A direct comparison of the optically stimulated luminescent properties of BeO and Al2O3 for clinical in-vivo dosimetry

Abstract

Optically stimulated luminescence dosimetry is a relatively recent field of in-vivo dosimetry in clinical radiotherapy, developing over the last 20 years. As a pilot study, this paper presents a direct comparison between the sensitivity variance with use, stability of measurement and linearity of the current clinical standard Al 2 O 3 :C and a potential alternative, beryllium oxide. A set of ten optically stimulated luminescence dosimeters (OSLD), including five of each type, were used simultaneously and irradiated on a Versa HD linear accelerator. Having similar sensitivity, while Al 2 O 3 :C showed a relatively stable signal response from initial use, BeO was found to have a higher response to the same dose. However, BeO displayed a strong exponential decline from initial signal response following a model of $$Respons{e}_{BeO}=(0.55\pm 0.05){e}^{-\left(0.40\pm 0.05\right)x}+(0.54\pm 0.01)$$ R e s p o n s e BeO = ( 0.55 ± 0.05 ) e - 0.40 ± 0.05 x + ( 0.54 ± 0.01 ) , reaching stability after approximately 10 irradiation cycles. BeO was shown to have potentially higher accuracy than Al 2 O 3 :C, with less variation between individual doses. Both OSLD showed good linearity between 0.2–5.0 Gy. Between these bounds, Al 2 O 3 :C demonstrated a strong linear response following the trend $$Dose_{Al_{2}O_{3}, group(adj)}=(1.00\pm 0.09)x-(0.02\pm 0.04)\,{\text{Gy}}$$ D o s e A l 2 O 3 , g r o u p ( a d j ) = ( 1.00 ± 0.09 ) x - ( 0.02 ± 0.04 ) Gy , however beyond this showed deviation from linearity, resulting in a measured dose of $$12.0\pm 0.2$$ 12.0 ± 0.2 Gy at 10.0 Gy dose delivery. BeO showed strong linearity across the full examined range of 0.2–10.0 Gy with following a model of $$Dos{e}_{BeO, ind}=(0.98\pm 0.01)x+(0.04\pm 0.01)$$ D o s e B e O , i n d = ( 0.98 ± 0.01 ) x + ( 0.04 ± 0.01 ) Gy with a recorded dose at 10.0 Gy delivery as $$9.9\pm 0.1$$ 9.9 ± 0.1 Gy. In conclusion, BeO does show large variance in sensitivity between individual OSLD and a considerable initial variance and decline in dose–response, however after pre-conditioning and individual normalisation to offset OSLD specific sensitivity BeO provides not only a viable alternative to Al 2 O 3 :C, but potentially provide higher accuracy, precision and reproducibility for in-vivo dosimetry.

Bibliographic Information