STATE INSTITUTION «NATIONAL RESEARCH CENTER FOR RADIATION MEDICINE OF THE NATIONAL ACADEMY OF MEDICAL SCIENCES OF UKRAINE¼ - RESEARCH ACTIVITIES AND SCIENTIFIC ADVANCE IN 2020. / REZUL'TATY ROBOTY DU «NATsIONAL'NYI NAUKOVYI TsENTR RADIATsIINOÏ MEDYTsYNY NATsIONAL'NOÏ AKADEMIÏ MEDYChNYKh NAUK UKRAÏNY¼ U 2020 ROTsI.

Research activities and scientific advance achieved in 2020 at the State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine¼ (NRCRM) concerning medical problems of the Chornobyl disaster, radiation medicine, radiobiology, radiation hygiene and epidemiology in collaboration with the WHO network of medical preparedness and assistance in radiation accidents are outlined in the annual report. The report presents the results of fundamental and applied research works of the study of radiation effects and health effects of the Chornobyl accident. The report also shows the results of scientific-organizational and health care work, staff training. The Scientific Council meeting of NAMS approved the NRCRM Annual Report.

A computational tool for patient specific dosimetry and radiobiological modeling of selective internal radiation therapy with (90)Y microspheres.

In recent years we have witnessed tremendous progress in selective internal radiation therapy. In clinical practice, quite often, radionuclide therapy is planned using simple models based on standard activity values or activity administered per unit body weight or surface area in spite of the admission that radiation-dose methods provide more accurate dosimetric results. To address that issue, the authors developed a Matlab-based computational software, named Patient Specific Yttrium-90 Dosimetry Toolkit (PSYDT). PSYDT was designed for patient specific voxel-based dosimetric calculations and radiobiological modeling of selective internal radiation therapy with (90)Y microspheres. The developed toolkit is composed of three dimensional dose calculations for both bremsstrahlung and beta emissions. Subsequently, radiobiological modeling is performed on a per-voxel basis and cumulative dose volume histograms (DVHs) are generated. In this report we describe the functionality and visualization features of PSYDT.

The effect of radiation quality on the risks of second malignancies.

UNLABELLED: Abstract Purpose: Numerous studies have implicated elevated second cancer risks as a result of radiation therapy. Our aim in this paper was to contribute to an understanding of the effects of radiation quality on second cancer risks. In particular, we developed a biologically motivated model to study the effects of linear energy transfer (LET) of charged particles (including protons, alpha particles and heavy ions Carbon and Neon) on the risk of second cancer. MATERIALS AND METHODS: A widely used approach to estimate the risk uses the so-called initiation-inactivation-repopulation model. Based on the available experimental data for the LET dependence of radiobiological parameters and mutation rate, we generalized this formulation to include the effects of radiation quality. We evaluated the secondary cancer risks for protons in the clinical range of LET, i.e., around 4-10 (KeV/µm), which lies in the plateau region of the Bragg peak. RESULTS: For protons, at a fixed radiation dose, we showed that the increase in second cancer risks correlated directly with increasing values of LET to a certain point, and then decreased. Interestingly, we obtained a higher risk for proton LET of 10 KeV/µm compared to the lower LET of 4 KeV/µm in the low dose region. In the case of heavy ions, the risk was higher for Carbon ions than Neon ions (even though they have almost the same LET). We also compared protons and alpha particles with the same LET, and it was interesting to note that the second cancer risks were higher for protons compared to alpha particles in the low-dose region. CONCLUSION: Overall, this study demonstrated the importance of including LET dependence in the estimation of second cancer risk. Our theoretical risk predictions were noticeably high; however, the biological end points should be tested experimentally for multiple treatment fields and to improve theoretical predictions.

Online training on the safe use of fluoroscopy can result in a significant decrease in patient dose.

RATIONALE AND OBJECTIVES: Concerns over medical radiation exposure have received national press in recent years, and training in the appropriate use of radiation has become an essential component of every radiology residency program. Appropriate training is particularly important in fluoroscopy because it is commonly used by inexperienced radiology residents and has the potential to impart relatively high patient radiation doses. In an effort to minimize the radiation doses received by patients, our institution has recently initiated an online training program in the safe use of fluoroscopy. This course is required and must be completed by new radiology residents before their first fluoroscopy rotation. The goal of this study was to determine if the use of an online course in the safe use of fluoroscopy could result in decreased patient dose without affecting diagnostic quality. MATERIALS AND METHODS: Four years of retrospective procedural data for residents performing gastrointestinal and genitourinary fluoroscopic procedures without specialized training were reviewed. Incoming residents took an American Medical Association-accredited online training program in the safe use of fluoroscopy the week before their first fluoroscopy rotation. Patient dose and diagnostic quality data, inferred from the frequency of attending physician intervention necessary to complete the procedure, were collected for all exams performed by the new group of residents after completion of the training course. This was then compared to data from prior classes and stratified by procedure type. RESULTS: Statistically significant reductions in both average fluoroscopy time (FT) or dose-area-product (DAP) were found for many of the fluoroscopic procedures performed by residents who participated in the online fluoroscopy training program. Specifically, statistically significant reductions in FT for barium enema, cystogram, defecogram, and esophagram procedures (P < .001) were found. Esophagram and upper gastrointestinal studies were completed with a significantly lower DAP (P < .001). The average reduction in DAP across all procedures performed by first-year residents was 38%, whereas the average reduction in FT was 25%. Based on a review of data from all procedures performed, there was no statistically significant loss in diagnostic quality. CONCLUSION: An online training program can be effectively used to provide radiation safety instruction immediately before the start of a resident's fluoroscopy rotation, decreasing patient dose without affecting diagnostic quality.

Workshop report on atomic bomb dosimetry-residual radiation exposure: recent research and suggestions for future studies.

There is a need for accurate dosimetry for studies of health effects in the Japanese atomic bomb survivors because of the important role that these studies play in worldwide radiation protection standards. International experts have developed dosimetry systems, such as the Dosimetry System 2002 (DS02), which assess the initial radiation exposure to gamma rays and neutrons but only briefly consider the possibility of some minimal contribution to the total body dose by residual radiation exposure. In recognition of the need for an up-to-date review of the topic of residual radiation exposure in Hiroshima and Nagasaki, recently reported studies were reviewed at a technical session at the 57th Annual Meeting of the Health Physics Society in Sacramento, California, 22-26 July 2012. A one-day workshop was also held to provide time for detailed discussion of these newer studies and to evaluate their potential use in clarifying the residual radiation exposures to the atomic-bomb survivors at Hiroshima and Nagasaki. Suggestions for possible future studies are also included in this workshop report.

ENLIGHT: The European Network for Light Ion Hadron Therapy.

The European Network for Light Ion Hadron Therapy (ENLIGHT) was established in 2002 to coordinate European efforts on hadron therapy (radiotherapy performed with protons and light ions instead of high-energy photons). The ENLIGHT network is formed by the European Hadron Therapy Community, with more than 300 participants from 20 different countries. A major success of ENLIGHT has been uniting traditionally separate communities so that clinicians, physicists, biologists, and engineers with experience and interest in particle therapy work together. ENLIGHT has been a successful initiative in forming a common European platform and bringing together people from diverse disciplines. ENLIGHT demonstrates the advantages of regular and organized exchanges of data, information, and best practices, as well as determining and following strategies for future needs in research and technological development in the hadron therapy field.

Highly cited German research contributions to the fields of radiation oncology, biology, and physics: focus on collaboration and diversity.

BACKGROUND AND PURPOSE: Tight budgets and increasing competition for research funding pose challenges for highly specialized medical disciplines such as radiation oncology. Therefore, a systematic review was performed of successfully completed research that had a high impact on clinical practice. These data might be helpful when preparing new projects. METHODS: Different measures of impact, visibility, and quality of published research are available, each with its own pros and cons. For this study, the article citation rate was chosen (minimum 15 citations per year on average). Highly cited German contributions to the fields of radiation oncology, biology, and physics (published between 1990 and 2010) were identified from the Scopus database. RESULTS: Between 1990 and 2010, 106 articles published in 44 scientific journals met the citation requirement. The median average of yearly citations was 21 (maximum 167, minimum 15). All articles with ≥ 40 citations per year were published between 2003 and 2009, consistent with the assumption that the citation rate gradually increases for up to 2 years after publication. Most citations per year were recorded for meta-analyses and randomized phase III trials, which typically were performed by collaborative groups. CONCLUSION: A large variety of clinical radiotherapy, biology, and physics topics achieved high numbers of citations. However, areas such as quality of life and side effects, palliative radiotherapy, and radiotherapy for nonmalignant disorders were underrepresented. Efforts to increase their visibility might be warranted.

The effect of stochastic fluctuation in radiation dose-rate on cell survival following fractionated radiation therapy.

In radiobiological models, it is often assumed that the radiation dose rate remains constant during the course of radiation delivery. However, instantaneous radiation dose rate undergoes random (stochastic) temporal fluctuation. The effect of stochastic dose rate in fractionated radiation therapy is unknown and there has been no analytical formulation of stochastic dose-rate fluctuation effect in fractionated radiation therapy which we endeavor to pursue here. We have obtained the quantitative expression of cellular survival fraction considering stochastic temporal fluctuation or noise in dose rate. We have shown that the constant dose-rate approximation overestimates the survival fraction compared to that under stochastic dose rate in a fractionated radiation therapy situation and this overestimation effect increases appreciably with the increase in the fluctuation level in dose rate. However, for a given level of fluctuation in dose rate, overestimation of survival fraction also depends on the value of cellular radiation sensitivity parameter ß and the repair rate of DNA lesion. This overestimation effect is higher for the cells which have a higher value of ß parameter or have a lower repair rate. Our study draws attention to stochastic temporal fluctuation in the radiation dose rate and its potential contribution to cell survival following fractionated radiotherapy.

From imaging to dosimetry and biological effects.

The essential steps are explained in calculating a radiation dose for radionuclide therapy from imaging data. As the dose alone is a meaningless value, its consequences in tumour cell kill efficiency and normal tissue damage are explained. The influence of dose rate and inhomogeneous dose distributions are discussed.

Dosimetry in nuclear medicine therapy: radiobiology application and results.

The linear quadratic model (LQM) has largely been used to assess the radiobiological damage to tissue by external beam fractionated radiotherapy and more recently has been extended to encompass a general continuous time varying dose rate protocol such as targeted radionuclide therapy (TRT). In this review, we provide the basic aspects of radiobiology, from a theoretical point of view, starting from the "four Rs" of radiobiology and introducing the biologically effective doses, which may be used to quantify the impact of a treatment on both tumors and normal tissues. We also present the main parameters required in the LQM, and illustrate the main models of tumor control probability and normal tissue complication probability and summarize the main dose-effect responses, reported in literature, which demonstrate the tentative link between targeted radiotherapy doses and those used in conventional radiotherapy. A better understanding of the radiobiology and mechanisms of action of TRT could contribute to describe the clinical data and guide the development of future compounds and the designing of prospective clinical trials.

Three endpoints of in vivo tumour radiobiology and their statistical estimation.

PURPOSE: To review the existing endpoints of tumour growth delay assays in experimental radiobiology with an emphasis on their efficient estimation for statistically significant identification of the treatment effect. To mathematically define doubling time (DT), tumour-growth delay (TGD) and cancer-cell surviving fraction (SF) in vivo using exponential growth and regrowth models with tumour volume measurements obtained from animal experiments. MATERIALS AND METHODS: A statistical model-based approach is used to define and efficiently estimate the three endpoints of tumour therapy in experimental cancer research. RESULTS: The log scale is advocated for plotting the tumour volume data and the respective analysis. Therefore, the geometric mean should be used to display the mean tumour volume data, and the group comparison should be a t-test for the log volume to comply with the Gaussian-distribution assumption. The relationship between cancer-cell SF, TGD and rate of growth is rigorously established. The widespread formula for cell kill is corrected; it has been rigorously shown that TGD is the difference between DTs. The software for the tumour growth delay analysis based on the mixed modeling approach with a complete set of instructions and example can be found on the author's webpage. CONCLUSIONS: The existing practice for TGD data analysis from animal experiments suffers from imprecision and large standard errors that yield low power and statistically insignificant treatment effect. This practice should be replaced with a model-based statistical analysis on the log scale.

A detailed radiobiological and dosimetric analysis of biochemical outcomes in a case-control study of permanent prostate brachytherapy patients.

The purpose of this study is to determine dosimetric and radiobiological predictors of biochemical control after recalculation of prostate implant dosimetry using updated AAPM Task Group 43 (TG-43) parameters and the radiobiological parameters recommended by TG-137. All biochemical failures among patients implanted with 125I Or 103Pd sources between 1994 and March 2006 were matched 2:1 with nonfailure controls. The individual matching was by risk group, radionuclide, prescribed dose, and time of implant (one match before and one after the failed patient) resulting in a median follow-up of 10.9 years. Complete dose volume histogram (DVH) data were recalculated for all 55 cases and 110 controls after updating the original source strength by the retrospectively determined ratios of TG-43. Differential DVH data were acquired in 179 increments of prostate volume versus percentage prescribed dose. At each incremental dose level i, the biologically equivalent dose BEDi, equivalent uniform dose EUDi, and tumor control probability TCPi were calculated from the implant dose plus any external beam delivered to the patient. Total BED, EUD, and TCP were then derived from the incremental values for comparison with single point dosimetric quality parameters and DVH-based averages. There was no significant difference between failures and controls in terms of total BED (143 vs 142 Gy), EUD (95 vs 94 Gy), or TCP (0.87 vs 0.89). Conditional logistic regression analysis factored out the matching variables and stratified the cohort into each case and its controls, but no radiobiological parameter was predictive of biochemical failure. However, there was a significant difference between radiobiological parameters of 125I and 103Pd due to less complete coverage of the target volume by the former isotope. The implant BED and TCP were highly correlated with the D90 and natural prescription doses and a series of mean DVH-based doses such as the harmonic mean and expressions of the generalized EUD. In this case-control study of prostate brachytherapy biochemical failures and nonfailures, there were no radiobiological parameters derived from detailed DVH-based analysis that predicted for biochemical control. This may indicate that in our approach, implant dosimetry is at or near the limits of clinically effective dose escalation.

Linear quadratic and tumour control probability modelling in external beam radiotherapy.

The standard linear-quadratic (LQ) survival model for external beam radiotherapy is reviewed with particular emphasis on studying how different schedules of radiation treatment planning may be affected by different tumour repopulation kinetics. The LQ model is further examined in the context of tumour control probability (TCP) models. The application of the Zaider and Minerbo non-Poissonian TCP model incorporating the effect of cellular repopulation is reviewed. In particular the recent development of a cell cycle model within the original Zaider and Minerbo TCP formalism is highlighted. Application of this TCP cell-cycle model in clinical treatment plans is explored and analysed.

Nondestructive inspection of low atomic number media using inelastic photon scattering.

The purpose of this study was to examine the potential of using scatter information to evaluate tissue density at selected sites. A method for non-invasively generating profiles of density distribution within an object using Compton scattered X-rays is presented. The Compton scatter method is modified to scan longitudinal sections of composite phantoms and samples of tissue substitute materials. Line scan data are used to describe how the detected count rate changes in response to localized density variations within an extended object. The physical limitations of quantification are discussed, including the effect of attenuation, multiple scatter, and limited spatial resolution. Further, the theory of the method, its performance and results of experimental phantom studies are described. The results presented indicate that the suggested method has the potential for measuring physical density distribution within an object with a spatial resolution of 2mm and an accuracy of approximately 4% under the circumstances in which attenuation correction is avoided.

Assessment of personal qualities in selection of medical radiation science students.

UNLABELLED: It is increasingly acknowledged that, in addition to prior academic achievement, there is a need to seek evidence for the abilities and personal qualities of applicants to health professional programs at a university. The aim of this study was to determine the specific abilities and personal qualities required for excellence in practice in the relevant professional domains of medical radiation science (MRS). METHODS: A focus group, consisting of MRS academic staff, developed a questionnaire. The questionnaire was sent to senior MRS practitioners throughout Australia and 213 were returned for analysis. Respondents were asked to rate 40 specific abilities and qualities (referred to as "elements") on a 5-point scale. RESULTS: Two hundred thirteen completed questionnaires were returned, a 53% response rate. One hundred twelve respondents (52%) indicated they currently worked in diagnostic radiography (DR), 57 (27%) worked in radiation therapy (RT), and 44 (21%) worked in nuclear medicine (NM). The duration (mean +/- SD) of the respondents' professional practice in MRS was 14.5 +/- 10 y, with durations ranging from 1 to 43 y. Raw scores and mean scores were examined for any influence of the variable "Number of Years in Practice." DISCUSSION: No major differences were found between the ratings provided by the practitioners from the 3 different MRS professional domains of NM, RT, and DR. Factor analysis indicated the existence of 3 orthogonal factors in the questionnaire data: (a) treat others professionally and ethically, (b) engage with and be open to others, and (c) problem-solving ability. Qualitative analysis of the respondents' comments provided similar themes: (a) the need for professional competence (knowledge and abilities), (b) ethical behavior, (c) the need for a technology and a people orientation, and (d) MRS should be the first choice of MRS students and not a second choice to other professional degrees. CONCLUSION: Senior medical radiation scientists identified professionalism, ethical behavior, engagement with and openness to others, intrinsic specific motivation, and an orientation to people and technology as nonacademic qualities required for excellence in the practice of the professions embraced by MRS.

The University of Michigan Student Health Physics Society's Radiation and Health Physics World Wide Web Site.

The University of Michigan Student Health Physics Society's (UMSHPS) Radiation and Health Physics World Wide Web Site is an informative database of radiation and health physics related topics. With over 1,000 visitors each day, the UMSHPS web site provides professionals and the general public with a valuable resource for information and research. Users of this site can either search for information by topic or submit questions directly to the qualified members the national Health Physics Society. During the past year, progress has been made in replacing the site's older, less versatile framework with new search engines and refined submittal forms, as well as a "Frequently Asked Questions" section. Within the database, references will include brief summaries of the site's available information and target audience. Although these changes have been beneficial for the site, the UMSHPS continuously seeks professional opinions and ideas to further the services that this online resource can provide to the profession and to the general public.

Radiation biodosimetry: applications for spaceflight.

The multiparametric dosimetry system that we are developing for medical radiological defense applications could be adapted for spaceflight environments. The system complements the internationally accepted personnel dosimeters and cytogenetic analysis of chromosome aberrations, considered the best means of documenting radiation doses for health records. Our system consists of a portable hematology analyzer, molecular biodosimetry using nucleic acid and antigen-based diagnostic equipment, and a dose assessment management software application. A dry-capillary tube reagent-based centrifuge blood cell counter (QBC Autoread Plus, Becton [correction of Beckon] Dickinson Bioscience) measures peripheral blood lymphocytes and monocytes, which could determine radiation dose based on the kinetics of blood cell depletion. Molecular biomarkers for ionizing radiation exposure (gene expression changes, blood proteins) can be measured in real time using such diagnostic detection technologies as miniaturized nucleic acid sequences and antigen-based biosensors, but they require validation of dose-dependent targets and development of optimized protocols and analysis systems. The Biodosimetry Assessment Tool, a software application, calculates radiation dose based on a patient's physical signs and symptoms and blood cell count analysis. It also annotates location of personnel dosimeters, displays a summary of a patient's dosimetric information to healthcare professionals, and archives the data for further use. These radiation assessment diagnostic technologies can have dual-use applications supporting general medical-related care.