Abstract
To test whether susceptibility imaging can detect microvenous oxygen saturation changes, induced by hyperoxia, in the rat brain. A three-dimensional gradient-echo with a flow compensation sequence was used to acquire T2*-weighted images of rat brains during hyperoxia and normoxia. Quantitative susceptibility mapping (QSM) and QSM-based microvenous oxygenation venography were computed from gradient-echo (GRE) phase images and compared between the two conditions. Pulse oxygen saturation (SpO2 ) in the cortex was examined and compared with venous oxygen saturation (SvO2 ) estimated by QSM. Oxygen saturation change calculated by a conventional Δ R2* map was also compared with the ΔSvO2 estimated by QSM. Susceptibilities of five venous and tissue regions were quantified separately by QSM. Venous susceptibility was reduced by nearly 10%, with an SvO2 shift of 10% during hyperoxia. A hyperoxic effect, confirmed by SpO2 measurement, resulted in an SvO2 increase in the cortex. The ΔSvO2 between hyperoxia and normoxia was consistent with what was estimated by the Δ R2* map in five regions. These findings suggest that a quantitative susceptibility map is a promising technique for SvO2 measurement. This method may be useful for quantitatively investigating oxygenation-dependent functional MRI studies. Magn Reson Med 77:592-602, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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