Despite their advantages, two-dimensional (2D) thermoluminescence dosimeters (TLDs) have not yet replaced film dosimeters owing to their nonuniformity and low repeatability. A 2D TLD based on Al 2 O 3 :Cr ceramics is a promising new reusable passive dosimeter. 2D Al 2 O 3 :Cr TLDs can be used for geometry check tests and dose distribution verification in robotic radiosurgery using monoenergetic X-ray beams. In this work, the dependence of energy on the field size and water depth of 2D Al 2 O 3 :Cr TLDs for 4, 6, and 10 MV X-ray beams was investigated, because multienergy X-ray beams are used in radiotherapy. Intensity-modulated radiotherapy plan verifications were performed using the TLDs. The TLDs were found to have a large field size dependence for each energy, but their water depth dependence was small at a water depth above 4 cm for each energy. The relative dose distributions were verified with high accuracy using the TLDs.

In the neutron irradiation field in boron neutron capture therapy, neutron rays and γ-rays are mixed, and it is not easy to selectively measure only neutron rays. The currently used gold activation method is expensive and not suitable for measuring the dose distribution with high spatial resolution. Therefore, there is increasing demand for a simple neutron measurement method for periodic inspections and treatment planning in boron neutron capture therapy (BNCT). Cd has a large nuclear reaction cross section solely for thermal neutrons, and converts thermal neutrons to γ-rays by the (n, γ) reaction. Therefore, in this study, we investigated a method for calculating the thermal neutron fluence by installing Cd as a neutron converter on Cr-doped Al 2 O 3 (Al 2 O 3 :Cr), which is a thermoluminescence dosimeter, and measuring the converted γ-ray dose with the Al 2 O 3 :Cr. After a 30 min irradiation experiment using the Kyoto University research reactor, the amount of thermoluminescence (TL) increased 101-fold after installing a Cd converter compared with the case of no Cd converter. In addition, the dependence of the TL response on the irradiation time showed excellent proportionality, suggesting the possibility of selectively measuring only the thermal neutron fluence.

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Boron neutron capture therapy (BNCT) is an innovative cancer therapy that selectively destroys only cancer cells by utilizing the reaction between boron agents, which selectively accumulate in cancer cells, and neutron beams. However, the irradiation field of BNCT is a mixture of multiple radiation types, making accurate dose evaluation difficult. For dose evaluation in cancer tissues, which is particularly important, it is essential to discriminate neutrons and γ-rays mixed in the BNCT irradiation field and to measure them correctly. In this paper, we introduce a new method for selective measurement of neutrons and γ-rays using thermoluminescence phosphor, which is expected to be a promising method to improve the accuracy of dose evaluations.