B-lines and Comet-tail Artifacts in Lung Ultrasound: Mechanisms and Clinical Implications

The diagnostic utility of lung ultrasound (LUS) relies on the interpretation of sonographic artifacts, necessitating a clear distinction between "comet-tail artifacts" and "ring-down artifacts (i.e., B-lines)." However, these two types of artifacts are frequently confused in clinical practice. LUS has been validated as a highly accurate technique for both qualitative diagnosis and quantitative assessment of alveolar-interstitial pathologies. Although B-lines can be detected in a variety of pulmonary conditions, characteristic variations in the pleural line provide valuable clues for differential diagnosis. In cardiogenic pulmonary edema, the pleural line appears smooth, reflecting the homogeneous distribution of fluid within the subpleural interstitium and interlobular septa. In contrast, in interstitial lung disease, the pleural line is often irregular - a finding not necessarily attributable to pleural pathology itself, but possibly related to subpleural interstitial abnormalities. These commonly misunderstood aspects underscore the need for clarification in this article, which utilizes an in vitro teaching phantom to explore the formation of such artifacts.