Electron tomography offers a powerful tool to obtain three-dimensional (3-D) structural information in biology and materials science. A set of 2-D projections of an object recorded at different tilt angles is used for calculating the 3-D reconstruction. This 3-D data volume can be computed either by Fourier or real-space back-projection methods.

For information about our Tomography Package click here...
Sample Images and Movies...

• Cellular tomography: imaging the interior of whole cells
• Molecular tomography: structural information of supramolecular complexes
• Cytochemistry: 3-D localisation of gold labels
• Materials science. catalyst particles, nano tubes
• Semiconductor research: contact holes, interconnect line

For a typical 3-D reconstruction, 70 or more projections (depending on the desired resolution) have to be recorded. In principle, these projections can be successively collected by tilting the specimen followed by image recording. Due to mechanical imperfections of the goniometer, the tilt axis is not perfectly stable. Moreover, a specimen which is not adjusted exactly to the eucentric z-position or a tilt axis which is not well aligned to the optical axis causes movements of the object when the specimen is tilted. As illustrated in the figure, this results in

• image displacements up to several µm
• focus changes in the same order of magnitude.

In practice, these effects, even enforced by specimen drift, require several operations such as recentering and refocusing after each tilt increment, particularly at higher tilt angles (>30°). A manual correction can be very time-consuming and - in case of beam-sensitive specimen - almost impossible.

Here you can find a list of introductory publications.
The following links refer to other 3D-EM pages (no claim for completeness):

• 3D-EM homepage: link collection, labs, image processing, mailing list, ...
• Homepage 3-D Electron Microscopy at Utrecht University
• Animated introduction to automatic electron tomography (from 3DEM at Utrecht University)
• Boulder Laboratory for 3-Dimensional Fine Structure
• Max-Planck-Institute for Biochemistry, Dept. of Molecular Structural Biology
• National Center for Microscopy and Imaging Research at San Diego
• Resource for the Visualization of Biological Complexity at the Wadsworth Center, Albany NY
• This site offers a listing of software available for 2D and 3D image processing.