High-resolution MEMRI characterizes laminar specific ascending and descending spinal cord pathways in rats

Background: The spinal cord is composed of nine distinct cellular laminae that currently can only be visualized by histological methods. Developing imaging methods that can visualize laminar architecture in-vivo is of significant interest. Manganese enhanced magnetic resonance imaging (MEMRI) yields valuable architectural and functional information about the brain and has great potential in characterizing neural pathways in the spinal cord. Here we apply MEMRI to visualize laminae architecture in the thoracic region of the spinal cord with ultrahigh resolution. New Method: Manganese chloride (MnCl2) was delivered systemically and imaging of the lumbar and thoracic spinal cord levels was acquired in high field, 11.7 T MRI scanner, 48 h following MnCl2 administration. Results: Here we demonstrate laminar specific signal enhancement in the spinal cord of rats administered with MnCl2 with 69 mu m in-plane resolution. We also report reduced T1 values over time in MnCl2 groups across laminae I-IX. Comparisons with existing methods: This is the first study to demonstrate that MEMRI is capable of identifying spinal laminae at a high resolution of 69 mu m in a living animal. This would enable the visualization of architecture and function of distinct regions with improved resolution, in healthy and diseased animal models. Conclusions: The regions with the largest T1 enhancements were observed to correspond to laminae that contain either high cell density or large motor neurons, making MEMRI an excellent tool for studying spinal cord architecture, physiology and function in different animal models.