Towards correlative imaging of neuronal tissue by phase-contrast x-ray tomography and SEM

The mammalian brain shows a complex and hierarchical architecture, whose assessment at all functionally relevant scales requires the establishment of multiomics approaches. In this work, we propose a correlative workflow, which is based on large-scale overview PC-CT scans using the extended beams offered by laboratory μCT sources and parallel beam synchrotron radiation (SR), with subsequent zooms into specific regions-of-interest using cone-beam recordings with nanofocused laboratory sources or SR, and finally SEM in controlled and wellidentified sub-volumes obtained before. We demonstrate the workflow at the example of rOTO-stained murine corpus callosum tissue, a brain region rich in myelinated nerve fibers. Based on two different and complementary techniques, PC-CT and scanning electron microscopy (SEM), we approach the establishment of a correlative imaging workflow. As we show here, the workflow can be applied (i) in a correlative study, in order to add further quantitative value, for instance, or (ii) in a multiscale approach, to which PC-CT can contribute volume throughput, while SEM can contribute resolution. The findings from this work demonstrate the complementary strength of each modality in terms of resolution (FIB-SEM) and FOV or volume throughput (PC-CT).