Measuring Cerebrovascular Reactivity: The Dynamic Response to a Step Hypercapnic Stimulus

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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Faculty Opinions recommendation of Staging Hemodynamic Failure With Blood Oxygen-Level-Dependent Functional Magnetic Resonance Imaging Cerebrovascular Reactivity: A Comparison Versus Gold Standard (15O-)H2O-Positron Emission Tomography.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.732571633.793542183 ◽

2018 ◽

Author(s):

James Duffin

Keyword(s):

Gold Standard ◽

Blood Oxygen Level Dependent ◽

Cerebrovascular Reactivity ◽

Emission Tomography ◽

Blood Oxygen ◽

Functional Magnetic Resonance ◽

Resonance Imaging ◽

Blood Oxygen Level ◽

Positron Emission ◽

Hemodynamic Failure

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Measurement of Cerebrovascular Reactivity as Blood Oxygen Level-Dependent Magnetic Resonance Imaging Signal Response to a Hypercapnic Stimulus in Mechanically Ventilated Patients

Journal of Stroke and Cerebrovascular Diseases ◽

10.1016/j.jstrokecerebrovasdis.2017.08.035 ◽

2018 ◽

Vol 27 (2) ◽

pp. 301-308 ◽

Cited By ~ 6

Author(s):

Lashmi Venkatraghavan ◽

Julien Poublanc ◽

Jay S. Han ◽

Olivia Sobczyk ◽

Casey Rozen ◽

...

Keyword(s):

Blood Oxygen Level Dependent ◽

Cerebrovascular Reactivity ◽

Blood Oxygen ◽

Oxygen Level ◽

Resonance Imaging ◽

Blood Oxygen Level ◽

Mechanically Ventilated ◽

Mechanically Ventilated Patients ◽

Signal Response ◽

Ventilated Patients

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Magnetic Resonance Imaging in Pediatric Migraine

Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques ◽

10.1017/cjn.2019.243 ◽

2019 ◽

Vol 46 (6) ◽

pp. 653-665

Author(s):

Megan E. Webb ◽

Farnaz Amoozegar ◽

Ashley D. Harris

Keyword(s):

Magnetic Resonance Imaging ◽

Magnetic Resonance ◽

Blood Oxygen Level Dependent ◽

Blood Oxygen ◽

Structural Studies ◽

Resonance Imaging ◽

Blood Oxygen Level ◽

Pediatric Migraine ◽

Magnetic Resonance Imaging Mri ◽

Using Data

ABSTRACT:This literature review provides an overview of the research using magnetic resonance imaging (MRI) in pediatric migraine and compares findings with the adult migraine literature. A literature search using PubMed was conducted using all relevant sources up to February 2019. Using MRI methods to categorize and explain pediatric migraine in comparison with adult migraine is important, in order to recognize and appreciate the differences between the two entities, both clinically and physiologically. We aim to demonstrate the differences and similarities between pediatric and adult migraine using data from white matter and gray matter structural studies, cerebral perfusion, metabolites, and functional MRI (fMRI) studies, including task-based and resting-state blood oxygen level-dependent studies. By doing this we identify areas that need further research, as well as possible areas where intervention could alter outcomes.

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Effects of short-term continuous positive airway pressure withdrawal on cerebral vascular reactivity measured by blood oxygen level-dependent magnetic resonance imaging in obstructive sleep apnoea: a randomised controlled trial

European Respiratory Journal ◽

10.1183/13993003.01854-2018 ◽

2019 ◽

Vol 53 (2) ◽

pp. 1801854 ◽

Cited By ~ 2

Author(s):

Sira Thiel ◽

Franziska Lettau ◽

Protazy Rejmer ◽

Cristina Rossi ◽

Sarah R. Haile ◽

...

Keyword(s):

Vascular Reactivity ◽

Positive Airway Pressure ◽

Blood Oxygen Level Dependent ◽

Sleep Apnoea ◽

Blood Oxygen ◽

Resonance Imaging ◽

Blood Oxygen Level ◽

Short Term ◽

Bold Mri ◽

Obstructive Sleep

Impaired cerebral vascular reactivity (CVR) increases long-term stroke risk. Obstructive sleep apnoea (OSA) is associated with peripheral vascular dysfunction and vascular events. The aim of this trial was to evaluate the effect of continuous positive airway pressure (CPAP) withdrawal on CVR.41 OSA patients (88% male, mean age 57±10 years) were randomised to either subtherapeutic or continuation of therapeutic CPAP. At baseline and after 2 weeks, patients underwent a sleep study and magnetic resonance imaging (MRI). CVR was estimated by quantifying the blood oxygen level-dependent (BOLD) MRI response to breathing stimuli.OSA did recur in the subtherapeutic CPAP group (mean treatment effect apnoea–hypopnoea index +38.0 events·h−1, 95% CI 24.2–52.0; p<0.001) but remained controlled in the therapeutic group. Although there was a significant increase in blood pressure upon CPAP withdrawal (mean treatment effect +9.37 mmHg, 95% CI 1.36–17.39; p=0.023), there was no significant effect of CPAP withdrawal on CVR assessedviaBOLD MRI under either hyperoxic or hypercapnic conditions.Short-term CPAP withdrawal did not result in statistically significant changes in CVR as assessed by functional MRI, despite the recurrence of OSA. We thus conclude that, unlike peripheral endothelial function, CVR is not affected by short-term CPAP withdrawal.

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Comparison of CO2 in Air Versus Carbogen for the Measurement of Cerebrovascular Reactivity with Magnetic Resonance Imaging

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.2013.131 ◽

2013 ◽

Vol 33 (11) ◽

pp. 1799-1805 ◽

Cited By ~ 28

Author(s):

Hannah V Hare ◽

Michael Germuska ◽

Michael E Kelly ◽

Daniel P Bulte

Keyword(s):

Arterial Spin Labeling ◽

Spin Labeling ◽

Blood Oxygen Level Dependent ◽

Cerebrovascular Reactivity ◽

Blood Oxygen ◽

Resonance Imaging ◽

Blood Oxygen Level ◽

Bold Imaging ◽

Flow Response ◽

Alternative Stimulus

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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