Chest radiograph

A chest radiograph, also called a chest X-ray (CXR) or chest film, is a special picture of the chest that doctors use to find problems in the chest and the things inside it. It is one of the most common tests done in hospitals and doctor’s offices.

This test uses a safe type of energy called ionizing radiation, which makes X-rays. These X-rays pass through the body and create an image that shows what’s inside the chest. For an adult, the amount of radiation from a chest X-ray is very small—about the same as the natural radiation we get from the environment in just ten days. This makes it a helpful tool for doctors to see inside the body without using a lot of radiation.

Medical uses

Chest X-rays are a common way for doctors to look for problems in the chest. They help find issues like infections in the lungs, heart problems, and broken bones. These X-rays can show the lungs, heart, and other important parts inside the chest.

Doctors use chest X-rays to check for many different conditions. They can look at the airways, bones, heart shape, and the space between the lungs to see if anything looks unusual. If they notice something might be wrong, they might do more tests to be sure.

Views

Different views of the chest can be taken by changing how the person stands and where the x-ray beam points. The most common views are posteroanterior (PA), anteroposterior (AP), and lateral. In a PA view, the x-ray beam goes through the back of the chest and comes out the front. The person stands facing a flat surface with an x-ray detector behind it, and the x-ray source is placed behind the person.

In an AP view, the x-ray beam goes through the front of the chest and comes out the back. This view is harder to read and is used when a person cannot stand up, such as when they are in bed. A portable x-ray machine is used for this.

Lateral views are similar to PA views, but the person stands with their left side against a flat surface and both arms raised.

Main article: Projections

Typical views

The needed views can differ by country and hospital, but a standing PA view is usually the first choice. If this cannot be done, an AP view is taken. In the UK, the usual chest x-ray is a standing PA view, with a lateral view only if a radiologist asks for it. In the US, chest x-rays include a PA and lateral view with the person standing or sitting up. Special views, like an AP view taken quickly with a portable device, are used when a person cannot safely stand up. Lateral decubitus views help see air-fluid levels when a person cannot stand up.

Additional views

• Decubitus – taken while the person is lying on their side. This helps tell apart fluid build-up from infections like pneumonia.
• Lordotic view – used to see the top part of the lung, helpful for finding certain growths.
• Expiratory view – helps find air that shouldn’t be in the lungs.
• Oblique view – useful for seeing the ribs and breastbone. The x-ray dose must be adjusted correctly for this view.

Main articles: Pleural effusions, Pancoast tumor, Pneumothorax

Landmarks

In a normal chest X-ray, the diaphragm usually meets the 5th to 7th ribs at a special line called the mid-clavicular line. Usually, you can see 9 to 10 ribs at the back on a normal X-ray. Seeing more ribs might mean the lungs are larger than normal, which can happen with certain lung problems. Seeing fewer ribs might mean the lungs are smaller, which can happen with other lung issues.

Doctors also look at the size of blood vessels and the shape of certain structures to find clues about health problems. They check if parts of the heart or diaphragm look blurry, which can help them figure out where a problem might be.

Abnormalities

A lung nodule is a small, round spot seen in the lungs on an X-ray. It can be caused by different things, such as infections, growths, or problems with blood vessels. Doctors look at how fast it grows, its shape, and where it is to help figure out what it might be.

A cavity is a hollow space inside the lungs. It can be caused by infections, cancer, or problems with blood flow. Doctors check the walls of the cavity and the area around it to help find the cause.

Pleural abnormalities happen when fluid builds up between the lungs and the chest wall. This is called a pleural effusion. The amount of fluid needed to see this on an X-ray can vary. Sometimes, thick lines or shadows on the X-ray can also show problems with the lining around the lungs.

Diffuse shadowing means areas of the lungs look darker on the X-ray. This can happen for many reasons, and often needs more tests to understand fully. Doctors look at the pattern of the shadowing, where it is located, and the size of the lungs to help make a diagnosis.

Signs

The silhouette sign helps doctors find where lung problems are by looking at parts of the heart or other structures that might not show up clearly if there is a problem nearby. The air bronchogram sign shows the airways clearly surrounded by other materials, which often points to certain lung diseases.

Disease mimics

Sometimes, things that look like diseases on an X-ray are actually normal parts of the body or harmless changes. For example, a big thymus can look like a widened mediastinum. Also, skin folds near the supraclavicular fossa might seem like a periosteal reaction of the clavicle, but they are not harmful.

Limitations

Chest X-rays are a common and safe way to check for problems in the chest. However, some serious chest issues might not show up on an X-ray. For instance, someone having a heart attack might still have a normal-looking chest X-ray. In such cases, doctors may need to use other tests to find out what’s wrong.