You might be thinking, “hang on – this activity is called 3D imaging! The simulation in the Explore section demonstrated the effect of the number of projections using a 2D image! What’s going on here?”
The answer is that in order to build a 3D image, we take lots of 2D reconstructions (that we refer to as slices) and stack them on top of each other. This is useful for two reasons. One is that we can look at any slice we choose and analyse the information in it. Secondly, if we want to look at the entire volume, we simply stack the individual slices and look at the entire 3D structure.
Computed tomography of a human brain. The slices represent information that goes from the base of the skull (top left) to the top of the skull (bottom right)
Below you can see similar slice reconstructions. The x-ray data was taken using x-ray tomography equipment at La Trobe University.
Of course, the grid above only shows a small subset of all the slices. For the data shown above, we reconstructed 512 individual slices through the object with each slice representing an extremely thin layer of the object. Below you can watch movies that show the reconstructed slices through the object. Once the slices are reconstructed they are stacked together to form a 3D rendering of the object.
Ball Bearing Slices
Ball Bearing Reconstruction Outer
Ball Bearing Reconstruction Inner
Seashell Reconstruction Outer
Seashell Reconstruction Inner