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A comparison of ambient dose equivalent meters and dose calculations at constant flight conditions
Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI).
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2007 (English)In: Radiation Measurements, ISSN 1350-4487, Vol. 42, no 3, 323-333 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier Ltd , 2007. Vol. 42, no 3, 323-333 p.
Keyword [en]
Aircrew exposure; Cosmic radiation; TEPC; Microdosimetry; Variance–covariance method
National Category
Physical Sciences
URN: urn:nbn:se:su:diva-24149DOI: 10.1016/j.radmeas.2006.12.011OAI: diva2:196872
Part of urn:nbn:se:su:diva-6687Available from: 2007-03-01 Created: 2007-02-26 Last updated: 2011-01-19Bibliographically approved
In thesis
1. The microdosimetric variance-covariance method used for beam quality characterization in radiation protection and radiation therapy
Open this publication in new window or tab >>The microdosimetric variance-covariance method used for beam quality characterization in radiation protection and radiation therapy
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Radiation quality is described by the RBE (relative biological effectiveness) that varies with the ionizing ability of the radiation. Microdosimetric quantities describe distributions of energy imparted to small volumes and can be related to RBE. This has made microdosimetry a powerful tool for radiation quality determinations in both radiation protection and radiation therapy. The variance-covariance method determines the dose-average of the distributions and has traditionally been used with two detectors to correct for beam intensity variations. Methods to separate dose components in mixed radiation fields and to correct for beam variations using only one detector have been developed in this thesis. Quality factor relations have been optimized for different neutron energies, and a new algorithm that takes single energy deposition events from densely ionizing radiation into account has been formulated. The variance-covariance technique and the new methodology have been shown to work well in the cosmic radiation field onboard aircraft, in the mixed photon and neutron fields in the nuclear industry and in pulsed fields around accelerators.

The method has also been used for radiation quality characterization in therapy beams. The biological damage is related to track-structure and ionization clusters and requires descriptions of the energy depositions in nanometre sized volumes. It was shown that both measurements and Monte Carlo simulation (condensed history and track-structure) are needed for a reliable nanodosimetric beam characterization. The combined experimental and simulated results indicate that the dose-mean of the energy imparted to an object in the nanometre region is related to the clinical RBE in neutron, proton and photon beams. The results suggest that the variance-covariance technique and the dose-average of the microdosimetric quantities could be well suited for describing radiation quality also in therapy beams.

Place, publisher, year, edition, pages
Stockholm: Medicinsk strålningsfysik (tills m KI), 2007. 146 p.
ionizing radiation, radiation quality, radiation protection, radiation therapy, microdosimetry, nanodosimetry, variance-covariance method
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Medical Radiation Physics
urn:nbn:se:su:diva-6687 (URN)91-7155-391-6 (ISBN)
Public defence
2007-03-23, föreläsningssalen, Radiumhemmet, Karolinska universitetssjukhuset, Solna, 10:00
Available from: 2007-03-01 Created: 2007-02-26Bibliographically approved

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