Tracing neuronal tracts in the olfactory pathway of rat and detecting ischemic core in a rat model of focal ischemia using manganese enhanced magnetic resonance imaging

Manganese enhanced magnetic resonance imaging (MRI) is a novel neuroimaging technique that can be usedin vivo to trace neuronal tract and to study brain functions dynamically. In this study, manganese enhanced MRI was used to trace the neuronal tracts between the laminar structures of the olfactory bulb (OB) in rat and to study the so-called “calcium overload” phenomenon in a rat model of cerebral ischemia. High spatial resolution images of the OB were obtained and used to measure the transportation rate of Mn²⁺ among the laminar structures of the OB, which was shown to be approximately 0.2 mm/h under resting condition. In the rat focal ischemia study, it was found that the total area of brain regions with Mn²⁺ accumulation (representing brain regions with calcium overload) was only 55%±15% of the area of the ischemic brain regions shown by diffusion-weighted imaging (DWI). Manganese enhanced MRI might be more accurate than DWI in detecting the ischemic core at the early stage of experimental cerebral ischemia.