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.