| 1. |
- Lillhök, J E, et al.
(författare)
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Nanodosimetry in a clinical neutron therapy beam using the variance-covariance method and Monte Carlo simulations.
- 2007
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Ingår i: Physics in Medicine and Biology. - : IOP. - 0031-9155 .- 1361-6560. ; 52:16, s. 4953-66
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Nanodosimetric single-event distributions or their mean values may contribute to a better understanding of how radiation induced biological damages are produced. They may also provide means for radiation quality characterization in therapy beams. Experimental nanodosimetry is however technically challenging and Monte Carlo simulations are valuable as a complementary tool for such investigations. The dose-mean lineal energy was determined in a therapeutic p(65)+Be neutron beam and in a Co-60 gamma. beam using low-pressure gas detectors and the variance-covariance method. The neutron beam was simulated using the condensed history Monte Carlo codes MCNPX and SHIELD-HIT. The dose-mean lineal energy was calculated using the simulated dose and fluence spectra together with published data from track-structure simulations. A comparison between simulated and measured results revealed some systematic differences and different dependencies on the simulated object size. The results show that both experimental and theoretical approaches are needed for an accurate dosimetry in the nanometer region. In line with previously reported results, the dose-mean lineal energy determined at 10 nm was shown to be related to clinical RBE values in the neutron beam and in a simulated 175 MeV proton beam as well.
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| 2. |
- Grindborg, J.-E., et al.
(författare)
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Nanodosimetric measurements and calculations in a neutron therapy beam
- 2007
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 126:1-4, s. 463-466
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Tidskriftsartikel (refereegranskat)abstract
- A comparison of calculated and measured values of the dose mean lineal energy (yD) for the former neutron therapy beam at Louvain-la-Neuve is reported. The measurements were made with wall-less tissue-equivalent proportional counters using the variance-covariance method and simulating spheres with diameters between 10 nm and 15 µm. The calculated yD-values were obtained from simulated energy distributions of neutrons and charged particles inside an A-150 phantom and from published yD-values for mono-energetic ions. The energy distributions of charged particles up to oxygen were determined with the SHIELD-HIT code using an MCNPX simulated neutron spectrum as an input. The mono-energetic ion yD-values in the range 3-100 nm were taken from track-structure simulations in water vapour done with PITS/KURBUC. The large influence on the dose mean lineal energy from the light ion (A > 4) absorbed dose fraction, may explain an observed difference between experiment and calculation. The latter being larger than earlier reported result. Below 50 nm, the experimental values increase while the calculated decrease. © The Author 2007. Published by Oxford University Press. All rights reserved.
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| 3. |
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| 4. |
- Carlsson Tedgren, Åsa, 1968-, et al.
(författare)
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192-Ir source strength dosimetry audit in Sweden
- 2007
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Ingår i: 9th Biennial ESTRO meeting on physics and radiation technology for clinical radiotherapy,2007. ; , s. S143-S143
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Posters Brachytherapy, publicerad i Radiotherapy and Oncology.
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| 5. |
- Malusek, Alexandr, et al.
(författare)
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In-situ calibration of clinical built-in KAP meters with traceability to a primary standard using a reference KAP meter
- 2014
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Ingår i: Physics in Medicine and Biology. - : IOP Publishing: Hybrid Open Access. - 0031-9155 .- 1361-6560. ; 59:23, s. 7195-7210
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Tidskriftsartikel (refereegranskat)abstract
- The air kerma-area product (KAP) is used for settings of diagnostic reference levels. The International Atomic Energy Agency (IAEA) recommends that doses in diagnostic radiology (including the KAP values) be estimated with an accuracy of at least +/- 7% (k = 2). Industry standards defined by the International Electrotechnical Commission (IEC) specify that the uncertainty of KAP meter measurements should be less than +/- 25% (k = 2). Medical physicists willing to comply with the IAEAs recommendation need to apply correction factors to KAP values reported by x-ray units. The aim of this work is to present and evaluate a calibration method for built-in KAP meters on clinical x-ray units. The method is based on (i) a tandem calibration method, which uses a reference KAP meter calibrated to measure the incident radiation, (ii) measurements using an energy-independent ionization chamber to correct for the energy dependence of the reference KAP meter, and (iii) Monte Carlo simulations of the beam quality correction factors that correct for differences between beam qualities at a standard laboratory and the clinic. The method was applied to the KAP meter in a Siemens Aristos FX plus unit. It was found that values reported by the built-in KAP meter differed from the more accurate values measured by the reference KAP meter by more than 25% for high tube voltages (more than 140 kV) and heavily filtered beams (0.3 mm Cu). Associated uncertainties were too high to claim that the IECs limit of 25% was exceeded. Nevertheless the differences were high enough to justify the need for a more accurate calibration of built-in KAP meters.
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