Thyroid scintigraphy (Tc-99m)

Last revised by Ammar Ashraf on 20 May 2023

Tc-99m pertechnetate thyroid scintigraphy (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 (i. e. ionic size and negative charge) - in the thyroid parenchyma is mediated by the NIS (sodium-iodide symporter, a transmembrane glycoprotein). 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

  • 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.

ADVERTISEMENT: Supporters see fewer/no ads