Investigating hyperoxic effects in the rat brain using quantitative susceptibility mapping based on MRI phase.

Area of Science:

• Neuroimaging
• Biophysics
• Medical Physics

Background:

• Assessing brain oxygenation is crucial for understanding various physiological and pathological conditions.
• Current methods for measuring venous oxygen saturation (SvO2) in the brain have limitations.

Purpose of the Study:

• To evaluate the capability of susceptibility imaging to detect changes in microvenous oxygen saturation induced by hyperoxia in the rat brain.
• To compare quantitative susceptibility mapping (QSM) with conventional methods for estimating oxygen saturation changes.

Main Methods:

• T2*-weighted images were acquired using a 3D gradient-echo sequence during normoxia and hyperoxia in rat brains.
• Quantitative susceptibility mapping (QSM) and microvenous oxygenation venography were computed from gradient-echo phase images.
• Venous oxygen saturation (SvO2) estimated by QSM was compared with pulse oxygen saturation (SpO2) and changes derived from ΔR2* maps.

Main Results:

• QSM quantified susceptibility in venous and tissue regions, revealing a nearly 10% reduction in venous susceptibility during hyperoxia.
• An SvO2 shift of 10% was observed during hyperoxia, consistent with increased cortical oxygenation confirmed by SpO2 measurements.
• The change in SvO2 estimated by QSM correlated well with changes derived from ΔR2* maps.

Conclusions:

• Quantitative susceptibility mapping is a promising technique for measuring SvO2 in the brain.
• This method offers potential for quantitative analysis in oxygenation-dependent functional MRI studies.