Thyroid Dose Research Articles

8507 Misdiagnosis of Graves’ and RAI Treatment in Patient with THRB Gene Mutation

Abstract Disclosure: E. McBride: None. R. Kennedy: None. A.N. Davis: None. S.J. Healy: None. Introduction: Resistance to thyroid hormone (RTH) is an inherited condition in which there is decreased tissue responsiveness to thyroid hormone. Occasionally patients with this condition can be misdiagnosed with hyperthyroidism.Clinical case: A 35 yo female was referred to our clinic for evaluation of postablative hypothyroidism. 6 years prior, the patient was evaluated by endocrinology at our city’s army hospital. The patient had abnormal TFTs during HTN workup but was otherwise asymptomatic. Family history included goiter in paternal aunt and grandmother (s/p thyroidectomy). Labs showed TSH 0.370 mIU/L (0.3-3); FT4 2.01, repeat 1.96 ng/dl (0.6-1.6); FT3 6.10 pg/ml (2.3-4.4); T4 16.2 mcg/dl (4.5-12); alpha subunit 0.32ng/ml; TBG 31 mcg/ml (13-39). On exam patient had thyromegaly. Thyroid US showed normal gland with length 5.6 cm. Subsequent labs showed negative thyroglobulin ab, antithyroid microsomal ab, TBII, and TSI. Resistance to thyroid hormone (RTH) was suspected. Pt underwent RTH mutation analysis. Result was heterozygous for c.715T>A (pTrp239Arg) in exon 7 of the THRB gene, described as variant of unknown significance. Treatment was not recommended. Patient desired pregnancy and was evaluated by our hospital’s MFM clinic for preconception counseling. Per notes, patient had another child who tested negative for the gene.Patient then moved out of state, and 1 year later she underwent ablation for presumed diagnosis of Graves’ disease. The records from that hospital are not available. Patient later moved back to our city and was evaluated in clinic. At that visit, weight was 44 kg and patient was on 200 mcg LT4 daily. Pt endorsed cold intolerance, mood swings, brain fog, some hair loss. Recent thyroid US showed diminutive thyroid, and outside labs showed TSH 7.288, TPO ab <4. Our labs showed TSH 8.6 and FT4 2.05. Pt was still interested in becoming pregnant. She did not recall the prior genetic testing or diagnosis of RTH, and believed that she had Graves’. Patient did not return for follow up visit and later moved out of state.Conclusions: Patient’s labs showed elevated T4 and T3 with normal TSH. Genetic testing revealed a mutation in THRB gene. The normal codon is TGG coding for tryptophan and mutation in this patient is AGG coding for arginine. Other mutations in this same codon result in reduced T3 binding affinity.This patient was later was misdiagnosed as having Graves’ at an outside hospital, presumably due to labs and increased thyroid uptake. Patient underwent unnecessary RAI treatment. It is common for these patients to require higher than expected doses of thyroid hormone.This case illustrates the importance of obtaining outside records and correlating thyroid function tests with imaging studies. It is a reminder that not all cases of increased thyroid uptake are due to Graves’. Management of thyroid hormone can be challenging in patients with RTH who have undergone ablation. Presentation: 6/3/2024

Thyroid cancer incidence in cohorts exposed in childhood to 131I released during the Windscale nuclear reactor accident at Sellafield, England, in 1957.

A fire in one of the Windscale nuclear reactors at Sellafield (Cumbria, England) in October 1957 released 1,800 TBq of 131I (half-life, 8 days) to atmosphere. Measurements of 131I activity in thyroids of exposed children showed typical thyroid doses of tens of milligray, but with some exceeding 100 mGy. Radiation exposure in childhood is known to increase the risk of thyroid cancer. Consequently, an investigation was conducted into whether raised numbers of thyroid cancer cases occurred in those exposed to 131I as young children in Cumbria. A database of Cumbrian births from 1950 onwards allowed cohorts of 56,086 births during 1950-1958 and 137,444 births during 1959-1980 to be constructed, periods including children potentially exposed and unexposed, respectively, to 131I. Three areas of Cumbria with different 131I contamination levels were identified from monitoring data, and births assigned to these three areas for the two periods of birth. Members of these six sub-cohorts were linked to incident thyroid cancer cases in Great Britain during 1981-2020 using national cancer registration databases, providing thyroid cancer incidence rates. Incidence rate ratios (IRRs), with the lowest contamination area as a reference, were computed. No IRR differed discernibly from unity. For births during 1950-1958, the IRR for the combined highest and intermediate 131I contamination areas was 0.68 (95% confidence interval: 0.24, 1.56), and no case of thyroid cancer was found in the small cohort born in the highest contamination area. In conclusion, no increased risk of thyroid cancer in those exposed to 131I as young children in Cumbria in 1957 was detected. This study adds to the evidence on the long-term risk of thyroid cancer following childhood exposure to low and moderate levels of 131I, such as occurred following the Fukushima nuclear accident in 2011.

Recent insights into trends of thyroid cancer incidence in Lithuanian population exposed to Chernobyl fallout early in life

In the last three decades, an increase in thyroid cancer incidence has been observed worldwide, as well as in Lithuania. Although the rise was linked to overdiagnosis, the role of lifestyle and environmental factors, including exposure to ionizing radiation, cannot be excluded. In our retrospective study, we aimed to assess the association between the average age-specific thyroid dose due to the radioactive iodine uptake during childhood and adolescence from the Chernobyl fallout in Lithuania, and the trends of incidence of thyroid cancer from 1991 to 2015 in different regions. Averaged age-dependent thyroid doses were estimated for every municipality based on radioiodine activity in milk, reconstructed from available 131I activity measurements in the grass. Thyroid cancer incidence rates were calculated for the entire population and for two age at the time of exposure groups: 0–19 years and 0–9 years. Thyroid cancer relative risk (RR) was estimated for three municipality-specific thyroid dose (for 0-year-old babies) categories: less than 100 mGy (reference group), 100–199 mGy, and ≥200 mGy. Over the study period (1991–2015), a total of 5664 cases of thyroid cancer were registered in the entire Lithuanian population; 817 cases in the age group from 0 to 19 years at the time of the Chernobyl accident, and 266 cases in the age group from 0 to 9 years. Age-standardized thyroid cancer incidence rates have notably increased since 2000, peaked in 2009 (especially in females), and then slightly decreased and stabilized. The estimated average municipality-specific age-dependent thyroid doses ranged from 270 mGy in western Lithuania to 1.5 mGy in central and northern Lithuania. For the age group of 0–19 years at the time of the accident, in the period 1991–1995, the thyroid cancer relative risk was significantly increased (RR 3.91; 95 % CI: 1.27–10.29, p=0.01) in the highest dose category, compared to the lowest (although based on a small number of cases). For the age group 0–9 years at the time of the accident, a tendency of increased RR in the highest dose category appeared in the most recent period, 2011–2015. Our observations need to be confirmed by further following trends of thyroid cancer incidence in the cohort of 0–19-year-old Lithuanians at the time of the Chernobyl accident.

Absorbed dose, effective dose and lifetime attributable risk of breast and thyroid cancers in coronary CT angiography: A comparison between 64 and 128 slice CT scanners

The attentive consideration of absorbed dose impact on the breast, a radiosensitive organ, remains pivotal in coronary computed tomography angiography (CCTA). Additionally, the thyroid is subjected to scatter radiation during this diagnostic procedure. The primary objective of this study was to comprehensively investigate and quantify the absorbed dose, effective dose, and lifetime attributable risks (LARs) associated with breast and thyroid cancers in the context of CCTA. This investigation enrolled a cohort of 180 patients (90 men and 90 women) who underwent CCTA utilizing three distinct CT scanners: the SOMATOM Definition AS 128 slice (Siemens 128), the Lightspeed VCT 64 Slice (GE 64), and the Brilliance 64 Slice (Philips 64). The precise quantification of absorbed doses to the breast and thyroid was achieved through the utilization of a thermoluminescence dosimeter (TLD). LAR for breast and thyroid cancers was evaluated in accordance with the BEIR VII report. Kruskal–Wallis test was employed to compare the means of absorbed doses and LARs. The average absorbed doses to the breast during CCTA with Siemens 128, GE 64, and Philips 64 scanners were 116.32 ± 39.02, 82.88 ± 18.33, and 84.11 ± 15.18 mGy, respectively (P < 0.05). Correspondingly, the average LAR for breast cancer was found to be 84, 68, and 52 cases per 100,000 persons, respectively. Notably, a significant discrepancy in breast cancer LARs was observed among different age groups (P < 0.05). Regarding thyroid doses with Siemens 128, GE 64, and Philips 64 scanners, average values were 11.82 ± 7.51, 12.20 ± 10.87, and 14.49 ± 5.43 mGy, respectively (P > 0.05). Additionally, the average LAR for thyroid cancer was determined as 0.32, 0.56, and 0.22 cases per 100,000 persons, respectively. Across all age groups, the LAR for thyroid cancer exhibited higher values among women compared to men. However, these differences did not achieve statistical significance (P > 0.05), indicating a need for further investigation. The findings prominently indicated high absorbed doses to the breast in CCTA using protocols investigated in this study (with an average of 93.7 ± 30.26 mGy). Particularly, the LAR for breast cancer was higher among younger women, specifically those aged between 20 and 40 years (249 cases per 100,000). These results underscore the necessity for further justification and optimization of CCTA protocols.

Thyroid and contralateral breast surface dose variation in mammography: a phantom study on the role of breast tissue composition

The organs of the thyroid and contralateral breast can be exposed to radiation because of scattered x-rays during mammography. It is important to determine the dose values of these quantities in terms of the risk of triggering a second cancer induction for both organs. In the present study, thyroid and contralateral breast surface doses were investigated with LiF:Mg,Ti (TLD-100) dosimeters for three types of BR-12 phantoms with glandularity/fat tissue ratios (70%/30%, 50%/50% and 30%/70%) over four views as in the real patient situation in Mo/Mo and Mo/Rh anode/filter combinations in each phantom thickness as opposed to a single glandular/fat tissue commonly used in the literature. Both thyroid and contralateral surface doses increased with increasing both phantom thickness and glandularity/fat ratio. The thyroid surface doses changed within 0.06–0.18 mGy and 0.05–0.14 mGy according to phantom thickness of 2 to 6 cm for the glandularity/adipose of 50%/50% in the Mo/Mo and Mo/Rh, respectively. On the other hand, the contralateral breast surface doses were within 0.35–1.39 mGy and 0.40–0.99 mGy for 50%/50% in the Mo/Mo and Mo/Rh, respectively. Based on a 70%/30% breast composition with a phantom thickness of 6 cm, the thyroid and contralateral breast surface doses increased by approximately 40% compared with 50%/50% for both Mo/Mo and Mo/Rh. These results showed that both thyroid and contralateral breast surface doses significantly depend on the glandularity/fat composition of the breast. Therefore, the outputs of this study may contribute to future studies aimed at reducing the doses received by organs during examination.

Concomitant lithium increases radioiodine uptake and absorbed doses per administered activity in graves' disease: comparison of conventional versus lithium-augmented radioiodine therapy.

BackgroundLithium inhibits iodine and thyroid hormone release from thyroid cells, possibly increasing radioiodine retention and anti-hyperthyroid efficacy when given adjunctively to radioiodine therapy (RAI) of Graves’ disease (GD). However, the literature contains limited dosimetric data regarding the influence of concomitant lithium in this setting.MethodsWe retrospectively compared dosimetric variables in patients undergoing RAI with/without adjunctive lithium (n = 52 each). We assessed two low-dose, short-duration oral lithium carbonate regimens, 450 mg/d (n = 22) or 900 mg/d (n = 30), for a mean of 4.7 ± 1.4 d starting upon RAI administration. Patients underwent diagnostic testing to measure thyroidal radioiodine uptake (RAIU) 24 h ± 2 h after ingesting up to 5 MBq radioiodine, receiving individualized RAI activities 24 h later. Using ≥3 RAIU daily measurements starting 24 h post-RAI, researchers were able to determine the effective radioiodine half-life and absorbed dose to the thyroid; we also calculated the absorbed dose per administered activity concentration within that organ. Rates of GD cure, defined as reaching euthyroidism or hypothyroidism post-RAI, were evaluated in patients with ~6 months or longer post-RAI follow-up.ResultsThe lithium dosage subgroups had similar dosimetric values and thus are considered together. Lithium patients and controls had similar average “diagnostic” RAIU (51.1% ± 15.7% vs. 50.6% ± 13.8%, p = 0.820), but the former had significantly higher RAIU post-RAI (56.3% ± 13.5% vs. 49.1% ± 13.5%, p = 0.002), reflecting significantly greater change in the former (+16.2% ± 30.4% vs. -1.8% ± 16.1%, p = 0.001). Radioiodine effective half-life was non-significantly longer in lithium patients (5.43 ± 1.50 d vs. 5.08 ± 1.16 d, p = 0.192). The mean RAI administered activity was 27% less in lithium patients (677 ± 294 MBq vs. 930 ± 433 MBq, p = 0.001), but GD cure rates were similar (83% [39/47] vs. 82% [33/40], p = 0.954), possibly due to the significantly higher thyroid dose in the lithium patients, especially in thyroid gland with a volume ≤ 20 mL (1.04 ± 0.44 Gy/MBq vs. 0.76 ± 0.30 Gy/MBq, p = 0.020). Day 3 serum lithium concentrations were low (450 mg/d: 0.26 ± 0.12 mmol/L, 900 mg/d: 0.50 ± 0.18 mmol/L); no lithium toxicity was noted.ConclusionLithium augmentation may increase the RAIU and thyroid absorbed dose, permitting potentially decreased RAI activities without sacrificing efficacy. Our observations should be confirmed in a prospective, randomized trial.

Thyroid Absorbed Dose from Brain CT Examinations in Different Age Groups of Pediatric Based on Monte Carlo Simulation

Background: This study was designed to assess the thyroid absorbed dose from brain computed tomography (CT) scans across various pediatric age groups, utilizing Monte-Carlo simulation and thermoluminescent dosimeters (TLDs). Methods: We used the Monte Carlo N-particle (MCNP) transport code to model the spiral CT scan of the brain and calculated the average thyroid dose for each pediatric age group. Techniques for variance reduction, such as Time cutoff, Energy cutoff, and Russian roulette, were implemented. Additionally, a cross-sectional study measured the average thyroid absorbed dose in 45 patients under 20 years using TLD dosimetry. The data were analyzed with SPSS software at a 95% confidence interval (CI). Results: The absorbed thyroid dose for an irradiation time of 1 second and 120 mA across the age groups 0 - 5, 6 - 10, 11 - 15, and 16 - 20 years for boys was 4.165 ± 0.028, 3.802 ± 0.036, 3.861 ± 0.031, and 3.021 ± 0.029 mGy, respectively, and for girls, it was 4.185 ± 0.024, 3.852 ± 0.044, 4.052 ± 0.028, and 4.072 ± 0.047 mGy, respectively. For a dose of 110 mAs, the results for boys were 3.711 ± 0.037, 3.660 ± 0.026, 3.251 ± 0.019, and 3.204 ± 0.031 mGy, respectively, and for girls were 3.882 ± 0.040, 3.842 ± 0.032, 3.412 ± 0.026, and 3.619 ± 0.029 mGy, respectively (P &lt; 0.001). Conclusions: Comparing these results with experimental studies indicates the feasibility of using less computationally intensive methods. The thyroid dose received by girls was higher than that for boys, aligning with findings from experimental studies and other research.

An approach of radiological impact analysis due to a simulated accident of the TRIGA research reactor of Bangladesh

The present study focused on the radiological impact analysis by assessing radiological doses due to a postulated TRIGA Mark-II research reactor accident at AERE, Savar, Dhaka, Bangladesh. Core inventory and source term of radionuclides from different groups such as noble gas, halogen, tellurium, alkali metal, lanthanide, alkaline earth metal, cerium and transition metal were analyzed for 365 days of operation at full power (3 MWth) due to a postulated nuclear accident. The HotSpot code was used for the dose calculation, and the dose values of TED, and Thyroid were calculated for a 40 km radius from the reactor site. Local meteorological data from Bangladesh Meteorological Department were used for the dose assessment and doses were calculated in the three dominant directions such as South, Southeast, and West. The TED and Thyroid dose values are assessed and compared to the PAZs dose criteria of the U.S. Environmental Protection Agency. It is found that doses are higher in stability class F, and evacuation, sheltering, and iodine prophylaxis are needed at longer distances. Since outside of the AERE campus is densely populated, these calculated data may help to ensure radiological safety by taking required protective actions like evacuation, sheltering, and iodine tablet consumption for the same type of accidental situation.

Comparison of Thyroid Toxicity Profiles in Head and Neck Cancer Patients Irradiated by 3D-Conformal Radiation Therapy and Intensity-Modulated Radiation Therapy

ABSTRACT Background: In spite of recent technical advances in the radiation field, exposure to non-target organs such as the thyroid gland remains unavoidable in locally advanced head and neck cancer (LAHNC) planning, which is associated with late toxicities, and this may affect the lifestyle of cancer survivors. Aim: The purpose of this study was to estimate the incidence of thyroid toxicity in LAHNC patients treated with three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT). To establish its correlation, we have analyzed thyroid profile levels, DVH, and the doses of radiation received by the thyroid volume in both radiotherapy planning methods. Material and Method: Sixty patients with LAHNC enrolled and were divided into two groups treated with 3D-CRT (group A) and IMRT (group B). The patient’s thyroid function test, which consisted of serumT3, T4, and TSH, was done before starting radiotherapy and at 6 months and 12 months follow-up. Absolute thyroid volume, maximum dose, minimum dose, mean dose to the thyroid gland, and percentage of thyroid volume receiving as V10, V20, V30, V40, and V50 were studied. Results: After 6-month post-RT, 6.7% of patients in group A showed biochemical hypothyroidism, whereas biochemical hypothyroidism, sub-clinical hypothyroidism, and hyperthyroidism were observed in 10%, 3.3%, and 10% patients of group B, respectively. After 12 months post-RT, 23.3% of patients in group A showed hypothyroidism. In the 3DCRT group, mean T3 was significantly higher for patients with no hypothyroidism (P &lt; 0.05). Mean T4 was observed to be significantly lower in both the groups in hypothyroid patients (P &lt; 0.05). Mean TSH was significantly higher for hypothyroid patients in the IMRT group (P &gt; 0.01). The difference in thyroid volume and thyroid dose was observed to be statistically significant (P &lt; 0.05). Conclusion: The incidence of thyroid toxicity may be decreased by sparing the volume of the thyroid gland and the thyroid dose kept to a minimum. As per dosimetric parameters, &gt;V40 may predict the risk of developing hypothyroidism after irradiation in LAHNC patients. We recommend regular thyroid function tests on follow-up visits of irradiated patients of LAHNC.

Dental Cone-Beam Computed Tomography: Are the Eye Lens and Thyroid at Risk?

Background: The purpose of this study was to assess radiation dose to the eye lens (EL) and thyroid gland (TG) from 22 protocols used in maxillofacial imaging with cone-beam computed tomography (CBCT).Methods and Results: NanoDot optically stimulated luminescence dosimeters were used to assess scattered radiation to the EL and TG using a phantom. The dosimeters were secured at four sites around areas of interest. Mean eye radiation dose was significantly associated with field of view (FOV) size (r=0.830, P&lt;0.001). Meanwhile, the mean thyroid radiation dose was found to be significantly associated only with exposure time (r=0.464, P=0.030). Mandible centralization was observed to be the most significant predictor for a greater effective thyroid dose; mandible FOV centralization had 0.236 odds of a higher thyroid dose than maxilla FOV centralization.Conclusion: FOV size significantly impacted EL dose. Thyroid exposure was affected by FOV centralization and exposure time. Centering the FOV on the mandible resulted in a greater effective dose due to the proximity of the TG to the primary beam.

Radioiodine internal dose coefficients specific for Koreans

This study developed internal dose coefficients for radioiodine, tailored to the Korean population, by incorporating the Korean biokinetic model along with the Korean S values. The observed differences in dose coefficients for Koreans compared to the International Commission on Radiological Protection (ICRP) reference values noticeably varied depending on physical half-lives of iodine isotopes. For longer-lived isotopes such as I-125 and I-129, significant differences in thyroid dose coefficients were observed, with ratios (Korean/ICRP) from 0.30 to 0.55, indicating that actual doses for Koreans can be considerably lower than those evaluated based on the ICRP data. However, for short-lived iodine isotopes, such as I-131, the thyroid dose coefficients were comparable to the ICRP reference values (ratio = 0.95–0.98). These comparable dose coefficients resulted from the lower thyroidal iodine uptake in the Korean model being almost entirely offset by the higher thyroid self-absorption S values in the Korean phantoms. Additionally, this study delves into the substantial differences in absorbed dose coefficients for non-thyroidal regions and effective dose coefficients, which arose not only from physiological/anatomical variability but also technical differences in phantom design. The use of Korean-specific dose coefficients is advisable particularly in scenarios predicting elevated doses, yielding a more precise and clinically relevant dose assessment.

Enhancing Resilience through Nuclear Emergency Preparedness at El Dabaa Site

The research utilized advanced PCTRAN and RASCAL software to evaluate the potential radiological impacts of hypothetical accidents, specifically loss-of-coolant accident (LOCA) and long-term station blackout (LTSBO), at the El Dabaa Nuclear Power Plant. Over a span of ten years, comprehensive meteorological data were meticulously analyzed to assess the dispersion of radioactive substances within a 40-kilometer radius across all four seasons. The outcomes revealed that only in the case of LTSBO did the radiological levels surpass the limits set by the Environmental Protection Agency (EPA). Notably, during spring, LTSBO exhibited a maximum total effective dose equivalent (TEDE) value of 13 millisieverts (mSv) at a distance of 3.2 kilometers, and the highest thyroid dose (TD) recorded was 63 mSv at 8 kilometers. These significant findings play a crucial role in shaping strategies related to the distribution of potassium iodide (KI) and further enhance the overall preparedness and evacuation planning protocols.

The RADTRAD analysis methodology for the Fuel Handling Accident during the long-term shutdown period of Chinshan Nuclear Power Plant

Abstract This study presents a methodology for the Fuel Handling Accident (FHA) analysis during the long-term shutdown period with the fuels still residing in the reactor core for the Chinshan BWR/4 Nuclear Power Plant. This methodology can be used to calculate the radiation dose received by the control room personnel, assuming failure in safety systems, facilities or structures. The computer code RADTRAD is employed to perform the transport and release of radioactive inventories first, and then calculate the control room dose based on appropriate dose conversion factor for the FHA. The results show that even failure in safety systems, facilities or structures, the whole body dose, thyroid dose and beta-skin dose are well below the acceptance limits specified in the Standard Review Plan.

Radiological consequence assessment from long term station blackout nuclear accident on Buyende nuclear power plant of Uganda

Uganda’s energy policy of 2023 and Vision 2040 plans to address the country’s electricity shortage by introducing nuclear power of 24,000 MW capacity by 2040. The pioneer nuclear power plants with a generation capacity of 8,400 MW will be built in Buyende District. This study focused on assessing the radiological consequences of potential nuclear accident on any of the four technologies of APR1400, VVER1200, HPR1000, and APR1000. Evaluation of acute and chronic radiation effects from a long-term station blackout accident using RASCAL and GENII codes identified the order of minimum health risks to the public as APR100, HPR1000, VVER1200, and APR1400 if single units are constructed. The total effective dose equivalents and thyroid doses at the exclusion area boundary and emergency protection zone were within the regulatory limits of 250 mSv and 3,000 mSv, respectively for all the reactor technologies.

Radiation Dose Does Not Affect the Predictive Value of Thyroid Biopsy for Diagnosing Papillary Thyroid Cancer in a Belarusian Cohort Exposed to Chernobyl Fallout

Introduction: The Chernobyl nuclear accident exposed residents of contaminated territories to substantial quantities of radioiodines and was followed by an increase in thyroid cancer, primarily papillary thyroid cancer (PTC), among exposed children and adolescents. Although thyroid biopsy is an essential component of screening programs following accidental exposure to radioiodines, it is unknown whether the predictive value of biopsy is affected by different levels of environmental exposure. Methods: A cohort of 11,732 Belarusians aged ≤18 years at the time of the Chernobyl accident with individual thyroid radiation dose estimates was screened at least once 11–22 years later. Paired cytologic conclusions and histopathologic diagnoses were possible for 258 thyroid nodules from 238 cohort members. Cytologic conclusions were divided into five reporting categories, with all follicular lesion aspirates combined into a single indeterminate category. Standard performance indicators, risk of malignancy (ROM), and odds ratios for a correct cytologic conclusion were calculated, both overall and according to quintile of thyroid radiation dose. Results: The arithmetic mean thyroid dose estimate for the study group was 1.73 Gy (range: 0.00–23.64 Gy). The final histopathologic diagnosis was cancer for 136 of 258 biopsies (52.7%; 135 papillary and 1 follicular). The overall ROM was 96.7% for cytologies definite for PTC, 83.7% for suspicious for PTC, 33.0% for indeterminate, 8.1% for benign, and 31.0% for non-diagnostic. The ROM showed little change according to level of radiation exposure. Overall, there was no association between thyroid radiation dose and the odds ratio for a correct cytologic conclusion (p = 0.24). When analyzed according to dose quintile, the odds ratio for a correct conclusion increased two-fold at 0.10–0.29 Gy compared to a dose of 0.00–0.09 Gy and decreased at doses of 0.3–24 Gy (p value for linear trend = 0.99). Conclusions: At radiation doses received by a cohort of young Belarusians exposed to radioiodines by the Chernobyl accident, the predictive value of thyroid biopsy for diagnosing PTC was not significantly affected by level of radiation exposure.

Estimation and comparison of the effective dose and lifetime attributable risk of thyroid cancer between males and females in routine head computed tomography scans: a multicentre study.

A significant number of head computed tomography (CT) scans are performed annually. However, due to the close proximity of the thyroid gland to the radiation field, this procedure can expose the gland to ionising radiation. Consequently, this study aimed to estimate organ dose, effective dose (ED) and lifetime attributable risk (LAR) of thyroid cancer from head CT scans in adults. Head CT scans of 74 patients (38 males and 36 females) were collected using three different CT scanners. Age, sex, and scanning parameters, including scan length, tube current-time product (mAs), pitch, CT dose index, and dose-length product (DLP) were collected. CT-Expo software was used to calculate thyroid dose and ED for each patient based on scan parameters. LARs were subsequently computed using the methodology presented in the Biologic Effects of Ionizing Radiation (BEIR) Phase VII report. Although the mean thyroid organ dose (2.66 ± 1.03 mGy) and ED (1.6 ± 0.4 mSv) were slightly higher in females, these differences were not statistically significant compared to males (mean thyroid dose, 2.52 ± 1.31 mGy; mean ED, 1.5 ± 0.4 mSv). Conversely, there was a significant difference between the mean thyroid LAR of females (0.91 ± 1.35) and males (0.20136 ± 0.29) (P = 0.001). However, the influencing parameters were virtually identical for both groups. The study's results indicate that females have a higher LAR than males, which can be attributed to higher radiation sensitivity of the thyroid in females. Thus, additional care in the choice of scan parameters and irradiated scan field for female patients is recommended.

Estimation of Entrance Surface Radiation Dose to Thyroid and Gonads during Computed Tomography Thorax Examination

ABSTRACT Introduction: The organ’s sensitivity to radiation exposure varies depending on the cells in that organ. The thyroid and gonads have an increased radiation risk since the cells in those organs divide faster. This study aimed to estimate the radiation dose and to compare gender-related variations in entrance dose to the thyroid and gonads during computed tomography (CT) thorax examination. Materials and Methods: We used data from 43 patients prescribed thorax CT examinations. Thermoluminescent dosimeter (TLD) discs detect the scattered radiation dose to the thyroid and gonads. Four discs were used for each patient, two at the thyroid level and two at the gonad region. The exposed and a control TLD disc with the appropriate identifications are sent to Avanttec Laboratories, India, for readings. Results: The median thyroid dose for males and females was 7.55 mSv and 9.42 mSv, respectively. The median gonad dose was 0.11 mSv and 0.25 mSv for males and females, respectively. Gonad dose has a statistically significant difference between males and females (P &lt; 0.001). Karl Pearson’s correlation coefficient was used to check the relationship between body mass index (BMI) and dose length product (DLP), and it showed a correlation coefficient value of 0.611 in males and 0.715 in females, a strong positive correlation between BMI and DLP, irrespective of gender. Conclusion: The scattered entrance radiation dose to the thyroids and gonads was minimal during CT thorax when compared with the literature. However, we recommend providing better care using an optimized protocol with only the required area coverage to protect the thyroid and gonad.

Influence of short-lived radioiodines other than 131I on screening direct thyroid measurements with TCS-172 NAI(TL) survey meters.

In a nuclear emergency, one of the actions taken for the sake of public is to monitor thyroid exposure to radioiodines. Japan's Nuclear Regulation Authority recently published a report on such monitoring and proposed direct thyroid measurements with conventional NaI(Tl) survey meters (e.g. Hitachi model TCS-172) as a primary screening method. A previous study proposed screening levels (SLs) used in these simplified measurements as the net reading values of the TCS-172 device. Age-specific SLs were derived from a thyroid equivalent dose of 100mSv due to the inhalation intake of 131I. This study addressed the possible influence of short-lived iodine isotopes other than 131I on the simplified measurements. In preparation for such measurements, the responses of the device for 132I as an ingrowth component from 132Te, 133I, 134I and 135I in the thyroid were evaluated by numerical simulations using age-specific stylized phantoms in addition to those obtained for 131I in the previous study. The radioactivity ratios of the relevant isotopes were taken from the inventory data of the Fukushima Daiichi Nuclear Power Plant. The results were used to predict the net readings of the device when 132Te-132I and 133I as well as 131I were inhaled at 24 or 72h after the shutdown of a nuclear power plant. In these cases, the signals from 132Te-132I and 133I become undetectable a couple of days after intake, which could lead to underestimations of the thyroid dose. To estimate the thyroid dose accurately from the simplified measurements, it is necessary to identify the exact time of intake after the shutdown and the actual physiochemical property of 132Te that affects the thyroid uptake of 132I.

Assessment of organ doses, peak skin doses and effective doses in patients undergoing anterior cervical discectomy and fusion utilising VirtualDose-IR software.

In this study, the effect of patient- and procedure-related parameters on organ doses (ODs), peak skin dose (PSD) and effective dose (E) during anterior cervical discectomy and fusion (ACDF) was evaluated. Patient- and procedure-related parameters, as well as fluoroscopy time, kerma-area product (KAP), cumulative air-kerma (Kair) and incident Kair, were analysed for 50 ACDF procedures performed with a mobile C-arm. These parameters were inserted in VirtualDose-IR software implementing sex-specific and body mass index (BMI)-adjustable anthropomorphic phantoms to calculate OD, PSD and E. The BMI, gender and type of implants did not significantly affect KAP, incident Kair, PSD and E. However, the type of fusion significantly affected the E. The single fusions in C5/C6 resulted in significantly higher KAP, incident Kair and E than C4/C5 levels, while those performed in C6/C7 resulted in significantly higher E and PSD than C4/C5 levels. The thyroid, oesophagus and salivary glands received the largest doses in all groups studied. The BMI did not significantly affect ODs. The salivary glands absorbed significantly higher doses in males than females, while the extrathoracic region's dose significantly increased for multi- than single-level fusions. The fusions in C6/C7 resulted in significantly higher oesophagus and thyroid doses than C3/C4 and C4/C5 levels, as well as fusions performed in C5/C6 compared with C4/C5 levels. The data presented here could be used by the neurosurgeons as a comparator for future studies in optimising radiation protection during ACDF procedures in the operating theatre by keeping the ODs, PSD and E as low as reasonably practicable.

An Analytical Study to Determine Dose-Volume Threshold for Radiation Induced Hypothyroidism.

Objective: To determine radiation dose volume threshold in predicting the development of hypothyroidism in cancer patients following neck irradiation. Methods: This is a cross sectional follow up study for patients who had been previously irradiated, prior to enrolment in the study. We have done thyroid dose-volumetric analysis on 120 histologically proven cancer patients in the age group of 18-75 years who received neck irradiation as a part of their definitive or adjuvant radiotherapy with three-dimensional conformal or intensity-modulated radiotherapy technique (3D -CRT or IMRT) and completed at least six months post-radiotherapy. Primary tumor sites included carcinoma or lymphoma of the head and neck, breast, cervical, and upper thoracic esophagus, requiring neck irradiation. Results: The proportion of patients who tested positive for Radiation induced hypothyroidism (RIHT) was found to be 40%, with clinical hypothyroidism and subclinical hypothyroidism being 25.8% and 14.2%, respectively. Time to develop hypothyroidism peaks around two years. Mean thyroid gland dose (Dmean) >28 Gy, thyroid gland volume receiving 40 Gy dose (i.e. V40) >49% and age <50 years were found to be significant risk factors for the development of RIHT on binary logistic regression. RT dose >50 Gy and thyroid gland volume spared from 40 Gy (i.e. VS40) < 2.12cm3 were statistically significant predictors for RIHT on chi-square and (Receiver operating characteristic) ROC curve analysis respectively but not on regression analysis. Conclusion: Dose-volume threshold for the thyroid gland as Dmean <28 Gy and V40 <49% may prevent the development of RIHT.