What imaging sign on CT is associated with recovery from invasive aspergillosis?

What imaging sign on CT is associated with recovery from invasive aspergillosis?

• A. Halo sign
• B. Air crescent sign
• C. Tree-in-bud sign
• D. Reverse halo sign

Answer: (B)

Air crescent sign. This CT finding shows a crescent-shaped air-filled space within a cavitary lesion that forms as necrotic fungal tissue is cleared during recovery, often as neutrophil counts recover and the immune system gains control after antifungal therapy. It marks a shift toward healing rather than active invasion. Halo sign represents the early angioinvasive stage, with a nodule surrounded by ground-glass opacity from hemorrhage, not recovery. Tree-in-bud reflects small airways disease or endobronchial spread, not a recovery indicator. The reverse halo (atoll) sign is a ring of consolidation around central ground-glass and is more associated with other processes (like organizing pneumonia or mucormycosis) and is not a reliable sign of recovery in invasive aspergillosis.

Air crescent sign. This CT finding shows a crescent-shaped air-filled space within a cavitary lesion that forms as necrotic fungal tissue is cleared during recovery, often as neutrophil counts recover and the immune system gains control after antifungal therapy. It marks a shift toward healing rather than active invasion.

Halo sign represents the early angioinvasive stage, with a nodule surrounded by ground-glass opacity from hemorrhage, not recovery. Tree-in-bud reflects small airways disease or endobronchial spread, not a recovery indicator. The reverse halo (atoll) sign is a ring of consolidation around central ground-glass and is more associated with other processes (like organizing pneumonia or mucormycosis) and is not a reliable sign of recovery in invasive aspergillosis.