Medical imaging technologies such as the CT and MRI create sets of 2D slices. There are various ways to reconstruct these 2D slices into 3D models. Generally each of these slices were taken at a known distance apart. Imaging software can create   a simple 3D structure by placing each of these images that known distance apart in 3D space and thereby create a 3D model out of 2D images. This model can be further analyzed by doing a “volume rendering” in which internal objects with different grey scale values are separated into different 3D components.

The following is an image of a 3D model of the brain and eyeballs created in a free software called OsiriX:

Source for image and information: http://en.wikipedia.org/wiki/3D_scanner

I think this technic is interesting because it represents the internal rather than producing an empty shell of the surface of the object.

I also came across the artist Marlene Oliver  who works almost exclusively in 3D medical imaging technologies.