Showing papers in "Radiation Protection Dosimetry in 2006"
TL;DR: The Chernobyl Forum Expert Group on Environmental Consequences of the Chernobyl Accident and their Remediation: Twenty Years of Experience RADIOLOGICAL ASSESSMENT R E P O R T S S S E R I R I E S Enironm etal C onsuences of he C heobyl A ccdent nd teir R em edtion: Tw enty Yars of Exrience 9.9 mm 180 pages as discussed by the authors
Abstract: VIENNA ISBN 92–0–114705–8 ISSN 1020–6566 The explosion on 26 April 1986 at the Chernobyl nuclear power plant and the consequent reactor fire resulted in an unprecedented release of radioactive material from a nuclear reactor and adverse consequences for the public and the environment. Although the accident occurred nearly two decades ago, controversy still surrounds the real impact of the disaster. Therefore the IAEA, in cooperation with the Food and Agriculture Organization of the United Nations, the United Nations Development Programme, the United Nations Environment Programme, the United Nations Office for the Coordination of Humanitarian Affairs, the United Nations Scientific Committee on the Effects of Atomic Radiation, the World Health Organization and the World Bank, as well as the competent authorities of Belarus, the Russian Federation and Ukraine, established the Chernobyl Forum in 2003. The mission of the Forum was to generate “authoritative consensual statements” on the environmental consequences and health effects attributable to radiation exposure arising from the accident as well as to provide advice on environmental remediation and special health care programmes, and to suggest areas in which further research is required. This report presents the findings and recommendations of the Chernobyl Forum concerning the environmental effects of the Chernobyl accident. Report of the Chernobyl Forum Expert Group ‘Environment’ Environmental Consequences of the Chernobyl Accident and their Remediation: Twenty Years of Experience RADIOLOGICAL ASSESSMENT R E P O R T S S E R I E S Enironm etal C onsuences of he C heobyl A ccdent nd teir R em edtion: Tw enty Yars of Exrience 9.9 mm 180 pages
238 citations
TL;DR: PresAGE as mentioned in this paper is an optically clear polyurethane-based radiochromic 3D dosemeter for ionising radiation that is formulated with a free radical initiator and a leuco dye.
Abstract: For the past 50 years there has been interest in developing 3-D dosemeters for ionising radiation. Particular emphasis has been put on those dosemeters that change their optical properties in proportion to the absorbed dose. Many of the dosemeters that have been evaluated have had limitations such as lack of transparency, diffusion of the image of the dose distribution or poor stability of baseline optical density. Many of these performance limitations have been overcome by the development of PRESAGE™, an optically clear polyurethane-based radiochromic 3-D dosemeter. The solid PRESAGE™ dosemeter is formulated with a free radical initiator and a leuco dye and it does not require a container to maintain its shape. The polyurethane matrix is tissue equivalent and prevents the diffusion of the dose distribution image. There is a linear dose-response, which is independent of both photon energy and dose rate. Simple precautions such as preventing long-term exposure to additional ionising radiation including ultraviolet and controlling storage temperatures prevent the bleaching of the radiochromic response field within the irradiated dosemeter.
194 citations
TL;DR: Historical threads are traced through the successive symposia, culminating in current emphasis on the predominant importance of clustered damage in DNA, first revealed by track-structure simulations, but tempered by recognition also of the contribution that novel 'non-targeted' effects may play in the overall biological consequences of radiation.
Abstract: The broad field of microdosimetry, as reflected in the proceedings of the 13 previous symposia in this series, has been largely concerned with the microscopic stochastics of energy deposition from ionising radiations of different qualities, the ways in which these can be described and the information that they can provide towards mechanistic understanding of the biological effects of radiation and for practical applications Directions of the research have been strongly influenced by technical developments at particular times, most notably the tissue-equivalent proportional counter and later Monte Carlo track-structure simulation methods Essential to the research have been evolving notions as to characteristics of the relevant biological targets, and in particular their sizes and structures in relation to the microscopic features of the radiation Over the decades since the first Symposium on Microdosimetry, in 1967, emphasis has fluctuated from key targets being assumed to be of nanometre dimensions, then up to one micrometer, ten micrometers, and then back again to a few nanometres Some of these historical threads are traced through the successive symposia, culminating in current emphasis on the predominant importance of clustered damage in DNA, first revealed by track-structure simulations, but tempered by recognition also of the contribution that novel 'non-targeted' effects may play in the overall biological consequences of radiation
171 citations
TL;DR: The focus lies in the mechanisms responding to direct or indirectly induced DSBs, which are the major lethal lesion induced by IR.
Abstract: The amazing feature of ionising radiation (IR) as a DNA damaging agent is the range of lesions it induces Such lesions include base damage, single strand breaks (SSBs), double strand breaks (DSBs) of varying complexity and DNA cross links A range of DNA damage response mechanisms operate to help maintain genomic stability in the face of such damage Such mechanisms include pathways of DNA repair and signal transduction mechanisms Increasing evidence suggests that these pathways operate co-operatively In addition, the relative impact of one mechanism over another most probably depends upon the cell cycle phase and tissue type Here, the distinct damage response pathways are reviewed and the current understanding of the interplay between them is considered Since DNA DSBs are the major lethal lesion induced by IR, the focus lies in the mechanisms responding to direct or indirectly induced DSBs
135 citations
TL;DR: In the soils in general, the concentration of (232)Th was found to be higher than that of the (238)U and the activities of ( 232)Th and ( 238)U in this area are higher than the world average, and the annual effective dose to the public was finding to be 269 muSv.
Abstract: The concentrations and distribution of natural and anthropogenic radionuclides in soils from around the Kestanbol (Canakkale), Turkey were investigated with an aim of evaluating the environmental radioactivity and radiological health hazard. Concentrations of radionuclides in the samples were determined by gamma ray spectrometer using HPGe detector. In the soils in general, the concentration of (232)Th was found to be higher than that of the (238)U and the activities of (232)Th and (238)U in this area are higher than the world average. (137)Cs was observed in all the samples, ranging from 0.37 +/- 0.22 to 36.03 +/- 0.54 Bq kg(-1). The mean radium equivalent activity, external hazard index and terrestrial absorbed dose rate for the area under study are 498 Bq kg(-1), 1.4 and 219 nGy h(-1), respectively. The annual effective dose to the public was found to be 269 muSv. The present data were compared with data obtained from different countries.
110 citations
TL;DR: The aim of this paper is to describe the capabilities of IMBA Professional Plus, and the mathematical methods used.
Abstract: IMBA (Integrated Modules for Bioassay Analysis) is a suite of software modules that implement the current ICRP biokinetic and dosimetric models for estimation of intakes and doses. The IMBA modules have gone through extensive quality assurance, and are now used for routine formal dose assessment by Approved Dosimetry Services throughout the UK. HPA has continued to develop the IMBA modules. In addition, several projects, sponsored by organisations both in the USA and in Canada, have resulted in the development of customised user-friendly interfaces (IMBA Expert™ ‘editions’). These enable users not only to use the standard ICRP models, but also to change many of the parameter values from ICRP defaults, and to apply sophisticated data handling techniques to internal dose calculations. These include: fitting measurement data with the maximum likelihood method; using multiple chronic and acute intakes; and dealing with different data types, such as urine, faces and whole body simultaneously. These interfaces were improved further as a result of user-feedback, and a general ‘off-the-shelf’ product, IMBA Professional, was developed and made available in January 2004. A new version, IMBA Professional Plus, was released in April 2005, which is both faster and more powerful than previous software. The aim of this paper is to describe the capabilities of IMBA Professional Plus, and the mathematical methods used.
106 citations
TL;DR: The short luminescent lifetime and nondestructive readout is favorable for imaging applications, and the main optical properties of this material are due to the formation of aggregate defects composed of two oxygen vacancies and two Mg-impurity atoms.
Abstract: Optical and dosimetric properties of a new radiophotoluminescent material based on aluminum oxide doped with carbon and magnesium (Al2O3:C,Mg) and having aggregate oxygen vacancy defects are presented. The Al2O3:C,Mg crystals are characterized by several new optical absorption and emission bands. It is suggested that the main optical properties of this material are due to the formation of aggregate defects composed of two oxygen vacancies and two Mg-impurity atoms. Radiation-induced optical absorption bands are centered at 335 and 620 nm and produce fluorescent emission at 750 nm with a 75 +/- 5 ns lifetime. The dose measurements are performed by illumination of the Al2O3:C,Mg crystal with 335 nm or 650 nm light and by measuring the intensity of the 750 nm fluorescence. The detector material is insensitive to room light before and after the irradiation and the traps are stable up to 600 degrees C. A dose measurement range between 5 mGy and 200 Gy, suitable for therapeutic radiology applications, was demonstrated. The short luminescent lifetime and nondestructive readout is favorable for imaging applications.
88 citations
TL;DR: Fading, photon energy dependence and reproducibility of OSL-signal correspond well with requirements to clinical and personal dosemeters and a simple optically stimulated luminescence (OSL) treatment has been developed.
Abstract: The optical sensitivity of BeO-based luminophors has been well-known for many years. The optical stimulation of BeO with blue light is most effective. Then the dosemeters emit luminescent light in the ultraviolet-range around 325 nm. Matched on these facts a simple optically stimulated luminescence (OSL) treatment has been developed. Intense blue light-emitting diodes are used for cw-stimulation. A Hamamatsu solar blind photomultiplier detects the OSL-light. Good separation of both spectral ranges by optical filters is very important. The dosemeter has a linear dose response between approximately 20 muGy and >10 Gy. It was suggested, that a modification of stimulation conditions would allow measurements down to 1 muGy. Fading, photon energy dependence and reproducibility of OSL-signal correspond well with requirements to clinical and personal dosemeters. In addition, basic questions of the OSL-process in BeO have been investigated. A relevant point of interest was the dependency of the OSL-signal on stimulation power.
87 citations
TL;DR: The fragmentation characteristics along the penetration path in tissue were investigated experimentally by using a water phantom as tissue-equivalent absorber and the preliminary results include energy- and angular distributions, fragment yields, build-up curves and attenuation of the primary carbon projectiles.
Abstract: High-energy beams of (12)C ions in the range of 80-430 MeV u(-1) delivered by the heavy-ion synchrotron SIS-18 are used for radiotherapy of deep-seated localized tumors at the treatment unit at GSI Darmstadt. In order to improve the physical database, the fragmentation characteristics along the penetration path in tissue were investigated experimentally by using a water phantom as tissue-equivalent absorber. Measurements were performed at specific energies of 200 and 400 MeV u(-1) of the incident (12)C ions and at six different depths before and behind the Bragg peak. Secondary fragments with nuclear charges Z(f) = 1-5 were identified by scintillation detectors using AE-E and time-of-flight techniques. The preliminary results include energy- and angular distributions, fragment yields, build-up curves and attenuation of the primary carbon projectiles.
86 citations
TL;DR: The present work deals with the radioactivity of the Archeozoic-Cambrian rocks of the Weibei area, Shaanxi, China, and calculated the radium equivalent activity, the external hazard index, internal hazard index and the annual gonadal dose equivalent associated with the radionuclides compared with the international recommended values.
Abstract: The present work deals with the radioactivity of the Archeozoic-Cambrian rocks of the Weibei area, Shaanxi, China. A total of 45 rock samples of Archeozoic-Cambrian strata were investigated. The radionuclides of the samples, in Bq kg(-1), have been measured using Na(I)Tl gamma-ray spectrometer. The concentration of 226Ra, 232Th and 40K in the Archeozoic-Cambrian rock samples range from 12.3 to 55.4, from 2.4 to 98.7 and from 58.6 to 1613.3 Bq kg(-1), respectively. The measured activity concentrations for these radionuclides were compared with the typical world average values. To assess the radiological hazard of the natural radioactivity in the samples, the radium equivalent activity, the external hazard index, internal hazard index and the annual gonadal dose equivalent associated with the radionuclides were calculated and compared with the international recommended values.
84 citations
TL;DR: Patient and staff dose values in an interventional cardiology laboratory for different operational modes and several patient thicknesses (from 16 to 28 cm, simulated using polymethylmethacrylate) are presented to optimise protection of patients and staff.
Abstract: Patient and staff dose values in an interventional cardiology laboratory for different operational modes and several patient thicknesses (from 16 to 28 cm, simulated using polymethylmethacrylate) are presented. When increasing patient thicknesses and depending on fluoroscopy and cine modes, occupational doses can increase >30 times the baseline level. Scatter dose rates at the cardiologist's position with no radiation protective tools ranged from 1 to 14 mSv h(-1) for fluoroscopy, and from 10 to 47 mSv h(-1) during cine acquisition. Patient entrance surface air kerma rates increased by nearly 3 and staff dose rates by up to 2.6 when fluoroscopy was moved from the low to the high mode, for a typical 20 cm thickness. The respective increase factors were 6 and 4.2 when patient thickness rose from 16 to 28 cm, and by 10 and 8.3, when comparing cine acquisition with the low fluoroscopy mode. The knowledge of typical dose rates for each X-ray system in use in catheterisation laboratories is essential in order to optimise protection of patients and staff.
TL;DR: In this study, the activity concentrations of some radionuclides in tap water samples of the Eastern Black Sea region of Turkey were measured using high resolution gamma ray spectrometry and the effective doses were determined.
Abstract: In this study, the activity concentrations of some radionuclides in tap water samples of the Eastern Black Sea region of Turkey were measured. The activity concentrations of radionuclides (214)Pb, (214)Bi, (40)K, (226)Ra and (137)Cs were determined using high resolution gamma ray spectrometry. Furthermore, (222)Rn activity concentrations in tap water samples were measured using Liquid Scintillation Counting. The mean specific activities of (214)Pb, (214)Bi, (226)Ra, (40)K, (137)Cs and (222)Rn in tap water samples were 6.73, 6, 19.16, 168.57, 5.45 mBq l(-1) and 10.82 Bq l(-1), respectively. These values are comparable with concentrations reported for other countries. The effective doses were determined due to intake of these radionuclides as a consequence of direct consumption of tap water samples. The estimated effective doses were 6.878 x 10(-4) microSv y(-1) for (214)Pb, 4.800 x 10(-4) microSv y(-1) for (214)Bi, 3.916 microSv y(-1) for (226)Ra, 0.763 microSv y(-1) for (40)K, 0.052 microSv y(-1) for (137)Cs and 5.848 microSv y(-1) for (222)Rn.
TL;DR: These first results show that the newly synthesised material MgO doped with terbium (Tb) has some promising properties for the application in radiation dosimetry.
Abstract: In this paper main optically stimulated luminescence (OSL) and thermoluminescence (TL) characteristics are presented of a newly synthesised material MgO doped with terbium (Tb) developed at the Institute of Nuclear Science, Vinca. A thermally stimulated emission spectrum showed the characteristic lines of Tb3+ in a wide range of wavelengths. The TL sensitivity of the main TL glow peak at 315 degrees C is 1.7 times higher than the TL of Al2O3:C. The highest OSL sensitivity was obtained under green lamp (500-570 nm) stimulation. The fast component in the OSL decay curve is 2.4 times faster than Al2O3:C. The OSL signal is linear with dose up to 10 Gy. The lower limit of detection was found to be 100 microGy. These first results show that the newly synthesised material has some promising properties for the application in radiation dosimetry.
TL;DR: The dosimetry system has been used for dose measurements in a phantom during an intensity-modulated radiation therapy (IMRT) treatment with 6 MV photons and the RL measurement results are in excellent agreement with both the OSL results and the dose delivered according to the treatment planning system.
Abstract: Although the radioluminescence (RL) signal from optical fibre Al(2)O(3):C dosemeters used in medical applications is essentially proportional to dose rate, the crystals used so far are imperfect in the sense that their RL sensitivity changes with accumulated dose. A computational algorithm has been developed that corrects for these sensitivity changes. We further report on a new system that effectively separates the RL signal generated in the crystal from fluorescence and Cerenkov emission generated in the optical fibre cable using a gating technique in connection with pulsed linear accelerator radiation beams. The dosimetry system has been used for dose measurements in a phantom during an intensity-modulated radiation therapy (IMRT) treatment with 6 MV photons. The RL measurement results are in excellent agreement (i.e. within 1%) with both the OSL results and the dose delivered according to the treatment planning system. RL signals from Al(2)O(3):C can be used for real-time dose rate measurements with a time resolution of approximately 0.1 s and a spatial resolution only limited by the size of the detector (<0.5 mm).
TL;DR: The specific energy distributions in liquid water around the tracks of several HZE particles with energies up to 100 GeV n(-1) were calculated by performing track structure simulation with the Monte Carlo technique.
Abstract: Estimation of the specific energy distribution in a human body exposed to complex radiation fields is of great importance in the planning of long-term space missions and heavy ion cancer therapies. With the aim of developing a tool for this estimation, the specific energy distributions in liquid water around the tracks of several HZE particles with energies up to 100 GeV n(-1) were calculated by performing track structure simulation with the Monte Carlo technique. In the simulation, the targets were assumed to be spherical sites with diameters from 1 nm to 1 microm. An analytical function to reproduce the simulation results was developed in order to predict the distributions of all kinds of heavy ions over a wide energy range. The incorporation of this function into the Particle and Heavy Ion Transport code System (PHITS) enables us to calculate the specific energy distributions in complex radiation fields in a short computational time.
TL;DR: The RPLGD had not only good basic characteristics for reproducibility of readout value, dose linearity, energy dependence and fading, but also infinite repeatable measurements and could be one of the most important radiation dose measurement instruments.
Abstract: The radiophotoluminescent glass dosemeter (RPLGD) system is applicable for measurement of radiation dose of X rays and gamma rays by using radiophotoluminescent glass (silver-activated phosphate glass) When the radiophotoluminescent glass is exposed to ionizing radiation, stable luminescent centres are created During pulsed ultraviolet laser excitation (3371 nm) in the reader, the centres emit a radiation induced orange fluorescent light (600-700 nm) This phenomenon is called radiophotoluminescence This study compared the RPLGD system with lithium fluoride (LiF) thermoluminescence dosimetry system and the results of the study revealed that the RPLGD had not only good basic characteristics for reproducibility of readout value, dose linearity, energy dependence and fading, but also infinite repeatable measurements and could be one of the most important radiation dose measurement instruments
TL;DR: This paper presents the results of radon concentration measurements in drinking water from the municipal water supply system and private wells located in Baoji, China, finding the mean values of tap water and well water to be 12 kBq m(-3) with a maximum of 18 kBQ m (-3) and 41 kB QM(-3), respectively, while the contributions of the observed radon concentrations to indoor radon account for 2.2% of the mean value.
Abstract: This paper presents the results of radon concentration measurements in drinking water from the municipal water supply system and private wells located in Baoji, China. The measurements were carried out on 69 samples. The mean values of tap water and well water were found to be 12 kBq m -3 with a maximum of 18 kBq m -3 and 41 kBq m -3 with a maximum of 127 kBq m -3 , respectively. The well water samples obtained from different depth-well (water-bearing levels), i.e. shallow well (well depth under 10 m) water, middle well (well depth 10-30 m) water and deep well water, have respective mean values of 24, 34 and 56 kBq m -3 . The contributions of the observed radon concentration in drinking water to indoor radon account for 2.8-13.2% of the mean value of Shaanxi indoor radon concentration and the effective dose to the dweller owing to inhalation of radon emanating from household water is 0.03-0.14 mSv y -1 .
TL;DR: This paper presents the radioactivity concentrations of 226Ra, 232Th and 40K for 106 samples of surface soil collected in Southern Vietnam and estimates the average annual effective doses outdoors, indoors and in total are 0.067, 0.374 and 0.441 mSv.
Abstract: This paper presents the radioactivity concentrations of 226Ra, 232Th and 40K for 106 samples of surface soil collected in Southern Vietnam. The mean values of mass activity of radionuclides 226Ra, 232Th and 40K for Southern Vietnam are 28.6, 50.7 and 292.6 Bq kg(-1), respectively, which lead to the population-weighted absorbed dose rate of 54.5 nGy h(-1). The average annual effective doses outdoors, indoors and in total of Southern Vietnam are estimated to be 0.067, 0.374 and 0.441 mSv, respectively. The radium equivalent activity and the external hazard index of soil in Southern Vietnam are in the range 23.2-254.1 Bq kg(-1) and 0.06-0.69, respectively.
TL;DR: The main task of the MATROSHKA facility is to measure particle fluence and energy spectra, dose and dose rates outside and inside--including organ dose determination--in an anthropomorphic phantom mounted on the outside of the Space Station with passive and active dosemeter systems.
Abstract: On 29 January 2004 the MATROSHKA facility was launched with a Russian Progress to the International Space Station.
MATROSHKA is an ESA project, which has been achieved under the direction of the German Aerospace Center (DLR). The
project is a cooperation of >16 research institutes from all over the world and is currently the biggest international experiment
in radiation dosimetry ever performed in space. The facility simulates, as exact as possible, an astronaut during an
extravehicular activity. It was successfully installed outside the Russian segment ‘Zvezda’ on 26 February 2004 and will
remain there for a 1.5 year exposure period. The main task of the facility is to measure particle fluence and energy spectra,
dose and dose rates outside and inside—including organ dose determination—in an anthropomorphic phantom mounted on the
outside of the Space Station with passive and active dosemeter systems.
TL;DR: An exciting recent development is the availability of a new radiochromic emulsion which has been developed for IMRT dosimetry, an order of magnitude more sensitive than was previously available.
Abstract: NIST has been a pioneer in the use of radiochromic film for medical dosimetry applications. Beginning in 1988 with experiments with 90 Sr/Y ophthalmic applicators, this work has continued into the present. A review of the latest applications is presented, which include high activity low-energy photon source dosimetry and ultra-high resolution film densitometry for dose enhancement near stents and microbeam radiation therapy dosimetry. An exciting recent development is the availability of a new radiochromic emulsion which has been developed for IMRT dosimetry. This emulsion is an order of magnitude more sensitive than was previously available. Measurements of the sensitivity and uniformity of samples of this new film are reported, using a spectrophotometer and two scanning laser densitometers. A unique feature of the new emulsion is that the peak of the absorbance spectrum falls at the wavelength of the HeNe lasers used in the densitometer, maximising sensitivity. When read at a wavelength of 633 nm, sensitivities on the order of 900 mAU Gy -1 were determined for this new film type, compared with about 40 mAU Gy -1 for type HS film, 20 mAU Gy -1 for type MD-55-2 film, and 3 mAU Gy -1 for type HD-810. Film uniformities were found to be good, on the order of 6% peak to peak. However, there is a strong polarisation effect in the samples examined, requiring care in film orientation during readout.
TL;DR: The thermoluminescence dosemeter (TLD) was used for measuring radiation dose to family members of thyrotoxicosis and thyroid cancer patients treated with (131)I using CaSO(4):Dy discs to avoid close proximity with the patient.
Abstract: The thermoluminescence dosemeter (TLD) was used for measuring radiation dose to family members of thyrotoxicosis and thyroid cancer patients treated with (131)I using CaSO(4):Dy discs. There were 45 family members of thyrotoxicosis patients, who were divided into two groups with 22 in the first and 23 in the second group. Radiation safety instructions were the same for both the groups except in the second group where the patients were advised to use a separate bed at home for the first 3 d of dose administration. An activity ranging from 185 to 500 MBq was administered to these patients. The whole-body dose to family members ranged from 0.4 to 2.4 mSv (mean 1.1 mSv) in the first group and 0-1.9 mSv (mean 0.6 mSv) in the second group. A total of 297 family members of thyroid cancer patients were studied for whole-body dose estimation. An activity ranging from 0.925 to 7.4 GBq was administered to the thyroid cancer patients. The family members were divided into three groups depending upon the mode of transport and facilities available at home to avoid close proximity with the patient. Group A with 25 family members received a dose ranging from 0 to 0.9 mSv (mean 0.4 mSv), group B with 96 family members received a dose ranging from 0 to 8.5 mSv (mean 0.8 mSv) and group C with 176 family members received a dose ranging from 0 to 5.0 mSv (mean 0.8 mSv). The thyroid monitoring was also done in 103 family members who attended the patients in isolation wards for >2 d. Thyroid dose in them ranged from 0 to 2.5 mGy (mean 0.1 mGy).
TL;DR: A binary all-or-nothing model of triggering the bystanderser response is confirmed and the delay and persistence of the bystander response suggests a different mechanism of DSB induction in bystander cells than in directly irradiated cells.
Abstract: Radiation-induced bystander effect has been well documented However, the mechanisms are poorly understood How we incorporate this effect into the classical models of risk assessment remains an open question Here, the induction of bystander effect was studied by assessing DNA double-strand break (DSB) formation in situ with the rapid and sensitive c-H2AX focus formation assay Utilising the Columbia University single-cell microbeam system to deliver 2 or 20 individual alpha particles to selected cell nuclei in a precisely known proportion of cells in a population, the induced DNA DSB incidences were quantified 30 min and 18 h post-IR The increase in DNA DSB incidence in bystander cells lacked of a linear dose response indicating that neither the dose of irradiation nor proportion of irradiated cells in a population, is a critical parameter This study confirms a binary all-or-nothing model of triggering the bystander response The delay and persistence of the bystander response suggests a different mechanism of DSB induction in bystander cells than in directly irradiated cells
TL;DR: The biophysical simulation code PARTRAC was extended by a module to handle ions heavier than alpha particles to handle DNA damage patterns finding regional clusters in closer correlation to experimental cell inactivation data.
Abstract: The biophysical simulation code PARTRAC was extended by a module to handle ions heavier than alpha particles. Cross sections for ion-electron interactions were taken from He(++) ions of the same velocity and scaled by Z(eff(2))/4. Calculated linear energy transfer values, radial dose distributions and secondary electron spectra were found in agreement with experimental results. DNA damage due to irradiation of human fibroblast cells by several light ions from H to S was calculated for various energies complemented by 220 kV(p) X rays as reference radiation. With increasing linear energy transfer, the calculated total yield of double-strand breaks per dose showed saturation behaviour at about twice the value for reference radiation. When data analysis methods for experimental double-strand break yield determination were applied to the simulated DNA damage patterns, the two data sets were found in accord. The calculated patterns of DNA damage clusters were analysed on local and regional scale finding regional clusters in closer correlation to experimental cell inactivation data.
TL;DR: Applying the retrospective dosimetry method to post-Chernobyl studies has resulted in the development of new procedures using fired building materials with the capability to measure cumulative doses owing to artificial sources of gamma radiation as low as 20 mGy.
Abstract: There is a growing public awareness of the risk of accidental radiation exposure due to ageing nuclear power installations, illegal dumping of nuclear waste and terrorist activities, and of the consequential health risks to populations in addition to social and economic disturbance extending beyond national boundaries. In the event of catastrophic incidents where no direct radiation monitoring data are available, the application of retrospective dosimetry techniques such as luminescence may be employed with materials from the immediate environment to confirm values of cumulative gamma dose to compare with or augment computational modeling calculations. Application of the method to post-Chernobyl studies has resulted in the development of new procedures using fired building materials with the capability to measure cumulative doses owing to artificial sources of gamma radiation as low as 20 mGy. Combined with Monte Carlo simulations of photon transport, values of cumulative dose in brick can be presented in a form suitable for use in dose-reconstruction efforts. Recent investigations have also shown that certain types of cementitious building material, including concrete, mortar and plaster, and personal objects in the form of telephone cards containing microchips and dental ceramics have the potential to be used for retrospective dosimetry. Examples of the most recent research concerning new materials and examples of application to sites in the Former Soviet Union are discussed.
TL;DR: The cell specificity in inducing the bystander effect and in receiving the secreted signals that has been described suggests that not only the ability to release the cytokines but also the receptor profiles are likely to modulate the cell responses and the final outcome.
Abstract: Recent experimental evidence has challenged the paradigm according to which radiation traversal through the nucleus of a cell is a prerequisite for producing genetic changes or biological responses. Thus, unexposed cells in the vicinity of directly irradiated cells or recipient cells of medium from irradiated cultures can also be affected. The aim of the present study was to evaluate, by means of the medium transfer technique, whether interleukin-8 and its receptor (CXCR1) may play a role in the bystander effect after gamma irradiation of T98G cells in vitro. In fact the cell specificity in inducing the bystander effect and in receiving the secreted signals that has been described suggests that not only the ability to release the cytokines but also the receptor profiles are likely to modulate the cell responses and the final outcome. The dose and time dependence of the cytokine release into the medium, quantified using an enzyme linked immunosorbent assay, showed that radiation causes alteration in the release of interleukin-8 from exposed cells in a dose-independent but time-dependent manner. The relative receptor expression was also affected in exposed and bystander cells.
TL;DR: Both detectors show an enhanced response for kilovoltage photon beams, which in the case of 50 kV X rays is 3.2 times higher than that for 60Co gamma rays, and the addition of 0.1 or 1% of carbon by weight into the Al2O3 does not change the Monte Carlo determined energy-response factor.
Abstract: A Monte Carlo study of the energy-response factor of aluminium oxide (Al 2 O 3 ) and lithium fluoride (LiF) TLDs in kilovoltage and megavoltage photon beams relative to "Co gamma rays has been performed using EGSnrc Monte Carlo simulations The sensitive volume of the detector was simulated as a disc of diameter 285 mm and thickness 1 mm The phantom material was water and the irradiation depth was 20 cm in kilovoltage photon beams and 50 cm for megavoltage photon beams The results show that the energy-response of the Al 2 O 3 and LiF-TLDs is constant within 3% for photon beam energies in the energy range of "Co gamma rays to 25 MV X rays However, both detectors show an enhanced response for kilovoltage photon beams, which in the case of 50 kV X rays is 32 times higher than that for "Co gamma rays The energy-response factor was 146 for LiF irradiated in 50 kV X rays The Al 2 O 3 detector has an energy-response that is 22 times higher than that of LiF in 50 kV X rays decreasing to 119 for 250 kV X rays The results show that the addition of 01 or 1% of carbon by weight (as dopant) into the Al 2 O 3 does not change the Monte Carlo determined energy-response factor by more than 1%
TL;DR: The study showed that organ doses ranged from <0.01 to 0.72 mGy in routine X-ray radiography of chest and of abdomen and from 0.07 to 55.91 mGyIn routine computed tomography (CT) examinations with current multi-slice CT scanners, and the effective dose observed in the chest CT examination was approximately 300 times higher than that in chest radiography.
Abstract: Organ and the effective doses of patients undergoing clinical X ray examinations of chest and abdomen were evaluated with an anthropomorphic phantom and a new dosimetry system. The system was comprised of 34 pin photodiode dosemeters placed in/on particular tissues or organs of the anthropomorphic phantom, where the tissues and organs are defined by the International Commission on Radiological Protection (ICRP) to estimate the effective doses. Dosemeter signals were acquired on a personal computer directly, and converted into absorbed doses, from which the organ and the effective doses were evaluated on the computer. Our study showed that organ doses ranged from <0.01 to 0.72 mGy in routine X-ray radiography of chest and of abdomen and from 0.07 to 55.91 mGy in routine computed tomography (CT) examinations with current multi-slice CT scanners. The effective dose observed in the chest CT examination was approximately 300 times higher than that in chest radiography.
TL;DR: The gamma dose rates due to naturally occuring terrestrial radionuclides ((226)Ra, (232)Th and (40)K) were calculated based on their activities in soil samples, determined by gamma-ray spectrometry, and the radiation hazard was found to be insignificant for population living in the investigated area.
Abstract: The gamma dose rates due to naturally occuring terrestrial radionuclides ( 226 Ra, 232 Th and 40 K) were calculated based on their activities in soil samples, determined by gamma-ray spectrometry. A total of 140 soil samples from 21 different regions of Serbia and Montenegro were collected. The gamma dose rates ranged from 7.40 to 29.7 nGy h -1 for 226 Ra, from 12.9 to 46.5 nGy h -1 for 232 Th and from 12.5 to 37.1 nGy h -1 for 40 K. The total absorbed gamma dose rate due to these radionuclides varied from 34.5 to 97.6 nGy h -1 with mean of 66.8 nGy h -1 . Assuming a 20% occupancy factor, the corresponding annual effective dose varied from 4.23 x 10 -5 to 11.9 x 10 -5 Sv with mean of 8.19 x 10 -5 Sv, i.e. the dose was lower than world wide average value. According to the values of external hazard index (mean: 0.39) obtained in this study, the radiation hazard was found to be insignificant for population living in the investigated area.
TL;DR: The gamma absorbed dose rates at the roadsides in traffic density areas were found to be lower when compared with previously reported values in natural and undisturbed locations in non-traffic density areas in the city.
Abstract: The effect of ionising radiation on biological systems depends among other factors on time and place of exposure and population involved. Socio-economic factors in human daily activities have subjected humans to certain environmental health risks. In most cases the risk appears to be higher outdoors than indoors. In order to quantify the radiation exposure levels to individuals in the outdoors in areas with high human and vehicular densities, roadside soil samples were collected from major bus stops and round-about in the metropolis of Ibadan and were analysed for their activity concentration levels using gamma-ray spectrometry. The 40K activity concentration ranged between 96.1 and 336.5 Bq kg(-1) with a mean of 219.8 +/- 71.4 Bq kg(-1); 238U was in the range of 10.2-40.7 Bq kg(-1) with a mean of 20.3 +/- 6.9 Bq kg(-1) while that of 232Th ranged between 13.3 and 29.7 Bq kg(-1) with a mean of 21.2 +/- 5.3 Bq kg(-1). The total gamma absorbed dose rates in air ranged between 17.2 and 41.8 nGy h(-1) with an average of 32.0 +/- 5.8 nGy h(-1). The gamma absorbed dose rates at the roadsides in traffic density areas were found to be lower when compared with previously reported values in natural and undisturbed locations in non-traffic density areas in the city.
TL;DR: The experimental results presented suggest that dose might be the most significant factor in determining induction of GI after low-LET radiation.
Abstract: Genomic instability (GI) is a hallmark of tumorigenic progression and is observed as delayed genetic damage in the progeny of irradiated and unirradiated bystander cells. The expression of GI can be influenced by genotype, cell type and radiation quality. While several studies have demonstrated the induction of GI by high and low-linear energy transfer (LET) radiation, our work on human and mouse primary cell systems has shown LET-dependent differences in the induction and expression of GI. These differences might be attributed to differences in radiation track structure, dose rate, contribution of bystander cells and radiation dose. This paper reviews the role of radiation quality in the induction of GI and describe the possible mechanisms underlining the observed differences between radiation types on its induction. The experimental results presented suggest that dose might be the most significant factor in determining induction of GI after low-LET radiation.