16:00 〜 18:00
▲ [16p-P9-51] The LET dependence of radiophotoluminescence glass dosimeter and Al2O3 ceramic type TLD in proton beam
キーワード：radiophotoluminescence glass dosimeter, thermal luminescence dosimeter, LET dependence
[Background and purpose] Recently, the interest and the demand of dosimetry system for proton therapy increased. Many reports concerned with the feasibility of dosimeter in proton beam. The radiophotoluminescence glass dosimeter (RGD) is widely used for conventional X-ray radiotherapy because it has many advantageous such as high reproducibility, reusable, and easy to handle. Besides the RGD, it has been reported that the main glow peak of alumina based ceramics TLD (A8, Chibacera Co.) is less LET dependent compare to other commercial TLD. However, the LET quenching effect of RGD and A8 in proton beam were only clarified for the LET of 1 keV μm-1. This report was aimed at investigating the LET dependence of the relative luminescence efficiency ε for RGD and A8 for proton dosimetry.
[Materials and methods] In this work, the RGD (GD-302, Asahi techno) and A8 were calibrated using a 60Co γ-ray. The LET dependence was investigated using a 70 MeV proton beam. Setup conditions were as follows: 30 cm air gap from snout, 10 cm × 10 cm field size. Proton energies, i.e. LET, were changed using range shifter made of PMMA.
[Results and discussions] Figure 1 shows the ε for TLD and RGD as a function of LET. The ε for RGD decreases rapidly at LET range from 1 to 2 keV μm-1. On the other hand, the variation of the ε of A8 was within 5 % at LET range from 1 keV μm-1 to 4 keV μm-1. The LET for therapeutic proton beam, unmodulated and modulated proton beams, are range from 0.5 keV μm-1to 5 keV μm-1 which means that A8 is potentially usable for proton dosimetry. As a future work, the depth dose distribution will be measured using A8 to evaluate the feasibility in proton dosimetry.
[Materials and methods] In this work, the RGD (GD-302, Asahi techno) and A8 were calibrated using a 60Co γ-ray. The LET dependence was investigated using a 70 MeV proton beam. Setup conditions were as follows: 30 cm air gap from snout, 10 cm × 10 cm field size. Proton energies, i.e. LET, were changed using range shifter made of PMMA.
[Results and discussions] Figure 1 shows the ε for TLD and RGD as a function of LET. The ε for RGD decreases rapidly at LET range from 1 to 2 keV μm-1. On the other hand, the variation of the ε of A8 was within 5 % at LET range from 1 keV μm-1 to 4 keV μm-1. The LET for therapeutic proton beam, unmodulated and modulated proton beams, are range from 0.5 keV μm-1to 5 keV μm-1 which means that A8 is potentially usable for proton dosimetry. As a future work, the depth dose distribution will be measured using A8 to evaluate the feasibility in proton dosimetry.