Non-cancer thyroid diseases among children in the Kaluga and Bryansk regions of the Russian Federation exposed to radiation following the Chernobyl accident.

This paper presents results of estimated radiation risks of non-cancer thyroid diseases in the people from Kaluga and Bryansk regions of the Russian Federation exposed in their childhood to radioiodine as a result of the Chernobyl accident. This work was carried out under the Joint Medical Research Project on non-cancer thyroid diseases conducted by Sasakawa Memorial Health Foundation and the Medical Radiological Research Center of the Russian Academy of Medical Sciences. The subjects were 2,457 people who underwent health examinations from 1997 to the end of 1999 who had individual radiometric thyroid data obtained between May and June 1986 and were aged 10 y or less at the time of exposure. The thyroid absorbed doses from incorporated 131I were estimated on the basis of measurements of exposure dose rate in the vicinity of the subject's thyroid and liver. A compartment model accounting for 131I metabolism in humans and cows was used. The estimated dose varied from 0 to 6 Gy, and its distribution was approximately lognormal with a mean of 0.132 Gy and standard deviation of 0.45 Gy. The prevalence of diffuse goiter in males showed a significant dose-response (p = 0.03) with an estimated odds ratio 1.36 at 1 Gy.

Comparing risk estimates following diagnostic CT radiation exposures employing different methodological approaches.

The current study has two aims: the first is to quantify the difference between radiation risks estimated with the use of organ or effective doses, particularly when planning pediatric and adult computed tomography (CT) examinations. The second aim is to determine the method of calculating organ doses and cancer risk using dose-length product (DLP) for typical routine CT examinations. In both cases, the radiation-induced cancer risks from medical CT examinations were evaluated as a function of gender and age. Lifetime attributable risk values from CT scanning were estimated with the use of ICRP (Publication 103) risk models and Russian national medical statistics data. For populations under the age of 50 y, the risk estimates based on organ doses usually are 30% higher than estimates based on effective doses. In older populations, the difference can be up to a factor of 2.5. The typical distributions of organ doses were defined for Chest Routine, Abdominal Routine, and Head Routine examinations. The distributions of organ doses were dependent on the anatomical region of scanning. The most exposed organs/tissues were thyroid, breast, esophagus, and lungs in cases of Chest Routine examination; liver, stomach, colon, ovaries, and bladder in cases of Abdominal Routine examination; and brain for Head Routine examinations. The conversion factors for calculation of typical organ doses or tissues at risk using DLP were determined. Lifetime attributable risk of cancer estimated with organ doses calculated from DLP was compared with the risk estimated on the basis of organ doses measured with the use of silicon photodiode dosimeters. The estimated difference in LAR is less than 29%.