get smb/smth out of one's mind/head

(from Idioms in Speech)

to stop thinking about somebody (something), to dismiss somebody (something) from one's mind

Charles knew that he would never get that smile out of his mind again. (J. Wain)

I wish you'd get Dr. Hasselbacher out of your head. (Gr. Greene)

Jane Gallagher. Jesus. I couldn't get her off my mind. (J. Salinger)