1. The gyrus rectus is located in the most medial and inferior region of the frontal lobe. Its boundaries are the olfactory sulcus inferiorly and the susorbital sulcus superiorly. (Fig. 1, Fig. 2)
  2. Masking of the gyrusrectus is done in the coronal view. Begin by locating the olfactory sulcus either in the coronal view or on the 3d object. (Fig. 3, Fig. 1) Follow the olfactory sulcus to its most posterior point in the coronal view, and mask from its internal end to the lowest medial sulcus. (Fig. 4) Continue this step until the olfactory sulcus is no longer visible, keeping the height of the gyrus fairly consistent. (Fig. 5, Fig. 6)