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Sleight E, Stringer MS, Mitchell I, Murphy M, Marshall I, Wardlaw JM, Thrippleton MJ. Cerebrovascular reactivity measurements using 3T BOLD MRI and a fixed inhaled CO 2 gas challenge: Repeatability and impact of processing strategy. Front Physiol 2023; 14:1070233. [PMID: 36814481 PMCID: PMC9939770 DOI: 10.3389/fphys.2023.1070233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 01/19/2023] [Indexed: 02/09/2023] Open
Abstract
Introduction: Cerebrovascular reactivity (CVR) measurements using blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) are commonly used to assess the health of cerebral blood vessels, including in patients with cerebrovascular diseases; however, evidence and consensus regarding reliability and optimal processing are lacking. We aimed to assess the repeatability, accuracy and precision of voxel- and region-based CVR measurements at 3 T using a fixed inhaled (FI) CO2 stimulus in a healthy cohort. Methods: We simulated the effect of noise, delay constraints and voxel- versus region-based analysis on CVR parameters. Results were verified in 15 healthy volunteers (28.1±5.5 years, female: 53%) with a test-retest MRI experiment consisting of two CVR scans. CVR magnitude and delay in grey matter (GM) and white matter were computed for both analyses assuming a linear relationship between the BOLD signal and time-shifted end-tidal CO2 (EtCO2) profile. Results: Test-retest repeatability was high [mean (95% CI) inter-scan difference: -0.01 (-0.03, -0.00) %/mmHg for GM CVR magnitude; -0.3 (-1.2,0.6) s for GM CVR delay], but we detected a small systematic reduction in CVR magnitude at scan 2 versus scan 1, accompanied by a greater EtCO2 change [±1.0 (0.4,1.5) mmHg] and lower heart rate [-5.5 (-8.6,-2.4] bpm]. CVR magnitude estimates were higher for voxel- versus region-based analysis [difference in GM: ±0.02 (0.01,0.03) %/mmHg]. Findings were supported by simulation results, predicting a positive bias for voxel-based CVR estimates dependent on temporal contrast-to-noise ratio and delay fitting constraints and an underestimation for region-based CVR estimates. Discussion: BOLD CVR measurements using FI stimulus have good within-day repeatability in healthy volunteers. However, measurements may be influenced by physiological effects and the analysis protocol. Voxel-based analyses should be undertaken with care due to potential for systematic bias; region-based analyses are more reliable in such cases.
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Affiliation(s)
- Emilie Sleight
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom,UK Dementia Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Michael S. Stringer
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom,UK Dementia Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Isla Mitchell
- Edinburgh Imaging Facility, Royal Infirmary of Edinburgh, University of Edinburgh, Edinburgh, United Kingdom
| | - Madeleine Murphy
- Edinburgh Imaging Facility, Royal Infirmary of Edinburgh, University of Edinburgh, Edinburgh, United Kingdom
| | - Ian Marshall
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom,UK Dementia Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Joanna M. Wardlaw
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom,UK Dementia Research Institute, University of Edinburgh, Edinburgh, United Kingdom,Edinburgh Imaging Facility, Royal Infirmary of Edinburgh, University of Edinburgh, Edinburgh, United Kingdom
| | - Michael J. Thrippleton
- Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom,UK Dementia Research Institute, University of Edinburgh, Edinburgh, United Kingdom,Edinburgh Imaging Facility, Royal Infirmary of Edinburgh, University of Edinburgh, Edinburgh, United Kingdom,*Correspondence: Michael J. Thrippleton,
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Reeder EL, O'Connell CJ, Collins SM, Traubert OD, Norman SV, Cáceres RA, Sah R, Smith DW, Robson MJ. Increased Carbon Dioxide Respiration Prevents the Effects of Acceleration/Deceleration Elicited Mild Traumatic Brain Injury. Neuroscience 2023; 509:20-35. [PMID: 36332692 DOI: 10.1016/j.neuroscience.2022.10.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/30/2022] [Accepted: 10/17/2022] [Indexed: 11/07/2022]
Abstract
Acceleration/deceleration forces are a common component of various causes of mild traumatic brain injury (mTBI) and result in strain and shear forces on brain tissue. A small quantifiable volume dubbed the compensatory reserve volume (CRV) permits energy transmission to brain tissue during acceleration/deceleration events. The CRV is principally regulated by cerebral blood flow (CBF) and CBF is primarily determined by the concentration of inspired carbon dioxide (CO2). We hypothesized that experimental hypercapnia (i.e. increased inspired concentration of CO2) may act to prevent and mitigate the actions of acceleration/deceleration-induced TBI. To determine these effects C57Bl/6 mice underwent experimental hypercapnia whereby they were exposed to medical-grade atmospheric air or 5% CO2 immediately prior to an acceleration/deceleration-induced mTBI paradigm. mTBI results in significant increases in righting reflex time (RRT), reductions in core body temperature, and reductions in general locomotor activity-three hours post injury (hpi). Experimental hypercapnia immediately preceding mTBI was found to prevent mTBI-induced increases in RRT and reductions in core body temperature and general locomotor activity. Ribonucleic acid (RNA) sequencing conducted four hpi revealed that CO2 exposure prevented mTBI-induced transcriptional alterations of several targets related to oxidative stress, immune, and inflammatory signaling. Quantitative real-time PCR analysis confirmed the prevention of mTBI-induced increases in mitogen-activated protein kinase kinase kinase 6 and metallothionein-2. These initial proof of concept studies reveal that increases in inspired CO2 mitigate the detrimental contributions of acceleration/deceleration events in mTBI and may feasibly be translated in the future to humans using a medical device seeking to prevent mTBI among high-risk groups.
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Affiliation(s)
- Evan L Reeder
- University of Cincinnati James L. Winkle College of Pharmacy, Division of Pharmaceutical Sciences, Cincinnati, OH 45267, USA
| | - Christopher J O'Connell
- University of Cincinnati James L. Winkle College of Pharmacy, Division of Pharmaceutical Sciences, Cincinnati, OH 45267, USA
| | - Sean M Collins
- University of Cincinnati James L. Winkle College of Pharmacy, Division of Pharmaceutical Sciences, Cincinnati, OH 45267, USA
| | - Owen D Traubert
- University of Cincinnati College of Arts and Sciences, Department of Biological Sciences, Cincinnati, OH 45221, USA
| | - Sophia V Norman
- University of Cincinnati College of Arts and Sciences, Department of Biological Sciences, Cincinnati, OH 45221, USA
| | - Román A Cáceres
- University of Cincinnati College of Medicine, Department of Cancer and Cell Biology Cincinnati, OH 45267, USA
| | - Renu Sah
- University of Cincinnati College of Medicine, Department of Pharmacology and Systems Physiology, Cincinnati, OH 45267, USA
| | | | - Matthew J Robson
- University of Cincinnati James L. Winkle College of Pharmacy, Division of Pharmaceutical Sciences, Cincinnati, OH 45267, USA.
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Tsvetanov KA, Spindler LRB, Stamatakis EA, Newcombe VFJ, Lupson VC, Chatfield DA, Manktelow AE, Outtrim JG, Elmer A, Kingston N, Bradley JR, Bullmore ET, Rowe JB, Menon DK. Hospitalisation for COVID-19 predicts long lasting cerebrovascular impairment: A prospective observational cohort study. Neuroimage Clin 2022; 36:103253. [PMID: 36451358 PMCID: PMC9639388 DOI: 10.1016/j.nicl.2022.103253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 10/06/2022] [Accepted: 10/31/2022] [Indexed: 11/09/2022]
Abstract
Human coronavirus disease 2019 (COVID-19) due to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has multiple neurological consequences, but its long-term effect on brain health is still uncertain. The cerebrovascular consequences of COVID-19 may also affect brain health. We studied the chronic effect of COVID-19 on cerebrovascular health, in relation to acute severity, adverse clinical outcomes and in contrast to control group data. Here we assess cerebrovascular health in 45 patients six months after hospitalisation for acute COVID-19 using the resting state fluctuation amplitudes (RSFA) from functional magnetic resonance imaging, in relation to disease severity and in contrast with 42 controls. Acute COVID-19 severity was indexed by COVID-19 WHO Progression Scale, inflammatory and coagulatory biomarkers. Chronic widespread changes in frontoparietal RSFA were related to the severity of the acute COVID-19 episode. This relationship was not explained by chronic cardiorespiratory dysfunction, age, or sex. The level of cerebrovascular dysfunction was associated with cognitive, mental, and physical health at follow-up. The principal findings were consistent across univariate and multivariate approaches. The results indicate chronic cerebrovascular impairment following severe acute COVID-19, with the potential for long-term consequences on cognitive function and mental wellbeing.
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Affiliation(s)
- Kamen A Tsvetanov
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom; Department of Psychology, University of Cambridge, Cambridge, United Kingdom.
| | - Lennart R B Spindler
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom; Division of Anaesthesia, Department of Medicine, University Cambridge, Cambridge, United Kingdom
| | - Emmanuel A Stamatakis
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom; Division of Anaesthesia, Department of Medicine, University Cambridge, Cambridge, United Kingdom
| | - Virginia F J Newcombe
- Division of Anaesthesia, Department of Medicine, University Cambridge, Cambridge, United Kingdom; Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom
| | - Victoria C Lupson
- Division of Anaesthesia, Department of Medicine, University Cambridge, Cambridge, United Kingdom; Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom
| | - Doris A Chatfield
- Division of Anaesthesia, Department of Medicine, University Cambridge, Cambridge, United Kingdom
| | - Anne E Manktelow
- Division of Anaesthesia, Department of Medicine, University Cambridge, Cambridge, United Kingdom
| | - Joanne G Outtrim
- Division of Anaesthesia, Department of Medicine, University Cambridge, Cambridge, United Kingdom
| | - Anne Elmer
- Cambridge Clinical Research Centre, NIHR Clinical Research Facility, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Nathalie Kingston
- NIHR BioResource, Cambridge University Hospitals NHS Foundation, Cambridge Biomedical Campus, Cambridge, United Kingdom; Department of Haematology, School of Clinical Medicine, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - John R Bradley
- NIHR BioResource, Cambridge University Hospitals NHS Foundation, Cambridge Biomedical Campus, Cambridge, United Kingdom; Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
| | - Edward T Bullmore
- Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom; Department of Psychiatry, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - James B Rowe
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom; Medical Research Council Cognition and Brain Sciences Unit, Department of Psychiatry, Cambridge, United Kingdom
| | - David K Menon
- Division of Anaesthesia, Department of Medicine, University Cambridge, Cambridge, United Kingdom; Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, United Kingdom; Cambridge Clinical Research Centre, NIHR Clinical Research Facility, Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, United Kingdom; Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Cambridge, United Kingdom
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Early fMRI responses to somatosensory and optogenetic stimulation reflect neural information flow. Proc Natl Acad Sci U S A 2021; 118:2023265118. [PMID: 33836602 PMCID: PMC7980397 DOI: 10.1073/pnas.2023265118] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
fMRI has revolutionized how neuroscientists investigate human brain functions and networks. To further advance understanding of brain functions, identifying the direction of information flow, such as thalamocortical versus corticothalamic projections, is critical. Because the early hemodynamic response at microvessels near active neurons can be detected by ultrahigh field fMRI, we propose using the onset times of fMRI responses to discern the information flow. This approach was confirmed by observing the ultrahigh spatiotemporal resolution BOLD fMRI responses to bottom-up somatosensory stimulation and top-down optogenetic stimulation of the primary motor cortex in anesthetized mice. Because ultrahigh field MRI is increasingly available, ultrahigh spatiotemporal fMRI will significantly facilitate the investigation of functional circuits in humans. Blood oxygenation level–dependent (BOLD) functional magnetic resonance imaging (fMRI) has been widely used to localize brain functions. To further advance understanding of brain functions, it is critical to understand the direction of information flow, such as thalamocortical versus corticothalamic projections. For this work, we performed ultrahigh spatiotemporal resolution fMRI at 15.2 T of the mouse somatosensory network during forepaw somatosensory stimulation and optogenetic stimulation of the primary motor cortex (M1). Somatosensory stimulation induced the earliest BOLD response in the ventral posterolateral nucleus (VPL), followed by the primary somatosensory cortex (S1) and then M1 and posterior thalamic nucleus. Optogenetic stimulation of excitatory neurons in M1 induced the earliest BOLD response in M1, followed by S1 and then VPL. Within S1, the middle cortical layers responded to somatosensory stimulation earlier than the upper or lower layers, whereas the upper cortical layers responded earlier than the other two layers to optogenetic stimulation in M1. The order of early BOLD responses was consistent with the canonical understanding of somatosensory network connections and cannot be explained by regional variabilities in the hemodynamic response functions measured using hypercapnic stimulation. Our data demonstrate that early BOLD responses reflect the information flow in the mouse somatosensory network, suggesting that high-field fMRI can be used for systems-level network analyses.
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Tsvetanov KA, Henson RNA, Rowe JB. Separating vascular and neuronal effects of age on fMRI BOLD signals. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190631. [PMID: 33190597 PMCID: PMC7741031 DOI: 10.1098/rstb.2019.0631] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/19/2020] [Indexed: 12/14/2022] Open
Abstract
Accurate identification of brain function is necessary to understand the neurobiology of cognitive ageing, and thereby promote well-being across the lifespan. A common tool used to investigate neurocognitive ageing is functional magnetic resonance imaging (fMRI). However, although fMRI data are often interpreted in terms of neuronal activity, the blood oxygenation level-dependent (BOLD) signal measured by fMRI includes contributions of both vascular and neuronal factors, which change differentially with age. While some studies investigate vascular ageing factors, the results of these studies are not well known within the field of neurocognitive ageing and therefore vascular confounds in neurocognitive fMRI studies are common. Despite over 10 000 BOLD-fMRI papers on ageing, fewer than 20 have applied techniques to correct for vascular effects. However, neurovascular ageing is not only a confound in fMRI, but an important feature in its own right, to be assessed alongside measures of neuronal ageing. We review current approaches to dissociate neuronal and vascular components of BOLD-fMRI of regional activity and functional connectivity. We highlight emerging evidence that vascular mechanisms in the brain do not simply control blood flow to support the metabolic needs of neurons, but form complex neurovascular interactions that influence neuronal function in health and disease. This article is part of the theme issue 'Key relationships between non-invasive functional neuroimaging and the underlying neuronal activity'.
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Affiliation(s)
- Kamen A. Tsvetanov
- Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0SZ, UK
- Department of Psychology, University of Cambridge, Cambridge CB2 3EB, UK
| | - Richard N. A. Henson
- Department of Psychiatry, University of Cambridge, Cambridge CB2 0SP, UK
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, Cambridge CB2 7EF, UK
| | - James B. Rowe
- Department of Clinical Neurosciences, University of Cambridge, Cambridge CB2 0SZ, UK
- Medical Research Council Cognition and Brain Sciences Unit, University of Cambridge, Cambridge CB2 7EF, UK
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Yang HCS, Liang Z, Vike NL, Lee T, Rispoli JV, Nauman EA, Talavage TM, Tong Y. Characterizing near-infrared spectroscopy signal under hypercapnia. JOURNAL OF BIOPHOTONICS 2020; 13:e202000173. [PMID: 32706517 DOI: 10.1002/jbio.202000173] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 07/11/2020] [Accepted: 07/20/2020] [Indexed: 06/11/2023]
Abstract
Vasoactive stress tests (i.e. hypercapnia, elevated partial pressure of arterial CO2 [PaCO2 ]) are commonly used in functional MRI (fMRI), to induce cerebral blood flow changes and expose hidden perfusion deficits in the brain. Compared with fMRI, near-infrared spectroscopy (NIRS) is an alternative low-cost, real-time, and non-invasive tool, which can be applied in out-of-hospital settings. To develop and optimize vasoactive stress tests for NIRS, several hypercapnia-induced tasks were tested using concurrent-NIRS/fMRI on healthy subjects. The results indicated that the cerebral and extracerebral reactivity to elevated PaCO2 depended on the rate of the CO2 increase. A steep increase resulted in different cerebral and extracerebral reactivities, leading to unpredictable NIRS measurements compared with fMRI. However, a ramped increase, induced by ramped-CO2 inhalation or breath-holding tasks, induced synchronized cerebral, and extracerebral reactivities, resulting in consistent NIRS and fMRI measurements. These results demonstrate that only tasks that increase PaCO2 gradually can produce reliable NIRS results.
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Affiliation(s)
- Ho-Ching Shawn Yang
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
| | - Zhenhu Liang
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
- Institute of Electrical Engineering, Yanshan University, Qinhuangdao, China
| | - Nicole L Vike
- Department of Basic Medical Sciences, Purdue University, West Lafayette, Indiana, USA
| | - Taylor Lee
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA
| | - Joseph V Rispoli
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, USA
| | - Eric A Nauman
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
- School of Mechanical Engineering, Purdue University, West Lafayette, Indiana, USA
| | - Thomas M Talavage
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, USA
| | - Yunjie Tong
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA
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Faraci FM, Taugher RJ, Lynch C, Fan R, Gupta S, Wemmie JA. Acid-Sensing Ion Channels: Novel Mediators of Cerebral Vascular Responses. Circ Res 2019; 125:907-920. [PMID: 31451088 PMCID: PMC6813889 DOI: 10.1161/circresaha.119.315024] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
RATIONALE Precise regulation of cerebral blood flow is critical for normal brain function. Insufficient cerebral blood flow contributes to brain dysfunction and neurodegeneration. Carbon dioxide (CO2), via effects on local acidosis, is one of the most potent regulators of cerebral blood flow. Although a role for nitric oxide in intermediate signaling has been implicated, mechanisms that initiate CO2-induced vasodilation remain unclear. OBJECTIVE Acid-sensing ion channel-1A (ASIC1A) is a proton-gated cation channel that is activated by extracellular acidosis. Based on work that implicated ASIC1A in the amygdala and bed nucleus of the stria terminalis in CO2-evoked and acid-evoked behaviors, we hypothesized that ASIC1A might also mediate microvascular responses to CO2. METHODS AND RESULTS To test this hypothesis, we genetically and pharmacologically manipulated ASIC1A and assessed effects on CO2-induced dilation of cerebral arterioles in vivo. Effects of inhalation of 5% or 10% CO2 on arteriolar diameter were greatly attenuated in mice with global deficiency in ASIC1A (Asic1a-/-) or by local treatment with the ASIC inhibitor, psalmotoxin. Vasodilator effects of acetylcholine, which acts via endothelial nitric oxide synthase were unaffected, suggesting a nonvascular source of nitric oxide may be key for CO2 responses. Thus, we tested whether neurons may be the cell type through which ASIC1A influences microvessels. Using mice in which Asic1a was specifically disrupted in neurons, we found effects of CO2 on arteriolar diameter were also attenuated. CONCLUSIONS Together, these data are consistent with a model wherein activation of ASIC1A, particularly in neurons, is critical for CO2-induced nitric oxide production and vasodilation. With these findings, ASIC1A emerges as major regulator of microvascular tone.
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Affiliation(s)
- Frank M. Faraci
- Department of Internal Medicine, Francois M. Abboud Cardiovascular Center, Papajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Department of Veterans Affairs Medical Center, Iowa City, IA 52242
- Department of Pharmacology, Francois M. Abboud Cardiovascular Center, Papajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Department of Veterans Affairs Medical Center, Iowa City, IA 52242
| | - Rebecca J. Taugher
- Department of Psychiatry, Francois M. Abboud Cardiovascular Center, Papajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Department of Veterans Affairs Medical Center, Iowa City, IA 52242
| | - Cynthia Lynch
- Department of Internal Medicine, Francois M. Abboud Cardiovascular Center, Papajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Department of Veterans Affairs Medical Center, Iowa City, IA 52242
| | - Rong Fan
- Department of Psychiatry, Francois M. Abboud Cardiovascular Center, Papajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Department of Veterans Affairs Medical Center, Iowa City, IA 52242
| | - Subhash Gupta
- Department of Psychiatry, Francois M. Abboud Cardiovascular Center, Papajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Department of Veterans Affairs Medical Center, Iowa City, IA 52242
| | - John A. Wemmie
- Department of Psychiatry, Francois M. Abboud Cardiovascular Center, Papajohn Biomedical Institute, Carver College of Medicine, University of Iowa, Department of Veterans Affairs Medical Center, Iowa City, IA 52242
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Rapid cerebrovascular reactivity mapping: Enabling vascular reactivity information to be routinely acquired. Neuroimage 2017; 159:214-223. [PMID: 28756241 DOI: 10.1016/j.neuroimage.2017.07.048] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 07/17/2017] [Accepted: 07/23/2017] [Indexed: 11/22/2022] Open
Abstract
Cerebrovascular reactivity mapping (CVR), using magnetic resonance imaging (MRI) and carbon dioxide as a stimulus, provides useful information on how cerebral blood vessels react under stress. This information has proven to be useful in the study of vascular disorders, dementia and healthy ageing. However, clinical adoption of this form of CVR mapping has been hindered by relatively long scan durations of 7-12 min. By replacing the conventional block presentation of carbon dioxide enriched air with a sinusoidally modulated stimulus, the aim of this study was to investigate whether more clinically acceptable scan durations are possible. Firstly, the conventional block protocol was compared with a sinusoidal protocol of the same duration of 7 min. Estimates of the magnitude of the CVR signal (CVR magnitude) were found to be in good agreement between the stimulus protocols, but estimates of the relative timing of the CVR response (CVR phase) were not. Secondly, data from the sinusoidal protocol was reanalysed using decreasing amounts of data in the range 1-6 min. The CVR magnitude was found to tolerate this reduction in scan duration better than CVR phase. However, these analyses indicate that scan durations in the range of 3-5 min produce robust data.
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Blair GW, Doubal FN, Thrippleton MJ, Marshall I, Wardlaw JM. Magnetic resonance imaging for assessment of cerebrovascular reactivity in cerebral small vessel disease: A systematic review. J Cereb Blood Flow Metab 2016; 36:833-41. [PMID: 26884471 PMCID: PMC4853842 DOI: 10.1177/0271678x16631756] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 01/04/2016] [Indexed: 11/16/2022]
Abstract
Cerebral small vessel disease (SVD) pathophysiology is poorly understood. Cerebrovascular reactivity (CVR) impairment may play a role, but evidence to date is mainly indirect. Magnetic resonance imaging (MRI) allows investigation of CVR directly in the tissues affected by SVD. We systematically reviewed the use of MRI to measure CVR in subjects with SVD. Five studies (total n = 155 SVD subjects, 84 controls) provided relevant data. The studies included different types of patients. Each study used blood oxygen level dependent (BOLD) MRI to assess CVR but a different vasoactive stimulus and method of calculating CVR. CVR decreased with increasing white matter hyperintensities in two studies (n = 17, 11%) and in the presence of microbleeds in another. Three studies (n = 138, 89%) found no association of CVR with white matter hyperintensities. No studies provided tissue-specific CVR values. CVR decreased with age in three studies, and with female gender and increasing diastolic blood pressure in one study. Safety and tolerability data were limited. Larger studies using CVR appear to be feasible and are needed, preferably with more standardized methods, to determine if specific clinical or radiological features of SVD are more or less associated with impaired CVR.
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Affiliation(s)
- Gordon W Blair
- Neuroimaging Sciences, Centre for Clinical Brain Science, University of Edinburgh, Edinburgh, UK
| | - Fergus N Doubal
- Neuroimaging Sciences, Centre for Clinical Brain Science, University of Edinburgh, Edinburgh, UK
| | - Michael J Thrippleton
- Neuroimaging Sciences, Centre for Clinical Brain Science, University of Edinburgh, Edinburgh, UK
| | - Ian Marshall
- Neuroimaging Sciences, Centre for Clinical Brain Science, University of Edinburgh, Edinburgh, UK
| | - Joanna M Wardlaw
- Neuroimaging Sciences, Centre for Clinical Brain Science, University of Edinburgh, Edinburgh, UK
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10
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Spain A, Howarth C, Khrapitchev AA, Sharp T, Sibson NR, Martin C. Neurovascular and neuroimaging effects of the hallucinogenic serotonin receptor agonist psilocin in the rat brain. Neuropharmacology 2015; 99:210-20. [PMID: 26192543 PMCID: PMC4655865 DOI: 10.1016/j.neuropharm.2015.07.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 06/22/2015] [Accepted: 07/16/2015] [Indexed: 12/28/2022]
Abstract
The development of pharmacological magnetic resonance imaging (phMRI) has presented the opportunity for investigation of the neurophysiological effects of drugs in vivo. Psilocin, a hallucinogen metabolised from psilocybin, was recently reported to evoke brain region-specific, phMRI signal changes in humans. The present study investigated the effects of psilocin in a rat model using phMRI and then probed the relationship between neuronal and haemodynamic responses using a multimodal measurement preparation. Psilocin (2 mg/kg or 0.03 mg/kg i.v.) or vehicle was administered to rats (N=6/group) during either phMRI scanning or concurrent imaging of cortical blood flow and recording of local field potentials. Compared to vehicle controls psilocin (2 mg/kg) evoked phMRI signal increases in a number of regions including olfactory and limbic areas and elements of the visual system. PhMRI signal decreases were seen in other regions including somatosensory and motor cortices. Investigation of neurovascular coupling revealed that whilst neuronal responses (local field potentials) to sensory stimuli were decreased in amplitude by psilocin administration, concurrently measured haemodynamic responses (cerebral blood flow) were enhanced. The present findings show that psilocin evoked region-specific changes in phMRI signals in the rat, confirming recent human data. However, the results also suggest that the haemodynamic signal changes underlying phMRI responses reflect changes in both neuronal activity and neurovascular coupling. This highlights the importance of understanding the neurovascular effects of pharmacological manipulations for interpreting haemodynamic neuroimaging data.
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Affiliation(s)
- Aisling Spain
- Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TP, UK; Cancer Research UK & Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK.
| | - Clare Howarth
- Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TP, UK; Cancer Research UK & Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK.
| | - Alexandre A Khrapitchev
- Cancer Research UK & Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK.
| | - Trevor Sharp
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, UK.
| | - Nicola R Sibson
- Cancer Research UK & Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford OX3 7DQ, UK.
| | - Chris Martin
- Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TP, UK.
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11
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Jou T, Patterson S, Pauly JM, Bowen CV. Fat-suppressed alternating-SSFP for whole-brain fMRI using breath-hold and visual stimulus paradigms. Magn Reson Med 2015; 75:1978-88. [PMID: 26037220 DOI: 10.1002/mrm.25797] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Revised: 04/24/2015] [Accepted: 05/01/2015] [Indexed: 11/07/2022]
Abstract
PURPOSE To achieve artifact-suppressed whole-brain pass-band-balanced steady-state free precession functional MRI from a single functional magnetic resonance imaging (fMRI) scan. METHODS A complete and practical data acquisition sequence for alt-SSFP fMRI was developed. First, multishot flyback-echo-planar imaging (EPI) and echo-time shifting were used to achieve data acquisition that was robust against eddy currents, gradient delays, and ghosting artifacts. Second, a steady-state catalyzation scheme was implemented to reduce oscillations in the transient signal when catalyzing in and out of alternate steady states. Next, a short spatial-spectral radiofrequency (RF) pulse was designed to achieve excellent fat-suppression while maintaining a repetition time <15 ms to sensitize functional activation toward smaller vessels and capillaries. Lastly, parallel imaging was used to achieve whole-brain coverage and sufficiently high temporal resolution. RESULTS Breath-hold experiments showed excellent fat-suppression and alt-SSFP's capability to recover functional sensitivity from signal dropout regions of conventional gradient-echo and banding artifacts from conventional pass-band-balanced steady-state free precession. Applying fat-suppression resulted in improved activation maps and increased temporal SNR. Visual stimulus functional studies verify the proposed method's excellent functional sensitivity to neuronal activation. CONCLUSION Artifact-suppressed images are demonstrated, showing a practical pass-band-balanced steady-state free precession fMRI method that permits whole-brain imaging with excellent blood oxygen level-dependent sensitivity and fat suppression.
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Affiliation(s)
- Tiffany Jou
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Steve Patterson
- Biomedical Translational Imaging Centre, Halifax, Nova Scotia, Canada
| | - John M Pauly
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Chris V Bowen
- Department of Radiology, Dalhousie University, Halifax, Nova Scotia, Canada
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12
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Viallon M, Cuvinciuc V, Delattre B, Merlini L, Barnaure-Nachbar I, Toso-Patel S, Becker M, Lovblad KO, Haller S. State-of-the-art MRI techniques in neuroradiology: principles, pitfalls, and clinical applications. Neuroradiology 2015; 57:441-67. [PMID: 25859832 DOI: 10.1007/s00234-015-1500-1] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 02/04/2015] [Indexed: 12/20/2022]
Abstract
This article reviews the most relevant state-of-the-art magnetic resonance (MR) techniques, which are clinically available to investigate brain diseases. MR acquisition techniques addressed include notably diffusion imaging (diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and diffusion kurtosis imaging (DKI)) as well as perfusion imaging (dynamic susceptibility contrast (DSC), arterial spin labeling (ASL), and dynamic contrast enhanced (DCE)). The underlying models used to process these images are described, as well as the theoretic underpinnings of quantitative diffusion and perfusion MR imaging-based methods. The technical requirements and how they may help to understand, classify, or follow-up neurological pathologies are briefly summarized. Techniques, principles, advantages but also intrinsic limitations, typical artifacts, and alternative solutions developed to overcome them are discussed. In this article, we also review routinely available three-dimensional (3D) techniques in neuro MRI, including state-of-the-art and emerging angiography sequences, and briefly introduce more recently proposed 3D quantitative neuro-anatomy sequences, and new technology, such as multi-slice and multi-transmit imaging.
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Affiliation(s)
- Magalie Viallon
- CREATIS, UMR CNRS 5220 - INSERM U1044, INSA de Lyon, Université de Lyon, Lyon, France,
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Tancredi FB, Lajoie I, Hoge RD. Test-retest reliability of cerebral blood flow and blood oxygenation level-dependent responses to hypercapnia and hyperoxia using dual-echo pseudo-continuous arterial spin labeling and step changes in the fractional composition of inspired gases. J Magn Reson Imaging 2015; 42:1144-57. [PMID: 25752936 DOI: 10.1002/jmri.24878] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 02/09/2015] [Indexed: 01/16/2023] Open
Abstract
PURPOSE To assess the reproducibility of blood oxygenation level-dependent / cerebral blood flow (BOLD/CBF) responses to hypercapnia/hyperoxia using dual-echo pseudo-continuous arterial spin labeling (pCASL) and step changes in inspired doses. MATERIALS AND METHODS Eight subjects were scanned twice, within 24 hours, using the same respiratory manipulation and imaging protocol. Imaging comprised a 5-minute anatomical acquisition, allowing segmentation of the gray matter (GM) tissue for further analysis, and an 18-minute pCASL functional scan. Hypercapnia/hyperoxia were induced by increasing the fraction of inspired CO2 to 5% and inspired O2 to 60%, alternately. Reproducibility of BOLD and CBF pCASL measures was assessed by computing the inter-session coefficient of variation (CV) of the respective signals in GM. RESULTS BOLD and CBF measures in GM were robust and consistent, yielding CV values below 10% for BOLD hypercapnic/hyperoxic responses (which averaged 1.9 ± 0.1% and 1.14 ± 0.02%) and below 20% for the CBF hypercapnic response (which averaged 35 ± 2 mL/min/100g). The CV for resting CBF was 3.5%. CONCLUSION It is possible to attain reproducible measures of the simultaneous BOLD and CBF responses to blood gases, within a reasonable scan time and with whole brain coverage, using a simple respiratory manipulation and dual-echo pCASL.
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Affiliation(s)
- Felipe B Tancredi
- Université de Montréal Institut de génie biomédical Département de physiologie C.P. 6128, Succursale Centre-ville Montréal, Québec, Canada.,Centre de recherche de l'institut universitaire de gériatrie de Montréal Unité de neuroimagerie fonctionnelle 4545, Ch. Queen Mary Montréal, Québec, Canada.,Hospital Israelita Albert Einstein Imagem Av. Albert Einstein, 627, São Paulo, SP, Brazil
| | - Isabelle Lajoie
- Université de Montréal Institut de génie biomédical Département de physiologie C.P. 6128, Succursale Centre-ville Montréal, Québec, Canada.,Centre de recherche de l'institut universitaire de gériatrie de Montréal Unité de neuroimagerie fonctionnelle 4545, Ch. Queen Mary Montréal, Québec, Canada
| | - Richard D Hoge
- Université de Montréal Institut de génie biomédical Département de physiologie C.P. 6128, Succursale Centre-ville Montréal, Québec, Canada.,Centre de recherche de l'institut universitaire de gériatrie de Montréal Unité de neuroimagerie fonctionnelle 4545, Ch. Queen Mary Montréal, Québec, Canada
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14
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Zhou Y, Rodgers ZB, Kuo AH. Cerebrovascular reactivity measured with arterial spin labeling and blood oxygen level dependent techniques. Magn Reson Imaging 2015; 33:566-76. [PMID: 25708263 DOI: 10.1016/j.mri.2015.02.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 01/17/2015] [Accepted: 02/16/2015] [Indexed: 10/24/2022]
Abstract
PURPOSE To compare cerebrovascular reactivity (CVR) quantified with pseudo-continuous arterial spin labeling (pCASL) and blood oxygen level dependent (BOLD) fMRI techniques. MATERIALS AND METHODS Sixteen healthy volunteers (age: 37.8±14.3years; 6 women and 10 men; education attainment: 17±2.1years) were recruited and completed a 5% CO2 gas-mixture breathing paradigm at 3T field strength. ASL and BOLD images were acquired for CVR determination assuming that mild hypercapnia does not affect the cerebral metabolic rate of oxygen. Both CVR quantifications were derived as the ratio of the fractional cerebral blood flow (CBF) or BOLD signal change over the change in end-tidal CO2 pressure. RESULTS The absolute CBF, BOLD and CVR measures were consistent with literature values. CBF derived CVR was 5.11±0.87%/mmHg in gray matter (GM) and 4.64±0.37%/mmHg in parenchyma. BOLD CVR was 0.23±0.04%/mmHg and 0.22±0.04%/mmHg for GM and parenchyma respectively. The most significant correlations between BOLD and CBF-based CVRs were also in GM structures, with greater vascular response in occipital cortex than in frontal and parietal lobes (6.8%/mmHg versus 4.5%/mmHg, 50% greater). Parenchymal BOLD CVR correlated significantly with the fractional change in CBF in response to hypercapnia (r=0.61, P=0.01), suggesting the BOLD response to be significantly flow driven. GM CBF decreased with age in room air (-5.58mL/100g/min per decade for GM; r=-0.51, P=0.05), but there was no association of CBF with age during hypercapnia. A trend toward increased pCASL CVR with age was observed, scaling as 0.64%/mmHg per decade for GM. CONCLUSION Consistent with previously reported CVR values, our results suggest that BOLD and CBF CVR techniques are complementary to each other in evaluating neuronal and vascular underpinning of hemodynamic processes.
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Affiliation(s)
- Yongxia Zhou
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104.
| | - Zachary B Rodgers
- Department of Radiology, University of Pennsylvania, Philadelphia, PA 19104
| | - Anderson H Kuo
- Department of Radiology, University of Texas South Medical Center, San Antonio, TX
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15
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Reproducibility of hypocapnic cerebrovascular reactivity measurements using BOLD fMRI in combination with a paced deep breathing task. Neuroimage 2014; 98:31-41. [DOI: 10.1016/j.neuroimage.2014.04.049] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 04/14/2014] [Accepted: 04/16/2014] [Indexed: 11/23/2022] Open
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Xia J, Xie N, Feng Y, Yin A, Liu P, Zhou R, Lin F, Teng G, Lei Y. Brain susceptibility weighted imaging signal changes in acute hemorrhagic anemia: an experimental study using a rabbit model. Med Sci Monit 2014; 20:1291-7. [PMID: 25060330 PMCID: PMC4116343 DOI: 10.12659/msm.890641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 04/09/2014] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND The aim of this study was to investigate susceptibility-weighted imaging (SWI) signal changes in different brain regions in a rabbit model of acute hemorrhagic anemia. MATERIAL/METHODS Ten New Zealand white rabbits were used for construction of the model of acute hemorrhagic anemia. Signal intensities of SWI images of the bilateral frontal cortex, frontal white matter, temporal lobe, and thalamic nuclei were measured. In addition, the cerebral gray-white contrast and venous structures of the SWI images were evaluated by an experienced physician. RESULTS Repeated bloodletting was associated with significant reductions in red blood cell count, hemoglobin concentration, hematocrit, pH, and PaCO2, and elevations of blood lactate and PaO2. In normal status, the SWI signal intensity was significantly higher in the frontal cortex than in the frontal white matter (63.10±22.82 vs. 52.50±20.29; P<0.05). Repeated bloodletting (5 occasions) caused significant (P<0.05) decreases in the SWI signals of the frontal cortex (from 63.10±22.82 to 37.70±4.32), temporal lobe (from 52.50±20.29 to 42.60±5.54), and thalamus (from 60.40±20.29 to 39.40±3.47), but was without effect in the frontal white matter. The cerebral white-gray contrast and venous structures were clearer after bloodletting than before bloodletting. CONCLUSIONS The effect of hemorrhage on the brain is reflected by SWI signal changes in the cerebral cortex and gray matter nuclei.
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Affiliation(s)
- Jun Xia
- Department of Radiology, Second People’s Hospital of Shenzhen City, First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
| | - Ni Xie
- Biobank, Second People’s Hospital of Shenzhen City, First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
| | - Yuning Feng
- Department of Radiology, Second People’s Hospital of Shenzhen City, First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
| | - Anyu Yin
- Department of Radiology, Second People’s Hospital of Shenzhen City, First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
| | - Pinni Liu
- Department of Radiology, Second People’s Hospital of Shenzhen City, First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
| | - Ruming Zhou
- Department of Interventional Radiology, Second People’s Hospital of Shenzhen City, First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
| | - Fan Lin
- Department of Radiology, Second People’s Hospital of Shenzhen City, First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
| | - Guozhao Teng
- Medical Record and Statistics Room, Second People’s Hospital of Shenzhen City. First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
| | - Yi Lei
- Department of Radiology, Second People’s Hospital of Shenzhen City, First Affiliated Hospital of Shenzhen University, Shenzhen, Guangdong province, China
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17
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Kannurpatti SS, Motes MA, Biswal BB, Rypma B. Assessment of unconstrained cerebrovascular reactivity marker for large age-range FMRI studies. PLoS One 2014; 9:e88751. [PMID: 24551151 PMCID: PMC3923811 DOI: 10.1371/journal.pone.0088751] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 01/12/2014] [Indexed: 11/23/2022] Open
Abstract
Breath hold (BH), a commonly used task to measure cerebrovascular reactivity (CVR) in fMRI studies varies in outcome among individuals due to subject-physiology and/or BH-inspiration/expiration differences (i.e., performance). In prior age-related fMRI studies, smaller task-related BOLD response variability is observed among younger than older individuals. Also, a linear CVR versus task relationship exists in younger individuals which maybe useful to test the accuracy of CVR responses in older groups. Hence we hypothesized that subject-related physiological and/or BH differences, if present, may compromise CVR versus task linearity in older individuals. To test the hypothesis, empirical BH versus task relationships from motor and cognitive areas were obtained in younger (mean age = 26 years) and older (mean age = 58 years) human subjects. BH versus task linearity was observed only in the younger group, confirming our hypothesis. Further analysis indicated BH responses and its variability to be similar in both younger and older groups, suggesting that BH may not accurately represent CVR in a large age range. Using the resting state fluctuation of amplitude (RSFA) as an unconstrained alternative to BH, subject-wise correspondence between BH and RSFA was tested. Correlation between BH versus RSFA was significant within the motor but was not significant in the cognitive areas in the younger and was completely disrupted in both areas in the older subjects indicating that BH responses are constrained by subject-related physiology and/or performance-related differences. Contrasting BH to task, RSFA-task relationships were independent of age accompanied by age-related increases in CVR variability as measured by RSFA, not observed with BH. Together the results obtained indicate that RSFA accurately represents CVR in any age range avoiding multiple and yet unknown physiologic and task-related pitfalls of BH.
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Affiliation(s)
- Sridhar S. Kannurpatti
- Department of Radiology, RUTGERS-New Jersey Medical School, Newark, New Jersey, United States of America
- * E-mail: (SSK) (SK); (BR) (BR)
| | - Michael A. Motes
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, Texas, United States of America
| | - Bharat B. Biswal
- Department of Radiology, RUTGERS-New Jersey Medical School, Newark, New Jersey, United States of America
- Department of Biomedical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States of America
| | - Bart Rypma
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, Texas, United States of America
- * E-mail: (SSK) (SK); (BR) (BR)
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18
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Wilson SM. The impact of vascular factors on language localization in the superior temporal sulcus. Hum Brain Mapp 2014; 35:4049-63. [PMID: 24452906 DOI: 10.1002/hbm.22457] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 11/27/2013] [Accepted: 12/16/2013] [Indexed: 11/07/2022] Open
Abstract
The left superior temporal sulcus (STS) has been shown in numerous functional imaging studies to be a critical region for language processing, as it is reliably activated when language comprehension is compared with acoustically matched control conditions. Studies in non-human primates have demonstrated several subdivisions in the STS, yet the precise region(s) within the STS that are important for language remain unclear, in large part because the presence of draining veins in the sulcus makes it difficult to determine whether neural activity is localized to the dorsal or ventral bank of the sulcus. We used functional MRI to localize language regions, and then acquired several additional sequences in order to account for the impact of vascular factors. A breath-holding task was used to induce hypercapnia in order to normalize voxel-wise differences in blood oxygen level-dependent (BOLD) responsivity, and veins were identified on susceptibility-weighted and T2*-weighted BOLD images, and masked out. We found that the precise locations of language areas in individual participants were strongly influenced by vascular factors, but that these vascular effects could be ameliorated by hypercapnic normalization and vein masking. After these corrections were applied, the majority of regions activated by language processing were localized to the dorsal bank of the STS.
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Affiliation(s)
- Stephen M Wilson
- Department of Speech, Language, and Hearing Sciences, University of Arizona, Tucson, Arizona; Department of Neurology, University of Arizona, Tucson, Arizona
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19
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Chang K, Barnes S, Haacke EM, Grossman RI, Ge Y. Imaging the effects of oxygen saturation changes in voluntary apnea and hyperventilation on susceptibility-weighted imaging. AJNR Am J Neuroradiol 2013; 35:1091-5. [PMID: 24371029 DOI: 10.3174/ajnr.a3818] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND AND PURPOSE Cerebrovascular oxygenation changes during respiratory challenges have clinically important implications for brain function, including cerebral autoregulation and the rate of brain metabolism. SWI is sensitive to venous oxygenation level by exploitation of the magnetic susceptibility of deoxygenated blood. We assessed cerebral venous blood oxygenation changes during simple voluntary breath-holding (apnea) and hyperventilation by use of SWI at 3T. MATERIALS AND METHODS We performed SWI scans (3T; acquisition time of 1 minute, 28 seconds; centered on the anterior commissure and the posterior commissure) on 10 healthy male volunteers during baseline breathing as well as during simple voluntary hyperventilation and apnea challenges. The hyperventilation and apnea tasks were separated by a 5-minute resting period. SWI venograms were generated, and the signal changes on SWI before and after the respiratory stress tasks were compared by means of a paired Student t test. RESULTS Changes in venous vasculature visibility caused by the respiratory challenges were directly visualized on the SWI venograms. The venogram segmentation results showed that voluntary apnea decreased the mean venous blood voxel number by 1.6% (P < .0001), and hyperventilation increased the mean venous blood voxel number by 2.7% (P < .0001). These results can be explained by blood CO2 changes secondary to the respiratory challenges, which can alter cerebrovascular tone and cerebral blood flow and ultimately affect venous oxygen levels. CONCLUSIONS These results highlight the sensitivity of SWI to simple and noninvasive respiratory challenges and its potential utility in assessing cerebral hemodynamics and vasomotor responses.
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Affiliation(s)
- K Chang
- From the Department of Radiology (K.C., R.I.G., Y.G.), Center for Biomedical Imaging, New York University School of Medicine, New York, New York
| | - S Barnes
- Division of Biology (S.B.), Caltech, Pasadena, California
| | - E M Haacke
- Department of Radiology (E.M.H.), Wayne State University School of Medicine, Detroit, Michigan
| | - R I Grossman
- From the Department of Radiology (K.C., R.I.G., Y.G.), Center for Biomedical Imaging, New York University School of Medicine, New York, New York
| | - Y Ge
- From the Department of Radiology (K.C., R.I.G., Y.G.), Center for Biomedical Imaging, New York University School of Medicine, New York, New York
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20
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Measurement of brain oxygenation changes using dynamic T1-weighted imaging. Neuroimage 2013; 78:7-15. [DOI: 10.1016/j.neuroimage.2013.03.068] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 03/25/2013] [Accepted: 03/28/2013] [Indexed: 11/30/2022] Open
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21
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Comparison of cerebral vascular reactivity measures obtained using breath-holding and CO2 inhalation. J Cereb Blood Flow Metab 2013; 33:1066-74. [PMID: 23571282 PMCID: PMC3705433 DOI: 10.1038/jcbfm.2013.48] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 02/05/2013] [Accepted: 03/03/2013] [Indexed: 11/09/2022]
Abstract
Stimulation of cerebral vasculature using hypercapnia has been widely used to study cerebral vascular reactivity (CVR), which can be expressed as the quantitative change in cerebral blood flow (CBF) per mm Hg change in end-tidal partial pressure of CO2 (PETCO2). We investigate whether different respiratory manipulations, with arterial spin labeling used to measure CBF, lead to consistent measures of CVR. The approaches included: (1) an automated system delivering variable concentrations of inspired CO2 for prospective targeting of PETCO2, (2) administration of a fixed concentration of CO2 leading to subject-dependent changes in PETCO2, (3) a breath-hold (BH) paradigm with physiologic modeling of CO2 accumulation, and (4) a maneuver combining breath-hold and hyperventilation. When CVR was expressed as the percent change in CBF per mm Hg change in PETCO2, methods 1 to 3 gave consistent results. The CVR values using method 4 were significantly lower. When CVR was expressed in terms of the absolute change in CBF (mL/100 g per minute per mm Hg), greater discrepancies became apparent: methods 2 and 3 gave lower absolute CVR values compared with method 1, and the value obtained with method 4 was dramatically lower. Our findings indicate that care must be taken to ensure that CVR is measured over the linear range of the CBF-CO2 dose-response curve, avoiding hypocapnic conditions.
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Artzi M, Aizenstein O, Abramovitch R, Bashat DB. MRI multiparametric hemodynamic characterization of the normal brain. Neuroscience 2013; 240:269-76. [PMID: 23500143 DOI: 10.1016/j.neuroscience.2013.03.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 03/03/2013] [Accepted: 03/05/2013] [Indexed: 02/04/2023]
Abstract
Characterization of the brain's vascular system is of major clinical importance in the assessment of patients with cerebrovascular disease. The aim of this study was to characterize brain hemodynamics using multiparametric methods and to obtain reference values from the healthy brain. A multimodal magnetic resonance imaging (MRI) study was performed in twenty healthy subjects, including dynamic susceptibility contrast imaging and blood oxygen level dependence (BOLD) during hypercapnia and carbogen challenges. Brain tissues were defined using unsupervised cluster analysis based on these three methods, and several hemodynamic parameters were calculated for gray matter (GM), white matter (WM), blood vessels and dura (BVD); the three main vascular territories within the GM; and arteries and veins defined within the BVD cluster. The carbogen challenge produced a BOLD signal twice as high as the hypercapnia challenge, in all brain tissues. The three brain tissues differed significantly from each other in their hemodynamic characteristics, supporting the graded vascularity of the tissues, with BVD>GM>WM. Within the GM cluster, a significant delay of ∼1.2 s of the bolus arrival time was detected within the posterior cerebral artery territory relative to the middle and anterior cerebral artery territories. No differences were detected between right and left middle cerebral artery territories for all hemodynamic parameters. Within the BVD cluster, a significant delay of ∼1.9 s of the bolus arrival time was detected within the veins relative to the arteries. This parameter enabled to differentiate between the various blood vessels, including arteries, veins and choroid plexus. This study provides reference values for several hemodynamic parameters, obtained from healthy brains, and may be clinically important in the assessment of patients with various vascular pathologies.
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Affiliation(s)
- M Artzi
- The Functional Brain Center, The Wohl Institute for Advanced Imaging, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
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23
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Hsu YY, Chu WC, Lim KE, Liu HL. Vascular space occupancy MRI during breathholding at 3 Tesla. J Magn Reson Imaging 2012; 36:1179-85. [PMID: 22791565 DOI: 10.1002/jmri.23745] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2011] [Accepted: 06/01/2012] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To evaluate the vasodilatory response of normal human brain and meningiomas under repeated breathholding challenges using vascular space occupancy (VASO) MRI at 3 Tesla (T). MATERIALS AND METHODS Five normal volunteers and five patients with meningiomas were recruited for this study. For the normal group, VASO MRI during repeated breathholds of different duration (5 to 30 s) was acquired. Patients performed a 15-s breathhold paradigm for VASO MRI. The maximum signal change and full-width at half-maximum (FWHM) were determined by curve fitting. RESULTS Significant VASO signal decreases in the gray matter could be detected for a breathhold period as short as 5 s. The fractional activation volume vs. breathhold duration reached a plateau around 34.21 ± 3.39% at 15 s. In the patient group, there were significant VASO signal decreases in normal gray matters and also in small areas of three large-sized meningiomas. CONCLUSION The 3T VASO MRI detected significant signal decreases in the gray matter, but not in the white matter, during short periods of breathholding. The fractional activation volume reached the plateau at 15-s breathhold, which is recommended for clinical application.
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Affiliation(s)
- Yuan-Yu Hsu
- Department of Medical Imaging, Buddhist Tzu Chi General Hospital, Taipei, Taiwan
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Assessing Cerebrovascular Reactivity in Carotid Steno-Occlusive Disease Using MRI BOLD and ASL Techniques. Radiol Res Pract 2012; 2012:268483. [PMID: 22919485 PMCID: PMC3388310 DOI: 10.1155/2012/268483] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 04/17/2012] [Accepted: 04/17/2012] [Indexed: 12/13/2022] Open
Abstract
Impaired cerebrovascular reactivity (CVR), a predictive factor of imminent stroke, has been shown to be associated with carotid steno-occlusive disease. Magnetic resonance imaging (MRI) techniques, such as blood oxygenation level-dependent (BOLD) and arterial spin labeling (ASL), have emerged as promising noninvasive tools to evaluate altered CVR with whole-brain coverage, when combined with a vasoactive stimulus, such as respiratory task or injection of acetazolamide. Under normal cerebrovascular conditions, CVR has been shown to be globally and homogenously distributed between hemispheres, but with differences among cerebral regions. Such differences can be explained by anatomical specificities and different biochemical mechanisms responsible for vascular regulation. In patients with carotid steno-occlusive disease, studies have shown that MRI techniques can detect impaired CVR in brain tissue supplied by the affected artery. Moreover, resulting CVR estimations have been well correlated to those obtained with more established techniques, indicating that BOLD and ASL are robust and reliable methods to assess CVR in patients with cerebrovascular diseases. Therefore, the present paper aims to review recent studies which use BOLD and ASL to evaluate CVR, in healthy individuals and in patients with carotid steno-occlusive disease, providing a source of information regarding the obtained results and the methodological difficulties.
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25
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Zhang Y, Peng Q, Kiel JW, Rosende CA, Duong TQ. Magnetic resonance imaging of vascular oxygenation changes during hyperoxia and carbogen challenges in the human retina. Invest Ophthalmol Vis Sci 2011; 52:286-91. [PMID: 20847121 PMCID: PMC3053278 DOI: 10.1167/iovs.10-6108] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Revised: 08/11/2010] [Accepted: 08/11/2010] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To demonstrate blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) of vascular oxygenation changes in normal, unanesthetized human retinas associated with oxygen and carbogen challenge. METHODS MRI was performed with a 3-T human scanner and a custom-made surface-coil detector on normal volunteers. BOLD MRI with inversion recovery was used to suppress the vitreous signal. During MRI measurements, volunteers underwent three episodes of air and 100% oxygen or carbogen (5% CO(2) and 95% O(2)) breathing. Eye movement was effectively managed with eye fixation, synchronized blinks, and postprocessing image coregistration. BOLD time-series images were analyzed using the cross-correlation method. Percent changes due to oxygen or carbogen inhalation versus air were tabulated for whole-retina and different regions of the retina. RESULTS Robust BOLD responses were detected. BOLD MRI percent change from a large region of interest at the posterior pole of the retina was 5.2 ± 1.5% (N = 9 trials from five subjects) for oxygen inhalation and 5.2 ± 1.3% (N = 11 trials from five subjects) for carbogen inhalation. Group-averaged BOLD percent changes were not significantly different between oxygen and carbogen challenges (P > 0.05). The foveal region had greater BOLD response compared with the optic nerve head region for both challenges. CONCLUSIONS BOLD retinal responses to oxygen and carbogen breathing in unanesthetized humans can be reliably imaged at high spatiotemporal resolution. BOLD MRI has the potential to provide a valuable tool to study retinal physiology and pathophysiology, such as how vascular oxygenation at the tissue level is regulated in the normal retina, and how retinal diseases may affect oxygen response.
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Affiliation(s)
- Yi Zhang
- From the Research Imaging Institute and
- the Departments of Radiology
| | - Qi Peng
- From the Research Imaging Institute and
- the Departments of Radiology
| | | | | | - Timothy Q. Duong
- From the Research Imaging Institute and
- the Departments of Radiology
- Ophthalmology, and
- Physiology, University of Texas Health Science Center, San Antonio, Texas; and
- South Texas Veterans Health Care System, San Antonio, Texas
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Wise RG, Pattinson KTS, Bulte DP, Rogers R, Tracey I, Matthews PM, Jezzard P. Measurement of relative cerebral blood volume using BOLD contrast and mild hypoxic hypoxia. Magn Reson Imaging 2010; 28:1129-34. [PMID: 20685053 DOI: 10.1016/j.mri.2010.06.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 05/17/2010] [Accepted: 06/18/2010] [Indexed: 11/28/2022]
Abstract
Relative cerebral blood volume (CBV) was estimated using a mild hypoxic challenge in humans, combined with BOLD contrast gradient-echo imaging at 3 T. Subjects breathed 16% inspired oxygen, eliciting mild arterial desaturation. The fractional BOLD signal change induced by mild hypoxia is expected to be proportional to CBV under conditions in which there are negligible changes in cerebral perfusion. By comparing the regional BOLD signal changes arising with the transition between normoxia and mild hypoxia, we calculated CBV ratios of 1.5 ± 0.2 (mean ± S.D.) for cortical gray matter to white matter and 1.0 ± 0.3 for cortical gray matter to deep gray matter.
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Affiliation(s)
- Richard G Wise
- Department of Clinical Neurology, Centre for Functional Magnetic Resonance Imaging of the Brain, John Radcliffe Hospital, University of Oxford, Oxford, UK
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Conklin J, Fierstra J, Crawley AP, Han JS, Poublanc J, Mandell DM, Silver FL, Tymianski M, Fisher JA, Mikulis DJ. Impaired cerebrovascular reactivity with steal phenomenon is associated with increased diffusion in white matter of patients with Moyamoya disease. Stroke 2010; 41:1610-6. [PMID: 20576954 DOI: 10.1161/strokeaha.110.579540] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND AND PURPOSE Reduced cerebrovascular reactivity (CVR) with steal phenomenon is an independent predictor for stroke and may indicate tissue exposed to episodic low-grade ischemia. The apparent diffusion coefficient (ADC) calculated using diffusion-weighted MRI is effective in characterizing focal brain ischemia and subtle structural changes in normal-appearing white matter (WM). We hypothesized that regions of steal phenomenon are associated with increased ADC in normal-appearing WM of patients with Moyamoya disease. METHODS Twenty-two patients with unilateral CVR impairment secondary to Moyamoya disease and 12 healthy control subjects underwent diffusion-weighted MRI and functional MRI mapping of the cerebrovascular response to hypercapnia. Parametric maps of ADC and CVR were calculated, coregistered, and segmented using automated image processing methods. ADC of normal-appearing WM was compared between hemispheres, and between WM with negative CVR (ie, steal phenomenon) and WM with positive CVR. RESULTS In patients, ADC of normal-appearing WM was elevated in the hemisphere ipsilateral to the CVR impairment compared with the contralateral hemisphere (P<0.005) and in WM with negative CVR compared with WM with positive CVR (P<0.001). WM in regions of steal phenomenon within the affected hemisphere had higher ADC than homologous contralateral WM (P<0.005). In control subjects, negative CVR in WM was not associated with elevated ADC. CONCLUSIONS Regions of steal phenomenon are spatially correlated with elevated ADC in normal-appearing WM of patients with Moyamoya disease. This structural abnormality may reflect low-grade ischemic injury after exhaustion of the cerebrovascular reserve capacity.
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Affiliation(s)
- John Conklin
- Department of Medical Imaging, Toronto Western Hospital, Toronto, Ontario, Canada
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28
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Rioja E, Kerr CL, McDonell WN, Dobson H, Konyer NB, Poma R, Noseworthy MD. Effects of hypercapnia, hypocapnia, and hyperoxemia on blood oxygenation level-dependent signal intensity determined by use of susceptibility-weighted magnetic resonance imaging in isoflurane-anesthetized dogs. Am J Vet Res 2010; 71:24-32. [PMID: 20043777 DOI: 10.2460/ajvr.71.1.24] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To assess the effects of alterations in PaCO(2) and PaO(2) on blood oxygenation level-dependent (BOLD) signal intensity determined by use of susceptibility-weighted magnetic resonance imaging in brains of isoflurane-anesthetized dogs. ANIMALS 6 healthy dogs. PROCEDURES In each dog, anesthesia was induced with propofol (6 to 8 mg/kg, IV) and maintained with isoflurane (1.7%) and atracurium (0.2 mg/kg, IV, q 30 min). During 1 magnetic resonance imaging session in each dog, targeted values of PaCO(2) (20, 40, or 80 mm Hg) and PaO(2) (100 or 500 mm Hg) were combined to establish 6 experimental conditions, including a control condition (PaCO(2), 40 mm Hg; PaO(2), 100 mm Hg). Dogs were randomly assigned to different sequences of conditions. Each condition was established for a period of >or= 5 minutes before susceptibility-weighted imaging was performed. Signal intensity was measured in 6 regions of interest in the brain, and data were analyzed by use of an ANCOVA and post hoc Tukey-Kramer adjustments. RESULTS Compared with control condition findings, BOLD signal intensity did not differ significantly in any region of interest. However, signal intensities in the thalamus and diencephalic gray matter decreased significantly during both hypocapnic conditions, compared with all other conditions except for the control condition. CONCLUSIONS AND CLINICAL RELEVANCE In isoflurane-anesthetized dogs, certain regions of gray matter appeared to have greater cerebrovascular responses to changes in PaCO(2) and PaO(2) than did others. Both PaO(2) and PaCO(2) should be controlled during magnetic resonance imaging procedures that involve BOLD signaling and taken into account when interpreting findings.
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Affiliation(s)
- Eva Rioja
- Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada.
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29
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Hsu YY, Kuan WC, Lim KE, Liu HL. Breathhold-regulated blood oxygenation level-dependent (BOLD) MRI of human brain at 3 tesla. J Magn Reson Imaging 2009; 31:78-84. [DOI: 10.1002/jmri.22015] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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30
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Kiviniemi V, Remes J, Starck T, Nikkinen J, Haapea M, Silven O, Tervonen O. Mapping Transient Hyperventilation Induced Alterations with Estimates of the Multi-Scale Dynamics of BOLD Signal. Front Neuroinform 2009; 3:18. [PMID: 19636388 PMCID: PMC2715265 DOI: 10.3389/neuro.11.018.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Accepted: 06/22/2009] [Indexed: 11/24/2022] Open
Abstract
Temporal blood oxygen level dependent (BOLD) contrast signals in functional MRI during rest may be characterized by power spectral distribution (PSD) trends of the form 1/f(alpha). Trends with 1/f characteristics comprise fractal properties with repeating oscillation patterns in multiple time scales. Estimates of the fractal properties enable the quantification of phenomena that may otherwise be difficult to measure, such as transient, non-linear changes. In this study it was hypothesized that the fractal metrics of 1/f BOLD signal trends can map changes related to dynamic, multi-scale alterations in cerebral blood flow (CBF) after a transient hyperventilation challenge. Twenty-three normal adults were imaged in a resting-state before and after hyperventilation. Different variables (1/f trend constant alpha, fractal dimension D(f), and, Hurst exponent H) characterizing the trends were measured from BOLD signals. The results show that fractal metrics of the BOLD signal follow the fractional Gaussian noise model, even during the dynamic CBF change that follows hyperventilation. The most dominant effect on the fractal metrics was detected in grey matter, in line with previous hyperventilation vaso-reactivity studies. The alpha was able to differentiate also blood vessels from grey matter changes. D(f) was most sensitive to grey matter. H correlated with default mode network areas before hyperventilation but this pattern vanished after hyperventilation due to a global increase in H. In the future, resting-state fMRI combined with fractal metrics of the BOLD signal may be used for analyzing multi-scale alterations of cerebral blood flow.
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Affiliation(s)
- Vesa Kiviniemi
- Department of Diagnostic Radiology, Oulu University HospitalOulu, Finland
| | - Jukka Remes
- Department of Diagnostic Radiology, Oulu University HospitalOulu, Finland
- Department of Information and Electrical Engineering, University of OuluOulu, Finland
| | - Tuomo Starck
- Department of Diagnostic Radiology, Oulu University HospitalOulu, Finland
| | - Juha Nikkinen
- Department of Diagnostic Radiology, Oulu University HospitalOulu, Finland
| | - Marianne Haapea
- Department of Diagnostic Radiology, Oulu University HospitalOulu, Finland
| | - Olli Silven
- Department of Information and Electrical Engineering, University of OuluOulu, Finland
| | - Osmo Tervonen
- Department of Diagnostic Radiology, Oulu University HospitalOulu, Finland
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Lu J, Dai G, Egi Y, Huang S, Kwon SJ, Lo EH, Kim YR. Characterization of cerebrovascular responses to hyperoxia and hypercapnia using MRI in rat. Neuroimage 2009; 45:1126-34. [DOI: 10.1016/j.neuroimage.2008.11.037] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 11/04/2008] [Accepted: 11/25/2008] [Indexed: 01/08/2023] Open
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32
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Bacigaluppi S, Dehdashti AR, Agid R, Krings T, Tymianski M, Mikulis DJ. The contribution of imaging in diagnosis, preoperative assessment, and follow-up of moyamoya disease. Neurosurg Focus 2009; 26:E3. [DOI: 10.3171/2009.01.focus08296] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The aim of this review was to evaluate the imaging tools used in diagnosis and perioperative assessment of moyamoya disease, with particular attention to the last decade.
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Affiliation(s)
- Susanna Bacigaluppi
- 1Divisions of Neurosurgery and
- 3Department of Neurosciences and Biomedical Technologies, University of Milan-Bicocca, Milan, Italy
| | | | - Ronit Agid
- 2Neuroradiology, University Health Network, Toronto Western Hospital, University of Toronto, Ontario, Canada; and
| | - Timo Krings
- 2Neuroradiology, University Health Network, Toronto Western Hospital, University of Toronto, Ontario, Canada; and
| | | | - David J. Mikulis
- 2Neuroradiology, University Health Network, Toronto Western Hospital, University of Toronto, Ontario, Canada; and
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33
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Haller S, Bonati LH, Rick J, Klarhöfer M, Speck O, Lyrer PA, Bilecen D, Engelter ST, Wetzel SG. Reduced cerebrovascular reserve at CO2 BOLD MR imaging is associated with increased risk of periinterventional ischemic lesions during carotid endarterectomy or stent placement: preliminary results. Radiology 2008; 249:251-8. [PMID: 18796680 DOI: 10.1148/radiol.2491071644] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
PURPOSE To determine whether any initial reductions in cardiovascular reserve (CVR) normalize after carotid revascularization and-because reduced CVR represents a risk factor for ischemic events-whether patients who develop periinterventional infarction have more severely reduced pretreatment CVR than those who do not. MATERIALS AND METHODS Ethics committee approval and informed consent were obtained. Twenty-four consecutive patients with symptomatic high-grade internal carotid artery stenosis (seven women; mean age, 73.1 years +/- 9.4 [standard deviation]) were recruited from a prospective, randomized trial that compared carotid artery stent placement with endarterectomy. Magnetic resonance (MR) imaging, including CO(2) blood oxygen level-dependent (BOLD) MR, was performed 1-3 days before, 1-3 days after, and 1 month after carotid revascularization (carotid artery stent placement, n = 13; carotid endarterectomy, n = 11). RESULTS Mean CVR in the ipsilateral middle cerebral artery (MCA) territory was reduced prior to treatment (mean DeltaT2* in ipsilateral territory, 1.92% +/- 1.18; mean DeltaT2* in contralateral territory, 2.28% +/- 1.15 [P < .05]) and normalized after treatment (mean DeltaT2* 1-3 days after treatment in ipsilateral territory, 2.66% +/- 1.01; that in contralateral territory, 2.48% +/- 1.27 [P > .05]; mean DeltaT2* 1 month after treatment in ipsilateral territory, 2.27% +/- 1.05; that in contralateral territory, 2.14% +/- 0.96 [P > .05]). Those patients who developed new periinterventional infarcts (n = 7 with punctate foci of restricted diffusion) had greater reduction of CVR in the ipsilateral MCA territory prior to treatment (relative reduction, 32.5% +/- 46.0; P < .05) than those who did not develop infarction (n = 17; relative reduction, 9.2% +/- 55.9). CONCLUSION CO(2) BOLD MR imaging could be used successfully to monitor the hemodynamic effects of carotid revascularization; initial reductions in CVR normalized after carotid revascularization. Severely reduced pretreatment CVR was associated with increased occurrence of new periinterventional therapy infarction.
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Affiliation(s)
- Sven Haller
- Department of Diagnostic and Interventional Neuroradiology, Institute of Radiology, University Hospital Basel, Petersgraben 4, CH-4031 Basel, Switzerland.
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34
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Mandell DM, Han JS, Poublanc J, Crawley AP, Stainsby JA, Fisher JA, Mikulis DJ. Mapping cerebrovascular reactivity using blood oxygen level-dependent MRI in Patients with arterial steno-occlusive disease: comparison with arterial spin labeling MRI. Stroke 2008; 39:2021-8. [PMID: 18451352 DOI: 10.1161/strokeaha.107.506709] [Citation(s) in RCA: 181] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND AND PURPOSE Blood oxygen level-dependent MRI (BOLD MRI) of hypercapnia-induced changes in cerebral blood flow is an emerging technique for mapping cerebrovascular reactivity (CVR). BOLD MRI signal reflects cerebral blood flow, but also depends on cerebral blood volume, cerebral metabolic rate, arterial oxygenation, and hematocrit. The purpose of this study was to determine whether, in patients with stenoocclusive disease, the BOLD MRI signal response to hypercapnia is directly related to changes in cerebral blood flow. METHODS Thirty-eight patients with stenoocclusive disease underwent mapping of CVR by both BOLD MRI and arterial spin labeling MRI. The latter technique was used as a reference standard for measurement of cerebral blood flow changes. RESULTS Hemispheric CVR measured by BOLD MRI was significantly correlated with that measured by arterial spin labeling MRI for both gray matter (R=0.83, P<0.0001) and white matter (R=0.80, P<0.0001). Diagnostic accuracy (area under receiver operating characteristic curve) for BOLD MRI discrimination between normal and abnormal hemispheric CVR was 0.90 (95% CI=0.81 to 0.98; P<0.001) for gray matter and 0.82 (95% CI=0.70 to 0.94; P<0.001) for white matter. Regions of paradoxical CVR on BOLD MRI had a moderate predictive value (14 of 19 hemispheres) for spatially corresponding paradoxical CVR on arterial spin labeling MRI. Complete absence of paradoxical CVR on BOLD MRI had a high predictive value (31 of 31 hemispheres) for corresponding nonparadoxical CVR on arterial spin labeling MRI. CONCLUSIONS Arterial spin labeling MRI confirms that, even in patients with stenoocclusive disease, the BOLD MRI signal response to hypercapnia predominantly reflects changes in cerebral blood flow.
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Affiliation(s)
- Daniel M Mandell
- Department of Medical Imaging, Toronto Western Hospital, Toronto, Ontario M5T 2S8, Canada
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35
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Scouten A, Constable RT. VASO-based calculations of CBV change: accounting for the dynamic CSF volume. Magn Reson Med 2008; 59:308-15. [PMID: 18228581 DOI: 10.1002/mrm.21427] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The goal of the vascular space occupancy (VASO) imaging technique is to use selective nulling of the blood signal to infer relative changes in cerebral blood volume (CBV). In accordance with recent work, we show that changes in the local CSF fraction (x(c)) with activation can significantly impact the VASO signal, thereby limiting our ability to infer DeltaCBV from DeltaVASO alone. Here we calculate CBV change using a VASO-based method which ACcounts for the Dynamic Cerebrospinal (ACDC) fluid fraction. By combining data from two separate VASO acquisitions that eliminate either the blood signal (VASO(b)) or the CSF signal (VASO(c)), a nonlinear least-squares optimization may then be used to simultaneously solve for the relative changes in CBV and CSF with activation. The method is applied across the whole brain during a breath-holding task, offering insight into the relationship between changes in CBV and x(c) associated with global vasodilatation. Calculations of mean changes in CBV in different volumes of interest obtained from the proposed method compare much better with previous (gold-standard) PET data than traditional VASO methods that do not account for a nonzero Deltax(c) with activation. This confirms the necessity of incorporating the dynamic CSF volume into VASO-based calculations of DeltaCBV.
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Affiliation(s)
- A Scouten
- Department of Biomedical Engineering, Yale University School of Medicine, 300 Cedar Street, New Haven, CT 06520, USA.
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36
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Andrade KC, Pontes-Neto OM, Leite JP, Santos AC, Baffa O, de Araujo DB. Quantitative aspects of brain perfusion dynamic induced by BOLD fMRI. ARQUIVOS DE NEURO-PSIQUIATRIA 2008; 64:895-8. [PMID: 17220991 DOI: 10.1590/s0004-282x2006000600001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2006] [Accepted: 08/24/2006] [Indexed: 11/22/2022]
Abstract
The increase of relative cerebral blood flow (rCBF) may contribute for a change in blood oxygenation level dependent signal (BOLD). The main purpose of this study is to investigate some aspects of perfusional alterations in the human brain in response to a uniform stimulation: hypercapnia induced by breath holding. It was observed that the BOLD signal increased globally during hypercapnia and that it is correlated with the time of breath holding. This signal increase shows a clear distinction between gray and white matter, being greater in the grey matter.
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Affiliation(s)
- Katia C Andrade
- Dept. of Physics and Math, FFCLRP, USP, Ribeirão Preto, SP, Brazil
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37
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Uematsu H, Takahashi M, Hatabu H, Chin CL, Wehrli SL, Wehrli FW, Asakura T. Changes in T1 and T2 observed in brain magnetic resonance imaging with delivery of high concentrations of oxygen. J Comput Assist Tomogr 2007; 31:662-5. [PMID: 17895773 DOI: 10.1097/rct.0b013e3180319114] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The aim of this study was to clarify the relative contributions of the amount of oxygen in the blood, and vasoconstriction/dilation responsible for changes in T1 and T2 observed in brain during hyperoxia. METHODS T1 and T2 values of the cerebral cortex and pituitary gland in mice were determined in room air. After room air was changed to either 100% oxygen (n = 8) or carbogen (n = 8), T1 and T2 values were again determined. Changes in each value with both gases were compared. RESULTS In both challenges, T1 values of the cerebral cortex decreased, whereas significant T2 prolongation of the cerebral cortex and pituitary gland was demonstrated. However, both cortex and pituitary gland displayed similar responses in T1 and T2 values when exposed to 100% oxygen or carbogen. CONCLUSIONS Reduction of T1 was introduced by the increased amount of dissolved oxygen in blood, and the increased fraction of oxyhemoglobin caused T2 prolongation. The contribution of vasoconstriction/dilation by carbogen to changes in T1 and T2 may be negligible.
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38
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Pattinson KTS, Rogers R, Mayhew SD, Tracey I, Wise RG. Pharmacological FMRI: measuring opioid effects on the BOLD response to hypercapnia. J Cereb Blood Flow Metab 2007; 27:414-23. [PMID: 16736039 DOI: 10.1038/sj.jcbfm.9600347] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Opioid binding to the cerebral blood vessels may affect vascular responsiveness and hence confound interpretation of blood oxygen level-dependent (BOLD) responses, which are usually interpreted as neuronal in origin. Opioid binding varies in different brain regions. It is unclear whether opioids alter neurovascular coupling, or whether their effects are purely neuronal. This study used BOLD functional magnetic resonance imaging (FMRI) to investigate the effect of a mu-opioid agonist remifentanil, on cerebrovascular CO(2) reactivity (being one component of neurovascular coupling). Hypercapnic challenges were delivered to human volunteers, while controlling potential opioid-induced respiratory depression. The BOLD signal increase to hypercapnia was compared before and during remifentanil administration. Remifentanil was shown not to have a generalised effect on CO(2) responsiveness in the cerebral vasculature. However, it caused a significant reduction in the positive BOLD response to hypercapnia in the bilateral primary sensorimotor cortices, bilateral extrastriate visual areas, left insula, left caudate nucleus, and left inferior temporal gyrus. We conclude that remifentanil does not modulate cerebrovascular CO(2) reactivity, as we saw no difference in BOLD response to hypercapnia in areas with high opioid receptor densities. We did however see a focal reduction in areas related to motor control and putative task activation, which we conclude to be related to changes in neuronal activity related to the sedative effects of remifentanil. Our method of controlling CO(2) levels effectively mitigated the potential confound of respiratory depression and allowed comparison over a similar range of CO(2) levels. We suggest that similar methodology should be used when investigating other potentially vasoactive compounds with FMRI.
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Affiliation(s)
- Kyle T S Pattinson
- Nuffield Department of Anaesthetics, Oxford University, John Radcliffe Hospital, Oxford, UK.
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39
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Krainik A, Rubin C, Grand S, David O, Baciu M, Jaillard A, Troprès I, Lamalle L, Duffau H, Le Bas JF, Segebarth C, Lehéricy S. L’imagerie par résonance magnétique cérébrale fonctionnelle en pratique clinique. ACTA ACUST UNITED AC 2006; 87:607-17. [PMID: 16788535 DOI: 10.1016/s0221-0363(06)74054-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In the last decade, functional MRI (fMRI) has become one of the most widely used functional imaging technique in neurosciences. However, its clinical applications remain limited. Despite methodological and practical issues, fMRI data has been validated by different techniques (magnetoencephalography, Wada test, electrical and magnetic stimulations, and surgical resections). In neurosurgical practice, fMRI can identify eloquent areas involved in motor and language functions, and may evaluate characteristics of postoperative neurological deficit including its occurrence, clinical presentation and duration. This may help to inform patients and to prepare postoperative care. fMRI may also identify epileptic foci. In neurological practice, fMRI may help to determine prognosis of recovery after stroke, appropriate medication, and rehabilitation. fMRI may help to identify patients at risk of developing Alzheimer disease. Finally, cerebrovascular reactivity imaging is an interesting approach that might provide new radiological insights of vascular function.
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Affiliation(s)
- A Krainik
- Service de Neuroradiologie - Unité IRM, CHU Grenoble.
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Rostrup E, Larsson HBW, Born AP, Knudsen GM, Paulson OB. Changes in BOLD and ADC weighted imaging in acute hypoxia during sea-level and altitude adapted states. Neuroimage 2005; 28:947-55. [PMID: 16095921 DOI: 10.1016/j.neuroimage.2005.06.032] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2005] [Revised: 06/15/2005] [Accepted: 06/28/2005] [Indexed: 10/25/2022] Open
Abstract
Acute normobaric hypoxia as well as longstanding hypobaric hypoxia induce pronounced physiological changes and may eventually lead to impairment of cerebral function. The aim of the present study is to investigate the effect of hypoxia on the cerebral activation response as well as to explore possible structural changes as measured by diffusion weighted imaging. Eleven healthy sea-level residents were studied after 5 weeks of adaptation to high altitude conditions at Chacaltaya, Bolivia (5260 m). The subjects were studied immediately after return to sea-level in hypoxic and normoxic conditions, and the examinations repeated 6 months later after re-adaptation to sea-level conditions. The BOLD response, measured at 1.5 T, was severely reduced during acute hypoxia both in the altitude and sea-level adapted states (50% reduction during an average S(a)O(2) of 75%). On average, the BOLD response magnitude was 23% lower in altitude than sea-level adaptation in the normoxic condition, but in the hypoxic condition, no significant differences were found. A small but statistically significant decrease in the apparent diffusion coefficient (ADC) was seen in some brain regions during acute hypoxia, whereas ADC was slightly elevated in high altitude as compared to sea-level adaptation. It is concluded that hypoxia significantly diminishes the BOLD response, and the mechanisms underlying this finding are discussed. Furthermore, altitude adaptation may influence both the magnitude of the activation-related response, as well as micro-structural features.
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Affiliation(s)
- Egill Rostrup
- Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital Hvidovre, Denmark.
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Rauscher A, Sedlacik J, Barth M, Haacke EM, Reichenbach JR. Nonnvasive assessment of vascular architecture and function during modulated blood oxygenation using susceptibility weighted magnetic resonance imaging. Magn Reson Med 2005; 54:87-95. [PMID: 15968657 DOI: 10.1002/mrm.20520] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Susceptibility weighted imaging (SWI) is a BOLD-sensitive method for visualizing anatomical features such as small cerebral veins in high detail. The purpose of this study was to evaluate high-resolution SWI in combination with a modulation of blood oxygenation by breathing of air, carbogen, and oxygen and to directly visualize the effects of changing blood oxygenation on the magnetic field inside and around venous blood vessels. Signal changes associated with the response to carbogen and oxygen breathing were evaluated in different anatomic regions in healthy volunteers and in two patients with brain tumors. In the magnitude images inhalation of carbogen led to significant signal intensity changes ranging from +4.4 +/- 1.9% to +9.5 +/- 1.4% in gray matter and no significant changes in thalamus, putamen, and white matter. During oxygen breathing mean signal changes were smaller than during carbogen breathing. The method is capable of producing high-resolution functional maps of BOLD response to carbogen and oxygen breathing as well as high-resolution images of venous vasculature. Its sensitivity to changes in blood oxygenation was demonstrated by in vivo visualization of the BOLD effect via phase imaging.
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Affiliation(s)
- Alexander Rauscher
- Institute for Diagnostic and Interventional Radiology, Friedrich Schiller University, Jena, Germany
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Ainslie PN, Ashmead JC, Ide K, Morgan BJ, Poulin MJ. Differential responses to CO2 and sympathetic stimulation in the cerebral and femoral circulations in humans. J Physiol 2005; 566:613-24. [PMID: 15890697 PMCID: PMC1464750 DOI: 10.1113/jphysiol.2005.087320] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The relative importance of CO2 and sympathetic stimulation in the regulation of cerebral and peripheral vasculatures has not been previously studied in humans. We investigated the effect of sympathetic activation, produced by isometric handgrip (HG) exercise, on cerebral and femoral vasculatures during periods of isocapnia and hypercapnia. In 14 healthy males (28.1 +/- 3.7 (mean +/- S.D.) years), we measured flow velocity (VP; transcranial Doppler ultrasound) in the middle cerebral artery during euoxic isocapnia (ISO, +1 mmHg above rest) and two levels of euoxic hypercapnia (HC5, end-tidal P(CO(2)), P(ET,CO2), = +5 mmHg above ISO; HC10, P(ET,CO2) = +10 above ISO). Each P(ET,CO2) level was maintained for 10 min using the dynamic end-tidal forcing technique, during which increases in sympathetic activity were elicited by a 2-min HG at 30% of maximal voluntary contraction. Femoral blood flow (FBF; Doppler ultrasound), muscle sympathetic nerve activity (MSNA; microneurography) and mean arterial pressure (MAP; Portapres) were also measured. Hypercapnia increased VP and FBF by 5.0 and 0.6% mmHg-1, respectively, and MSNA by 20-220%. Isometric HG increased MSNA by 50% and MAP by 20%, with no differences between ISO, HC5 and HC10. During the ISO HG there was an increase in cerebral vascular resistance (CVR; 20 +/- 11%), while VP remained unchanged. During HC5 and HC10 HG, VP increased (13% and 14%, respectively), but CVR was unchanged. In contrast, HG-induced sympathetic stimulation increased femoral vascular resistance (FVR) during ISO, HC5 and HC10 (17-41%), while there was a general decrease in FBF below ISO. The HG-induced increases in MSNA were associated with increases in FVR in all conditions (r = 0.76-0.87), whereas increases in MSNA were associated with increases in CVR only during ISO (r = 0.91). In summary, in the absence of hypercapnia, HG exercise caused cerebral vasoconstriction, myogenically and/or neurally, which was reflected by increases in CVR and a maintained VP. In contrast, HG increased FVR during conditions of ISO, HC5 and HC10. Therefore, the cerebral circulation is more responsive to alterations in PCO2, and less responsive to sympathetic stimulation than the femoral circulation.
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Affiliation(s)
- Philip N Ainslie
- Department of Physiology & Biophysics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
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Abstract
Cerebrovascular reserve reflects the capacity of the brain to maintain adequate blood flow in the face of decreased perfusion pressure. Perfusion imaging, combined with a physiologic or pharmacologic challenge, is a direct method of measuring cerebrovascular reserve. The authors discuss the strengths and drawbacks of each of the methods of cerebrovascular reserve assessment. They review the applications of cerebrovascular reserve testing, particularly in the assessment of stroke risk in the setting of chronic stenosis or occlusion of vessels in the head and neck.
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Affiliation(s)
- Clifford J Eskey
- Division of Neuroradiology, Dartmouth Hitchcock Medical Center, Lebanon, NH 03756, USA.
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Rostrup E, Knudsen GM, Law I, Holm S, Larsson HBW, Paulson OB. The relationship between cerebral blood flow and volume in humans. Neuroimage 2005; 24:1-11. [PMID: 15588591 DOI: 10.1016/j.neuroimage.2004.09.043] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Revised: 06/25/2004] [Accepted: 09/24/2004] [Indexed: 11/28/2022] Open
Abstract
The purpose of this study was to establish the relationship between regional CBF and CBV at normal, resting cerebral metabolic rates. Eleven healthy volunteers were investigated with PET during baseline conditions, and during hyper- and hypocapnia. Values for rCBF and rCBV were obtained using 15O-labelled water and carbon monoxide, respectively. The mean value of rCBF using PET was 62 +/- 18 ml 100 g(-1) min(-1) during baseline conditions, with an average increase of 46% during hypercapnia, and a decrease of 29% during hypocapnia; baseline rCBV was 7.7 ml/100 g, with 27% increase during hypercapnia and no significant decrease during hypocapnia. A regionally uniform exponential relationship was confirmed between PaCO2 and rCBF as well as rCBV. It is shown that the theoretical implication of this is that the rCBV vs. rCBF relationship should be modelled by a power function; however, due to pronounced intersubject variability, the goodness of fit for linear and nonlinear models were not significantly different. The results of the study are applied to a numerical estimation of regional brain deoxy-haemoglobin content. Independently of the choice of model for the rCBV vs. rCBF relationship, a nonlinear deoxy-haemoglobin vs. rCBF relationship was predicted, and the implications for the BOLD response are discussed.
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Affiliation(s)
- Egill Rostrup
- Danish Research Center for Magnetic Resonance, DK-2650, Copenhagen University Hospital, Hvidovre, Denmark
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Ziyeh S, Rick J, Reinhard M, Hetzel A, Mader I, Speck O. Blood oxygen level-dependent MRI of cerebral CO2 reactivity in severe carotid stenosis and occlusion. Stroke 2005; 36:751-6. [PMID: 15705935 DOI: 10.1161/01.str.0000157593.03470.3d] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND AND PURPOSE Impaired cerebrovascular reserve capacity (CVC) is a risk factor for ischemic events in patients with high-grade carotid stenosis and occlusion. In this study, the CVC in response to a CO2 challenge was evaluated with blood oxygen level-dependent (BOLD) MRI and the results compared with those of a transcranial Doppler CO2 tests. METHODS A T2*-weighted single-shot multigradient echo-planar imaging sequence was used to determine cerebral CO2 reactivity. T2* values were calculated for each pixel at rest and during a challenge with 7% CO2, and a reference function was fitted to the T2* time courses. Whole-brain color-coded DeltaT2* parameter maps were calculated and visually evaluated for regional differences. Additionally, a region-of-interest analysis was undertaken. Average values for DeltaT2* normalized to changes in end-tidal PCO2 were calculated. RESULTS Color parameter maps showed areas of decreased BOLD effect within the internal carotid artery territory in 12 of 13 hemispheres with impaired CVC in transcranial Doppler CO2 test. Regional normalized DeltaT2* was highly correlated with changes of middle cerebral artery blood flow velocity in transcranial Doppler CO2 test. Normalized DeltaT2* was significantly reduced in hemispheres with impaired CVC in transcranial Doppler (P<0.0001). CONCLUSIONS BOLD MRI can easily be included in routine MRI exams. The technique is robust and yields diagnostic information concerning the cerebrovascular reserve.
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Affiliation(s)
- Sargon Ziyeh
- Section of Neuroradiology, University Hospital of Freiburg D-79106 Freiburg, Germany.
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van der Zande FHR, Hofman PAM, Backes WH. Mapping hypercapnia-induced cerebrovascular reactivity using BOLD MRI. Neuroradiology 2004; 47:114-20. [PMID: 15616848 DOI: 10.1007/s00234-004-1274-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Revised: 08/08/2004] [Accepted: 08/16/2004] [Indexed: 10/26/2022]
Abstract
Severe carotid artery stenosis or occlusion may put patients at risk for ischaemic stroke. Reduced cerebrovascular reserve capacity is a possible indicator of an imminent ischaemic event and can be determined by assessment of cerebrovascular reactivity to a vasodilative stimulus. However, little is known about the distribution of cerebrovascular reactivity in healthy individuals. In 13 healthy volunteers, dynamic T2* MR images, acquired at alternating inspiratory pCO2 levels, showed a high percentage of signal change in grey matter, with a strong linear correlation with end-tidal pCO2. The mean percentages of signal change for grey and white matter were 5.9 +/- 1.2% and 1.9 +/- 0.5%, respectively. The mean time lag between CO2 stimulus and haemodynamic response was 15 +/- 4 s for grey matter and 180 +/- 12 s for white matter. Parameter mapping revealed a hemispherically symmetrical and homogeneous distribution of cerebrovascular reactivity over the entire grey matter. These findings indicate that it may be feasible to detect exhausted cerebrovascular autoregulation in patients with a compromised cerebral vasculature.
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Affiliation(s)
- F H R van der Zande
- Department of Radiology, Maastricht University Hospital, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands
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Cohen ER, Rostrup E, Sidaros K, Lund TE, Paulson OB, Ugurbil K, Kim SG. Hypercapnic normalization of BOLD fMRI: comparison across field strengths and pulse sequences. Neuroimage 2004; 23:613-24. [PMID: 15488411 DOI: 10.1016/j.neuroimage.2004.06.021] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2004] [Revised: 04/29/2004] [Accepted: 06/18/2004] [Indexed: 11/24/2022] Open
Abstract
The blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal response to neural stimulation is influenced by many factors that are unrelated to the stimulus. These factors are physiological, such as the resting venous cerebral blood volume (CBV(v)) and vessel size, as well as experimental, such as pulse sequence and static magnetic field strength (B(0)). Thus, it is difficult to compare task-induced fMRI signals across subjects, field strengths, and pulse sequences. This problem can be overcome by normalizing the neural activity-induced BOLD fMRI response by a global hypercapnia-induced BOLD signal. To demonstrate the effectiveness of the BOLD normalization approach, gradient-echo BOLD fMRI at 1.5, 4, and 7 T and spin-echo BOLD fMRI at 4 T were performed in human subjects. For neural stimulation, subjects performed sequential finger movements at 2 Hz, while for global stimulation, subjects breathed a 5% CO(2) gas mixture. Under all conditions, voxels containing primarily large veins and those containing primarily active tissue (i.e., capillaries and small veins) showed distinguishable behavior after hypercapnic normalization. This allowed functional activity to be more accurately localized and quantified based on changes in venous blood oxygenation alone. The normalized BOLD signal induced by the motor task was consistent across different magnetic fields and pulse sequences, and corresponded well with cerebral blood flow measurements. Our data suggest that the hypercapnic normalization approach can improve the spatial specificity and interpretation of BOLD signals, allowing comparison of BOLD signals across subjects, field strengths, and pulse sequences. A theoretical framework for this method is provided.
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Affiliation(s)
- Eric R Cohen
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN 15260, USA
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48
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Knudsen GM, Rostrup E, Hasselbalch SG. Quantitative PET for assessment of cerebral blood flow and glucose consumption under varying physiological conditions. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.ics.2004.04.025] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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49
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Ainslie PN, Poulin MJ. Ventilatory, cerebrovascular, and cardiovascular interactions in acute hypoxia: regulation by carbon dioxide. J Appl Physiol (1985) 2004; 97:149-59. [PMID: 15004003 DOI: 10.1152/japplphysiol.01385.2003] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study examined the effect of high, normal, and uncontrolled end-tidal Pco2 (PetCO2) on the ventilatory, peak cerebral blood flow velocity ( V̄p), and mean arterial blood pressure (MAP) responses to acute hypoxia. Nine healthy subjects undertook, in random order, three hypoxic protocols (end-tidal Po2 was held at eight steps between 300 and 45 Torr) in conditions of hypercapnia, isocapnia, or poikilocapnia (PetCO2 +7.5 Torr, +1.0 Torr, or uncontrolled, respectively). Transcranial Doppler ultrasound was used to measure V̄p in the middle cerebral artery. The slopes of the linear regressions of ventilation, V̄p, and MAP with arterial O2 saturation were significantly greater in hypercapnia than in both isocapnia and poikilocapnia ( P < 0.05). Strong, significant correlations were observed between ventilation, V̄p, and MAP with each PetCO2 condition. These data suggest that 1) a high acute hypoxic ventilatory response (AHVR) decreases the acute hypoxic cerebral blood flow responses during poikilocapnia hypoxia, due to hypocapnic-induced cerebral vasoconstriction; and 2) in hypercapnic hypoxia, a high AHVR is associated with a high acute hypoxic cerebral blood flow response, demonstrating a linkage of individual sensitivities of ventilation and cerebral blood flow to the interaction of PetCO2 and hypoxia. In summary, the between-individual variability in AHVR is shown to be firmly linked to the variability in V̄p and MAP responses to hypoxia. Individuals with a high AHVR are found also to have high V̄p and MAP responses to hypoxia.
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Affiliation(s)
- Philip N Ainslie
- Department of Physiology & Biophysics, Faculty of Medicine, Univiversity of Calgary, Calgary Alberta, Canada T2N 4N1
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50
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Brevard ME, Duong TQ, King JA, Ferris CF. Changes in MRI signal intensity during hypercapnic challenge under conscious and anesthetized conditions. Magn Reson Imaging 2004; 21:995-1001. [PMID: 14684202 PMCID: PMC2962949 DOI: 10.1016/s0730-725x(03)00204-2] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Most functional magnetic resonance imaging (fMRI) studies in animals are conducted under anesthesia to minimize motion artifacts. However, methods and techniques have been developed recently for imaging fully conscious rats. Functional MRI studies on conscious animals report enhanced BOLD signal changes as compared to the anesthetized condition. In this study, rats were exposed to different concentrations of carbon dioxide (CO(2)) while conscious and anesthetized to test whether cerebrovascular reactivity may be contributing to these enhanced BOLD signal changes. Hypercapnia produced significantly greater increases in MRI signal intensity in fully conscious animals (6.7-13.3% changes) as when anesthetized with 1% isoflurane (3.2-4.9% changes). In addition, the response to hypercapnia was more immediate in the conscious condition (< 30s) with signal risetimes twice as fast as in the anesthetized state (60s). Both cortical and subcortical brain regions showed a robust, dose- dependent increase in MRI signal intensity with hypercapnic challenge while the animals were conscious but little or no change when anesthetized. Baseline variations in MRI signal were higher while animals were conscious but this was off set by greater signal intensity changes leading to a greater contrast-to-noise ratio, 13.1 in conscious animals, as compared to 8.0 in the anesthetized condition. In summary, cerebral vasculature appears to be more sensitive to hypercapnic challenge in the conscious condition resulting in enhanced T2* MRI signal intensity and the potential for better BOLD signal changes during functional imaging.
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Affiliation(s)
- M E Brevard
- Center for Comparative Neuroimaging, Department of Psychiatry, University of Massachusetts Medical School, Worcester, MA, USA.
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