SU-FF-T-225: Evaluation of Optically Stimulated Luminescence (OSL) Dosimetry for High-Energy Photon and Electron Beam Measurements in Radiotherapy

Abstract

Purpose: The precision and accuracy of the Optically Stimulated Luminescence(OSL) for determination of absorbed doses delivered by photon and electron beams from linear accelerator was investigated. The dependence of the OSLdose measurements with variations in temperature, field size,dose rate, and energy of the beam was also investigated. This study complements previous investigation on 6MV photons which showed that the OSL technique can provide dose estimates with a precision of 0.7% for a single measurement (1 dosimeter).Method and Materials:OSLdoses were obtained for various depths in a water phantom for photons (6 and 18 MV) and electrons (6 to 20 MeV) and compared to data obtained from ionization chamber. Al2O3:C OSLdosimeters (7mm diameter by 0.3mm thickness) were irradiated using a linear accelerator (Varian 21 EX S/N 2833) at SSD = 100 cm. The OSL measurements were carried out using a Riso TL/OSL‐DA‐15 reader with green light stimulation and using a readout procedure that eliminates dependences on the mass or sensitivity of the dosimeter.Results: Depth‐dose profile for 6 MV photon showed a high precision (0.5%) and accuracy, the difference between the OSLdose and the ionization chamber data being smaller than ±1.1% in all cases. The OSL measurements appear to be independent from variations in temperature, field size, and dose rate, with differences smaller than 1% compared to ionization chamber data for the 6MV photonbeam. The data for the 18 MV photonbeam and the electron beams are still being analyzed and will be presented. Conclusion: The results demonstrate that the OSL of Al2O3:C (dosimeters) provides reliable high‐precision and accurate dose estimates, with no dependence on temperature, field size, or dose rate. The OSL technique with automated readers offers a simple and effortless method, since no precise control of mass of dosimeter is required.