Tomography

Tomography is a way to visualize parts of a fossil through images that are slices through the specimen. These 2-D slices can be physically cut through the specimen or by using advanced imaging techniques (Sutton et al. 2014). We will refer to an individual slice as a tomogram and a complete data series as a tomographic dataset, following Sutton et al. (2014). These 2-D slices can be used to examine the interior of organisms (including you) and create 3-D reconstructions of the object/organism.

Three tomograms through a generalized diagram of a snail. The three slices are then able to be presented as slices (bottom) through the shell. Modified from Sutton (2008) and Sutton et al. (2014).

There are two primary ways to obtain tomographs: (1) destructive techniques and (2) non-destructive techniques. Destructive techniques are just as they sound, destructive! This involves destroying the specimen while you are making tomographs. One of the traditional methods is to create acetate peels of fossil specimens. To learn more about acetate peels, including how to make them, click here! Non-destructive techniques have made a rise with advances in technology. These include medical imaging machines such as MRI (Magnetic Resonance Imaging) and CT scans.

There are many forms of tomography but the main goal of this page is to prepare you with knowledge to read a paper or article and understand the terminology. Computed tomography (CT) is a tomographic technique that relies on computational programs to aid in the analysis of your data. CT scans that you get at the doctor are using X-rays to image inside your body. But to be clear, X-rays are not the only source of imaging via computed tomography. It is definitely the most well-known!

See below for details!

The above image is of a blastoid with sections of the specimen placed below it. These are acetate peels of a different specimen that was destroyed while they were made. The sections are taken at different locations on the specimen. Often, the section is completely sectioned from top to bottom! That results in a ton of peels! You can see the progression in the peels – number 3 has a much larger jumbled dark circle in the middle whereas number 1 has a very tiny dark circle in the middle.

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