阳江高本底地区女性居民甲状腺超声检查的结果与分析

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

目的 探索长期低剂量电离辐射对人群甲状腺结节发生的影响。方法 分别从高本底辐射地区（HBRA）的4个管区和对照地区（CA）的2个管区选择50岁以上女性居民中各100名，通过超声检查测量甲状腺结节的大小及直径；测量居民血压、身高及体重，通过问卷调查搜集个人生活史和居住史。同时，依据既往研究所测量的室内外环境地表γ剂量率及调查的年龄别居留因子并考虑居住史，估算个人终生累积剂量。采用STATA 11.0软件进行t检验、χ2检验及Logistic回归统计分析。结果 HBRA与CA居民的平均累计剂量分别为（162.5±38.1）和（43.7±7.3）mSv；平均年龄分别为（65.2±10.4）和（60.7±8.1）岁。经甲状腺超声检查结果显示，甲状腺结节检出率，HBRA高于CA，HBRA为70.2%、CA为51.0%。不同类型甲状腺结节中，实性甲状腺结节所占比例最高，HBRA为87.7%，CA为75.9%。将实性结节按其最大直径分组，调整年龄影响因素后，对于甲状腺实性小结节（〈15 mm）来讲，高本底地区为实性甲状腺结节风险增加的危险因素（其中直径〈10 mm的结节β回归系数=0.804，P〈0.05；直径为10~15 mm的结节β回归系数=1.277，P〈0.05）。个人累积剂量为甲状腺实性小结节（〈15 mm）发病的危险因素，并且随着累积剂量的增加其风险有增加的趋势。 结论 未见长期低剂量辐射对大结节有影响，但有增加实性甲状腺小结节（〈15 mm）发生风险的可能。

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.