Chest X-rays are a common type of exam. A chest X-ray is often among the first procedures you'll undergo if your doctor suspects you have heart or lung disease. It can also be used to check how you are responding to treatment.

A chest X-ray can reveal many things inside your body, including:

• The condition of your lungs. Chest X-rays can detect cancer, infection or air collecting in the space around a lung (pneumothorax). They can also show chronic lung conditions, such as emphysema or cystic fibrosis, as well as complications related to these conditions.
• Heart-related lung problems. Chest X-rays can show changes or problems in your lungs that stem from heart problems. For instance, fluid in your lungs (pulmonary edema) can be a result of congestive heart failure.
• The size and outline of your heart. Changes in the size and shape of your heart may indicate heart failure, fluid around the heart (pericardial effusion) or heart valve problems.
• Blood vessels. Because the outlines of the large vessels near your heart — the aorta and pulmonary arteries and veins — are visible on X-rays, they may reveal aortic aneurysms, other blood vessel problems or congenital heart disease.
• Calcium deposits. Chest X-rays can detect the presence of calcium in your heart or blood vessels. Its presence may indicate damage to your heart valves, coronary arteries, heart muscle or the protective sac that surrounds the heart. Calcium deposits in your lungs are most often from an old, resolved infection.
• Fractures. Rib or spine fractures or other problems with bone may be seen on a chest X-ray.
• Postoperative changes. Chest X-rays are useful for monitoring your recovery after you've had surgery in your chest, such as on your heart, lungs or esophagus. Your doctor can look at any lines or tubes that were placed during surgery to check for air leaks and areas of fluid or air buildup.
• A pacemaker, defibrillator or catheter. Pacemakers and defibrillators have wires (leads) attached to your heart to make sure your heart rate and rhythm are normal. Catheters are small tubes used to deliver medications or for dialysis. A chest X-ray usually is taken after placement of such medical devices to make sure everything is positioned correctly.

You may be concerned about radiation exposure from chest X-rays, especially if you have them regularly. But the amount of radiation from a chest X-ray is low — even lower than what you're exposed to through natural sources of radiation in the environment.

Even though the benefits of an X-ray outweigh the risk, you may be given a protective apron if you need more than one image. Tell your doctor if you're pregnant or might be pregnant. The procedure can be performed in a way to protect your abdomen from the radiation.

Before the chest X-ray, you generally undress from the waist up and wear an exam gown. You'll need to remove jewelry from the waist up, too, since both clothing and jewelry can obscure the X-ray images.

During the procedure, your body is positioned between a machine that produces the X-rays and a plate that creates the image digitally or with X-ray film. You may be asked to move into different positions in order to take views from both the front and the side of your chest.

During the front view, you stand against the plate, hold your arms up or to the sides and roll your shoulders forward. The X-ray technician may ask you to take a deep breath and hold it for several seconds. Holding your breath after inhaling helps your heart and lungs show up more clearly on the image.

During the side views, you turn and place one shoulder on the plate and raise your hands over your head. Again, you may be asked to take a deep breath and hold it.

Having X-rays taken is generally painless. You don't feel any sensation as the radiation passes through your body. If you have trouble standing, you may be able to have the exam while seated or lying down.

A chest X-ray produces a black-and-white image of the organs in your chest. Structures that block radiation appear white, and structures that let radiation through appear black.

Your bones appear white because they are very dense. Your heart also appears as a lighter area. Your lungs are filled with air and block very little radiation, so they appear as darker areas on the images.

A radiologist — a doctor trained in interpretation of X-rays and other imaging exams — analyzes the images, looking for clues that may suggest if you have heart failure, fluid around your heart, cancer, pneumonia or another condition.

Your own doctor will discuss the results with you as well as what treatments or other tests or procedures may be necessary.