| 1. |
- Almgren, Sara, 1979, et al.
(författare)
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GIS supported calculations of (137)Cs deposition in Sweden based on precipitation data.
- 2006
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Ingår i: The Science of the total environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 368:2-3, s. 804-13
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Tidskriftsartikel (refereegranskat)abstract
- It is of interest to know the spatial variation and the amount of (137)Cs e.g. in case of an accident with a radioactive discharge. In this study, the spatial distribution of the quarterly (137)Cs deposition over Sweden due to nuclear weapons fallout (NWF) during the period 1962-1966 was determined by relating the measured deposition density at a reference site to the amount of precipitation. Measured quarterly values of (137)Cs deposition density per unit precipitation at three reference sites and quarterly precipitation at 62 weather stations distributed over Sweden were used in the calculations. The reference sites were assumed to represent areas with different quarterly mean precipitation. The extent of these areas was determined from the distribution of the mean measured precipitation between 1961 and 1990 and varied according to seasonal variations in the mean precipitation pattern. Deposition maps were created by interpolation within a geographical information system (GIS). Both integrated (total) and cumulative (decay corrected) deposition densities were calculated. The lowest levels of NWF (137)Cs deposition density were noted in north-eastern and eastern parts of Sweden and the highest levels in the western parts of Sweden. Furthermore the deposition density of (137)Cs, resulting from the Chernobyl accident was determined for an area in western Sweden based on precipitation data. The highest levels of Chernobyl (137)Cs in western Sweden were found in the western parts of the area along the coast and the lowest in the east. The sum of the deposition densities from NWF and Chernobyl in western Sweden was then compared to the total activity measured in soil samples at 27 locations. Comparisons between the predicted values of this study show a good agreement with measured values and other studies.
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| 2. |
- Bernitt Cartemo, Petty, 1984, et al.
(författare)
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Building a generic voxel phantom ofIRINA for Monte Carlo simulations
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The human phantom IRINA, which is widely used for whole body counting calibrations, has been modelled using MATLAB. This document summa-rizes and explains the procedure that was applied for building voxel ver-sions of IRINA in standing position. All 6 sizes in standing positions were successfully modelled with the help of MATLAB and the files are ready to use for any MC simulation. The MC code GATE was used to verify the geometry of the IRINA phantom by comparing the placement of source tubes and scatterers in the Monte Carlo model to the original IRINA docu-mentation. The methodology can easily be used for building voxel phan-toms of IRINA in sitting and bending position, as well as any other geome-try that may be needed.
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| 3. |
- Bernitt Cartemo, Petty, 1984, et al.
(författare)
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Comparison of computational phantoms and investigation of the effect of biodistribution on activity estimations
- 2016
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 171:3, s. 358-364
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Tidskriftsartikel (refereegranskat)abstract
- We have made a comparison between two computational phantoms, modeled from the unified phantom UPh-08T, for whole-body counting applications. One of these was further compared with the ICRP reference adult male computational phantom. The simulations that were performed for the comparison of all three voxel phantoms use various distributions of 60Co. The two voxel phantoms of the UPh-08T showed good agreement, despite different methods of phantom modeling. Also, effects on efficiency of the inhomogeneous distribution of a radionuclide in the computational UPh-08T phantom were studied, using the realistic biodistribution of 140La. Our results show that the activity estimation of radionuclides, which are inhomogeneously distributed in the human body, will be in error if a homogeneous distribution is assumed for the calibration of whole-body counting systems.
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| 4. |
- Cartemo, Petty, et al.
(författare)
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Letter to the Editor.
- 2016
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 168:2
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Nilsson, Jenny, et al.
(författare)
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A comparison between Monte Carlo-calculated and -measured total efficiencies and energy resolution for large plastic scintillators used in whole-body counting.
- 2011
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Ingår i: Radiation protection dosimetry. - : Oxford University Press (OUP). - 1742-3406 .- 0144-8420. ; 144:1-4, s. 555-9
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Tidskriftsartikel (refereegranskat)abstract
- The measured total efficiency for several source positions has been determined for a large, plastic scintillation detector (NE 102A, 91.5 × 76.0 × 24.5 cm(3)) used for whole-body counting gamma spectrometry. The results have been compared with Monte Carlo-calculated total efficiencies; the code used was MCNPX 2.60. For (137)Cs, there was a good agreement between the measured and calculated total efficiencies. MXNPX was also used to calculate the electron light yield for (137)Cs; for the detector material NE 102A, Birks' constant kB was found to be 9.6 mg cm(-2) MeV(-1). The effect of light losses on spectrum resolution has been investigated for (65)Zn.
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| 6. |
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| 7. |
- Nilsson, Jenny, et al.
(författare)
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A MONTE CARLO CALIBRATION OF A WHOLE BODY COUNTER USING THE ICRP COMPUTATIONAL PHANTOMS.
- 2015
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 163:4, s. 458-467
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Tidskriftsartikel (refereegranskat)abstract
- A fast and versatile calibration of a whole body counter (WBC) is presented. The WBC, consisting of four large plastic scintillators, is to be used for measurements after accident or other incident involving ionising radiation. The WBC was calibrated using Monte Carlo modelling and the ICRP computational phantoms. The Monte Carlo model of the WBC was made in GATE, v6.2 (Geant4 Application for Tomographic Emission) and MATLAB. The Monte Carlo model was verified by comparing simulated energy spectrum and simulated counting efficiency with experimental energy spectrum and experimental counting efficiency for high-energy monoenergetic gamma-emitting point sources. The simulated results were in good agreement with experimental results except when compared with experimental results from high dead-time (DT) measurements. The Monte Carlo calibration was made for a heterogeneous source distribution of (137)Cs and (40)K, respectively, inside the ICRP computational phantoms. The source distribution was based on the biokinetic model for (137)Cs.
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| 8. |
- Nilsson, Jenny, et al.
(författare)
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Can GATE Be Used For Monte Carlo Calibrations Of Whole Body Counters?
- 2012
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Ingår i: 13th International Congress of the International Radiation Protection Association (IRPA) in Glasgow, 13-18 May 2012.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the presented work is to determine if GATE can be used for Monte Carlo calibration of a whole body counter scintillation spectrometer system consisting of large plastic detectors. GATE is an open source software, on a GEANT4 platform, dedicated to medical use such as PET and SPECT. Even though whole body counting scintillator spectrometer systems and PET/SPECT systems have different purposes and complexity, there are a few fundamental similarities: the use of scintillation detectors, moveable detectors, source inside a patient and the amplification method of the detector signal. Compared to whole body counting, the PET/SPECT medical field is large, which affects the development of system specific software such as GATE in a positive direction. However, if it is possible to use GATE for whole body counting specific problems as well, then a rather small field of research could benefit from the already extensive work done in a larger. If so GATE can be used instead of in-house codes, or general-purpose codes that may not be specific enough for whole body counting purposes. In this work, GATE will be used to investigate the optical transport in large plastic scintillators and its effect on intrinsic spectrum resolution. Further, since the signal from a plastic scintillator needs to be amplified, it will be investigated if it is possible to simulate a broadened spectrum produced by a photomultiplier tube. If these two problems are possible to simulate using GATE, then GATE would be a promising software to be used for a Monte Carlo calibration of whole body counters. The results of these finding will be presented at the conference together with the conclusion whether GATE can be used also for whole body counting.
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| 9. |
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| 10. |
- Nilsson, Jenny, et al.
(författare)
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How to transform a nail into a hay stack – key processes in simulating a proper plastic scintillator spectrum from a Monte Carlo modeled energy deposition peak!
- 2014
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Ingår i: The 4th European Regional IRPA Congress, June 23rd to June 27th 2014, Genève Schweiz.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The rather sharp peak in a Monte Carlo simulated spectrum of energy deposition in a large plastic scintillator bears little resemblance with a measured spectrum, which consists of a broad hump. The aim of the presented work is to find the key parameters in GATE to simulate the response of a large plastic scintillator for subsequent Monte Carlo calibration of a whole body counter. GATE is open source software, on a GEANT4 platform, which has been found useful for simulating the response from scintillation detectors. It has been shown that by carefully defining the plastic scintillator surface and material properties used in the model of optical photon transport a good resemblance between a simulated and a measured spectrum could be achieved. Simply applying a broadening function (i.e. a Gaussian) available in most Monte Carlo codes does not account for the complex behavior of optical photons in a large scintillator. In GATE, an optical photon is transported through the material until it reaches a boundary where it is either reflected, refracted or absorbed. The properties of the surface are chosen by the user. We have found that the most important parameters are: surface finish, reflectivity and the probability distribution for the different modes of reflection (specular lobe, specular spike, Lambertian or backscatter).
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