Like all methods of radiography, chest radiography employs ionizing radiation in the form of x-rays to generate images of the chest. The typical radiation dose to an adult from a chest radiograph is around 0.06 mSv
Different views of the chest can be obtained by changing the relative orientation of the body and the direction of the x-ray beams. The most common views are posteroanterior, anteroposterior, and lateral. In an posteroanterior (PA) view, the x-ray source is positioned so that x-rays enter through the posterior (back) aspect of the chest, and exit out of the anterior (front) aspect where they are detected. To obtain this view, individuals stand facing a flat surface behind which is an x-ray detector. A radiation source is positioned behind the patient at a standard distance, and x-ray beams are transmitted toward the patient.
In anteroposterior (AP) views, the positions of the x-ray source and detector are reversed: x-rays enter through the anterior aspect and exit through the posterior aspect of the chest. AP chest x-rays are harder to interpret than PA x-rays and are therefore generally reserved for situations where it is difficult for the patient to obtain a normal chest x-ray, such as when the patient cannot get out of bed. In this situation, mobile X-ray equipment is used to obtain a lying down chest x-ray (known as a "supine film"). As a result most supine films are also AP.
Lateral views of the chest are obtained in a similar fashion as the posteroanterior views, except in the lateral view, the patient stands with both arms raised and the left side of the chest pressed against a flat surface.