How Does a Lung X-ray Work?

A lung X-ray, also known as a chest X-ray, is a very common radiology test that uses a small amount of radiation to produce an image of the internal structures within the chest, including the heart, lungs, blood vessels and bones.[1]

How X-rays Work

lung x-ray, chest x-ray, lung x ray, chest x ray, lung xray, chest xrayOnce aimed at the body part being studied, X-rays work by producing a focused beam of radiation that passes through the body, recording the image on special film or a computer. Because body tissues vary in density (thickness), different parts of the body absorb the X-ray in varying degrees. For example, bone, which is very dense, absorbs a large amount of radiation and appears white on an X-ray. Soft tissues, such as muscle, fat and various organs, allow much of the radiation to pass through them and appear in varying shades of gray on the image, while air on an X-ray shows up as black. On a lung X-ray, your ribs and spine absorb a great deal of radiation and appear white or light gray, while the lungs, which are filled with air, allow more of the radiation to pass through and appear in darker shades of gray on the image.[2]

Common Reasons for a Lung X-ray

A lung X-ray is usually the very first diagnostic test your doctor will order if you have:2

In addition, many health care providers use lung X-rays to help diagnose or monitor treatment for illnesses such as:2

Are There Any Risks?

Because the amount of radiation used during a lung X-ray is very small, they are generally considered safe and unlikely to cause any side effects. Those at greater risk for tissue damage from an X-ray include young children and unborn fetuses.1

Note: even though X-rays are considered safe, you’ll still be asked to wear a protective apron made of lead if more than one image is being taken.[3]

What to Expect During the Procedure

Having a chest X-ray is usually painless; you should feel nothing as the radiation passes through your body. A radiology technician will conduct your X-ray. During the test, the technician will position your body between the X-ray machine and a plate that produces a digital or film image. Sometimes, your doctor will order more than one view of your chest and the technician may ask that you move your body in different positions so that the machine can capture images of both the front and side views of your chest.3

For the front view, you’ll stand facing the plate with your arms up or to the sides and your shoulders rotated forward. Sometimes, you’ll be asked to hold your breath for several seconds while the technician captures the image. This is done to reduce blur so your doctor can see your heart and lungs more clearly on the X-ray.3

During the side view, you’ll turn to the side placing your shoulder against the plate with your hands over your head. You’ll most likely be asked to hold your breath again while the technician shoots the image.3

Note: if you have trouble standing during the lung X-ray, ask the technician if you can sit in a chair.


A radiologist trained in the interpretation of X-rays and other imaging studies will read your X-ray, generate a report with your results and forward it to your doctor. During your follow-up appointment, you can discuss your results with your doctor and ask questions, as needed.

For more information about obtaining a lung X-ray, talk to your primary health care provider.

 [1] Cleveland Clinic. Chest XRay. Last reviewed November 10, 2014.

[2] X-ray (Radiography) – Chest. Accessed April 29, 2018.

[3] Mayo Clinic. Chest X-rays. April 26, 2018.


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