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Characterization of Optically Stimulated Luminescence Dosimeter Supralinearity with Respect to Prior Dose History

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E Osunkwor

E Osunkwor1*, K Singh2 , J Seuntjens3 , S Davis4 , (1) McGill University, Montreal, QC, (2) McGill University Health Centre, Montreal, QC, (3) McGill University, Montreal, QC, (4) McGill University Health Centre, Montreal, QC


SU-K-205-4 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: 205

Purpose: To experimentally investigate and characterize the effect of dose history on the supralinear response of optically stimulated luminescence dosimeters (OSLDs) for in-vivo dosimetry.

Methods: nanoDot OSLDs were used for this work and were read with the microStar reader (Landauer, Inc., Glenwood, IL). Dose was delivered to the OSLDs in a Solid Water phantom using 6 MV photons, and was specified as dose to water at the point of measurement. Optical bleaching of the detectors was done before and after each irradiation using a simple bench fluorescent lamp. The supralinearity of the detectors was tested by irradiating nanoDots to doses from 0.1 Gy to 20 Gy that had previous irradiation histories to doses of 1 Gy to 37 Gy. The dose history represents the amount of dose the detector has accumulated throughout its irradiation/bleach cycles prior to the current irradiation. The measured dose was computed using the measured counts from the reader and a recent sensitivity calibration. The supralinearity factor for a particular dose history is simply the ratio of the measured dose to the delivered dose to water.

Results: Our results confirm the dependence of the supralinearity factor on the OSLD dose history. A correction matrix was created using quadratic polynomial fits to predict the extent of supralinearity based on the delivered dose and dose history. When tested on independent data, this correction matrix was accurate within 1.9 % and had an average accuracy of 0.2 % for doses from 0.1 Gy to 20 Gy.

Conclusion: Our work shows that a commercial OSLD system can be used to measure doses up to 20 Gy by keeping track of the dose history (up to ~40 Gy) and applying the necessary supralinearity correction.

Funding Support, Disclosures, and Conflict of Interest: E. O. acknowledges partial support by the CREATE Medical Physics Research Training Network grant of the Natural Sciences and Engineering Research Council (Grant number: 432290)

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