| 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. |
- Lillhök, J E, et al.
(författare)
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A comparison of ambient dose equivalent meters and dose calculations at constant flight conditions
- 2007
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Ingår i: Radiation Measurements. - : Elsevier Ltd. - 1350-4487 .- 1879-0925. ; 42:3, s. 323-333
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Tidskriftsartikel (refereegranskat)abstract
- Ambient dose-equivalent results from an in-flight comparison between different tissue-equivalent proportional counters and silicon diode spectrometers from seven European institutes are presented and compared with calculations using the EPCARD computer program. The measurements were performed on 40 000 and 32 000 ft in narrow target areas at latitudes N57 and N42. Keeping the altitude and geographic position almost constant provided unique conditions for comparisons. The different measuring systems as well as the calculations are in remarkably good agreement, with an average standard deviation in the ambient dose equivalent between 6% and 21%. The ratio between calculated and measured ambient dose-equivalent rates varies between 0.91 and 1.09, with an average of 1.00±0.08 (1s). Nevertheless some systematic differences in the experimentally determined ambient dose equivalent and its low-LET and high-LET components are noticed and discussed. It is concluded that the standard deviation between different instruments can through optimization and harmonization of the calibration procedures be reduced by up to a factor of two.
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| 3. |
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| 4. |
- Lillhök, J., et al.
(författare)
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RADIATION PROTECTION MEASUREMENTS WITH THE VARIANCE-COVARIANCE METHOD IN THE STRAY RADIATION FIELDS FROM PHOTON AND PROTON THERAPY FACILITIES
- 2018
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Ingår i: Radiation Protection Dosimetry. - : Oxford University Press (OUP). - 0144-8420 .- 1742-3406. ; 180:1-4, s. 338-341
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Tidskriftsartikel (refereegranskat)abstract
- The microdosimetric variance-covariance method was used to study the stray radiation fields from the photon therapy facility at the Technical University of Denmark and the scanned proton therapy beam at the Skandion Clinic in Uppsala, Sweden. Two TEPCs were used to determine the absorbed dose, the dose-average lineal energy, the dose-average quality factor and the dose equivalent. The neutron component measured by the detectors at the proton beam was studied through Monte Carlo simulations using the code MCNP6. In the photon beam the stray absorbed dose ranged between 0.3 and 2.4 mu Gy per monitor unit, and the dose equivalent between 0.4 and 9 mu Sv per monitor unit, depending on beam energy and measurement position. In the proton beam the stray absorbed dose ranged between 3 and 135 mu Gy per prescribed Gy, depending on detector position and primary proton energy.
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