The Janus project: the remaking of nuclear medicine and radiology.

In ancient Roman religion and mythology, Janus is the god of beginnings and transitions. He is depicted as having 2 faces on his head, facing opposite directions: one face looks eastward and the other westward, looking simultaneously into the future and the past. He also symbolizes change and transitions such as the progression of one condition to another, of one vision to another (Fig. 1) (1,2).