A-line (ultrasound)

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An a-line is an ultrasonographic artifact appreciated during the insonation of an aerated lung.

The term may be applied to the horizontal, echogenic long path reverberation artifacts that occur beneath the pleural line at multiples of the distance between the ultrasound probe and the visceral-parietal pleural interface which appear to fatigue as a function of depth. The artifact is hypothesized to result from sound reflecting between two parallel, closely apposed reflective surfaces.