Sodium iodide, 131-I in isotonic solution (Sodium iodide, 131-I, in isotonic solution)

The drug "Sodium iodide,¹³¹I, in isotonic solution "is administered intravenously or orally (per os).

Radioiodine therapy

In the treatment of thyrotoxicosis in diffuse and multi-site toxic goiter, treatment is carried out 3-4 weeks after thyroidectomy or withdrawal L- thyroxine 20 days before the administration of the drug.Patients are transferred to specialized wards that are equipped with an autonomous ventilation and sewerage system connected to special treatment facilities. Patients are withdrawn from the "closed" regime when the gamma radiation power is reduced to the permissible level of radiation safety (3 μSv / h).

In the treatment of thyrotoxicosis, the amount of the drug administered is individually selected in the range from 111 to 555 MBq.

The main condition for conducting radioiodine therapy for thyroid cancer of its metastases is thyroidectomy. The period of treatment is no earlier than 4-6 weeks after surgery. The most optimal form for radioiodine therapy is the highly differentiated A-cellular thyroid cancer. Carrying out radioiodine therapy of metastases of B- and C-cell forms of thyroid cancer is inexpedient.

In the treatment of metastases of thyroid cancer, the drug is prescribed by mouth in an amount of 1850-3700 MBq once every 3 months. Before each re-appointment of the drug, an investigation is made of the iodine-absorption activity of metastases. For this purpose, scintigraphy or radioisotope scanning is used after the administration of 37-74 MBq of the preparation.Duration of treatment can reach 2 years, and the total dose of iodine-131 is 18.5 - 25.9 GBq.

Currently, there are two most common methods for calculating the input activity of iodine-131.

Individual calculation based on the volume of the thyroid gland, the rate of iodine uptake - 131 during the diagnostic scan 24 hours after taking the drug and the specified activity per gram of tissue (range from 0.1 to 0.3 MBq / g) according to the formula:

Av = (As x V)/(C x 10), where A3 is a given activity, MBq / g; V - volume of the thyroid gland, cm³; C - rate of iodine-131 capture after 24 hours after drug administration; 10 is the coefficient.

The purpose of the fixed activity of iodine is 131: 190 MBq - small glands, 380 MBq - medium-sized glands, 570 MBq - large glands. Before the beginning of treatment, preliminary determination of iodine-131 absorption by the thyroid gland is necessary, which guarantees the correctness of treatment, excludes the possibility of an error associated with the use of fixed activity in a patient with a large but poorly absorbing iodine 131 by the gland. In the therapeutic use of the drug, an obligatory condition is the constant monitoring of the state of peripheral blood.

Methods of research

Functional state of the thyroid gland can be estimated by:

- the level of protein-bound plasma iodine;

- results of radiometry of the whole body.

The iodine-131 value 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 - iodine-131 content in iron, imp / min, C-content of iodine-131 in standard, imp / min, Nf-background, imp / min.

In healthy people, in the thyroid gland, after 2 hours, an average of 14% of the added amount of isotope accumulates, after 4 hours - 19 %, in 24 hours - 27 %.

In order to determine 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 3 - 5 ml of blood plasma is transferred to a test tube and the protein is separated by adding three times a 10% solution of trichloroacetic acid in a volume equal to the volume of the blood 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, C - 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, the first measurement in geometry providing the necessary accuracy is carried out using a scintillation sensor with a diameter of 10 to 20 cm. 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 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%.

Radiation loads on the organs and tissues of the patient when using the drug "Sodium iodide,¹³¹I, in an isotonic solution of "

The effective equivalent dose (mSv / MBq) 0.072