Lessard F, Archambault L, Plamondon M, Després P, Therriault-Proulx F, Beddar S, Beaulieu L
Département de physique, de génie physique et d'optique, Université Laval, Québec, QC, Canada and Département de radio-oncologie, Hôtel-Dieu de Québec, Centre hospitalier universitaire de Québec, Québec, QC, Canada.
Department of Radiation Physics, Unit 94, The University of Texas MD Anderson Cancer Center, Houston, Texas.
Med Phys. 2012 Jul;39(7Part4):4646. doi: 10.1118/1.4740214.
To characterize the plastic scintillation detectors (PSDs) response in the diagnostic energy range. A fast and adaptable method for real-time dosimetry in superficial x-ray therapy and interventional radiology is proposed.
A PSD (1 mm diameter and 10 mm long) is coupled to a 5 m long optical fiber. Scintillation photons are guided to a polychromatic photodiode which provides an electrical current proportional to the input light signal. If the incident energy spectrum is known, the dose measured in the PSD's polystyrene sensitive volume can be converted to score dose in any other media such as air, water or soft tissues using the large cavity theory (LCT). A software simulating x-ray tube spectra and filtration has been benchmarked and is used for analysis. The method is confirmed by Monte Carlo simulations.
PSDs cannot be assumed energy independent with low-energy photons as a factor 2 has been observed in the energy response between 80 kVp and 150 kVp. When the dose is converted to the desired medium, the PSD's energy dependence is compensated and a 2.1% standard deviation was observed upon the studied energy ranges, which is inside the measurement and calculation uncertainties. Percent depth dose (PDD) measurements are in good agreement with Monte Carlo simulations and results can be improved if the proposed method is applied to compensate beam hardening.
PSDs present great potential for real-time dose measurements with radiologic photon energy.
表征塑料闪烁探测器（PSD）在诊断能量范围内的响应。提出一种用于浅表X射线治疗和介入放射学实时剂量测定的快速且适应性强的方法。
将一个PSD（直径1毫米，长10毫米）与一根5米长的光纤耦合。闪烁光子被引导至一个多色光电二极管，该二极管提供与输入光信号成比例的电流。如果入射能谱已知，利用大腔理论（LCT），在PSD的聚苯乙烯灵敏体积中测量的剂量可转换为在任何其他介质（如空气、水或软组织）中的计分剂量。一个模拟X射线管能谱和过滤的软件已经经过基准测试并用于分析。该方法通过蒙特卡罗模拟得到证实。
对于低能光子，不能认为PSD与能量无关，因为在80 kVp至150 kVp的能量响应中观察到了2倍的差异。当剂量转换到所需介质时，PSD的能量依赖性得到补偿，在研究的能量范围内观察到2.1%的标准偏差，这在测量和计算不确定度范围内。百分深度剂量（PDD）测量结果与蒙特卡罗模拟结果吻合良好，如果应用所提出的方法来补偿束硬化，结果可以得到改善。
PSD在放射光子能量实时剂量测量方面具有巨大潜力。
