What is electron tomography?
Electron tomography is an imaging technique that uses a transmission electron microscope (TEM) to obtain three-dimensional (3D) images of nano-scale objects. It overcomes the limited resolution of light microscopes by using electrons instead of photons as the imaging probe. The high resolution and large depth of field of TEMs make them ideally suited for this purpose.
How does it work?
Conventional TEMs produce two-dimensional (2D) images of specimens by passing a beam of electrons through them and detecting the resulting pattern of scattered electrons on a fluorescent screen or digital detector. In electron tomography, the specimen is tilted in successive steps while being imaged at each angle, so that a series of 2D projection images is acquired. These projection images are then computationally reconstructed to yield a 3D image. This process is analogous to X-ray computed tomography (CT), which produces 3D images from X-ray projections acquired at different angles around the subject. However, whereas CT uses X-rays, which have relatively low energy and long wavelength, electron tomography employs high-energy electrons with much shorter wavelength. This enables it to achieve far higher resolutions than CT—on the order of nanometers rather than micrometers.
Applications
One key application of electron tomography is in structural biology, where it can be used to determine the 3D structure of proteins and other biomolecules at near atomic resolution. It has also been used in materials science to study the microstructure of metals, alloys, ceramics, semiconductors, and other materials; and in nanotechnology for characterizing nano-scale devices and structures.