combining form denoting posterior. Example: posterolateral (behind and at the side of).
(PA) adj. from the back to the front. In radiography it refers to the direction of the X-ray beam (i.e. from the back to the front of the patient); thus a PA radiograph is taken with the X-ray film in front of the patient. Normally, a chest radiograph will be PA: since the heart is in the front of the chest, its size can be most accurately assessed if the X-ray film is in front of the chest. Compare decubitus; anteroposterior.... posteroanterior
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