Color enhanced CT cross section of the head at the level of the bones of the skull base. Bones are blue, air in the sinuses, ears and mastoid air cells are yellow. The eyes are seen towards the top of the image. This image shows a highly detailed view of the bones making up the base of the skull. The spaces within the bony structure which is black is air. The air is in the sphenoid sinus, ethmoid sinuses and in mastoid air cells on both sides. The internal carotid artery is also seen as a linear gray structure near the center of the image on both sides of the skull base.