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

To investigate the feasibility of cerebral metabolic rate of oxygen consumption (CMRO₂) measurements with MRI at 3 Tesla in different brain regions.

CMRO₂ 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.

In 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.

Dynamic ¹⁷O-MRI enables direct, non-invasive determination of regional CMRO₂ in brain structures in healthy volunteers at 3T.