This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'Signet ring sign is seen in: March 2013 \nSelect and explain. \nA. Blastomycosis, B. Bronchogenic carcinoma, C. Invasive aspergillosis, D. Bronchiectasis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. Bronchiectasis Signet ring sign The signet ring sign is a CT finding seen in patients with Bronchiectasis The ring of soft-tissue attenuation represents the wall of the dilated bronchus seen on a cross-sectional CT scan, whereas the low-attenuating circle of air represents air within the dilated bronchus. The circle of soft-tissue attenuation abutting the ring represents a cross-sectional image of the pulmonary aery that lies adjacent to the dilated bronchus.', 'role': 'assistant'}]