Which sign suggests vascular cutoff in pulmonary embolism?

Westermark's sign describes a focal area of oligemia (decreased blood flow) in the lung associated with pulmonary embolism. It is visible on a chest radiograph and manifests as a distinct difference in vascular markings between the affected region and the surrounding lung areas. This sign showcases the absence of blood supply to the region of the lung that is affected by the embolism, indicating a vascular cutoff.

This sign is typically observed in cases of larger pulmonary emboli where a significant portion of the pulmonary vasculature is impacted, allowing for the radiological representation of reduced vascular markings. Recognizing Westermark's sign can thus assist in the diagnosis of pulmonary embolism by suggesting the presence of vascular obstruction.

Other signs listed relate differently to the imaging findings in pulmonary conditions. For example, Hampton's Hump refers to a wedge-shaped infarct, typically not associated with direct visualization of vascular changes. The Fleischner sign indicates possible right heart strain but does not directly reflect vascular blood flow alterations. The silhouette sign helps localize disease processes by indicating loss of normal borders due to adjacent opacified lung but does not directly suggest a vascular cutoff.