Radiogenic Risk Research Articles

Incidence risk of hepatobiliary malignant neoplasms in the cohort of workers chronically exposed to ionizing radiation

The increased risk of liver malignancies was found in workers of the first Russian nuclear production facility, Mayak Production Association, who had been chronically exposed to gamma rays externally and to alpha particles internally due to plutonium inhalation. In the present study, we updated the radiogenic risk estimates of the hepatobiliary malignancies using the extended follow-up period (1948–2018) of the Mayak worker cohort and the improved «Mayak worker dosimetry system–2013». The cohort comprised 22,377 workers hired at the Mayak PA between 1948 and 1982. The analysis considered 62 liver malignancies (32 hepatocellular carcinomas, 13 intrahepatic cholangiocarcinomas, 16 angiosarcomas, and 1 anaplastic cancer) and 33 gallbladder adenocarcinomas. The analysis proved the positive significant association of the liver malignancy risk (the total of histological types, hepatocellular carcinoma) with the liver absorbed alpha dose from internal exposure. The excess relative risk per Gy (95% confidence interval) of alpha dose (the linear model) was 7.56 (3.44; 17.63) for the total of histological types and 3.85 (0.95; 13.30) for hepatocellular carcinoma. Indications of non-linearity were observed in the dose–response for internal exposure to alpha radiation. No impact of external gamma-ray exposure on the liver malignancy incidence was found. In the study cohort, the number of angiosarcomas among various types of liver malignancies was very high (25.8%), and most of these tumors (73.3%) were registered in individuals internally exposed to alpha radiation at doses ranging between 6.0 and 21.0 Gy. No association with chronic occupational radiation exposure was observed for the incidence of gallbladder malignancies.

Radiogenic cancer risk from contrast enhanced computed tomography during pediatric abdomen and pelvis examinations in Saudi Arabia

The sensitivity to ionizing radiation is increasing by age of development for some malignant tumors. Therefore, children have higher risk to radiation induced tumors due the high cellular rate of proliferation and long lifespan probability. The risk is also increase with increase the effective and organ doses. Computed tomography (CT) exposed pediatric patients to higher radiation dose during multiphase image acquisition, repeated exams, for follow-up procedures. This research intended to estimate the radiogenic risks and effective radiation doses resulted from CT enhanced contrast for abdomen and pelvis. 126 (66 (62.3%) males, 60 (47.7%) females) pediatric patients underwent CT enhanced abdominal examination at Medical Imaging Department at King Khalid Hospital and Prince Sultan Center for Health Services, Alkharj, Saudi Arabia. The average and range of pediatric age (years) is 11.6 ± 5.0 (0.1–17). The mean, standard deviation, and range of the volume CT air kerma index (CVOL (mGy) and the air kerma length product (PKL, mGy.cm) were 9.8 ± 9.4 (2.1–45.8) and 1795 (221–3150) per abdominopelvic procedure, respectively. The mean and range of the effective dose (mSv) per procedure are 26.9 (2.4–59.1). The effective dose is higher compared to the most previously published studies. The effective dose per pediatric abdomen and pelvis with contrast procedure suggest that the patient dose is not optimized yet. Because the chest and pelvis region contain sensitive organs that are irradiated repeatedly, dose optimization is crucial.

Patient organ dose during multicycle radiation dosimetry in Lutetium −177 radionuclide therapy

Precise patient radiation dosimetry during theranostic procedures allows clinicians to tailor therapeutic procedures to each patient. Organ dose measurement aids in adjustment of the administered activity or number of treatment cycles to maximize tumor cell destruction while minimizing damage to healthy tissues. This study was aimed at quantifying patient organ doses during Lu-177 DOTATATE and Lu-177 PSMA theranostic procedures. Nine patients underwent Lu-177 radionuclide therapy, usually four cycles with 6–8 GBq administered activity per cycle. The typical dose is 7.5 GBq as a fixed activity. Using quantitative dosimetry, physicians can estimate the next dose cycle according to patient condition. The average dose per activity for critical organs were low, at 1.76, 1.96, 0.25, 0.5, and 2.43 mSv/MBq for the right kidney, left kidney, liver bladder, and spleen, respectively. The doses for the left and right kidneys, liver, urinary bladder, and spleen were lower than those in previously published studies. Wide variations were observed in patient organ doses for Lu-177 DOTATATE and Lu-177 PSMA procedures. Further studies are recommended to ensure organ safety during theransotic procedures, to minimize the radiogenic risks to healthy organs.

ЗАБОЛЕВАЕМОСТЬ САХАРНЫМ ДИАБЕТОМ 2 ТИПА И РИСК ЕГО ВОЗНИКНОВЕНИЯ У ЛИКВИДАТОРОВ ПОСЛЕДСТВИЙ АВАРИИ НА ЧАЭС, В ТОМ ЧИСЛЕ РАБОТНИКОВ ПРЕДПРИЯТИЙ АТОМНОЙ ПРОМЫШЛЕННОСТИ

Summary: Investigation purposes Diabetes mellitus (DM) occupies the largest share in the structure of endocrine system diseases, nutritional disorders and metabolic disorders, which is currently one of the important priorities of national health systems. Research on certain groups of the population with their own harmful occupational risk factors is relevant. Analysis of the incidence of diabetes mellitus of the second type - T2DM (ICD 10: E11-E11.9) of liquidators of the consequences of the Chernobyl accident ‒ workers of nuclear industry enterprises for 30 years of observation and assessment of the radiation risk of its occurrence. Material and methods: The study includes data from the Industry register of persons exposed to radiation as a result of the Chernobyl accident over a thirty-year period, having a verified dose of external radiation received during work in the 30 km zone of the Chernobyl nuclear power plant, men – 12663 people, 1327, of whom have data on the dose of occupational irradiation. The Poisson process with an intensity parameter was chosen as a statistical model of morbidity. Results: The incidence of T2DM in liquidators of the consequences of the Chernobyl accident was estimated by age and sex groups. On the basis of the obtained file of individual unstratified data, an analytical likelihood function for the Poisson process was constructed and the value of the excess relative risk (ERR) of T2DM incidence was calculated and the nature of the dose dependence of RR was investigated. A cohort epidemiological study of a group of liquidators in 1986–1990 was carried out. over a thirty-year period, depending on the dose, both received during the liquidation of the consequences of the Chernobyl accident, and during professional work with radioactive substances (RS) and sources of ionizing radiation (IRS). Direct estimates of the radiogenic risk of diabetes mellitus are given. Different values ​​of risk were noted when using doses from different types of radiation. There was no significant increase in the risk of disease per dose unit (ERR / Sv). Conclusion: With the aging of the cohort of liquidators, an increase in the incidence of T2DM was noted in both men and women. The results obtained on the assessment of the radiation risk of T2DM at this stage are taken as preliminary, since the use of radiation risk in the development of radiation safety regulations requires a total dose from all types of exposure (professional, emergency, medical, natural).

Оценка заболеваемости глазной поверхности у персонала объекта использования атомной энергии

Relevance. One of the main areas of scientific support for work in the field of ensuring radiation safety during the liquidation of nuclear legacy is the assessment of radiation effects among personnel of nuclear industry enterprises and the most significant radiogenic risks among workers of these enterprises. Objective. To conduct a retrospective analysis of ocular surface morbidity among personnel of a nuclear energy facility under long-term man-made external irradiation. Materials and methods. A retrospective analysis of ocular surface morbidity among personnel of a nuclear energy facility (NUF) under long-term man-made external irradiation was carried out, taking into account the absorbed dose equivalent. The medical records of 3,795 employees were analyzed, divided into 2 groups: main - medical records of 2,546 employees of the main production; comparison - medical records of 1249 employees of auxiliary production. Results. According to the results of a retrospective analysis, blepharoconjunctivitis, inflammation of the lacrimal drainage apparatus, and inflammatory lesions of the cornea are the most common among OAE personnel. At the same time, there is a statistically significant increase in the pathology of the ocular surface as the dose load increases among personnel of both the main and auxiliary production facilities of nuclear power plants. Conclusion. Among nuclear facility personnel exposed to long-term technogenic exposure to ionizing radiation, there is a statistically significant increase in the number of cases of ocular surface diseases as the dose load of soft tissues increases. Keywords: ionizing radiation, long-term technogenic external exposure, ocular surface, morbidity

Patients’ radiation dose evaluation during contrast enhanced computed tomography urography procedure

Renal diseases and urinary tract disorders are causing a global burden, with an estimated prevalence of around 13%. Contrast-enhanced computed tomography urography (CE-CTU) is a well-known diagnostic technique for urinary system diseases for initial diagnosis and, very often, for follow-up. CE-CTU procedure exposes patients to high doses of ionizing radiation; hence, justification and optimization of doses are necessary to maximize the benefits and minimize the patients' risks. This study aims to evaluate radiation doses to patients during CE-CTU procedures and estimate the subsequent radiogenic risk. The study included twenty-seven patients who underwent CE-CTU examination in two different hospitals (National Ribat Hospital (NRH) and National Security Fource Hospital (NSFH)), where 16-slice CT machines from different vendors are used. The variables and significance were analyzed using SPSS and Scheffe's statistical tool. Data collected included the age of patients (19–70 years), the radiation dose received by patients: dose length product (DLP, mGy.cm) and volume CT dose index (CTDIvol (mGy)), and tube current-time product (mAs). Patients' dose measurements per CE-CTU procedure given as (mean and range) was: DLP 3098 (647–5301) (mGy.cm) and CTDIvol 44.11 (15–136) (mGy). The results revealed statistically significant differences in DLP (mGy.cm), CTDIvol (mGy), and mAs, and this could be attributed to discrepancies in protocols, machines, and operators among the hospitals and within each hospital. Considering gender, the variables (age, tube current-time product (mAs), and CTDIvol) showed no statistically significant differences. The radiogenic risks from the CE-CTU procedure were ≈1 per 400. Comparison between the two hospitals showed that the variables varied significantly between the hospitals studied, but no significant differences were found based on gender. CE-CTU with contrast medium exposes patients to high doses. Therefore, proper dose optimization is crucial.

Риск заболеваний щитовидной железы, связанных с йодной недостаточностью, ликвидаторов последствий аварии на Чернобыльской АЭС ‒ работников предприятий атомной промышленности

Purpose: Assessment of thyroid disease risk associated with iodine deficiency, liquidators of the Chernobyl accident consequences, employees of nuclear industry enterprises depending on the doses of different types of exposure. Material and methods: The dose-risk assessment study included 12663 men, 1327 of whom had occupational exposure data. A Poisson’s process with intensity parameter was chosen as a statistical model of morbidity risk. The statistical package of epidemiological data analysis EPICURE was used for the estimation of excess relative risk (ERR) of thyroid diseases related to iodine deficiency. There was conducted a cohort epidemiological study of a group of liquidators who worked in the 30-km zone in 1986‒1990 over a period of more than thirty years depending on the dose received both during liquidation of the Chernobyl accident consequences and during professional work with radioactive substances (RS) and ionizing radiation sources (IRS). Results: As a result of the study direct estimates of radiogenic risk of thyroid diseases associated with iodine deficiency in the liquidators of the Chernobyl accident consequences were obtained for the first time using the data on doses of Chernobyl and the sum of these doses with the doses of occupational exposure. It is shown that the risk of disease per unit dose (ERR/Zv) for dose loads received both at liquidation of Chernobyl accident consequences and for total doses give different results. Conclusion: Assessment of the risk of thyroid diseases associated with iodine deficiency, liquidators of the Chernobyl NPP accident consequences and workers of nuclear industry enterprises, serviced by FMBA health care institutions of Russia using the doses of different types of exposure gives different results. Correct results of assessing the risk of radiation-related diseases can only be given by the register using the total radiation dose (occupational, accidental, medical, natural), as required by the directive documents.

Ionizing radiation and solid cancer mortality among US nuclear facility workers.

The risk of solid cancers from low-level protracted ionizing radiation is not well characterized. Nuclear workers provide valuable information on the effects of ionizing radiation in contemporary exposure scenarios relevant to workers and the public. We evaluated the association between penetrating ionizing radiation exposure and solid cancer mortality among a pooled cohort of nuclear workers in the USA, with extended follow-up to examine cancers with long latencies. This analysis includes 101 363 workers from five nuclear facilities, with 12 069 solid cancer deaths between 1944 and 2016. The association between cumulative equivalent dose measured in sieverts (Sv) and solid cancer subtypes were modelled as the excess relative rate per Sv (ERR Sv-1) using Cox regression. For the association between ionizing radiation exposure and all solid cancer mortality we observed an elevated rate (ERR Sv-1=0.19; 95% CI: -0.10, 0.52), which was higher among a contemporary sub-cohort of workers first hired in 1960 or later (ERR Sv-1= 2.23; 95% CI: 1.13, 3.49). Similarly, we observed an elevated rate for lung cancer mortality (ERR Sv-1= 0.65; 95% CI: 0.09, 1.30) that was higher among contemporary hires (ERR Sv-1= 2.90; 95% CI: 1.00, 5.26). Although concerns remain about confounding, measurement error and precision, this analysis strengthens the evidence base indicating there are radiogenic risks for several solid cancer types.

Dose rate effect on mortality from ischemic heart disease in the cohort of Russian Mayak Production Association workers

For improvement of the radiation protection system it is crucial to know the factors that modify the radiation dose–response relationship. One of such key factors is the ionizing radiation dose rate. There are, however, very few studies that examine the impact of the dose rate on radiogenic risks observed in human cohorts exposed to radiation at various dose rates. Here we investigated the impact of the dose rate (in terms of the recorded annual dose) on ischemic heart disease (IHD) mortality among Russian nuclear workers chronically exposed to radiation. We observed significantly increased excess relative risks (ERR) of IHD mortality per unit of external gamma-ray absorbed dose accumulated at higher dose rates (0.005–0.050 Gy/year). The present findings provide evidence for the association between radiation dose rate and ERRs of IHD mortality in occupationally chronically exposed workers per unit total dose. IHD mortality risk estimates considerably increased with increasing duration of uninterrupted radiation exposure at high rates. The present findings are consistent with other studies and can contribute to the scientific basis for recommendations on the radiation protection system.

Assessment of male patients’ average glandular dose during mammography procedure

Breast cancer is a common malignancy for females (25% of female cancers) and also has low incidence in males. It was estimated that 1% of all breast malignancies occur in males with mortality rate about 20%, with annual increase in incidence. Risk factors include age, family history, exposure to ionizing radiation and high estrogen and low of androgens hormones level. Diagnosis and screening are challenging due to limiting effectiveness of breast cancer screening. Therefore, patients may expose to ionizing radiation that may contribute in breast cancer incidence in males. In literature, limited studies were published regarding radiation exposure for males during mammography. The objective of this research is to quantify patient doses during male mammogram and to estimate the projected radiogenic risk during the procedure. In total, 42 male patients were undergone mammogram for breast cancer diagnosis during two consecutive years. The mean and range of patient age (years) is 45 (23–80). The mean and standard deviation (SD) of the peak tube potential and tube current time product are 28.64 ± 2. and 149 ± 35.1, respectively. The mean, and range of patients' entrance surface air kerma (ESAK, mGy) per single breast procedure was 5.3 (0.47–27.5). Male patient's received comparable radiation dose per mammogram compared to female procedures. With increasing incidence of male breast cancer, proper guidelines are necessary for the mammographic procedure are necessary to reduce unnecessary radiation doses and radiogenic risk.

Paediatric effective radiation doses during brain computed tomography angiography procedure

In comparison to adults and paediatric are more sensitive to ionizing radiation exposure. Computed tomography (CT) is now the dominant source of medical radiologic tests for patients, accounting for more than 70% of total doses to the general public. Paediatric CT brain scans (with and without contrast) are routinely performed for a variety of clinical reasons. As a result, this parameter must be calculated in order to determine relative radiation risk. The goal of this study is to assess the radiation risk to children during CT brain diagnostic procedures. Three hundred fifty three child patients' radiation risk doses were assessed over the course of a year. The mean and ranged of the children's radiation doses were 40.6 ± 8.8 (27.8–45.8) CTDIvol (mGy) and 850 ± 230 (568.1–1126.4) DLP (mGy.cm) for the brain with contrast medium. For CT brain without contrast, the patients' doses were 40.9 ± 9.4 (14.27–64.07) CTDIvol (mGy), and 866.1 ± 289.3 (203.6–2484.9) DLP (mGy.cm). The characteristics related to the radiation dose were retrieved from the scan protocol generated by the CT system by the participating physicians after each procedure. Furthermore, optimizing the CT acquisition parameter is critical for increasing the benefit while lowering the procedure's radiogenic risk. The patients' radiation dose is comparable with the most previously published studies and international diagnostic reference levels (DRLs). Radiation dose optimization is recommended due to high sensitivity of the paediatric patients to ionizing radiation.

3D-CRT, IMRT and VMAT for flank irradiation due to pediatric Wilms tumor: A comparative planning study with XCAT phantoms

PurposeTo compare the dosimetric parameters and radiogenic risks from 3D-CRT, IMRT and VMAT for flank irradiation due to pediatric Wilms tumor. MethodsTwo computational XCAT phantoms simulating an average 5- and 10-year-old patient were used. Four different planning target volumes (PTVs) for right flank (RF) and left flank (LF) irradiation with or without paraaortic lymph nodes (LNs) and eight surrounding organs-at-risk (OARs) were contoured on the phantoms’ CT sections. Forty-eight 3D-CRT, IMRT and VMAT plans were created using 6 and 10-MV photons on the two phantoms. The target coverage index (TCI), homogeneity index (HI), conformity index (CI), conformation number (CN) and OAR exposure were determined through dose-volume histogram (DVH) analysis. Second cancer risks were estimated using a non-linear model and DVH data. ResultsThe IMRT and VMAT for LF + LN and RF + LN irradiation reduced the radiation dose to four to six out of the eight OARs compared to 3D-CRT. Conventional treatment provided a better organ sparing for RF and LF irradiation. The IMRT and VMAT led to superior planning parameters in respect to 3D-CRT for all PTVs and both patient’s ages (3D-CRT: TCI = 59.80 % - 82.26 %, CI = 0.55–0.81, CN = 0.40–0.64, HI = 1.11–1.15; IMRT: TCI = 96.04 % - 99.72 %, CI = 0.85–0.91, CN = 0.85–0.88, HI = 1.03–1.05; VMAT: TCI = 96.02 % - 99.69 %, CI = 0.86–0.91, CN = 0.85–0.89, HI = 1.03–1.06). The excess-absolute-risk for developing secondary small intestine, liver and stomach malignancies from 3D-CRT were (7.99–19.32) × 10-4, (0.29–3.83) × 10-4 and (0.37–4.50) × 10-4 persons-year, respectively. The corresponding risks from intensity modulated techniques reached to 22.26 × 10-4, 4.58 × 10-4 and 5.42 × 10-4 persons-year. ConclusionsThis dataset related to plan quality, radiation dose and risks to OARs allows the selection of the proper treatment technique for flank irradiation based on the patient’s age and target site.

Establishment of institutional diagnostic reference levels for 6 adult computed tomography examinations: Results from preliminary data collection

Computed tomography (CT) is the leading source of the cumulative effective doses to the general populace from medicinal and artificial sources. With the increased use of CT examinations comes the concern regarding the health effects of unnecessary radiation exposure and the need to optimize the doses that patients receive. The current study evaluates the patients' doses during specific CT procedures and establishes institutional diagnostic reference levels (DRLs) for the frequent CT scans performed. 8156 CT scan examinations were performed during three years from 2015 to 2018 using a single CT scan machine at our institution. Data from the six most common examinations were analyzed. The volume CT dose index (CTDIvol (mGy)) and dose length product (DLP) distribution's median and 75th percentile values were computed. The results were descriptively compared with DRLs from different countries and regions. The six most common examinations constituted 5815 studies. We established our DRLs as the median value of CTDIvol (mGy)| and DLP (mGy × cm) as follows: CT of the brain: 35.0 mGy and 839 mGy× cm, respectively; chest with contrast: 4 mGy and 148 mGy-cm, respectively; chest without contrast: 5 mGy and 190 mGy-cm, respectively; abdomen and pelvis with contrast: 8 mGy and 636 mGy-cm, respectively; abdomen and pelvis without contrast 8 mGy and 568 mGy-cm, in that order; abdomen, pelvis, and kidneys: 11 mGy and 458 mGy× cm, respectively. Our values for brain and chest CTs were lower than the international DRLs, while those for abdominal imaging were higher. The established DRLs offer an opportunity for us to optimize the dose delivered to patients and compare them to the national benchmarks when they are issued. The study revealed that CT dose showed wide discrepancies for the same procedures at the department levels suggesting that the practice was neither optimized nor harmonized. Therefore, DRL should be reassessed after the operators' training and awareness to reduce the patients' dose and related radiogenic risk to its minimal value.

Effective radiation dose and radiogenic cancer risk during contrast enhanced abdominal computed tomography examinations

Pediatrics and children have higher radiosensitivity to ionizing radiation and radiogenic risks than adults due to their rapidly dividing tissues. This study explores the infant and children radiation doses during computed tomography (CT) abdomen and estimates the cancer risk from the procedure. In total, 87 were examined for CT enhanced abdominal examination. The abdominal CT scan with contrast was performed using a 128-slice multi slice CT (MSCT) scan. The mean, standard deviation, and range of patients' age (years) are 13 ± 4.5 (2–17). The mean and range of the air kerma length product (PKL(mGy.cm)) and volume CT air kerma index (Cvol (mGy)) were 1740 (157.8–8440.3) (mGy.cm) and 9.8 (2.09–45.77) (mGy) per CT abdomen procedure, respectively. The mean and range of the effective dose (mSv) per procedure are 34 (3.14–176.8). The average radiogenic risk per CT procedure is one cancer incidence per 250 CT enhanced abdomen procedures. The mean and range of total irradiation even are 4.0 (2.0–8.0) times per procedure. The results of this study showed that child risk is high compared to other CT examinations. Therefore, patients’ dose optimization and proper establishment of a diagnostic reference level (DRL) are necessary to preventing avoidable radiation risks.

Estimate of effective dose for adult patients from nuclear medicine examinations in Sudan

Artificial radiation is the primary radiogenic risk source to the general population. Medical field has been growing in Sudan. This study aims to estimate effective doses for adult patients from nuclear medicine examinations. The study involved 685 patients from five different hospitals in Sudan. In total, 300, 196, and 189 patients underwent renal, thyroid, and bone scans. All procedures were carried out using the Tc-99m radionuclide. Effective dose has been estimated using computer software depending on conductive activity. The results show that dose information for patients from thyroid, renal, and bone scan, for thyroid scan the patients' age was 42.82 ± 16.46 years, the patient's weight 68.58 ± 12.82 kg, the activity 4.75 ± 0.543 mCi and the effective dose for thyroid was 2.28 ± 0.26 mSv. For renal scan, the patients' age 45.19 ± 16.36 years, the weight 65.96 ± 13.78 kg, the activity 5.21 ± 1.166 mCi, and the effective dose 0.94 ± 0.211 mSv. For a bone scan, the patients' age was 57.59 ± 14.92 years, the patient's weight was 69.48 ± 13.71 kg, the activity 19.96 ± 2.11 mCi, and the effective dose for bone was 4.208 ± 0.443 mSv. The study revealed that the administered activity is independent of patient weight. Patients received unjustified exposure due to the high amount of administered activity. Implementation of national guidelines is necessary to improve the practice and patient safety.

Effective radiation doses in neck computed tomography scans

A significant source of ionizing radiation for medical use is computed tomography (CT). According to estimates, more than 84 million CT scans are carried out yearly in the US. Because the neck area contains several organs and tissues that are very sensitive to ionizing radiation, such as the thyroid gland, CT for the neck region is commonly done for a variety of clinical causes. This study's goal is to assess the patient doses to radiosensitive organs and effective doses received during the CT neck surgery in the pastAt Riyadh Care Hospital, a multislice CT (MSCT) system (Siemens Somatom Sensation, 64 slices/detector) was used to perform improved CT treatments on a total of 54 patients. Patient ages were 41.5–15.5 years old on average, with a wide variation (21–73). Using computer software based on Monte Carlo simulation, organ and effective dosages were assessed. The International Commission of Radiological Protection (ICRP) risk variables were used to calculate the patient's radiogenic risk for a particular organ. The patients' dose length product (DLP, mGy.cm) for CT neck examination were 993.3 ± 539.5 (267.3–2441.7). The mean and range of volume CT dose per slice (CTDIvol (mGy)) were 1.5 ± 3.9 (3.91–22.55). The overall effective dose (mSv) per procedure is ranged from 1.3 to 11.7 with a mean value 2.8 mSv. Patients' CT neck procedures have been repeated the procedure up to 7 times during the treatment course. The risk of malignancy is 1x10-6 CT procedure. The study showed that patients received wide discrepancies in patients' doses up to 9 times. Optimization of image acquisition protocol and scan length is necessary to reduce the unnecessary risk.

Incidence risks for cerebrovascular diseases and types of stroke in a cohort of Mayak PA workers.

Incidence risks for cerebrovascular diseases (CeVD) and some types of stroke in a cohort of 22,377 Russian Mayak nuclear workers chronically exposed to ionising radiation and followed up until the end of 2018 are reported. Among total 9469 cases of CeVD, 2078 cases were strokes that included 262 hemorrhagic strokes (HS) and 1611 ischemic strokes (IS). Data evaluation was performed with categorical and dose-response analyses estimating the relative risk (RR) and excess relative risk (ERR) per unit cumulative liver absorbed dose of external gamma-ray or internal alpha-particle exposure based on a linear model utilizing the AMFIT module of the EPICURE software. CeVD incidence was found to be significantly associated with cumulative radiation dose: ERR/Gy was 0.37 (95% confidence interval (CI) 0.27, 0.47) in males and 0.47 (95% CI 0.31, 0.66) in females for external exposure, and 0.31 (95% CI 0.11, 0.59) in males and 0.32 (95% CI 0.11, 0.61) in females for internal exposure. When the model for the analysis of external radiation effect did not include an adjustment for alpha radiation dose (and vice versa), the radiogenic risk estimate increased notably both for males and for females. In contrast, exclusion from or inclusion in the model of additional adjustments for non-radiation factors did not notably change the risk estimates. ERR/Gy of external gamma dose for CeVD incidence significantly decreased with increasing attained age (males and females) and duration of employment (females). No significant associations of either stroke or its types with cumulative gamma-ray dose of external exposure or alpha-particle dose of internal exposure were found.

АНАЛИЗ РИСКА СМЕРТИ ОТ ЦЕРЕБРОВАСКУЛЯРНЫХ БОЛЕЗНЕЙ ЛИКВИДАТОРОВ ПОСЛЕДСТВИЙ АВАРИИ НА ЧАЭС, РАБОТНИКОВ АТОМНОЙ ПРОМЫШЛЕННОСТИ

Purpose: Assessment of the risk of death of the liquidators of the Chernobyl accident from cerebrovascular diseases. Material and methods: The risk of death of liquidators of the Chernobyl accident from cerebrovascular diseases (ICD 10: I60-I69.9) was estimated using the Industry Register of persons exposed to radiation as a result of the Chernobyl accident over a thirty-year period, with a verified dose of external exposure obtained by operating in the 30 km zone of the Chernobyl NPP. The study included men - 12,663 people, 1327 of them have a dose of occupational exposure. Rough relative risks of mortality from cerebrovascular diseases were evaluated for five dose groups based on internal control. At the second stage of the study, all data were stratified by age, dose load and Follow up period. Based on the obtained stratified data file, the Poisson regression procedure was carried out, for which the Epicure AMFIT module was used and the magnitude of the excess relative risk (ERR) of death from cerebrovascular diseases was calculated and the nature of the dose dependence of EI was investigated. A cohort epidemiological study of a group of liquidators of 1986-1990 was conducted over a thirty-year period, depending on the dose, both obtained during the liquidation of the consequences of the Chernobyl accident and during work with radioactive substances (RS) in the profession. Results: For the first time, direct estimates of the radiogenic risk of death from cerebrovascular diseases have been obtained. A risk decrease in this type of death per unit dose was shown for dose loads implemented during the liquidation of the consequences of the Chernobyl accident and professional doses too. Conclusion: Liquidators in the long-term after the work on eliminating the consequences of the accident need generally accepted medical care approaches aimed at preventing and treating such common diseases as cardiovascular diseases. The results can be used in the development of radiation safety regulation.

Риск заболевания нетоксическим зобом ликвидаторов последствий аварии на Чернобыльской АЭС, работников предприятий атомной промышленности

Estimates of radiation risk of non-toxic goiter (ICD 10: E04-E04.9) in Chernobyl liquidators were given from the information database of the Sectoral register of persons exposed to radiation as a result of the Chernobyl accident for 1989-2018. Used dosimetry information contained liquidators radiation doses were measured during their work inside the Chernobyl exclusion zone, and the employees’ occupational radiation dose. The study used information about men − 12663 people, of which 1327 workers have an occupational exposure dose. At the first stage, the excess relative risk per 1 Sv (ROR/Sv) of non-toxic goiter was estimated for four groups depending on age at the time of participation in work in the Chernobyl accident zone. At the second stage of the study, a Poisson process with an intensity parameter was chosen as a statistical model of morbidity. Based on the obtained individual non-stratified data, an analytical likelihood function for the Poisson process was built and the value of the excess relative risk (RRR) of the disease with nontoxic goi-ter was calculated. The nature of the dose dependence of the IOR was studied, for which the Amfit module of the Epicure statistical software package was used. A cohort study of liquidators 1986-1990 was carried out. for 1989-2018 depending on the dose of external exposure received during the liquidation of the consequences of the Chernobyl accident, and with the total dose received in the 30-km zone of the Chernobyl nuclear power plant with the dose during professional work. The values of the radiogenic risk of non-toxic goiter in liquidators of the consequences of the Cherno-byl accident are shown. A significant increase in the risk of IOR disease per dose unit for doses received during the liquidation of the consequences of the Chernobyl accident was not found. A significant increase in risk was noted when using total doses for its calculation only for liquidators in the age group of 50-59 years. The use of doses from various types of exposure in assessing the radiogenic risk of non-toxic goiter in liquidators of the consequences of the Chernobyl accident gives different values of the excess relative risk of developing this nosology. For a correct as-sessment of the radiation risk of non-toxic goiter, it is necessary to collect data on the doses of all types of exposure (occupational, emergency, medical and natural), and only the use of the total dose can give the true risk necessary to calculate the radiation safety standards.

Elimination of biological and physical artifacts in abdomen and brain computed tomography procedures using filtering techniques

IntroductionMedical images are usually affected by biological and physical artifacts or noise, which reduces image quality and hence poses difficulties in visual analysis, interpretation and thus requires higher doses and increased radiographs repetition rate. ObjectivesThis study aims at assessing image quality during CT abdomen and brain examinations using filtering techniques as well as estimating the radiogenic risk associated with CT abdomen and brain examinations. Materials and MethodsThe data were collected from the Radiology Department at Royal Care International (RCI) Hospital, Khartoum, Sudan. The study included 100 abdominal CT images and 100 brain CT images selected from adult patients. Filters applied are namely: Mean filter, Gaussian filter, Median filter and Minimum filter. In this study, image quality after denoising is measured based on the Mean Squared Error (MSE), Peak Signal-to-Noise Ratio (PSNR), and the Structural Similarity Index Metric (SSIM). ResultsThe results show that the images quality parameters become higher after applications of filters. Median filter showed improved image quality as interpreted by the measured parameters: PSNR and SSIM, and it is thus considered as a better filter for removing the noise from all other applied filters. DiscussionThe noise removed by the different filters applied to the CT images resulted in enhancing high quality images thereby effectively revealing the important details of the images without increasing the patients’ risks from higher doses. ConclusionsFiltering and image reconstruction techniques not only reduce the dose and thus the radiation risks, but also enhances high quality imaging which allows better diagnosis.