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': 'Which of the following is used to differentiate between the arachnoid cyst and epidermoid cyst – \nSelect and explain. \nA. FLAIR, B. T1 weighted MRI, C. Smooth margin, D. Contrast enhancement', 'role': 'user'}, {'content': 'Answer: A \nExplanation: On MRI, diagnostic confusion occasionally arises between arachnoid cysts and epidermoid cysts. The two masses may have similar characteristics on T1-weighted and T2-weighted images, and neither shows enhancement with gadolinium.\nHowever, arachnoid cysts follow CSF signals on all sequences, in particular on FLAIR sequence, in contradistinction to the epidermoid cyst.\nDiffusion-weighted images (DWIs) allow easier differentiation of the two masses.', 'role': 'assistant'}]