Facts about and Definition of Chest X-Ray
A chest X-ray test is a very common, non-invasive radiology test that produces an image of the chest and the internal organs. To produce a chest X-ray test, the chest is briefly exposed to radiation from an X-ray machine and an image is produced on a film or into a digital computer. Chest X-ray is also referred to as a chest radiograph, chest roentgenogram, or CXR. Depending on its density, each organ within the chest cavity absorbs varying degrees of radiation, producing different shadows on the film. Chest X-ray images are black and white with only the brightness or darkness defining the various structures. For example, bones of the chest wall (ribs and vertebrae) may absorb more of the radiation and thus, appear whiter on the film.
On the other hand, the lung tissue, which is mostly composed of air, will allow most of the radiation to pass through, developing the film to a darker appearance. The heart and the aorta will appear whitish, but usually less bright than the bones, which are more denser.
Chest X-rays tests are ordered by physicians for a variety of reasons. Many clinical conditions can be evaluated by this simple radiology test. Some of the common conditions detected on a chest X-ray include, pneumonia, enlarged heart, congestive heart failure, lung mass, rib fractures, fluid around the lung (pleural effusion), and air around the lung (pneumothorax).
In general, a chest X-ray test is a simple, quick, inexpensive, and relatively harmless procedure with minimal risk of radiation. It is also widely available.
How to Prepare for a Chest X-Ray
As noted above, usually a gown is worn and metal containing materials are removed from the body before an X-ray is taken. Pregnant women need to notify the doctor and the technician as some or all images may not be taken in order to avoid unnecessary X-ray radiation exposure to the fetus. Precautions, such as, protective lead covers may be placed on the abdomen to avoid radiation to the fetus when an X-ray is absolutely necessary.
Chest X-Ray Procedure
To prepare for a chest X-ray, the patient is typically instructed to wear a gown and remove all metal containing objects around the upper body (necklaces, zippers, bras, buttons, jewelry, eyeglasses, etc.) as these will interfere with the visualization of the tissues. No other specific preparation, such as fasting, is necessary for a routine chest X-ray.
The patient is then asked by the technician to stand in front of a surface adjacent to the film that records the images. The front of the chest is closest to the surface. Another part of the machine that releases the radiation is then placed about 6 feet away, behind the patient. When the positioning is appropriate (normal standing position with arms on the sides), the technician may advise the patient to take a deep breath and hold it and then takes the image by activating the device (similar to taking a regular photograph). The image is then captured on the film within a few seconds. The film can be developed within a few minutes to be reviewed by the doctor.
Usually one image is done from back to front (referred to as posterior-anterior, or "PA" view) and, as described above, a second image using a sideways view from side-to-side (lateral) can be done as well.
In situations where someone is unable to stand (too weak, disabled, or hospitalized), the image can be taken while laying down with the recording surface placed behind the back. Because the image is taken from the front to back in this scenario, it is called an anterior-posterior (AP) view. A lateral film is generally not possible in these situations. This method can also be called a portable chest X-ray because the X-ray machine is wheeled in to the patient in order to take the X-ray. Other chest images from different positions are sometimes ordered by the doctor for special situations.
Medical Reasons for Chest X-Rays
Doctors generally order chest X-ray tests in conjunction with taking a medical history and performing a physical exam to confirm or exclude a suspected chest. Some of the common reasons to order a chest X-ray test are cough, shortness of breath, chest pain, poor oxygenation (hypoxia), back pain, chest injury, and fever. Certain abnormalities detected on the doctor's physical examination of the lung, heart, or chest wall (abnormal heart sounds, abnormal lung sounds, chest wall deformity, etc.) Pre-operative evaluation (before an operation to screen for any obvious lung disease) Follow-up of a previously abnormal chest X-ray test
To confirm the proper placement of certain devices within the chest, such as pacemakers, endotracheal (breathing tubes - when someone is placed on artificial breathing machine), catheters in large veins of the chest (central lines), etc. There are many other more specific reasons that a doctor may choose to order a chest X-ray depending on each individual situation.
Chest X-Ray Risks
Risks associated with having a chest X-ray test are minimal, but they need to weighed against the benefits for each individual case. Chest X-rays release radiation to the body in order to produce an image. The amount of radiation, however, is very small and it does not last in the body after the image is taken. Pregnant women who require a chest X-ray are advised to notify the doctor and the X-ray technician so proper precautions can be taken to minimize radiation exposure to the fetus.
Normal Chest X-Rays
As mentioned earlier, the image on chest X-ray film is in shades of black and white, similar to a negative of a regular photograph. The shadows on a chest X-ray test depend on the degree of absorbed radiation by the particular organ based on its composition. Bony structures absorb the most radiation and appear white on the film. Hollow structures containing mostly air, such the lungs, normally appear dark. In a normal chest X-ray, the chest cavity is outlined on each side by the white bony structures that represent the ribs of the chest wall. On the top portion of the chest is the neck and the collar bones (clavicles). On the bottom, the chest cavity is bordered by the diaphragm under which is the abdominal cavity. On either side of the chest wall, the bones of the shoulders and arms are easily recognizable.
Inside the chest cavity, the vertebral column can be seen down the middle of the chest, splitting it nearly in equal halves. On each side of the midline, the dark appearing lung fields are seen. The white shadow of the heart is in the middle of the field, atop the diaphragm and more to the left side. The trachea (wind pipe), aorta (main blood vessel exiting the heart), and the esophagus descend down the middle, overlapping the vertebral column.
Abnormal Chest X-Rays
Many abnormalities can be detected on a chest X-ray test. Common abnormalities seen on a chest X-ray test include:
- pneumonia (abnormally white or hazy shadow on the lung fields that would normally look dark);
- abscess in the lung (lung abscess);
- fluid collection between the lung and the chest wall appearing whiter than the lungs and making the sharp lung borders on the film more hazy (pleural effusion);
- pulmonary edema (fluid build-up in the lung or its blood vessels) seen as diffuse haziness on the lung fields (for example, from congestive heart failure);
- enlarged heart size (or cardiomegaly);
- broken ribs or arm bones (irregularity in the structure and shape of any of the ribs or the humerus bone of the arm);
- broken vertebrae or vertebral fractures;
- dislocated shoulders;
- lung cancer or other lung masses (irregular and abnormal shadow on the lung fields);
- cavities in the lungs or cavitary lung lesions (tuberculosis, sarcoidosis, etc.);
- abnormal presence of air between the chest wall and the lung creating a distinct black shadow (darker than the lung fields) between the border of the lung tissue and the inside border of the chest wall (pneumothorax);
- hiatal hernia (protrusion of the upper portion of the stomach into the chest cavity); and
- aortic aneurysm (dilated aorta - a widening of the midline of the chest overlying the vertebral column).
These are some of the common abnormal findings that can be seen on chest X-ray test. There are many other less common abnormalities that can be detected on chest X-rays.
How to Get the Results of Chest X-Rays
After the chest X-ray test is read by the doctor, a report is typically generated and placed in the patient's chart. If the X-ray is performed in a radiology facility, the report from a radiologist is usually sent to the doctor who had ordered the test. The written report can also be provided to the patient after proper forms to release medical information are signed.
Diseases and Conditions Diagnosed with Chest X-Rays
Many diseases or conditions may be detected or diagnosed based on a chest X-ray test. A chest X-ray test can also be very helpful in ruling out suspected diagnoses. Some of the common conditions that can be evaluated by a chest X-ray tests are pneumonia, congestive heart failure, emphysema, lung mass or lung nodule, tuberculosis, fluid around the lung (pleural effusion), fracture of the vertebrae (bones of the back), rib fractures, or cardiomegaly, or enlarged heart.
How to Interperet Chest X-Rays
Chest X-ray tests are most frequently interpreted by a radiologist (doctor specialized in radiology). Other doctors who often review and interpret the results of chest X-ray tests include emergency room physicians, internal medicine doctors, pediatricians, family practice doctors, pulmonologists (lung doctors), cardiologists (heart doctors), anesthesiologists, chest surgeons, and oncologists (cancer doctors).
Generally, doctors use the information from a chest X-ray together with medical history, physical examination, and other clinical data to help to make a clinical decision.