| 1. |
- Champion, C., et al.
(författare)
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Dose point kernels in liquid water : An intra-comparison between GEANT4-DNA and a variety of Monte Carlo codes
- 2014
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 83, s. 137-141
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Tidskriftsartikel (refereegranskat)abstract
- Modeling the radio-induced effects in biological medium still requires accurate physics models to describe the interactions induced by all the charged particles present in the irradiated medium in detail. These interactions include inelastic as well as elastic processes. To check the accuracy of the very low energy models recently implemented into the GEANT4 toolkit for modeling the electron slowing-down in liquid water, the simulation of electron dose point kernels remains the preferential test. In this context, we here report normalized radial dose profiles, for mono-energetic point sources, computed in liquid water by using the very low energy GEANT4-DNA physics processes available in the GEANT4 toolkit. In the present study, we report an extensive intra-comparison of profiles obtained by a large selection of existing and well-documented Monte-Carlo codes, namely, EGSnrc, PENELOPE, CPA100, FLUKA and MCNPX.
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| 2. |
- Francis, Z., et al.
(författare)
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Molecular scale track structure simulations in liquid water using the Geant4-DNA Monte-Carlo processes
- 2011
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 69:1, s. 220-226
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a study of energy deposits induced by ionising particles in liquid water at the molecular scale Particles track structures were generated using the Geant4-DNA processes of the Geant4 Monte-Carlo toolkit These processes cover electrons (0 025 eV-1 MeV) protons (1 keV-100 MeV) hydrogen atoms (1 keV-100 MeV) and alpha particles (10 keV-40 MeV) including their different charge states Electron ranges and lineal energies for protons were calculated in nanometric and micrometric volumes
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| 3. |
- Gedda, Lars, et al.
(författare)
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Real-time immunohistochemistry analysis of embedded tissue
- 2010
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 68:12, s. 2372-2376
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel analysis of membrane-protein expression in tissue sections based on semi-automatic real-time measurement using LigandTracer(®) technology. A commercial antiHER2 antibody developed for immunohistochemistry used in this setup was revealed to have sub-optimal interaction with tissue when analyzed as recommended for immunohistochemistry. We therefore think that real-time measurement of tissue, offering direct and quantitative membrane-protein interaction analysis, can lead to improved reproducibility and eliminate the subjective operator dependences that classical immunohistochemsitry suffers from.
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| 4. |
- He, Qinggang, et al.
(författare)
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Electrochemical nucleophilic synthesis of di-tert-butyl-(4-[F-18]fluoro-1,2-phenylene)-dicarbonate
- 2014
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 92, s. 52-57
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Tidskriftsartikel (refereegranskat)abstract
- An electrochemical method with the ability to conduct F-18-fluorination of aromatic molecules through direct nucleophilic fluorination of cationic intermediates is presented in this paper. The reaction was performed on a remote-controlled automatic platform. Nucleophilic electrochemical fluorination of tert-butyloxycarbonyl (Boc) protected catechol, an intermediate model molecule for the positron emission tomography (PET) probe (3,4-dihydroxy-6-[F-18]fluoro-L-phenylalanine), was performed. Fluorination was achieved under potentiostatic anodic oxidation in acetonitrile containing Et3N center dot 3HF and other supporting electrolytes. Radiofluorination efficiency was influenced by a number of variables, including the concentration of the precursor, concentration of Et3N center dot 3HF, type of supporting electrolyte, temperature and time, as well as applied potentials. Radiofluorination efficiency of 10.4 +/- 0.6% (n=4) and specific activity of up to 43 GBq/mmol was obtained after 1 h electrolysis of 0.1 M of 4-tert-butyl-diboc-catechol in the acetonitrile solution of Et3N center dot 3HF (0.033 M) and NBu4PF6 (0.05 M). Density functional theory (DFT) was employed to explain the tert-butyl functional group facilitation of electrochemical oxidation and subsequent fluorination.
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| 5. |
- Holmgren, S., et al.
(författare)
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Handling interferences in Sr-89 and Sr-90 measurements of reactor coolant water: A method based on strontium separation chemistry
- 2014
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 90:Aug., s. 94-101
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Tidskriftsartikel (refereegranskat)abstract
- Measurements for determining the activity of Sr-89 and Sr-90 in reactor coolant water are associated with limitations due to interferences from radionuclides with similar chemical properties and beta(-)-energies. From a measurement bias point-of-view these interferences would result mainly in an overestimated activity concentration of Sr-90. In order to address the interference problem, a common and well-known method was used in order to show the need for sufficient decontamination. An improvement was achieved by taking the sample through two initial strontium separations in order to increase the decontamination factor. This method determines the activity concentration of Sr-89 and Sr-90, via its daughter nuclide Y-90, by Cherenkov counting. This work is primarily based on theoretical calculations of strontium-, yttrium- and other potential interfering radionuclide ratios after instant fission. The work done to confirm the theoretical calculations were carried through on spiked strontium standard solutions and fresh reactor coolant water. The reactor coolant water was known to contain interferences at a composition resembling that of instant fission. The detection limit for double separation was calculated to 0.17 Bq/kg for Sr-90 and 0.38 Bq/kg for Sr-89. When using methods that solely rely on strontium resins, this paper shows that the decontamination factor (DF) is significantly higher when using double separation than that of a single separation. The paper also shows that the DF of an initial double strontium separation is as effective when it comes to removing high ratio interferences as separations done with both Sr- and Ln-resin (EiChrom Technologies, Inc., 2003; Tovedal at at, 2009b). However, 'old' samples, where e.g. Ba-140 and Sr-89 has decayed, does not benefit from double separation. Furthermore, samples with low ratios of interfering radionuclides does not benefit from using this method either, seeing as this is a more time consuming method due to the double separations.
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| 6. |
- Kastlander, Johan, et al.
(författare)
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In-situ method to determine depth distribution of buried activity
- 2011
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 69:5, s. 773-779
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Tidskriftsartikel (refereegranskat)abstract
- A method is described to determine the depth distribution of buried activity offering an alternative to conventional soil sampling and laboratory analysis by in-situ measurements with small detectors inserted into the ground. As ad demonstration of the method small-scale variations in the distribution of Cs-137 in a riparian marsh in central-eastern Sweden are determined using lanthanum bromide detectors (LaBr3). The results show variations of the activity ranging between 400 and 2200 kBq/m^2 over an area not exceeding 350 m^2. The decrease of the average activity since 2003 coincides with the physical decay indicating that no net redistribution of activity into this part of the marsh has occurred during the inter weening years.
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| 7. |
- Mukhopadhyay, Nitai D, et al.
(författare)
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Estimating statistical uncertainty of Monte Carlo efficiency-gain in the context of a correlated sampling Monte Carlo code for brachytherapy treatment planning with non-normal dose distribution
- 2012
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Ingår i: Applied Radiation and Isotopes. - UK : Pergamon. - 0969-8043 .- 1872-9800. ; 70:1, s. 315-323
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Tidskriftsartikel (refereegranskat)abstract
- Correlated sampling Monte Carlo methods can shorten computing times in brachytherapy treatment planning. Monte Carlo efficiency is typically estimated via efficiency gain, defined as the reduction in computing time by correlated sampling relative to conventional Monte Carlo methods when equal statistical uncertainties have been achieved. The determination of the efficiency gain uncertainty arising from random effects, however, is not a straightforward task specially when the error distribution is non-normal. The purpose of this study is to evaluate the applicability of the F distribution and standardized uncertainty propagation methods (widely used in metrology to estimate uncertainty of physical measurements) for predicting confidence intervals about efficiency gain estimates derived from single Monte Carlo runs using fixed-collision correlated sampling in a simplified brachytherapy geometry. A bootstrap based algorithm was used to simulate the probability distribution of the efficiency gain estimates and the shortest 95% confidence interval was estimated from this distribution. It was found that the corresponding relative uncertainty was as large as 37% for this particular problem. The uncertainty propagation framework predicted confidence intervals reasonably well; however its main disadvantage was that uncertainties of input quantities had to be calculated in a separate run via a Monte Carlo method. The F distribution noticeably underestimated the confidence interval. These discrepancies were influenced by several photons with large statistical weights which made extremely large contributions to the scored absorbed dose difference. The mechanism of acquiring high statistical weights in the fixed-collision correlated sampling method was explained and a mitigation strategy was proposed.
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| 8. |
- Pham, M. K., et al.
(författare)
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Certified Reference Material IAEA-446 for radionuclides in Baltic Sea seaweed
- 2014
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 87, s. 468-474
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Tidskriftsartikel (refereegranskat)abstract
- A Certified Reference Material (CRM) for radionuclides in seaweed (Fucus vesiculosus) from the Baltic Sea (IAEA-446) is described and the results of the certification process are presented. The K-40, Cs-132, U-234 and Pu239+240 radionuclides were certified for this material, and information values for 12 other radionuclides (Sr-90, Tc-99, Pb-210 (Po-210), Ra-226, Ra-228, Th-228, Th-230, Th-232, U-235, U-238, Pu-239 and Pu-240) are presented. The CRM can be used for Quality Assurance/Quality Control of analysis of radionuclides in seaweed and other biota samples, as well as for development and validation of analytical methods, and for training purposes. (C) 2013 Elsevier Ltd. All rights reserved.
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| 9. |
- Qiao, Jixin, et al.
(författare)
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Speciation analysis of 129I, 137Cs, 232Th, 238U, 239Pu and 240Pu in environmental soil and sediment
- 2012
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 70:8, s. 1698-1708
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Tidskriftsartikel (refereegranskat)abstract
- The environmental mobility and bioavailability of radionuclides are related to their physicochemical forms, namely species. We here present a speciation analysis of important radionuclides including I-129 (also I-127), Cs-137, Th-232, U-238 and plutonium isotopes (Pu-239 and Pu-240) in soil (IAEA-375) and sediment (NIST-4354) standard reference materials and two fresh sediment samples from Ovre Heimdalsvatnet Lake, Norway. A modified sequential extraction protocol was used for the speciation analysis of these samples to obtain fractionation information of target radionuclides. Analytical results reveal that the partitioning behaviour, and thus the potential mobility and bioavailability, are exclusively featured for the individual radionuclide. Iodine is relatively mobile and readily binds to organic matter, while plutonium is mainly bound to both organic matter and nitric acid leachable fractions. Thorium is predominated in nitric acid leachable fraction and caesium is primarily observed in nitric acid and aqua regia leachable fractions and residue. Our analytical results reveal that around 50% of uranium might still remain in the residue which could not be extracted with aggressive acid, namely, aqua regia.
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| 10. |
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