Analysis on the result of thyroid ultrasound examination in female residents in high background radiation area Yangjiang

Abstract

Objective To explore the effect of long-term low dose radiation exposure on thyroid noduls of people. Methods There were 100 female residents aged 50 or above selected each from four regions in the high background radiation area (HBRA) and two regions in the control area (CA). The number, size and form of thyroid nodule were measured by ultrasound examination. Other indicators like blood pressure, height and weight were also measured. Personal life and living history were collected through questionnaires. The estimation of individual lifetime accumulated radiation dose was based on the γ dose rate indoor and outdoor and the age-related occupancy factor that obtained from the previous studies. Multinomial Logistic regression model, chi-square test and t test were conducted through software Stata 11.0. Results The average age was (65.2±10.4) years for residents from HBRA and (60.7±8.1) years for residents from CA, the average accumulated radiation dose in HBRA and CA was (162.5±38.1)and (43.7±7.3) mSv, respectively. Through the thyroid ultrasound examination, the prevalence of thyroid nodules in HBRA was higher than that in CA, 70.2% and 51.0%, respectively. Among different type of thyroid nodules, the proportion of multiple solid nodules was highest, 87.7% in HBRA and, 75.9% in CA, respectively. The solid nodules were divided into different group according to the largest diameter of the nodule. For the solid nodule with<15 mm in diameter, after adjusting confounding factor age, HBRA was responsible a possible risk (for nodule with<10 mm in diameter β=0.804, P<0.05; while for 10-15 mm in diameter β=1.277, P<0.05). The accumulated radiation dose was a risk factor for small solid nodules with <15 mm in diameter, and the risk would increase with the increased accumulated radiation dose. Conclusions There was no effect tobe found on the large nodules from long-term low dose radiation exposure, however the increase in the risk of the small solid nodules (<15 mm in diameter) may be possible. Key words: Thyroid nodule; Long-term low dose radiation; The high background radiation area; Thyroid ultrasound examination