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': 'Investigation of choice for bronchiectasis is: September 2009 \nSelect and explain. \nA. Chest X-ray, B. MRI, C. CT scan, D. V-P scan', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: CT Scan High Resolution Computed Tomography (HRCT) is the investigation of choice for the diagnosis of bronchiectasis. It shows dilated bronchi adjacent to vascular structure forming a signet ring shape. The diameter of the lumen of the bronchi is characteristically larger than that of the vascular structure. The dilatation of proximal airways alone may indicate the possibility of allergic bronchopulmonary aspergillosis. Dilated bronchi with multiple small parenchymal nodules point towards possible infection with Mycobacterium avium complex.', 'role': 'assistant'}]