Département de Radio-Oncologie, Centre hospitalier de l'Université de Montréal (CHUM), 1560 Sherbrooke est, Montréal, Québec H2L 4M1, Canada
Med Phys. 2010 Feb;37(2):412-8. doi: 10.1118/1.3276734.
The purpose of this work was threefold: First, to determine which type of charge-coupled device (CCD) would provide the best dosimetric precision for plastic scintillation detectors (PSDs); second, to design a high-photon-efficiency PSD system by optimizing its signal-to-noise ratio (SNR) using off-the-shelf technology; and third, to establish the spatial, temporal, and dose precision limits of such a PSD system. The authors have attempted to design a dosimetric tool suitable for radiotherapy treatment modalities employing small fields or fast temporal modulation of the radiation fields, and to explore the current precision limits of PSD systems.
The authors used an SNR simulation model to design and calculate the dosimetric precision of a PSD employing a fiber taper to couple the optical fiber to the photodetector. The authors also used the SNR simulation model to evaluate the impact of the photodetector performance characteristics on the SNR and to establish the spatial, temporal, and dose precision limits.
The authors found that a high-photon-efficiency PSD can provide a precision of 1% in 45 micros of integration time for a dose rate of 400 cGy/min when a single image is taken, detect a dose of 1 cGy with a detector volume of 0.0007 mm3, and image over 15,000 detectors with a precision of 1% on a 30.7 x 30.7 mm2 CCD imaging area.
These characteristics establish that PSDs theoretically constitute a suitable dosimetric tool for radiotherapy treatment modalities employing small fields or fast temporal modulation of the radiation fields.
本研究旨在达到三个目的：首先，确定哪种电荷耦合器件（CCD）可为塑料闪烁探测器（PSD）提供最佳的剂量学精度；其次，通过优化其信噪比（SNR）来设计具有高光敏度的 PSD 系统，采用现成技术；最后，确定此类 PSD 系统的空间、时间和剂量精度极限。作者尝试设计一种适合于采用小射野或快速调制辐射场的放射治疗模式的剂量测定工具，并探索 PSD 系统的当前精度极限。
作者使用 SNR 仿真模型来设计和计算采用光纤锥形件将光纤耦合到光电探测器的 PSD 的剂量学精度。作者还使用 SNR 仿真模型来评估光电探测器性能特性对 SNR 的影响，并确定空间、时间和剂量精度极限。
作者发现，当单次拍摄时，高灵敏度 PSD 可在 45 微秒的积分时间内提供 1%的精度，在探测器体积为 0.0007mm3 的情况下检测 1cGy 的剂量，并在 30.7x30.7mm2 的 CCD 成像区域上以 1%的精度对超过 15000 个探测器进行成像，剂量率为 400cGy/min。
这些特性表明 PSD 理论上可构成适合于采用小射野或快速调制辐射场的放射治疗模式的剂量测定工具。
