Brain oxygen extraction fraction mapping is feasible in multiple sclerosis (MS), according to a new study that appeared in the Journal of Cerebral Blood Flow & Metabolism. It can detect within-lesion differences between the rim and core regions of the lesions as well as differences between MS patients and healthy controls. It could therefore be a useful quantitative marker for MS progression and treatment.
Recently, research identified a new type of MS lesion called chronic active lesions. These lesions are characterized by low-grade sustained microglial activity and expanding demyelination at the rim, and they are associated with increased tissue damage, neuroinflammation, and disability. Magnetic resonance imaging (MRI), which is the standard technique to diagnose MS and monitor disease progression, is not sensitive enough to detect this type of lesion.
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In the present study, a team of researchers from Cornell University in Ithaca, NY aimed to demonstrate the feasibility of whole-brain mapping of oxygen extraction fraction in patients with MS. To do so, they computed oxygen extraction fraction and neural tissue susceptibility maps in 22 MS patients and 11 healthy controls.
They identified 80 chronic active lesions with a hyperintense rim on quantitative susceptibility mapping in patients with MS. They compared the mean oxygen extraction fraction and neural tissue susceptibility within the rim and core of the lesions.
They found that the rim of the lesions showed higher oxygen extraction fraction and neural tissue susceptibility than those of the core.
They also found that, in the whole brain, MS patients had lower oxygen extraction fraction and higher neural tissue susceptibility than healthy controls.
“Our feasibility study suggests that [oxygen extraction fraction] may serve as a useful quantitative marker of tissue oxygen utilization in MS,” the authors concluded.
The oxygen extraction fraction is the ratio of blood oxygen that tissue takes from the blood flow to maintain its function and morphological integrity. It reflects the efficiency of oxygen utilization.
Reference
Cho J, Nguyen TD, Huang W, et al. Brain oxygen extraction fraction mapping in patients with multiple sclerosis. J Cereb Blood Flow Metab. Published online September 24, 2021. doi:10.1177/0271678X211048031
