Thyroid scintigraphy is a nuclear medicine method that displays the thyroid gland and thyroid tissue functioning anywhere in the body. Thyroid scintigraphy provides information about the anatomy and function of the thyroid gland.  The radioactive materials routinely used in thyroid scintigraphy are technetium and iodine.  Since very low dose of radioactive material is used, there is no harm, but scintigraphic examination is not performed for pregnants.

When thyroid nodule is identified, thyroid function is determined by analysing thyroid hormones. The next step is to evaluate the nodules by ultrasonography and to perform needle biopsy for suspicious nodule, if any. Thyroid scintigraphy  is not requested in each patient with the identified nodule. T Thyroid scintigraphy should be requested for the differential diagnosis of hyperthyroidism in patients with low TSH levels. The appearance of a "cold nodule" in a thyroid scintigraphy should not cause a cancer panic in patients, because 80% of benign nodules are visualized as cold nodules.

When a patient with a thyroid nodule has a low level of TSH, a scintigraphic examination is performed. This examination helps visualize a nodule/nodules that may cause hyperthyroidism. Also, thyroid scintigraphy may sometimes be required in the diagnosis of thyroid diseases. While there is little radioactive substance uptake in hashimatosis, substance uptake is very high in toxic goiter species such as Graves.


Hot (hyperactive) nodules

  • Hot nodules are the nodules visualized in scintigraphy with more intense radioactivity than the surrounding tissue. Hot nodules account for 5% of all nodules.
  • Hot nodules are also seen in single or multiple toxic goitre.
  • Hot nodules may cause hyperthyroidism. Not every hot nodule causes hyperthyroidism.
  • The risk of cancer is very low. 

      

Cold (hypoactive) nodules

  • Cold nodules are the nodules that do not show radioactive substance uptake in scintigraphy compared to the surrounding tissue and account for 85% of all nodules.                          
  • Thyroid is benign nodules and thyroid cancers are visualized as cold nodules. Every cold nodule is not cancer.
  • Malignancy rate of cold nodules is 15-20%       

Normoactive nodules

  • Nodule shows same activity uptake with the surrounding tissue in the scintigraphy.
  • Normoactive nodule accounts for about 10% of all thyroid nodules.
  • Normoactive nodules are like cold nodules in terms of risk of cancer.