Quantification of normal cerebral oxygen extraction and oxygen metabolism by phase-based MRI susceptometry: evaluation of repeatability using two different imaging protocols.

Global oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO2 ) were quantified in a test-retest study. Cerebral blood flow (CBF) data, required for CMRO2 estimation, were obtained using dynamic susceptibility contrast MRI (DSC-MRI). OEF and CMRO2 were quantified using two separate data sets, that is, conventional high-resolution (HR) gradient echo (GRE) phase maps as well as echo planar imaging (EPI) phase maps taken from the baseline (precontrast) part of the DSC-MRI time series. The EPI phase data were included to elucidate whether an extra HR-GRE scan is needed to obtain information about OEF and CMRO2 , or if this information can be extracted from the DSC-MRI experiment only.