The article describes a model and method for calculating beta-exposure doses to secretory and basal cells of the tracheobronchial part of the respiratory tract when a point source of 1 Bq activity moves along the inner surface of respiratory formations. The calculations, that used for proposed model, were performed by using a ⁹⁰Y point source as an example. The dose calculation model takes into account the speed o f movement of the radiation source in each respiratory formation, the size of the respiratory formations, and the depth of the secretory and basal cells. The dose calculation is based on  the dose rate attenuation functions published by W. G. Cross et al.  (DOI: 10.1097/00004032-199208000-00002). The calculations were performed for a cylindrical model of a respiratory formation. Two kinds of cells were considered for the dose estimation: cells irradiated without beta-particle exit into bronchial lumen (type 1 cells) and cells irradiated due to beta-par­
ticle exit into bronchial lumen (type 2 cells). The results of calculations showed, that as far as the generation number increasing, the average irradiation doses of the type 1 cells are 10 or more times greater than those of the type 2 cells. With increasing generation number in the tracheobronchial tree, doses per cells increase by several orders of magnitude. The highest doses are formed in bronchioles of generations 9-15, reaching units and tens of mGy. In spite of the fact that the number of generation increases, the total number of irradiated cells decreases, the collective doses of irradiated cells (sum of doses to all cells of the respiratory formation) in the last generations are 30-50 times higher than the doses of the first generations. Thus, in case of a single point source, there is a significant (by many orders of magnitude) scatter of doses to individual cells in indi­vidual respiratory formation, as well as significant differences in average doses of trachea, individual bronchi and bronchioles.

Assessment of the lymphocyte doses is relevant for solving a number of radiobiological problems, including the risk assessment of hemoblastosis (leukemia, multiple myeloma, lymphoma etc.), as well as the use of circulating lymphocytes as “natural biodosimeters”. The latter is because the frequency of chromosomal aberrations occurring in lymphocytes following radiation exposure is proportional to the accumulated dose. Assessment of doses to the circulating lymphocytes requires due account of: first, the dose accumulated by the lymphocyte progenitors in the red bone marrow; and second, the dose accumulated during lymphocyte circulation through lymphoid organs. The models presented by International Commission on Radiological Protection (ICRP-67, ICRP-100) allow calculating the dose for specific lymphoid organs based on known level of radionuclide intakes. A recently developed model of circulating T-lymphocyte irradiation takes into account all sources of exposure and age-related dynamics of T-lymphocytes: (1) exposure of lymphocyte progenitors in red bone marrow: (2) exposure of T-lymphocytes in the lymphoid organs, taking into account the proportion of resident lymphocytes and the residence time of circulating lymphocytes in the specific lymphoid organs. The objective of the study is to assess the dose coefficients allowing for the transition from the ingestion of ^141,144Ce, ⁹⁵Zr, ^103,106Ru, ⁹⁵Nb to the doses accumulated in circulating T-lymphocytes. For calculations, we used the dose coefficients from ICRP publications for specific lymphoid organs, as well as published data on the residence time of circulating lymphocytes in lymphoid organs and tissues. As a result, it was shown that the doses in circulating T-lymphocytes are higher than those in the red bone marrow, but lower than the doses to the colon wall. The dose coefficients were age dependent; the maximum values were typical for newborns. The obtained dose coefficients for ^141,144Ce, ⁹⁵Zr, ⁹⁵Nb and ^103,106Ru can be used to estimate the tissue and organ doses based on data on the frequency of chromosomal aberrations in peripheral blood lymphocytes.

According to the analysis of requests for methodological assistance to the Saint-Petersburg Research In ­stitute of Radiation Hygiene after Professor P. V. Ramzaev, measurements of radon concentration (or radon EEC) in existing operated public buildings (primarily children institutions) in the framework of surveillance actions in the regions of the Russian Federation, as a rule, are taken according to Guidelines MU 2.6.1.2838-11, intended for radiation control of public buildings only when they are put into operation after construction, major repairs or reconstruction, due to the absence of special guidelines. Compliance with the requirements of paragraph 6.5 of MU 2.6.1.2838-11 means that the building and premises are in a state that is not equal to their normal operation mode. Registration of high values of indoor radon concentration in this case leads to management decisions, including administrative suspension o f activities for up to ninety days, i.e. the closure of individual premises or even the entire building of a children institution. The consequences of making such decisions may include an increase in social tension in society and provoking radiophobia among the population. The paper presents specific recommendations for the radon survey for existing operated public buildings with non-round-the-clock stay of people, which are based on the results of the analysis of the experience of practical application of various methods of measuring indoor radon concentrations in such buildings in order to assess average radon concentration during working hours in the normal operation mode. The proposed approach can be further used as the basis for developing special guidelines for radiation control of existing operated public buildings with non-round-the-clock stay of people. 

An application of geometric mixed additive-multiplicative models for lung cancer risk modeling under combined action of radon and smoking is justified in this paper. The geometric mixed model allows: 1) to reduce the discrepancies between estimates of the lung cancer risk for males and females, 2) to predict the population risk under condition of the varying smoking prevalence and changing average indoor radon concentration level. Using the geometric mixed model, the calculation of the lung cancer risks for the Russian Federation population was carried out for different percentages of smokers among the population, an increase in life expectancy, and a change in the average radon concentration level in residential buildings. Assuming that currently rounded average indoor radon concentration in Russia is 50 Bq/m³, the contribution of radon to total mortality in 2009 was 0.46% and 0.20% for male and female, respectively. Modeling has shown that the effect of lung cancer mortality reducing due to the predicted decrease in the proportion of smoking population will partly be offset by an increase in the realization of lung cancer risk with the life expectancy increase. For a hypothetical situation, when the entire population maintain a healthy lifestyle and mortality from cardiovascular, oncological, infectious diseases, diseases of the respiratory tract and from external causes has significantly decreased, the contribution of radon exposure to total mortality will increase to about 0.8%. If the average level of radon in buildings will increase due to energy-efficient technologies widespread implementation in building construction, the contribution of radon to total mortality will be even more noticeable. 

The aim of the study was to develop a methodology for assessing radiation risk for patients undergoing medical examinations in the Russian Federation. The methodology is based on the risk model of the ICRP Publication 103, the coefficients of lifetime radiation risk for the Russian population and the results of evaluating the doses of patients in the Russian Federation. For thirty examinations that define about 80% of the collective dose of the population of the Russian Federation from medical exposure, the radiation risk was calculated using «gold standard», — the organ doses and the corresponding sex/age risk coefficients for the Russian population. For other examinations (with the exception of mammography) the values of the risk coefficients normalized on 1 mSv of effective dose, which is the averaged value for four selected anatomical areas of the body: head, neck, chest and abdominal cavity — pelvis, were used. It is assumed that for such examinations the error of risk assessment will increase relative to the error of risk assessment for the aforementioned 30 examinations not more than 30%. It is shown that risk estimates for some examinations calculated using the “gold standard” may differ from such estimates on the base of effective dose and nominal risk coefficients averaged by age and the sex to the order of magnitude. 

The objective of the paper is to assess the breast cancer incidence risk in the Ural cohort of accidentally exposed population. The cohort of people exposed in the Southern Urals on the Techa River and in the East Ural Radioactive Trace was created in 2018. This is the first time that breast cancer risk analysis in women in this cohort is being carried out. Over the period from 1956 to 2018, 337breast cancer cases and 741,533person-years at risk were reported in the female subcohort in the incidence catchment area. Mean accumulated dose to the mammary gland, calculated using the TRDS-2016 dosimetry system, was 46 mGy, the maximum dose was 1 Gy. Regression analysis was performed using the EPICURE software package. Statistical significance with 95% probability was assessed by the maximum likelihood method. As a result of the analysis, a statistically significant linear dependence of breast cancer parameters on the dose was obtained. Excess relative risk for the follow-up period from 1956 through 2018 for members of the female subcohort with a 5-year latency period was 2.39 / Gy. The paper also discusses the impact of available for analyses non-radiation factors on both baseline rates of breast cancer incidence and those associated with radiation exposure. These results do not contradict those obtained in the previous study in the Techa River Cohort separately, and in the Japanese L SS cohort of atomic bomb survivors.

Cancer morbidity among patients examined using computed tomography within 10 years follow-up period depending on various factors has been retrospectively analyzed. Information on Ozyorsk residents examined at the Kasli District Hospital was retrospectively collected. The data collection period started in 2009 when the first computed tomography examination has been performed in the X-ray department of Kasli District Hospital, and ended by December 31, 2018. The data obtained in the study were linked to the local Cancer registry, the Death registry, and the “CT Registry” database to receive information about the vital status, cancer morbidity and CT examinations performed outside the Kasli District Hospital. Cumulative incidence has been accounted in terms of predisposed conditions associated with cancer, cancer diagnoses stated before the date of the first CT examination and CT-confirmed malignancy cases. As a result of the study, information on 275 examinations of 246 residents of the Ozyorsk urban district has been derived. By the end of the observation period, 46 cases of malignant tumors were accumulated in the study group. The average time from 1st CT to the end of follow-up was 6.5 years. The distribution of carcinogenic effects among patients examined using CT has been shown retrospectively from the date of birth to the date of the end of follow-up. The cumulative cancer incidence adjusted for predisposing conditions has been compared with the LSS data. No epidemiological data were found on the relationship between the detected cases of malignant tumors and the diagnostic radiation from CT scans. The data obtained in the study provide information on the long-term oncological effects among Ozyorsk residents examined using CT as a source of additional information for a comprehensive assessment of the low dose effects associated with diagnostic exposure in the Ozyorsk Computed Tomography Cohort study.

Computed tomography is associated with high patient doses. CT is actively used for pediatric, however, currently there is no reliable data on the pediatric patient doses in the Russian Federation. The current study presents the data on the anthropometric characteristics of 5, 10 and 15-year-old pediatric patients, as well as the results of a comparative assessment of the effective doses of these patients during CT-examinations of chest, considering their anthropometric data. The effective doses were calculated using three methods: based on the actual guidelines (MU 2.6.1.3584-19) using the age specific conversion coefficients; using the conversion coefficients considered patient body mass and effective diameter; using a specialized software NCICT 3.0. The difference between effective doses according to actual guidelines and considering patient body mass and effective diameter was about 7.1 % (max-65 %). High deviations were observed in patients with abnormally large or abnormally low body mass. Effective doses calculated using NCICT 3.0 were higher compared to doses calculated according to actual guidelines on average by 18 % (max — 53 %). Such differences are explained by the fact that in MU 2.6.1.3584-19 conversion coefficients are presented for the most common CT-scan parameters of protocols, and in NCICT 3.0 the calculation considers individual scan parameters for each patient. The difference between effective doses according to NCICT 3.0 and considering patient body mass and effective diameter was about 32 % (max-70 %). This difference can be explained by the differences in the anthropometric data of some patients, and by the use of different types of phantoms: a stylized phantom (Golikov et al) and a voxel phantom in NCICT 3.0.

In 2011 the International Commission on Radiation Protection established the threshold value of the absorbed dose in the lens of the eye for the development of cataract equal to 0.5 Gy for acute and chronic exposure. A dose limit for exposure of the lens of the eye was established equal to 20 mSv per year, averaged over five consecutive years (100 mSv over 5 years), and 50 mSv for any single year. The Russian regulatory documents specify the dose limit for the exposure of the eye lens equal to 150 mSv per year and there are noclear criteria determining the conditions under which it is necessary to carry out individual monitoring of exposure of the eye lens, but it should be expected that in Russia the dose limit will also be reduced in the coming years. Objectives of the study: assessment of the absorbed doses in the eye lenses of the staff of medical facilities working with radiopharmaceuticals; identification of the relationship between the absorbed dose in the eye lens and the type and range of activities of the radionuclides; justification of the feasibility and identification of categories of staff for regular individual monitoring of the eye lens doses in nuclear medicine departments. Within the framework of the study, the absorbed dose in the eye lens for staff members working with the radiopharmaceuticals in nuclear medicine departments of two medical facilities in St. Petersburg were measured, the possibility of detection of  high eye lens doses for these workers was analyzed. The monitoring period was set to 1 month. The workers were divided into two groups depending on the type of radionuclides in the radiopharmaceuticals they commonly work with: 1) the staff of the PET departments and the radiochemistry units working the with radiopharmaceuticals labeled with positron emitting radionuclides (11C, 18F, 68Ga) 2) the staff of the departments of nuclear medicine working with radiopharmaceuticals labeled with 89Sr, 99mTc. Measurements of the operational quantity Н (3 ) were carried out by the method o f thermoluminescent dosimetry. We used individual dosimeters that met the conditions for determining the operating values. Dosimeters designed to measure Н (3) were located on the collar of a dressing gown without an attenuator. The results of measurements of Н (3 ) indicated that the collected dose depends on the type of the work, the equipment of the nuclear medicine unit, the radionuclide and its activity both at the workplaces and for the entire period of data collection. High dose values were obtained for procedural nurses, radiochemists and technologists who worked with positron-emitting radionuclides (18F, 68Ga and 11C), which, when extrapolated to a year, can exceed 20 mSv. For this category of workers, it is advisable to carry out individual monitoring of external irradiation of the eye lenses after a preliminary assessment of the level of exposure of workers and an assessment of the risks of high doses of the eye lens.

This study is focused on the analysis of the results of the functioning of the Federal Databank on the doses to the public of the Russian Federation from natural and man-made modified radiation background as a part of Joint governmental system of control and accounting of the doses from ionizing exposure in 2001-2020. The mean individual annual effective dose of the public of the Russian Federation from natural sources of ionizing exposure, calculated based on the data from all measurements in 2001-2020, is equal to 3,36 mSv/year. The study includes the analysis of the problems and perspectives of the improvement of the system of the data collection on the levels of exposure of the public of the Russian Federation from natural sources.

The number and contribution of high dose imaging modalities, computed tomography in particular, is rapidly increasing both in the 'Russian Federation and other developed countries. Maximal increase in the number of computed tomography examinations in Russia was observed in 2020 due to the full-scale application of this imaging modality for the diagnostics of the novel coronavirus infection COVID-19. The use of computed tomography for the examination of the chest for the pregnant women is associated with several issues. An internationally accepted approach for the provision of the radiation safety of the pregnant patients is the assessment of the absorbed dose in the fetus after each X-ray examination. However, there are no existingn approved methods for the assessment of the absorbed dose in the fetus in the Russian Federation. The aim of the current study was to assess the doses in the fetus for the pregnant women undergoing computed tomography of the chest due to the COVID-19 and to estimate the probability of the development of the deterministic effects for the fetus. The study was based on the collection of the parameter of Russian and international computed tomography protocols. Parameters of the international computed tomography protocols were collected viameta-analysis of the existing publications; Russian protocols — via data collection in computed tomography departments in St-Petersburg hospitals. Absorbed dose in the uterus of the female patient and effective dose for the fetus were calculated using NCICT 3.0 software for 8, 10, 15, 20, 25, 30, 35 and 38 weeks of pregnancy. The results of the calculations indicate the lack of significant differences between absorbed doses in the uterus and effective doses for the fetus for all stages of pregnancy. Maximal doses for the selected computed tomog­ raphy protocols were in the range of 0.5 mGy (mSv) for 8-25 weeks, 0.6 mGy (mSv) for 30 week, 1.4 mGy (mSv) for 35 week and 2.7 mGy (mSv) for 38 week. The threshold for the development of the deterministic effects equal to 100 mGy cannot be exceeded even for repeated (10-15) computed tomography chest scans. Hence, the use of computed tomography as the primary method of COVID-19 diagnostics and staging will not be associated with the development of deterministic effects in the fetus.