Validation of a new 3D quantitative BOLD based cerebral oxygen extraction mapping, 2024, Lee et al.

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Validation of a new 3D quantitative BOLD based cerebral oxygen extraction mapping
Hyunyeol Lee; Jing Xu; Maria A Fernandez-Seara; Felix W Wehrli

Quantitative BOLD (qBOLD) MRI allows evaluation of oxidative metabolism of the brain based purely on an endogenous contrast mechanism. The method quantifies deoxygenated blood volume (DBV) and hemoglobin oxygen saturation level of venous blood (Yv ), yielding oxygen extraction fraction (OEF), and along with a separate measurement of cerebral blood flow, cerebral metabolic rate of oxygen (CMRO2 ) maps.

Here, we evaluated our recently reported 3D qBOLD method that rectifies a number of deficiencies in prior qBOLD approaches in terms of repeat reproducibility and sensitivity to hypercapnia on the metabolic parameters, and in comparison to dual-gas calibrated BOLD (cBOLD) MRI for determining resting-state oxygen metabolism.

Results suggested no significant difference between test-retest qBOLD scans in either DBV and OEF. Exposure to hypercapnia yielded group averages of 38 and 28% for OEF and 151 and 146 mmol/min/100 g for CMRO 2 in gray matter at baseline and hypercapnia, respectively. The decrease of OEF during hypercapnia was significant (p ( 0.01), whereas CMRO 2 did not change significantly (p ¼ 0.25). Finally, baseline OEF (37 vs. 39%) and CMRO 2 (153 vs. 145 mmol/min/100 g) in gray matter using qBOLD and dual-gas cBOLD were found to be in good agreement with literature values, and were not significantly different from each other (p > 0.1).

Link | PDF (Journal of Cerebral Blood Flow & Metabolism)

 

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Posting for background for the fMRI findings in Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome (2024, Nature Communications).

From the introduction —

The healthy brain requires about 20% of total oxygen consumed in the body to sustain its normal function. In the cerebrovascular system, both cerebral blood flow (CBF) and oxygen extraction fraction (OEF) are adaptively regulated in close connection to each other to meet local metabolic demands, typically expressed in terms of cerebral metabolic rate of oxygen (CMRO2 ) by Fick’s principle:

The three parameters CBF, OEF, and CMRO2, play a pivotal role in understanding brain oxygen metabolism.

 

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Two representative MRI techniques among the few that enable OEF mapping are calibrated BOLD (cBOLD) and quantitative BOLD (qBOLD). As the names suggest, parameters giving rise to BOLD signal, i.e., deoxyhemoglobin concentration ([dHb]) and deoxygenated blood volume (DBV), are either “calibrated” or “quantified”.

In cBOLD, the calibration constant ‘M’, which represents a maximally attainable BOLD signal change, is first determined using hypercapnic or hyperoxic gas breathing challenges, and thereafter, relative changes of OEF and CMRO2 in response to neural stimulation are obtained from a separate data acquisition.

Recent advances in the method by means of dual-gas calibration (hereafter referred to as “dualgas cBOLD”) enable resting-state OEF and CMRO2 mapping in absolute physiologic units.

Nevertheless, cBOLD methods have been limited in clinical applications due to complex experimental settings for gas administration and potential subject discomfort therefrom. Additionally, in this class of methods arterial spin-labeling (ASL)-based CBF measurements (in lieu of DBV quantification that is yet more challenging) must be conducted in order to derive OEF from the signal model.

Alternatively, qBOLD is a calibration-free technique, yielding resting-state OEF maps without external stimuli or CBF information. [...] A recent technique (termed “qBOLD + QSM”) combining qBOLD with quantitative susceptibility mapping (QSM) sought to address these issues.

In this work, we aimed to validate the new qBOLD method by performing repeatability tests on resting-state OEF, by evaluating its sensitivity to a hypercapnic stimulus inducing changes in brain’s hemodynamic and metabolic status, and by comparing with the existing dual-gas cBOLD technique enabling baseline OEF and CMRO2 mapping. Hereafter, baseline refers to the resting state of the brain with normoxic/normocapnic air.

Concluding —

while average values of qBOLD- and dual-gas cBOLD-based estimates of baseline OEF and CMRO 2 were in good agreement with each other, the present qBOLD method yielded lower intra-subject variability than dual-gas cBOLD, suggesting its promise for a cost-efficient and patient-friendly alternative for evaluation of cerebral oxygen metabolism.

 

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See also —

Cerebral OEF quantification: A comparison study between quantitative susceptibility mapping and dual-gas calibrated BOLD imaging (2020, Magnetic Resonance in Medicine)

BOLD signal physiology: Models and applications (2019, NeuroImage)

Calibrated fMRI for mapping absolute CMRO2: Practicalities and prospects (2019, NeuroImage)

Cerebral metabolic rate of oxygen CMRO2 mapping with hyperventilation challenge using quantitative susceptibility mapping QSM (2017, Magnetic Resonance in Medicine)