Work

Magnetic resonance imaging metrics of oxygen extraction fraction: Contradictions or insight into pathophysiological mechanisms?

Year: 2022

Type: article

Abstract: In this issue of the American Journal of Hematology, Fields et al. report cerebral oxygen extraction fraction (OEF) measurements using an Asymmetric Spin Echo Magnetic Resonance Imaging (ASE-MRI) technique for a large cohort (N = 120) of children including healthy controls (34), anemic controls without sickle cell disease (27), and those with sickle cell anemia (SCA) (59). 1 They found that average OEF in anemic controls was significantly higher than in healthy controls, and that OEF is higher still in SCA.In addition, they found that the volume of brain with elevated OEF was larger for SCA than for anemic controls.In both cohorts, the largest OEF increases were in the white matter and included regions where infarcts were identified by fluid-attenuated inversion recovery (FLAIR) MRI.The observations of increased OEF by Fields et al. in SCA contradict the decreased OEF recently reported by Vu et al.Vu et al. used T2-relaxation under spin tagging MRI (TRUST-MRI) to measure OEF in a large cohort (N = 118) of young adults including healthy controls (44), anemic controls (27), and individuals with SCA (47). 2 This study also found that OEF in anemic controls differed from healthy controls and SCA had even larger OEF differences, however, the differences were in the opposite direction with SCA having the lowest OEF.This discrepancy could lead readers to dismiss both methods, not knowing which is correct, but once the details of each measurement technique are considered a reconciliation between these opposite observations is possible.All MRI-based techniques for quantifying OEF rely on the different magnetic properties of oxy-and deoxy-hemoglobin.There are two main families of techniques that quantify cerebral OEF, those that provide estimates of OEF on a voxelwise basis from signals that arise from the local tissue, and those that quantify whole-brain OEF by observing large draining veins most often the superior sagittal sinus (SSS).3 The techniques from the contradictory papers come from these two different families.

Source: American Journal of Hematology

DOI: 10.1002/ajh.26567

Authors: Jeffrey N. Stout, Pei‐Yi Lin, Jason Sutin, John Higgins, P. Ellen Grant

Institutions: Boston Children's Hospital, Harvard University, Massachusetts General Hospital, Center for Systems Biology

Language: English

Topic: Advanced MRI Techniques and Applications

Subfield: Radiology, Nuclear Medicine and Imaging

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: green