Medical proton dosimetry using radioluminescence from aluminium oxide crystals attached to optical-fiber cables

The prime objective of this study is to investigate if radioluminescence (RL) from carbon-doped aluminum oxide ( Al 2 O 3 : C ) crystals potentially can be used for absorbed dose-rate measurements during proton radiotherapy. The RL from two separate (2 mg) Al 2 O 3 : C crystals attached to optical-fiber cables were recorded during irradiations in water in a 175 MeV clinical proton beam. The RL response for low-LET protons in the plateau region of the Bragg curve was found to closely resemble that observed for a clinical 6 MV X-ray beam. An identical response was found in the Bragg peak (where the dose-averaged LET is about 4 keV / μ m ) for absorbed doses less than 0.3 Gy. For doses in the range of 0.3–3 Gy, we observed a significant decrease in luminescence efficiency with LET. At 3 Gy, the luminescence efficiency was about 60% in the Bragg-peak region. The study implies that the RL-signal from Al 2 O 3 : C could potentially be suitable for medical proton dosimetry in the 0–0.3 Gy range even without any LET-dependent correction factors.