Artifactual Lung Ultrasonography: It Is a Matter of Traps, Order, and Disorder

Featured Application The differential diagnosis between a normally aerated lung and a lung with interstitial pathology is based on the interpretation of ultrasound vertical artifacts. However, the physical basis of these artifacts and their correlations with the causal pulmonary pathology is not known in depth. Theoretical and experimental studies strongly support the hypothesis that the link between non-consolidative parenchymal pathological conditions of the lung and the presence of vertical artifacts is mediated by the acoustic properties of the pleura and is caused by a structural change in the geometry and connectivity of subpleural air spaces. The future development of lung ultrasound needs a better knowledge of ultrasound artefactual semiotics, a valid correlations between artefactual evidence and the superficial lung structure, and, not least, the development of ultrasound equipment, software and probes, specifically dedicated to lung sonography. Abstract When inspecting the lung with standard ultrasound B-mode imaging, numerous artifacts can be visualized. These artifacts are useful to recognize and evaluate several pathological conditions in Emergency and Intensive Care Medicine. More recently, the interest of the Pulmonologists has turned to the echographic study of the interstitial pathology of the lung. In fact, all lung pathologies which increase the density of the tissue, and do not consolidate the organ, are characterized by the presence of ultrasound artifacts. Many studies of the past have only assessed the number of vertical artifacts (generally known as B-Lines) as a sign of disease severity. However, recent observations suggest that the appearance of the individual artifacts, their variability, and their internal structure, may play a role for a non-invasive characterization of the surface of the lungs, directing the diagnoses and identifying groups of diseases. In this review, we discuss the meaning of lung ultrasound artifacts, and introduce hypothesis on the correlation between their presence and the structural variation of the sub-pleural tissue in light of current knowledge of the acoustic properties of the pleural plane.