Characterization of a Commercial Optically Stimulated Luminescence Dosimetry System
There is a need to better understand the risks of low level radiation dose in medical diagnostic procedures and ensure that dose measurements are accurate and traceable to National Standards. Users of instruments typically calibrate their dosimeters with one type of radiation beam with a specific photon energy spectrum (referred to as beam quality) and then may use these dosimeters to measure radiation in other types of radiation beam qualities over a different range of photon energies. This is not a problem if the dosimeter response is relatively constant for a broad range of photon energies. However, the response of the optically stimulated luminescent (OSL) dosimeters studied in this work have a relatively strong energy dependence for photons with energies less than 100 keV. Moreover, since this work focused on measuring doses in diagnostic units only, where the mean photon energies are below 100 keV, using a single calibration based on an 80 kVp beam quality as provided by the vendor of the system could result in inaccurate dose measurements. To address this hypothesis, as part of this work, the system was calibrated independently using other beam qualities that better match those of diagnostic units including: RQR50, RQR60, M60, M80 and M100 (Lamperti & O'Brien, 2001), available at the National Institute of Standards and Technology (NIST). A comparison was then made of the air kerma measured by the OSL system using both the vendor’s OSL reader calibration and the independent calibration implemented in this work. This comparison shows that when measuring air kerma in x-ray beams with beam qualities that have energy spectra different than the energy spectra of the x-ray beam in which the vendor prepared their calibration set (80 kVp x-ray beam), significant differences of up to 20% are observed. Because of this comparison, a set of beam quality correction factors (BQCF) were developed that allows correcting the air kerma values measured with the vendor’s calibrated OSL system, to account for the differences in energy spectra in the air kerma measurement for different beam qualities and ensuring traceability to the national standard for air kerma.
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Arrow, Kenneth; Auerbach, Alan; Bertko, John; Brownlee, Shannon; Casalino, Lawrence P.; Cooper, Jim; Crosson, Francis J.; Enthoven, Alain; Falcone, Elizabeth; Feldman, Robert C.; Fuchs, Victor R.; Garber, Alan M.; Gold, Marthe R.; Goldman, Dana; Hadfield, Gillian K.; Hall, Mark A.; Horwitz, Ralph I.; Hooven, Michael; Jacobson, Peter D.; Jost, Timothy Stoltzfus; Kotlikoff, Lawrence J.; Levin, Jonathan; Levine, Sharon; Levy, Richard; Linscott, Karen; Luft, Harold S.; Mashal, Robert; McFadden, Daniel; Mechanic, David; Meltzer, David; Newhouse, Joseph P.; Noll, Roger G.; Pietzsch, Jan B.; Pizzo, Philip; Reischauer, Robert D.; Rosenbaum, Sara; Sage, William; Schaeffer, Leonard D.; Sheen, Edward; Silber, B. Michael; Skinner, Jonathan; Shortell, Stephen M.; Thier, Samuel O.; Tunis, Sean; Wulsin, Lucien Jr.; Yock, Paul; Nun, Gabi Bin; Bryan, Stirling; Luxenburg, Osnat; van de Ven, Wynand P.M.M. (2009-04-07)