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Volume 29, Number 3, February 2017
Further reading
How does electron tomography
work?
Liz Sheffield and Louise Hughes
First let’s consider tomographic reconstruction. This is used to generate three-dimensional images
from two-dimensional components. You may have heard of CT (or CAT) scans. The computer
tomography machine takes X-ray images of the body from different angles, so gives a series of cross
sectional images (like taking slices) through the part of the body being scanned. These are combined
into a three-dimensional reconstruction.
CT scanner,
courtesy Epstock/Fotolia
Read more about the technique, and some of the ways it can be used to diagnose medical problems,
on the Cancer Research UK website with a video of a scan being done, at: http://tinyurl.com/j5yrygz
Electron tomography (ET) is a similar technique based on beams of electrons. It is an extension of the
technique of transmission electron microscopy, which passes a beam of electrons through a sample.
In ET the electron beam is passed through the sample, which is tilted incrementally around the centre
of the target area — again generating a series of cross-sectional images. All of the images are fed into
a computer, which ‘back-projects’ them to create a three-dimensional model, such as that shown on
page 20 of the February issue. The images below show how this is done and you can see a movie
showing how the technique can be used to generate three-dimensional models using a 3D printer
here: http://tinyurl.com/z5hshqm
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www.hoddereducation.co.uk/biologicalsciencesreview
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This resource is part of BIOLOGICAL SCIENCES REVIEW , a magazine written for A-level students by subject experts.
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www.hoddereducation.co.uk/biologicalsciencesreview