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Duffin J, Sobczyk O, Crawley A, Poublanc J, Venkatraghavan L, Sam K, Mutch A, Mikulis D, Fisher J. The role of vascular resistance in BOLD responses to progressive hypercapnia. Hum Brain Mapp 2017; 38:5590-5602. [PMID: 28782872 DOI: 10.1002/hbm.23751] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Revised: 07/20/2017] [Accepted: 07/20/2017] [Indexed: 12/22/2022] Open
Abstract
The ability of the cerebral vasculature to regulate vascular diameter, hence resistance and cerebral blood flow (CBF), in response to metabolic demands (neurovascular coupling), and perfusion pressure changes (autoregulation) may be assessed by measuring the CBF response to carbon dioxide (CO2 ). In healthy individuals, the CBF response to a ramp CO2 stimulus from hypocapnia to hypercapnia is assumed sigmoidal or linear. However, other response patterns commonly occur, especially in individuals with cerebrovascular disease, and these remain unexplained. CBF responses to CO2 in a vascular region are determined by the combined effects of the innate vascular responses to CO2 and the local perfusion pressure; the latter ensuing from pressure-flow interactions within the cerebral vascular network. We modeled this situation as two vascular beds perfused in parallel from a fixed resistance source. Our premise is that all vascular beds have a sigmoidal reduction of resistance in response to a progressive rise in CO2 . Surrogate CBF data to test the model was provided by magnetic resonance imaging of blood oxygen level-dependent (BOLD) signals. The model successfully generated all the various BOLD-CO2 response patterns, providing a physiological explanation of CBF distribution as relative differences in the network of vascular bed resistance responses to CO2 . Hum Brain Mapp 38:5590-5602, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- James Duffin
- Department of Physiology, University Health Network, Toronto, Canada.,Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, Canada
| | - Olivia Sobczyk
- Institute of Medical Science, University of Toronto, Toronto, Canada
| | - Adrian Crawley
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab, University Health Network, Toronto, Canada
| | - Julien Poublanc
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab, University Health Network, Toronto, Canada
| | - Lashmi Venkatraghavan
- Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, Canada
| | - Kevin Sam
- Joint Department of Medical Imaging and the Functional Neuroimaging Lab, University Health Network, Toronto, Canada
| | - Alan Mutch
- Department of Anesthesia and Perioperative Medicine, University of Manitoba, Winnipeg, Manitoba, Canada
| | - David Mikulis
- Institute of Medical Science, University of Toronto, Toronto, Canada.,Joint Department of Medical Imaging and the Functional Neuroimaging Lab, University Health Network, Toronto, Canada
| | - Joseph Fisher
- Department of Physiology, University Health Network, Toronto, Canada.,Department of Anaesthesia and Pain Management, University Health Network, University of Toronto, Toronto, Canada.,Institute of Medical Science, University of Toronto, Toronto, Canada
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Lajoie I, Nugent S, Debacker C, Dyson K, Tancredi FB, Badhwar A, Belleville S, Deschaintre Y, Bellec P, Doyon J, Bocti C, Gauthier S, Arnold D, Kergoat MJ, Chertkow H, Monchi O, Hoge RD. Application of calibrated fMRI in Alzheimer's disease. NEUROIMAGE-CLINICAL 2017; 15:348-358. [PMID: 28560160 PMCID: PMC5443910 DOI: 10.1016/j.nicl.2017.05.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Revised: 04/26/2017] [Accepted: 05/15/2017] [Indexed: 02/07/2023]
Abstract
Calibrated fMRI based on arterial spin-labeling (ASL) and blood oxygen-dependent contrast (BOLD), combined with periods of hypercapnia and hyperoxia, can provide information on cerebrovascular reactivity (CVR), resting blood flow (CBF), oxygen extraction fraction (OEF), and resting oxidative metabolism (CMRO2). Vascular and metabolic integrity are believed to be affected in Alzheimer's disease (AD), thus, the use of calibrated fMRI in AD may help understand the disease and monitor therapeutic responses in future clinical trials. In the present work, we applied a calibrated fMRI approach referred to as Quantitative O2 (QUO2) in a cohort of probable AD dementia and age-matched control participants. The resulting CBF, OEF and CMRO2 values fell within the range from previous studies using positron emission tomography (PET) with 15O labeling. Moreover, the typical parietotemporal pattern of hypoperfusion and hypometabolism in AD was observed, especially in the precuneus, a particularly vulnerable region. We detected no deficit in frontal CBF, nor in whole grey matter CVR, which supports the hypothesis that the effects observed were associated specifically with AD rather than generalized vascular disease. Some key pitfalls affecting both ASL and BOLD methods were encountered, such as prolonged arterial transit times (particularly in the occipital lobe), the presence of susceptibility artifacts obscuring medial temporal regions, and the challenges associated with the hypercapnic manipulation in AD patients and elderly participants. The present results are encouraging and demonstrate the promise of calibrated fMRI measurements as potential biomarkers in AD. Although CMRO2 can be imaged with 15O PET, the QUO2 method uses more widely available imaging infrastructure, avoids exposure to ionizing radiation, and integrates with other MRI-based measures of brain structure and function.
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Affiliation(s)
- Isabelle Lajoie
- Département de Pharmacologie et physiologie, Université de Montréal, Montreal, QC, Canada; Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Montreal Neurological Institute, Montreal, QC, Canada.
| | - Scott Nugent
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Montreal Neurological Institute, Montreal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
| | - Clément Debacker
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Montreal Neurological Institute, Montreal, QC, Canada; Department of Psychiatry, McGill University, Montreal, QC, Canada
| | - Kenneth Dyson
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Montreal Neurological Institute, Montreal, QC, Canada; Department of Physiology, McGill University, Montreal, QC, Canada
| | - Felipe B Tancredi
- Departamento de Radiologia, Centro de Pesquisa em Imagem, Hospital Israelita Albert Einstein, São Palo, SP, Brazil
| | - AmanPreet Badhwar
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Department of Computer Science and Operations Research, Université de Montréal, Montreal, QC, Canada
| | - Sylvie Belleville
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Département de Psychologie, Université de Montréal, Montreal, QC, Canada
| | - Yan Deschaintre
- Département de Neurosciences, Université de Montréal, Montreal, QC, Canada; Service de neurologie, Département de Médecine, CHUM Notre-Dame, Montréal, QC, Canada
| | - Pierre Bellec
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Department of Computer Science and Operations Research, Université de Montréal, Montreal, QC, Canada
| | - Julien Doyon
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Département de Psychologie, Université de Montréal, Montreal, QC, Canada
| | - Christian Bocti
- Division de Neurologie, Faculté de Médecine et des Sciences de la Santé & Research Centre on Aging, Université de Sherbrooke, Sherbrooke, QC, Canada
| | - Serge Gauthier
- McGill Center for Studies in Aging, Douglas Mental Health Research Institute, Montreal, QC, Canada
| | - Douglas Arnold
- Montreal Neurological Institute, Montreal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
| | - Marie-Jeanne Kergoat
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Département de Médecine, Université de Montréal, Montreal, QC, Canada
| | - Howard Chertkow
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada; Department of Medicine, Sir Mortimer B. Davis-Jewish General Hospital, McGill University, Montreal, QC, Canada
| | - Oury Monchi
- Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada; McGill Center for Studies in Aging, Douglas Mental Health Research Institute, Montreal, QC, Canada; Department of Clinical Neurosciences and Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Richard D Hoge
- Département de Pharmacologie et physiologie, Université de Montréal, Montreal, QC, Canada; Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, QC, Canada; Montreal Neurological Institute, Montreal, QC, Canada; Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
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Sheng M, Liu P, Mao D, Ge Y, Lu H. The impact of hyperoxia on brain activity: A resting-state and task-evoked electroencephalography (EEG) study. PLoS One 2017; 12:e0176610. [PMID: 28464001 PMCID: PMC5412995 DOI: 10.1371/journal.pone.0176610] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 04/13/2017] [Indexed: 12/17/2022] Open
Abstract
A better understanding of the effect of oxygen on brain electrophysiological activity may provide a more mechanistic insight into clinical studies that use oxygen treatment in pathological conditions, as well as in studies that use oxygen to calibrate functional magnetic resonance imaging (fMRI) signals. This study applied electroencephalography (EEG) in healthy subjects and investigated how high a concentration of oxygen in inhaled air (i.e., normobaric hyperoxia) alters brain activity under resting-state and task-evoked conditions. Study 1 investigated its impact on resting EEG and revealed that hyperoxia suppressed α (8-13Hz) and β (14-35Hz) band power (by 15.6±2.3% and 14.1±3.1%, respectively), but did not change the δ (1-3Hz), θ (4-7Hz), and γ (36-75Hz) bands. Sham control experiments did not result in such changes. Study 2 reproduced these findings, and, furthermore, examined the effect of hyperoxia on visual stimulation event-related potentials (ERP). It was found that the main peaks of visual ERP, specifically N1 and P2, were both delayed during hyperoxia compared to normoxia (P = 0.04 and 0.02, respectively). In contrast, the amplitude of the peaks did not show a change. Our results suggest that hyperoxia has a pronounced effect on brain neural activity, for both resting-state and task-evoked potentials.
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Affiliation(s)
- Min Sheng
- Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Peiying Liu
- Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Deng Mao
- Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Yulin Ge
- Department of Radiology, New York University Langone Medical Center, New York, New York, United States of America
| | - Hanzhang Lu
- Advanced Imaging Research Center, The University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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54
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Investigation of the confounding effects of vasculature and metabolism on computational anatomy studies. Neuroimage 2017; 149:233-243. [DOI: 10.1016/j.neuroimage.2017.01.025] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 01/10/2017] [Accepted: 01/11/2017] [Indexed: 01/21/2023] Open
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Lajoie I, Tancredi FB, Hoge RD. The impact of inspired oxygen levels on calibrated fMRI measurements of M, OEF and resting CMRO2 using combined hypercapnia and hyperoxia. PLoS One 2017; 12:e0174932. [PMID: 28362834 PMCID: PMC5376305 DOI: 10.1371/journal.pone.0174932] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 03/17/2017] [Indexed: 12/04/2022] Open
Abstract
Recent calibrated fMRI techniques using combined hypercapnia and hyperoxia allow the mapping of resting cerebral metabolic rate of oxygen (CMRO2) in absolute units, oxygen extraction fraction (OEF) and calibration parameter M (maximum BOLD). The adoption of such technique necessitates knowledge about the precision and accuracy of the model-derived parameters. One of the factors that may impact the precision and accuracy is the level of oxygen provided during periods of hyperoxia (HO). A high level of oxygen may bring the BOLD responses closer to the maximum M value, and hence reduce the error associated with the M interpolation. However, an increased concentration of paramagnetic oxygen in the inhaled air may result in a larger susceptibility area around the frontal sinuses and nasal cavity. Additionally, a higher O2 level may generate a larger arterial blood T1 shortening, which require a bigger cerebral blood flow (CBF) T1 correction. To evaluate the impact of inspired oxygen levels on M, OEF and CMRO2 estimates, a cohort of six healthy adults underwent two different protocols: one where 60% of O2 was administered during HO (low HO or LHO) and one where 100% O2 was administered (high HO or HHO). The QUantitative O2 (QUO2) MRI approach was employed, where CBF and R2* are simultaneously acquired during periods of hypercapnia (HC) and hyperoxia, using a clinical 3 T scanner. Scan sessions were repeated to assess repeatability of results at the different O2 levels. Our T1 values during periods of hyperoxia were estimated based on an empirical ex-vivo relationship between T1 and the arterial partial pressure of O2. As expected, our T1 estimates revealed a larger T1 shortening in arterial blood when administering 100% O2 relative to 60% O2 (T1LHO = 1.56±0.01 sec vs. T1HHO = 1.47±0.01 sec, P < 4*10−13). In regard to the susceptibility artifacts, the patterns and number of affected voxels were comparable irrespective of the O2 concentration. Finally, the model-derived estimates were consistent regardless of the HO levels, indicating that the different effects are adequately accounted for within the model.
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Affiliation(s)
- Isabelle Lajoie
- Département de physiologie moléculaire et intégrative, Institut de génie biomédical, Université de Montréal, Montreal, Quebec, Canada
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- * E-mail:
| | - Felipe B. Tancredi
- Departamento de Radiologia, Centro de Pesquisa em Imagem, Hospital Israelita Albert Einstein, São Palo, SP, Brazil
| | - Richard D. Hoge
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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56
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Helmerhorst HJF, de Wilde RBP, Lee DH, Palmen M, Jansen JRC, van Westerloo DJ, de Jonge E. Hemodynamic effects of short-term hyperoxia after coronary artery bypass grafting. Ann Intensive Care 2017; 7:20. [PMID: 28233196 PMCID: PMC5323416 DOI: 10.1186/s13613-017-0246-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Accepted: 02/14/2017] [Indexed: 01/11/2023] Open
Abstract
Background Although oxygen is generally administered in a liberal manner in the perioperative setting, the effects of oxygen administration on dynamic cardiovascular parameters, filling status and cerebral perfusion have not been fully unraveled. Our aim was to study the acute hemodynamic and microcirculatory changes before, during and after arterial hyperoxia in mechanically ventilated patients after coronary artery bypass grafting (CABG) surgery. Methods This was a single-center physiological study in a tertiary care ICU in the Netherlands. Twenty-two patients scheduled for ICU admission after elective CABG were enrolled in the study between September 2014 and September 2015. In the ICU, patients were exposed to a fraction of inspired oxygen (FiO2) of 90% allowing a 15-min wash-in period. Various hemodynamic parameters were measured using direct pressure signals and continuous arterial waveform analysis at three sequential time points: before, during and after hyperoxia. Results During a 15-min exposure to a fraction of inspired oxygen (FiO2) of 90%, the partial pressure of arterial oxygen (PaO2) and arterial oxygen saturation (SaO2) were significantly higher. The systemic resistance increased (P < 0.0001), without altering the heart rate. Stroke volume variation and pulse pressure variation decreased slightly. The cardiac output did not significantly decrease (P = 0.08). Mean systemic filling pressure and arterial critical closing pressure increased (P < 0.01), whereas the percentage of perfused microcirculatory vessels decreased (P < 0.01). Other microcirculatory parameters and cerebral blood flow velocity showed only slight changes. Conclusions We found that short-term hyperoxia affects hemodynamics in ICU patients after CABG. This was translated in several changes in central circulatory variables, but had only slight effects on cardiac output, cerebral blood flow and the microcirculation. Clinical trial registration Netherlands Trial Register: NTR5064
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Affiliation(s)
- Hendrik J F Helmerhorst
- Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands. .,Department of Anesthesiology, Leiden University Medical Center, Leiden, The Netherlands. .,Laboratory of Experimental Intensive Care and Anesthesiology, Academic Medical Center, Amsterdam, The Netherlands.
| | - Rob B P de Wilde
- Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands
| | - Dae Hyun Lee
- Department of Nephrology, Einthoven Laboratory for Vascular Medicine, Leiden University Medical Center, Leiden, The Netherlands
| | - Meindert Palmen
- Department of Cardiothoracic Surgery, Leiden University Medical Center, Leiden, The Netherlands
| | - Jos R C Jansen
- Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands
| | - David J van Westerloo
- Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands
| | - Evert de Jonge
- Department of Intensive Care Medicine, Leiden University Medical Center, Post Box 9600, Leiden, 2300 RC, The Netherlands
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Dani KA, Moreton FC, Santosh C, Lopez R, Brennan D, Schwarzbauer C, Goutcher C, O'Hare K, Macrae IM, Muir KW. Oxygen challenge magnetic resonance imaging in healthy human volunteers. J Cereb Blood Flow Metab 2017; 37:366-376. [PMID: 26787107 PMCID: PMC5363753 DOI: 10.1177/0271678x15627827] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 11/12/2015] [Accepted: 11/16/2015] [Indexed: 11/15/2022]
Abstract
Oxygen challenge imaging involves transient hyperoxia applied during deoxyhaemoglobin sensitive (T2*-weighted) magnetic resonance imaging and has the potential to detect changes in brain oxygen extraction. In order to develop optimal practical protocols for oxygen challenge imaging, we investigated the influence of oxygen concentration, cerebral blood flow change, pattern of oxygen administration and field strength on T2*-weighted signal. Eight healthy volunteers underwent multi-parametric magnetic resonance imaging including oxygen challenge imaging and arterial spin labelling using two oxygen concentrations (target FiO2 of 100 and 60%) administered consecutively (two-stage challenge) at both 1.5T and 3T. There was a greater signal increase in grey matter compared to white matter during oxygen challenge (p < 0.002 at 3T, P < 0.0001 at 1.5T) and at FiO2 = 100% compared to FiO2 = 60% in grey matter at both field strengths (p < 0.02) and in white matter at 3T only (p = 0.0314). Differences in the magnitude of signal change between 1.5T and 3T did not reach statistical significance. Reduction of T2*-weighted signal to below baseline, after hyperoxia withdrawal, confounded interpretation of two-stage oxygen challenge imaging. Reductions in cerebral blood flow did not obscure the T2*-weighted signal increases. In conclusion, the optimal protocol for further study should utilise target FiO2 = 100% during a single oxygen challenge. Imaging at both 1.5T and 3T is clinically feasible.
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Affiliation(s)
- Krishna A Dani
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Fiona C Moreton
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Celestine Santosh
- Department of Neuroradiology, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Rosario Lopez
- Department of Clinical Physics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - David Brennan
- Department of Clinical Physics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Christian Schwarzbauer
- University of Applied Sciences Munich, School of Applied Sciences and Mechatronics, München
| | - Colin Goutcher
- Department of Anaesthetics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Kevin O'Hare
- Department of Anaesthetics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - I Mhairi Macrae
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow
| | - Keith W Muir
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
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Effect of sensor location on regional cerebral oxygen saturation measured by INVOS 5100 in on-pump cardiac surgery. J Anesth 2016; 31:178-184. [DOI: 10.1007/s00540-016-2287-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 11/19/2016] [Indexed: 11/27/2022]
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Donahue MJ, Strother MK, Lindsey KP, Hocke LM, Tong Y, Frederick BD. Time delay processing of hypercapnic fMRI allows quantitative parameterization of cerebrovascular reactivity and blood flow delays. J Cereb Blood Flow Metab 2016; 36:1767-1779. [PMID: 26661192 PMCID: PMC5076782 DOI: 10.1177/0271678x15608643] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 07/29/2015] [Indexed: 11/17/2022]
Abstract
Blood oxygenation level-dependent fMRI contrast depends on the volume and oxygenation of blood flowing through the circulatory system. The effects on image intensity depend temporally on the arrival of blood within a voxel, and signal can be monitored during the time course of such blood flow. It has been previously shown that the passage of global endogenous variations in blood volume and oxygenation can be tracked as blood passes through the brain by determining the strength and peak time lag of their cross-correlation with blood oxygenation level-dependent data. By manipulating blood composition using transient hypercarbia and hyperoxia, we can induce much larger oxygenation and volume changes in the blood oxygenation level-dependent signal than result from natural endogenous fluctuations. This technique was used to examine cerebrovascular parameters in healthy subjects (n = 8) and subjects with intracranial stenosis (n = 22), with a subgroup of intracranial stenosis subjects scanned before and after surgical revascularization (n = 6). The halfwidth of cross-correlation lag times in the brain was larger in IC stenosis subjects (21.21 ± 14.22 s) than in healthy control subjects (8.03 ± 3.67), p < 0.001, and was subsequently reduced in regions that co-localized with surgical revascularization. These data show that blood circulatory timing can be measured robustly and longitudinally throughout the brain using simple respiratory challenges.
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Affiliation(s)
- Manus J Donahue
- Department of Radiology, Vanderbilt Medical Center, Nashville, TN, USA Department of Neurology, Vanderbilt Medical Center, Nashville, TN, USA Department of Psychiatry, Vanderbilt Medical Center, Nashville, TN, USA Department of Physics and Astronomy, Vanderbilt University, Nashville, TN, USA
| | - Megan K Strother
- Department of Radiology, Vanderbilt Medical Center, Nashville, TN, USA
| | - Kimberly P Lindsey
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Lia M Hocke
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Bioengineering, Tufts University, Medford, MA, USA
| | - Yunjie Tong
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Blaise deB Frederick
- Brain Imaging Center, McLean Hospital, Belmont, MA, USA Department of Psychiatry, Harvard Medical School, Boston, MA, USA
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Lajoie I, Tancredi FB, Hoge RD. Regional Reproducibility of BOLD Calibration Parameter M, OEF and Resting-State CMRO2 Measurements with QUO2 MRI. PLoS One 2016; 11:e0163071. [PMID: 27649493 PMCID: PMC5029886 DOI: 10.1371/journal.pone.0163071] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 09/01/2016] [Indexed: 11/18/2022] Open
Abstract
The current generation of calibrated MRI methods goes beyond simple localization of task-related responses to allow the mapping of resting-state cerebral metabolic rate of oxygen (CMRO2) in micromolar units and estimation of oxygen extraction fraction (OEF). Prior to the adoption of such techniques in neuroscience research applications, knowledge about the precision and accuracy of absolute estimates of CMRO2 and OEF is crucial and remains unexplored to this day. In this study, we addressed the question of methodological precision by assessing the regional inter-subject variance and intra-subject reproducibility of the BOLD calibration parameter M, OEF, O2 delivery and absolute CMRO2 estimates derived from a state-of-the-art calibrated BOLD technique, the QUantitative O2 (QUO2) approach. We acquired simultaneous measurements of CBF and R2* at rest and during periods of hypercapnia (HC) and hyperoxia (HO) on two separate scan sessions within 24 hours using a clinical 3 T MRI scanner. Maps of M, OEF, oxygen delivery and CMRO2, were estimated from the measured end-tidal O2, CBF0, CBFHC/HO and R2*HC/HO. Variability was assessed by computing the between-subject coefficients of variation (bwCV) and within-subject CV (wsCV) in seven ROIs. All tests GM-averaged values of CBF0, M, OEF, O2 delivery and CMRO2 were: 49.5 ± 6.4 mL/100 g/min, 4.69 ± 0.91%, 0.37 ± 0.06, 377 ± 51 μmol/100 g/min and 143 ± 34 μmol/100 g/min respectively. The variability of parameter estimates was found to be the lowest when averaged throughout all GM, with general trends toward higher CVs when averaged over smaller regions. Among the MRI measurements, the most reproducible across scans was R2*0 (wsCVGM = 0.33%) along with CBF0 (wsCVGM = 3.88%) and R2*HC (wsCVGM = 6.7%). CBFHC and R2*HO were found to have a higher intra-subject variability (wsCVGM = 22.4% and wsCVGM = 16% respectively), which is likely due to propagation of random measurement errors, especially for CBFHC due to the low contrast-to-noise ratio intrinsic to ASL. Reproducibility of the QUO2 derived estimates were computed, yielding a GM intra-subject reproducibility of 3.87% for O2 delivery, 16.8% for the M value, 13.6% for OEF and 15.2% for CMRO2. Although these results focus on the precision of the QUO2 method, rather than the accuracy, the information will be useful for calculation of statistical power in future validation studies and ultimately for research applications of the method. The higher test-retest variability for the more extensively modeled parameters (M, OEF, and CMRO2) highlights the need for further improvement of acquisition methods to reduce noise levels.
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Affiliation(s)
- Isabelle Lajoie
- Département de physiologie moléculaire et intégrative, Institut de génie biomédical, Université de Montréal, Montreal, Quebec, Canada
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
- * E-mail:
| | - Felipe B. Tancredi
- Departamento de Radiologia, Centro de Pesquisa em Imagem, Hospital Israelita Albert Einstein, São Palo, SP, Brazil
| | - Richard D. Hoge
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
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Rodgers ZB, Detre JA, Wehrli FW. MRI-based methods for quantification of the cerebral metabolic rate of oxygen. J Cereb Blood Flow Metab 2016; 36:1165-85. [PMID: 27089912 PMCID: PMC4929705 DOI: 10.1177/0271678x16643090] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 02/22/2016] [Indexed: 11/16/2022]
Abstract
The brain depends almost entirely on oxidative metabolism to meet its significant energy requirements. As such, the cerebral metabolic rate of oxygen (CMRO2) represents a key measure of brain function. Quantification of CMRO2 has helped elucidate brain functional physiology and holds potential as a clinical tool for evaluating neurological disorders including stroke, brain tumors, Alzheimer's disease, and obstructive sleep apnea. In recent years, a variety of magnetic resonance imaging (MRI)-based CMRO2 quantification methods have emerged. Unlike positron emission tomography - the current "gold standard" for measurement and mapping of CMRO2 - MRI is non-invasive, relatively inexpensive, and ubiquitously available in modern medical centers. All MRI-based CMRO2 methods are based on modeling the effect of paramagnetic deoxyhemoglobin on the magnetic resonance signal. The various methods can be classified in terms of the MRI contrast mechanism used to quantify CMRO2: T2*, T2', T2, or magnetic susceptibility. This review article provides an overview of MRI-based CMRO2 quantification techniques. After a brief historical discussion motivating the need for improved CMRO2 methodology, current state-of-the-art MRI-based methods are critically appraised in terms of their respective tradeoffs between spatial resolution, temporal resolution, and robustness, all of critical importance given the spatially heterogeneous and temporally dynamic nature of brain energy requirements.
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Affiliation(s)
- Zachary B Rodgers
- University of Pennsylvania Medical Center, Philadelphia, PA, USA Laboratory for Structural, Physiologic, and Functional Imaging, Department of Radiology, Philadelphia, PA, USA
| | - John A Detre
- University of Pennsylvania Medical Center, Philadelphia, PA, USA Center for Functional Neuroimaging, Department of Neurology, Philadelphia, PA, USA
| | - Felix W Wehrli
- University of Pennsylvania Medical Center, Philadelphia, PA, USA
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Fisher JA. The CO2 stimulus for cerebrovascular reactivity: Fixing inspired concentrations vs. targeting end-tidal partial pressures. J Cereb Blood Flow Metab 2016; 36:1004-11. [PMID: 27000209 PMCID: PMC4908627 DOI: 10.1177/0271678x16639326] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 02/20/2016] [Indexed: 11/15/2022]
Abstract
Cerebrovascular reactivity (CVR) studies have elucidated the physiology and pathophysiology of cerebral blood flow regulation. A non-invasive, high spatial resolution approach uses carbon dioxide (CO2) as the vasoactive stimulus and magnetic resonance techniques to estimate the cerebral blood flow response. CVR is assessed as the ratio response change to stimulus change. Precise control of the stimulus is sought to minimize CVR variability between tests, and show functional differences. Computerized methods targeting end-tidal CO2 partial pressures are precise, but expensive. Simpler, improvised methods that fix the inspired CO2 concentrations have been recommended as less expensive, and so more widely accessible. However, these methods have drawbacks that have not been previously presented by those that advocate their use, or those that employ them in their studies. As one of the developers of a computerized method, I provide my perspective on the trade-offs between these two methods. The main concern is that declaring the precision of fixed inspired concentration of CO2 is misleading: it does not, as implied, translate to precise control of the actual vasoactive stimulus - the arterial partial pressure of CO2 The inherent test-to-test, and therefore subject-to-subject variability, precludes clinical application of findings. Moreover, improvised methods imply widespread duplication of development, assembly time and costs, yet lack uniformity and quality control. A tabular comparison between approaches is provided.
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Affiliation(s)
- Joseph A Fisher
- Department of Anesthesiology University Health Network, and Department of Physiology, University of Toronto, Toronto, Canada
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64
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Respiratory challenge MRI: Practical aspects. NEUROIMAGE-CLINICAL 2016; 11:667-677. [PMID: 27330967 PMCID: PMC4901170 DOI: 10.1016/j.nicl.2016.05.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2016] [Revised: 04/11/2016] [Accepted: 05/03/2016] [Indexed: 11/24/2022]
Abstract
Respiratory challenge MRI is the modification of arterial oxygen (PaO2) and/or carbon dioxide (PaCO2) concentration to induce a change in cerebral function or metabolism which is then measured by MRI. Alterations in arterial gas concentrations can lead to profound changes in cerebral haemodynamics which can be studied using a variety of MRI sequences. Whilst such experiments may provide a wealth of information, conducting them can be complex and challenging. In this paper we review the rationale for respiratory challenge MRI including the effects of oxygen and carbon dioxide on the cerebral circulation. We also discuss the planning, equipment, monitoring and techniques that have been used to undertake these experiments. We finally propose some recommendations in this evolving area for conducting these experiments to enhance data quality and comparison between techniques. Oxygen and carbon dioxide affect cerebral blood flow and metabolism. This can be imaged with various MRI sequences. The practicalities of these techniques are reviewed. Examples of how this has been used to understand disease mechanisms.
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Borzage MT, Bush AM, Choi S, Nederveen AJ, Václavů L, Coates TD, Wood JC. Predictors of cerebral blood flow in patients with and without anemia. J Appl Physiol (1985) 2016; 120:976-81. [PMID: 26796758 PMCID: PMC4835904 DOI: 10.1152/japplphysiol.00994.2015] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 01/19/2016] [Indexed: 11/22/2022] Open
Abstract
Sickle cell disease (SCD) is the most common cause of stroke in childhood and results primarily from a mismatch of cerebral oxygen supply and demand rather than arterial obstruction. However, resting cerebral blood flow (CBF) has not been examined in the general African American population, in whom obesity, hypertension, cerebrovascular disease, and diminished cerebrovascular reserve capacity are common. To better understand the underlying physiological substrate upon which SCD is superimposed, we measured CBF in 32 young (age 28 ± 10 yr), asymptomatic African American subjects with and without sickle cell trait (n= 14). To characterize the effects of chronic anemia, in isolation of sickle hemoglobin we also studied a cohort of 13 subjects with thalassemia major (n= 10), dyserythropoetic anemia (n= 1), or spherocytosis (n= 2). Blood was analyzed for complete blood count, hemoglobin electrophoresis, cell free hemoglobin, and lactate dehydrogenase. Multivariate regression analysis showed that oxygen content was the strongest predictor of CBF (r(2)= 0.33,P< 0.001). CBF declined rapidly in the second and third decades of life, but this drop was explained by reductions in cerebral gray matter. However, age effects persisted after correction for brain composition, possibly representing microvascular impairment. CBF was independent of viscosity, hemoglobin S%, and body mass index. Hyperoxia resulted in reduced CBF by 12.6% (P= 0.0002), and CBF changes were proportional to baseline oxygen content (r(2)= 0.16,P= 0.02). These data suggest that these hemoglobin subtypes do not alter the normal CBF regulation of the balance of oxygen supply and demand.
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Affiliation(s)
- Matthew T Borzage
- Division of Neonatology and Radiology, Children's Hospital Los Angeles, Los Angeles, California
| | - Adam M Bush
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California
| | - Soyoung Choi
- Neuroscience Graduate Program, University of Southern California, Los Angeles, California
| | - Aart J Nederveen
- Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Lena Václavů
- Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Thomas D Coates
- Division of Hematology, Children's Hospital Los Angeles, Los Angeles, California; and
| | - John C Wood
- Division of Cardiology and Radiology, Children's Hospital Los Angeles, Los Angeles, California
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66
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Taher A, Pilehvari Z, Poorolajal J, Aghajanloo M. Effects of Normobaric Hyperoxia in Traumatic Brain Injury: A Randomized Controlled Clinical Trial. Trauma Mon 2016; 21:e26772. [PMID: 27218057 PMCID: PMC4869427 DOI: 10.5812/traumamon.26772] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 11/21/2015] [Indexed: 01/22/2023] Open
Abstract
Background Traumatic brain injury (TBI) is one of the important causes of morbidity and mortality throughout the world, especially in young people. In recent years normobaric hyperoxia has become an important and useful step for recovery and improvement of outcome in TBI. Objectives The purpose of this study was to evaluate the effects of normobaric hyperoxia on clinical neurological outcomes of patients with severe traumatic brain injuries. We used the Glasgow outcome scale (GOS), barthel index, and modified rankin scale (mRS) to measure the outcomes of patients with TBI. Patients and Methods Sixty-eight consecutive patients with severe TBI (mean Glasgow coma scale [GCS] score: 7.4) who met the inclusion criteria were entered in this randomized controlled clinical trial. The patients were randomized into two groups, as follows: 1) experimental: received 80% oxygen via mechanical ventilator in the first 6 hours of admission, 2) control: received 50% oxygen by mechanical ventilator in the first 6 hours of admission and then standard medical care. We measured the GOS, Barthel Index, and mRS at the time of discharge from hospital and reassessed these measurements at the 6-month follow-up after injury. Results According to our study, there were no significant sex or age differences between the two groups (P = 0.595 and 0.074). The number of days in the intensive care unit (ICU) in the control group and experimental group were 11.4 and 9.4 days, respectively (P = 0.28), while the numbers of days of general ward admission were 13.9 and 11.4 days (P = 0.137) respectively. The status of GOS at time of discharge were severe = 13 and 10, moderate = 16 and 19, and low = 5 and 5 in the control and experimental groups, respectively (P = 0.723); 6 months after injury, the scores were as follows: moderate = 16 and 9, low = 15 and 25, and severe = 3 and 0 (P = 0.024). The Barthel index scores in the control and experimental groups were 59.7 and 63.9 at time of discharge (P = 0.369) and 82.7 and 91.3 at 6 months after injury (P = 0.018), respectively. The mRS results were 2.6 and 2.3 at time of discharge (P = 0.320) and 1.6 and 0.7 at 6 months after injury (P = 0.006) for the control and experimental groups, respectively. Conclusions According to the results of this study, oxygen therapy by mechanical ventilator in the first 6 hours after injury in patients with severe TBI can improve the final GOS, Barthel index, and mRS scores. It could also improve long-term outcomes and enhance rehabilitation and the quality of life.
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Affiliation(s)
- Abbas Taher
- Department of Anesthesiology and Critical Care, Hamadan University of Medical Sciences, Hamadan, IR Iran
| | - Zahra Pilehvari
- Department of Anesthesiology and Critical Care, Hamadan University of Medical Sciences, Hamadan, IR Iran
- Corresponding author: Zahra Pilehvari, Department of Anesthesiology and Critical Care, Besat Hospital, Hamadan University of Medical Sciences, Hamadan, IR Iran. Tel: +98-9123878776, Fax: +98-2177053308, E-mail:
| | - Jalal Poorolajal
- Department of Epidemiology, Modeling of Noncommunicable Diseases Research Center, School of Public Health, Hamadan University of Medical Sciences, Hamadan, IR Iran
| | - Mashhood Aghajanloo
- Department of Neurosurgery, Hamadan University of Medical Sciences, Hamadan, IR Iran
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67
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Merola A, Murphy K, Stone AJ, Germuska MA, Griffeth VEM, Blockley NP, Buxton RB, Wise RG. Measurement of oxygen extraction fraction (OEF): An optimized BOLD signal model for use with hypercapnic and hyperoxic calibration. Neuroimage 2016; 129:159-174. [PMID: 26801605 DOI: 10.1016/j.neuroimage.2016.01.021] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 01/06/2016] [Accepted: 01/09/2016] [Indexed: 11/24/2022] Open
Abstract
Several techniques have been proposed to estimate relative changes in cerebral metabolic rate of oxygen consumption (CMRO2) by exploiting combined BOLD fMRI and cerebral blood flow data in conjunction with hypercapnic or hyperoxic respiratory challenges. More recently, methods based on respiratory challenges that include both hypercapnia and hyperoxia have been developed to assess absolute CMRO2, an important parameter for understanding brain energetics. In this paper, we empirically optimize a previously presented "original calibration model" relating BOLD and blood flow signals specifically for the estimation of oxygen extraction fraction (OEF) and absolute CMRO2. To do so, we have created a set of synthetic BOLD signals using a detailed BOLD signal model to reproduce experiments incorporating hypercapnic and hyperoxic respiratory challenges at 3T. A wide range of physiological conditions was simulated by varying input parameter values (baseline cerebral blood volume (CBV0), baseline cerebral blood flow (CBF0), baseline oxygen extraction fraction (OEF0) and hematocrit (Hct)). From the optimization of the calibration model for estimation of OEF and practical considerations of hypercapnic and hyperoxic respiratory challenges, a new "simplified calibration model" is established which reduces the complexity of the original calibration model by substituting the standard parameters α and β with a single parameter θ. The optimal value of θ is determined (θ=0.06) across a range of experimental respiratory challenges. The simplified calibration model gives estimates of OEF0 and absolute CMRO2 closer to the true values used to simulate the experimental data compared to those estimated using the original model incorporating literature values of α and β. Finally, an error propagation analysis demonstrates the susceptibility of the original and simplified calibration models to measurement errors and potential violations in the underlying assumptions of isometabolism. We conclude that using the simplified calibration model results in a reduced bias in OEF0 estimates across a wide range of potential respiratory challenge experimental designs.
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Affiliation(s)
- Alberto Merola
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK
| | - Kevin Murphy
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK
| | - Alan J Stone
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK
| | - Michael A Germuska
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK
| | - Valerie E M Griffeth
- Department of Bioengineering and Medical Scientist Training Program, University of California San Diego, La Jolla, CA, United States
| | - Nicholas P Blockley
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK; Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, United States
| | - Richard B Buxton
- Center for Functional Magnetic Resonance Imaging, Department of Radiology, University of California San Diego, La Jolla, CA, United States; Kavli Institute for Brain and Mind, University of California San Diego, La Jolla, CA, United States
| | - Richard G Wise
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Cardiff, UK.
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Abstract
Oxygen plays a fundamental role in functional magnetic resonance imaging (FMRI). Blood oxygenation level-dependent (BOLD) imaging is the foundation stone of all FMRI and is still the essential workhorse of the vast majority of FMRI procedures. Hemoglobin may provide the magnetic properties that allow the technique to work, but it is oxygen that allows the contrast to effectively be switched on or off, and it is oxygen that we are interested in tracking in order to observe the oxygen metabolism changes. In general the changes in venous oxygen saturation are observed in order to infer changes in the correlated mechanisms, which can include changes in cerebral blood flow, metabolism, and the fraction of inspired oxygen. By independently manipulating the fraction of inspired oxygen it is possible to alter the amount of dissolved oxygen in the plasma, the venous saturation, or even the blood flow. The effects that these changes have on the observed MRI signal can be either a help or a hindrance depending on how well the changes induced are understood. The administration of supplemental inspired oxygen is in a unique position to provide a flexible, noninvasive, inexpensive, patient-friendly addition to the MRI toolkit to enable investigations to look beyond statistics and regions of interest, and actually produce calibrated, targeted measurements of blood flow, metabolism or pathology.
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Affiliation(s)
- Daniel Bulte
- FMRIB Centre, John Radcliffe Hospital, University of Oxford, Oxford, UK.
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69
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Baseline oxygenation in the brain: Correlation between respiratory-calibration and susceptibility methods. Neuroimage 2016; 125:920-931. [DOI: 10.1016/j.neuroimage.2015.11.007] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 11/03/2015] [Accepted: 11/03/2015] [Indexed: 01/21/2023] Open
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70
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Ma Y, Berman AJ, Pike GB. The effect of dissolved oxygen on the relaxation rates of blood plasma: Implications for hyperoxia calibrated BOLD. Magn Reson Med 2015; 76:1905-1911. [DOI: 10.1002/mrm.26069] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 10/05/2015] [Accepted: 11/02/2015] [Indexed: 12/18/2022]
Affiliation(s)
- Yuhan Ma
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University; Montreal Quebec Canada
| | - Avery J.L. Berman
- McConnell Brain Imaging Centre, Montreal Neurological Institute, McGill University; Montreal Quebec Canada
- Department of Radiology and Hotchkiss Brain Institute; University of Calgary; Calgary Alberta Canada
| | - G. Bruce Pike
- Department of Radiology and Hotchkiss Brain Institute; University of Calgary; Calgary Alberta Canada
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71
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Özbay PS, Rossi C, Kocian R, Redle M, Boss A, Pruessmann KP, Nanz D. Effect of respiratory hyperoxic challenge on magnetic susceptibility in human brain assessed by quantitative susceptibility mapping (QSM). NMR IN BIOMEDICINE 2015; 28:1688-1696. [PMID: 26484968 DOI: 10.1002/nbm.3433] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 09/04/2015] [Accepted: 09/17/2015] [Indexed: 06/05/2023]
Abstract
The purpose of this study was to measure the regional change of magnetic susceptibility in human brain upon inhalation of 100% oxygen by MRI quantitative susceptibility mapping (QSM). Fourteen healthy volunteers were scanned in a 3 T MR scanner with a 3D multi-gradient-echo sequence while breathing medical air (normoxia) and pure oxygen (hyperoxia). QSM images and R2* maps were calculated. Mean susceptibility differences versus white matter were measured in regions of interest covering veins, gray matter (GM), and cerebrospinal fluid (CSF) under both conditions. Hyperoxia resulted in a strong susceptibility decrease in large veins (-154.4 ± 65.9 ppb, p < 10(-6)), in a smaller reduction in GM (-1.3 ± 1 ppb, p < 0.001), and in a susceptibility increase in ventricular CSF (3.8 ± 1.8 ppb, p < 10(-5)). The susceptibility decrease in veins implied an increase of venous oxygen saturation (SvO2) by 10.1 ± 4.0%. Compared with QSM, R2* was more seriously affected by long-distance effects not related to local tissue oxygenation and increased in cerebral frontal regions (3 ± 2 s(-1), p < 0.0004) due to paramagnetic molecular oxygen in cavities. The results highlight the potential of QSM to yield region-specific quantitative oxygenation information, and, thus, for applications such as oxygen-therapy monitoring or identification of hypoxic tumor tissue during radiotherapy planning.
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Affiliation(s)
- Pinar Senay Özbay
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology, Zurich, Switzerland
- University of Zurich and ETH Zürich, Institute for Biomedical Engineering, Zurich, Switzerland
| | - Cristina Rossi
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology, Zurich, Switzerland
| | - Roman Kocian
- University Hospital Zurich, Institute of Anesthesiology, Zurich, Switzerland
| | - Manuel Redle
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology, Zurich, Switzerland
| | - Andreas Boss
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology, Zurich, Switzerland
| | - Klaas Paul Pruessmann
- University of Zurich and ETH Zürich, Institute for Biomedical Engineering, Zurich, Switzerland
| | - Daniel Nanz
- University Hospital Zurich and University of Zurich, Institute of Diagnostic and Interventional Radiology, Zurich, Switzerland
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72
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Siero JCW, Strother MK, Faraco CC, Hoogduin H, Hendrikse J, Donahue MJ. In vivo quantification of hyperoxic arterial blood water T1. NMR IN BIOMEDICINE 2015; 28:1518-25. [PMID: 26419505 PMCID: PMC4618707 DOI: 10.1002/nbm.3411] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 08/20/2015] [Accepted: 08/24/2015] [Indexed: 06/05/2023]
Abstract
Normocapnic hyperoxic and hypercapnic hyperoxic gas challenges are increasingly being used in cerebrovascular reactivity (CVR) and calibrated functional MRI experiments. The longitudinal arterial blood water relaxation time (T1a) change with hyperoxia will influence signal quantification through mechanisms relating to elevated partial pressure of plasma-dissolved O2 (pO2) and increased oxygen bound to hemoglobin in arteries (Ya) and veins (Yv). The dependence of T1a on Ya and Yv has been elegantly characterized ex vivo; however, the combined influence of pO2, Ya and Yv on T1a in vivo under normal ventilation has not been reported. Here, T1a is calculated during hyperoxia in vivo by a heuristic approach that evaluates T1 -dependent arterial spin labeling (ASL) signal changes to varying gas stimuli. Healthy volunteers (n = 14; age, 31.5 ± 7.2 years) were scanned using pseudo-continuous ASL in combination with room air (RA; 21% O2/79% N2), hypercapnic normoxic (HN; 5% CO2/21% O2/74% N2) and hypercapnic hyperoxic (HH; 5% CO2/95% O2) gas administration. HH T1a was calculated by requiring that the HN and HH cerebral blood flow (CBF) change be identical. The HH protocol was then repeated in patients (n = 10; age, 61.4 ± 13.3 years) with intracranial stenosis to assess whether an HH T1a decrease prohibited ASL from being performed in subjects with known delayed blood arrival times. Arterial blood T1a decreased from 1.65 s at baseline to 1.49 ± 0.07 s during HH. In patients, CBF values in the affected flow territory for the HH condition were increased relative to baseline CBF values and were within the physiological range (RA CBF = 36.6 ± 8.2 mL/100 g/min; HH CBF = 45.2 ± 13.9 mL/100 g/min). It can be concluded that hyperoxic (95% O2) 3-T arterial blood T1aHH = 1.49 ± 0.07 s relative to a normoxic T1a of 1.65 s.
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Affiliation(s)
- Jeroen C W Siero
- Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Megan K Strother
- Radiology and Radiological Sciences, Vanderbilt Medical Center, Nashville, TN, USA
- Neurological Surgery, Vanderbilt Medical Center, Nashville, TN, USA
| | - Carlos C Faraco
- Radiology and Radiological Sciences, Vanderbilt Medical Center, Nashville, TN, USA
| | - Hans Hoogduin
- Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Jeroen Hendrikse
- Radiology, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Manus J Donahue
- Radiology and Radiological Sciences, Vanderbilt Medical Center, Nashville, TN, USA
- Neurology, Vanderbilt Medical Center, Nashville, TN, USA
- Psychiatry, Vanderbilt Medical Center, Nashville, TN, USA
- Vanderbilt Brain Institute, Vanderbilt Medical Center, Nashville, TN, USA
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73
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Poublanc J, Crawley AP, Sobczyk O, Montandon G, Sam K, Mandell DM, Dufort P, Venkatraghavan L, Duffin J, Mikulis DJ, Fisher JA. Measuring cerebrovascular reactivity: the dynamic response to a step hypercapnic stimulus. J Cereb Blood Flow Metab 2015; 35:1746-56. [PMID: 26126862 PMCID: PMC4635229 DOI: 10.1038/jcbfm.2015.114] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 04/13/2015] [Accepted: 04/14/2015] [Indexed: 11/09/2022]
Abstract
We define cerebral vascular reactivity (CVR) as the ratio of the change in blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal (S) to an increase in blood partial pressure of CO2 (PCO2): % Δ S/Δ PCO2 mm Hg. Our aim was to further characterize CVR into dynamic and static components and then study 46 healthy subjects collated into a reference atlas and 20 patients with unilateral carotid artery stenosis. We applied an abrupt boxcar change in PCO2 and monitored S. We convolved the PCO2 with a set of first-order exponential functions whose time constant τ was increased in 2-second intervals between 2 and 100 seconds. The τ corresponding to the best fit between S and the convolved PCO2 was used to score the speed of response. Additionally, the slope of the regression between S and the convolved PCO2 represents the steady-state CVR (ssCVR). We found that both prolongations of τ and reductions in ssCVR (compared with the reference atlas) were associated with the reductions in CVR on the side of the lesion. τ and ssCVR are respectively the dynamic and static components of measured CVR.
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Affiliation(s)
- Julien Poublanc
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | - Adrian P Crawley
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | - Olivia Sobczyk
- Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Gaspard Montandon
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | - Kevin Sam
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Daniel M Mandell
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | - Paul Dufort
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada
| | | | - James Duffin
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada.,Department of Anaesthesia and Pain Management, University Health Network, Toronto, Ontario, Canada
| | - David J Mikulis
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Joseph A Fisher
- Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario, Canada.,Department of Anaesthesia and Pain Management, University Health Network, Toronto, Ontario, Canada
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74
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Blockley NP, Griffeth VEM, Stone AJ, Hare HV, Bulte DP. Sources of systematic error in calibrated BOLD based mapping of baseline oxygen extraction fraction. Neuroimage 2015; 122:105-13. [PMID: 26254114 DOI: 10.1016/j.neuroimage.2015.07.059] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 06/16/2015] [Accepted: 07/20/2015] [Indexed: 11/27/2022] Open
Abstract
Recently a new class of calibrated blood oxygen level dependent (BOLD) functional magnetic resonance imaging (MRI) methods were introduced to quantitatively measure the baseline oxygen extraction fraction (OEF). These methods rely on two respiratory challenges and a mathematical model of the resultant changes in the BOLD functional MRI signal to estimate the OEF. However, this mathematical model does not include all of the effects that contribute to the BOLD signal, it relies on several physiological assumptions and it may be affected by intersubject physiological variability. The aim of this study was to investigate these sources of systematic error and their effect on estimating the OEF. This was achieved through simulation using a detailed model of the BOLD signal. Large ranges for intersubject variability in baseline physiological parameters such as haematocrit and cerebral blood volume were considered. Despite this the uncertainty in the relationship between the measured BOLD signals and the OEF was relatively low. Investigations of the physiological assumptions that underlie the mathematical model revealed that OEF measurements are likely to be overestimated if oxygen metabolism changes during hypercapnia or cerebral blood flow changes under hyperoxia. Hypoxic hypoxia was predicted to result in an underestimation of the OEF, whilst anaemic hypoxia was found to have only a minimal effect.
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Affiliation(s)
- Nicholas P Blockley
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
| | - Valerie E M Griffeth
- Department of Bioengineering and Medical Scientist Training Program, University of California San Diego, La Jolla, CA, USA
| | - Alan J Stone
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Hannah V Hare
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Daniel P Bulte
- FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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75
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Quantitative T2, T2*, and T2' MR imaging in patients with ischemic leukoaraiosis might detect microstructural changes and cortical hypoxia. Neuroradiology 2015; 57:1023-30. [PMID: 26227168 DOI: 10.1007/s00234-015-1565-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 07/13/2015] [Indexed: 01/21/2023]
Abstract
INTRODUCTION Quantitative MRI with T2, T2*, and T2' mapping has been shown to non-invasively depict microstructural changes (T2) and oxygenation status (T2* and T2') that are invisible on conventional MRI. Therefore, we aimed to assess whether T2 and T2' quantification detects cerebral (micro-)structural damage and chronic hypoxia in lesions and in normal appearing white matter (WM) and gray matter (GM) of patients with ischemic leukoaraiosis (IL). Measurements were complemented by the assessment of the cerebral blood flow (CBF) and the degree of GM and WM atrophy. METHODS Eighteen patients with IL and 18 age-matched healthy controls were included. High-resolution, motion-corrected T2, T2*, and T2' mapping, CBF mapping (pulsed arterial spin labeling, PASL), and segmentation of GM and WM were used to depict specific changes in both groups. All parameters were compared between patients and healthy controls, using t testing. Values of p < 0.05 were accepted as statistically significant. RESULTS Patients showed significantly increased T2 in lesions (p < 0.01) and in unaffected WM (p = 0.045) as well as significantly increased T2* in lesions (p = 0.003). A significant decrease of T2' was detected in patients in unaffected WM (p = 0.027), while no T2' changes were observed in GM (p = 0.13). Both unaffected WM and GM were significantly decreased in volume in the patient-group (p < 0.01). No differences of PASL-based CBF could be shown. CONCLUSION Non-invasive quantitative MRI with T2, T2*, and T2' mapping might be used to detect subtle structural and metabolic changes in IL. Assessing the grade of microstructural damage and hypoxia might be helpful to monitor disease progression and to perform risk assessment.
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Affiliation(s)
- K O Pryor
- Department of Anesthesiology, Weill Cornell Medical College, 525 East 68th Street, New York, NY 10065, USA
| | - M M Berger
- Department of Anesthesiology, Perioperative and General Critical Care Medicine, Salzburg General Hospital, Paracelsus Medical University, Müllner Haupstraße 48, Salzburg 5020, Austria
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77
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Normobaric oxygen worsens outcome after a moderate traumatic brain injury. J Cereb Blood Flow Metab 2015; 35:1137-44. [PMID: 25690469 PMCID: PMC4640244 DOI: 10.1038/jcbfm.2015.18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 01/12/2015] [Accepted: 01/16/2015] [Indexed: 11/08/2022]
Abstract
Traumatic brain injury (TBI) is a multifaceted injury and a leading cause of death in children, young adults, and increasingly in Veterans. However, there are no neuroprotective agents clinically available to counteract damage or promote repair after brain trauma. This study investigated the neuroprotective effects of normobaric oxygen (NBO) after a controlled cortical impact in rats. The central hypothesis was that NBO treatment would reduce lesion volume and functional deficits compared with air-treated animals after TBI by increasing brain oxygenation thereby minimizing ischemic injury. In a randomized double-blinded design, animals received either NBO (n = 8) or normal air (n = 8) after TBI. Magnetic resonance imaging (MRI) was performed 0 to 3 hours, and 1, 2, 7, and 14 days after an impact to the primary forelimb somatosensory cortex. Behavioral assessments were performed before injury induction and before MRI scans on days 2, 7, and 14. Nissl staining was performed on day 14 to corroborate the lesion volume detected from MRI. Contrary to our hypothesis, we found that NBO treatment increased lesion volume in a rat model of moderate TBI and had no positive effect on behavioral measures. Our results do not promote the acute use of NBO in patients with moderate TBI.
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78
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Boudiaf N, Attyé A, Warnking JM, Troprès I, Lamalle L, Pietras J, Krainik A. BOLD fMRI of cerebrovascular reactivity in the middle cerebral artery territory: A 100 volunteers' study. J Neuroradiol 2015; 42:338-44. [PMID: 26031884 DOI: 10.1016/j.neurad.2015.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 03/26/2015] [Accepted: 04/05/2015] [Indexed: 11/15/2022]
Abstract
BACKGROUND AND PURPOSE The assessment of cerebrovascular reactivity (CVR) has shown promising results for its use in medical diagnosis and prognosis, especially in patients suffering from severe intracranial arterial stenosis. However, its quantification remains uncertain because of a large variability inherent in brain anatomy and in methodological settings. To overcome this variability, we provide lateralization index (LI) values for CVR within the middle cerebral artery territory to detect CVR impairment. MATERIALS AND METHODS We assessed CVR in 100 volunteers (41 females; 47.52 ± 21.58 years) without cervico-encephalic arterial stenosis using BOLD-fMRI contrast with a block-design hypercapnic challenge. Averaged end-tidal CO2 was used as a physiological regressor for statistical analyses with a general linear model. We measured %BOLD signal-change in segmented gray matter regions of interest in the middle cerebral artery territory (MCA). We calculated a laterality index according to the following formula: LI=(CVRleft-CVRright)/(CVRleft+CVRright). We tested the effects of methodological settings (i.e. hypercapnic gas, gas administration means, MR acquisition and sex) on %BOLD signal change and LI values with analysis of variance. RESULTS No adverse effects of the hypercapnic challenge were reported. LI values were independent of experimental conditions. Mean LI calculated in MCA territories was 0.016 ± 0.031, giving the lower and upper limits of 95% (m ± 2SD) of this population distribution at]-0.05; 0.08[. CONCLUSION LI can effectively help us to overcome measurement variabilities. Therefore, it can be used to detect abnormal asymmetries in CVR and identify patients at higher risk of ischemic stroke.
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Affiliation(s)
- Naïla Boudiaf
- Université Grenoble Alpes 3bis, CNRS, LPNC, 38000 Grenoble, France; Université Savoie 3, LPNC, 73000 Chambéry, France.
| | - Arnaud Attyé
- Inserm, université Grenoble Alpes, GIN, CHU de Grenoble, 38000 Grenoble, France; Department of Neuroradiology and MRI, University Hospital of Grenoble-IFR1, Grenoble, France
| | - Jan M Warnking
- Inserm, université Grenoble Alpes, GIN, CHU de Grenoble, 38000 Grenoble, France
| | - Irène Troprès
- Inserm, université Grenoble Alpes, GIN, CHU de Grenoble, 38000 Grenoble, France; Inserm, université Grenoble Alpes, CNRS, IRMaGe, CHU de Grenoble, 38000 Grenoble, France
| | - Laurent Lamalle
- Inserm, université Grenoble Alpes, CNRS, IRMaGe, CHU de Grenoble, 38000 Grenoble, France
| | - Johan Pietras
- Inserm, université Grenoble Alpes, CNRS, IRMaGe, CHU de Grenoble, 38000 Grenoble, France
| | - Alexandre Krainik
- Inserm, université Grenoble Alpes, GIN, CHU de Grenoble, 38000 Grenoble, France; Inserm, université Grenoble Alpes, CNRS, IRMaGe, CHU de Grenoble, 38000 Grenoble, France; Department of Neuroradiology and MRI, University Hospital of Grenoble-IFR1, Grenoble, France
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79
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The dynamics of cerebrovascular reactivity shown with transfer function analysis. Neuroimage 2015; 114:207-16. [PMID: 25891374 DOI: 10.1016/j.neuroimage.2015.04.029] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Revised: 04/06/2015] [Accepted: 04/11/2015] [Indexed: 01/24/2023] Open
Abstract
Cerebrovascular reactivity (CVR) is often defined as the increase in cerebral blood flow (CBF) produced by an increase in carbon dioxide (CO2) and may be used clinically to assess the health of the cerebrovasculature. When CBF is estimated using blood oxygen level dependent (BOLD) magnetic resonance imaging, CVR values for each voxel can be displayed using a color scale mapped onto the corresponding anatomical scan. While these CVR maps therefore show the distribution of cerebrovascular reactivity, they only provide an estimate of the magnitude of the cerebrovascular response, and do not indicate the time course of the response; whether rapid or slow. Here we describe transfer function analysis (TFA) of the BOLD response to CO2 that provides not only the magnitude of the response (gain) but also the phase and coherence. The phase can be interpreted as indicating the speed of response and so can distinguish areas where the response is slowed. The coherence measures the fidelity with which the response follows the stimulus. The examples of gain, phase and coherence maps obtained from TFA of previously recorded test data from patients and healthy individuals demonstrate that these maps may enhance assessment of cerebrovascular pathophysiology by providing insight into the dynamics of cerebral blood flow control and distribution.
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80
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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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81
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Comparing cerebrovascular reactivity measured using BOLD and cerebral blood flow MRI: The effect of basal vascular tension on vasodilatory and vasoconstrictive reactivity. Neuroimage 2015; 110:110-23. [PMID: 25655446 DOI: 10.1016/j.neuroimage.2015.01.050] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 01/15/2015] [Accepted: 01/26/2015] [Indexed: 11/23/2022] Open
Abstract
Cerebrovascular reactivity (CVR) is an important metric of cerebrovascular health. While the BOLD fMRI method in conjunction with carbon-dioxide (CO2) based vascular manipulation has been the most commonly used, the BOLD signal is not a direct measure of vascular changes, and the use of arterial-spin labeling (ASL) cerebral blood flow (CBF) imaging is increasingly advocated. Nonetheless, given the differing dependencies of BOLD and CBF on vascular baseline conditions and the diverse CO2 manipulation types currently used in the literature, knowledge of potential biases introduced by each technique is critical for the interpretation of CVR measurements. In this work, we use simultaneous BOLD-CBF acquisitions during both vasodilatory (hypercapnic) and vasoconstrictive (hypocapnic) stimuli to measure CVR. We further imposed different levels of baseline vascular tension by inducing hypercapnic and hypocapnic baselines, separately from normocapnia by 4mmHg. We saw significant and diverse dependencies on vascular stimulus and baseline condition in both BOLD and CBF CVR measurements: (i) BOLD-based CVR is more sensitive to basal vascular tension than CBF-based CVR; (ii) the use of a combination of vasodilatory and vasoconstrictive stimuli maximizes the sensitivity of CBF-based CVR to vascular tension changes; (iii) the BOLD and CBF vascular response delays are both significantly lengthened at predilated baseline. As vascular tension can often be altered by potential pathology, our findings are important considerations when interpreting CVR measurements in health and disease.
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82
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Croal PL, Hall EL, Driver ID, Brookes MJ, Gowland PA, Francis ST. The effect of isocapnic hyperoxia on neurophysiology as measured with MRI and MEG. Neuroimage 2015; 105:323-31. [DOI: 10.1016/j.neuroimage.2014.10.036] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 08/27/2014] [Accepted: 10/14/2014] [Indexed: 10/24/2022] Open
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83
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Krieger SN, Gauthier CJ, Ivanov D, Huber L, Roggenhofer E, Sehm B, Turner R, Egan GF. Regional reproducibility of calibrated BOLD functional MRI: Implications for the study of cognition and plasticity. Neuroimage 2014; 101:8-20. [DOI: 10.1016/j.neuroimage.2014.06.072] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 06/24/2014] [Accepted: 06/28/2014] [Indexed: 02/02/2023] Open
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84
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Fan AP, Evans KC, Stout JN, Rosen BR, Adalsteinsson E. Regional quantification of cerebral venous oxygenation from MRI susceptibility during hypercapnia. Neuroimage 2014; 104:146-55. [PMID: 25300201 DOI: 10.1016/j.neuroimage.2014.09.068] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 08/18/2014] [Accepted: 09/30/2014] [Indexed: 12/27/2022] Open
Abstract
There is an unmet medical need for noninvasive imaging of regional brain oxygenation to manage stroke, tumor, and neurodegenerative diseases. Oxygenation imaging from magnetic susceptibility in MRI is a promising new technique to measure local venous oxygen extraction fraction (OEF) along the cerebral venous vasculature. However, this approach has not been tested in vivo at different levels of oxygenation. The primary goal of this study was to test whether susceptibility imaging of oxygenation can detect OEF changes induced by hypercapnia, via CO2 inhalation, within selected a priori brain regions. Ten healthy subjects were scanned at 3T with a 32-channel head coil. The end-tidal CO2 (ETCO2) was monitored continuously and inspired gases were adjusted to achieve steady-state conditions of eucapnia (41±3mmHg) and hypercapnia (50±4mmHg). Gradient echo phase images and pseudo-continuous arterial spin labeling (pcASL) images were acquired to measure regional OEF and CBF respectively during eucapnia and hypercapnia. By assuming constant cerebral oxygen consumption throughout both gas states, regional CBF values were computed to predict the local change in OEF in each brain region. Hypercapnia induced a relative decrease in OEF of -42.3% in the straight sinus, -39.9% in the internal cerebral veins, and approximately -50% in pial vessels draining each of the occipital, parietal, and frontal cortical areas. Across volunteers, regional changes in OEF correlated with changes in ETCO2. The reductions in regional OEF (via phase images) were significantly correlated (P<0.05) with predicted reductions in OEF derived from CBF data (via pcASL images). These findings suggest that susceptibility imaging is a promising technique for OEF measurements, and may serve as a clinical biomarker for brain conditions with aberrant regional oxygenation.
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Affiliation(s)
- Audrey P Fan
- Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA; Radiology, Athinoula A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Charlestown, MA, USA.
| | - Karleyton C Evans
- Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA; Psychiatry, Massachusetts General Hospital East, 149 Thirteenth Street, Charlestown, MA, USA.
| | - Jeffrey N Stout
- Radiology, Athinoula A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Charlestown, MA, USA; Harvard-MIT Health Sciences and Technology, Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA.
| | - Bruce R Rosen
- Radiology, Athinoula A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Charlestown, MA, USA; Harvard-MIT Health Sciences and Technology, Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA.
| | - Elfar Adalsteinsson
- Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA; Radiology, Athinoula A. Martinos Center for Biomedical Imaging, 149 Thirteenth Street, Charlestown, MA, USA; Harvard-MIT Health Sciences and Technology, Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA.
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85
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Postnatal hyperoxia exposure differentially affects hepatocytes and liver haemopoietic cells in newborn rats. PLoS One 2014; 9:e105005. [PMID: 25115881 PMCID: PMC4130630 DOI: 10.1371/journal.pone.0105005] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 07/17/2014] [Indexed: 11/29/2022] Open
Abstract
Premature newborns are frequently exposed to hyperoxic conditions and experimental data indicate modulation of liver metabolism by hyperoxia in the first postnatal period. Conversely, nothing is known about possible modulation of growth factors and signaling molecules involved in other hyperoxic responses and no data are available about the effects of hyperoxia in postnatal liver haematopoiesis. The aim of the study was to analyse the effects of hyperoxia in the liver tissue (hepatocytes and haemopoietic cells) and to investigate possible changes in the expression of Vascular Endothelial Growth Factor (VEGF), Matrix Metalloproteinase 9 (MMP-9), Hypoxia-Inducible Factor-1α (HIF-1α), endothelial Nitric Oxide Synthase (eNOS), and Nuclear Factor-kB (NF-kB). Experimental design of the study involved exposure of newborn rats to room air (controls), 60% O2 (moderate hyperoxia), or 95% O2 (severe hyperoxia) for the first two postnatal weeks. Immunohistochemical and Western blot analyses were performed. Severe hyperoxia increased hepatocyte apoptosis and MMP-9 expression and decreased VEGF expression. Reduced content in reticular fibers was found in moderate and severe hyperoxia. Some other changes were specifically produced in hepatocytes by moderate hyperoxia, i.e., upregulation of HIF-1α and downregulation of eNOS and NF-kB. Postnatal severe hyperoxia exposure increased liver haemopoiesis and upregulated the expression of VEGF (both moderate and severe hyperoxia) and eNOS (severe hyperoxia) in haemopoietic cells. In conclusion, our study showed different effects of hyperoxia on hepatocytes and haemopoietic cells and differential involvement of the above factors. The involvement of VEGF and eNOS in the liver haemopoietic response to hyperoxia may be hypothesized.
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86
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Rincon F, Kang J, Vibbert M, Urtecho J, Athar MK, Jallo J. Significance of arterial hyperoxia and relationship with case fatality in traumatic brain injury: a multicentre cohort study. J Neurol Neurosurg Psychiatry 2014; 85:799-805. [PMID: 23794718 DOI: 10.1136/jnnp-2013-305505] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVE In this retrospective multi-centre cohort study, we tested the hypothesis that hyperoxia was not associated with higher in-hospital case fatality in ventilated traumatic brain injury (TBI) patients admitted to the intensive care unit (ICU). METHODS Admissions of ventilated TBI patients who had arterial blood gases within 24 h of admission to the ICU at 61 US hospitals between 2003 and 2008 were identified. Hyperoxia was defined as PaO2 ≥300 mm Hg (39.99 kPa), hypoxia as any PaO2 <60 mm Hg (7.99 kPa) or PaO2/FiO2 ratio ≤300 and normoxia, not defined as hyperoxia or hypoxia. The primary outcome was in-hospital case fatality. RESULTS Over the 5-year period, we identified 1212 ventilated TBI patients, of whom 403 (33%) were normoxic, 553 (46%) were hypoxic and 256 (21%) were hyperoxic. The case-fatality was higher in the hypoxia group (224/553 [41%], crude OR 2.3, 95% CI 1.7-3.0, p<.0001) followed by hyperoxia (80/256 [32%], crude OR 1.5, 95% CI 1.1-2.5, p=.01) as compared to normoxia (87/403 [23%]). In a multivariate analysis adjusted for other potential confounders, the probability of being exposed to hyperoxia and hospital-specific characteristics, exposure to hyperoxia was independently associated with higher in-hospital case fatality adjusted OR 1.5, 95% CI 1.02-2.4, p=0.04. CONCLUSIONS In ventilated TBI patients admitted to the ICU, arterial hyperoxia was independently associated with higher in-hospital case fatality. In the absence of results from clinical trials, unnecessary oxygen delivery should be avoided in critically ill ventilated TBI patients.
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Affiliation(s)
- Fred Rincon
- Department of Neurology, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA Department of Neurology Neurosurgery, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA
| | - Joon Kang
- Department of Neurology, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA
| | - Matthew Vibbert
- Department of Neurology, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA Department of Neurology Neurosurgery, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA
| | - Jacqueline Urtecho
- Department of Neurology, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA Department of Neurology Neurosurgery, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA
| | - M Kamran Athar
- Department of Neurology Neurosurgery, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA Department of Neurology Medicine, Philadelphia, Pennsylvania, USA
| | - Jack Jallo
- Department of Neurology Neurosurgery, Divisions of Critical Care and Neurotrauma, Philadelphia, Pennsylvania, USA
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Donahue MJ, Faraco CC, Strother MK, Chappell MA, Rane S, Dethrage LM, Hendrikse J, Siero JCW. Bolus arrival time and cerebral blood flow responses to hypercarbia. J Cereb Blood Flow Metab 2014; 34:1243-52. [PMID: 24780904 PMCID: PMC4083394 DOI: 10.1038/jcbfm.2014.81] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 04/07/2014] [Accepted: 04/09/2014] [Indexed: 11/09/2022]
Abstract
The purpose of this study was to evaluate how cerebral blood flow and bolus arrival time (BAT) measures derived from arterial spin labeling (ASL) MRI data change for different hypercarbic gas stimuli. Pseudocontinuous ASL (pCASL) was applied (3.0T; spatial resolution=4 × 4 × 7 mm(3); repetition time/echo time (TR/TE)=3,600/11 ms) sequentially in healthy volunteers (n=12; age=30±4 years) for separate experiments in which (i) normocarbic normoxia (i.e., room air), hypercarbic normoxia (i.e., 5% CO₂/21% O₂/74% N2), and hypercarbic hyperoxia (i.e., carbogen: 5% CO₂/95% O₂) gas was administered (12 L/minute). Cerebral blood flow and BAT changes were quantified using models that account for macrovascular signal and partial volume effects in all gray matter and regionally in cerebellar, temporal, occipital, frontal, and parietal lobes. Regional reductions in BAT of 4.6% to 7.7% and 3.3% to 6.6% were found in response to hypercarbic normoxia and hypercarbic hyperoxia, respectively. Cerebral blood flow increased by 8.2% to 27.8% and 3.5% to 19.8% for hypercarbic normoxia and hypercarbic hyperoxia, respectively. These findings indicate that changes in BAT values may bias functional ASL data and thus should be considered when choosing appropriate experimental parameters in calibrated functional magnetic resonance imaging or ASL cerebrovascular reactivity experiments that use hypercarbic gas stimuli.
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Affiliation(s)
- Manus J Donahue
- 1] Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA [2] Psychiatry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA [3] Neurology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA [4] Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA
| | - Carlos C Faraco
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Megan K Strother
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | | | - Swati Rane
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Lindsey M Dethrage
- Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
| | - Jeroen Hendrikse
- Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jeroen C W Siero
- Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
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88
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Germuska M, Bulte DP. MRI measurement of oxygen extraction fraction, mean vessel size and cerebral blood volume using serial hyperoxia and hypercapnia. Neuroimage 2014; 92:132-42. [DOI: 10.1016/j.neuroimage.2014.02.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 01/06/2014] [Accepted: 02/01/2014] [Indexed: 01/11/2023] Open
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89
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Faraco CC, Strother MK, Dethrage LM, Jordan L, Singer R, Clemmons PF, Donahue MJ. Dual echo vessel-encoded ASL for simultaneous BOLD and CBF reactivity assessment in patients with ischemic cerebrovascular disease. Magn Reson Med 2014; 73:1579-92. [PMID: 24757044 DOI: 10.1002/mrm.25268] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 04/05/2014] [Accepted: 04/07/2014] [Indexed: 11/07/2022]
Abstract
PURPOSE Blood oxygenation level-dependent (BOLD)-weighted and vessel-encoded arterial spin labeling (VE-ASL) MRI provide complementary information and can be used in sequence to gauge hemodynamic contributions to cerebrovascular reactivity. Here, cerebrovascular reactivity is assessed using dual echo VE-ASL MRI to understand how VE labeling preparations influence BOLD and ASL contrast in flow-limited and healthy perfusion territories. METHODS Patients (n = 12; age = 55 +/- 14 years; 6F/6M) presenting with ischemic steno-occlusive cerebrovascular disease underwent 3.0T angiographic imaging, T1 -weighted structural, and planning-free dual echo hypercarbic hyperoxic (i.e., carbogen) VE-ASL MRI. Vasculopathy extent, timecourses, and cerebrovascular reactivity (signal change and Z-statistic) for different VE-ASL images were contrasted across flow territories and Bonferroni-corrected P-values reported. RESULTS BOLD cerebrovascular reactivity (i.e., long-TE VE-ASL) Z-statistics were similarly sensitive to asymmetric disease (P ≤ 0.002) regardless of labeling scenario. Cerebral blood flow reactivity correlated significantly with BOLD reactivity (Z-statistic). However, BOLD signal changes did not differ significantly between labeling scenarios (P > 0.003) or across territories (P > 0.002), indicating BOLD signal changes in response to carbogen offer low sensitivity to lateralizing disease. CONCLUSION Dual echo VE-ASL can provide simultaneous cerebral blood flow and qualitative BOLD contrast consistent with lateralizing disease severity in patients with asymmetric steno-occlusive disease. The methodological strengths and limitations of composite BOLD and VE-ASL measurements in the clinic are discussed.
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Affiliation(s)
- Carlos C Faraco
- Department of Radiology and Radiological Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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90
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Yang Y, Zhang YG, Lin GA, Xie HQ, Pan HT, Huang BQ, Liu JD, Liu H, Zhang N, Li L, Chen JH. The effects of different hyperbaric oxygen manipulations in rats after traumatic brain injury. Neurosci Lett 2014; 563:38-43. [DOI: 10.1016/j.neulet.2014.01.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 12/14/2013] [Accepted: 01/02/2014] [Indexed: 11/16/2022]
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91
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Stability of cerebral metabolism and substrate availability in humans during hypoxia and hyperoxia. Clin Sci (Lond) 2014; 126:661-70. [DOI: 10.1042/cs20130343] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Marked elevations in brain blood flow with progressive hypoxaemia and related reductions in oxygen content resulted in a well-maintained oxygen delivery to the brain. As such, cerebral metabolism is still supported almost exclusively by carbohydrate oxidation during severe levels of hypoxaemia.
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92
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Algattas H, Huang JH. Traumatic Brain Injury pathophysiology and treatments: early, intermediate, and late phases post-injury. Int J Mol Sci 2013; 15:309-41. [PMID: 24381049 PMCID: PMC3907812 DOI: 10.3390/ijms15010309] [Citation(s) in RCA: 158] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2013] [Revised: 12/02/2013] [Accepted: 12/20/2013] [Indexed: 12/25/2022] Open
Abstract
Traumatic Brain Injury (TBI) affects a large proportion and extensive array of individuals in the population. While precise pathological mechanisms are lacking, the growing base of knowledge concerning TBI has put increased emphasis on its understanding and treatment. Most treatments of TBI are aimed at ameliorating secondary insults arising from the injury; these insults can be characterized with respect to time post-injury, including early, intermediate, and late pathological changes. Early pathological responses are due to energy depletion and cell death secondary to excitotoxicity, the intermediate phase is characterized by neuroinflammation and the late stage by increased susceptibility to seizures and epilepsy. Current treatments of TBI have been tailored to these distinct pathological stages with some overlap. Many prophylactic, pharmacologic, and surgical treatments are used post-TBI to halt the progression of these pathologic reactions. In the present review, we discuss the mechanisms of the pathological hallmarks of TBI and both current and novel treatments which target the respective pathways.
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Affiliation(s)
- Hanna Algattas
- School of Medicine and Dentistry, University of Rochester Medical Center, 601 Elmwood Ave, Box 441, Rochester, NY 14642, USA.
| | - Jason H Huang
- School of Medicine and Dentistry, University of Rochester Medical Center, 601 Elmwood Ave, Box 441, Rochester, NY 14642, USA.
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93
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Impact of gas delivery systems on imaging studies of human cerebral blood flow. Radiol Res Pract 2013; 2013:694803. [PMID: 24392225 PMCID: PMC3874307 DOI: 10.1155/2013/694803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 11/08/2013] [Accepted: 11/13/2013] [Indexed: 11/30/2022] Open
Abstract
Purpose. To compare a semiopen breathing circuit with a non-rebreathing (Hudson mask) for MRI experiments involving gas delivery. Methods and Materials. Cerebral blood flow (CBF) was measured by quantitative phase contrast angiography of the internal carotid and basilar arteries in 18 volunteers (20–31 years). In 8 subjects, gases were delivered via a standard non-rebreathing (Hudson mask). In 10 subjects, gases were delivered using a modified “Mapleson A” semiopen anesthetic gas circuit and mouthpiece. All subjects were given 100% O2, medical air, and carbogen gas (95% O2 and 5% CO2) delivered at 15 L/min in a random order. Results. The Hudson mask group showed significant increases in CBF in response to increased FiCO2 compared to air (+9.8%). A small nonsignificant reduction in CBF (−2.4%) was seen in response to increased inspired concentrations of oxygen (FiO2). The Mapleson A group showed significantly larger changes in CBF in response to both increased inspired concentrations of carbon dioxide (FiCO2) (+32.2%, P < 0.05) and FiO2 (−14.6%, P < 0.01). Conclusions. The use of an anaesthetic gas delivery circuit avoids entrainment of room air and rebreathing effects that may otherwise adversely affect the experimental results.
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94
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Wise RG, Harris AD, Stone AJ, Murphy K. Measurement of OEF and absolute CMRO2: MRI-based methods using interleaved and combined hypercapnia and hyperoxia. Neuroimage 2013; 83:135-47. [PMID: 23769703 PMCID: PMC4151288 DOI: 10.1016/j.neuroimage.2013.06.008] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Revised: 05/30/2013] [Accepted: 06/05/2013] [Indexed: 02/02/2023] Open
Abstract
Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is most commonly used in a semi-quantitative manner to infer changes in brain activity. Despite the basis of the image contrast lying in the cerebral venous blood oxygenation level, quantification of absolute cerebral metabolic rate of oxygen consumption (CMRO2) has only recently been demonstrated. Here we examine two approaches to the calibration of fMRI signal to measure absolute CMRO2 using hypercapnic and hyperoxic respiratory challenges. The first approach is to apply hypercapnia and hyperoxia separately but interleaved in time and the second is a combined approach in which we apply hyperoxic challenges simultaneously with different levels of hypercapnia. Eleven healthy volunteers were studied at 3T using a dual gradient-echo spiral readout pulsed arterial spin labelling (ASL) imaging sequence. Respiratory challenges were conducted using an automated system of dynamic end-tidal forcing. A generalised BOLD signal model was applied, within a Bayesian estimation framework, that aims to explain the effects of modulation of CBF and arterial oxygen content to estimate venous deoxyhaemoglobin concentration ([dHb]0). Using CBF measurements combined with the estimated oxygen extraction fraction (OEF), absolute CMRO2 was calculated. The interleaved approach to hypercapnia and hyperoxia, as well as yielding estimates of CMRO2 and OEF demonstrated a significant increase in regional CBF, venous oxygen saturation (SvO2) (a decrease in OEF) and absolute CMRO2 in visual cortex in response to a continuous (20 min) visual task, demonstrating the potential for the method in measuring long term changes in CMRO2. The combined approach to oxygen and carbon dioxide modulation, as well as taking less time to acquire data, yielded whole brain grey matter estimates of CMRO2 and OEF of 184±45 μmol/100 g/min and 0.42±0.12 respectively, along with additional estimates of the vascular parameters α=0.33±0.06, the exponent relating relative increases in CBF to CBV, and β=1.35±0.13, the exponent relating deoxyhaemoglobin concentration to the relaxation rate R2*. Maps of cerebrovascular and cerebral metabolic parameters were also calculated. We show that combined modulation of oxygen and carbon dioxide can offer an experimentally more efficient approach to estimating OEF and absolute CMRO2 along with the additional vascular parameters that form an important part of the commonly used calibrated fMRI signal model.
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Affiliation(s)
- Richard G Wise
- Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Park Place, Cardiff CF10 3AT, UK.
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95
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Hare HV, Germuska M, Kelly ME, Bulte DP. Comparison of CO2 in air versus carbogen for the measurement of cerebrovascular reactivity with magnetic resonance imaging. J Cereb Blood Flow Metab 2013; 33:1799-805. [PMID: 23921896 PMCID: PMC3824179 DOI: 10.1038/jcbfm.2013.131] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 07/10/2013] [Accepted: 07/11/2013] [Indexed: 01/16/2023]
Abstract
Measurement of cerebrovascular reactivity (CVR) can give valuable information about existing pathology and the risk of adverse events, such as stroke. A common method of obtaining regional CVR values is by measuring the blood flow response to carbon dioxide (CO2)-enriched air using arterial spin labeling (ASL) or blood oxygen level-dependent (BOLD) imaging. Recently, several studies have used carbogen gas (containing only CO2 and oxygen) as an alternative stimulus. A direct comparison was performed between CVR values acquired by ASL and BOLD imaging using stimuli of (1) 5% CO2 in air and (2) 5% CO2 in oxygen (carbogen-5). Although BOLD and ASL CVR values are shown to be correlated for CO2 in air (mean response 0.11±0.03% BOLD, 4.46±1.80% ASL, n=16 hemispheres), this correlation disappears during a carbogen stimulus (0.36±0.06% BOLD, 4.97±1.30% ASL). It is concluded that BOLD imaging should generally not be used in conjunction with a carbogen stimulus when measuring CVR, and that care must be taken when interpreting CVR as measured by ASL, as values obtained from different stimuli (CO2 in air versus carbogen) are not directly comparable.
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Affiliation(s)
- Hannah V Hare
- 1] Nuffield Department of Clinical Neurosciences, FMRIB Centre, University of Oxford, Oxford, UK [2] Department of Physics, University of Oxford, Oxford, UK
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96
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Porzionato A, Macchi V, Zaramella P, Sarasin G, Grisafi D, Dedja A, Chiandetti L, De Caro R. Effects of postnatal hyperoxia exposure on the rat dentate gyrus and subventricular zone. Brain Struct Funct 2013; 220:229-47. [PMID: 24135771 DOI: 10.1007/s00429-013-0650-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2013] [Accepted: 10/04/2013] [Indexed: 12/27/2022]
Abstract
Premature newborns may be exposed to hyperoxia in the first postnatal period, but clinical and experimental works have raised the question of oxygen toxicity for the developing brain. However, specific analysis of hyperoxia exposure on neurogenesis is still lacking. Thus, the aim of the present study was to evaluate possible changes in the morphometric parameters of the main neurogenic sites in newborn rats exposed to 60 or 95 % oxygen for the first 14 postnatal days. The optical disector, a morphometric method based upon unbiased sampling principles of stereology, was applied to analyse cell densities, total volumes, and total cell numbers of the dentate gyrus (DG) and subventricular zone (SVZ). Apoptosis and proliferation were also studied by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling method and anti-ki67 immunohistochemistry, respectively. Severe hyperoxia increased the percentage of apoptotic cells in the DG. Moderate and severe hyperoxia induced a proliferative response both in the DG and SVZ, but the two neurogenic sites showed different changes in their morphometric parameters. The DG of both the hyperoxic groups showed lower volume and total cell number than that of the normoxic one. Conversely, the SVZ of newborn rats exposed to 95 % hyperoxia showed statistically significant higher volume and total cell number than SVZ of rats raised in normoxia. Our findings indicate that hyperoxia exposure in the first postnatal period affects both the neurogenic areas, although in different ways, i.e. reduction of DG and expansion of SVZ.
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Affiliation(s)
- Andrea Porzionato
- Section of Anatomy, Department of Molecular Medicine, University of Padova, Via A Gabelli 65, 35127, Padua, Italy
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97
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Krainik A, Villien M, Troprès I, Attyé A, Lamalle L, Bouvier J, Pietras J, Grand S, Le Bas JF, Warnking J. Functional imaging of cerebral perfusion. Diagn Interv Imaging 2013; 94:1259-78. [PMID: 24011870 DOI: 10.1016/j.diii.2013.08.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The functional imaging of perfusion enables the study of its properties such as the vasoreactivity to circulating gases, the autoregulation and the neurovascular coupling. Downstream from arterial stenosis, this imaging can estimate the vascular reserve and the risk of ischemia in order to adapt the therapeutic strategy. This method reveals the hemodynamic disorders in patients suffering from Alzheimer's disease or with arteriovenous malformations revealed by epilepsy. Functional MRI of the vasoreactivity also helps to better interpret the functional MRI activation in practice and in clinical research.
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Affiliation(s)
- A Krainik
- Clinique universitaire de neuroradiologie et IRM, CHU de Grenoble, CS 10217, 38043 Grenoble cedex, France; Inserm U836, université Joseph-Fourier, site santé, chemin Fortuné-Ferrini, 38706 La Tronche cedex, France; UMS IRMaGe, unité IRM 3T recherche, CHU de Grenoble, CS 10217, 38043 Grenoble cedex 9, France.
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98
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Micarelli A, Jacobsson H, Larsson SA, Jonsson C, Pagani M. Neurobiological insight into hyperbaric hyperoxia. Acta Physiol (Oxf) 2013; 209:69-76. [PMID: 23692702 DOI: 10.1111/apha.12116] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 05/02/2013] [Accepted: 05/15/2013] [Indexed: 11/29/2022]
Abstract
AIM Hyperbaric hyperoxia (HBO) is known to modulate aerobic metabolism, vasoreactivity and blood flow in the brain. Nevertheless, mechanisms underlying its therapeutic effects, especially in traumatic brain injury (TBI) and stroke patients, are debated. The present study aimed at investigating regional cerebral blood flow (rCBF) distribution during acute HBO exposure. METHODS Regional cerebral blood flow response was investigated in seven healthy subjects exposed to either normobaric normoxia or HBO with ambient pressure/inspired oxygen pressure of 101/21 and 250/250 kPa respectively. After 40 min at the desired pressure, they were injected a perfusion tracer and subsequently underwent brain single photon emission computed tomography. rCBF distribution changes in the whole brain were assessed by Statistical Parametric Mapping. RESULTS During HBO, an increased relative rCBF distribution was found in sensory-motor, premotor, visual and posterior cingulate cortices as well as in superior frontal gyrus, middle/inferior temporal and angular gyrus and cerebellum, mainly in the dominant hemisphere. During normobaric normoxia, a higher (99m) Tc-HMPAO distribution in the right insula and subcortical structures as well as in bilateral hippocampi and anterior cingulated cortex was found. CONCLUSIONS The present study firstly confirmed the rCBF distribution increase during HBO in sensory-motor and visual cortices, and it showed for the first time a higher perfusion tracer distribution in areas encompassed in dorsal attention system and in default mode network. These findings unfold both the externally directed cognition performance improvement related to the HBO and the internally directed cognition states during resting-state conditions, suggesting possible beneficial effects in TBI and stroke patients.
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Affiliation(s)
- A. Micarelli
- Department of Medical Sciences and Translational Medicine; ‘Tor Vergata’ University; Rome; Italy
| | - H. Jacobsson
- Department of Nuclear Medicine; Karolinska University Hospital; Stockholm; Sweden
| | - S. A. Larsson
- Department of Nuclear Medicine; Karolinska University Hospital; Stockholm; Sweden
| | - C. Jonsson
- Department of Nuclear Medicine; Karolinska University Hospital; Stockholm; Sweden
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99
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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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100
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Klychnikova EV, Tazina EV, Solodov AA, Petrikov SS, Godkov MA, Krylov VV. The effects of normobaric hyperoxia on oxidative stress and factors of endogenous vascular regulation in patients who suffered from non-traumatic subarachnoid hemorrhages and remained in critical condition. NEUROCHEM J+ 2013. [DOI: 10.1134/s1819712413030057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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