Definition of PA (posteroanterior)
PA (posteroanterior): In anatomy, PA stands for posteroanterior: 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: 6/9/2016