Sensitivity of photon-counting K-edge imaging: Dependence on atomic number and object size
Sensitivity of photon-counting K-edge imaging: Dependence on atomic number and object size
复制标题
光子计数 K 边缘成像的灵敏度：取决于原子序数和物体尺寸
DOI：
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
R. Proksa
中科院分区：
文献类型：
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作者：
E. Roessl;B. Brendel;Jens;A. Thran;R. Proksa
K-边缘X射线CT成像的可行性已被证明通过模拟和能量分辨，光子计数数据上进行的实验。该方法是基于检测的衰减与能量敏感，光子计数装置测量的高原子序数Z的元素的K边缘以上和以下的差异。到目前为止，这种技术的敏感性只在少数情况下进行了探索。在本文中，我们彻底调查的K-边缘成像的原子序数Z的对比材料，对象的大小D和X射线探测器的光谱响应函数的灵敏度的依赖关系。我们假设光子计数探测器配备有6个可调的能量阈值。使用光谱响应函数R（E，U）的概念考虑导致探测器的能量分辨率退化的各种物理效应，对于光谱响应函数R（E，U），我们假设四种不同的模型：无限能量分辨率，10 keV FWHM的平移不变高斯响应，（测量的）位移不变能量响应，其特征在于光峰值和K逃逸峰值，以及最后，来自同步加速器处的检测器校准的实验确定的响应函数。通过相对于阈值优化可实现的信号来考虑对能量阈值的值的依赖性。我们发现，对于一个给定的X射线光谱，存在一个原子序数Z的信号噪声比（SNR）在高Z基材料图像是最大的。SNR对对象厚度的依赖性是指数下降，在对象本身的射束硬化导致K边缘以下的信号损失的情况下，具有特别恶化的效果。检测器的能量响应的影响非常强，并且对于具有朝向较低能量的拖尾的响应而增加。
The feasibility of K-edge x-ray CT imaging has been demonstrated both by simulations and by experiments performed on energy-resolved, photon-counting data. The method is based on detecting the difference in attenuation above and below the K-edge of elements with high atomic number Z measured with energy-sensitive, photon counting devices. So far, the sensitivity of this technique has been probed only for a handful of scenarios. In this paper, we thoroughly investigate the dependence of the sensitivity of K- edge imaging on the atomic number Z of the contrast material, on the object size D and on the spectral response function of the x-ray detector. We assume a photon-counting detector equipped with 6 adjustable energy thresholds. The various physical effects leading to a degradation of the energy resolution of the detector are taken into account using the concept of a spectral response function R(E, U) for which we assume four different models: infinite energy resolution, a shift-invariant Gaussian response with 10 keV FWHM, a (measured) shift-invariant energy response featuring a photo-peak and a K- escape peak and, finally, an experimentally determined response function from a detector calibration at the synchrotron. The dependence on the values of the energy thresholds is taken into account by optimizing the achievable signal with respect to the threshold values. We find that for a given x-ray spectrum there exists an atomic number Z for which the signal-to-noise ratio (SNR) in the high-Z basis material image is maximal. The SNR dependence on the object thickness is an exponential decrease with particularly deteriorating effects in the case where the beam-hardening from the object itself causes a signal loss below the K-edge. The influence of the energy-response of the detector is very strong and increases for responses with tailing towards lower energies.
影响因子：
3.8
作者：
TUCKER, DM;BARNES, GT;CHAKRABORTY, DP
通讯作者：
CHAKRABORTY, DP