thyroid scan (Tc-99m)

Tc-99m pertechnetate thyroid scan is a functional nuclear medicine study used to assess the thyroid gland. The uptake of the pertechnetate anion - similar in chemical-physical characteristics to the iodide ion - in the thyroid parenchyma is mediated by the NIS (Sodium-Iodide Symporter). However, unlike iodine, pertechnetate anion is not incorporated into thyroid hormones.


  • patient preparation
    • fast for 4 hours prior to exam
  • radiopharmaceutical
  • dose and route of administration
  • time of imaging
    • 20 minutes after Tc-99m pertechnetate administration
  • equipment
    • camera: gamma camera
    • collimator: pinhole
    • window: 20% energy window centered at 140 KeV
  • procedure
    • obtain anterior, LAO, and RAO views
    • mark chin, suprasternal notch, palpable nodules, and surgical scars


Radiotracer uptake on the thyroid scan needs to be interpreted with biochemical thyroid function tests and thyroid antibodies (e.g. antithyroglobulin, antimicrosomal, thyrotropin receptor). The combination of these results can usually distinguish between the causes of thyroid dysfunction.

Increased uptake
Normal uptake
Decreased uptake
Abnormal site of uptake

See also

Siehe auch: