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Denis G.,Oklahoma State University | Akselrod M.S.,Landauer Inc. | Yukihara E.G.,Oklahoma State University
Journal of Applied Physics | Year: 2011

The objective of this paper is to investigate the influence of shallow traps on the signals from Al2O3:C,Mg obtained using time-resolved optically stimulated luminescence (TR-OSL) measurements through experiments and numerical simulations. TR-OSL measurements of Al 2O3:C,Mg were carried out and the resulting optically stimulated luminescence (OSL) curves were investigated as a function of the temperature. The numerical simulations were carried out using the rate-equations for a simplified model of Al2O3:C,Mg containing two types of luminescence centers with different luminescence lifetimes and three types of electron traps (a shallow trap, a main dosimetric trap, and a thermally disconnected deep trap). Both experimental results and simulations show that the OSL signals during and between the stimulation pulses are affected by the presence of shallow traps. However, with an appropriate choice of timing parameters, the influence of shallow traps can be reduced by calculating the difference between the signals during and between stimulation pulses. Therefore, TR-OSL can be useful in dosimetry using materials having a large concentration of shallow traps and OSL components with short luminescence lifetimes, for example Al2O3:C,Mg and BeO. Our results also show that the presence of shallow traps has to be taken into account when using the TR-OSL for discrimination between luminescence centers with different luminescence lifetimes, or separation between the OSL from different materials based on their characteristic luminescence lifetimes. The experimental results also show evidence of thermal assistance in the OSL process of Al2O 3:C,Mg. © 2011 American Institute of Physics. Source


Osinga J.-M.,German Cancer Research Center | Osinga J.-M.,Martin Luther University of Halle Wittenberg | Akselrod M.S.,Landauer Inc. | Herrmann R.,University of Aarhus | And 6 more authors.
Radiation Measurements | Year: 2013

We present an approach to use Al2O3:C,Mg-based fluorescent nuclear track detectors (FNTDs) and confocal laser scanning microscopy as a semiautomatic tool for fluence measurements in clinical ion beams. The method was found to cover a linear energy transfer (LET) range from at least L. © 2013 Elsevier Ltd. All rights reserved. Source


Klimpki G.,German Cancer Research Center | Klimpki G.,Paul Scherrer Institute | Mescher H.,German Cancer Research Center | Akselrod M.S.,Landauer Inc. | And 3 more authors.
Physics in Medicine and Biology | Year: 2016

Due to their superior spatial resolution, small and biocompatible fluorescent nuclear track detectors (FNTDs) open up the possibility of characterizing swift heavy charged particle fields on a single track level. Permanently stored spectroscopic information such as energy deposition and particle field composition is of particular importance in heavy ion radiotherapy, since radiation quality is one of the decisive predictors for clinical outcome. Findings presented within this paper aim towards single track reconstruction and fluence-based dosimetry of proton and heavier ion fields. Three-dimensional information on individual ion trajectories through the detector volume is obtained using fully automated image processing software. Angular distributions of multidirectional fields can be measured accurately within ±2° uncertainty. This translates into less than 5% overall fluence deviation from the chosen irradiation reference. The combination of single ion tracking with an improved energy loss calibration curve based on 90 FNTD irradiations with protons as well as helium, carbon and oxygen ions enables spectroscopic analysis of a detector irradiated in Bragg peak proximity of a 270 MeV u-1 carbon ion field. Fluence-based dosimetry results agree with treatment planning software reference. © 2016 Institute of Physics and Engineering in Medicine. Source


Niklas M.,German Cancer Research Center | Abdollahi A.,German Cancer Research Center | Abdollahi A.,University of Heidelberg | Abdollahi A.,Heidelberg Ion Beam Therapy Center | And 8 more authors.
International Journal of Radiation Oncology Biology Physics | Year: 2013

Purpose To report on the spatial correlation of physical track information (fluorescent nuclear track detectors, FNTDs) and cellular DNA damage response by using a novel hybrid detector (Cell-Fit-HD). Methods and Materials The FNTDs were coated with a monolayer of human non-small cell lung carcinoma (A549) cells and irradiated with carbon ions (270.55 MeV u-1, rising flank of the Bragg peak). Phosphorylated histone variant H2AX accumulating at the irradiation-induced double-strand break site was labeled (RIF). The position and direction of ion tracks in the FNTD were registered with the location of the RIF sequence as an ion track surrogate in the cell layer. Results All RIF sequences could be related to their corresponding ion tracks, with mean deviations of 1.09 μm and -1.72 μm in position and of 2.38 in slope. The mean perpendicular between ion track and RIF sequence was 1.58 μm. The mean spacing of neighboring RIFs exhibited a regular rather than random spacing. Conclusions Cell-Fit-HD allows for unambiguous spatial correlation studies of cell damage with respect to the intracellular ion traversal under therapeutic beam conditions. © 2013 The Authors. Published by Elsevier Inc. All rights reserved. Source


Sykora G.J.,Landauer Inc. | Sykora G.J.,Oklahoma State University | Akselrod M.S.,Landauer Inc.
Radiation Measurements | Year: 2010

The latest achievements in fluorescent nuclear track detector (FNTD) technology are described. FNTDs are aluminum oxide crystals containing aggregate oxygen vacancy defects and doped with carbon and magnesium (Al 2O3:C,Mg). Unlike most nuclear track detectors, Al 2O3:C,Mg is sensitive to low linear energy transfer (LET) radiation including secondary electrons resulting from interactions of photons with the crystal. A new image processing method is investigated as a technique to discriminate and measure the doses of gamma and fast neutrons in mixed field conditions. Dose dependencies for both gamma and neutron irradiated FNTDs are shown. The new image processing method increased the dynamic range of detectable neutron doses from 4 orders of magnitude for track counting method to at least 6 orders of magnitude by combining track counting with the new image processing method. The new image processing method is combined with a detector configuration utilizing three converters: Teflon®, polyethylene, and lithium fluoride. © 2009 Elsevier Ltd. All rights reserved. Source

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