Radionuclide imaging of the parathyroid glands: patterns, pearls, and pitfalls

Optimal parathyroid scintigraphy requires an understanding of (a) the embryologic, anatomic, and physiologic features of the parathyroid glands and (b) the properties of the two common imaging agents, technetium-99m sestamibi and Tc-99m tetrofosmin. Normal parathyroid glands are too small to be visualized, but parathyroid disease often produces visibly enlarged glands. Enlarged parathyroid glands may be found near the thyroid gland or outside their expected locations. Characteristic abnormal scintigraphic patterns may be described as focal or multifocal, usual or ectopic in location, and associated with a normal or abnormal thyroid gland. Patients who are referred for parathyroid imaging should have an abnormal biochemical profile. The first step in evaluating images of a patient suspected to have parathyroid disease is correlating the normal or abnormal scintigraphic patterns with the clinical and surgical history. By integrating the interpretative and technical pearls and pitfalls of parathyroid scintigraphy, the radiologist can be more confident in establishing a correct diagnosis and can precisely guide the surgeon to a single parathyroid adenoma, multiple parathyroid adenomas, or multigland hyperplasia.