Characterization of energy response for photon-counting detectors using x-ray fluorescence.
Characterization of energy response for photon-counting detectors using x-ray fluorescence.
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DOI：
10.1118/1.4900820
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发表时间：
2014-12
期刊：
影响因子：
3.8
通讯作者：
H. Ding;Hyo-Min Cho;W. Barber;J. Iwanczyk;S. Molloi
中科院分区：
文献类型：
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作者：
H. Ding;Hyo-Min Cho;W. Barber;J. Iwanczyk;S. Molloi
目的 研究使用 X 射线荧光表征硅带光子计数探测器的可行性。方法 X 射线荧光是通过使用来自带有 2 mm Al 过滤的钨阳极 X 射线管的笔形光束产生的。使用基于边缘照明硅带探测器的能量分辨光子计数探测器在与主光束方向成 90° 的位置获取光谱。源到目标和目标到探测器的距离分别约为 19 和 11 厘米。将含有银 (Ag)、碘 (I)、钡 (Ba) 和钆 (Gd) 的四种不同材料放置在直径约为 0.7 厘米的小塑料容器中，用于 X 射线荧光测量。进行线性回归分析以获得测量的荧光峰中心和已知荧光能量之间的相关性的增益和偏移值。能量分辨率和电荷共享分数也是从记录的荧光光谱的分析拟合中获得的。使用可以通过荧光校准确定的四个参数的分析模型来估计检测器响应函数。结果 所有四种目标材料的强荧光信号均通过所研究的硅条检测器的几何形状记录下来。用于探测器能量校准的所有像素的平均增益和偏移分别确定为 6.95 mV/keV 和 -66.33 mV。探测器的能量分辨率在低能量时保持在约 2.7 keV，并略有增加至 45 keV。在所研究的 20-45 keV 能量范围内，平均电荷共享分数估计为 36%。基于所提出的响应函数的模拟探测器输出与实验测量结果吻合良好。结论 使用能量分辨光子计数探测器的光谱成像系统的性能很大程度上取决于探测器的能量校准。所提出的 X 射线荧光技术提供了一种准确有效的方法来校准光子计数探测器的能量响应。
PURPOSE To investigate the feasibility of characterizing a Si strip photon-counting detector using x-ray fluorescence. METHODS X-ray fluorescence was generated by using a pencil beam from a tungsten anode x-ray tube with 2 mm Al filtration. Spectra were acquired at 90° from the primary beam direction with an energy-resolved photon-counting detector based on an edge illuminated Si strip detector. The distances from the source to target and the target to detector were approximately 19 and 11 cm, respectively. Four different materials, containing silver (Ag), iodine (I), barium (Ba), and gadolinium (Gd), were placed in small plastic containers with a diameter of approximately 0.7 cm for x-ray fluorescence measurements. Linear regression analysis was performed to derive the gain and offset values for the correlation between the measured fluorescence peak center and the known fluorescence energies. The energy resolutions and charge-sharing fractions were also obtained from analytical fittings of the recorded fluorescence spectra. An analytical model, which employed four parameters that can be determined from the fluorescence calibration, was used to estimate the detector response function. RESULTS Strong fluorescence signals of all four target materials were recorded with the investigated geometry for the Si strip detector. The average gain and offset of all pixels for detector energy calibration were determined to be 6.95 mV/keV and -66.33 mV, respectively. The detector's energy resolution remained at approximately 2.7 keV for low energies, and increased slightly at 45 keV. The average charge-sharing fraction was estimated to be 36% within the investigated energy range of 20-45 keV. The simulated detector output based on the proposed response function agreed well with the experimental measurement. CONCLUSIONS The performance of a spectral imaging system using energy-resolved photon-counting detectors is very dependent on the energy calibration of the detector. The proposed x-ray fluorescence technique offers an accurate and efficient way to calibrate the energy response of a photon-counting detector.