Figure 2. (a) Typical CT appearance of a parathyroid adenoma in a 67-year-old man. Contrast-enhanced axial helical CT-scanning (window width 440 H, level 40 H, collimation 5 mm) revealing a significantly enhanced nodule, 21 x 11 mm in size, posterior to the inferior aspect of the right thyroid lobe (arrow). (b) Helical CT image (window width 370 H, level 40 H, collimation 5 mm) from a 42-year-old woman showing a retrotracheal parathyroid adenoma (arrow) of the right inferior parathyroid gland, 17 x 18 mm in size.