Applicability of two-dimensional thermoluminescence slab dosimeter based on Al2O3:Cr for the quality assurance of robotic radiosurgery

Two-dimensional (2-D) thermoluminescence (TL) slab dosimeters based on Al2O3:Cr have been recently developed. They have high solidity, spatial resolution, repeatability and linearity, and they can be immersed in water. In the present work, their clinical applicability for quality assurance (QA) testing of the CyberKnife® robotic radiosurgery system was investigated. Those TL slabs were irradiated with 6 MV X-rays and were read out using a 2-D TL reader equipped with a large hot plate and a complementary metal-oxide-semiconductor (CMOS) camera. A comparison was made with the results obtained using radiochromic films (RCFs), which are typically used as 2-D dosimeters. It was found that those TL slabs provided sufficient precision for geometric QA tests and dose-distribution verification. Although the energy dependence for Al2O3:Cr TL slabs was larger than that for tissue-equivalent thermoluminescence dosimeters (TLDs), this had little effect in robotic radiosurgery. Thus, the results demonstrated that those TL slabs can act as replacements for RCFs for QA of robotic radiosurgery.