SANKEN, Osaka University. 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
RIKEN Nishina Center for Accelerator-Based Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Biomed Phys Eng Express. 2024 Oct 29;10(6). doi: 10.1088/2057-1976/ad81fd.
The importance of real-time dose evaluation has increased for recent advanced radiotherapy. However, conventional methods for real-time dosimetry using gel dosimeters face challenges owing to the delayed dose response caused by the slow completion of radiation-induced chemical reactions. In this study, a novel technique called photoluminescence-detected pulse radiolysis (PLPR) was developed, and its potential to allow real-time dose measurements using nano-clay radio-fluorogenic gel (NC-RFG) dosimeters was investigated. PLPR is a time-resolved observation method, and enables time-resolved fluorescence measurement. NC-RFG dosimeters were prepared, typically consisting of 100 μM dihydrorhodamine 123 (DHR123) and 2.0 wt.% nano-clay, along with catalytic and dissolving additives. We successfully achieved time-resolved observation of the increase in fluorescence intensity upon irradiation of the dosimeter. Dose evaluation was possible at 1 s after irradiation. The dose-rate effect was not observed for the deoxygenated dosimeter, but was observed for the aerated dosimeter. Besides the dose-rate effect, linear dose responses were obtained for both conditions. Furthermore, we made a novel observation of a decay in the fluorescence intensity over time in the early stages which named fluorescence secondary loss (FSL) and elucidated the conditions under which this phenomenon occurs.
实时剂量评估对于最近的先进放疗变得越来越重要。然而，由于辐射诱导化学反应的缓慢完成导致的剂量响应延迟，使用凝胶剂量计进行实时剂量测定的传统方法面临挑战。在这项研究中，开发了一种称为光致发光探测脉冲辐解（PLPR）的新技术，并研究了其使用纳米粘土放射性荧光凝胶（NC-RFG）剂量计进行实时剂量测量的潜力。PLPR 是一种时间分辨观察方法，能够实现时间分辨荧光测量。NC-RFG 剂量计通常由 100 μM 二氢罗丹明 123（DHR123）和 2.0wt%纳米粘土以及催化和溶解添加剂组成。我们成功地实现了对剂量计辐照后荧光强度增加的时间分辨观察。辐照后 1 秒即可进行剂量评估。对于去氧剂量计，未观察到剂量率效应，但对于充气剂量计，观察到了剂量率效应。除了剂量率效应之外，两种情况下均获得了线性剂量响应。此外，我们还观察到了一个新的现象，即在早期阶段荧光强度随时间的衰减，称为荧光二次损失（FSL），并阐明了这种现象发生的条件。
