Chest X-ray

Two chest radiographs are proposed: one AP projection, the other lateral projection. The legend is in the middle of the page.

Chest X-ray: AP Projection

1, Trachea. 2, Clavicle. 3, 4th posterior rib. 4, Right main bronchus. 5, Right breast shadow. 6, Gastric air bubble. 7, Left hemidiaphragm. 8, Left ventricle. 9, Descending aorta. 10, Left pulmonary artery. 11 Left upper lobe. 12, Left atrium. 13, Right ventricle. 14, Right pulmonary artery. Right pulmonary veins. 15, Vertebral body (Thoracic spine). 16, Posterior costophrenic angle.

Chest X-ray: lateral projection

Chest X-ray or chest radiograph is the most commonly performed diagnostic imaging test. This noninvasive method produces images of the heart, lungs, airways, blood vessels, and the bones of the chest and spine(1)

Like other radiography methods, taking images with X-ray involves exposing a part of the body to a small ionizing radiation dose(2)

Physicians use chest X-rays to diagnose and treat medical conditions affecting the chest, its contents, and nearby structures. A chest X-ray can also reveal fluid in or around the patient’s lungs or air surrounding a lung(3)

Functions of Chest X-Ray

Chest X-rays are among the first procedures conducted if the doctor suspects that a patient has a heart or lung disease. This imaging method can also check how a patient is responding to specific treatments. 

Common symptoms that can be diagnosed using chest X-rays include chest pain or injury, a bad or persistent cough, breathing difficulties, and fever(4)

Chest radiographs can reveal and identify the following conditions(5)

  • Lung conditions: Chest X-rays can detect infection, cancer, or air collecting in the space around a lung that can cause it to collapse. X-rays can show lung conditions, including pneumonia, pneumothorax, emphysema, and interstitial lung disease.
  • Heart-related lung problems: Chest radiographs can show changes or problems in the lungs that stem from heart problems. For instance, congestive heart failure can lead to the accumulation of fluid in the lungs. 
  • The heart’s size and outline: Changes in the heart’s size and shape may indicate fluid around the heart, heart valve problems, or heart failure.
  • Blood vessels: The outlines of the large vessels (aorta, pulmonary arteries, and veins) near the heart are visible on X-rays. Chest X-rays can reveal aortic aneurysms, blood vessel problems, or congenital heart disease.
  • Calcium deposits: Chest X-rays can detect the presence of calcium in the heart or blood vessels. Calcium presence may indicate fats and other substances in the vessels, damage to the heart valves, coronary arteries, or heart muscle. 
  • Fractures: Spine or rib fractures and other bone problems can be seen on chest X-rays.
  • Postoperative changes: X-rays are useful in monitoring a patient’s recovery after having surgery on the chest, such as the heart, lungs, or esophagus. Doctors can check for any air leaks, fluid, or air buildup on the surgical tubes or lines. 
  • Pacemaker, defibrillator, or catheter: Chest X-rays are usually taken after these medical devices’ placement to ensure their correct positioning in the body.

How Does Chest X-ray Work? 

The chest X-rays equipment consists of a wall-mounted, box-like apparatus and an X-ray producing tube positioned about six feet away from the patient(6). The apparatus contains the X-ray film or a special plate that digitally records the images. 

The X-ray tube is arranged in a suspended manner over the table where the patient lies on their back. The drawer under the table holds the X-ray film or digital recording plate(7).

X-rays are a form of electromagnetic radiation similar to light or radio waves that pass through most objects, including the body. 

Once carefully aimed at a body part being examined, the X-ray machine produces a small burst of radiation that passes through the body and records the image on photographic film or a special detector(8).

A portable X-ray machine or a compact apparatus is also available and can be taken to the patient in the emergency room or a hospital bed. 

The X-ray tube connects to a flexible arm extended over the patient. Meanwhile, an X-ray film holder or image recording plate is placed beneath the patient(9)

Various parts of the body absorb X-rays to varying degrees. Dense bones absorb much of the radiation, while soft tissues (muscle, fat, and organs) allow more X-rays to pass through them(10).

As a result, bones (ribs and spine) appear white, soft tissues show up in shades of gray, and air appears black on X-rays(11)

Most X-rays images are digital files stored electronically. These digital images are easily accessible to doctors for diagnosis and disease management.

Chest X-ray Projections

Different chest projections or views can be obtained by changing the body’s relative orientation and the X-ray beam’s direction. The most common projections are posteroanterior, anteroposterior, and lateral.

In the posteroanterior view, the X-ray beam enters through the chest’s posterior (back) aspect and exits out of the anterior (front) aspect where the beam is detected. The patient stands facing a flat surface behind an X-ray detector(12).

In the anteroposterior view, the positions of the X-ray beam and detector are reversed. The X-ray enters through the chest’s anterior aspect and exits through the posterior aspect(13)

Obtaining lateral views of the chest is similar to the posteroanterior views. However, the patient stands with both arms raised while the chest’s left side is pressed against a flat surface(14)

  1. Chest X-ray. Retrieved from:
  2. X-rays. Retrieved from:
  3. Chest X-rays. Retrieved from:
  4. Ibid.
  5. Ibid.
  6. Protocols for the Radiation Safety Surveys of Diagnostic Radiological Equipment. Retrieved from:
  7. op. cit. 
  8. Ibid.
  9. Ibid.
  10. Ibid.
  11. Ibid.
  12. X-ray Film Reading Made Easy. Retrieved from:
  13. Ibid.
  14. Ibid.
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