Many facial animation systems rely on medical data for input to the model. Such information as the shape of the underlying bone structure, the musculature, and a model of the skin are often used in these calculations. Much of this information is available in anatomy books, but if we wish to model a particular individual medical imaging technologies can help.
Determination of bone and other hard tissue 3 dimensional structure is easily accomplished by means of X-ray tomography. (Any use of X-rays or ingestion of nuclear materials, of course, involves some risk.) Soft tissue studies are usually done by means of magnetic resonance imaging (MRI) or positron emission tomography (PET) scans. PET scans typically measure a level of uptake of a material and are used for example to measure activity within the brain. This is likely of limited use for facial animation directly, but may be of interest to those studying facial understanding.