Figure 7b. Osteochondroma in a 39-year-old woman. (a) Axial contrast-enhanced CT scan at the level of the left atrium (A) shows a dense calcification (arrowhead) that projects medially from a right rib. (b) Axial T2-weighted (6,000/112) MR image of the right side of the chest wall obtained with a surface coil shows a cartilaginous apical cap (arrow), which has a slightly higher signal intensity than does muscle.