Chest X-rays, or a chest film, is a projection radiograph of the chest used to diagnose conditions affecting the chest, its contents, and nearby structures. Chest X-rays are among the most common X-rays taken, being diagnostic of many conditions. Like all methods of radiography, chest X-rays employ ionizing radiation to generate images of the chest. The mean radiation dose to an adult from a chest X-ray is around 0.02 mSv for a front view (PA or posterior-anterior) and 0.08 mSv for a side view (LL or latero-lateral).
Chest X-rays are used to diagnose many conditions involving the chest wall, including its bones, and also structures contained within the thoracic cavity including the lungs, heart, and great vessels. Pneumonia and congestive heart failure are very commonly diagnosed by chest radiograph. Chest radiographs are used to screen for job-related lung disease in industries such as mining where workers are exposed to dust.
For some conditions of the chest, radiography is good for screening but poor for diagnosis. When a condition is suspected based on chest X-rays, additional imaging of the chest can be obtained to definitively diagnose the condition or to provide evidence in favor of the diagnosis suggested by initial chest X-rays. Unless a fractured rib is suspected of being displaced, and therefore likely to cause damage to the lungs and other tissue structures, X-rays of the chest are not necessary as it will not alter patient management.
The main regions where a chest X-ray may identify problems are:
- Airways, including hilar adenopathy or enlargement.
- Breast shadows.
- Bones, e.g. rib fractures and lytic bone lesions.
- Cardiac silhoutte, detecting cardiac enlargement.
- Costophrenic angles, including pleural effusions.
- Diaphragm, e.g. evidence of free air, indicative of perforation of an abdominal viscus.
- Edges, e.g. apices for fibrosis, pneumothorax, pleural thickening or plaques.
- Extrathoracic tissues.
- Fields (lung parenchyma), being evidence of alveolar flooding.
- Failure, e.g. alveolar air space disease with prominent vascularity with or without pleural effusions.
While chest X-rays are a cheap and relatively safe method of investigating diseases of the chest, there are a number of serious chest conditions that may be associated with a normal chest X-ray and other means of assessment may be necessary to make the diagnosis. For example, a patient with an acute myocardial infarction may have a completely normal chest X-ray.
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