Salehjahromi Morteza, Zhang Yanbo, Yu Hengyong
Department of Electrical and Computer Engineering, University of Massachusetts Lowell, Lowell, MA 01854, USA.
Sens Imaging. 2018;19(1). doi: 10.1007/s11220-018-0200-4. Epub 2018 Mar 27.
The energy-resolving photon-counting detectors in spectral computed tomography (CT) can acquire projections of an object in different energy channels. In other words, they are able to reliably distinguish the received photon energies. These detectors lead to the emerging spectral CT, which is also called multi-energy CT, energy-selective CT, color CT, etc. Spectral CT can provide additional information in comparison with the conventional CT in which energy integrating detectors are used to acquire polychromatic projections of an object being investigated. The measurements obtained by X-ray CT detectors are noisy in reality, especially in spectral CT where the photon number is low in each energy channel. Therefore, some regularization should be applied to obtain a better image quality for this ill-posed problem in spectral CT image reconstruction. Quadratic-based regularizations are not often satisfactory as they blur the edges in the reconstructed images. As a result, different edge-preserving regularization methods have been adopted for reconstructing high quality images in the last decade. In this work, we numerically evaluate the performance of different regularizers in spectral CT, including total variation, non-local means and anisotropic diffusion. The goal is to provide some practical guidance to accurately reconstruct the attenuation distribution in each energy channel of the spectral CT data.
光谱计算机断层扫描（CT）中的能量分辨光子计数探测器能够在不同能量通道中获取物体的投影。换句话说，它们能够可靠地分辨接收到的光子能量。这些探测器催生了新兴的光谱CT，也被称为多能量CT、能量选择性CT、彩色CT等。与传统CT相比，光谱CT能够提供额外信息，传统CT使用能量积分探测器来获取被研究物体的多色投影。实际上，X射线CT探测器获得的测量数据存在噪声，尤其是在光谱CT中，每个能量通道中的光子数量较少。因此，在光谱CT图像重建中，针对这个不适定问题需要应用一些正则化方法来获得更好的图像质量。基于二次的正则化方法通常并不令人满意，因为它们会模糊重建图像中的边缘。因此，在过去十年中，人们采用了不同的边缘保留正则化方法来重建高质量图像。在这项工作中，我们对光谱CT中不同正则化器的性能进行了数值评估，包括总变差、非局部均值和各向异性扩散。目的是为准确重建光谱CT数据每个能量通道中的衰减分布提供一些实用指导。
