Lung ultrasonography: Normal aeration pattern and alveolar consolidation

(A) Normal aeration pattern: Normally aerated lung is not visible as a distinct structure. Due to major mismatch of acoustic impedance and velocity of sound between the air and the soft tissue of the chest wall, the ultrasound waves are fully reflected at the pleural interface. This results in a an A line pattern due to reverberation artifact that is characteristic of normal aeration pattern.
(B) Alveolar consolidation: This image shows translobar consolidation of the left lower lobe. The affected alveolar compartment is airless, so the consolidated lung has an echogenicity pattern resembling that of liver (hepatization of lung). The small hyperechoic foci within the consolidated lobe represent residual air that remains within bronchial structures.