Figure 1. Chest wall measurements. Fast TurboFLASH axial image with measurements of the skeletal extent of pectus excavatum deformity. Pectus Index=b/a; chest flatness=b/c; mean anteroposterior chest wall movement=100[(c_i/c_e)+(c'_i/c'_e)-2]/2, where the subscripts i and e are the full inspiratory and expiratory measurements, respectively. a, minimum sternovertebral distance (minimum anteroposterior diameter) at the level of greatest deformity; b, maximum internal transverse diameter of the thorax; c and c', maximum anteroposterior rib diameters on the right and left sides, respectively, at the level of greatest deformity.