Differences Between AP & PA Projections

In medicine, patient positioning is a fundamental skill. Every medical discipline uses positioning terms to describe their patient's condition and complaints. Medical terminology begins with the body position and builds from this point. Radiology not only uses position terminology but must also physically position their patients to properly perform the testing they need to do. The slightest position misalignment could mean a wrong diagnosis.

Function

• X-rays are a vital diagnostic tool.

  X-rays are short wavelengths of energy that can pass through solid objects. By focusing the beam on a photographic plate, a physician is able to see the internal anatomy of a patient. Patient positioning or view, the direction from which the picture is taken, is the most important factor when taking an x-ray.

Posteroanterior (PA)

• Quite literally, from back to front. The front of the patient is facing away from the X-ray tube and is up against the film plate. This is the most commom view for an X-ray. It gives the physician a clear picture of the internal anatomy without much interference from overlapping internal anatomy. The PA films are usually ordered with lateral, or side, films for comparison.

Anteroposterior (AP)

• The AP view travels from front to back. AP views come from portable X-ray images and X-ray images of joints or any time a physician wants that view. Because of overlapping anatomy, the AP view does not give a clear, sharp image the way the PA view does. When an AP film of a patients trunk is ordered, it is because the physician is looking for something specific.

Types

• Patient positioning and the view used are important for a proper interpretation.

  "AP," "PA," "Lateral," "Right Lateral," "Left Lateral," "Oblique," "Supine" and "Prone" are not only terms to describe the position of a body, they are also the different views used to get the picture the physician needs to see. Body position, and the interpretation thereof, is based on the "Anatomical Man." This fictious being is 67 inches tall, 150 pounds, standing upright, facing straight ahead, feet slightly apart, and palms facing forward. The physician looks at this being the same way they look at a patient - face to face. This is also the way the X-ray is viewed.