Fiber-coupled radioluminescence dosimetry with saturated Al2O3:C crystals: Characterization in 6 and 18 MV photon beams
Fiber-coupled radioluminescence dosimetry with saturated Al2O3:C crystals: Characterization in 6 and 18 MV photon beams
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DOI：
10.1016/j.radmeas.2011.06.063
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发表时间：
2011-10-01
影响因子：
2
通讯作者：
Aznar, M. C.
中科院分区：
文献类型：
--
作者：
Andersen, C. E.;Damkjaer, S. M. S.;Aznar, M. C.
Radioluminescence (RL) and optically stimulated luminescence (OSL) from carbon-doped aluminum oxide crystals can be used for medical dosimetry in external beam radiotherapy and remotely afterloaded brachytherapy. The RL/OSL signals are guided from the treatment room to the readout instrumentation using optical fiber cables, and in vivo dosimetry can be carried out in real time while the dosimeter probes are in the patient. The present study proposes a new improved readout protocol based solely on the RL signal from Al2O3:C. The key elements in the protocol are that Al2O3:C is pre-dosed with similar to 20 Gy before each measurement session, and that the crystals are not perturbed by optical stimulation. Using 6 and 18 MV linear accelerator photon beams, the new RL protocol was found to have a linear dose-response from 7 mGy to 14 Gy, and dosimetry in this range could therefore be performed using a single calibration factor (similar to 6 x 10(6) counts per Gy for a 2 mg crystal). The reproducibility of the RL dosimetry was 0.3% (one relative standard deviation) for doses larger than 0.1 Gy. The apparent RI sensitivity was found to change with accumulated dose ((-0.45 +/- 0.03)% per 100 Gy), crystal temperature ((-0.21 +/- 0.01)%/ degrees C), and dose-delivery rate ((-0.22 +/- 0.01)% per 100 MU/min). A temporal gating technique was used for separation of RI and stem signals (i.e. Cerenkov light and fluorescence induced in the optical fiber cable during irradiation). The new readout protocol was a substantial improvement compared with the combined RL/OSL protocol, that required relatively long readout times and where the optical stimulation greatly affected the RI sensitivity. The only significant caveat was the apparent change in RI-response with accelerator dose-delivery rate. (C) 2011 Elsevier Ltd. All rights reserved.
