Chest X-ray

Doctors know to what extent each of the body’s tissues absorbs X-rays. The less dense a substance is, the greater the ability of X-rays to pass through it. In the body, soft tissues — such as skin, fat, muscle, and blood are more transparent to X-rays than hard, dense substances such as bone. Thus, when a beam of X-rays is directed at a part of the body, the chest for example, X-rays pass easily through the soft tissues but do not penetrate the ribs and the breastbone, which cast a shadow. Because X-rays blacken photographic film, the shadow of the bone appears as a white area; the soft tissues (heart and lungs) are represented on the film as dark gray.

X-rays are produced using electric power in a device called an X-ray tube. The X-rays travel in straight lines, radiating outward from the target, and emerge as an X-ray beam from a small aperture in the lead casing that surrounds the X—ray tube. The beam is focused on a part of the body placed against an X—ray cassette. When the film is processed, the body parts that allowed few X-rays to pass through appear white; those that transmitted many rays appear black.

X-rays give a photographic image of part of the body. This image may confirm or rule out the doctor’s diagnosis. The simplest type of X-ray examination is a single "snapshot" image. These plain X-ray pictures are an excellent means of showing bone and dense areas in the body, such as tumors, and are commonly used for examining the chest, skull, spine, and other parts of the skeleton.

When you arrive for an X-ray, the X-ray technician or radiologist will explain the procedure and will position you in contact with a cassette containing the X-ray film. You will be asked to remain very still during the period of exposure (which usually lasts less than a second), since any movement produces a blurred image that is difficult to interpret. When all is ready - you are in the correct position, the film is in place, and the machine has been set to the right exposure, the technician moves briefly behind a protective screen (from which he or she can still see and talk to you) and presses the exposure button. You will not feel any sensation; X-rays are painless.

Several X-ray pictures are usually taken from different angles to get as complete a view as possible of the area in question. The technician will alter your position and that of the equipment as required between shots. As soon as the pictures are taken, the films are passed into an automatic developing machine and are developed, fixed, and dried within a few minutes. If there is reason for urgency, the films are examined immediately by a radiologist. However, in most cases, the radiologist reviews your films later in his or her office, writes a formal report, and discusses the results with your doctor.

X-ray images of the heart and circulatory system allows doctors to investigate a wide range of disorders. A chest X-ray is a simple method of obtaining an image of the heart. Having a chest X-ray is a quick and painless procedure that is usually done on an outpatient basis. A chest X-ray reveals the size, shape, and position of the heart and the large blood vessels that carry blood in and out of the heart chambers. Disorders that can be detected include enlargement of the heart chambers, ballooning of the upper part of the aorta, and expansion of the heart outline from accumulation of fluid in the pericardial sac.

A chest X-ray can confirm that the heart is failing to keep up with its work load by revealing accumulation of blood in the vessels, the presence of fluid inside the lungs, or an enlarged heart. With routine chest x-ray pictures, doctors can frequently tell if calcium has collected on the heart valves or in the aorta or can even see calcium in coronary arteries. Calcium deposits may suggest certain types of disease. They can also determine how effective a certain treatment is in improving heart failure and decreasing lung congestion.

Compared with some of the sophisticated imaging methods used today, the information gained from a chest X-ray is considered one dimensional.