Mitigation of artifacts in imaging biosamples with optical scanning transmission electron microscopy

Electron microscopy (EM) allows ultrastructural analysis of biological tissues and cells, but images frequently contain artifacts because biological samples have to undergo rigorous preparation to be resistant to vacuum conditions and electron beam exposure. Knowledge about the appearance of image artifacts and how they arise is crucial for their recognition and mitigation and for proper image interpretation. How artifacts appear depends strongly on the electron detection modality and the imaging conditions. Optical scanning transmission EM (OSTEM) is a detection technique compatible with single-beam and multibeam electron microscopes, in which tissue samples are directly deposited on a scintillator for imaging in transmission mode. Here, we identified several types of artifacts that may occur in single-beam and multibeam OSTEM. These artifacts arise or appear as a result of combining established sample preparation protocols with solid scintillator substrates and optical transmission detection. Artifacts can be effectively mitigated or minimized to ultimately enable high quality large-scale 2D and 3D acquisitions.