The drug "Sodium iodide, -131I "is intended for oral administration.
To study the functions of the thyroid gland in terms of the accumulation of iodine-131, scintigraphy (scanning) of the thyroid gland, determination of protein-bound iodine, and the study of the peripheral stage of thyroid hormone metabolism, it is sufficient to introduce 0.06-0.60 MBq
Preparation of patient. The study of the functional state of the thyroid gland should be conducted no earlier than 2 weeks after the withdrawal of the use of stable iodine preparations, iodine and iodinated foods and multivitamin preparations (Centrum, Vitrum, Unicap, Multi-tabs , etc.), iodine-containing radiocontrast agents, fluoride, bromine, triiodothyronine, thyroxine, thyroidin, 6-methylthiouracil and other similar antithyroid drugs, as well as glucocorticosteroids
Methods of research.
Functional state of the thyroid gland can be estimated by:
- the amount of iodine-131 accumulation in the gland after 2, 4, 24 hours and at a later time after taking the drug;
- the level of protein-bound plasma iodine; results of radiometry of the whole body.
The accumulation of iodine-131 in the thyroid gland is the total index of the state of the inorganic and organic phases of iodine metabolism in this organ. The determination is made using a radiometer, placing the end of the sensor at a distance of 30 cm from the front surface of the neck. Radiometry standard, which is used as a capsule containing iodine-131, in an amount equal to the injected patient, is carried out under the same geometric conditions.
The percentage of radionuclide accumulation in the thyroid gland (A) is calculated by the formula:
A = (B - Nf) / (C - Nf) x 100%, where
B - iodine-131 content in iron, imp / min, C - iodine-131 content in standard, imp / min, Nf - background, imp / min.
In healthy people, in the thyroid gland, after an average of 10 hours, an average of 10% of the administered amount of radionuclide accumulates, after 4 hours - 19%, after 24 hours - 27%, and after 10 days 6-12% of the administered amount of iodine-131.
With the aim of determination of the level of protein-bound iodine in a patient 48 hours after the administration of the drug, a blood sample (8-10 ml) is taken from the ulnar vein.After centrifugation, 4-5 ml of plasma is transferred to a test tube and the protein is separated by adding triplicate 10% trichloroacetic acid solution in a volume equal to the volume of the plasma to be analyzed, followed by centrifugation at 2000 rpm for 10 minutes. The resulting precipitate is dissolved to the original volume of plasma in a 2M solution of sodium or potassium hydroxide and is metered in a well counter in parallel with the standard. As the latter, a solution of iodine-131 diluted in a ratio of 1: 500 is used; the volume of the standard should be equal to the volume of plasma taken for radiometry. Preparation of the standard is carried out by dissolving the capsule in hot water.
The percentage of protein-bound iodine (A) is calculated by the formula:
A = [(B - Nf) x 1000 x 100 / C x (D - Nf)] x 500% / l, where
B - content of iodine-131 in the sample, imp / min, C - volume of plasma taken for analysis, ml, D - content of iodine-131 in the standard, imp / min, Nf ) - background, imp / min. |
The normal level of protein-bound iodine is no more than 0.3% / l.
The peripheral stage of the exchange of thyroid hormones is carried out by radiometry of the whole body and is carried out as follows. After 2 hours after taking 1 MBq of the drug, during which the patient is asked not to empty the bladder,Scintillation probe with a diameter of 10-20 cm is carried out with a first measurement in geometry that ensures the necessary accuracy. These results are taken as 100%. Subsequently, the radiometry is repeated after 24, 72 and 192 hours. The registration is carried out every time with both a shielding of the neck (thyroid) region with a lead plate 4-5 cm thick, and without screening. Based on the results of radiometry, the iodine-131 content is calculated in subsequent terms in the thyroid gland and in the whole body, except for the thyroid gland, as a percentage of the amount administered. The iodine-131 content is normal in the body (excluding the thyroid gland) in a day -10-25%, after 3 days - 9.7-15%, after 8 days - 2-12%.