Hsieh Scott S, Pelc Norbert J
Stanford University, Department of Radiology, 1201 Welch Road, Stanford, California 94305, United States; Stanford University, Department of Electrical Engineering, 350 Serra Mall, Stanford, California 94305, United States.
Stanford University, Department of Radiology, 1201 Welch Road, Stanford, California 94305, United States; Stanford University, Department of Bioengineering, 443 Via Ortega, Stanford, California 94305, United States.
J Med Imaging (Bellingham). 2016 Apr;3(2):023505. doi: 10.1117/1.JMI.3.2.023505. Epub 2016 Jun 1.
Energy-discriminating, photon-counting (EDPC) detectors are attractive for their potential for improved detective quantum efficiency and for their spectral imaging capabilities. However, at high count rates, counts are lost, the detected spectrum is distorted, and the advantages of EDPC detectors disappear. Existing EDPC detectors identify counts by analyzing the signal with a bank of comparators. We explored alternative methods for pulse detection for multibin EDPC detectors that could improve performance at high count rates. The detector signal was simulated in a Monte Carlo fashion assuming a bipolar shape and analyzed using several methods, including the conventional bank of comparators. For example, one method recorded the peak energy of the pulse along with the width (temporal extent) of the pulse. The Cramer-Rao lower bound of the variance of basis material estimates was numerically found for each method. At high count rates, the variance in water material (bone canceled) measurements could be reduced by as much as an order of magnitude. Improvements in virtual monoenergetic images were modest. We conclude that stochastic noise in spectral imaging tasks could be reduced if alternative methods for pulse detection were utilized.
能量分辨光子计数（EDPC）探测器因其在提高探测量子效率方面的潜力及其光谱成像能力而备受关注。然而，在高计数率下，会出现计数丢失、检测光谱失真的情况，EDPC探测器的优势也会消失。现有的EDPC探测器通过一组比较器分析信号来识别计数。我们探索了用于多通道EDPC探测器的脉冲检测替代方法，这些方法可以在高计数率下提高性能。假设信号为双极形状，以蒙特卡洛方式模拟探测器信号，并使用多种方法进行分析，包括传统的比较器组。例如，一种方法记录脉冲的峰值能量以及脉冲宽度（时间范围）。通过数值计算得出了每种方法的基础材料估计方差的克拉美罗下界。在高计数率下，水材料（去除骨骼）测量中的方差可降低多达一个数量级。虚拟单能图像的改善幅度不大。我们得出结论，如果采用脉冲检测替代方法，光谱成像任务中的随机噪声可能会降低。
