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Medical Definition of Posteroanterior (PA)

Posteroanterior (PA): In anatomy, posteroanterior (PA) means from back-to-front. For example, a PA X-ray of the chest is taken from back-to-front.

PA in this respect is the opposite of AP, which stands for anteroposterior: from front-to-back.

Source: MedTerms™ Medical Dictionary
Last Editorial Review: 7/1/2016

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