背景:新放射治疗技术的持续发展需要剂量测定系统来满足日益严格的要求,如高灵敏度,宽剂量范围,高空间分辨率。一个新兴的要求是能够以高精度和空间分辨率在三维(3D)中读出剂量。一些具有3D功能的剂量测定系统可用,但是由于各种原因,它们在临床工作流程中的应用受到限制,主要源于其化学性质。因此,正在寻找具有临床实施潜力的3D剂量测定系统。
目的:展示一种新型的基于光学刺激发光(OSL)的3D剂量测定系统的功能,该系统能够测量临床相关体积的辐射剂量。
方法:使用基于激光的读出系统来测量光子和质子传递的剂量分布,利用50×50×50$50\乘以50\乘以50$mm3$^3$YSO:Ce晶体的OSL。使用由两个相反的光子场组成的均匀治疗计划来建立晶体响应的不均匀性校正图,并证明了系统的准确性和精度。用光子治疗计划对晶体进行了额外的辐照,该计划由三个重叠的10×10$10\\times10$mm2$^2$从不同角度交付的场组成,以及由四个能量为90MeV的铅笔束组成的质子治疗计划(×2$\\times2$),115MeV,和140MeV。通过将3D分辨测量值与蒙特卡洛模拟进行比较来量化系统能力。
结果:发现系统的剂量图再现性在2%以内,包括统计和系统误差。测量结果从50×50×40$50\乘以50\\乘以40$mm3$^3$,体素体积仅为0.28×0.28×0.50$0.28\\乘以0.28\\乘以0.50$mm3$^3$。对于光子和质子辐照,发现3D分辨测量与模拟之间具有极好的一致性。
结论:证明了所设计的系统在临床相关体积内测量光子和质子笔形束的临床相关领域的能力。该系统是临床应用的有希望的候选者,并支持基于OSL的组织等效3D剂量学领域的未来研究。
BACKGROUND: The continued development of new radiotherapy techniques requires dosimetry systems that satisfy increasingly rigorous requirements, such as high sensitivity, wide dose range, and high spatial resolution. An emerging requirement is the ability to read out doses in three dimensions (3D) with high precision and spatial resolution. A few dosimetry systems with 3D capabilities are available, but their application in a clinical workflow is limited for various reasons, primarily originating from their chemical nature. The search for a 3D dosimetry system with potential for clinical implementation is thus ongoing.
OBJECTIVE: To demonstrate the capabilities of a novel optically-stimulated-luminescence (OSL)-based 3D dosimetry system capable of measuring radiation doses in clinically relevant volumes.
METHODS: A laser-based readout system was used to measure dose distributions delivered by both photons and protons, utilizing the OSL from a 50 × 50 × 50 $50\\times 50\\times 50$ mm 3 $^3$ YSO:Ce crystal. A homogeneous treatment plan consisting of two opposing photon fields was used to establish an inhomogeneity correction map of the crystal response and demonstrated the accuracy and precision of the system. The crystal was additionally irradiated with a photon treatment plan consisting of three overlapping 10 × 10 $10\\times 10$ mm 2 $^2$ fields delivered from different angles, and a proton treatment plan consisting of four pencil beams with energies 90 MeV ( × 2 $\\times 2$ ), 115 MeV, and 140 MeV. The system abilities were quantified by comparing the 3D-resolved measurements to Monte Carlo simulations.
RESULTS: The dose map reproducibility of the system was found to be within 2% including both statistical and systematic errors. The measurements yielded integrated doses from a volume of 50 × 50 × 40 $50\\times 50\\times 40$ mm 3 $^3$ with voxel volumes of just 0.28 × 0.28 × 0.50 $0.28\\times 0.28\\times 0.50$ mm 3 $^3$ . An excellent agreement between the 3D-resolved measurements and the simulations was found for both photon- and proton-irradiation.
CONCLUSIONS: The capabilities of the devised system for measuring clinically relevant fields of photons and proton pencil beams within a clinically relevant volume were demonstrated. The system poses as a promising candidate for clinical applications, and enables future research in the field of OSL-based tissue-equivalent 3D dosimetry.