Thyroid exposure to radioactive iodine is one of the most dangerous consequences of the notorious accident at the Chemobyl Nuclear Power Station in 1986, because iodine radionuclides were dominant components of the radioactive trail.Although the total dose of external gamma-radiation created by these radionuclides was relatively low, local exposure of thyroid was very significant, particularly in children. It should also be noted that most districts of 13ryansk region exposed to the radioactive trail are foci of endemic goiter caused by iodine deficiency of various origin [8, 9].Ultrasonic scanning provides new methods of thyroid volume evaluation [15], which should replace routine palpation, because palpation gives erroneous results in almost 30% of children [3].Ultrasonic assessment of thyroid size and measurements of iodine content in urine are presently the most effective methods of diagnosis of iodine deficiency [2].Various methods of ultrasonic scanning of thyroid volume in normal and pathological states are presently used in clinical practice. Therefore, the results on thyroid pathology published in the literature are difficult to compare.The goal of this work was to determine the capacity of ultrasonic scanning for testing the state of endemic goiter in children of the Bryansk region exposed to the radioactive trail ofthe Chernobyl Nuclear Power Station accident.
Materials and MethodsStatistical results on thyroid disease incidence in children in areas with different level of contamination with 131I [1] were used. Experiments were performed in the town of Novozybkov (reconstructed specific activity of 1311 on May 10, 1986 was 55.97 Ci/krn2), Navlya settlement (2.09 Ci/kmZ), and the town of Karachev (1.53 Ci/km2). Children were divided into two age groups: 1) 10-12 years (0-2 years at the time of the Chernobyl accident); 2) 13-15 years (3-5 years, respectively).Medison model Eurica SA-600 ultrasonic scanners with high-frequency (7.5 MHz) linear probes were used to study the structure and volume of the thyroid gland [7, 11].Iodine concentration in urine was measured by the cerium-arsenite method with preliminary wet ashing. Iodine content was expressed in ~g per 100 ml urine (lag %). The results of the study were statistically processed using standard epidemiological criteria of severity of iodine deficiency (Indicators from Assessing Iodine Deficiency Disorders and Their Control Programmes. Report of Joint WHO/UNISEF Consultations, November 3-5, 1992. Revised version. September 1993 WHO/NUT/93.1). Normal level of iodine excretion is 10-20 i.tg %. Iodine content in urine of patients with slight iodine deficiency is 5-10 lag %; medium iodine deficiency, 2-5 I~g %; and severe iodine deficiency, less than 2 i.tg %.If the thyroid volume increase was more than 97 percentile in 5-20%, 20-30%, or more than 30%, the extent of iodine deficiency was considered as light, medium, or severe, respectively.
Results and DiscussionAccording to urine tests, in children of the town of Novozybkov and Navlya settlement aged 10-...