Indication/Technique

The chest X-ray is the most frequently requested X-ray at the radiology department. A primary indication is to exclude/confirm lung pathology (including overfilling, pneumonia, pneumothorax). In addition, it provides some information on inserted lines and tubes (deep venous lines, tracheal tube, gastric tube), heart/vessels (cardiomegaly, aneurysm), the mediastinum (lymphadenopathy), the ribs/vertebrae and soft tissues (subcutaneous emphysema).

When an X-ray is made, an X-ray beam leaves the X-ray tube, passes through the body and hits a phosphorus plate/detector. The whiteness (= density) depends on the amount of radiation passing through the tissue. The more X-rays are obstructed (absorbed or scattered) and do not reach the phosphorus plate/detector, the denser (= whiter) the image. Highly absorbent materials, such as metal, will be imaged as dense. Another example: X-rays travel more easily through air-filled lungs (black) than bone (white). The information received on the plate is converted into a digital image, in this case the chest X-ray.

  • Each chest X-ray is evaluated as if you are standing in front of the patient; so the right side of the image is the patient’s left side and vice versa.
  • Importantly, the X-ray beam has a divergent property. This means it widens as the distance to the X-ray tube increases. A drawback of this phenomenon is that tissues/structures farther from the plate are imaged larger.