Computerized Tomography

This method is also refered to as CAT, short for computer assisted tomography. The CT, or CAT, scan is a natural progression from x-rays. The method is based on the principle that a three-dimensional object can be reconstructed from its two dimensional projections. The mathematics are based on the Radon transform which is a map from an n-dimensional space to an (n-1)-dimensional space. A scan involves taking x-ray pictures from various angles and then combining them together to reconstruct the three-dimensional structures in the body.

Because the final CT image is reconstructed by a computer, it is already in digital form and can be analyzed quantitatively. In addition, it is far easier to separate tissues other than bone from one another, as compared to a simple x-ray scan, because significantly more data is collected. Reconstruction algorithms exist to take advantage of the subtle differences between tissue absorption coefficients and allow demarcation of various structures in the body.

CT imaging is superior to single x-ray scans, but still suffers from the fact that soft tissue x-ray absorption is relatively similar. Although more information is available by applying reconstruction algorithms to the data, for a detailed imaging of anatomy the MRI scan is used.