Biological Effects Of Radiation Research Articles

Clinical evaluation of the possibilities of modern conformal brachytherapy in the treatment of cancer of the female genital organs

The data on 137 patients with metastases of the cervical cancer to the vagina and on 132 patients with metastases of the uterus body cancer to the vagina after radiation treatment are analyerd. It is concluded that to estimate the biological effect of radiation on tissue it is more rational to use the time-dose- fractioning factor comparing with the cumulative radiation effect or linear and square law modehit is simpler, it is appleid in radiation oncology, it is as good as the latter models in predicting the probality of early and late radiation complications.

VERDICT MRI for radiation treatment response assessment in neuroendocrine tumors.

Noninvasive methods to study changes in tumor microstructure enable early assessment of treatment response and thus facilitate personalized treatment. The aim of this study was to evaluate the diffusion MRI model, Vascular, Extracellular and Restricted Diffusion for Cytometry in Tumors (VERDICT), for early response assessment to external radiation treatment and to compare the results with those of more studied sets of parameters derived from diffusion-weighted MRI data. Mice xenografted with human small intestine tumors were treated with external radiation treatment, and diffusion MRI experiments were performed on the day before and up to 2 weeks after treatment. The diffusion models VERDICT, ADC, IVIM, and DKI were fitted to MRI data, and the treatment response of each tumor was calculated based on pretreatment tumor growth and post-treatment tumor volume regression. Linear regression and correlation analysis were used to evaluate each model and their respective parameters for explaining the treatment response. VERDICT analysis showed significant changes from day -1 to day 3 for the intracellular and extracellular volume fraction, as well as the cell radius index (p<0.05; Wilcoxon signed-rank test). The strongest correlation between the diffusion model parameters and the tumor treatment response was seen for the ADC, kurtosis-corrected diffusion coefficient, and intracellular volume fraction on day 3 (τ =0.47, 0.52, and -0.49, respectively, p<0.05; Kendall rank correlation coefficient). Of all the tested models, VERDICT held the strongest explanatory value for the tumor treatment response on day 3 (R2 =0.75, p<0.01; linear regression). In conclusion, VERDICT has potential for early assessment of external radiation treatment and may provide further insights into the underlying biological effects of radiation on tumor tissue. In addition, the results suggest that the time window for assessment of treatment response using dMRI may be narrow.

The practice of radiation protection in an interventional neuroradiology service.

Interventional neuroradiology procedures subject professionals who work in this area to high doses of ionizing radiation, and such exposure leads to a higher chance of occupational diseases related to this physical risk. Radiation protection practices aim to reduce the occurrence of such damage to the health of these workers. To identify how the practice of radiation protection occurs in a multidisciplinary team of an interventional neuroradiology service in the state of Santa Catarina, Brazil. A qualitative, exploratory, and descriptive research conducted with nine health professionals from the multidisciplinary team. Non-participant observation and a survey form were used as data collection techniques. For data analysis, descriptive analysis based on absolute and relative frequency and content analysis were used. Although some practices showed the use of radiation protection measures in practice, such as workers taking turns to perform procedures and continuous use of the lead apron as well as the mobile suspended protection, we found that most of the practices violate the principles of radiation protection. Among these inadequate radiological protection practices, the following aspects were observed: not wearing lead goggles, not using collimation to obtain the image, poor knowledge of the principles of radiation protection and biological effects of ionizing radiation, and non-use of an individual dosimeter. There was a lack of know-how of the multidisciplinary team working in interventional neuroradiology regarding the practice of radiation protection.

Awareness of radiation protection among dental practitioners in UP and NCR region, India: A questionnaire-based study

Background: Biological effects of radiation include deterministic and stochastic effects. Dental colleges still follow radiation protection principles due to guidelines laid by the Dental Council of India and the Atomic Energy Regulatory Board, but private practitioners sometimes are negligent about the significance of radiation protection. The study focuses on the awareness of radiation protection among dental practitioners based on their knowledge, attitude, and application. Aim and Objectives: The aim and objectives of this study were to evaluate the level of awareness and attitude about radiation protection among dental practitioners in Uttar Pradesh and the NCR region, India. Materials and Methods: The survey was performed on dental practitioners from UP and NCR region, India. The survey comprised two sections: one section on basic information of the dentists and their working place, consisting of two questions. The second section consisted of 21 questions regarding patient and personnel protection methods and knowledge about radiation exposure. The questionnaire was disseminated through Google Forms. Results: Among 200 dentists, 84% use Radio visual graph (RVG) in their clinics. Ninety percent of the specialists attended the basic lecture on radiation exposure, nearly 50% of the dentists use digital receptors in pediatric patients, 86% of the specialists use their hands when adjusting the X-ray tube, 98.4% of the dentists know the related complications of radiation, 46.8% of the specialists explain the radiation measures to the patients, 76.2% of the dentists use lead barriers in their clinics, and 76.2% of the clinicians often get their X-ray machines serviced yearly. Conclusion: The current study shows the utmost need for further implementation of radiation protection. The majority of dentists are negligent in practicing radiation protection procedures properly. Emphasis on radiation safety and mandatory professional education is needed.

Comparison of early forecasts of the incidence of thyroid cancer in residents of the Russian Federation after the Chernobyl accident with observational data

A review of methods for assessing doses in the thyroid gland, predictions of the long-term consequences of its irradiation and the actual incidence of thyroid cancer in residents of four regions of the Russian Federation with the most significant radioactive fallout after the Chernobyl accident are presented. The method for assessing doses in the thyroid gland is based on the results of monitoring in May-June 1986 of radioiodine in the environment, food and in the body of residents. Thyroid doses in the population were used to justify medical and social protection measures, as well as epidemiological studies. In addition, the authorities needed forecasts of the possible morbidity of the population in order to organize adequate medical care. Most of the thyroid cancer cases were predicted among the adult population, which was not confirmed by observations 35 years after the accident. The prognosis of the incidence of thyroid cancer in preschool children differed in different studies due to the use of different coefficients of reducing the biological effectiveness of 131I radiation in the thyroid gland and long-term external and internal irradiation of the whole body with a low dose rate compared to the effect of acute exposure. The increase in the incidence of thyroid cancer among children began five years after the accident at the Chernobyl nuclear power plant. Examples of the dynamics of the incidence for children in the Bryansk region of the Russian Federation are given. The 2018 UNSCEAR Report showed that for 1986-2015, among children and adolescents under 18 years of age on the day of the accident in Belarus, Ukraine and four regions of Russia, more than 19 thousand thyroid cancer cases were detected, of which the share of radiation-induced diseases was estimated at 25%. For four regions of Russia, this amounts to 460 cases with a range of possible estimates from 130 to 900 cases. The highest morbidity was manifested among younger children exposed at the age of 0-4 years. In older children and adolescents, the proportion of radiation-induced diseases has significantly decreased 30 years after the accident. In general, early forecasts of radiation-induced thyroid cancer incidence in children in four regions of the Russian Federation with high levels of radioactive fallout are consistent with the data of subsequent 30-year epidemiological observations within an order of magnitude. With regard to thyroid cancer in adults, such a comparison is difficult, since no radiogenic increase in the incidence has been detected.

Studying the influence of 3.1 THz irradiation on the endocytosis of neuronal cells

Although more and more attention has been paid to the biological effects of electromagnetic radiation in the terahertz (THz) frequencies range with the rapid development of THz technology, the effects of THz irradiation on many biological processes remain unknown. In this study, we explored the influence of THz irradiation at the frequency of 3.1 THz on the endocytosis of neuronal cells. To determine the changes of endocytosis, a membrane-selective fluorescent dye FM4-64 was used to stain HT22 cells under two kinds of THz irradiation conditions including pre-irradiating cells followed by FM4-64 staining and simultaneously irradiating and FM4-64 dyeing cells. The results showed that 3.1 THz irradiation could alter the endocytosis of HT22 cells via enhancing this process when cells are in a resting state, and, to the contrary, inhibiting this process when cells were in an excited state. Finally, in the presence of dynasore, an inhibitor of GTPase dynamin, THz irradiation dramatically increased the FM4-64 fluorescence intensity comparing to the unirradiated group in both physiological states. These findings demonstrated that THz irradiation could alter the endocytic process of neuronal cells in either a positive or negative way, suggesting that it has the possibility of affecting the substance exchange and signal transmission.

Therapeutic Efficacy of Variable Biological Effectiveness of Proton Therapy in U-CH2 and MUG-Chor1 Human Chordoma Cell Death.

Simple SummaryChordoma is a rare, slow-growing cancer of the spinal cord. Photon radiation therapy and surgery are the standard of care for chordoma. Proton radiation therapy has become an increasingly common treatment in comparison to photon radiation therapy due to the ability to reduce off-target radiation dose. However, there is still an increased risk of toxicity to the surrounding critical structures that lead to poor treatment outcomes. Moreover, the biologic effectiveness of protons to sterilize chordoma cells remains uncertain and likely varies according to the proton energy spectrum throughout the proton field. We aim to investigate the tumoricidal properties of proton radiation therapy at the middle and end of the proton radiation field and elucidate variations in the relative biological effectiveness for chordoma cells. Our study helps quantify the therapeutic value of treating chordoma near the end of the proton field, where linear energy transfer is relatively high.Background: Chordoma is a cancer of spinal cord, skull base, and sacral area. Currently, the standard of care to treat chordoma is resection followed by radiation therapy. Since, chordoma is present in the spinal cord and these are very sensitive structures and often complete removal by surgery is not possible. As a result, chordoma has a high chance of recurrence and developing resistance to radiation therapy. In addition, treatment of chordoma by conventional radiation therapy can also damage normal tissues surrounding chordoma. Thus, current therapeutic options to treat chordoma are insufficient and novel therapies are desperately needed to treat locally advanced and metastatic chordoma. (2) Methods: In the present investigation, human chordoma cell lines of sacral origin MUG-Chor1 and U-CH2 were cultured and irradiated with Proton Beam Radiation using the clinical superconducting cyclotron and pencil-beam (active) scanning at Middle and End of the Spread-Out Bragg Peak (SOBP). Proton radiation was given at the following doses: Mug-Chor1 at 0, 1, 2, 4, and 8 Gy and U-CH2 at 0, 4, 8, 12, and 16 Gy. These doses were selected based on a pilot study in our lab and attempted to produce approximate survival fractions in the range of 1, 0.9, 0.5, 0.1, and 0.01, respectively, chosen for linear quadratic model fitting of the dose response. (3) Results: In this study, we investigated relative biological effectiveness (RBE) of proton radiation at the end of Spread Out Bragg Peak assuming that the reference radiation is a proton radiation in the middle of the SOBP. We observed differences in the survival of both Human chordoma cell lines, U-CH2 and MUG-Chor1. The data showed that there was a significantly higher cell death at the end of the Bragg peak as compared to middle of the Bragg peak. Based on the linear quadratic (LQ) fit for cell survival we calculated the RBE between M-SOBP and E-SOBP at 95% CI level and it was observed that RBE was higher than 1 at E-SOBP and caused significantly higher cell killing. Proton field at E-SOBP caused complex DNA damage in comparison to M-EOBP and the genes such as DNA topoisomerase 1, GTSE1, RAD51B were downregulated in E-SOBP treated cells. Thus, we conclude that there seems to be substantial variation in RBE (1.3–1.7) at the E-SOBP compared with the M-SOBP.

What Have We Learned about the Biological Effects of Radiation from the 35 Years of Analysis of the Consequences of the Chernobyl NPP Accident?

What Have We Learned about the Biological Effects of Radiation from the 35 Years of Analysis of the Consequences of the Chernobyl NPP Accident?

Quantitative modeling of carcinogenesis induced by single beams or mixtures of space radiations using targeted and non-targeted effects

Ionizing radiations encountered by astronauts on deep space missions produce biological damage by two main mechanisms: (1) Targeted effects (TE) due to direct traversals of cells by ionizing tracks. (2) Non-targeted effects (NTE) caused by release of signals from directly hit cells. The combination of these mechanisms generates non-linear dose response shapes, which need to be modeled quantitatively to predict health risks from space exploration. Here we used a TE + NTE model to analyze data on APC(1638N/+) mouse tumorigenesis induced by space-relevant doses of protons, 4He, 12C, 16O, 28Si or 56Fe ions, or γ rays. A customized weighted Negative Binomial distribution was used to describe the radiation type- and dose-dependent data variability. This approach allowed detailed quantification of dose–response shapes, NTE- and TE-related model parameters, and radiation quality metrics (relative biological effectiveness, RBE, and radiation effects ratio, RER, relative to γ rays) for each radiation type. Based on the modeled responses for each radiation type, we predicted the tumor yield for a Mars-mission-relevant mixture of these radiations, using the recently-developed incremental effect additivity (IEA) synergy theory. The proposed modeling approach can enhance current knowledge about quantification of space radiation quality effects, dose response shapes, and ultimately the health risks for astronauts.

Energy imparted and ionization yield in nanometre-sized volumes

In radiation physics, the biological effectiveness of radiation is generally estimated from the energy imparted to a sensitive volume of given size. However, measurements of this quantity are carried out almost exclusively with ionization-based techniques, by converting the ionization charge signal to energy imparted by means of a constant calibration factor, independent of particle type and energy. This procedure is reliable when the tissue-equivalent size of the sensitive volume is of the order of 1 μm and larger, since in this case the number of radiation-induced collisions is high and the distribution of energy transfer per single collision is masked by the multiple averaging. However, its reliability can be called into question when the size of the sensitive volume is decreased to the nanometre scale, as it is the case in experimental nanodosimetry. For this reason, the present study investigates the relationship between the two stochastic quantities energy imparted and ionization yield, calculated by Monte Carlo simulations in spherical sensitive volumes with diameter ranging from 100 nm down to 1 nm. The analysis was carried out for protons and carbon ions in the energy range from 1 to 100 MeV/u, crossing liquid-water sensitive spheres along their diameter. Simulations were done by means of the Geant4-DNA Monte Carlo code, with two different physics lists. A strong correlation between the energy imparted and the ionization yield was found, which comprises not only their mean values, but their entire stochastic distributions, even when the diameter of the sensitive volume is as small as 1 nm.

Basics of the Development of Microwave Intensification of Upstream on the Example of &lt;i&gt;Escherichia coli&lt;/i&gt;

Introduction. E. coli strains are the main microorganisms used for the production of a number of important biopharmaceutical products. There are no natural sources of microwave radiation on Earth, as it is absorbed by the upper atmosphere. No one doubts the importance of studying the biological effect of microwave radiation. The number of publications devoted to this problem is growing every year, and new ideas for the use of microwaves in drug production technology are emerging.Aim. Reveal the main effects of microwave irradiation and develop a technology for microwave intensification of E. coli culture growth.Materials and methods. This study presents the results of atomic force microscopy, refractometry, NMR relaxometry, turbidimetry, and lumimetry, demonstrating the possibility of microwave intensification of the cultivation process.Results and discussion. It was found that microwave irradiation leads to changes in the mobility of protons and the adsorption of water molecules on biopolymers and cells. These are the main links in the mechanism of "non-thermal" microwave action. A single microwave irradiation, depending on a number of parameters, can decrease or increase the growth of biomass. Studies of the bioluminescence of the E. coli strain with the lux-operon have shown that the optimal processing conditions do not negatively affect the luciferase production and metabolic activity of cells. Conclusion. The intensification procedure using microwave radiation can be considered a promising method and can provide new ideas for various applications in biotechnology.

The Effects of Ionising and Non-Ionising Electromagnetic Radiation on Extracellular Matrix Proteins.

Exposure to sub-lethal doses of ionising and non-ionising electromagnetic radiation can impact human health and well-being as a consequence of, for example, the side effects of radiotherapy (therapeutic X-ray exposure) and accelerated skin ageing (chronic exposure to ultraviolet radiation: UVR). Whilst attention has focused primarily on the interaction of electromagnetic radiation with cells and cellular components, radiation-induced damage to long-lived extracellular matrix (ECM) proteins has the potential to profoundly affect tissue structure, composition and function. This review focuses on the current understanding of the biological effects of ionising and non-ionising radiation on the ECM of breast stroma and skin dermis, respectively. Although there is some experimental evidence for radiation-induced damage to ECM proteins, compared with the well-characterised impact of radiation exposure on cell biology, the structural, functional, and ultimately clinical consequences of ECM irradiation remain poorly defined.

Radiation field and dose inhomogeneities using an X-ray cabinet in radiation biology research.

X-ray cabinets are replacing 137 Cs/60 Co sources in radiation biology research due to advantages in size, handling, and radiation protection. However, because of their different physical properties, X-ray cabinets are more susceptible to experimental influences than conventional sources. The aim of this study was to examine the variations related to the experimental setups typically used to investigate biological radiation effects with X-ray cabinets. A combined approach of physical dose measurements by thermoluminescence dosimetry and detection of biological effects by quantification of γH2AX and 53BP1 foci was used to analyze field inhomogeneity and evaluate the influence of the components of the experimental setup. Irradiation was performed using an X-ray tube (195kV, 10mA, 0.5-mm-thick copper filter, dose rate of 0.59Gy/min). Thermoluminescence dosimetry revealed inhomogeneity and a dose decrease of up to 42.3% within the beam area (diameter 31.1cm) compared to the dose at the center. This dose decrease was consistent with the observed decline in the number of radiation-induced foci by up to 55.9%. Uniform dose distribution was measured after reducing the size of the radiation field (diameter 12.5cm). However, when using 15-ml test tubes placed at different positions within this field, the dose decreased by up to 17% in comparison to the central position. Analysis of foci number revealed significant differences between the tubes for γH2AX (1 h) and 53BP1 (4 h) at different time points after irradiation. Neither removal of some tubes nor of the caps improved the dose decrease significantly. By contrast, when using 1.5-ml tubes, dose differences were less than 4%, and no significant differences in foci number were detected. X-ray cabinets are user-friendly irradiation units for investigating biological radiation effects. However, field inhomogeneities and experimental setup components considerably affect the delivered irradiation doses. For this reason, strict dosimetric monitoring of experimental irradiation setups is mandatory for reliable studies.

Combined DNA Damage Repair Interference and Ion Beam Therapy: Development, Benchmark, and Clinical Implications of a Mechanistic Biological Model

Our purpose was to develop a mechanistic model that describes and predicts radiation response after combined DNA damage repair interference (DDRi) and particle radiation therapy. The heterogeneous dose distributions of protons and 4He ions were implemented into the "UNIfied and VERSatile bio-response Engine" (UNIVERSE). Predictions for monoenergetic and mixed fields over clinically relevant dose and linear energy transfer range were compared with experimental in vitro survival data measured in this work as well as data available in the literature, including different cell lines and DDR interferences. Ultimately, UNIVERSE predictions were investigated in a patient plan. UNIVERSE accurately predicts survival of cell lines with and without DDRi in clinical settings of ion beam therapy based only on 3 parameters derived from photon data. With increasing dose or linear energy transfer, the radiosensitizing effect of DDRi decreases, resulting in diminished relative biological effect of ion beam radiation for cells subjected to DDRi in comparison to cells that are not. Similar trends were observed in patient plan recalculations; however, this analysis also suggests that DDRi+particle radiation therapy may better preserve the therapeutic window in comparison to DDRi+photon radiation therapy. The presented framework represents the first mechanistic model of combined DDRi and particle radiation therapy comprehensively benchmarked in clinically relevant scenarios and a step toward more personalized treatment. It reveals potential differences between DDRi+photon radiation therapy versus DDRi+particle radiation therapy, which have not been described so far. UNIVERSE could aid in appraising the clinical viability of combined administration of radiosensitizing drugs and charged particle therapy, as well as the identification of patients with known DDR deficiencies in the tumor who might benefit from therapy with light ions, freeing limited space at heavy ion therapy centers.

Track Structure Components: Characterizing Energy Deposited in Spherical Cells from Direct and Peripheral HZE Ion Hits.

To understand the biological effects of radiation, it is important to determine how ionizing radiation deposits energy in micrometric targets. The energy deposited in a target located in an irradiated tissue is a function of several factors such as the radiation type and the irradiated volume size. We simulated the energy deposited by energetic ions in spherical targets of 1, 2, 4, and 8 µm radii encompassed in irradiated parallelepiped volumes of various sizes using the stochastic radiation track structure code Relativistic Ion Tracks (RITRACKS). Because cells are usually part of a tissue when they are irradiated, electrons originating from radiation tracks in neighboring volumes also contribute to energy deposition in the target. To account for this contribution, we used periodic boundary conditions in the simulations. We found that the single-ion spectra of energy deposition in targets comprises two components: the direct ion hits to the targets, which is identical in all irradiation conditions, and the contribution of hits from electrons from neighboring volumes, which depends on the irradiated volume. We also calculated an analytical expression of the indirect hit contributions using the local effect model, which showed results similar to those obtained with RITRACKS.

Dr. Edith H. Quimby: A pioneering medical physicist and educator with outstanding contributions in radiation dosimetry

Dr. Edith H. Quimby: A pioneering medical physicist and educator with outstanding contributions in radiation dosimetry

Hygienic assessment of the impact of 5G/IMT-2020 communication networks on public health (literature review)

The program “Digital Economy of the Russian Federation” approved the Concept for the creation and development of 5G / IMT-2020 networks. The development of 5G communications will significantly impact the implementation of many innovative projects and initiatives: the Smart City project, Unmanned Transport, etc. Along with significant technical advantages compared to previous generations of communication (2G, 3G, 4G), 5G technology has completely different emitting characteristics: more emitting elements, signal modulation, three-dimensional beam, the ability to control the beam, SHF (ultra-high) and EHF (extremely high) radio frequency ranges and centimetre and millimetre wavelengths of electromagnetic radiation. Therefore, it is becoming an especially urgent problem to ensure exposure to the human body of non-ionizing electromagnetic fields of the radio frequency range (30 kHz-300 GHz). The authors searched the literature on the biological effects of 5G cellular communications and electromagnetic radiation in the centimetre and millimetre ranges using the appropriate keywords in PubMed search engines, Scopus, Web of Science, Medline, The Cochrane Library, EMBASE, Global Health, CyberLeninka, RSCI and others. There is currently tentative and conflicting evidence on the impact of 5G. The rapidly growing density of wireless devices and antennas (considering future 5G networks) increases the public health risk from exposure to RF EMFs as the penetration depth for 5G EHF radiation is only a few millimetres. At these wavelengths, resonance phenomena are possible at the cellular and molecular levels, particularly concerning stimulating SHF and EHF oxidative processes and damaging DNA. The influence of the millimetre range of RF-EMF is poorly understood; oncological and non-oncological (impact on the reproductive, immune systems, etc.) effects are possible. Using numerical simulation methods of EMF radiation resonances on insects, Thielens A et al., 2018, found a significant overall increase in the absorbed RF power at a frequency of 6 GHz and higher than a frequency below 6 GHz.

Computational simulator that calculates tumor control probability in a tumor heterogeneously irradiated for fractionated radiation oncology treatments

Although in the ionizing radiation field many concepts and processes are currently recognized as radiobiological, there are also probabilistic ones, and a probabilistic treatment makes a better understanding about them. The purpose of this study is to develop a new radiobiological simulator that calculates the tumor control probability (TCP) for a tumor heterogeneously irradiated from a fractioned treatment. The three possible types of cells and the results of interactions of ionizing radiation with each cell of a determined volume are analyzed. For an irradiated region with a dose per fraction d, the simulator determines the radiation biological effects using the cell kill ( K) and cell sub-lethal damage, volume, cell density, cell repair of damaged cells during the interfractions, and number of fractions. K is determined from its probabilistic complement, the cell survival ( S), described with the linear-quadratic (LQ) S(d) model as K = 1 − LQ S( d). TCP is calculated from computational simulations as in the ratio of simulations with K = 100% and their total. This application opens new avenues for theoretical and experimental investigations concerning simulations of radiation treatments, and methodologies for therapy optimizations. Our simulator represents a novel methodology as TCP is calculated without analytical formulas, but based on its own probabilistic definition.

Proton-Cluster-Beam Lethality and Mutagenicity in Bacillus subtilis Spores

The unique energy transfer characteristics of swift cluster ions have attracted the attention of many researchers working on the analysis or processing of material surfaces, but the effects on living organisms remain unclear. We irradiated B. subtilis spores with monomer and cluster proton beams and examined their lethality; the 2 MeV H2+ shows a clearly lower lethality than 340 keV H+, even though both have a comparable linear energy transfer. The 2 MeV H2+ dissociates into a pair of 1 MeV H+ by losing the bonding electrons at the target surface. The estimated internuclear distance and the radial dose distribution suggest that the spread of deposited total energy over two areas separated by just several nanometers greatly diminishes beam lethality and that the energy density in the very center of the trajectory, possibly within a 1 nm radius, has a great impact on lethality. We also performed a whole genome resequencing of the surviving colonies to compare the molecular nature of mutations but failed to find a clear difference in overall characteristics. Our results suggest that cluster beams may be a useful tool for understanding biological effects of high linear energy transfer radiation.

Comparison of 186Re to 662 keV photon radiation concerning biological radiation effect on the human B-cell line BV-173

Zellen der humanen Leukämie-Zelllinie BV-173 wurden mit 662keV-Photonenstrahlung respektive 186Re bestrahlt. In einem Inkubationszeitraum von 7 Tagen wurden Zahl und Vitalität der Zellen täglich bestimmt und als Dosiseffektkurven basierend auf der Vitalität dargestellt. Hierfür wurde der Zeitpunkt mit minimalem Überleben verwendet (72h 186Re und 24h Photonenstrahlung). Beide Strahlenarten zeigen am Auswertezeitpunkt (72h nach Versuchsbeginn für 186Re und 24h nach Versuchsbeginn für Photonenstrahlung) eine Überlebenskurve mit biexponentiellem Verlauf. Für Photonenstrahlung ist dies erklärbar durch eine Hypersensitivität im niedrigen Dosisbereich bis 1Gy, für die sich eine D0 von 3,3Gy ergibt, für Dosen über 1,0Gy liegt die D0 bei 10Gy. Für die 186Re-Inkubation ergibt sich eine D0 von 11,1Gy bei niedrigen Dosen verursacht durch die Reparatur subletaler Schäden, durch welche die biologische Wirkung abgeschwächt wird. Ab einer akkumulierten Dosis von etwa 1,6Gy zeichnet sich für 186Re ein wesentlich steilerer Kurvenverlauf mit einer D0 von 4,0Gy ab, der eine in diesem Bereich 2,5-fach stärkere biologische Wirkung als akute Photonenstrahlung wiedergibt (D0 4Gy für 186Re bzw. 10Gy für Photonen). Strahlung niedriger Dosisleistung zeigt eine geringere biologische Wirkung als eine akute Bestrahlung. Es existiert aber ein Grenzwert der akkumulierten Dosis, ab dem die biologische Wirkung von β-Strahlung die der Photonenstrahlung sogar übertrifft.