Radiographic appearance of a normal thymus gland in an infant

Anteroposterior view of the chest in a healthy 5-month old infant. The radiopaque paraspinal density just above the heart (arrow) represents the normal infant thymus gland. The left margin is slightly undulating, characteristic of the thymus, which is indented by adjacent costochondral cartilages (thymic wave sign). The lungs have mild, nonspecific increased bronchovascular markings bilaterally because the radiograph is not in full inspiration.