Which of the following signs is associated with pulmonary embolism on a chest X-ray?

Westermark's sign is known to be associated with pulmonary embolism on a chest X-ray. This sign is characterized by an area of decreased vascular markings on an image of the chest, which occurs due to the obstruction of blood flow to the affected lung region. As the blood vessels become occluded by the embolism, the affected lung areas appear less vascularized, leading to a notable difference in the blood flow pattern and subsequently visible on X-ray.

This sign is particularly important in the context of diagnosing pulmonary embolism, as it highlights the impact of the clot on pulmonary circulation. When present, it can support the diagnosis of embolism, although it is often not prominently seen in all cases.

The other signs mentioned have different associations and are not specifically indicative of pulmonary embolism. For example, Kerley B lines are typically seen in interstitial edema, the bat wing appearance is characterized by bilateral perihilar opacities often seen in pulmonary edema, and air bronchograms usually occur in cases of pneumonia or lung consolidation, not pulmonary embolism. Understanding Westermark's sign and its clinical relevance is crucial for the identification and management of pulmonary embolism.