1. The inferior occipital gyrus is bound medially by the collateral sulcus and the posterior transverse collateral sulcus, laterally by the inferior occipital sulcus, and anteriorly by the occipital notch (temporo-occipital notch). A 3D reference model is necessary to delineate the IOG (Fig. 1, Fig. 2, Fig. 3, Fig. 5).
  2. Mask in the coronal view, starting at a slice that corresponds with the end of the temporo-occipital incisure. This slice can be determined by referencing the 3D model. In the 3D model, click at a point where the temporo-occiptial incisure ends (Fig. 1) and work off of its corresponding coronal slice (Fig. 6). In the coronal view, trace the collateral sulcus it its internal end and cut to the internal end of the inferior occipital sulcus, then completely trace the inferior occipital sulcus. Mask everything within (Fig. 6, Fig. 7, Fig. 8).
  3. Moving posteriorly, the collateral sulcus becomes the posterior transverse collateral sulcus. When this occurs continue to follow step 2 substituting the posterior transverse collateral sulcus for the collateral sulcus (Fig. 9, Fig. 10). Continue this step until the posterior transverse collateral sulcus is no longer visible.