The drug "Sodium iodide,131I "is administered orally.
Preparation of the patient. Research of the functional state of the thyroid gland should be carried out no earlier than 4-6 weeks after the withdrawal of preparations of stable iodine, iodine and iodinated foods and multivitamin preparations containing iodine, iodine-containing radiopaque agents, fluoride, bromine, triiodothyronine, thyroxine, thyroidin, 6-methylthiouracil and other similar antithyroid drugs, as well as glucocorticosteroids.
Radioiodine diagnostics. DTo study the function of the thyroid gland according to the accumulation value of 1-131, it is sufficient to introduce 0,037-0,074 MBq of the drug, when scanning the thyroid gland, determining protein-bound iodine, and studying the entire body by radiometry-0,111-0,185 MBq. 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 uses 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
AT - the content of iodine-131 in iron, imp / min, C-content of iodine-131 in the standard, imp / min, Nf - background, imp / min.
In healthy people, in the thyroid gland, after an average of 14 hours, an average of 14% of the added amount of isotope 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 after 48 hours a blood sample is taken from the ulnar vein (8-10 ml). After centrifugation, 4 to 5 ml of blood plasma is transferred to a test tube and the protein is separated by adding 3% of 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 in a 2M solution of caustic sodium or caustic potassium, leading to the original volume of blood plasma, and radiometric in the 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.
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
AT - content of iodine-131 in the sample, imp / min, FROM - volume of blood plasma taken for analysis, ml, D - iodine-131 content in the standard, imp / min, Nf - background, imp / min.
The normative level of protein-bound iodine is no more than 0.3% per liter. Radiometry of the whole body allows to evaluate the peripheral stage of the exchange of thyroid hormones and is carried out as follows. After 2 hours after taking 1.0 MBq of the drug, during which the patient is asked not to empty the bladder,is carried out with a scintillation sensor with a Diameter 10-20 cm the first measurement in geometry, providing the necessary accuracy. The results of this first radiometry are taken as 100%. Subsequently, the radiometry is repeated after 24, 72, 120 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 radiometry, iodine-131 subsequent terms in the thyroid glandeze and throughout the body, except for thyroid gland, as a percentage of the amount administered.
The iodine-131 content is normal in the body (excluding the thyroid gland) 10-25% after a day, 9.7-15% after 3 days, and 2-12% after 8 days. The method of radionuclide diagnosis of A-cell cancer and thyroid metastases involves scanning or scintigraphy of the entire body 24 and 48 hours after intravenous injection of 111-165 MBq of the drug.
Radiation loads on the organs and tissues of the patient when using the drug "Sodium iodide, 131I".
BODIES ................................................. ......... ABSORBED DOSE, mG p / MBq
stomach................................................. ..................... .34
red bone marrow ............................................... ........... 0.035
lungs................................................. ...................................... .031
the bladder ................................................ ...................... 0.61
liver ................................................. ..................................... 0.033
pancreas ................................................ ............ 0.03
kidneys ................................................. ...................................... .0655
spleen ................................................. .................................. .0344
small intestine ................................................ ............................ .038colon ................................................ ........................... .0
thyroid ................................................ ................ .029
testicles ................................................. ...................................... .042
ovaries ................................................. .................................. 0.037
Equivalent dose (mSv / MBq) ........................................... ... 0.037