Dr Simon Kennon MB ChB, FRCP, MD Consultant Cardiologist

Chest X-Ray

A chest X-ray is a painless, noninvasive test that creates pictures of the structures inside your chest, such as your heart, lungs, and blood vessels.

This test is done to find the cause of symptoms such as shortness of breath, chest pain, chronic cough (a cough that lasts a long time), and fever.

How do x-rays work?

An X-ray machine is essentially a camera. Instead of visible light, however, it uses X-rays to expose the film. X-rays are like light in that they are electromagnetic waves, but they are more energetic so they can penetrate many materials to varying degrees.

When the X-rays hit the film, they expose it just as light would. Since bone, fat, muscle, tumors and other masses all absorb X-rays at different levels, the image on the film lets you see different (distinct) structures inside the body because of the different levels of exposure on the film.

Your ribs and spine, which are bony, absorb radiation well and normally appear light on a chest X-ray. However, your lungs, which are filled with air, normally appear dark. A disease in the chest that changes how radiation is absorbed will also appear on a chest X-ray.

When are chest X-rays used?

Chest X-rays help doctors diagnose heart failure (although they are also commonly used to diagnoes pneumonia and other lung conditions.

An X-ray image of your chest allows your doctor to check the size of your heart and its blood vessels and to look for any fluid in your lungs.

If a person is short of breath, this can be a sign of heart failure in which fluid builds up on the lungs and the increase in density in the lungs can show up on the X-ray.

Doctors also may use chest X-rays to see how well treatments for certain conditions are working. Also, doctors often use chest X-rays before surgery to look at the structures in the chest.


Chest X-rays have few risks. The amount of radiation used in a chest X-ray is very small, similar to the amount of radiation you're naturally exposed to over 10 days.