FIB-SEM Technology

Isotropic high-resolution imaging of large volumes provides unprecedented opportunities to advance connectomics and cell biology research. Conventional Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) offers unique benefits such as high resolution (< 10 nm in x, y, and z), minimal defects, and robust image alignment, well suited for superior tracing of neuronal processes and automated segmentation. However, its prevailing deficiencies in imaging speed and duration cap the maximum possible image volume. We developed innovative solutions to overcome these barriers and transformed FIB-SEM from a conventional lab tool lacking long term reliability to a robust imaging platform capable of years of continuous imaging without defects in the final image stack [Xu et al. 2017; Xu et al. 2020a; Xu et al. 2020b].

These improvements have enabled the extension of the continuous imaged volume by more than four orders of magnitude from 10³ µm³ to at least 10⁷ µm³, while maintaining an isotropic sampling of 8 x 8 x 8 nm³ voxels. Moreover, by trading off imaging speed, the system can readily be operated at even higher resolutions achieving voxel sizes of 4 x 4 x 4 nm³. The expanded volumes enabled by this enhanced FIB-SEM technology 1.0 enable a vast new regime in scientific learning, where nano scale resolution coupled with meso and even macro scale volumes is critical. The largest connectome to date has been generated through this enhanced FIB-SEM platform [Xu et al. 2020c], where the superior z resolution empowers automated tracing of neuronal processes and reduces the time-consuming human proofreading effort. The journey of enhanced FIB-SEM development and Drosophia hemibrain endeavor was featured in Nature & New York Times.