Figure 7a.  Rib counting at lateral chest radiography with the sternal angle as an anatomic landmark. (a) Diagram of the ribs and sternum (lateral view) shows the second costal cartilage attached to the sternal angle (*), which is characterized by a slight anterior convex angulation. The second rib (darkened area) courses upward obliquely. (b) Lateral chest radiograph shows the second rib (arrowheads) and costal cartilage attached to the sternal angle (*).