Thyroid scintigraphy

What is thyroid scintigraphy? 

Scintigraphy is one of the methods for diagnosing thyroid diseases, based on the assessment of its accumulation of a pharmacological drug that contains the radioactive isotope technetium.

The relevance of the study is due to the uniqueness of the diagnostic information obtained, which sometimes plays a crucial role in determining the treatment tactics.

Scintigraphy allows us to judge the features of the structure and location of the thyroid gland, to identify its focal and diffuse changes, to identify and differentiate "hot "(hormonally active) and" cold " (functionally inactive) nodes of the gland.

To evaluate the activity of hormone secretion by the thyroid gland using scintigraphy is possible due to the fact that this organ produces iodine-containing hormones, so its need for this trace element is almost a hundred times higher than that of other body tissues.

How does it work? 

  To perform thyroid scintigraphy, the radioactive isotope technetium (Tc99) is used, which the thyroid gland absorbs as well as iodine, but technetium is excreted faster, since it is not used by the gland to produce thyroid hormones. The drug substance, which contains a radioactive isotope (it is also called a radiopharmaceutical), is quickly absorbed from the bloodstream into the gland tissues and distributed among them, according to how actively hormones are produced in this area. The area of active accumulation of radiopharmaceuticals is colored orange-red and is called a " hot " focus. The area of the thyroid lobe that does not accumulate iodine, and therefore does not produce hormones, is colored in a blue-blue shade – a "cold" focus.So, the detection of "cold" nodes most often indicates that the detected volume formation is a colloidal cyst, but in a small part of cases (about 5-7%), a tumor is hidden behind such a scintigraphic picture. "Hot" nodes are most often a reflection of such diseases as functional autonomy of the thyroid gland (or – toxic adenoma, which produces an excessive amount of hormones).

Indications for scintigraphy

• incorrect location of the gland;
• congenital anomalies of its development;
• nodal formation;
• thyrotoxicosis;

 How is the research conducted? 

 Before the study, a small dose of radiopharmaceutical (technetium Tc99) is administered intravenously to the patient, then its distribution is evaluated using a gamma camera-a special device that captures and records flashes from the isotope radiation that are invisible to the eyes.

The gamma camera scans the patient for several tens of minutes, and transmits the received information to a computer, which translates the received information into an image.

How to prepare for the procedure?

• A month before the procedure, it is necessary to stop taking medications containing iodine, if they are not prescribed for the treatment of diseases of the body.
• It is also not recommended to do other studies within three months that use radiopaque drugs (kidney urography, angiographic studies, magnetic resonance imaging with additional contrast). 

Is scintigraphy dangerous? 

Although radioactive isotopes are used for this study, the degree of radiation exposure during thyroid scintigraphy is so small that this method of research with technetium 99 can be carried out even in children of the first year of life.

The radiation load does not exceed the level of radioactive radiation that accompanies the chest X-ray or CT scan.

Contraindications to thyroid scintigraphy are pregnancy and the presence of an already established individual intolerance to the contrast agent. Nursing mothers can continue feeding the baby a day after the procedure is completed.

Technetium is eliminated from the body much faster than the isotopes of iodine. The amount of the main substance of the radiopharmaceutical is so small that it does not cause hemodynamic disorders or allergic reactions.