Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Schematic anterior-posterior (AP) (a) and posterior-anterior (PA) (b) projections: D is the center of X-ray tube; I is the system’s iso-center; P is the projection center; O is the projection center defined by AP projection; DC is the source to detector distance (SDD) and DI is the source to iso-center distance (SID).
