Thyroid Dose Research Articles

Evaluating dose distributions of normal organs for patients undergoing VMAT therapy of nasopharyngeal carcinoma using Rando phantom and TLD-100H.

BACKGROUND: The routine radiation therapy treatment planning does not include secondary radiation and peripheral doses resulting from radiotherapy exposure in patients with nasopharyngeal carcinoma (NPC) undergoing Volumetric Modulated Arc Therapy (VMAT) using an linear accelerator (linac) of Axesse (Elekta 2538).OBJECTIVE: VMAT has a better dose conformity of the tumor and is also operated by adjusting the shapes of mulileaf collimator. However, such treatment is potentially important to improve the accuracy of estimated health risks.METHODS:This study aimed to evaluate the equivalent dose of organ or tissue () and effective dose () for normal organs using the Alderson Rando phantom as an equivalent of the human body. Thermoluminescent dosimeters (TLD-100H) were calibrated by 6 MV X-ray originated by the linac. A total of 252 TLDs were used. These TLDs were inserted into phantom organ or tissue which closely approximated to these places.RESULTS: The thyroid dose () had the highest dose, 1840 202 mSv/treatment. The of the Rando was 7.11 0.61 mSv/treatment, as estimated using ICRP 103. The skin doses () varied significantly outside the treatment field and decreased as the distance from the treatment field increased.CONCLUSIONS: This study can be referred to practical guidance regarding radiation protections of the public.

Entrance Surface Dose Measurement at Thyroid and Parotid Gland Regions in Cone-Beam Computed Tomography and Panoramic Radiography

Purpose: Ionizing radiation-absorbed doses is a crucial concern in Cone-Beam Computed Tomography (CBCT) and panoramic radiography. This study aimed to evaluate and compare the Entrance Skin Doses (ESD) of thyroid and parotid gland regions in CBCT and panoramic radiography in Yazd province, Iran.
 Materials and Methods: In this cross-sectional study, 332 patients were included, who were then divided into two age groups (adult and pediatric) and underwent dental CBCT and panoramic radiography. Twelve Thermoluminescence Dosimeters (TLD- GR200) were used for each patient to measure the ESD of thyroid and parotid glands. The differences between the ESD values in CBCT and panoramic examinations as well as between the adults and children groups were evaluated by one-way ANOVA and Man-Whitney tests.
 Results: The mean and Standard Deviation (SD) values of ESD in panoramic imaging were equal to 61 ± 4 and 290 ± 12 µGy for the thyroid and parotid glands of the adult groups, respectively. Notably, these values for CBCT were significantly higher (P<0.01), as 377 ± 139 and 1554 ± 177 µGy, respectively. Moreover, the mean ESD values in the panoramic examination were 41 ± 3 and 190 ± 16 µGy for thyroid and parotid glands for the children group, while they were 350 ± 120 and 990 ± 107 µGy in CBCT (P<0.01), respectively. The ESD values in the parotid gland were approximately 3.4 (2.8-4.1) and 4.7 (4.6-4.8) times greater than those for CBCT and panoramic examinations, respectively.
 Conclusion: Although CBCT provides supplementary diagnostic advantages, the thyroid and parotid glands’ doses are higher than panoramic radiography. Therefore, the risks and benefits of each method should be considered before their prescription.

Effective population monitoring for determination of the thyroidal radioiodine content of the public following a nuclear accident in Japan

After a nuclear accident, population monitoring is necessary to determine the radiation exposure levels of the affected population. One of the monitoring components is direct thyroid measurements to assess the internal thyroid dose (mainly from 131I with a relatively short physical half-life: 8.02 days). These measurements are particularly important for young children but were not adequately performed after the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Herein we propose a feasible and robust method to obtain as much reliable human data as possible for the dose reconstructions following a nuclear accident. The method employs three types of measurements: simplified, additional, and detailed measurements. The simplified measurements are performed using conventional NaI(Tl) survey meters to quickly triage heavily exposed individuals. The additional measurements are conducted using mobile whole-body counters to detect cesium (Cs; with longer retention in the body) as a tracer of 131I. And the detailed measurements are taken using spectrometric devices; they provide the most reliable data and are used to confirm the other measurements. We also discussed the target subjects and the monitoring period based on the experiences gained following the FDNPP accident. The early post-nuclear-accident phase is the most important period for the dose reconstruction for the affected populations; however, it is also the most challenging period in terms of allocating the necessary monitoring resources. It is thus vital that all countries that operate nuclear power plants establish and maintain a system for nuclear emergency preparedness and response.

Association between exposure to radioactive iodine after the Chernobyl accident and thyroid volume in Belarus 10-15\u2009years later

BackgroundWhile there is a robust literature on environmental exposure to iodine-131 (131I) in childhood and adolescence and the risk of thyroid cancer and benign nodules, little is known about its effects on thyroid volume.MethodsTo assess the effect of 131I dose to the thyroid on the volume of the thyroid gland, we examined the data from the baseline screening of the Belarusian-American Cohort Study of residents of Belarus who were exposed to the Chernobyl fallout at ages ≤18 years. Thyroid dose estimates were based on individual thyroid activity measurements made shortly after the accident and dosimetric data from questionnaires obtained 10-15 years later at baseline screening. During baseline screening, thyroid gland volume was assessed from thyroid ultrasound measurements. The association between radiation dose and thyroid volume was modeled using linear regression where radiation dose was expressed with power terms to address non-linearity. The model was adjusted for attained age, sex, and place of residence, and their modifying effects were examined.ResultsThe analysis was based on 10,703 subjects. We found a statistically significant positive association between radiation dose and thyroid volume (P < 0.001). Heterogeneity of association was observed by attained age (P < 0.001) with statistically significant association remaining only in the subgroup of ≥18 years at screening (P < 0.001). For this group, increase in dose from 0.0005 to 0.15 Gy was associated with a 1.27 ml (95% CI: 0.46, 2.07) increase in thyroid volume. The estimated effect did not change with increasing doses above 0.15 Gy.ConclusionsThis is the first study to examine the association between 131I dose to the thyroid gland and thyroid volume in a population of individuals exposed during childhood and systematically screened 10-15 years later. It provides evidence for a moderate statistically significant increase in thyroid volume among those who were ≥ 18 years at screening. Given that this effect was observed at very low doses and was restricted to a narrow dose range, further studies are necessary to better understand the effect.

Оценки неопределённостей доз внешнего и внутреннего облучения населения в загрязнённых областях РФ после аварии на ЧАЭС на основе инструментальных данных

The paper presents the results estimation of uncertainties in doses to the thyroid, from external and internal exposure to radiation following the Chernobyl accident. For the estimation the data-base of radiometry activities of Cs-134+137 in the body and I-131 to the thyroid in 1986 for 28,311 residents of Kaluga region and 16,470 residents of Bryansk region. Whole body radiation spectrome-try measurements made for 167,325 residents of Bryansk region from 1990 through 1994 were used. The computational model for reassessment of I-131 activities into individual exposure doses is an analytical relationship that describes the relative dynamics of radionuclide activities in a chain consisting “vegetation”, “milk”, “thyroid” and “inside the human body”, that is the chain of successive single-chamber models with time-constant transition rates between chambers and depending on the age of a person after single deposition of radionuclides on vegetation. The dy-namics of specific activities of I-131, Cs-134+137 in the vegetation chamber is calculated according to the agroclimatic model, with account of the dynamics of precipitation, the growth of forage and food vegetation biomass according to the data of the annual variation of average daily air tem-peratures in the surface layer of the atmosphere. The official methodology was used to calculate external exposure doses and reassess whole body radiation spectrometry measurements into in-ternal exposure doses. Based on the results of the studies, uncertainty estimates were obtained in terms of standard geometric deviations in the year of the accident – for individual, average in populated areas and integral dose estimates: (minimum/average/maximum) doses of internal thyroid and whole body exposure, respectively (1.1/2,0/3.0), (1.2/1.5/2.3) and (1.3/2.9/3.3); for doses since 1987, respectively (1.2/1.9/4.0), (1.2/1.9/2.1) and (1.4/5.2/8.2). The uncertainty of the calculation model for internal doses since 1987 is estimated at 2.1 times; the uncertainties estimated from the data of individual dosimetry of external and internal exposure of the population with the allocation of critical groups are equal to 1.5 and (1.9-2.2) times, respectively.

Thyroid Dose Reduction Using an X-Ray Shield Which is Artifact-Free During Fast Chest Ct Examinations

Thyroid Dose Reduction Using an X-Ray Shield Which is Artifact-Free During Fast Chest Ct Examinations

Reconstruction of thyroid doses after the Great east-Japan earthquake and tsunami in 2011

Reconstruction of thyroid doses after the Great east-Japan earthquake and tsunami in 2011

Comparison of early forecasts of the incidence of thyroid cancer in residents of the Russian Federation after the Chernobyl accident with observational data

A review of methods for assessing doses in the thyroid gland, predictions of the long-term consequences of its irradiation and the actual incidence of thyroid cancer in residents of four regions of the Russian Federation with the most significant radioactive fallout after the Chernobyl accident are presented. The method for assessing doses in the thyroid gland is based on the results of monitoring in May-June 1986 of radioiodine in the environment, food and in the body of residents. Thyroid doses in the population were used to justify medical and social protection measures, as well as epidemiological studies. In addition, the authorities needed forecasts of the possible morbidity of the population in order to organize adequate medical care. Most of the thyroid cancer cases were predicted among the adult population, which was not confirmed by observations 35 years after the accident. The prognosis of the incidence of thyroid cancer in preschool children differed in different studies due to the use of different coefficients of reducing the biological effectiveness of 131I radiation in the thyroid gland and long-term external and internal irradiation of the whole body with a low dose rate compared to the effect of acute exposure. The increase in the incidence of thyroid cancer among children began five years after the accident at the Chernobyl nuclear power plant. Examples of the dynamics of the incidence for children in the Bryansk region of the Russian Federation are given. The 2018 UNSCEAR Report showed that for 1986-2015, among children and adolescents under 18 years of age on the day of the accident in Belarus, Ukraine and four regions of Russia, more than 19 thousand thyroid cancer cases were detected, of which the share of radiation-induced diseases was estimated at 25%. For four regions of Russia, this amounts to 460 cases with a range of possible estimates from 130 to 900 cases. The highest morbidity was manifested among younger children exposed at the age of 0-4 years. In older children and adolescents, the proportion of radiation-induced diseases has significantly decreased 30 years after the accident. In general, early forecasts of radiation-induced thyroid cancer incidence in children in four regions of the Russian Federation with high levels of radioactive fallout are consistent with the data of subsequent 30-year epidemiological observations within an order of magnitude. With regard to thyroid cancer in adults, such a comparison is difficult, since no radiogenic increase in the incidence has been detected.

Age-Specific Thyroid Internal Dose Estimation for Koreans

Background: The International Commission on Radiological Protection is preparing to provide reference dose coefficients for environmental radioiodine intake based on newly developed age-specific biokinetic models. However, the biokinetics of iodine has been reported to be strongly dependent on the dietary intake of stable iodine; for example, the thyroidal uptake of iodine may be substantially lower in iodine-rich regions than in iodine-deficient regions. Therefore, this study attempted to establish a system of age-specific thyroid dose estimation for South Koreans, whose daily iodine intakes are significantly higher than that of the world population.Materials and Methods: Korean age-specific biokinetic parameters and thyroid masses were derived based on the previously developed Korean adult model and the Korean anatomical reference data for adults, respectively. This study complied with the principles used in the development of age-specific biokinetic models for world population and used the ratios of baseline values for each age group relative to the value for adults to derive age-specific values.Results and Discussion: Biokinetic model predictions based on the Korean age-specific parameters showed significant differences in iodine behaviors in the body compared to those predicted using the model for the world population. In particular, the Korean age-specific thyroid dose coefficients for 129I and 131I were considerably lower than those calculated for the world population (25%–76% of the values for the world population).Conclusion: These differences stress the need for Korean-specific internal dose assessments for infants and children, which can be achieved by using the data calculated in this study.

Risk of thyroid cancer in Ukrainian cleanup workers following the Chornobyl accident.

Although much is known about the radiation-related risk of thyroid cancer in those exposed at young ages, less is known about the risk due to adult exposure, particularly in men. We aimed to examine the association between thyroid radiation dose received during adulthood and thyroid cancer risk in men. We conducted a nested case-control study (149 cases; 458 controls) of male, Ukrainian cleanup workers who first worked in the Chornobyl zone between ages 18 and 59years, with cases identified through linkage with the National Cancer Registry of Ukraine from 1988 to 2012. Individual thyroid doses due to external and internal exposure during the cleanup mission and during residence in contaminated settlements were estimated (total dose mean 199mGy; range 0.15mGy to 9.0Gy). The excess odds ratio per gray (EOR/Gy) for overall thyroid cancer was 0.40 (95% CI: - 0.05, 1.48; p-value = 0.118). Time since exposure was borderline significant (p-value = 0.061) in modifying this association so that less time since exposure was associated with a stronger EOR/Gy. An elevated, but nonsignificant association was observed for follicular thyroid cancer (EOR/Gy = 1.72; 95% CI: - 0.25, 13.69; p-value = 0.155) based on a small number of cases (n = 24). Our findings for radiation-related overall thyroid cancer risk are consistent with evidence of increased risks observed in most of the other studies of adult exposure, though the magnitude of the effect in this study is lower than in the previous case-control study of Chornobyl cleanup workers.

Potential risks of cardiovascular and cerebrovascular disease and cancer due to cumulative doses received from diagnostic CT scans?

Potential risks from radiation exposure on the development of cardiovascular and cerebrovascular disease are indicated by epidemiological studies. Medical exposures give the largest dose to the population from artificial sources, with cumulative doses from multiple CT scans being significant. Data on doses from scans performed on 12 CT scanners in three hospitals over a period of 5½ years, derived using RadimetricsTM software, have been reviewed for 105 757 patients. Data have been downloaded for heart, brain, thyroid, and effective doses, and cumulative doses analysed using ExcelTM spreadsheets. 2.4% of patients having body CT scans received cumulative doses to the heart over 100 mSv, 9% of whom were under 50 years. 9.6% of patients having head CT scans received cumulative doses to the brain over 100 mSv with 0.08% over 500 mSv from whom 41% were under 50 years, but only 1.3% of patients scanned had thyroid/carotid artery doses over 100 mSv. An approximate evaluation of potential risks from exposures of the heart above 100 mSv and brain over 500 mSv for patients under 60 years would suggest that at most only one patient would demonstrate any excess risk from vascular disease resulting from the exposures. 0.67% of patients scanned received effective doses over 100 mSv, in line with results from European studies, with 8.4% being under 50 years. The application of age and sex specific risk coefficients relating to excess cancer incidence suggests that two or three patients with effective doses over 100 mSv and five patients with effective doses between 50 and 100 mSv, from those examined, might develop cancer as a result of exposure. However, this will be an overestimate, since it does not take patients’ health into account. Exposure management software can aid in evaluating cumulative doses and identifying individual patients receiving substantial doses from repetitive imaging.

Thyroid-optimized and thyroid-sparing radiotherapy in oral cavity and oropharyngeal carcinoma: A dosimetric study.

Radiation-induced hypothyroidism is a common toxicity of head and neck radiation. Our re-planning study aimed to reduce thyroid dose while maintaining target coverage with IMRT. We retrospectively identified patients with oral-cavity (n=5) and oropharyngeal cancer (n=5). Treatment plans were re-optimized with 45Gy thyroid mean dose constraint, then we cropped the thyroid out of PTVs and further reduced thyroid dose. Target coverage was delivering 100% dose to≥93% of PTV and 95% of dose to>99% of PTV. Originally, average mean dose to thyroid was 5580cGy. In model I, this dropped to 4325cGy (p<0.0001). In model II, average mean dose was reduced to 3154cGy (p<0.0001). For PTV low and PTV int, all had acceptable target coverage. In patients with oral-cavity and oropharyngeal cancers, mean dose could be significantly reduced using a thyroid-optimized or thyroid-sparing IMRT technique with adequate coverage.

Initial Plan Quality Evaluation Using a Novel AI-Driven Planning System and Paradigm for Adaptive Head and Neck Patients

An innovative ring gantry CBCT-guided adaptive radiotherapy system enables efficient planning and online adaptation to account for interfraction changes. Initial planning strategies and plan quality for head and neck (H&N) patients using the artificial intelligence (AI) plan optimizer for this system are evaluated.Nine previously treated H&N patients are used in this study. Planning target volumes (PTVs) have prescribed dose levels: PTVhigh = 70.0/69.3/66.0, PTVmed = 63.0/60, and PTVlow = 56.0/54.1/54.0/52.8 Gy. Clinical planning CT and structures are used for AI plan generation with the novel paradigm based on clinical goal prioritization. The system automatically optimizes 5 candidates plans: 7/9/12 equidistant field IMRT and 2/3 full arc VMAT. Three planning approaches are tested: 1) input physician goals; 2) prioritize PTV coverage by excluding organ at risk (OAR) goals when OAR intersects PTVs; 3) generate and assign goals to OAR subvolumes cropped from PTVs. Utility of generalized helper structures for controlling hot spot location and low dose spillage is investigated. The best of each patient's 5 candidate AI plans (AcurosXB) is compared to clinical (collapsed cone) plan using NRG guidelines.Strategies 1 and 2 consistently result in PTV under-coverage, high PTV hot spots, and failed OAR goals when intersecting PTVs. Strategy 3 provides acceptable PTV coverage and OAR dosimetry comparable to clinical plans. Helper structures (posterior block, distal OAR subvolumes, and PTVmed/low cropped from PTVhigh) were found to be necessary for shaping dose distributions similarly to clinical plans. Optimal plan type varied: 12 (n = 5), 9 (n = 2), 7 (n = 1) field IMRT and 3 arc VMAT (n = 1). Comparison of AI and clinical plans is based on using strategy (3) with helper structures. Compared to clinical plans, for all PTVs, average D99%, D95%, and Dmax are higher by 3.1% (103.6% vs. 100.5%), 1.3% (102.2 vs. 100.9%), and 3.3% (108.8% vs. 105.5%), respectively, but still within NRG guidelines. However, global hot spots may fall outside of PTVs and are higher by 5%. Hot spot differences may be from differences in dose calculation algorithms. The spinal cord, brainstem, parotid, oral cavity, mandible and thyroid doses are below NRG guidelines for both plans, with AI plan doses slightly lower. Larynx, Pharynx and submandibular doses on average are higher than the NRG guidelines due to PTV proximity for both plans, with AI plan doses slightly higher.The AI plan optimizer for this adaptive platform utilizes a novel planning paradigm based on clinical goals rather than direct optimization parameters and can efficiently generate H&N treatment plans. AI plans are comparable to clinical plans with slightly better PTV coverage and lower OAR doses. However, issues with higher and spatially undesirable calculated hot spots remain. All plans meet NRG guidelines.

Evaluation of Risk Factors for Developing Hypothyroidism Following Radiation Therapy for Head and Neck Cancers

<h3>Purpose/Objective(s)</h3> Hypothyroidism is a frequent late complication of Head and Neck radiotherapy. We sought to determine the incidence and risk factors for developing hypothyroidism after intensity modulated radiation therapy (IMRT) in patients with locally advanced head-and-neck cancer. We explored the hypothesis that baseline clinical characteristics and treatment factors would correlate with the development of hypothyroid. <h3>Materials/Methods</h3> We conducted an IRB approved retrospective review of patients with locally advanced head-and-neck cancer treated with radiotherapy at our institution. We determined the incidence as well as time to development of hypothyroidism defined as the initiation of hormone replacement or TSH value greater than 2-fold the normal assay limit. We then evaluated baseline clinical features including age, gender, tumor stage, tumor site in addition to clinical treatment factors including surgery, chemotherapy, and radiation dose for correlation with the development of hypothyroidism. <h3>Results</h3> We initially identified 207 subjects who completed radiation therapy between January 2015 and December 2017. We excluded patients who had hypothyroidism diagnosed before treatment, thyroid cancer, thyroidectomy or incomplete records yielding 147 evaluable patients with median follow-up time of 1.8 years. 77% of patients were male with mean age of 61 years (range 18-89). 58 of 147 evaluable patients (40.14%) developed hypothyroidism after a median of 12.7 months after radiation (range 2.6 to 44.4 months). Age, gender, stage, tumor site, and surgery did not show statistically significant correlation with the development with hypothyroidism. Mean Thyroid radiation dose correlated with the development of hypothyroidism (<i>P</i> < 0.01) on logistic regression modeling. 47.6 % of patients with mean thyroid dose greater than 40 Gy developed hypothyroidism compared to 18.7% of those receiving less than 40 Gy (<i>P</i> < 0.01, Chi-square test). Administration of chemotherapy was associated with hypothyroidism development after radiation (<i>P</i> < 0.05, Chi-square test). <h3>Conclusion</h3> Our institutional experience demonstrates hypothyroidism remains a frequent late complication with modern IMRT techniques. Mean thyroid dose correlates with the development of hypothyroidism. Intriguingly, administration of chemotherapy also correlates with the development of hypothyroidism. Ongoing aims include further characterizing the interaction of radiation therapy dose with chemotherapy in the development of hypothyroidism.

A Dosimetric Analysis of Reduction Cardiac Dose with Lead Shielding in Breast Cancer Radiotherapy

Adjuvant radiotherapy is an important treatment modality after breast-conserving surgery. Due to its proximity, radiation therapy for the left breast can often lead to an escalated heart dose that can result in heart diseases. The purpose of this study was to evaluate the heart dose reduction by using lead shields surrounding the left breast. The doses of a 3D conformal radiotherapy (3D-CRT) plan, an intensity-modulated radiotherapy (IMRT) plan, and volumetric-modulated arc therapy (VMAT) to the left breast tumor in a CIRS ATOM anthropomorphic female adult phantom were measured by optically stimulated luminescence dosimeters (OSLDs). To protect critical organs, the skin around the target area was covered by lead shields of two different thicknesses (0.125 mm and 0.25 mm). The results showed that compared to IMRT and 3D-CRT, VMAT provided better planning target volume (PTV) coverage, a better conformity index (CI), and homogeneity index (HI). With the use of lead shields, the thyroid dose was reduced by 5.12–27.5% and 20.51–30%, respectively; the heart dose was reduced by 49.41–50.12% and 56.38–57.42%, respectively; and the lung dose was reduced by 1.23–45.22% and 0.98–57.83%, respectively. Although the clinical application of lead shields was rare, this study verified that it could effectively decrease the heart dose from 4.31 ± 0.09 Gy to 1.88–2.18 Gy, thereby potentially reducing the risk of associated heart diseases by 14.8%. Further works to implement this method into clinical practice are needed.

ПРОГНОЗНАЯ ОЦЕНКА ПОСЛЕДСТВИЙ ТЯЖЕЛОЙ АВАРИИ НА БЕЛОРУССКОЙ АЭС ДЛЯ ЗДОРОВЬЯ НАСЕЛЕНИЯ

The article presents the results of assessment of the levels of emergency radionuclide discharge, gamma dose rates, radionuclide fallout, as well as the prognosis of public exposure doses to the population of Belarus as a result of a possible severe nuclear accident at the Belarusian NPP. It was found that, in the case of a severe nuclear accident at the Belarusian NPP with total activity of the accidental release of 4.5∙1015 Bq, the transfer of radioactive contamination to a distance up to 100 km from the site under various meteorological scenarios, will be less than 2 hours. The total contamination density of the territory with 131I and 137Сs isotopes within 100 km radius around the Belarusian NPP will be less than 29 kBq/m2 (0.78 Ci/km2) and less than 5.6 kBq/m2 (0.15 Ci/km2) respectivelly. Maximum value of the thyroid dose will be up to 93.8 mSv, and of the effective dose – 2.86 mSv. Based on the obtained results, the justification for public protective measures was made and recommendations were given for conducting emergency radiation monitoring, taking into account international recommendations and national radiation safety standards of the Republic of Belarus.

Thyroid dose estimates for the genome-wide association study of thyroid cancer in persons exposed in Belarus to 131I after the Chernobyl accident.

The Chernobyl accident on 26 April 1986 led to a sharp increase in thyroid cancer (TC) incidence in the individuals exposed to radiation in childhood. The major risk factor for TC was exposure to Iodine-131 (131I). Here, we estimated the thyroid doses due to 131I intake for 2041 participants of the genome-wide association study of TC in Belarusian people exposed to radioactive fallout from the Chernobyl accident. The following parameter-values specially developed in this study were used to estimate individual thyroid doses: (i) scaling factors for adjustment of the model-based doses, (ii) age and gender diet to characterize 131I intake, and (iii) area-, age- and gender-specific S-values for the thyroid gland per 131I decay in the thyroid. The most reliable doses were calculated for 103 people with measured 131I thyroid activity (the arithmetic mean of 1.2Gy, median 0.52Gy), and 275 individuals with detailed residential history and dietary data (the arithmetic mean of 0.41Gy, median 0.24Gy). The arithmetic mean of thyroid doses among all study participants was 0.23Gy (median 0.082Gy); the highest individual dose was 9.0Gy. Special attention was paid to the reliability and validity of the obtained estimates, in particular for the individuals without 131I thyroid activity measurements and individual data on residential history and diet, by comparing those with the doses from other post-Chernobyl epidemiological studies. Overall, the doses estimated in the current study were in reasonable agreement with previously reported thyroid doses. These doses will be used in the genome-wide association study of TC in people exposed in Belarus to 131I after the Chernobyl accident.

Исследование макро- и микроэлементного статуса у пациентов с аутоиммунным тиреоидитом среди жителей пострадавших после Чернобыльськой аварии районов Киевской области

Актуальность. Аутоиммунный тиреоидит (АИТ) — комплексное полигенное органоспецифическое заболевание. Уровень заболеваемости АИТ имеет тенденцию к росту во всем мире. Наблюдается тенденция к росту заболеваемости в младших возрастных группах. Циркулирующие антитела к тиреоидной пероксидазе (ТПО) находят у 10–15 % практически здоровых лиц, которые находятся в состоянии эутиреоза. Цель: установить макро­ и микроэлементный статус у пациентов с АИТ среди жителей пострадавших после Чернобыльской аварии районов Киевской области. Материалы и методы. Обследован 61 житель пострадавших после Чернобыльской аварии районов Киевской области: из них 45 — без тиреоидной патологии (контрольная группа) и 16 — с АИТ (опытная группа). Все обследованные с дозой облучения щитовидной железы (ЩЖ) &lt; 0,3 Гр — ≥ 1 Гр являются участниками когортных исследований украинско­белорусско­американского проекта. Исследование микро­элементов и макро­элементов проводили методом атомно­эмиссионной спектрометрии с индуктивно­связанной плазмой («Джерело­2003») на приборе Optima 2100 DV фирмы Perkin Elmer (США). Результаты. При исследовании показателей тиреоидного статуса группа пациентов с АИТ отличалась от конт­роля увеличенным тиреоидным объемом, повышенным уровнем антител к ТПО и увеличенным уровнем тиреотропного гормона. Медиана экскреции йода с мочой в исследованных группах достоверно не отличалась, ее показатель в контрольной группе составлял 65,0 мкг/л, в опытной группе — 80,6 мкг/л, что указывало на наличие йодного дефицита слабой степени тяжести. У обследованных пациентов с АИТ установлено более низкое (p &lt; 0,01) содержание магния в сыворотке крови (медианное значение 18,59 мг/л) по сравнению с соответствующим показателем контрольной группы. Проведена оценка шансов связи установленного диагноза АИТ со сниженным менее медианного значения уровнем магния (20,6 мг/л) в общей группе обследованных: отношение шансов (ОШ) составляет 6,63 (95% доверительный интервал (ДИ) [1,73; 24,8]; р &lt; 0,01). Выводы. Имеющейся диагноз АИТ достоверно значимый у пациентов, у которых показатель дозового облучения ЩЖ выше медианного значения (0,12 Гр), в общей группе обследованных в Киевской области: ОШ = 4,1 (95% ДИ [1,2; 13,9]; р &lt; 0,05). Наибольший показатель ОШ был при сочетании сниженного содержания магния и высоких значений дозового облучения ЩЖ: ОШ = 25 (95% ДИ [3,16; 179,0]; р = 0,002).

41Thyroid Cancers in Fukushima: Critical Review and Analysis of the 1st and 2nd Round Examination

Abstract Background After the Fukushima–Daiichi nuclear power plant (NPP) disaster, thyroid ultrasound examination (TUE) has been performed in subjects who were aged ≤18 years. Previous studies reported controversial results. Through critical review, three limitations were identified: arbitrary grouping of 59 municipalities, 2) usage of region as proxy of dose, and 3) separate analyse of the 1st and 2nd round data. Methods To overcome these limitations, this study examined the relationship between radiation dose and the number of participants with thyroid malignancy, using publicly available municipality level data (N = 59). To analyse two wave screening data, multi-level random-effect Poisson regression model was applied. The number of participants with thyroid malignancy was explained by dose estimates. Interaction between dose and screening round dummy (0 for the 1st and 1 for the 2nd) was also introduced to take into account latency. Results Interaction terms between external dose (Akahane et al. 2013) and screening round dummy were positive and significant (β = 0.681, z = 2.05). Similar results were obtained for UNSCEAR estimated thyroid dose (UNSCEAR 2013) (β = 0.128, z = 2.24) and re-estimated thyroid dose (Suzuki et al. 2018) (β = 0.215, z = 2.42). Conclusions These robust results are consistent with the conjecture that the 1st round TUE is the “baseline” that will not correlated with radiation level and the 2nd round TUE detected thyroid cancer caused by radiation from Fukushima NPP that distributed heterogeneously among regions. Key messages This was an ecological study at the municipality level, the results should be examined with individual level data.

Multivariate NTCP Model of Hypothyroidism After Intensity-Modulated Radiotherapy for Nasopharyngeal Carcinoma.

ObjectiveTo evaluate the incidence of hypothyroidism in patients with nasopharyngeal carcinoma after intensity-modulated radiotherapy (IMRT), analyze its correlation with multiple influencing factors such as thyroid exposure dose, thyroid volume, and gender, and construct a multivariate-based normal tissue complication probability (NTCP) model for the occurrence of hypothyroidism after IMRT.Materials and MethodsThe thyroid hormone levels of patients at different points in time before and after radiotherapy were tested, and statistics on the incidence of hypothyroidism after treatment were obtained. The dose-volume data of patients’ thyroids were converted into EQD2 equivalent dose values. The correlation between hypothyroidism after radiotherapy and thyroid exposure dose, thyroid volume, gender, and other factors was analyzed, and an NTCP model was constructed.ResultsA total of 69 patients with nasopharyngeal carcinoma were enrolled in this study. Twelve months after radiotherapy, a total of 24 patients (34.8%) developed hypothyroidism. Univariate analysis and multivariate analysis revealed that the average thyroid dose and thyroid volume are the most important factors affecting hypothyroidism after radiotherapy. The NTCP model constructed based on the average dose and thyroid volume has a good degree of fit.ConclusionThe volume and average dose of the thyroid gland are the key factors affecting the occurrence of hypothyroidism in patients with nasopharyngeal carcinoma after radiotherapy. The NTCP model constructed based on multivariate construction suggests that reducing the average dose of the thyroid to the greatest extent is an effective way to protect thyroid functions.