Section II. POSITIONING AND PROJECTION TERMINOLOGY
The process of recording a body part on an image receptor (film) is referred to as
projection. The projection describes the path of the central ray (CR) from the X-ray tube
through the patient to the image receptor.
projection: process of recording a body part on an image receptor (film); path of
central ray from the X-ray tube to film
Here, the terms posterior and anterior (posteroanterior (PA)) are combined to describe
the protection or direction in which the X-ray beam travels. In a PA projection, the X-ray beam
enters a posterior surface and exits an anterior surface (figure 3-23). As stated earlier, in a PA
projection the height of the film is superior to inferior and the width is lateral to lateral.
Figure 3-23. In this PA projection of the chest, the CR enters a posterior surface and
exits an anterior surface.
The two terms, anterior and posterior are combined here to describe the direction
of travel of the X-ray beam entering an anterior surface and exiting a posterior surface