Arterial Spin Labeling Research Articles

Exploring the Impact of Hemoglobin on Cerebral Blood Flow in Arterial Territories and Surgical Outcomes: Potential Implications for Moyamoya Disease Treatment.

Changes in levels of hemoglobin would result in alterations of cerebral blood flow (CBF). However, the impact of hemoglobin on CBF in moyamoya disease (MMD) remains largely unknown. This study sought to determine whether CBF would be influenced by hemoglobin before surgical revascularization and to analyze the relationships between hemoglobin and CBF with clinical outcome after surgery in patients with MMD. We prospectively enrolled adult patients with MMD undergoing surgical revascularization between June 2020 and December 2022. Preoperative CBF was measured in the territories of anterior, middle, and posterior cerebral arteries (ACA, MCA, and PCA, respectively) using 3-dimensional pseudo-continuous arterial spin labeling magnetic resonance imaging. Clinical outcome at 1 year after surgery was evaluated using the modified Rankin Scale. A total of 60 patients with MMD were included, with 25% (n=15) experiencing unfavorable outcomes. Patients with MMD exhibited lower CBF (ACA: P=0.007; MCA: P<0.001; PCA: P=0.014), compared with healthy controls (n=40). Hemoglobin was negatively and significantly associated with CBF (ACA: β=-0.45, P<0.001; MCA: β=-0.38, P<0.001; PCA: β=-0.54, P<0.001). CBF rather than hemoglobin was significantly related with clinical outcome (ACA: P<0.001; MCA: P<0.001; PCA: P=0.001), and CBF showed high discrimination in predicting clinical outcome (ACA: area under the curve, 0.84; MCA: area under the curve, 0.84; PCA: area under the curve, 0.80). Our findings demonstrate that hemoglobin significantly influences CBF, and CBF has a high predictive value for clinical outcome in MMD. The optimal hemoglobin level before surgical revascularization should be further investigated.

Cerebral perfusion in patients with unilateral internal carotid artery occlusion by dual post-labeling delays arterial spin labeling imaging.

Global and regional cerebral blood flow (CBF) changes in patients with unilateral internal carotid artery occlusion (ICAO) are unclear when the dual post-labeling delays (PLD) arterial spin labeling (ASL) magnetic resonance imaging (MRI) technique is used. Manual delineation of regions of interest for CBF measurement is time-consuming and laborious. To assess global and regional CBF changes in patients with unilateral ICAO with the ASL-MRI perfusion technique. Twenty hospitalized patients with ICAO and sex- and age-matched controls were included in the study. Regional CBF was measured by Dr. Brain's ASL software. The present study evaluated differences in global, middle cerebral artery (MCA) territory, anterior cerebral artery territory, and Alberta Stroke Program Early Computed Tomography Score (ASPECTS) regions (including the caudate nucleus, lentiform nucleus, insula ribbon, internal capsule, and M1-M6) and brain lobes (including frontal, parietal, temporal, and insular lobes) between ICAO patients and controls at PLD 1.5 s and PLD 2.5 s. When comparing CBF between ICAO patients and controls, the global CBF in ICAO patients was lower at both PLD 1.5 s and PLD 2.5 s; the CBF on the occluded side was lower in 15 brain regions at PLD 1.5 s, and it was lower in 9 brain regions at PLD 2.5 s; the CBF in the contralateral hemisphere was lower in the caudate nucleus and internal capsule at PLD 1.5 s and in M6 at PLD 2.5 s. The global CBF in ICAO patients was lower at PLD 1.5 s than at PLD 2.5 s. The ipsilateral CBF at PLD 1.5 s was lower than that at PLD 2.5 s in 15 regions, whereas the contralateral CBF was lower at PLD 1.5 s than at PLD 2.5 s in 12 regions. The ipsilateral CBF was lower than the contralateral CBF in 15 regions at PLD 1.5 s, and in M6 at PLD 2.5 s. Unilateral ICAO results in hypoperfusion in the global and MCA territories, especially in the ASPECTS area. Dual PLD settings prove more suitable for accurate CBF quantification in ICAO.

Arterial spin labeling detects trapped labeled spins in flow-diverted aneurysms and it reflects intra-aneurysmal flow stasis.

This study evaluated arterial spin labeling (ASL) imaging findings in flow-diverted aneurysms (FD-ANs). Twenty-one patients with internal carotid artery aneurysms treated with flow-diverter stent (FDS) were included. Time-of-flight magnetic resonance angiography (TOF-MRA) and ASL were performed before and after follow-up digital subtraction angiography (DSA) on the day, 6 months, and/or 1 year after treatment. Two radiologists rated the clarity of the depiction of FD-ANs for MRA on a 3-point scale and the ASL signal intensity of the aneurysm as negative or positive. A neurosurgeon assessed DSA findings using the O'Kelly-Marotta (OKM) grading scale, categorizing them into filling and stasis grades. The 23 examinations were classified according to the OKM grading scale, and the proportion of ASL-positive cases and the proportion of cases with MRA scores of 1-2 (detectable) were calculated for each grade. The relationship between the OKM grading scale and ASL positivity or MRA detectable was examined using Fisher's exact test. Of seven examinations where the statis grade was 1 or 2, no examinations showed ASL positivity. However, among the 16 examinations in which the stasis grade was 3, 9 examinations showed ASL positivity. A significant association was observed between stasis grade and ASL positivity (p = 0.035). In contrast, no significant relationship was observed between the OKM grading scale and the MRA 3-point scale. High-signal ASL in FD-ANs could reflect stasis within the aneurysm; therefore, noninvasive ASL can indicate reduction in intra-aneurysmal blood flow after treatment and reperfusion during posttreatment observation.

Possible association of elevated CSF IL-6 levels with anxiety and frustration in psychiatric disorders.

Neuroinflammation is an important causal factor for a variety of psychiatric disorders. We previously reported increased cerebrospinal fluid interleukin-6 levels in patients with schizophrenia and major depressive disorder. The present study aimed to examine the possible association of interleukin-6 levels with anxiety and frustration, negative valence symptoms shared in various psychiatric disorders. We included 129 patients with psychiatric disorders and 70 controls. CSF and plasma interleukin-6 levels were measured by immunoassay kits, and psychological symptoms were assessed with the State-Trait Anxiety Inventory, and the Basic Psychological Need Satisfaction and Frustration Scale. To examine regional cerebral blood flow, patients underwent arterial spin labeling analysis using magnetic resonance imaging. Cerebrospinal fluid interleukin-6 levels were significantly correlated with State-Trait Anxiety Inventory-trait anxiety (r = 0.25, P = 0.046) and Basic Psychological Need Satisfaction and Frustration Scale-autonomy frustration scores (r = 0.29, P = 0.018). Patients with abnormally high cerebrospinal fluid interleukin-6 levels (defined >97.5 percentile of the controls) had higher scores for trait anxiety (P = 0.035) and autonomy frustration (P = 0.026), and significantly increased regional cerebral blood flow in the left superior temporal gyrus, bilateral nucleus accumbens, and cerebellum than the remaining patients. Patients with elevated cerebrospinal fluid interleukin-6 constitute a subpopulation of psychiatric disorders associated with anxiety and autonomy frustration, which may be related to altered functions in specific brain areas.

Measurement and modeling of xenon gas transfer in the human brain with 1H and hyperpolarized 129Xe MRI

BackgroundThe feasibility of imaging hyperpolarized 129Xe dissolved in brain tissue following inhalation of xenon gas in the lungs has recently been demonstrated in humans. The image contrast in 129Xe brain MRI represents a combination of factors, including regional perfusion, polarization decay and gas transfer rate across the blood-brain barrier. PurposeTo investigate the repeatability of hyperpolarized 129Xe brain MRI in healthy normal individuals and to identify the dominant mechanisms of image contrast by assessing voxel-wise correlation between HP 129Xe brain MRI and models of 129Xe brain uptake derived from 1H arterial spin labeling (ASL) perfusion mapping. Materials and MethodsTo assess repeatability, 3 sets of hyperpolarized 129Xe brain images were acquired from 5 healthy volunteers. Quantitative maps of the human brain, including cerebral blood flow, volume and predicted xenon uptake, were derived from 1H arterial spin labeling and T2-weighted MRI. These maps were then spatially cross-correlated with hyperpolarized 129Xe brain MRI. ResultsSignal to noise ratios of 8.7–17.7 were observed across volunteers for a voxel size of 8 × 8 × 50 mm3 with intra-subject repeatability of between 6 and 29 %. Hyperpolarized 129Xe brain images showed voxel-wise correlations with cerebral blood flow (R = 0.32 to 0.62), volume (R = 0.33 to 0.63) and predicted xenon uptake (R = 0.34 to 0.63), but did not correlate with arterial transit time (R = 0.05 to 0.26). ConclusionVoxel-wise cross correlation between 129Xe and 1H ASL suggests that the regional quantity of dissolved xenon delivered by cerebral blood flow is the dominant mechanism of image contrast in HP 129Xe brain MRI, assuming normal blood-brain barrier function. Combining 1H and 129Xe brain MRI provides new opportunities to quantitatively investigate brain pathophysiology and function.

Alterations of perfusion and functional connectivity of the cingulate motor area are associated with psychomotor retardation in major depressive disorder

AbstractPsychomotor retardation, characterized by slowing of speech, thoughts, and a decrease of movements, is frequent in patients with major depressive disorder (MDD). However, its neurobiological correlates are still poorly understood. This study aimed to explore if cerebral blood flow (CBF) and resting state functional connectivity (rs-FC) of the motor network are altered in patients with MDD and if these changes are associated with psychomotor retardation. Thirty-six right-handed patients with depression and 19 right-handed healthy controls (HC) that did not differ regarding age and sex underwent arterial spin labelling (ASL) and resting-state functional MRI (rs-fMRI) scans. Psychomotor retardation was assessed with the motoric items of the core assessment of psychomotor change (CORE) questionnaire. Patients with MDD had more pronounced psychomotor retardation scores than HC. Patients with MDD had reduced CBF in bilateral cingulate motor area (CMA) and increased resting-state functional connectivity (rs-FC) between the cluster in the CMA and a cluster localized in bilateral supplementary motor areas (SMA). Furthermore, increased rs-FC between the CMA and the left SMA was associated with more pronounced psychomotor retardation. Our results suggest that reduced perfusion of the CMA and increased rs-FC between the CMA and the SMA are associated with psychomotor retardation in patients with depression.

Determinants of cerebral blood flow and arterial transit time in healthy older adults.

Cerebral blood flow (CBF) and arterial transit time (ATT), markers of brain vascular health, worsen with age. The primary aim of this cross-sectional study was to identify modifiable determinants of CBF and ATT in healthy older adults (n = 78, aged 60-81 years). Associations between cardiorespiratory fitness and CBF or ATT were of particular interest because the impact of cardiorespiratory fitness is not clear within existing literature. Secondly, this study assessed whether CBF or ATT relate to cognitive function in older adults. Multiple post-labelling delay pseudo-continuous arterial spin labelling estimated resting CBF and ATT in grey matter. Results from multiple linear regressions found higher BMI was associated with lower global CBF (β = -0.35, P = 0.008) and a longer global ATT (β = 0.30, P = 0.017), global ATT lengthened with increasing age (β = 0.43, P = 0.004), and higher cardiorespiratory fitness was associated with longer ATT in parietal (β = 0.44, P = 0.004) and occipital (β = 0.45, P = 0.003) regions. Global or regional CBF or ATT were not associated with processing speed, working memory, or attention. In conclusion, preventing excessive weight gain may help attenuate age-related declines in brain vascular health. ATT may be more sensitive to age-related decline than CBF, and therefore useful for early detection and management of cerebrovascular impairment. Finally, cardiorespiratory fitness appears to have little effect on CBF but may induce longer ATT in specific regions.

Elevated cerebral perfusion in neonatal encephalopathy is associated with neurodevelopmental impairments.

Neonatal encephalopathy (NE) represents a primary cause of neonatal death and neurodevelopmental impairments. In newborns with NE, cerebral hyperperfusion is related to an increased risk of severe adverse outcomes, but less is known about the link between perfusion and mild to moderate developmental impairments or developmental delay. Using arterial spin labelling perfusion MRI, we investigated the link between perfusion in 36 newborns with NE and developmental outcome at 2 years. 53% of the infants demonstrated a normal outcome at 24 months, while two had cerebral palsy with impairments in cognitive, motor, and language domains, and three infants died. The remaining infants showed mild or moderate delays in development in one or two domains. Hyperperfusion across the whole brain was associated with more adverse outcome, including an increased risk of death or severe disability such as cerebral palsy. Among the surviving infants, higher perfusion in the bilateral basal ganglia, thalamus, hippocampus and cerebellum during the neonatal period was related to a poorer cognitive outcome at 2 years. Hyperperfusion in infants with NE was associated with a more adverse outcome and lower cognitive outcome scores. In addition to severe adverse outcomes, altered perfusion is also related to mild to moderate impairment following HIE. Neonates with neonatal encephalopathy (NE) show increased cerebral perfusion globally, which is linked to a more adverse outcome. Higher perfusion in the bilateral basal ganglia, thalamus, hippocampus and cerebellum during the neonatal period was related to a poorer cognitive outcome at 2 years. In addition to severe adverse outcomes altered perfusion is related to mild to moderate impairment following NE. To improve neurodevelopmental outcomes, it is important to improve our understanding of the factors influencing cerebral perfusion in infants with NE.

A Systematic Review of Air Pollution Exposure and Brain Structure and Function during Development.

Air pollutants are known neurotoxicants. In this updated systematic review, we evaluate new evidence since our 2019 systematic review on the effect of outdoor air pollution exposure on childhood and adolescent brain structure and function as measured by magnetic resonance imaging (MRI). Using PubMed and Web of Science, we conducted an updated literature search and systematic review of articles published through March 2024, using key terms for air pollution and functional and/or structural MRI. Two raters independently screened all articles using Covidence and implemented the risk of bias instrument for systematic reviews informing the World Health Organization Global Air Quality Guidelines. We identified 222 relevant papers, and 14 new studies met our inclusion criteria. Including six studies from our 2019 review, the 20 publications to date include study populations from the United States, Netherlands, Spain, and United Kingdom. Studies investigated exposure periods spanning pregnancy through early adolescence, and estimated air pollutant exposure levels via personal monitoring, geospatial residential estimates, or school courtyard monitors. Brain MRI occurred when children were on average 6-14.7 years old; however, one study assessed newborns. Several MRI modalities were leveraged, including structural morphology, diffusion tensor imaging, restriction spectrum imaging, arterial spin labeling, magnetic resonance spectroscopy, as well as resting-state and task-based functional MRI. Air pollutants were associated with widespread brain differences, although the magnitude and direction of findings are largely inconsistent, making it difficult to draw strong conclusions. Prenatal and childhood exposure to outdoor air pollution is associated with structural and functional brain variations. Compared to our initial 2019 review, publications doubled-an increase that testifies to the importance of this public health issue. Further research is needed to clarify the effects of developmental timing, along with the downstream implications of outdoor air pollution exposure on children's cognitive and mental health.

Detectability of white matter cerebral blood flow using arterial spin labeling MRI in patients with sickle cell disease: Relevance of flow territory, bolus arrival time, and hematocrit.

Sickle cell disease (SCD) is the most common genetic blood disorder, characterized by red cell hemolysis, anemia, and corresponding increased compensatory cerebral blood flow (CBF). SCD patients are at high risk for cerebral infarcts and CBF quantification is likely critical to assess infarct risk. Infarcts primarily localize to white matter (WM), yet arterial spin labeling (ASL) MRI, the most common non-invasive CBF approach, has poor WM CBF sensitivity owing to low WM CBF and long WM bolus arrival time (BAT). We hypothesize that anemia, and associated cerebral hyperemia, in SCD leads to improved WM detection with ASL. We performed 3-Tesla multi-delay pulsed ASL in SCD (n = 35; age = 30.5 ± 8.3 years) and control (n = 15; age = 28.7 ± 4.5 years) participants and applied t-tests at each inversion time within different flow territories, and determined which regions were significantly above noise floor (criteria: one-sided p < 0.05). Total WM CBF-weighted signal was primarily detectable outside of borderzone regions in SCD (CBF = 17.7 [range = 12.9-25.0] mL/100 g/min), but was largely unphysiological in control (CBF = 8.1 [range = 7.6-9.9)] mL/100 g/min) participants. WM BAT was reduced in SCD versus control participants (ΔBAT = 37 [range = 46-70] ms) and BAT directly correlated with hematocrit (Spearman's-ρ = 0.62; p < 0.001). Findings support the feasibility of WM CBF quantification using ASL in SCD participants for appropriately parameterized protocols.

Comprehensive MRI assessment reveals subtle brain findings in non-hospitalized post-COVID patients with cognitive impairment.

Impaired cognitive ability is one of the most frequently reported neuropsychiatric symptoms in the post-COVID phase among patients. It is unclear whether this condition is related to structural or functional brain changes. In this study, we present a multimodal magnetic resonance imaging study of 36 post-COVID patients and 36 individually matched controls who had a mild form of severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) infection from March 2020 to February 2022. This study aimed to investigate structural and functional brain alterations and their correlation with post-COVID symptoms and neurocognitive functions. The study protocol comprised an assessment of physical fatigue [Fatigue Severity Scale (FSS)], mental fatigue (Mental Fatigue Scale (MFS)], depression [Montgomery Asberg Depression Rating Scale (MADRS)], anxiety [Hospital Anxiety and Depression Scale (HAD)], post-COVID Symptoms Severity Score, and neurocognitive status [Repeatable Battery for the Assessment of Neuropsychological Status Update (RBANS)]. The magnetic resonance imaging protocol included morphological sequences, arterial spin labeling (ASL) and dynamic susceptibility contrast-enhanced (DSC) perfusion, diffusion tensor imaging (DTI), and resting-state functional magnetic resonance imaging (fMRI) sequences. Using these protocols, the assessments of macrostructural abnormalities, perfusion, gray matter density, white matter integrity, and brain connectivity were performed. Post-COVID patients had higher levels of physical fatigue, mental fatigue, depression, and anxiety than controls and showed cognitive impairment in all the RBANS domains except in Visuospatial/Construction. The subjective mental fatigue correlated with objective impaired cognitive ability in the RBANS test, particularly in the Attention domain. There were no differences between patients and controls regarding macrostructural abnormalities, regional volumes, regional perfusion metrics, gray matter density, or DTI parameters. We observed a significant positive correlation between RBANS Total Scale Index score and gray matter volume in the right superior/middle-temporal gyrus (p < 0.05) and a significant negative correlation between the white matter integrity and post-COVID symptoms (p < 0.05) in the same area. The connectivity differences were observed between patients and controls in a few regions, including the right middle frontal gyrus, an important area of convergence of the dorsal and ventral attention networks. We also noted a positive correlation between post-COVID symptoms and increased connectivity in the right temporoparietal junction, which is part of the ventral attention system. In non-hospitalized subjects with post-COVID, we did not find any structural brain changes or changes in perfusion, compared to controls. However, we noted differences in connectivity within an important area for attention processes, which may be associated with post-COVID brain fog.

Hypertension and cerebral blood flow in the development of Alzheimer's disease.

We investigated the interactive associations between amyloid and hypertension on the entorhinal cortex (EC) tau and atrophy and the role of cerebral blood flow (CBF) as a shared mechanism by which amyloid and hypertension contribute to EC tau and regional white matter hyperintensities (WMHs). We analyzed data from older adults without dementia participating in the Add-Tau study (NCT02958670, n=138) or Alzheimer's Disease Neuroimaging Initiative (ADNI) (n=523) who had available amyloid-positron emission tomography (PET), tau-PET, fluid-attenuated inversion recovery (FLAIR), and T1-weighted magnetic resonance imaging (MRI). A subsample in both cohorts had available arterial spin labeling (ASL) MRI (Add-Tau: n=78; ADNI: n=89). The detrimental effects of hypertension on AD pathology and EC thickness were more pronounced in the Add-Tau cohort. Increased amyloid burden was associated with decreased occipital gray matter CBF in the ADNI cohort. In both cohorts, lower regional gray matter CBF was associated with higher EC tau and posterior WMH burden. Reduced cerebral perfusion may be one common mechanism through which hypertension and amyloid are related to increased EC tau and WMH volume. Hypertension is associated with increased entorhinal cortex (EC) tau, particularly in the presence of amyloid. Decreased cortical cerebral blood flow (CBF) is associated with higher regional white matter hyperintensity volume. Increasing amyloid burden is associated with decreasing CBF in the occipital lobe. MTL CBF and amyloid are synergistically associated with EC tau.

Measurement of blood-brain barrier water exchange rate using diffusion-prepared and multi-echo arterial spin labelling: Comparison of quantitative values and age dependence.

Water exchange rate (Kw) across the blood-brain barrier (BBB) is an important physiological parameter that may provide new insight into ageing and neurodegenerative disease. Recently, two non-invasive arterial spin labelling (ASL) MRI methods have been developed to measure Kw, but results from the different methods have not been directly compared. Furthermore, the association of Kw with age for each method has not been investigated in a single cohort. Thirty participants (70% female, 63.8 ± 10.4years) were scanned at 3T with Diffusion-Prepared ASL (DP-ASL) and Multi-Echo ASL (ME-ASL) using previously implemented acquisition and analysis protocols. Grey matter Kw, cerebral blood flow (CBF) and arterial transit time (ATT) were extracted. CBF values were consistent; approximately 50 ml/min/100 g for both methods, and a strong positive correlation in CBF from both methods across participants (r = 0.82, p < 0.001). ATT was significantly different between methods (on average 147.7ms lower when measured with DP-ASL compared to ME-ASL) but was positively correlated across participants (r = 0.39, p < 0.05). Significantly different Kw values of 106.6±19.7min-1 and 306.8±71.7min-1 were measured using DP-ASL and ME-ASL, respectively, and DP-ASL Kw and ME-ASL Kw were negatively correlated across participants (r = -0.46, p < 0.01). Kw measured using ME-ASL had a significant linear relationship with age (p < 0.05). In conclusion, DP-ASL and ME-ASL provided estimates of Kw with significantly different quantitative values and inconsistent dependence with age. We propose future standardisation of modelling and fitting methods for DP-ASL and ME-ASL, to evaluate the effect on Kw quantification. Also, sensitivity and bias analyses should be performed for both approaches, to assess the effect of varying acquisition and fitting parameters. Lastly, comparison with independent measures of BBB water transport, and with physiological and clinical biomarkers known to be associated with changes in BBB permeability, are essential to validate the ASL methods, and to demonstrate their clinical utility.

Magnetic resonance imaging patterns and perfusion changes of posterior reversible encephalopathy syndrome in children with clinical outcome correlation.

Posterior reversible encephalopathy syndrome (PRES) in children has a propensity towards atypical features on magnetic resonance (MR) imaging, with limited literature on perfusion changes and clinicoradiological correlation. We aimed to comprehensively study MR imaging patterns of pediatric PRES, including cerebral blood flow variations on arterial spin labeling, and looked for any MR biomarkers of poor clinical outcome. In this retrospective observational study conducted in a tertiary hospital setting, MR records over a 4-year period (May 2019 to May 2023) were systematically searched along with their clinical details. Patients with an age less than 18years and a clinicoradiological constellation consistent with PRES were included. MR scans were analyzed by two neuroradiologists with 8years' and 10years' experience. Association was sought with poor clinical outcome (defined as modified Rankin Scale score at discharge of > 2). A total of 45 patients (29 boys) were included in the study, with a mean age (± standard deviation) of 11.19 (± 4.53) years. On MR imaging, 95.6% of patients (n = 43) showed atypical features and/or atypical areas of involvement. The superior frontal sulcus (n = 18) was the most predominant MR pattern, and cerebellar involvement was not uncommon (n = 15). Unilateral involvement (n = 3), isolated central pattern (n = 1), and spinal cord involvement (PRES-SCI: n = 1) were also encountered. Brainstem involvement (n = 4) showed a characteristic "V-sign" of anterior medullary hyperintensity. Patchy restricted diffusion (46.6%), punctate hemorrhages (37.7%), and leptomeningeal contrast enhancement (36%) were not uncommon. Arterial spin labeling sequence (available in 24 patients) showed increased cerebral blood flow in the involved areas in 79.2% of patients. Univariate analysis showed a significant association of the presence of hemorrhage (P = 0.003), involvement of brainstem (P = 0.007), deep white matter (P = 0.008), and thalamus (P = 0.026) with poor clinical outcome. Multivariate regression analysis found that hemorrhage on MRI (P = 0.011, odds ratio 8) was an independent factor associated with poor clinical outcome. The conventionally described atypical features in PRES are common in children and therefore may no longer be considered exceptions. Raised perfusion on arterial spin labeling sequence was seen in the majority of cases. Hemorrhage on MRI was an independent predictor of poor clinical outcome in pediatric PRES.

Assessing Cerebral Microvascular Volumetric Pulsatility with High-Resolution 4D CBV MRI at 7T.

Arterial pulsation is crucial for promoting fluid circulation and for influencing neuronal activity. Previous studies assessed the pulsatility index based on blood flow velocity pulsatility in relatively large cerebral arteries of human. Here, we introduce a novel method to quantify the volumetric pulsatility of cerebral microvasculature across cortical layers and in white matter (WM), using high-resolution 4D vascular space occupancy (VASO) MRI with simultaneous recording of pulse signals at 7T. Microvascular volumetric pulsatility index (mvPI) and cerebral blood volume (CBV) changes across cardiac cycles are assessed through retrospective sorting of VASO signals into cardiac phases and estimating mean CBV in resting state (CBV0) by arterial spin labeling (ASL) MRI at 7T. Using data from 11 young (28.4±5.8 years) and 7 older (61.3±6.2 years) healthy participants, we investigated the aging effect on mvPI and compared microvascular pulsatility with large arterial pulsatility assessed by 4D-flow MRI. We observed the highest mvPI in the cerebrospinal fluid (CSF) on the cortical surface (0.19±0.06), which decreased towards the cortical layers as well as in larger arteries. In the deep WM, a significantly increased mvPI (p = 0.029) was observed in the older participants compared to younger ones. Additionally, mvPI in deep WM is significantly associated with the velocity pulsatility index (vePI) of large arteries (r = 0.5997, p = 0.0181). We further performed test-retest scans, non-parametric reliability test and simulations to demonstrate the reproducibility and accuracy of our method. To the best of our knowledge, our method offers the first in vivo measurement of microvascular volumetric pulsatility in human brain which has implications for cerebral microvascular health and its relationship research with glymphatic system, aging and neurodegenerative diseases.

Perfusion-weighted MRI patterns in neuropsychiatric systemic lupus erythematosus: a systematic review and meta-analysis.

Neuropsychiatric Systemic Lupus Erythematosus (NPSLE) is a complex manifestation of Systemic Lupus Erythematosus (SLE) characterized by a wide range of neurological and psychiatric symptoms. This study aims to elucidate the patterns of Perfusion-Weighted MRI (PWI) in NPSLE patients compared to SLE patients without neuropsychiatric manifestations (non-NPSLE) and healthy controls (HCs). A systematic search was conducted in PubMed/Medline, Embase, Web of Science, and Scopus for studies utilizing PWI in NPSLE patients published through April 14, 2024. Cerebral blood flow (CBF) data from NPSLE, non-NPSLE patients, and HCs were extracted for meta-analysis, using standardized mean difference (SMD) as an estimate measure. For studies lacking sufficient data for inclusion, CBF, cerebral blood volume (CBV), and mean transit time (MTT) were reviewed qualitatively. Our review included eight observational studies employing PWI techniques, including dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL). The meta-analysis of NPSLE compared to non-NPSLE incorporated four studies, encompassing 104 NPSLE patients and 90 non-NPSLE patients. The results revealed an SMD of -1.42 (95% CI: -2.85-0.00, I2: 94%) for CBF in NPSLE compared to non-NPSLE. PWI reveals informative patterns of cerebral perfusion, showing a significant reduction in mean CBF in NPSLE patients compared to non-NPSLE patients. Our qualitative synthesis highlights these changes, particularly in the frontal and temporal lobes. However, the existing data exhibits considerable heterogeneity and limitations.

Disturbed Dynamic Brain Activity and Neurovascular Coupling in End-Stage Renal Disease Assessed With MRI.

Pathophysiological mechanisms underlying cognitive impairment in end-stage renal disease (ESRD) remain unclear, with limited studies on the temporal variability of neural activity and its coupling with regional perfusion. To assess neural activity and neurovascular coupling (NVC) in ESRD patients, evaluate the classification performance of these abnormalities, and explore their relationships with cognitive function. Prospective. Exactly 33 ESRD patients and 35 age, sex, and education matched healthy controls (HCs). The 3.0T/3D pseudo-continuous arterial spin labeling, resting-state functional MRI, and 3D-T1 weighted structural imaging. Dynamic (dfALFF) and static (sfALFF) fractional amplitude of low-frequency fluctuations and cerebral blood flow (CBF) were assessed. CBF-fALFF correlation coefficients and CBF/fALFF ratio were determined for ESRD patients and HCs. Their ability to distinguish ESRD patients from HCs was evaluated, alongside assessment of cerebral small vessel disease (CSVD) MRI features. All participants underwent blood biochemical and neuropsychological tests to evaluate cognitive decline. Chi-squared test, two-sample t-test, Mann-Whitney U tests, covariance analysis, partial correlation analysis, family-wise error, false discovery rate, Bonferroni correction, area under the receiver operating characteristic curve (AUC) and multivariate pattern analysis. P < 0.05 denoted statistical significance. ESRD patients exhibited higher dfALFF in triangular part of left inferior frontal gyrus (IFGtriang) and left middle temporal gyrus, lower CBF/dfALFF ratio in multiple brain regions, and decreased CBF/sfALFF ratio in bilateral superior temporal gyrus (STG). Compared with CBF/sfALFF ratio, dfALFF, and sfALFF, CBF/dfALFF ratio (AUC = 0.916) achieved the most powerful classification performance in distinguishing ESRD patients from HCs. In ESRD patients, decreased CBF/fALFF ratio correlated with more severe renal impairment, increased CSVD burden, and cognitive decline (0.4 < |r| < 0.6). ESRD patients exhibited abnormal dynamic brain activity and impaired NVC, with dynamic features demonstrating superior discriminative capacity and CBF/dfALFF ratio showing powerful classification performance. 1 TECHNICAL EFFICACY: Stage 1.

Quantitative mapping of renal oxygen consumption using pseudo-continuous arterial spin labeling and quantitative susceptibility mapping in humans.

To propose a new method for quantitatively mapping the renal metabolic rate of oxygen (RMRO2) and to evaluate the proposed method using a caffeine challenge. Pseudo-continuous arterial spin labeling (pCASL) and QSM sequences were used to obtain MR images in the kidney. Six healthy volunteers were scanned on caffeine and control days. The pCASL and QSM images were registered using DICOM information and rigid translation. The Fick principle was applied to estimate RMRO2. The results on caffeine and control days were compared to evaluate the capability of the proposed method to estimate renal oxygen consumption. A paired t-test was used to assess the statistical significance. Estimated renal blood flow (RBF), QSM, and RMRO2 maps were consistent with those reported in the literature. RMRO2 values were higher than the cerebral metabolic rate of oxygen (CMRO2) and were significantly reduced on the caffeine days compared to the control days, consistent with findings from non-MRI literature. The feasibility of measuring renal oxygen consumption using pCASL and QSM images was demonstrated. To the best of our knowledge, this work provides quantitative maps of renal oxygen consumption in humans for the first time. The results were consistent with the literature, including the statistically significant reduction in renal oxygen consumption with caffeine challenge. These findings suggest the potential utility of our technique in measuring renal oxygen consumption noninvasively, especially for patients with complications associated with contrast agents.

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.

Is initial unilateral revascularization acceptable in pediatric patients with bilateral moyamoya disease with mild contralateral hemodynamic disturbance?

Although asymmetrical vascular involvement between hemispheres is common in pediatric patients with bilateral moyamoya disease, whether hemispheres with mild vascular changes and hemodynamic impairment require immediate surgical revascularization or whether they can be observed until disease progression remains unclear. The authors evaluated the long-term outcomes of their strategy to initially perform unilateral surgery and withhold surgery to the contralateral hemispheres with mild vascular changes and hemodynamic impairment. The authors retrospectively evaluated Japanese pediatric patients (onset age ≤ 15 years) diagnosed with bilateral sporadic moyamoya disease who underwent unilateral revascularization. The authors investigated whether the patient underwent additional collateral surgery and the incidence of ischemic events during follow-up. They also compared visual assessments of arterial spin labeling (ASL) images obtained before initial surgery, before additional contralateral surgery, and at last follow-up. Overall, 30/47 patients (63.8%) experienced progression of hemodynamic impairment in the contralateral hemisphere and underwent additional surgery. The age at initial surgery of the patients who needed additional contralateral surgery was significantly younger than that of the patients who did not require contralateral surgery (mean [SD] 7.0 [3.0] years vs 9.8 [2.6] years, p = 0.002). One patient (age 4 years) developed ischemic stroke before admission for preoperative evaluation 2 months after novel symptom onset, and another patient (age 6 years) experienced ischemic stroke in the contralateral hemisphere while discontinuing antiplatelet agents before surgery; both patients fully recovered from the neurological deficits. In contralateral hemispheres that required additional surgery, the ASL visual assessment scores significantly decreased before the additional contralateral surgery compared to those obtained before the initial surgery (p = 0.008). In pediatric patients with bilateral moyamoya disease, withholding surgery for hemispheres with mild vascular changes and hemodynamic impairment is generally safe. Younger patients were more likely to experience contralateral progression and require additional surgery, so close follow-up is needed. ASL imaging is useful for detecting and following the progression of hemodynamic impairment in conservatively treated hemispheres.