<prompt> In cerebral angiography, the dye is injected throughFemoral arteryBrachial arteryAxillary arteryRadial artery  <response>: 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. 