Connectomic Imaging Facility

Electron microscopy (EM) is the only imaging modality that has ever been used to reconstruct a connectome, defined as a complete neuronal wiring diagram of a nervous system or a brain. A mere cubic millimeter of brain tissue amounts to over a petabyte of images at EM resolution, so progress in connectomics continues to depend on massive increases in imaging throughput. PNI is the only site in the world that provides both high-throughput transmission EM and scanning EM. PNI is a key performer in CONNECTS, a transformative project of the US BRAIN Initiative.

Beam deflection transmission electron microscopy

The facility hosts four of the world’s fastest transmission electron microscopes. Each TEM is based on a vintage JEOL 1200EX II that has been hot-rodded with an automated reel-to-reel section feed and beam deflection system (Voxa), and a 50 megapixel camera with integrated scintillator and lens system (AMT). A single TEM is capable of 0.3 gigapixel/sec, even after accounting for imaging overhead. 

Multibeam scanning electron microscopy

The facility has installed a Zeiss MultiSEM 506, which scans 91 beams in parallel to achieve extremely high imaging throughput. Princeton is one of just three sites in the U.S. where the world’s fastest multibeam scanning electron microscope (mSEM) can be found. The mSEM has been integrated with an ion beam etching and milling (IBEAM) device. The IBEAM-mSEM system enables fast and robust iterative imaging of semithin sections.