Ex Vivo Lung Sonography: Morphologic-Ultrasound Relationship

The nature of lung ultrasound “artifacts” (B-lines, White Lung) has not yet been determined. We need to know what pathological structure and what physical mechanism create artifacts. We believe that lung ultrasonographic imaging is the acoustic behavior of ultrasounds crossing substrates of variable porosity or density. Each of 5 New Zeeland white rabbit right lungs was sequentially inserted in cylindrical, rigid, hermetically sealed containers, with different volumes of 50 mL, 30 mL, 20 mL and 15 mL. Both lung and internal space of each container communicated with external air through a cork cap: the former through a cannula connected to trachea lumen and the latter through a tube connected to an aspiration system. Each system underwent negative pressure to get different known degrees of lung inflation. Densities were obtained for each lung at each level of inflation. Every lung was studied through ultrasonography and then sectioned and analyzed to correlate images with histological appearance. In normal lung the variation of the pleural plane from specular reflector to generator of acoustic interference recognizes a mechanism which is related to values of tissue density. Artifacts described in lung ultrasonography as B-lines and White Lung appear in the normal lung through air dependent or weight dependent increases in density. Conclusion: Ultrasound lung artifacts are density or porosity related. B-Lines and white lung (as in pathological conditions) can be reproduced in normal lungs that are deflated (ie denser or less porous) to levels of density which are not realizable under in vivo physiological conditions (