This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuroradiology, Subject name: Radiology
[{'content': 'Puff of smoke is a feature of \nSelect and explain. \nA. Joube syndrome, B. Moya Moya disease, C. Both, D. None of the above', 'role': 'user'}, {'content': "Answer: B \nExplanation: Puff of smoke is a feature of Moya Moya disease on Angiography It is caused due to chronic vasospasm of supraclinoid pa of ICA. IVY'S SIGN- Prominent leptomeningeal collaterals in moya-moya disease result in vivid contrast enhancement and high signal on FLAIR due to slow flow. The appearance is reminiscent of the brain having been covered with ivy. Figure: Puff of smoke sign", 'role': 'assistant'}]