Abstract WP227: Magnetic Resonance Measurement Of Static Global And Regional Cerebral Autoregulation

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Souvik Sen ◽  
Hongyu An ◽  
Jonathan Oakes ◽  
Prema Menezes ◽  
Weili Lin ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Cerebral Autoregulation ◽  
Spin Echo ◽  
Oxygen Extraction Fraction ◽  
Oxygen Extraction ◽  
Medical Systems ◽  
Planar Imaging ◽  
Extraction Fraction ◽  
Before And After ◽  
Significant Change

Background: Reliable methods used to test static cerebral autoregulation are time-consuming and/or invasive. Objectives: To evaluate if noninvasive magnetic resonance measured oxygen extraction fraction (OEF), cerebral blood flow (CBF), and oxygen metabolic index (OMI=CBF×OEF) can consistently detect expected physiological changes in humans under normal and 10-15% lowered mean arterial pressure (MAP). Methods: Static cerebral autoregulation was determined by measuring changes in CBF using a pseudo continuous arterial spin labeling (pCASL) approach and Oxygen Extraction Fraction (OEF) using MRI T2‘-weighted asymmetric spin echo echo-planar imaging (EPI) sequences, in response to 10-15% reductions in MAP in stroke-free controls induced by using IV Nicardipine. Images were acquired in 3T MR scanner (Trio, Siemens Medical Systems Inc). Autoregulation was measured globally and regionally in the anterior (ACA), the middle (MCA) and the posterior cerebral artery (PCA) territories of the brain manually defined using autopsy based model. Autoregulatory Index (AI) was computed (AI = %CBF change/% MAP change) supplemented by CBF associated OEF changes. Baseline regional CBF and OEF, AI, CBF and OEF changes to 10-15% lowering of MAP Results: Nineteen normal volunteers (mean age 30, 95% male, 50% white, 40% black, 10% others) were consented to the protocol approved by the institutional review board. MAP lowering was successfully achieved in all subjects (Mean ± standard deviation of MAP lowering of 12.5 ± 5.6 mm Hg). At a global level this resulted in no significant change between pre-MAP lowering CBF (56.0 ± 8.5 ml/100g/min) and post-MAP lowering CBF (55.9± 8.8 ml/100g/min). This translated to a AI of 0 ± 1.2. The CBF results corroborated with no significant change in OEF and OMI. Baseline regional CBF was higher in the MCA territory (66.1 ± 7.6 ml/100g/min) compared with the ACA territory (52.8 ± 8.6ml/100g/min, p<0.001). The AIs were consistent (ANOVA p=0.15) at regional levels across ACA (-1.5 ± 3.1), MCA(-0.3± 2.1) and PCA (-0.1 ± 1.4) territories. Conclusions: Global and regional static cerebral autoregulation can be measured using MR measurement of CBF, OEF and OMI, before and after 10-15% reductions in MAP in healthy volunteers.

scholarly journals Quantifying the changes in oxygen extraction fraction and cerebral activity caused by caffeine and acetazolamide

2016 ◽  
Vol 37 (3) ◽  
pp. 825-836 ◽  
Author(s):  
Sagar Buch ◽  
Yongquan Ye ◽  
E Mark Haacke
Keyword(s):  
Oxygen Saturation ◽  
A Priori ◽  
Susceptibility Mapping ◽  
Oxygen Extraction Fraction ◽  
Oxygen Extraction ◽  
Cerebral Veins ◽  
Blood Oxygen Saturation ◽  
Vascular Reserve ◽  
Extraction Fraction ◽  
Before And After

A quantitative estimate of cerebral blood oxygen saturation is of critical importance in the investigation of cerebrovascular disease. We aimed to measure the change in venous oxygen saturation (Yv) before and after the intake of the vaso-dynamic agents caffeine and acetazolamide with high spatial resolution using susceptibility mapping. Caffeine and acetazolamide were administered on separate days to five healthy volunteers to measure the change in oxygen extraction fraction. The internal streaking artifacts in the susceptibility maps were reduced by giving an initial susceptibility value uniformly to the structure-of-interest, based on a priori information. Using this technique, Yv for normal physiological conditions, post-caffeine and post-acetazolamide was measured inside the internal cerebral veins as YNormal = 69.1 ± 3.3%, YCaffeine = 60.5 ± 2.8%, and YAcet = 79.1 ± 4.0%. This suggests that susceptibility mapping can serve as a sensitive biomarker for measuring reductions in cerebro-vascular reserve through abnormal vascular response. The percentage change in oxygen extraction fraction for caffeine and acetazolamide were found to be +27.0 ± 3.8% and −32.6 ± 2.1%, respectively. Similarly, the relative changes in cerebral blood flow in the presence of caffeine and acetazolamide were found to be −30.3% and + 31.5%, suggesting that the cerebral metabolic rate of oxygen remains stable between normal and challenged brain states for healthy subjects.

scholarly journals Functional oxygen extraction fraction (OEF) imaging with turbo gradient spin echo QUIXOTIC (Turbo QUIXOTIC)

2017 ◽  
Vol 79 (5) ◽  
pp. 2713-2723 ◽  
Author(s):  
Jeffrey N. Stout ◽  
Elfar Adalsteinsson ◽  
Bruce R. Rosen ◽  
Divya S. Bolar
Keyword(s):  
Spin Echo ◽  
Oxygen Extraction Fraction ◽  
Oxygen Extraction ◽  
Extraction Fraction

scholarly journals Uniform distributions of glucose oxidation and oxygen extraction in gray matter of normal human brain: No evidence of regional differences of aerobic glycolysis

2016 ◽  
Vol 36 (5) ◽  
pp. 903-916 ◽  
Author(s):  
Fahmeed Hyder ◽  
Peter Herman ◽  
Christopher J Bailey ◽  
Arne Møller ◽  
Ronen Globinsky ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Oxidative Phosphorylation ◽  
Human Brain ◽  
Gray Matter ◽  
Glucose Oxidation ◽  
Aerobic Glycolysis ◽  
Oxygen Extraction Fraction ◽  
Oxygen Extraction ◽  
Extraction Fraction ◽  
Normal Human

Regionally variable rates of aerobic glycolysis in brain networks identified by resting-state functional magnetic resonance imaging (R-fMRI) imply regionally variable adenosine triphosphate (ATP) regeneration. When regional glucose utilization is not matched to oxygen delivery, affected regions have correspondingly variable rates of ATP and lactate production. We tested the extent to which aerobic glycolysis and oxidative phosphorylation power R-fMRI networks by measuring quantitative differences between the oxygen to glucose index (OGI) and the oxygen extraction fraction (OEF) as measured by positron emission tomography (PET) in normal human brain (resting awake, eyes closed). Regionally uniform and correlated OEF and OGI estimates prevailed, with network values that matched the gray matter means, regardless of size, location, and origin. The spatial agreement between oxygen delivery (OEF≈0.4) and glucose oxidation (OGI ≈ 5.3) suggests that no specific regions have preferentially high aerobic glycolysis and low oxidative phosphorylation rates, with globally optimal maximum ATP turnover rates (VATP ≈ 9.4 µmol/g/min), in good agreement with 31P and 13C magnetic resonance spectroscopy measurements. These results imply that the intrinsic network activity in healthy human brain powers the entire gray matter with ubiquitously high rates of glucose oxidation. Reports of departures from normal brain-wide homogeny of oxygen extraction fraction and oxygen to glucose index may be due to normalization artefacts from relative PET measurements.

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