Procedure
The scintigraphy of the thyroid gland can be performed on an outpatient basis in a radiology practice or in the thyroid outpatient department of a radiology clinic. It is not necessary to be admitted to hospital for the examination. First, the doctor injects a liquid containing the radioactive substance into a vein, usually on the arm.
Radioactive iodine or iodine-like substances such as pertechnetate (radioactive element: technetium) are used here, which are incorporated into the thyroid just like iodine. Now you have to wait about ten to twenty minutes. During this time, the radioactive particles are distributed throughout the body with the blood and thus also reach the thyroid gland.
Almost exclusively there they are partially absorbed. Now the actual measurement is carried out by the so-called gamma camera, in front of which one usually sits down. This camera registers the radioactive radiation (gamma radiation) that now emanates from the thyroid gland.
If a patient cannot sit, the scintigraphy is performed while lying down. With the help of a computer, an image corresponding to the distribution of the radiation is created. In addition, the amount of administered radiation absorbed by the thyroid gland is measured.
This is the so-called “uptake”. The measurement itself takes about ten minutes and causes no pain, nausea or other discomfort. The result is usually directly available to the doctor and he can make initial statements.
A report with all information and the further procedure is then sent to the patient and the family doctor soon. After the examination you can go home again. However, contact with pregnant or breastfeeding women and children should be avoided for a few hours or at least some distance should be maintained, as the body still emits some radiation. However, this radiation decays continuously and is also excreted in the urine.
Evaluation/Values
The evaluation of the thyroid scintigraphy is initially performed on the basis of the image created. All areas of the butterfly-shaped organ are displayed in different colors. Blue tones stand for low and red tones for high activity of the tissue.
Thus, areas with increased or decreased activity can be determined by optical evaluation alone.The second important aspect of the evaluation are the scintigraphic values, which are usually given as TcTU (Technetium thyroidal uptake = Technetium uptake of the thyroid gland) in percent. This is the percentage of radioactivity (in the form of technetium) given with the syringe that was ultimately absorbed by the thyroid gland. In most cases the value is less than 2%. Together with the other findings, it helps the nuclear physician to assess a possible disease.
