Extending the clinical applications of commercially available optically stimulated luminescence (OSL) dosimeters Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/m613n087p

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  • We present the results of our experiments designed to extend the clinical applications of commercially available Optically Stimulated Luminescence (OSL) Dosimeters. Our initial experiments demonstrate the linear response of the OSL dosimeters for doses under 200 cGy and the non-linear response of the device after 200 cGy. Our experiments show the signal depletion due to the reading out of commercial OSL dosimeters is 0.05%. Extending a calibration curve beyond the range of dose measurements used to derive the curve can lead to an error in measurements greater than 10%. Our method of optically bleaching the dosimeters with a light box housing 15 W compact fluorescence lamps reduces the accumulative dose on the dosimeters by 38% of the initial dose every time the bleaching time is doubled after 10 minutes. The plausibility of the repeated use of OSL dosimeters with and without optically bleaching the devices is called into question based on the precision and accuracy seen in our next experiments. The reliability of dose measurements varies depending on whether 6 MV, 10 MV, or 18 MV photons were used to repeatedly irradiate the OSL dosimeters. However, the uncertainty in all measurements where the devices were optically bleached remains less than 2% throughout our experiment. In contrast, the uncertainty in repeated measurements for commercial OSL dosimeters when the devices were not optically bleached display an increasing uncertainty quickly surpassing 5% as increasing amounts of dose accumulates on the device. Through integration of the OSL dosimeter with the INTRABEAMTM system, we have developed a quality assurance procedure that tests deviation of the soft x-ray ionization chamber used with the system. The test can detect a deviation in an ionization chamber reading of 3.5% for the 50 kVp setting and 4.5% at the 40 kVp INTRABEAMTM setting. The OSL dosimeters are also used to determine the dose fall off of the output attenuated by a solid water phantom of varying thickness. An exponentially decreasing curve fits the dose measurements.
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  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2013-07-18T23:01:47Z (GMT) No. of bitstreams: 1 KellerJamesR2014.pdf: 28490064 bytes, checksum: 9a5c5cc2950b8b13408197468ab4d172 (MD5)
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