a system for portraying data obtained by a radiographic camera , such as an anger camera , which signals the occurrences of radioactive events and the addresses of locations of the events . data is obtained from a reference subject and a living subject . the activity of events of the reference subject is stored as a function of event location and is utilized as scale factors for scaling the relative energies of event signals obtained from the living subject , whereby data of the living subject is normalized relative to the reference subject .