Quantification of regional CMRO2 in human brain using dynamic 17O-MRI at 3T

Abstract

ObjectiveTo investigate the feasibility of cerebral metabolic rate of oxygen consumption (CMRO2) measurements with MRI at 3 Tesla in different brain regions. MethodsCMRO2 represents a key indicator of the physiological state of brain tissue. Dynamic 17O-MRI with inhalation of isotopically enriched 17O gas has been used to quantify global CMRO2 in brain white (WM) and gray matter (GM). However, global CMRO2 can only reflect the overall oxygen metabolism of the brain and cannot provide enough information on local tissue oxygen metabolism. To investigate the feasibility of determination of regional CMRO2 at a clinical 3 T MRI system, CMRO2 values in frontal, parietal and occipital WM and GM were determined in 5 healthy volunteers and compared to evaluate the regional differences of oxygen metabolism in WM and GM. Additionally, regional CMRO2 values were determined in deep brain structures including thalamus, dorsal striatum, caudate nucleus and insula cortex and in the cerebella, and compared with literature values from 15O-PET studies. ResultsIn cortical GM the determined CMRO2 values were in good agreement with the literature, whereas values in WM were about 32–48% higher than literature values. Regional analysis revealed a significantly higher CMRO2 in the occipital GM compared to the frontal and parietal GM. By contrast, no significant difference of CMRO2 was observed across the WM. In addition, CMRO2 in deep brain structures was lower compared to literature values and in the cerebella a good hemispheric symmetry of the tissue oxygen metabolism was found. ConclusionDynamic 17O-MRI enables direct, non-invasive determination of regional CMRO2 in brain structures in healthy volunteers at 3T.