How is a parathyroid scan performed?

Parathyroid tissue is capable of concentrating Tl-201 chloride and Tc-99m sestamibi. Because thyroid tissue also concentrates these drugs, it is necessary to image the thyroid tissue by itself (using oral I-123 or intravenous Tc-99m pertechnetate) and then subtract (either digitally or visually) the image of the thyroid tissue. Alternatively, delayed Tc-99m sestamibi images at 1-3 hours may show retained tracer in parathyroid tissue.