This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Radiology
[{'content': 'This round hyperdense lesion on NC-CT located in the 3rd ventricle is most likely to be a: \nSelect and explain. \nA. Arachnoid cyst, B. Epidermoid cyst, C. Colloid cyst, D. Giant cell astrocytoma', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C Colloid cystAxial NC-CT scan shows a well-defined hyperdense round lesion in the 3rd ventricle which is classic for colloid cyst. This cyst can sometimes lead to obstruction of CSF flow with hydrocephalous. Appears hyperintense on T1W MRI due to high protein content.', 'role': 'assistant'}]