Modeling Influence Factors of Al2O3:C Optically Stimulated Luminescence Detectors (OSLDs) Exposed to Radiotherapy Beams
G O Sawakuchi1*, A. Omotayo1 and E G Yukihara2, (1) Carleton University, Ottawa, ON, (2) Oklahoma State University, Stillwater, OKSU-E-T-62 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall
Purpose: The optically stimulated luminescence (OSL) technique is becoming increasingly popular in medical dosimetry. This is partially because of the dosimetric properties of Al2O3:C, the most common commercially available OSL detector (OSLD). Currently, there is no reference dosimetry protocol based on measurements using Al2O3:C OSLDs in radiotherapy beams. Influence factors, if not properly accounted for, may introduce large systematic uncertainties in the dose measurements. In this work we develop a phenomenological model based on band structure theory that can be used to investigated the role of different influence factors on the OSL response of Al2O3:C OSLDs exposed to photon beams.
Methods: To describe the charge transportation processes that lead to the OSL response of Al2O3:C OSLDs, we used a band diagram model consisting of three electron traps (shallow, main and deep traps) and two luminescence recombination centers. Based on this model we established a system of differential equations that represent the transport of charge carriers (electrons and holes) during irradiation, relaxation and stimulation of the material. Then we solved this system of differential equations to determine the role of factors that may influence the OSL response including: irradiation temperature, time elapsed since irradiation (fading), non-linearity of the dose response, accumulated dose and resetting or bleaching method.
Results: The OSL signal: 1) depends on irradiation temperature in the temperature range relevant to medical dosimetry (15 to 40ºC); 2) fades as a function of time elapsed since irradiation. The fading is dose dependent; 3) has a non-linear dose-response, which depends on the detected OSL emission; and 4) changes as a function of accumulated dose and resetting method.
Conclusion: The proposed band diagram model may be used to understand the role of influence factors on Al2O3:C OSLDs, which will help in the development of reference dosimetry protocols based on measurements using Al2O3:C OSLDs.