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.