min) compared to baseline pre-tDCS levels (128.30 ± 14.00 μmol/100 g/min; p = 0.006). Sustained elevations in CMRO2 and CBF into post-tDCS were also observed (tDCS lingering effects). Cumulative tDCS effects were observed in the form of sustained elevations in CMRO2 and CBF in pre-tDCS follow up, reaching the magnitudes measured at baseline during-tDCS. TDCS induces an acute surge in metabolic activity persisting immediately after the stimulation is removed. Moreover, treatment composed of repeated tDCS-aCT paired sessions contributes to establishing long-lasting increases in neuronal activity.

Differentiation Between High-Grade Glioma and Brain Metastasis Using Cerebral Perfusion-Related Parameters (Cerebral Blood Volume and Cerebral Blood Flow): A Systematic Review and Meta-Analysis of Perfusion-weighted MRI Techniques.

Distinguishing high-grade gliomas (HGGs) from brain metastases (BMs) using perfusion-weighted imaging (PWI) remains challenging. PWI offers quantitative measurements of cerebral blood flow (CBF) and cerebral blood volume (CBV), but optimal PWI parameters for differentiation are unclear. To compare CBF and CBV derived from PWIs in HGGs and BMs, and to identify the most effective PWI parameters and techniques for differentiation. Systematic review and meta-analysis. Twenty-four studies compared CBF and CBV between HGGs (n = 704) and BMs (n = 488). Arterial spin labeling (ASL), dynamic susceptibility contrast (DSC), dynamic contrast-enhanced (DCE), and dynamic susceptibility contrast-enhanced (DSCE) sequences at 1.5 T and 3.0 T. Following the PRISMA guidelines, four major databases were searched from 2000 to 2024 for studies evaluating CBF or CBV using PWI in HGGs and BMs. Standardized mean difference (SMD) with 95% CIs was used. Risk of bias (ROB) and publication bias were assessed, and I2 statistic was used to assess statistical heterogeneity. A P-value<0.05 was considered significant. HGGs showed a significant modest increase in CBF (SMD = 0.37, 95% CI: 0.05-0.69) and CBV (SMD = 0.26, 95% CI: 0.01-0.51) compared with BMs. Subgroup analysis based on region, sequence, ROB, and field strength for CBF (HGGs: 375 and BMs: 222) and CBV (HGGs: 493 and BMs: 378) values were conducted. ASL showed a considerable moderate increase (50% overlapping CI) in CBF for HGGs compared with BMs. However, no significant difference was found between ASL and DSC (P = 0.08). ASL-derived CBF may be more useful than DSC-derived CBF in differentiating HGGs from BMs. This suggests that ASL may be used as an alternative to DSC when contrast medium is contraindicated or when intravenous injection is not feasible. Stage 2.

Identification of toll-like receptor 2 as a key regulator of neuronal apoptosis in vascular dementia by bioinformatics analysis and experimental validation

BackgroundVascular dementia (VaD), the second most prevalent type of dementia, lacks a well-defined cause and effective treatment. Our objective was to utilize bioinformatics analysis to discover the fundamental disease-causing genes and pathological mechanisms in individuals diagnosed with VaD. MethodsTo identify potential pathogenic genes associated with VaD, we conducted weighted gene co-expression network analysis (WGCNA), differential expression analysis, and protein–protein interaction (PPI) analysis. The exploration of potential biological mechanisms involved the utilization of Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis. Moreover, a bilateral common carotid artery stenosis (BCAS) mouse model of VaD was established, and the expression of the hub gene, its relationship with cognitive function and its potential pathogenic mechanism were verified by cognitive behavior tests, cerebral blood flow measurement, Western blotting, and immunofluorescence experiments. ResultsThis study identified 293 DEGs from the brain cortex of VaD patients and healthy controls, among these genes, the Toll-like receptor 2 (TLR2) gene was identified as hub gene, and it was associated with the apoptosis-related pathway PI3K/AKT.The BCAS model demonstrated that the use of TLR2 inhibitors greatly enhanced the cognitive function of the mice (p < 0.05). Additionally, there was a notable decrease in the number of apoptotic cells in the brain cortex of the mice (p < 0.01). Moreover, significant alterations in the levels of proteins related to the PI3K/AKT pathway and cleaved-caspase3 proteins were detected (p < 0.05). ConclusionsTLR2 plays a role in the pathophysiology of VaD by enhancing the neuronal apoptotic pathway, suggesting it could be a promising therapeutic target.

Multi-Tracer Studies of Brain Oxygen and Glucose Metabolism Using a Time-of-Flight Positron Emission Tomography - Computed Tomography Scanner.

The authors have developed a paradigm using positron emission tomography (PET) with multiple radiopharmaceutical tracers that combines measurements of cerebral metabolic rate of glucose (CMRGlc), cerebral metabolic rate of oxygen (CMRO2), cerebral blood flow (CBF), and cerebral blood volume (CBV), culminating in estimates of brain aerobic glycolysis (AG). These in vivo estimates of oxidative and non-oxidative glucose metabolism are pertinent to the study of the human brain in health and disease. The latest positron emission tomography-computed tomography (PET-CT) scanners provide time-of-flight (TOF) imaging and critical improvements in spatial resolution and reduction of artifacts. This has led to significantly improved imaging with lower radiotracer doses. Optimized methods for the latest PET-CT scanners involve administering a sequence of inhaled 15O-labeled carbon monoxide (CO) and oxygen (O2), intravenous 15O-labeled water (H2O), and 18F-deoxyglucose (FDG)-all within 2-h or 3-h scan sessions that yield high-resolution, quantitative measurements of CMRGlc, CMRO2, CBF, CBV, and AG. This methods paper describes practical aspects of scanning designed for quantifying brain metabolism with tracer kinetic models and arterial blood samples and provides examples of imaging measurements of human brain metabolism.

Study of Time-Resolved Dynamics in Turbid Medium Using a Single-Cavity Dual-Comb Laser.

In measuring cerebral blood flow (CBF) noninvasively using optical techniques, diffusing-wave spectroscopy is often combined with near-infrared spectroscopy to obtain a reliable blood flow index. Measuring the blood flow index at a determined depth remains the ultimate goal. In this study, we present a simple approach using dual-comb lasers where we simultaneously measure the absorption coefficient (μa), the reduced scattering coefficient (μs '), and dynamic properties. This system can also effectively differentiate dynamics from various depths, which is crucial for analyzing multilayer dynamics. For CBF measurements, this capability is particularly valuable as it helps mitigate the influence of the scalp and skull, thereby enhancing the specificity of deep tissue.