This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiology Q Bank, Subject name: Radiology
[{'content': 'A 75 - year - old lady with severe chronic obstructive pulmonary disease (COPD) presents with acute breathlessness. The chest X - ray shows there is no focal consolidation. She is afebrile, but D - dimers are markedly elevated. Which of the following is best investigation to diagnose this condition ? \nSelect and explain. \nA. MRI, B. Ventilation - perfusion (V/Q) scan, C. High resolution CT thorax, D. CT pulmonary angiography', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The patient has a possible Pulmonary embolus. Gold standard for diagnosis of PEa Pulmonary angiography V/Q is difficult to interpret in patients with cardiorespiratory disease. V/Q is IOC in iodine allergics and pregnancy.', 'role': 'assistant'}]