Optimal positioning for CT examinations of the skull base. Experimental and clinical studies.

To evaluate the most appropriate CT angles for the skull base, four adult phantom skulls of various shapes were examined by CT. 15 osseous sites in each skull base were selected and the optimum angle for their delineation was determined. Using Reid's base line (0 degree), many sites could be imaged best at angles up to +20 degrees, and +10 degrees was found to be optimum. Examinations of patients using OM-line as a reference disclosed imaging rates in excess of 70% for sites other than the hypoglossal canal, the optic canal and foramen rotundum, which are in horizontal planes.