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PURPOSE: To quantitatively map cerebral metabolic rate of oxygen ( CMRO2) and oxygen extraction fraction ( OEF) in human brains using quantitative susceptibility mapping (QSM) and arterial spin labeling-measured cerebral blood flow (CBF) before and after caffeine vasoconstriction. METHODS: Using the multiecho, three-dimensional gradient echo sequence and an oral bolus of 200 mg caffeine, whole brain CMRO2 and OEF were mapped at 3-mm isotropic resolution on 13 healthy subjects. The QSM-based CMRO2 was compared with an R2*-based CMRO2 to analyze the regional consistency within cortical gray matter (CGM) with the scaling in the R2* method set to provide same total CMRO2 as the QSM method for each subject. RESULTS: Compared to precaffeine, susceptibility increased (5.1 ± 1.1 ppb; P 0.05), but quantitation of R2*-based CMRO2 required an additional scaling factor. CONCLUSION: QSM can be used with perfusion measurements pre- and postcaffeine vascoconstriction to map CMRO2 and OEF.
Zhang et al. (Fri,) studied this question.
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