Fig. 5. A. Schematic showing positioning for a basal projection. (CR, central ray; IM, infraorbitomeatal line) B. Radiograph of a basal projection. (a, zygomatic arch; b, orbit; c, lateral orbital wall; d, posterior wall of maxillary sinus; e, pterygoid plate; f, sphenoid sinus) (A; Rao VM, Gonzalez CF: Plain film radiography and polytomography of the orbit. In Gonzalez CF, Becker MH, Flanagan JC [eds]: Diagnostic Imaging in Ophthalmology, pp 1–7. New York, Springer Verlag, 1986)