Identification, prevention and response to events in medical exposure are an integral part of the radiation safety system in medicine. The existing approaches in the Russian Federation, presented in the current regulatory and methodological documents, need to be updated and harmonised with international practice. At the same time, it is advisable to focus on events related with patients, because of potential overexposure of workers and public is presented comprehensively. The study presents suggestions for amendments to terminology in medical exposure events of patients and development of classification of the events criteria as well. Schemes to identify and respond to events in medical exposure that related to overexposure of patients are defined. It is advisable to implement the results of the study into the section on radiation safety in medical exposure in the updated version of OSPORB-99/2010.

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.

Radiation events (accidents) appearance is an integral part of the use of ionizing radiation sources in medicine in general and nuclear medicine in particular. To minimize the negative impact on patients, workers, and public due to such events, it is necessary to have reliable information about real prevalence of the radiation events (accidents). The current work presents the analysis of the radiation accidents with medical ionizing radiation sources registered in the “Data bank of radiation accidents and incidents” of the Rospotrebnadzor Information and Analytical Centre for Radiation Safety and the results of workers questionnaires conducted in 25 nuclear medicine departments (about 30% of all nuclear medicine departments in the Russian Federation). The results of the analysis showed that the most common registered radiation accidents in the “Data bank of radiation accidents and incidents” are identification of passengers with high external dose rate as well as identification of waste contaminated by medical radionuclides. The results of the questionnaire showed that the most common radiation accidents (events) in nuclear medicine are contamination of work clothes or work surfaces with radionuclides, or patient fluids containing radionuclides; conducting examination without proper referral; extravasation of radiopharmaceutical. Existing systems of identification and registration of radiation accidents do not allow to identify radiation events (accidents) specific to nuclear medicine. The further research aimed at developing a classification of radiation events (accidents) in medicine and methods for responding to such events are feasible.

Background. Radiopharmaceutical therapy with 223 Ra dichloride (Xofigo (R)) is an effective method of treatment of bone metastases in patients with metastatic castration-resistant prostate cancer. Increased number of radiopharmaceutical therapy procedures with 223 Ra requires revision and update of the existing requirements to ensure radiation safety. Current problems in terms of radiation safety during radiopharmaceutical therapy are assessment of radiopharmaceutical excretion from a patient body and radionuclide activity in patient biological waste. Aim. To estimate the activity of 223 Ra excreted from a patient body at hospital (during the first hours after radiopharmaceutical administration) and activity concentration in the sewage water of the hospital during radiopharmaceutical therapy with 223 Ra dichloride (Xofigo (R)). Materials and methods. Eleven male patients with metastatic castration-resistant prostate cancer undergoing radiopharmaceutical therapy with 223 Ra dichloride were included in the study. Each micturition from patients in four hours had been sampled, and the samples were prepared to measure activity of 223 Ra in the urine. The urine sample residue was flushed down a dedicated patient toilet in the Department of Radionuclide Diagnosis and Therapy. Sewage water sampling was performed at three points (at three manholes) of the hospital. The 223 Ra activity in urine and sewage water samples was measured using a gamma semiconductor spectrometer. Results. All urine samples exceeded the threshold value of 223 Ra activity concentration and were considered liquid radioactive waste. The activity concentration of 223 Ra in the sewage water close to the Department of Radionuclide Diagnosis and Therapy building, and at the point where the sewage water from the building merged with the water from and the nearest building exceeded the threshold value. The activity concentration of 223 Ra decreased with increasing sewage water flow in the sewage system, and in the output from the entire hospital the activity concentration in the sewage water samples was below the threshold value. Conclusion. The results of this work show dilution of patient biological waste and reduction of 223 Ra activity concentration in the sewage system of a large hospital, which suggest that patient biological waste after radiopharmaceutical therapy with 223 Ra dichloride could be disposed directly into the sewage system and a differentiated approach to patient waste management after radiopharmaceutical therapy with 223 Ra dichloride could be applied.

Biological excretion from patients (urine) generated during radionuclide diagnostics enters directly into the hospital sewage system. The establishment of new clearance level according to Resolution of the Government of the Russian Federation No. 1069 of October 19, 2012 may entail amendments to regulatory documents for radionuclide diagnostics departments. One of these requirements is a mandatory dedicated sewage system. Establishment of the requirement may lead to an increase the cost of the radionuclide diagnostic examinations, and to a decrease the accessibility of radionuclide diagnostic. The aim of this study was to estimate the activity of radionuclides in patient urine after radionuclide diagnostic and activity concentration in sewage water in the hospital and in the transport tank of toilet for evaluation of paths of waste manage. Based on published literature data, models of biological excretion were constructed for the following radiopharmaceuticals: 99mTc-pyrophosphate, 64Cu-Labeled Monoclonal Antibody, 18F-FDG, 68Ga-PSMA-617. The activity of radionuclides in the patient waste in the hospital and in public transport during the patient transportation to home was calculated. Various scenarios of patient transportation were considered. The values of the excreted activity, activity concentration and dose rate at 1 m from the tank with sewage water for each type of transport were calculated. The calculated values of the radionuclide activity concentration in sewage water in transport tank of toilet for the majority scenarios exceed the clearance level (up to 180 times for 68Ga-PSMA-617 when traveling by bus). According the regulatory requirements, it is necessary to collect patient excretions after radionuclide diagnostic examinations and hold it for decay. However, estimated effective doses of individuals from the public from contact with biological patient waste do not exceed the acceptable value. This is due to the short half-life of diagnostic radionuclides. The paths of management system of biological patient waste were proposed.

Radiopharmaceutical therapy with 131I has been one of the most common types of radiopharmaceutical therapy for many years. Radiation safety of the public is ensured by limiting the patient contacts until the radiological parameters are reduced to the established criteria. To increase the availability of the radiopharmaceutical therapy with 131I, softer patient release criteria for 131I have been proposed. However, early patient release may increase exposure to the public, e.g. in transport. The aim of the work is to evaluate the radiation exposure from patients with 131I -MIBG and Na131I on the public in transport considering the generation of biological waste. In this work, 131I excretion from the body of patients in transport was evaluated for different scenarios of patient travel to the place of residence. As a result, it was found that mitigation of patient release criteria leads to an increase in the effective dose to the public in transport and an increase in the 131I activity excreted with patient waste. The specific activity in the tanks of biotoilets in transport, generated after the pas -sage of a patient with injected 131I -labeled radiopharmaceuticals, exceeds the limit value of classifying liquid waste as radioactive. To optimize radiation protection of the public, it is advisable to apply a differentiated approach to release patients after therapy with 131I: to group non-resident patients into a separate category retaining for them the established release criterion (without mitigation) to minimize the radiation impact on the public.

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

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.

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

Background. Radiopharmaceutical therapy with 223Ra dichloride (Xofigo®) is an effective method of treatment of bone metastases in patients with metastatic castration-resistant prostate cancer. Increased number of radiopharmaceutical therapy procedures with 223Ra requires revision and update of the existing requirements to ensure radiation safety. Current problems in terms of radiation safety during radiopharmaceutical therapy are assessment of radiopharmaceutical excretion from a patient body and radionuclide activity in patient biological waste.Aim. To estimate the activity of 223Ra excreted from a patient body at hospital (during the first hours after radiopharmaceutical administration) and activity concentration in the sewage water of the hospital during radiopharmaceutical therapy with 223Ra dichloride (Xofigo®).Materials and methods. Eleven male patients with metastatic castration-resistant prostate cancer undergoing radiopharmaceutical therapy with 223Ra dichloride were included in the study. Each micturition from patients in four hours had been sampled, and the samples were prepared to measure activity of 223Ra in the urine. The urine sample residue was flushed down a dedicated patient toilet in the Department of Radionuclide Diagnosis and Therapy. Sewage water sampling was performed at three points (at three manholes) of the hospital. The 223Ra activity in urine and sewage water samples was measured using a gamma semiconductor spectrometer.Results. All urine samples exceeded the threshold value of 223Ra activity concentration and were considered liquid radioactive waste. The activity concentration of 223Ra in the sewage water close to the Department of Radionuclide Diagnosis and Therapy building, and at the point where the sewage water from the building merged with the water from and the nearest building exceeded the threshold value. The activity concentration of 223Ra decreased with increasing sewage water flow in the sewage system, and in the output from the entire hospital the activity concentration in the sewage water samples was below the threshold value.Conclusion. The results of this work show dilution of patient biological waste and reduction of 223Ra activity concentration in the sewage system of a large hospital, which suggest that patient biological waste after radiopharmaceutical therapy with 223Ra dichloride could be disposed directly into the sewage system and a differentiated approach to patient waste management after radiopharmaceutical therapy with 223Ra dichloride could be applied.

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.

Purpose: To develop the method of experts’ quality evaluation of the PET images as an additional quality control method for accurate, comparable, and reproducible PET diagnostics results, and to conduct image quality evaluation in different PET departments used this method. Material and methods: 60 PET images (without CT) of the patients who underwent whole body PET/CT with 18F-FDG were collected from 12 PET/CT scanners in 9 PET departments. Experts’ quality evaluation was conducted with questioning of the experts. Each expert evaluated the image quality by five-point scale and filled out the special form which include three image quality criteria: image clarity, artefacts, and general image quality. There were 28 experts from 8 different PET departments who have work experience in radiology from 1 to 32 years. The results of experts’ quality evaluation of the PET images were examined for correlations with parameters of acquisition and reconstruction protocols, examination methods. The results were also examined for dependance of subjective factors such as work experience and work conditions of experts. The minimum required number of experts were defined. The results were analyzed used statistical methods. Results: The PET images obtained by 8 PET/CT scanners had mean quality value more than 4 points (good quality). PET/CT scanners, which had the lowest quality value, have the obsolete or unusual settings and reconstruction parameters. The correlations between experts’ quality evaluation of the PET images and acquisition parameters (acquisition time per bed, multiplication of injected activity and acquisition time per bed), and examination methods (injected activity and uptake time) were established. The results of experts’ quality evaluation of the PET images were dependent on work experience and work conditions of experts. Conclusion: The method of experts’ quality evaluation of the PET images of the patients based on the questioning of the experts working in PET was developed and demonstrated in the current study. The results showed this method has the potential to compare the PET images obtained by different acquisition and reconstruction protocols, and it can be applied during the optimization of examination method and for the determination of obsolete and unusual settings of PET/CT. Experts’ evaluation of the PET images should include the opinion of at least six experts with different work experience in PET from several PET departments.

The aim of this study was to evaluate the activity of 225 Ac in urine of patients undergoing radionuclide therapy with 225 Ac-DOTA-TATE. Activity concentration was determined in the urine samples collected within 72 hours after injection of 225 Ac-DOTA-TATE, using the ORTEC semiconductor gamma spectrometer, model TSP-DX-100T-PAC-PKG-1. Calculation of excreted activities was additionally performed based on scintig- raphy scans of patients receiving 225 Ac-DOTA-TATE. Scans were conducted 5 times for each patient: immedi- ately after injection, at 4 hours, and on the 1st, 2nd, and 3rd days after injection of the radiopharmaceutical. Absolute activity values and fractions of the injected activity were calculated based on the specific activity values. The results of the calculated activity concentration values demonstrate that maximum excretion was observed within the four hours after 225 Ac-DOTA-TATE injection. Significant differences between the two methods of determining 225 Ac activity were observed only on the third day after radiopharmaceutical injection, which allows for the simplification of future experimental work by using indirect radioactivity measurement methods for activity calculations. There were no significant differences between patient groups with different number of 225 Ac-DOTA-TATE injection, which allows for the exclusion of this parameter in the evaluation of experimental results. The results of this study represent the first published experimental data on the determi- nation of actinium excretion in patients.

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).

Existing drawbacks of the radionuclide therapy planning may lead to the excessive irradiation of the healthy organs and tissues that is associated with the development of deterministic and stochastic effects. In some cases absorbed dose in region of interest (lesion) can be lower than prescribed therapeutic dose. That reduces the effectiveness of radionuclide therapy and reduces survival rate of patients. These problems are associated with administration of the fixed activity of radionuclide in radiopharmaceutical, or administration of activity normalized per unit of body mass or body surface. That approach does not allow assessing absorbed doses in lesions or healthy tissues for individual patients. Report of International Commission on Radiation Units and Measurements 96 «Dosimetry-guided radiopharmaceutical therapy», published in 2021, presents modern approaches for the dosimetric planning of radionuclide therapy based on the individualized assessment of absorbed doses in organs and tissues. This study was aimed at the analysis of proposed in Report 96 methods of classification of irradiated regions, organs and tissues based on example of radionuclide therapy with 177 Lu-DOTATATE. Proposed terms and definitions are harmonized with previous reports of International Commission on Radiation Units and Measurements on external radiation therapy. Terms and definitions analyzed in the current study will be used in the following studies aimed at the development of the requirements on dosimetric planning of radionuclide therapy.

The development of nuclear medicine and, in particular, radionuclide diagnostics in the Russian Federation and the introduction of new technologies causes the necessity of the development and actualizing of the methods of the radionuclide diagnostics optimisation. Patient radiation protection optimisation through the equipment quality control and calibration is necessary to minimize the patient exposure levels and to obtain accurate and reproducible results of the uptake activity evaluation and high-quality image. However, in the national practice, conducting the equipment quality control and calibration is difficult due the lack of the requirements and methodology for quality control. The aim of the current study is the determination of the list of the necessary equipment quality control and calibration procedures in the radionuclide diagnostics department which will be harmonized between national and foreign standards and guidelines. The analysis of the national and the foreign documents standardized and recommended the gamma-camera and single photon emission computed tomography quality control and calibration procedures was performed in the study. The analysis demonstrated the national standards do not involve the frequency of the quality control for the most parameters. However, the methodology in the national standards is completely described, meets with foreign methodology and can be interchangeable, and can be used for quality control. Based on the analysis the list of the gamma camera and single photon emission computed tomography quality control and calibration procedures with recommended frequency, which is necessary for patient radiation protection optimisation and achievement of the accurate diagnostic results, are presented in the study.

INTRODUCTION: Peptide receptor therapy based on the 225 Ac radionuclide, due to the targeted effect on tumor cells, is the most promising method of treatment for patients with generalized forms of neuroendocrine tumors and castration-resistant prostate cancer. OBJECTIVE: The aim of the work was to evaluate the effectiveness of radioligand therapy of medicinal radiopharmaceuticals with 225 Ac. MATERIALS AND METHODS: Radioligand therapy based on 225 Ac radionuclide was performed in 7 patients with generalized prostate cancer and 3 patients with neuroendocrine tumors. RESULTS: Systemic radiation therapy with 225 Ac-PSMA 617 and 225 Ac-DOTATE showed its effectiveness in clinical practice — patients have a decrease in the level of accumulation of the radiopharmaceutical (RP) in pathological foci on PET-CT with 68 Ga-PSMA and 68 Ga-DOTATE; a decrease in the level of prostate-specific antigen (PSA) in the blood (for prostate cancer); reduction of manifestations of asthenic, pain and carcinoid (for neuroendocrine tumors) syndromes. Dosimetric studies make it possible to assess the biodistribution of a radiopharmaceutical drug in the body, accumulation in target organs and lesions. CONCLUSION: The appointment of this type of treatment requires an integrated approach based on a thorough study of medical records, assessment of the receptor status of the tumor tissue, timely detection and prediction of adverse reactions.