This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Peripheral and Visceral Vascular Imaging, Subject name: Radiology
[{'content': 'Investigation of choice for DVT is- \nSelect and explain. \nA. Doppler USG, B. Angiography, C. CT scan, D. MRI', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Doppler USG o Doppler USG is the first investigation of choice for DVT.", 'role': 'assistant'}]