<prompt> Which of the following is used to differentiate between the arachnoid cyst and epidermoid cystFLAIRT1 weighted MRISmooth marginContrast enhancement  <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 the epidermoid cyst.Diffusion-weighted images DWIs allow easier differentiation of the two masses. 