Qualitative distortion at fluid-air interfaces during echography of simulated pleural effusions

Beams of diagnostic ultrasound passing through pleural effusions produce an irregular band of complex echoes, when such beams strike aerated lung. To simulate pleural effusions and study this fluid-gas interface, we scanned latex bags of water and air which lay in a water bath beneath a uniform portion of veal rib cage. The general shape of an air-containing object could be determined under these conditions. The display of the upper surface of the gas-filled object was broad and heterogeneous but this zone of distortion was thin in relation to the overlying fluid layer. Fluid thicknesses exceeding 1 cm could be detected under these conditions even when they abut gas-filled structures. These preliminary data suggest that complex artefacts occurring at fluid-gas interfaces during echography of laboratory models simulating pleural effusions would not preclude useful volumentric estimations of overlying fluid layers.