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
In cerebral angiography, the dye is injected through – 
Select and explain. 
A. Femoral artery, B. Brachial artery, C. Axillary artery, D. Radial artery
A: Femoral artery
Answer: A: Femoral artery 
Explanation: 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.
However, arachnoid cysts follow CSF signals on all sequences, in particular on FLAIR sequence, in contradistinction to epidermoid cyst.
Diffusion-weighted images (DWIs) allow easier differentiation of the two masses.