Regional and depth-dependence of cortical blood-flow assessed with high-resolution Arterial Spin Labeling (ASL).
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ABSTRACT:
SUBMITTER: Taso M
PROVIDER: S-EPMC8327107 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:We have examined sensitivity and specificity of pseudocontinuous arterial spin labeling (PCASL) to detect global and regional changes in cerebral blood flow (CBF) in response to two different psychoactive drugs. We tested alcohol and morphine in a placebo-controlled, double-blind randomized study in 12 healthy young men. Drugs were administered intravenously. Validated pharmacokinetic protocols achieved minimal intersubject and intrasubject variance in plasma drug concentration. Permutation-based statistical testing of a mixed effect repeated measures model revealed a widespread increase in absolute CBF because of both morphine and alcohol. Conjunction analysis revealed overlapping effects of morphine and alcohol on absolute CBF in the left anterior cingulate, right hippocampus, right insula, and left primary sensorimotor areas. Effects of morphine and alcohol on relative CBF (obtained from z-normalization of absolute CBF maps) were significantly different in the left putamen, left frontoparietal network, cerebellum, and the brainstem. Corroborating previous PET results, our findings suggest that PCASL is a promising tool for central nervous system drug research.
| S-EPMC3099639 | biostudies-literature
Project description:ObjectiveTo investigate the relationship between cerebral blood flow and dementia in older stroke survivors and subjects with Alzheimer disease (AD).MethodsThis cohort study used arterial spin labeling MRI at 3 T to examine cerebral blood flow (CBF). We scanned 39 patients 6 years after stroke. They were older than 75 years at the time of stroke and free of dementia 3 months poststroke, with 8 subsequently developing dementia. We also scanned 17 subjects with AD and 29 healthy control subjects. We determined the perfusion in regions of interest (ROIs). Hippocampal volume was also measured using a previously validated automated procedure.ResultsThe gray matter/white matter CBF ratio was reduced globally in the poststroke dementia (PSD) group (1.55 SD = 0.12) relative to control subjects (1.78 SD = 0.18; p = 0.03). The CBF ratio in a parietal ROI was reduced in the AD (1.34 SD = 0.31; p = 0.003), PSD (1.32 SD = 0.22; p = 0.041), and poststroke no-dementia (PSND) (1.44 SD = 0.34; p = 0.014) groups relative to that of control subjects (1.70 SD = 0.32). In subjects without stroke, the best predictor of dementia was hippocampus volume, whereas in the stroke group, it was the global CBF gray matter/white matter ratio. Hippocampus volume was not significantly different between the AD and PSD groups, and both had reduced hippocampi relative to those of control subjects and the PSND group.ConclusionsWe found evidence for both vascular and AD pathology in PSD, suggesting that both the direct impact of the stroke and subsequent development of AD-type changes play a role in the etiology of PSD.
| S-EPMC3087466 | biostudies-literature
Project description:BACKGROUND:With the disappointing outcomes of clinical trials on patients with Alzheimer's disease or mild cognitive impairment (MCI), there is increasing attention to understanding cognitive decline in normal elderly individuals, with the goal of identifying subjects who are most susceptible to imminent cognitive impairment. PURPOSE/HYPOTHESIS:To evaluate the potential of cerebral blood flow (CBF) as a biomarker by investigating the relationship between CBF at baseline and cognition at follow-up. STUDY TYPE:Prospective longitudinal study with a 4-year time interval. POPULATION:309 healthy subjects aged 20-89 years old. FIELD STRENGTH/SEQUENCE:3T pseudo-continuous-arterial-spin-labeling MRI. ASSESSMENT:CBF at baseline and cognitive assessment at both baseline and follow-up. STATISTICAL TESTS:Linear regression analyses with age, systolic blood pressure, physical activity, and baseline cognition as covariates. RESULTS:Linear regression analyses revealed that whole-brain CBF at baseline was predictive of general fluid cognition at follow-up. This effect was observed in the older group (age ?54 years, ??=?0.221, P?=?0.004), but not in younger or entire sample (??=?0.018, P?=?0.867 and ??=?0.089, P?=?0.098, respectively). Among major brain lobes, frontal CBF had the highest sensitivity in predicting future cognition, with a significant effect observed for fluid cognition (??=?0.244 P?=?0.001), episodic memory (??=?0.294, P?=?0.001), and reasoning (??=?0.186, P?=?0.027). These associations remained significant after accounting for baseline cognition. Voxelwise analysis revealed that medial frontal cortex and anterior cingulate cortex, part of the default mode network (DMN), are among the most important regions in predicting fluid cognition. DATA CONCLUSION:In a healthy aging cohort, CBF can predict general cognitive ability as well as specific domains of cognitive function. LEVEL OF EVIDENCE:1 Technical Efficacy: Stage 3 J. MAGN. RESON. IMAGING 2018;48:449-458.
| S-EPMC6028323 | biostudies-literature
Project description:The arterial spin labeling (ASL) method provides images in which, ideally, the signal intensity of each image voxel is proportional to the local perfusion. For studies of pulmonary perfusion, the relative dispersion (RD, standard deviation/mean) of the ASL signal across a lung section is used as a reliable measure of flow heterogeneity. However, the RD of the ASL signals within the lung may systematically differ from the true RD of perfusion because the ASL image also includes signals from larger vessels, which can reflect the blood volume rather than blood flow if the vessels are filled with tagged blood during the imaging time. Theoretical studies suggest that the pulmonary vasculature exhibits a lognormal distribution for blood flow and thus an appropriate measure of heterogeneity is the geometric standard deviation (GSD). To test whether the ASL signal exhibits a lognormal distribution for pulmonary blood flow, determine whether larger vessels play an important role in the distribution, and extract physiologically relevant measures of heterogeneity from the ASL signal, we quantified the ASL signal before and after an intervention (head-down tilt) in six subjects. The distribution of ASL signal was better characterized by a lognormal distribution than a normal distribution, reducing the mean squared error by 72% (p < 0.005). Head-down tilt significantly reduced the lognormal scale parameter (p = 0.01) but not the shape parameter or GSD. The RD increased post-tilt and remained significantly elevated (by 17%, p < 0.05). Test case results and mathematical simulations suggest that RD is more sensitive than the GSD to ASL signal from tagged blood in larger vessels, a probable explanation of the change in RD without a statistically significant change in GSD. This suggests that the GSD is a useful measure of pulmonary blood flow heterogeneity with the advantage of being less affected by the ASL signal from tagged blood in larger vessels.
| S-EPMC2836845 | biostudies-other
Project description:Maintaining attention and performance over time is an essential part of many activities, and effortful cognitive control is required to avoid vigilance decrements and interference from distraction. Regions at or near right middle frontal gyrus (Brodmann's area (BA) 9), as well as in other prefrontal and parietal areas, are often activated in studies of sustained attention (e.g., Cabeza and Nyberg, 2000; Kim et al., 2006; Lim et al., 2010). This activation has often been interpreted as representing the engagement of cognitive control processes. However, such studies are typically implemented at one level of task difficulty, without an experimental manipulation of control demands. The present study used the distractor condition sustained attention task (dSAT), which has been used extensively in animals to determine the role of neuromodulator systems in attentional performance, to test the hypotheses that BA 9 is sensitive to changes in the demand for cognitive control and that this sensitivity reflects an increased engagement of attentional effort. Continuous arterial spin labeling (ASL) was used to measure neural activity in sixteen healthy, young adults performing a sustained attention task under standard conditions and under a distraction condition that provided an experimental manipulation of demands on cognitive control. The distractor impaired behavioral performance and increased activation in right middle frontal gyrus. Larger increases in right middle frontal gyrus activity were associated with greater behavioral vulnerability to the distractor. These findings indicate that while right middle frontal gyrus regions are sensitive to demands for attentional effort and control, they may not be sufficient to maintain performance under challenge. In addition, they demonstrate the sensitivity of ASL methods to variations in task demands, and suggest that the dSAT may be a useful tool for translational cross-species and clinical research.
| S-EPMC2997179 | biostudies-literature
Project description:To determine how different methods of normalizing for global cerebral blood flow (gCBF) affect image quality and sensitivity to cortical activation, pulsed arterial spin labeling (pASL) scans obtained during a visual task were normalized by either additive or multiplicative normalization of modal gCBF. Normalization by either method increased the statistical significance of cortical activation by a visual stimulus. However, image quality was superior with additive normalization, whether judged by intensity histograms or by reduced variability within gray and white matter.
| S-EPMC4369335 | biostudies-literature
Project description:Perfusion-weighted imaging is used to select patients with acute ischemic stroke for intervention, but knowledge of cerebral perfusion can also inform the understanding of ischemic injury. Arterial spin labeling allows repeated measurement of absolute cerebral blood flow (CBF) without the need for exogenous contrast. The aim of this study was to explore the relationship between dynamic CBF and tissue outcome in the month after stroke onset.Patients with nonlacunar ischemic stroke underwent ?5 repeated magnetic resonance imaging scans at presentation, 2 hours, 1 day, 1 week, and 1 month. Imaging included vessel-encoded pseudocontinuous arterial spin labeling using multiple postlabeling delays to quantify CBF in gray matter regions of interest. Receiver-operator characteristic curves were used to predict tissue outcome using CBF. Repeatability was assessed in 6 healthy volunteers and compared with contralateral regions of patients. Diffusion-weighted and T2-weighted fluid attenuated inversion recovery imaging were used to define tissue outcome.Forty patients were included. In contralateral regions of patients, there was significant variation of CBF between individuals, but not between scan times (mean±SD: 53±42 mL/100 g/min). Within ischemic regions, mean CBF was lowest in ischemic core (17±23 mL/100 g/min), followed by regions of early (21±26 mL/100 g/min) and late infarct growth (25±35 mL/100 g/min; ANOVA P<0.0001). Between patients, there was marked overlap in presenting and serial CBF values.Knowledge of perfusion dynamics partially explained tissue fate. Factors such as metabolism and tissue susceptibility are also likely to influence tissue outcome.
| S-EPMC5175999 | biostudies-literature
Project description:BackgroundThe choroid plexus is a major contributor to the generation of cerebrospinal fluid (CSF) and the maintenance of its electrolyte and metabolite balance. Here, we sought to characterize the blood flow dynamics of the choroid plexus using arterial spin labeling (ASL) MRI to establish ASL as a non-invasive tool for choroid plexus function and disease studies.MethodsSeven healthy volunteers were imaged on a 3T MR scanner. ASL images were acquired with 12 labeling durations and post labeling delays. Regions of the choroid plexus were manually segmented on high-resolution T1 weighted images. Choroid plexus perfusion was characterized with a dynamic ASL perfusion model. Cerebral gray matter perfusion was also quantified for comparison.ResultsKinetics of the ASL signal were clearly different in the choroid plexus than in gray matter. The choroid plexus has a significantly longer T1 than the gray matter (2.33?±?0.30 s vs. 1.85?±?0.10 s, p?<?0.02). The arterial transit time was 1.24?±?0.20 s at the choroid plexus. The apparent blood flow to the choroid plexus was measured to be 39.5?±?10.1 ml/100 g/min and 0.80?±?0.31 ml/min integrated over the posterior lateral ventricles in both hemispheres. Correction with the choroid plexus weight yielded a blood flow of 80 ml/100 g/min.ConclusionsOur findings suggest that ASL can provide a clinically feasible option to quantify the dynamic characteristics of choroid plexus blood flow. It also provides useful reference values of the choroid plexus perfusion. The long T1 of the choroid plexus may suggest the transport of water from arterial blood to the CSF, potentially providing a method to quantify CSF generation.
| S-EPMC7510126 | biostudies-literature
Project description:BackgroundNoninvasive measurement of placental blood flow is the major technical challenge for predicting ischemic placenta (IPD). Pseudocontinuous arterial spin labeling (pCASL) MRI was recently shown to be promising, but the potential value in predicting the subsequence development of IPD is not known.PurposeTo derive global and regional placental blood flow parameters from longitudinal measurements of pCASL MRI and to assess the associations between perfusion-related parameters and IPD.Study typeProspective.PopulationEighty-four women completed two pCASL MRI scans (first; 14-18 weeks and second; 19-24 weeks) from prospectively recruited 118 subjects. A total of 69 subjects were included for the analysis, of which 15 subjects developed IPD.Field strength/sequence3T/T2 -weighted half-Fourier single-shot turbo spin-echo (HASTE) and pCASL.AssessmentFour perfusion-related parameters in the placenta were derived: placenta volume, placental blood flow (PBF), high PBF (hPBF), and relative hPBF. The longitudinal changes of the parameters and their association with IPD were tested after being normalizing to the 16th and 20th weeks of gestation.Statistical testsComparisons between two gestational ages within subjects were performed using the paired Wilcoxon tests, and comparisons between normal and IPD groups were performed using the unpaired Wilcoxon tests.ResultsThe difference between the first and second MRI scans was statistically significant for volume (156.6 cm3 vs. 269.7 cm3 , P < 0.001) and PBF (104.9 ml/100g/min vs. 111.3 ml/100g/min, P = 0.02) for normal subjects, indicating an increase in pregnancy with advancing gestation. Of the parameters tested, the difference between the normal and IPD subjects was most pronounced in hPBF (278.1 ml/100g/min vs. 180.7 ml/100g/min, P < 0.001) and relative hPBF (259.1% vs. 183.2%, P < 0.001) at 16 weeks.Data conclusionThe high perfusion-related image parameters for IPD were significantly decreased from normal pregnancy at 14-18 weeks of gestation.Level of evidence2 TECHNICAL EFFICACY STAGE: 1 J. Magn. Reson. Imaging 2020;51:1247-1257.
| S-EPMC7654100 | biostudies-literature
Project description:Although arterial spin labeling (ASL) is appealing for mapping long-term changes in functional activity, inter-sessional variations in basal blood flow, arterial transit times (ATTs), and alignment errors, can result in significant false activation when comparing images from separate sessions. By taking steps to reduce these sources of noise, this study assessed the ability of ASL to detect functional CBF changes between sessions. ASL data were collected in three sessions to image ATT, resting CBF and CBF changes associated with motor activation (7 participants). Activation maps were generated using rest and task images acquired in the same session and from sessions separated by up to a month. Good agreement was found when comparing between-session activation maps to within-session activation maps with only a 16% decrease in precision (within-session: 90 ± 7%) and a 13% decrease in the Dice similarity (within-session: 0.75 ± 0.07) coefficient after a month. In addition, voxel-wise reproducibility (within-session: 4.7 ± 4.5%) and reliability (within-session: 0.89 ± 0.20) of resting grey-matter CBF decreased by less than 18% for the between-session analysis relative to within-session values. ATT variability between sessions (5.0 ± 2.7%) was roughly half the between-subject variability, indicating that its effects on longitudinal CBF were minimal. These results demonstrate that conducting voxel-wise analysis on CBF images acquired on different days is feasible with only modest loss in precision, highlighting the potential of ASL for longitudinal studies.
| S-EPMC5051683 | biostudies-literature