Transverse CT image of the manual segmentation process of the area of the jugular foramen. Outlines of the bony boundaries of the JF were manually segmented and assigned to tissue label fields (A). The segmented areas are reconstructed to the jugular foramen volume (B). The dorsal boundary of the JF was set along a line following the straight contour of the basioccipital bone from its midline laterally. The ventral boundary was set along a line perpendicular to the first line through the ventro-medial margin of the JF (C). Multiplanar image reconstruction (D) helped to identify the internal boundaries of the JF.