Temperature coefficients for in vivo RL and OSL dosimetry using Al2O3:C

A radiotherapy dosimetry system based on radioluminescence (RL) and optically stimulated luminescence (OSL) from small carbon-doped aluminum oxide (Al2O3:C) crystals attached to optical-fiber cables has been developed. To quantify the influence of temperature variations on clinical RL and OSL measurement results, we conducted an automated laboratory experiment involving threefold randomization of (1) irradiation temperature (10-45 deg. C) , (2) stimulation temperature (10-45 deg. C), and (3) irradiation dose (0-4 Gy; 50 kV X-rays). We derived linear RL and OSL temperature coefficients using a simple statistical model fitted to all data (N=909). The study shows that the temperature coefficients are independent of dose and other variables studied. In agreement with an earlier investigation, we found that the RL signal changes only with irradiation temperature whereas the OSL response changes with both irradiation temperature, stimulation temperature, and OSL integration time. Typically, the temperature coefficients are of the order of 0.2%/K, and these thermal effects are therefore large enough to be of importance for clinical measurements