For dental and facial imaging, a source of x-rays (14) or other penetrating radiation and a detector (20) are mounted opposite one another on a rotatable gantry (28), so that the head of the patient can be positioned between the source (14) and the detector (20), with the axis of rotation (36) of the gantry passing through the patient's head. The detector is longer in one direction than in the perpendicular direction, generally rectangular, and is rotatable between a position in which the long axis is transverse to the axis of rotation of the gantry and a position in which the long axis is generally parallel to the axis of rotation of the gantry. The length of the detector along the long axis is sufficient for fully detailed computed CT when the long axis is transverse, and for full-face CT when the long axis is parallel.