Chest Radiograph

In medicine, a chest radiograph, commonly called a chest x-ray (CXR), is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest radiographs are among the most common films taken, being diagnostic of many conditions.

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


Views
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.