A comparative validation of biodosimetry and physical dosimetry techniques for possible triage applications in emergency dosimetry.

Large-scale radiological accidents or nuclear terrorist incidents involving radiological or nuclear materials can potentially expose thousands, or hundreds of thousands, of people to unknown radiation doses, requiring prompt dose reconstruction for appropriate triage. Two types of dosimetry methods namely, biodosimetry and physical dosimetry are currently utilized for estimating absorbed radiation dose in humans. Both methods have been tested separately in several inter-laboratory comparison exercises, but a direct comparison of physical dosimetry with biological dosimetry has not been performed to evaluate their dose prediction accuracies. The current work describes the results of the direct comparison of absorbed doses estimated by physical (smartphone components) and biodosimetry (dicentric chromosome assay (DCA) performed in human peripheral blood lymphocytes) methods. For comparison, human peripheral blood samples (biodosimetry) and different components of smartphones, namely surface mount resistors (SMRs), inductors and protective glasses (physical dosimetry) were exposed to different doses of photons (0-4.4 Gy; values refer to dose to blood after correction) and the absorbed radiation doses were reconstructed by biodosimetry (DCA) and physical dosimetry (optically stimulated luminescence (OSL)) methods. Additionally, LiF:Mg,Ti (TLD-100) chips and Al2O3:C (Luxel) films were used as reference TL and OSL dosimeters, respectively. The best coincidence between biodosimetry and physical dosimetry was observed for samples of blood and SMRs exposed toγ-rays. Significant differences were observed in the reconstructed doses by the two dosimetry methods for samples exposed to x-ray photons with energy below 100 keV. The discrepancy is probably due to the energy dependence of mass energy-absorption coefficients of the samples extracted from the phones. Our results of comparative validation of the radiation doses reconstructed by luminescence dosimetry from smartphone components with biodosimetry using DCA from human blood suggest the potential use of smartphone components as an effective emergency triage tool for high photon energies.

Integration of new biological and physical retrospective dosimetry methods into EU emergency response plans - joint RENEB and EURADOS inter-laboratory comparisons.

PURPOSE: RENEB, 'Realising the European Network of Biodosimetry and Physical Retrospective Dosimetry,' is a network for research and emergency response mutual assistance in biodosimetry within the EU. Within this extremely active network, a number of new dosimetry methods have recently been proposed or developed. There is a requirement to test and/or validate these candidate techniques and inter-comparison exercises are a well-established method for such validation. MATERIALS AND METHODS: The authors present details of inter-comparisons of four such new methods: dicentric chromosome analysis including telomere and centromere staining; the gene expression assay carried out in whole blood; Raman spectroscopy on blood lymphocytes, and detection of radiation-induced thermoluminescent signals in glass screens taken from mobile phones. RESULTS: In general the results show good agreement between the laboratories and methods within the expected levels of uncertainty, and thus demonstrate that there is a lot of potential for each of the candidate techniques. CONCLUSIONS: Further work is required before the new methods can be included within the suite of reliable dosimetry methods for use by RENEB partners and others in routine and emergency response scenarios.

Ionisation density dependence of the optically stimulated luminescence dose-response of AL2O3:C to low-energy charged particles.

The optically stimulated luminescence (OSL) response of Al2O3:C to high doses of gamma or beta irradiation can be used to predict the response of this material to charged particles as a function of particle fluence, particle energy and/or linear energy transfer (LET). In particular, it is predicted that track interaction effects at high particle fluences should result in linear-sublinear growth of the OSL signal. Similar considerations also predict a dependence of the fluence at which sublinearity starts upon the energy of the particles. In this work the OSL response of Al2O3:C to low-energy charged particles was investigated using protons (1, 2 and 4 MeV), carbon ions (13 MeV) and oxygen ions (10 MeV). The sublinear growth predicted above was qualitatively confirmed, but the energy dependence prediction was not. Furthermore, the efficiency of OSL production in the material after charged particle irradiation, compared to that obtained for gamma irradiation, is determined from the dose-response curves by fitting to a simple saturating exponential function. The efficiency values so obtained using this method are compared with those obtained from a conventional single-point measurement in the linear portion of the curve and found to be in good agreement. In general, the efficiency decreases as the LET of the particle increases. The present data are compared with published data obtained using high-energy charged particles and the results show that the efficiency is not a unique function of LET.

Ionisation density dependence of the optically and thermally stimulated luminescence from Al2O3:C.

This paper presents an overview of recent results on ionisation density dependence of the thermally stimulated luminescence (TL) and optically stimulated luminescence (OSL) signals from Al2O3:C, with emphasis on the sensitivity, efficiency, shape of the TL/OSL curves and the emission spectrum. High-ionisation densities are created uniformly by accumulated high doses of low-linear energy transfer radiation (gamma, beta, X rays) or non-uniformly in heavy charged particle tracks, even at low fluences, as in the case of space radiation fields. Significant deep trap filling, which occurs at these high-ionisation densities, ultimately results in changes in the concentration of recombination centres (F+-centres) and, consequently, in sensitivity changes and other effects. An OSL emission band at 335 nm has been observed in addition to the main F-centre luminescence band, and the relative intensities of these bands have been observed to be dependent on the ionisation density. The implications of these results and open issues are discussed.

Recent advances in dosimetry using the optically stimulated luminescence of Al2O3:C.

This paper presents an overview of some very recent developments in optically stimulated luminescence (OSL) dosimetry using aluminium oxide (Al(2)O(3):C), with special emphasis given to the work of the research group at Oklahoma State University. Some of the advances are: (i) the development of a real-time optical fibre system for in vivo dosimetry applied to radiotherapy; (ii) the development of a fibre dosimetry system for remote detection of radiological contaminants in soil; (iii) the characterisation of Al(2)O(3):C in heavy charged particle fields and the study of ionisation density dependence of the OSL from Al(2)O(3):C; and (iv) fast and separate assessment of beta and gamma components of the natural dose rate in natural sediments. These achievements highlight the versatility of the OSL technique associated with the high-sensitivity of Al(2)O(3):C for the development of new dosimetry applications.