Views::Chest radiograph


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Positioning for a PA chest x-ray

Different views (also known as projections) of the chest can be obtained by changing the relative orientation of the body and the direction of the x-ray beam. The most common views are posteroanterior, anteroposterior, and lateral. In an posteroanterior (PA) view, the x-ray source is positioned so that the x-ray beam enters through the posterior (back) aspect of the chest, and exits out of the anterior (front) aspect where the beam is detected. To obtain this view, the patient stands facing a flat surface behind which is an x-ray detector. A radiation source is positioned behind the patient at a standard distance (most often 6 feet, 1,8m), and the x-ray beam is fired toward the patient.

In anteroposterior (AP) views, the positions of the x-ray source and detector are reversed: the x-ray beam enters through the anterior aspect and exits through the posterior aspect of the chest. AP chest x-rays are harder to read than PA x-rays and are therefore generally reserved for situations where it is difficult for the patient to get an ordinary chest x-ray, such as when the patient is bedridden. In this situation, mobile X-ray equipment is used to obtain a lying down chest x-ray (known as a "supine film"). As a result, most supine films are also AP.

A chest radiograph with the angle parts of the ribs and some other landmarks labeled.

Lateral views of the chest are obtained in a similar fashion as the posteroanterior views, except in the lateral view, the patient stands with both arms raised and the left side of the chest pressed against a flat surface.

Typical views

Required projections can vary by country and hospital, typically an erect postero-anterior projection is first preference, if this is not possible then an antero-posterior view will be taken. Further imaging depends on local protocols which is dependent on the hospital protocols, the availability of other imaging modalities and the preference of the image interpreter.

Additional views

  • Decubitus - taken while the patient is lying down, typically on his side. useful for differentiating pleural effusions from consolidation (e.g. pneumonia) and loculated effusions from free fluid in the pleural space. In effusions, the fluid layers out (by comparison to an up-right view, when it often accumulates in the costophrenic angles).
  • Lordotic view - used to visualize the apex of the lung, to pick up abnormalities such as a Pancoast tumour.
  • Expiratory view - helpful for the diagnosis of pneumothorax.
  • Oblique view - useful for the visualization of the ribs and sternum. Although it's necessary to do the appropriate adaptations to the x-ray dosage to be used.

Chest radiograph sections
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