Chest X-Ray

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Medical Author:

Siamak T. Nabili, MD, MPH

Siamak T. Nabili, MD, MPH

Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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What is a chest X-ray?

A chest X-ray is a radiology test that involves exposing the chest briefly to radiation to produce an image of the chest and the internal organs of the chest. An X-ray film is positioned against the body opposite the camera, which sends out a very small dose of a radiation beam. As the radiation penetrates the body, it is absorbed in varying amounts by different body tissues depending on the tissue's composition of air, water, blood, bone, or muscle. Bones, for example, absorb much of the X-ray radiation while lung tissue (which is filled with mostly air) absorbs very little, allowing most of the X-ray beam to pass through the lung.

What is a shadow on a chest X-ray?

Due to the differences in their composition (and, therefore, varying degrees of penetration of the X-ray beam), the lungs, heart, aorta, and bones of the chest each can be distinctly visualized on the chest X-ray. The X-ray film records these differences to produce an image of body tissue structures and these are shadows seen on the X-ray. The white shadows on chest X-ray represent more dense or solid tissues, such as bone or heart, and the darker shadows on the chest X-ray represent air filled tissues, such as lungs.

How is the chest X-ray procedure performed?

Patients obtaining a chest X-ray will often be requested to use an X-ray gown, and extra metallic objects such as jewelry are removed from the chest and/or neck areas. These objects can block X-ray penetration, making the result less accurate. Patients may be asked to take a deep breath and hold it during the chest X-ray in order to inflate the lungs to their maximum, which increases the visibility of different tissues within the chest.

The chest X-ray procedure often involves a view from the back to the front of the body as well as a view from the side. The view from the side is called a lateral chest X-ray. Occasionally, different angles are added in order for the radiologist to interpret certain specific areas of the chest.

The radiology technologist or technician is a trained, certified assistant to the radiologist who will help the patient during the X-ray and actually perform the X-ray test procedure. After the chest X-ray is taken and recorded on the X-ray film, the film is placed into a developing machine, and this picture (which is essentially a photographic negative) is examined and interpreted by the radiologist.