Fornaro Juergen, Leschka Sebastian, Hibbeln Dennis, Butler Anthony, Anderson Nigel, Pache Gregor, Scheffel Hans, Wildermuth Simon, Alkadhi Hatem, Stolzmann Paul
Insights Imaging. 2011 Apr;2(2):149-159. doi: 10.1007/s13244-010-0057-0. Epub 2011 Jan 19.
The energy spectrum of X-ray photons after passage through an absorber contains information about its elemental composition. Thus, tissue characterisation becomes feasible provided that absorption characteristics can be measured or differentiated. Dual-energy CT uses two X-ray spectra enabling material differentiation by analysing material-dependent photo-electric and Compton effects. Elemental concentrations can thereby be determined using three-material decomposition algorithms. In comparison to dual-energy CT used in clinical practice, recently developed energy-sensitive photon-counting detectors sample the material-specific attenuation curves at multiple energy levels and within narrow energy bands; the latter allows the detection of element-specific, k-edge discontinuities of the photo-electric cross section. Multi-energy CT imaging therefore is able to concurrently identify multiple materials with increased accuracy. These specific data on material distribution provide information beyond morphological CT, and approach functional imaging. This article reviews the principles of dual- and multi-energy CT imaging, hardware approaches and clinical applications.
X射线光子穿过吸收体后的能谱包含有关其元素组成的信息。因此，只要能够测量或区分吸收特性，组织表征就变得可行。双能CT使用两个X射线谱，通过分析与材料相关的光电效应和康普顿效应来实现材料区分。由此可以使用三材料分解算法确定元素浓度。与临床实践中使用的双能CT相比，最近开发的能量敏感型光子计数探测器在多个能量水平和窄能带内对材料特异性衰减曲线进行采样；后者能够检测光电截面的元素特异性k边不连续性。因此，多能CT成像能够以更高的准确性同时识别多种材料。这些关于材料分布的特定数据提供了超越形态学CT的信息，并接近功能成像。本文综述了双能和多能CT成像的原理、硬件方法及临床应用。
