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': 'In a patient with renal cell carcinoma with a thrombus in the IVCrenal vein, which of the following is the best for diagnosis? \nSelect and explain. \nA. CT scan, B. Angiography, C. Colour Doppler imaging, D. IVP', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. CT scan', 'role': 'assistant'}]