Inferior Frontal Gyrus Protocol

  1. The inferior frontal gyrus is bound by the inferior frontal sulcus inferiorly and the precentral sulcus anteriorly. Its inferior lateral boundary is the lateral aspect of the H shaped orbital sulcus. (Fig. 1, Fig. 2)
  2. Masking of the inferior frontal gyrus is done in the coronal view. Begin anteriorly where the lateral orbital sulcus first comes into view. At this point, draw a straight line from the internal end of the lateral orbital sulcus to the internal end of the inferior frontal sulcus. Mask everything within these boundaries. (Fig. 3)
  3. Moving posteriorly the transverse orbital sulcus will appear soon after step 2. At this point, draw a straight line from the internal end of the transverse orbital sulcus to the internal end of the inferior frontal sulcus. Mask everything within these boundaries. (Fig. 4)
  4. Moving posteriorly the H-shaped orbital sulcus comes into view. Mask from the lateral segment of the H-shaped orbital sulcus to the inferior frontal sulcus and fill in everything between these two sulci. (Fig. 5)
  5. Posteriorly, H-shaped orbital sulcus becomes less distinct. At this point, reference the previously masked slice to approximate its location. Draw a straight line between this approximated point and the inferior frontal sulcus. In addition be sure to exclude the temporal pole. Continue this step until the inferior frontal sulcus is no longer visible. (Fig. 6, Fig. 7)