What do earthquakes have in common with x-rays?
The vibrations from earthquakes travel through the Earth as energy waves called seismic waves. X-rays are also a type of energy wave. Seismic waves travel through different types of material at slightly different speeds and their changing speeds give us information about that material, such as density and thickness. The x-rays in a CAT scan lose amplitude as they go through the dense layers of tissue and the data stream representing the varying x-ray intensity is used to generate and image.