MicroCT with energy-resolved photon-counting detectors.
MicroCT with energy-resolved photon-counting detectors.
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DOI：
10.1088/0031-9155/56/9/011
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发表时间：
2011-05-07
影响因子：
3.5
通讯作者：
Frey EC
中科院分区：
文献类型：
--
作者：
Wang X;Meier D;Mikkelsen S;Maehlum GE;Wagenaar DJ;Tsui BM;Patt BE;Frey EC
本文的目的是研究具有能量分辨光子计数 X 射线探测器的 microCT 成像系统可以实际实现的优势。为此，我们构建并评估了基于此类探测器的原型 microCT 系统。该探测器基于碲化镉 (CdTe) 辐射传感器和专用集成电路 (ASIC) 读数装置。每个探测器像素可以同时对六个能量阈值以上的 X 射线光子进行计数，从而提供能量选择性 X 射线成像的能力。我们使用多色 X 射线辐射和具有 Ka 吸收边缘的各种过滤材料测试了系统的光谱性能。然后获取圆柱形 PMMA 模型的断层扫描图像，该模型包含填充有各种材料的孔。还将结果与使用强度积分 X 射线探测器和单能量（即非能量选择性）CT 获得的结果进行了比较。本文描述了系统的功能和性能，并提供了初步的光谱和断层扫描结果。光谱实验表明，能量分辨光子计数探测器能够测量标准 X 射线管等多色源的能谱，并解析用于成像的能量范围内存在的吸收边。然而，光谱质量因退化因素（包括有限的能量分辨率和电荷共享）引起的光谱失真而降低。我们开发了一个简单的电荷共享模型来重现这些扭曲。断层扫描实验表明，光子计数探测器中多个能量阈值的可用性使我们能够同时测量不同能量范围内的目标与背景对比度。与具有积分探测器的单能 CT 相比，此功能对于提高具有不同衰减系数能量依赖性的材料的区分特别有用。
The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with Kabsorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences.
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