Serial block-face scanning electron microscopy

Applications

One of the first applications of serial block-face scanning electron microscopy was to analyze the connectivity of axons in the brain. The resolution is sufficient to trace even the thinnest axons and to identify synapses. By now, serial block face imaging contributed to many fields, like developmental biology, plant biology, cancer research, studying neuro-degenerative diseases etc. The technique can generate extremely large data sets, and development of algorithms for automatic segmentation of the very large data sets generated is still a challenge. However much work is being done on this area currently. The EyeWire project harnesses human computation in a game to trace neurons through images of a volume of retina obtained using serial block-face scanning electron microscopy.

Many different samples can be prepared for serial block-face scanning electron microscopy and the ultramicrotome is able to cut many materials, therefore this technique has wider applicability. It is starting to find applications in many other areas ranging from cell and developmental biology to materials science.

Advantages and disadvantages

A disadvantage encountered with the SBEM method is that the thickness of the slice which can be removed with the ultra-microtome is limited (~25 nm), thus the resolution in the depth direction is limited. An advantage of the SBEM technique is that the specimen is stationary what improves the alignment in the stacks of images. Another advantage of the SBEM technique is the ability to acquire large data sets with a high level of detail. Because cutting by the ultra-microtome is extremely fast (comparing to the milling process in FIB-SEM), it can expose a wide area of the material (x and y directions) every sectioning. Additionally, by fast cutting, we can acquire many images in z-direction in a short period of time.

References

References

1. (2004). "Serial Block-Face Scanning Electron Microscopy to Reconstruct Three-Dimensional Tissue Nanostructure". PLOS Biol.
2. (2016-07-09). "Analysis of Brain Mitochondria Using Serial Block-Face Scanning Electron Microscopy". Journal of Visualized Experiments.
3. (2015-08-03). "Large-volume en-bloc staining for electron microscopy-based connectomics". Nature Communications.
4. "3View System for Image Capture of 3D Ultrastructures | Gatan, Inc".
5. (2017-10-02). "Teneo VolumeScope SEM for Life Sciences".
6. "Katana microtome".
7. "Challenge << EyeWire".
8. Holland, Nicholas. (June 21, 2018). "Formation of the initial kidney and mouth opening in larval amphioxus studied with serial blockface scanning electron microscopy (SBSEM)". Evodevo.