Longitudinal 19F magnetic resonance imaging of brain oxygenation in a mouse model of vascular cognitive impairment using a cryogenic radiofrequency coil.

Introduction: We explored the use of a perfluoro-15-crown-5 ether nanoemulsion (PFC) for measuring tissue oxygenation using a mouse model of vascular cognitive impairment.
Methods: Seventeen C57BL/6 mice underwent stereotactic injection of PFC coupled to a fluorophore into the striatum and corpus callosum. Combined 1H/19F magnetic resonance imaging (MRI) to localize the PFC and R ₁ mapping to assess pO ₂ were performed. The effect of gas challenges on measured R ₁ was investigated. All mice then underwent bilateral implantation of microcoils around the common carotid arteries to induce global cerebral hypoperfusion. 19F-MRI and R ₁ mapping were performed 1 day, 1 week, and 4 weeks after microcoil implantation. In vivo R ₁ values were converted to pO ₂ through in vitro calibration. Tissue reaction to the PFC was assessed through ex vivo immunohistochemistry of microglial infiltration.
Results: R ₁ increased with increasing oxygen concentrations both in vitro and in vivo and the strength of the 19F signal remained largely stable over 4 weeks. In the two mice that received all four scans, tissue pO ₂ decreased after microcoil implantation and recovered 4 weeks later. We observed infiltration of the PFC deposits by microglia.
Discussion: Despite remaining technical challenges, intracerebrally injected PFC is suitable for monitoring brain oxygenation in vivo.