Fig. 45-2. Approximately horizontal sections of the head as seen by imaging techniques: magnetic resonance imaging (MRI) and computerized tomography (CT). A, MRI. On each side, behind the globe, the orbital fat appears white. On the left side of the print, the slightly curved optic nerve is evident, lying between the lateral and medial recti. The peripheral white band represents mainly bone marrow within the skull. Internally, the temporal and occipital lobes of the cerebral hemispheres are visible. In or near the median plane, the nasal cavity and the ethmoidal and sphenoidal sinuses appear black, followed (in gray) by the hypophysial region and optic chiasma, the midbrain (which shows the aqueduct), and the cerebellum. B, CT. In each globe the lens can be seen, and, on the left side of the print, portions of the lateral rectus and optic nerve. The peripheral white band is the skull, outside which the auricles are visible. The greater wing of the sphenoid forms the lateral wall of the orbit and, further back, the squamous part of the temporal bone can be seen lateral to the temporal lobe. The petrous portion of the temporal bone proceeds anteromedially. Mastoid air cells show as black areas. In or near the median plane, the nasal cavity and the sphenoidal sinus appear black, followed by the dorsum sellae (in white) and, posteriorly, the internal occipital protuberance.