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Today in the Russian Federation, the existing method for assessing patients` effective doses during computed tomography in the form of conversion coefficients from the dose-length product provides for the area from the head to the upper third of the femur but does not consider the possibility of scanning the whole body including the lower extremities. In this case, for some nosologies, the lower extremities may be involved. The aim of the study was to develop conversion coefficients from the dose-length product to the effective dose for whole-body computed tomography scanning including the patient's lower extremities. The coefficients for whole-body computed tomography scans (including the lower extremities) were determined for a sample of computed tomography scanners that are part of positron emission tomography combined with computed tomography devices of different models for adults and children of different age groups. In NCICT 3.0 software absorbed organ doses were calculated taking into account the specific model of devices and scan length. Effective doses were determined in accordance with the methodology presented in Publication 60 of the International Commission on Radiological Protection and Radiation Safety Standards 99/2009. Separately, conversion coefficients were developed from the dose-length product to the absorbed dose in uterus to enable predictive assessment of doses in the fetus in pregnant women. The study presents the average values of the received effective doses, absorbed doses in uterus and conversion coefficients for all considered models of devices. Conversion coefficients for protocols with automatic tube current modulation were lower compared to those for protocols without automatic tube current modulation, especially for pediatric patients: for children with an average age of 0 years – 9 times, for children an average age of 1 year – 6 times, for children an average age of 5 years – 5 times, for children an average age of 10 years – 3 times, for children an average age of 15 years – 2 times; for adults the difference was 20%. Comparison of the conversion coefficients from the dose-length product to the effective dose for computed tomographic scanning of the whole body area limited to the upper third of the femur, presented in guidelines 2.6.1.3584-19, with the values obtained in this study for the whole body area with the lower extremities without automatic tube current modulation showed that for all age groups, with the exception of newborns, the conversion coefficients for the scanning area with the lower extremities are lower than those presented in the guidelines. Using the conversion coefficients from the Guideline 2.6.1.3584-19 for whole-body computed tomography scanning with the lower extremities will lead to a significant overestimation of patient doses. The calculated conversion coefficients from the dose-length product to the absorbed dose in uterus and from the dose-length product to the effective dose for computed tomography examination of the whole body with the lower extremities for different age groups of patients are suitable for assessing the effective doses of patients and for prognostic estimates of absorbed dose in the fetus in pregnant women.

Computed tomography has become increasingly common for diagnosing socially significant diseases in recent years. In foreign practice, screening schemes for lung cancer in people belonging to risk categories have been developed and implemented. These schemes have been successfully used over the past 10 years. In this case, “low-dose” scanning protocols are used, which make it possible to perform examination with patient effective dose several times lower compared to standard protocols. Lung cancer screening methods using low-dose computed tomography are beginning to be introduced in the Russian Federation. To ensure the radiation safety of those individuals eligible for inclusion in screening programs or participating in biomedical research testing lung cancer screening, it is necessary to evaluate effective doses from low-dose computed tomography and compare these doses to established radiation dose limits. This study assessed the patients’ effective doses who underwent different types of low-dose computed tomography of chest at two medical organizations. The results of the study show that it is possible to achieve non-exceedance of the current annual effective dose limit of 1 mSv only for patients weighing less than 90 kg. For patients with higher body weight, the minimum effective dose will be in the range of 1.2 – 1.4 mSv. The results of the study indicate the need to make changes to the current regulatory and methodological documents of Rospotrebnadzor to ensure the possibility of using low-dose computed tomography as part of screening for all categories of people.

Diagnostic reference levels are one of the effective tools for optimizing patient radiation doses in diagnostic radiology. The staff of domestic radiology departments does not have an understanding of the development process and use of diagnostic reference levels during X-ray examinations, although this tool is a generally accepted in practice abroad. The article shows the experience of forming regional diagnostic reference levels based on measurements provided by the accredited testing laboratory of the Scientific and Practical Clinical Center for Diagnostics and Telemedicine Technologies of the Moscow Healthcare Department. The diagnostic reference levels for radiography in Moscow were developed for eight of the most common types of examinations based on the operation of 216 digital X-ray machines. The resulting levels, expressed in the dose-area product (cGy-cm2) and effective dose (mSv), were compared with the local diagnostic reference levels for the Ryazan region, Russia, and national diagnostic reference levels for other countries. The analysis showed continuity in the values. Some types of studies have been optimized. The developed diagnostic reference levels are the quality performance indicators foe diagnostic radiology departments and will be used to optimize a patient radiation dose during diagnostic studies in Moscow.

The study assessed the acceptability of the currently existing approach to calculating shielding in computed tomography rooms and formulated proposals for its improvement, taking into account the parameters of research in domestic medical practice. It is proposed to use the dose-length product as the main measured parameter in the new approach to calculating shielding. Typical tomograph workload values of dose-length product, typical for examinations in the Russian Federation, were assessed. Using thermoluminescent detectors, the experimental assessment of the distribution of absorbed dose in the air in a computed tomography room was carried out. The experimental results showed that the distribution of of X-ray exposure in the central plane is not isotropic. Due to the attenuation of exposure by the gantry design, “shadow” zones are observed, where the absorbed dose reduction in the air reaches 10-13 times compared to its level in the direction of couch movement. Based on the results of measurements of the distribution of absorbed dose in air, the relative scatter coefficients were calculated. The workload was determined for 7 tomographs (1 in St. Petersburg and 6 in Moscow). For each tomograph, the average weekly number of head and body examinations and the values of dose-length product for these areas were assessed, taking into account the number of multiphase examinations. The obtained workload values turned out to be one or two orders of magnitude higher than those currently used in calculating shielding. Based on the results of the study and literature data, the work proposes a new approach to calculating shielding in computed tomography rooms, based on the value of measured dose-length product during the examination and allowing to take into account the specifics of the operation of the device.

The article presents the analysis of the structure of computed tomography diagnostics according to the forms of the federal state statistical observation (radiation-hygienic passports in 2011–2021, forms № 3-DOZ in 2011-2021 and forms № 30 in 2014–2020) in order to assess the status of CT diagnostics in the Russian Federation and identify the main trends in the development of this type of radiation diagnostics and patient doses. In 2011–2021, there was a sharp development of CT diagnostics in the Russian Federation – an increase in the number of CT examinations per 1000 people (up to a factor of 5.9 – from 32 CT examinations per 1000 people to 189 CT examinations per 1000 people) and the contribution of CT in the collective dose from medical diagnostic exposure (3 times from 26% to 77%). The number of CT examinations per 1 CT device from 2014 to 2019 increased by 2 thousand (52%), and in 2020 by another 1.85 thousand (32% compared to 2019) and reached 7.7 thousand. The increase in the number of CT examinations was mainly due to the increased use of CT equipment. The main contribution to the structure and collective dose of computed tomography in 2021 is made by examinations of chest (58%/65%), abdomen (8%/14%), pelvis and hips (3%/4%), skull and maxillofacial area (18%/7%). In 2011-2021 for chest CT examinations, the average effective dose was in the range from 4.2 to 5.9 mSv per examination, for abdomen – from 6.5 to 9.2 mSv, for pelvis and hips – 5 to 6.7 mSv, for skull and maxillofacial area – 1.5 to 2.4 mSv. The COVID-19 pandemic in 2020-2021 caused a change in the structure of CT examinations and collective dose in the Russian Federation – the chest CT examinations occupied the first place of the contribution to the number of examinations and the collective dose. The number of CT examinations per 1000 people and the contribution of CT to the collective dose from medical diagnostic exposure in the Russian Federation were significantly lower than those in foreign countries (up to a factor of 3.5 in the number of CT examinations per 1000 people and up to a factor of 1.6 of the contribution of CT to the collective dose).

Analysis of levels of exposure of public of the Russian Federation by sources of ionizing exposure is one of main parts of the activities conducted by the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing. Data on the doses of public of the Russian Federation from medical exposure on facility, regional and federal levels is collected using the form of federal governmental statistical surveillance № 3-DOZ “Data on patient doses from medical X-ray examinations”, that is active since 2000. For the last 20 years there were no significant updates of the form № 3-DOZ. According to the decision of the Board of the Rospotrebnadzor from 11.09.2020, a complex program on update and modernization of form № 3-DOZ was initiated, that has resulted in the approvement of new form № 3-DOZ by the order of Rosstat № 880. The form has been significantly changed to reflect the modern condition of X-ray diagnostics in the Russian Federation. The aim of the current study was to analyze main components of medical exposure dose data collection system that required update and modernization. The study was performed based on the results of assessment of the forms № 3-DOZ from different medical facilities and regions in 2015-2020. The results of the study allowed developing main approaches to the update of the form № 3-DOZ that were implemented in a new edition of the form.

Computed tomography has become the main method of early diagnostics of COVID-19 during the pandemic of the novel coronavirus infection. Based on results of computed tomography of the chest it is possible to diagnose viral pneumonia associated with COVIS-19, to quickly assess the lung damage volume and severity of changes, to perform quick routing of patients and to start antiviral treatment. Hence, 2020 was associated with a rapid increase in the number of computed tomography examinations with corresponding changes in the structure of X-ray diagnostics. The aim of the current study was to evaluate the impact of the pandemic of the novel coronavirus infection on the structure of X-ray diagnostics and collective doses from medical exposure in the Russian Federation in 2019-2020. The study was based on the results of analysis of the federal state statistical surveillance forms №3-DOZ and №30 as well as on the data on Covid-19 morbidity in the regions of the Russian Federation. The results of the study indicate that there were no significant changes in the structure of X-ray diagnostics in 2020 compared to 2019 except for the increase in the number of computed tomography examinations. Their contribution to the total number of X-ray examinations has increased to 8,2% in 2020 compared to 4,6% in 2019. Contribution of other imaging modalities to the total number of X-ray examinations has not changed significantly. In 2020 the number of X-ray examinations decreased by 20% in average, varying from 6% for diagnostic nuclear medicine to 42% for interventional examinations. At the same time, the number of computed tomography examinations has rapidly increased by 60%. The structure of collective dose from medical exposure has significantly changed in 2020. Contribution of computed tomography to the collective dose in 2020 accounted for to 74% compared to 57% in 2019. Contribution of other imaging modalities has decreased by the factor of 1,5-2. Contribution of radiography examinations has decreased to 10,5% compared to 19% in 2019. Collective doses have correspondingly decreased by 20-30% for all imaging modalities except for computed tomography. Collective dose from computed tomography has increased by 71% compared to 2019. The number of all X-ray examinations in the Russian Federation has decreased by 12%: from 294 million in 2019 to 258 million in 2020. Collective dose from medical exposure has rapidly increased in 2020 by 30% to 115 thousand man. -Sv compared to 88 thousand man. -Sv in 2019. In average, in regions of the Russian Federation in 2020 each second computed tomography examination has been performed as a part of COVID-19 diagnostics with 2,3 computed tomography examinations per person infected with COVID.

The aim of the search was to compare the sources of information and evaluate dynamics of changes of the patients doses during x-ray and radionuclide examinations in medical organizations in Moscow from 2017 to 2020. Material and methods: Reporting forms № 3-DOZ, № 30 and Radiation-Hygienic Passport for 2017–2020 from Moscow organizations of different forms of ownership were collected and analyzed. The analysis was performed of the main indicators that determine the radiation safety in medical exposure: the number of medical organizations operating sources of ionizing radiation, the equipment of radiation diagnostics, the structure of radiation diagnostics and collective doses from medical exposure. Results: The analysis of trends of the development of radiation diagnostics in Moscow presented in the paper shows that the number of organizations operating ionizing radiation sources is increasing every year; the number of computed tomography scanners is growing by an average of 10% per year, and there is approximately the same increase in the number of computed tomography examinations. Therefore, in 2017-2019 the annual increase in the number of examinations was 10%; it was 30% in 2019–2020, which is associated with the epidemic of the new coronavirus infection COVID-19. The increase in the collective dose from medical exposure corresponds to the increase in the number of X-ray examinations. Comparison of the considered reporting forms and data from the unified X-ray information system shows that all reporting forms have their advantages and disadvantages, which are discussed in detail in the paper. For a comprehensive assessment of the condition of radiation diagnostics, it is necessary to compile data from different statistical reporting forms, which negatively affects the reliability and representativeness of the data. It should be noted that all the considered statistical reporting forms provide no data on individual and accumulated patients doses, as well as standard (typical) doses for the equipment of X-ray and radionuclide diagnostics. The existing procedure of data collection does not allow to receive and analyze the data online. Conclusion: Among the analyzed statistical reporting forms, there is no one that fully provides the tasks of the current assessment of the situation and operational management of public radiation doses. Some of the data in fact duplicate each other, and the existing discrepancies are more likely express difficulties in collecting and summarizing information than differences in reporting forms. Current statistical reporting forms require revision, consolidation, clarification and automation of data collection processes. Further implementation of electronic systems for recording and controlling patients doses, and generation monitoring and reporting systems, as well as interdepartmental interaction systems and the creation of an electronic office of organizations will reduce the rate of non-submission of reporting documentation. That makes it more objective and provides all the data necessary to optimize radiation protection of patients.

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.

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.

To ensure the quality assurance of CT-examinations, it is necessary to obtain the high-quality diagnostic information and maintain the optimal exposure levels of patients and medical staff. This paper is focused on the requirements and main aspects of quality assurance of CT-examinations, which include quality control of the equipment, methods of CT-image quality control, optimization of radiation protection, as well as management of the unintended and accidental medical exposure. The paper contains recommendations on quality control of diagnostic equipment, methods for monitoring the quality control of CT-images, values of diagnostic reference levels for the detection of abnormally high patient doses and optimization of the radiation protection of patients, as well as the recommendations for management of radiation and non-radiation accidents. All main sections of the paper represent an unified quality assurance system in computed tomography.