Abstract
Purpose: The objective was to determine whether optically stimulated luminescent dosimeters (OSLDs) were appropriate for in vivo measurements in high dose rate brachytherapy. In order to make this distinction, three dosimetric characteristics were tested: dose linearity, dose rate dependence, and angular dependence. The Landauer nanoDot™ OSLDs were chosen due to their popularity and their availability commercially. Methods: To test the dose linearity, each OSLD was placed at a constant location and the dwell time was varied. Next, in order to test the dose rate dependence, each OSLD was placed at different OLSD-to-source distances and the dwell time was held constant. A curved geometry was created using a circular Accuboost® applicator in order to test angular dependence. Results: The OSLD response remained linear for high doses and was independent of dose rate. For doses up to 600 cGy, the linear coefficient of determination was 0.9988 with a response of 725 counts per cGy. The angular dependence was significant only in “edge-on” scenarios. Conclusion: OSLDs are conveniently read out using commercially available readers. OSLDs can be re-read and serve as a permanent record for clinical records or be annealed using conventional fluorescent light. Lastly, OSLDs are produced commercially for $5 each. Due to these convenient features, in conjunction with the dosimetric performance, OSLDs should be considered a clinically feasible and attractive tool for in vivo HDR brachytherapy measurements.
Highlights
Stimulated luminescence (OSL) is light emission from previously irradiated crystalline materials when stimulated by a light of different wavelength
Previous studies have stated that optically stimulated luminescent dosimeters (OSLDs) possess a supralinear relationship between dose and counts above 200 cGy
This work is the first investigation of the use of OSLDs explicitly using HDR sources: testing dose linearity, dose rate capabilities, and angular response
Summary
Stimulated luminescence (OSL) is light emission from previously irradiated crystalline materials when stimulated by a light of different wavelength. In OSL materials, crystal-lattice imperfections are introduced to trap electrons, which are liberated by ionizing radiation (Akselrod et al, 1990; Akselrod et al, 1999; Yukihara and McKeever, 2008). The materials used for OSL are essentially the same as the more well-known thermoluminescent dosimeters (TLDs), optically stimulated luminescent dosimeters (OSLDs) are stimulated using light while TLDs are stimulated using heat (McKeever and Moscovitch, 2003). The most common OSL dosimeter material – carbon-doped aluminum oxide (Al2O3:C) – was originally introduced as a TLD (Akselrod et al, 1990; Yukihara and McKeever, 2008). As an OSLD, aluminum oxide is capable of detecting absorbed dose greater than 105 Gy, with negligible temperature dependence
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