High resolution computed tomography of the orbit withthe Ohio Nuclear Delta head scanner

The orbit is an ideal structure to examine by CT because of large differences between absorption values of retroorbital fat and other structures such as muscle, optic nerve, and ophthalmic artery. Spatial resolution in CT is dependent upon the volume of each pixel (individual picture element). Whereas the pixel volume of the original EMI scanner was 117 mm, that of the Ohio Nuclear Delta head scanner employed in this paper is only 5 mm. Ovver 200 patients have been examined using this scanning instrument, including 32 patients in whom the orbits were specifically examined with a scan plane parallel to Reid's baseline. Representative abnormalities are discussed and illustrated. Orbital tumors such as hemangiomas, lymphomas, meningiomas, and inflammatory pseudotumors can be accurately localized while still very small.