Medical diagnostics procedures involving the use of ionising radiation is one of the most intensively developing areas in medical diagnostics. At the same time, medical exposure of patients has a number of fundamental differences from other routine situations of planned exposure. As a rule, medical exposure is acute, and radiation doses in some types of examinations exceed the level of natural and man-made exposure associated with normal operation of radiation facilities. In such a situation, risk differentiation is of great importance, taking into account the different radiosensitivity of individual sex and age groups of patients. Radiation risks should be taken into account both when prescribing examinations involving the use of ionising radiation and when analysing the benefit-harm ratio associated with their application to specific patients. Another reason why risk assessment is an urgent task is the need to inform patients and/or their legal representatives about the health risks associated with the carrying out of examinations, including radiation risks. Within the framework of the present work, the risks associated with fluoroscopic examinations were assessed. To characterise the risk we used the DALY indicator, which is more and more frequently used in risk assessment, reflecting the possible number of lost years of healthy life as a result of radiation exposure during the study. The aim of the work was to calculate DALY values for different sex and age groups of patients from the Russian population  during fluoroscopic examinations. To achieve this aim, the method of estimating the number of healthy life years lost due to exposure to ionising radiation, which was developed in the course of the research work, was used. The paper presents the results of calculating DALY values for three types of fluoroscopic examinations. This work represents the next step in the direction of harmonisation of radiation risk assessment methodology with the methodologies of risk assessment of other nature. One of the directions of using the calculation results is the development of methodological approaches to the calculation of sex- and age-dependent risk coefficients associated with medical exposure of patients. The analysis of the obtained results showed that the contribution of oncological diseases to the total radiation harm in older men was significantly higher than in women.

In case of radiation accidents, one of the radical protective measures is the evacuation of residents from contaminated areas. Its purpose is to reduce the possible radiation effect to the population. At the same time, evacuation itself becomes a serious stressful factor that has a negative impact on a person’s health and mental status. The objective of this work is to assess the state of mental health of residents of the Muslyumovo settlement in the Chelyabinsk region (the territory exposed to radioactive contamination as a result of radioactive waste releases into the Techa River) who participated in the resettlement program in the period from 2006 to 2010. Mental health was assessed twice: primarily in 2008-2010 against the background of resettlement, and again in 2019-2020, 10 or more years after the resettlement. The study includes 2 groups formed by random selection. The main group consisted of 100 persons from among the participants of the resettlement program. The comparison group included 80 persons living in the territories exposed to radioactive contamination, but not participating in the resettlement program. According to the main socio-hygienic characteristics, the groups are homogeneous and comparable. The following methods were used: clinical, clinical and psychological, and the method of statistical processing of materials. As a result, it was found that both in the primary and in the repeated study, residents of the Muslyumovo settlement, Chelyabinsk region, participating in the resettlement program, were statistically significantly more likely (p<0.001) to have mental disorders and behavioral disorders (neurotic, stress-related and somatoform disorders (F 40)), compared with the control group. Also, according to the results of the survey, statistically significantly more often the psychogenic effect of resettlement (p≤0.001) was detected in patients of the main group. The data obtained suggest a long-term effect of resettlement on the mental health of the population involved. Understanding the consequences of the protective measures carried out (resettlement) will clarify the criteria for their application, as well as predict the manifestations of mental maladaptation in the population with the potential development of radiation accidents.

In cases of intake of higher levels of plutonium, a chelate diethylenetriaminepentaacetic acid is used to enhance the elimination and reduce deposition rate in the organs of major deposit in the form of calcium compound Ca-DTPA (pentacinum). To interpret the results of the nuclide measurements in excreta while estimating the doses of internal exposure to plutonium, the biokinetic and dosimetry models recommended by ICRP are applied; and in case of the actinide intake through damaged skin it is recommended to use the models of NCRP of the USA. Since the application of chelates significantly changes the picture of plutonium urinary excretion, special models of complex Pu-DTPA behavior are developed to describe the plutonium biokinetics in presence of chelates. The purpose of this work is to assess the suitability of a special model of plutonium behavior in presence of chelates elaborated by K. Konzen to describe the plutonium biokinetics in the body by the cases of wound intake of industrial plutonium compounds in the FSUE Mayak PA workers. This study used the measurements of plutonium activity in daily amount of urine for three cases with the actinide intake through damaged skin and Ca-DTPA treatment, the duration of pentacinum application and observation periods for workers depending on the levels of intake. For each case, the most likely type of an entered compound was selected using Akaike information criterion, then the daily urinary activity of plutonium was calculated by the model (estimated value) on the same days when it was determined actually (actual values). The analysis of the compliance of calculated data with actual data was conducted using the statistic tests of Foster-Stewart,Breusch-Godfrey, Mann-Whitney, Shapiro-Wilk, and the determination coefficient. It was found that for all cases considered, the adjusted determination coefficient and Foster-Stewart test indicated the compliance of actual data with calculated ones. The statistical analysis of the compliance of calculated data with actual measurements of plutonium urinary activity showed that the special model of plutonium behavior proposed by K. Konzen was able to predict the urinary activity of plutonium during both the radionuclide decorporation measures and the period of pentacinum aftereffect.

A comprehensive radiation survey of settlements in six districts of the eastern part of the Orenburg region in terms of exposure to natural sources of ionizing radiation, carried out in 2019, revealed numerous exceedances of the hygienic norm (action level) for indoor radon concentration in residential and public buildings. It was found that among other studied factors, exhalation of radon from the ground under the buildings is the main source of high levels of public exposure. Due to the lack of funding for the continuation of the survey in 2020, specialists of St. Petersburg Research Institute of Radiation Hygiene after Professor P.V. Ramzaev, Directorate of Rospotrebnadzor in the Orenburg region and the Center of Hygiene and Epidemiology in the Orenburg region needed to develop new approaches to survey planning. These new approaches should provide maximum amount of measurement information necessary to ensure radiation safety of the region’s population, with minimal financial investments and labor costs. Indoor radon concentration in residential and public buildings was undoubtedly chosen as the studied factor, and the integrated measurement method using SSNTDs was chosen as the most suitable method for the objectives of the survey due to its scalability and ease of detectors deployment. Since exposure to radon and its progeny is the second leading cause of lung cancer after smoking, the selection of priority districts of the region for the radon survey was based on average standardized trachea, bronchi, and lung cancer morbidity rates in the districts of the Orenburg region for 2009-2018. The survey conducted in 2020-2023 revealed exceedances of the hygienic norm (action level) for indoor radon concentration in five of seven surveyed districts. By 2025 it is planned to conduct radon surveys in three more districts of the Orenburg region with increased respiratory systems cancer morbidity rates.

The usage of modern positron emission tomography scanners, in particular with digital detectors, allows obtaining images with better quality, increases the detection of small pathological lesions, reduces scanning time and the activity administered to the patient which leads to a decrease of patient dose as well. However, the values of the quantitative image parameters shift upward, which can lead to significant differences with the quantitative assessment obtained on the previous generation device. In order to compare quantitative assessments obtained on different generations of PET/CT, it is necessary to harmonise quantitative image parameters and perform regular quality control. The aim of current work is the comparison of different methods for harmonization of quantitative image parameters on the example of harmonisation of two PET/CT: Biograph mCT 128 and Biograph Vision 600. NEMA IEC Body phantom filled with 18F solution was scanned in Listmode in two bed positions with overlap in the sphere area during five minutes per bed position. Recovery coefficient used for harmonisation was measured for each sphere of the phantom. Harmonisation between Vision and mCT was performed using two methods: choosing of harmonised reconstruction parameters and EQ.PET technology. The acceptable divergence range between the recovery coefficients for Vision and for mCT is ±10% (20% range). The recovery coefficients measured for reconstruction: 4 iterations and 5 subsets, ToF+PSF, Gaussian 7 mm, matrix 220x220 completely fit within the 20% range. The recovery coefficients measured using EQ = 6 mm (optimal value) fit within the 20% range except the spheres with a diameter of 10 and 13 mm. Both harmonisation methods allow to approximate the quantitative assessment/ However, EQ.PET has limitations for the small lesions. Choosing harmonised reconstruction parameters is the mostwidely used harmonisation method; the EQ.PET allows to harmonise quantitative assessment without the use of multiple reconstruction protocols and losses in visualization ability

An open plot of virgin land is the reference location in the basic model used to date to estimate the effective dose of external exposure to the population living in a radioactively contaminated area. As our field observations in the Bryansk region of Russia have shown, at present it is very difficult to find truly reference plots of virgin land due to the fact that many virgin meadows were plowed or reclaimed for more than 30 years after the Chernobyl accident. Without special instrumental survey, such disturbed meadow areas can easily be confused with areas of virgin soil. Therefore, the situation with the use of open areas of virgin soil as the reference location has changed dramatically since the first years after the Chernobyl accident. It requires a change in the approach to choosing such a location for the model and/or some revision of the structure of the model itself. Firstly, we propose and justify the use of a permanently cultivated kitchengarden plot as the reference location. The second way to resolve the current difficult situation with the presence of a sufficient number of the virgin soil sites could be excluding the very concept of “reference location” from the model. In this case, when calculating the effective dose of external radiation, it is proposed to directly use the values of the gamma radiation dose rate in the air normalized to the 137Cs contamination density of soil. The values of the normalized dose rate should be experimentally determined in the required time period for each of the locations taken into account in the model.

Computational phantoms are used to calculate the doses of internal exposure of active bone marrow. The computational phantoms of ICRP were created for a reference man with anatomical characteristics typical of an average individual. The doses calculated with such phantoms correspond to population-average values. Individual variability introduces a stochastic component of uncertainty into the dose estimation. The objective of this study is to assess the effect of individual variability of bone structure dimensions on the results of dosimetric modeling. The phantoms are represented by simple geometry figures filled with trabecular structures and bone marrow (spongiosa), covered externally with a cortical layer. The models of bone geometry are described by parameters characterizing the linear dimensions, the microarchitecture of the spongiosa (trabecular thickness, trabecular separation, bone volume fraction), as well as the cortical layer thickness. By varying these parameters, sets of phantoms were generated to simulate the individual variability of bone geometry. The mean absorbed dose rate in active bone marrow from a single decay of ⁹⁰Sr/⁹⁰Y was calculated assuming isotope distribution either in the volume of the trabecular or cortical bone. All estimates are on the example of the phantom of an adult male skeleton. The individual variability of the main parameters of segment computational phantoms depends on size and equal to: a) for linear dimensions – 12-15%; b) for bone volume fraction – 22-24%; c) for cortical thickness – 21-23%. This leads to uncertainties of dose rate estimation equal to 21% – 25%.

The need to study and evaluate the leading protective mechanisms of the respiratory system remains one of the key, but unresolved problems of modern medicine, concerning both radiation hygiene and toxicology, and pulmonology. The model of the respiratory tract presented by the ICRP only partially addresses them, significantly limiting the feasibility and possibilities of its use. The solution of this problem undoubtedly contributes to the improvement of methods of prevention and treatment from the effects of incorporative radionuclides entering by inhalation, as well as methods for diagnosing and treating respiratory diseases aimed at the earliest stages of their pathogenesis, given that the processes of deposition of inhaled substances and lung clearance directly depend both therapeutic and pathogenic effects. This is especially relevant when there is a danger of contamination with radioactive waste, when there is an urgent need to deal with highly pathogenic influence and its consequences. The most informative method for studying the processes of deposition inhalant and mucociliary clearance is radioaerosol. However, due to the circumstances, there are no radiopharmaceuticals that could be used for such a study since the 2000s, which prompted us to carry out this work. At the same time, albumin microspheres labeled with ^99mTc are considered potentially suitable, but not studied radiopharmaceuticals in this regard. The aim of the work was to study the aerodynamic properties of albumin microspheres and evaluate the possibilities of their use for radioaerosol study of the processes of deposition of inhaled substances and mucociliary clearance. The aerodynamic properties of albumin micro[1]spheres were studied using optical and scanning electron microscopy by studying their dry dispersion, initial and obtained from its suspension in distilled water, generated by an ultrasonic inhaler according to the developed technology. The results indicated that the dispersible particles were characterized by sphericity, clear boundary differentiation and a relatively homogeneous distribution of particles with a relatively narrow size range (spread 1-2.5 µm) and little conglomeration, as well as a smooth surface. Conclusion. The investigated albumin microspheres are suitable for radioaerosol study of the processes of deposition of inhaled substances and mucociliary clearance.

The objective of the current study is the direct assessment of the excess relative risk of solid cancer mortality in people affected by low dose-rate chronic exposure mainly in low-to medium dose range (up to 1 Gy) at the age of <20. The study cohort consists of the population exposed at the age of <20 as a result of two large radiation accidents at the “Mayak” Production Association. The size of the cohort is 32,762 persons, follow-up period – 71 years (from 1950 through 2020), the number of person-years at risk is – 1 218 855. For this cohort the mortality catchment area includes Chelyabinsk and Kurgan Oblasts. Over a 71-year follow-up period 1,788 solid cancer deaths were registered in the cohort. Mean dose accumulated in the stomach walls over the whole follow-up period was 0.04 Gy, maximum dose was 1.1 Gy. Statistical processing of data was performed using Amfit and Datab software packages (Epicure statistics software package). Solid cancer mortality risk was analyzed with the Poisson regression using simple parametric excess relative risk model. Statistical significance of the results was estimated using the maximum likelihood method with 95% probability. For the first time the direct assessments of the excess relative risk of solid cancer mortality have been obtained in the Urals Cohort of population exposed at age <20 for a 71-year period (Excess Relative Risk was 0.84/Gy, 95% confidence interval: 0.24-1.55 for 10-years minimal latency period and 0.83 (0.24-1.55) for 5-year minimal latency period). Statistically significant estimates of the excess relative risk have been obtained for specific groups within the cohort selected according to the sex, age at the onset of exposure, and Oblast of residence at the time of exposure.

We have tested applicability of the commercially available portable spectrometer-dosimeter MKS AT6101D (the manufacturer: ATOMTEX, Belarus) to measure the density of ¹³⁷Cs soil contamination (inventory of ¹³⁷Cs in soil) in situ. The study was performed in 2015–2020 at the territories of the Bryansk region of Russia contaminated due to the Chernobyl accident. The in situ measurements were performed in the 17 ground plots (7 grasslands and 10 kitchengargens) for which the ¹³⁷Cs inventory and the mean migration depth of the radionuclide in soil was available from laboratory (ex situ) measurements of soil samples. It was found that the in situ data obtained with the method that was provided by the manufacturer of the instrument required additional correction on the vertical distribution of ¹³⁷Cs in the soil. The correction procedure was developed; in 2020–2021, it has been successfully tested in 114 kitchengarden plots located at the settlements in the zones of radioactive contamination in the Bryansk region.

Introduction of new methods of nuclear medicine, X-ray diagnostics and therapy using medical sources of ionizing radiation inevitably leads to an increase in the number and types of accidents (abnormal situations). In international practice in recent years, special attention has been paid to the prevention of radiation accidents and incidents from medical exposure. The main focus is put on accidental exposure (overexposure) of patients in X-ray and radionuclide diagnostics and therapy. These approaches are implemented in Russian regulatory and methodological documents in a limited and formal way. The main attention is paid to large-scale technogenic radiation accidents, and accidents (abnormal situations) from medical irradiation are undeservedly ignored. The aim of the work was to analyze the terminology and classification of radiation accidents and incidents from medical exposure in the Russian Federation and foreign countries to develop proposals to improve approaches to their classification within the framework of revision of existing regulatory and methodological documents. The results of the work indicate that it is necessary to actualize Russian approaches to the definition and classification of radiation accidents in medicine considering the specifics of medical exposure. For this purpose, it is advisable to introduce different levels of accidents (abnormal situations), differing from each other by the scale of impact and consequences for patients, workers and public. Considering the absence of elaborated scenarios of accidents (abnormal situations) in Russian regulatory and methodological documents, such gradation can be borrowed from international regulatory documents provided that it is adapted to the specifics and realities of the Russian health care system

In accordance with the fundamentals of state policy in the field of ensuring nuclear and radiation safety, State Corporation «Rosatom» carries out the remediation of JSC “AECC” nuclear legacy sites. The article presents the results of environmental impact assessment carried out in 2021-2023 in the vicinity of sublimation waste storage facilities that are being decommissioned. Health physics studies involved ambient dose rate measurements, sampling (soil, groundwater) and analysis of radiological and non radiological environmental pollutants. The external gamma dose rate, as well as content of natural and artificial radionuclides in soil, don’t exceed background levels. While uranium presence in groundwater is found to be 10 times and higher then background level. The data obtained indicate that the accumulated wastes of sludge sumps (bottom sediments, pulp) сome into contact with natural water. Flooded storage facilities form a plume of contamination spreading out in the direction of groundwater flow. Given the current situation optimization of the existing environmental monitoring programs in the JSC “AECC” health protection zone is recommended and reference levels of uranium proposed.

The article presents results of a study of the radiation environment on territories adjacent to the sites of the “Globus-4” and “Gorizont-1” peaceful nuclear explosions in the Komi Republic. Field survey was carried out in July 2021. The work provides an assessment of the radiation situation in terms of the main indicators: ambient dose equivalent rate, the content of anthropogenic radionuclides in soil, tritium in the water of water bodies and drinking water supply sources in the settlements nearest to the sites of the peaceful nuclear explosions. The values of gamma radiation ambient dose equivalent rate in all the surveyed territories are at the level of fluctuations of natural regional radiation background and amounted to 0.03 – 0.07 µSv/h in the territory of peaceful nuclear explosion “Globus-4”, 0.01 – 0.05 µSv/h in the territory of “Gorizont-1”. No contaminated soil areas with anthropogenicradionuclides were detected. Tritium activity concentration in water samples does not exceed 5 Bq/kg, which is typical for global levels of this radionuclide in water bodies. The study has shown that the radiation situation in the territory of peaceful nuclear explosions “Globus-4” and “Gorizont-1” meets the requirements of SanPiN 2.6.1.2819-10 “Ensuring radiation safety of the population living in the areas of (1965 – 1988) nuclear explosions for peaceful aims” and currently poses no threat to public health. A conservative dose estimate of additional anthropogenic exposure of individuals from the population from tritium intake with water from centralised water supply sources was 0.065 µSv/year. Longterm radiation safety of the researched territories requires organisation of radiation monitoring, determination of protected zone boundaries and installation of readable information signs warning about radiation hazard and prohibition of economic activities.