[Analysis of hearing aids application in elderly patients.]

The aim of the study is to evaluate the possibility to implement machine learning to create a digital auditory profile for elderly patients and to analyze the hearing aid fitting efficacy depending on involvement of the peripheral and central auditory pathways in a pathological process. Data analysis of 375 people aged 60-93 years is presented. 355 patients with chronic bilateral hearing loss (230 of them used hearing aids) were included in the main group, and 20 normal hearing elderly people were included in the control group. Audiological examination consisted of standard tests (pure tone audiometry, impedancemetry, speech audiometry in quiet) and tests to evaluate the central auditory processing (binaural fusion, dichotic digits, speech audiometry in noise, random gap detection). The Montreal Cognitive Assessment was used to detect cognitive impairment. The hearing aid fitting efficiency was evaluated with COSI questionnaire and speech audiometry in free field. Processing of the results was carried out using Pearson's correlation analysis aimed at creating a polynomial model of a patient's hearing on the basis of the limited test battery. There were close correlations between the state of cognitive functions and age, results of tests to evaluate the central auditory processing, as well as patients' satisfaction of hearing aid. The results of the work indicate the possibility of using computer technologies of data analysis to develop rehabilitation programs for elderly hearing impaired patients.

Fluorescence imaging of cells using long-range electromagnetic surface waves for excitation.

We present a depth-localized illumination technique for wide-field fluorescence microscopy, based on long-range optical surface waves. This technique allows one to excite the fluorescence only in a thin near-substrate layer of the specimen. Our experimental setup is compatible with both upright and inverted microscopes. It provides fluorescent microscopic images, which are superior to the epifluorescence ones in signal-to-noise ratio, contrast, and detail. We demonstrate the applicability of our technique for imaging both bacterial and eukaryotic cells (E. coli and HeLa, respectively).

The radiological environment at the Mayak PA site and radiation doses to individuals involved in emergency and remediation operations after the 'Kyshtym Accident' in 1957.

This article assesses the radiological environment at the nuclear site of the Mayak PA, Russian Federation, during and after the accident in 1957, the so-called 'Kyshtym Accident', and the radiation doses to those who participated in the eradication of its consequences. Based on numerous archival documents, this paper presents the radiation data for 1957-1960, including individual dosimetry monitoring data and estimated doses to the Mayak workers, as well as the to personnel in supporting organisations and the military involved in the remediation operations. From 1957-1959 some 38 500 individuals took part in the clean-up actions and remediation of contaminated areas of the Mayak PA industrial site after the accident, including individuals exposed at the time of the accident: Mayak PA employees, militarypersonnel, and civil construction workers. External equivalent doses to 10 500 individuals were estimated in the range of 220 to 265 mSv, while there were cases of doses up to 950 mSv and higher. The collective dose received during the accident and its aftermath was in the region of 7300 person-Sv. By October-December 1957, the collective dose was about 4500 person-Sv. Collective doses recorded in 1958 and 1959 amounted to 2250 person-Sv and 480 person-Sv, respectively.

Dynamics of body burdens and doses due to internal irradiation from intakes of long-lived radionuclides by residents of Ozyorsk situated near Mayak PA.

This paper presents and discusses new autopsy results and other historic data from earlier autopsies and environmental monitoring linked to releases from the Mayak PA facilities in the Chelyabinsk oblast in the southern Urals. The focus is on residents of the town of Ozyorsk located near to Mayak PA and the dynamics of body burdens and radiation doses from inhalation of plutonium alpha and americium-241, and ingestion of strontium-90 and caesium-137. It is demonstrated that accumulation and exposure from these radionuclides was mainly due to unplanned releases in the 1950s and 60s. The mean content of plutonium alpha at the time of autopsy of people commencing residence in Ozyorsk from 1949 to 1959 was about 3.5 Bq, falling to 0.2 Bq in those arriving after 1990. A reducing trend was also seen for (241)Am. The highest (90)Sr content in Ozyorsk residents was measured in 1967. The (137)Cs body content of residents arriving in Ozyorsk at any time was in almost all cases below the limit of detection. The committed effective dose from internal exposure to these long-lived radionuclides which would have been accumulated in Ozyorsk residents if present from 1949 to 2013 is estimated to be 13 mSv. This dose is primarily attributed to intakes during 1949 to 1959 when the annual effective dose rate was approximately 1 mSv y(-1). The current value is about 0.1 mSv y(-1). This dose is about 20 times higher than the dose from global man-made fallout, which is about 0.005 mSv y(-1) at present, but much lower than that from natural background radiation, i.e. about 2 mSv y(-1). The experience gained from this work and continuing activities can contribute to the development of improved international guidance in legacy situations, particularly as regards the provision and use of monitoring data to test and thereby build confidence in prognostic models for radiation conditions and potential future exposures. The scope includes evidence for the rate of reduction in radionuclide concentrations in environmental media and in their bioavailability, resuspension of long-lived alpha radionuclides, uptake of (90)Sr and (137)Cs in the food-chain, and confirmation of cumulative uptake via autopsy and whole body counting measurements. Continuing investigations will thus support decisions on future planned releases and contribute to planning of remediation of other areas affected by historic releases.

[Radiobiological Human Tissue repository: progress and perspectives for solving the problems of radiation safety and health protection of personnel and population].

Radiobiological Human Tissue repository was established in order to obtain and store biological material from Mayak PA workers occupationally exposed to ionizing (α- and/or γ-) radiation in a wide dose range, from the residents exposed to long term radiation due to radiation accidents and transfer of the samples to scientists for the purpose of studying the effects of radiation for people and their offspring. The accumulated biomaterial is the informational and research potential that form the basis for the work of the scientists in different spheres of biology and medicine. The repository comprises 5 sections: tumor and non-tumor tissues obtained in the course of autopsies, biopsies, surgeries, samples of blood and its components, of DNA, induced sputum, saliva, and other from people exposed or unexposed (control) to radiation. The biomaterial is stored in formalin, in paraffin blocks, slides, as well as in the freezers under low temperatures. All the information on the samples and the registrants (medical, dosimetry, demographic, and occupational data) was obtained and entered into the electronic database. A constantly updated website of the repository was developed in order to provide a possibility to get acquainted with the material and proceed with application for biosamples for scientists from Russia and abroad. Some data obtained in the course of scientific research works on the basis of the biomaterial from the Repository are briefly introduced in the review.

[The prevention of the acute urine retention and lower urinary tract infection after rectum surgery].

The possibilities of the prevention of the acute urine retention in patients with the prostatic enlargement after the rectum surgery. The method was successfully used in 106 patients.

Plutonium production and particles incorporation into the human body.

Plutonium is one of the most toxic radioactive substances known. The isotope 239Pu gained attention when it had become known as a potential explosive material for atomic bombs. This paper describes the main problems encountered during the early years of operation of the first plutonium production plant in the former Soviet Union, the Mayak Production Association (Mayak PA). Mayak PA caused severe radioactive contamination of the environment and exposure personnel and population living in the vicinity areas to high radiation doses. The authors focus on key findings of large-scale studies on the internal dosimetry of workers for use in assessment of radiological risks from exposure to plutonium. This work presents an overview of the important issues for inhalation dose assessments such as generation of plutonium particles, plutonium intake, dissolution of plutonium particles, distribution of plutonium in humans, related exposures and health effects. Understanding the relationship between health effects, radiation dose and route of exposure helps quantify the health risks associated with occupational exposure in the nuclear industry and validate the radiation protection standards used in the Russian Federation and worldwide.

Uncertainties in internal doses calculated for Mayak workers--a study of 63 cases.

This study makes use of 63 cases of Mayak workers exposed to Pu-239 with autopsy data and some late-time urine bioassay data. In addition, air-concentration data--used to construct monthly average values--are available for each case, which provide the time dependence and potential magnitudes of normal inhalation intakes for each case. The purpose of the study is to develop and test Bayesian methods of dose calculation for the Mayak workers. The first part of the study was to quantitatively characterise the uncertainties of the bioassay data. Then, starting with three different published biokinetic models, the data are fit by varying intake and model perturbation parameters, e.g., parameters influencing the lung, thoracic lymph nodes, liver and bone retention. Statistical self-consistency arguments are used to check the measurement uncertainty parameters within the Poisson-lognormal model. The second part of the study is to set up and test Bayesian dose calculations, which use the point determinations of biokinetic parameters from the study cases within a discrete, empirical Bayes approximation. The main conclusion of the study is that these methods are now ready to be applied to the entire Mayak worker population.

[Quantitative plutonium microdistribution in bone tissue of vertebra from occupationally exposed worker].

The purpose of this work is the receiving of quantitative data on Pu microdistribution in different structural elements of human bone tissue for local dose assessment and dosimetric models validation. Thoracic vertebra sample was taken for the study from former Mayak worker with rather high Pu burden, including information on occupational and exposure history, medical information and data on Pu content in organs. Lexan film autodiagrams were obtained using method of neutron-induced autoradiography from bone tissue sections. Quantitative analysis of randomly selected vision fields on one of autoradiograms was performed: fission fragment tracks Pu in different bone tissue areas were calculated, surface of bone tissue areas were defined. Quantitative information on Pu microdistribution in human bone tissue was obtained for the first time. On the basis of obtained data quantitative relation of Pu decays in bone volume to decays on bone surface in cortical and trabecular fractions were defined as 2.0 and 0.4, correspondingly. Actual quantitative relation of decays in bone volume to decays on bone surface is significantly different from recommended by ICRP for cortical fraction. Biokinetic model parameters of extrapulmonary ICRP compartment might need to be adjusted after expansion of data set on quantitative Pu microdistribution in other bone types in human that will involve new cases with different exposure pattern of radionuclide.

In vitro dissolution study of plutonium in aerosol particles from the Mayak PA: a tool for individualised dose estimates.

Chronic inhalation of Pu particles during Mayak processing is a potential concern for workers. Of the many particle properties that affect individualised dose estimates, particle solubility in lung fluids can be most important. This study compares in vitro dissolution rates of several plutonium industrial compounds present at different stages of the Mayak processing cycle using three different solvents. The results are then used to develop values of absorption parameters for individual dose assessments. In this study, the dissolution rates of nitrate, oxide and mixed plutonium aerosols were determined using a serum ultrafiltrate stimulant (SUF), phagolysosomal simulant fluid and Ringer's solution, all using a static system. According to the results obtained with SUF, Pu nitrate is absorbed into the blood to a larger extent than predicted using model parameters currently applied for Mayak workers. Absorption into the blood of 21.5 vs. 3% of deposited nuclide as current model predicts results in underestimation of systemic burden and overestimation of the lung dose. These data are being used to provide improved retrospective dose assessments for inhaled plutonium aerosols.

Comparison of dose estimation from occupational exposure to 239Pu using different modelling approaches.

Several approaches are available for bioassay interpretation when assigning Pu doses to Mayak workers. First, a conventional approach is to apply ICRP models per se. An alternative method involves individualised fitting of bioassay data using Bayesian statistical methods. A third approach is to develop an independent dosimetry system for Mayak workers by adapting ICRP models using a dataset of available bioassay measurements for this population. Thus, a dataset of 42 former Mayak workers, who died of non-radiation effects, with both urine bioassay and post-mortem tissue data was used to test these three approaches. All three approaches proved to be adequate for bioassay and tissue interpretation, and thus for Pu dose reconstruction purposes. However, large discrepancies are observed in the resulting quantitative dose estimates. These discrepancies can, in large part, be explained by differences in the interpretation of Pu behaviour in the lungs in the context of ICRP lung model. Thus, a careful validation of Pu lung dosimetry model is needed in Mayak worker dosimetry systems.

Adaptation of the ICRP publication 66 respiratory tract model to data on plutonium biokinetics for Mayak workers.

The biokinetics of inhaled plutonium were analyzed using compartment models representing their behavior within the respiratory tract, the gastrointestinal tract, and in systemic tissues. The processes of aerosol deposition, particle transport, absorption, and formation of a fixed deposit in the respiratory tract were formulated in the framework of the Human Respiratory Tract Model described in ICRP Publication 66. The values of parameters governing absorption and formation of the fixed deposit were established by fitting the model to the observations in 530 autopsy cases. The influence of smoking on mechanical clearance of deposited plutonium activity was considered. The dependence of absorption on the aerosol transportability, as estimated by in vitro methods (dialysis), was demonstrated. The results of this study were compared to those obtained from an earlier model of plutonium behavior in the respiratory tract, which was based on the same set of autopsy data. That model did not address the early phases of respiratory clearance and hence underestimated the committed lung dose by about 25% for plutonium oxides. Little difference in lung dose was found for nitrate forms.

Plutonium microdistribution in the lungs of Mayak workers.

The degree of nonuniform distribution of plutonium in the human lung has not been determined; thus current dosimetric models do not account for nonuniform irradiation. A better scientific basis is needed for assessing the risk of developing radiation-induced disease from inhaled alpha-particle-emitting radionuclides. We measured the distribution of plutonium activity in the lung by autoradiography and related the activity to specific compartments of the lung. The study materials were lung specimens from deceased workers employed by the Mayak Production Association. The approach to analyzing these lung samples used contemporary stereological sampling and analysis techniques together with quantitative alpha-particle autoradiography. For the first time, plutonium distribution has been quantified in the human lung. The distribution of long-term retained plutonium is nonuniform, and a significant portion of plutonium was retained in pulmonary scars. In addition, a large fraction of plutonium was present in the parenchyma, where it was retained much longer than was estimated previously. The sequestration of plutonium particles in scars would greatly reduce the radiation exposure of the critical target cells and tissues for lung cancer. Thus the prolonged retention of plutonium in lung scars may not increase the dose or risk for lung cancer.

Lung cancer risk due to exposure to incorporated plutonium.

An epidemiological study has been carried out among 1,479 male workers who started working at the "Mayak" Production Association in 1948-1958 and were exposed to external gamma radiation and plutonium aerosols. Lung cancer mortality for the follow-up period 1948-1993 has been analyzed. No statistically significant association of lung cancer mortality and external gamma-ray dose has been revealed in the range of accumulated doses of 0.2-5.5 Gy. Association of lung cancer mortality and the dose of alpha-particle radiation to the lung is statistically significant. In the dose range below 30 Sv, this association can be described in terms of a linear nonthreshold function. Lifetime lung cancer risk in the dose range below 30 Sv is 1.21 x 10(-2)Sv(-1).

Lung cancer in Mayak workers.

The cohort of nuclear workers at the Mayak Production Association, located in the Russian Federation, is a unique resource for providing information on the health effects of exposure to plutonium as well as the effects of protracted external dose. Lung cancer mortality risks were evaluated in 21,790 Mayak workers, a much larger group than included in previous evaluations of lung cancer risks in this cohort. These analyses, which included 655 lung cancer deaths occurring in the period 1955-2000, were the first to evaluate both excess relative risk (ERR) and excess absolute risk (EAR) models and to give detailed attention to the modifying effects of gender, attained age and age at hire. Lung cancer risks were found to be significantly related to both internal dose to the lung from plutonium and external dose, and risks were described adequately by linear functions. For internal dose, the ERR per gray for females was about four times higher than that for males, whereas the EAR for females was less than half that for males; the ERR showed a strong decline with attained age, whereas the EAR increased with attained age until about age 65 and then decreased. Parallel analyses of lung cancer mortality risks in Mayak workers and Japanese A-bomb survivors were also conducted. Efforts currently under way to improve both internal and external dose estimates, and to develop data on smoking, should result in more accurate risk estimates in the future.

Bone cancers in Mayak workers.

Bone cancer mortality risks were evaluated in 11,000 workers who started working at the "Mayak" Production Association in 1948-1958 and who were exposed to both internally deposited plutonium and external gamma radiation. Comparisons with Russian and U.S. general population rates indicate excess mortality, especially among females, plutonium plant workers, and workers with external doses exceeding 1 Sv. Comparisons within the Mayak worker cohort, which evaluate the role of plutonium body burden with adjustment for cumulative external dose, indicate excess mortality among workers with burdens estimated to exceed 7.4 kBq (relative risk = 7.9; 95% CI = 1.6-32) and among workers in the plutonium plant who did not have routine plutonium monitoring data based on urine measurements (relative risk = 4.1; 95% CI = 1.2-14). In addition, analyses treating the estimated plutonium body burden as a continuous variable indicate increasing risk with increasing burden (P < 0.001). Because of limitations in current plutonium dosimetry, no attempt was made to quantify bone cancer risks from plutonium in terms of organ dose, and risk from external dose could not be reliably evaluated.

Liver cancers in Mayak workers.

Liver cancer mortality risks were evaluated in 11,000 workers who started working at the "Mayak" Production Association in 1948-1958 and who were exposed to both internally deposited plutonium and external gamma radiation. Comparisons with Russian liver cancer incidence rates indicate excess risk, especially among those with detectable plutonium body burdens and among female workers in the plutonium plant. Comparisons within the Mayak worker cohort which evaluate the role of plutonium body burden with adjustment for cumulative external dose indicate excess risk among workers with burdens estimated to exceed 7.4 kBq (relative risk = 17; 95% CI = 8. 0-36) and among workers in the plutonium plant who did not have routine plutonium monitoring data based on urine measurements (relative risk = 2.8; 95% CI = 1.3-6.2). In addition, analyses treating the estimated plutonium body burden as a continuous variable indicate increasing risk with increasing burden (P < 0.001). Relative risks tended to be higher for females than for males, probably because of the lower baseline risk and the higher levels of plutonium measured in females. Because of limitations in current plutonium dosimetry, no attempt was made to quantify liver cancer risks from plutonium in terms of organ dose, and risk from external dose could not be reliably evaluated.

Cancer mortality risk among workers at the Mayak nuclear complex.

At present, direct data on risk from protracted or fractionated radiation exposure at low dose rates have been limited largely to studies of populations exposed to low cumulative doses with resulting low statistical power. We evaluated the cancer risks associated with protracted exposure to external whole-body gamma radiation at high cumulative doses (the average dose is 0.8 Gy and the highest doses exceed 10 Gy) in Russian nuclear workers. Cancer deaths in a cohort of about 21,500 nuclear workers who began working at the Mayak complex between 1948 and 1972 were ascertained from death certificates and autopsy reports with follow-up through December 1997. Excess relative risk models were used to estimate solid cancer and leukemia risks associated with external gamma-radiation dose with adjustment for effects of plutonium exposures. Both solid cancer and leukemia death rates increased significantly with increasing gamma-ray dose (P < 0.001). Under a linear dose-response model, the excess relative risk for lung, liver and skeletal cancers as a group (668 deaths) adjusted for plutonium exposure is 0.30 per gray (P < 0.001) and 0.08 per gray (P < 0.001) for all other solid cancers (1062 deaths). The solid cancer dose-response functions appear to be nonlinear, with the excess risk estimates at doses of less than 3 Gy being about twice those predicted by the linear model. Plutonium exposure was associated with increased risks both for lung, liver and skeletal cancers (the sites of primary plutonium deposition) and for other solid cancers as a group. A significant dose response, with no indication of plutonium exposure effects, was found for leukemia. Excess risks for leukemia exhibited a significant dependence on the time since the dose was received. For doses received within 3 to 5 years of death the excess relative risk per gray was estimated to be about 7 (P < 0.001), but this risk was only 0.45 (P = 0.02) for doses received 5 to 45 years prior to death. External gamma-ray exposures significantly increased risks of both solid cancers and leukemia in this large cohort of men and women with occupational radiation exposures. Risks at doses of less than 1 Gy may be slightly lower than those seen for doses arising from acute exposures in the atomic bomb survivors. As dose estimates for the Mayak workers are improved, it should be possible to obtain more precise estimates of solid cancer and leukemia risks from protracted external radiation exposure in this cohort.

Characteristics of the cohort of workers at the Mayak nuclear complex.

At Branch No. 1 of the Russian State Research Center "Biophysics Institute", a registry has been created of workers at the "Mayak" Production Association, the first nuclear complex in Russia. This registry includes 18,830 persons hired at Mayak's nuclear reactors and radiochemical and plutonium production plant between 1948 and 1972. Twenty-five percent of these workers are women. As of December 31, 1994, the vital status is known for approximately 90% of the cohort members. A total of 5,118 persons have died. The cause for 97% of total deaths has been ascertained. The cohort members were exposed to both external gamma radiation and internal radiation from incorporated plutonium. The plutonium body burden has been measured in 30% of the cohort members with potential for plutonium exposure. External gamma-ray doses were in the range from tenths of milligrays to about 10 Gy, and plutonium body burdens were up to about 260 kBq. In view of the nature of the Mayak worker cohort, it has the potential to provide reasonably precise, quantitative estimates of the long-term health effects associated with chronic low-dose-rate exposure to external gamma radiation as well as internal radiation from plutonium. However, a number of issues must be addressed before credible risk estimates can be obtained from this cohort. These issues include the development of an appropriate internal comparison group and/or external rates and separating of the effects of internal and external exposures on risk estimates.

Lung cancer in radiochemical industry workers.

The frequency of lung cancer was investigated among 2346 workers in the radiochemical plant 'Mayak' who were exposed to radiation, both externally and internally from incorporation of plutonium. The results from the follow-up were analysed in terms of a linear relative risk model, accounting for the protracted exposures. On the basis of the observed data, it is deduced that the life-span incidence of radiation-induced lung cancer is several times larger than the value 0.0085 Sv-1 that is recommended in ICRP Publication 60 for the risk to this organ.