MULTI-ENERGY CONE-BEAM CT RECONSTRUCTION WITH A SPATIAL SPECTRAL NONLOCAL MEANS ALGORITHM.
MULTI-ENERGY CONE-BEAM CT RECONSTRUCTION WITH A SPATIAL SPECTRAL NONLOCAL MEANS ALGORITHM.
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DOI：
10.1137/17m1123237
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发表时间：
2018
影响因子：
2.1
通讯作者：
Jia X
中科院分区：
文献类型：
--
作者：
Li B;Shen C;Chi Y;Yang M;Lou Y;Zhou L;Jia X
多能量计算机断层扫描（CT）是一种新兴的医学图像模式，在诊断和治疗方面具有许多潜在的应用。然而，高昂的系统成本和技术障碍阻碍了其进入常规临床实践。在这项研究中，我们提出了一个在 CBCT 系统上实现多能量锥形束 CT (ME-CBCT) 的框架，该系统已广泛使用并常规用于放射治疗图像引导。在我们的方法中，实现了 kVp 切换技术，该技术获取具有在多个值之间循环的 kVp 水平的 X 射线投影。对于这种基于 kVp 切换的 ME-CBCT 采集，每个能量通道的 X 射线投影只是所有采集投影的子集。这导致了采样不足的问题，给重建问题带来了挑战。我们提出了一种空间光谱非局部均值 (ssNLM) 方法来重建 ME-CBCT，该方法利用沿空间和光谱方向的图像相关性来抑制噪声和条纹伪影。为了解决不同能量通道的强度尺度差异，采用了直方图匹配方法。我们的方法与传统使用的 NLM 方法的不同之处在于，它包含了光谱维度，这有助于有效去除不同能量通道图像中不同方向出现的条纹伪影。提供了我们算法的收敛性分析。一系列全面的模拟和真实实验研究证明了我们的 ME-CBCT 方案的可行性，以及与传统的滤波反投影型 (FBP) 和 NLM 重建方法相比，能够实现卓越的图像质量。
Multi-energy computed tomography (CT) is an emerging medical image modality with a number of potential applications in diagnosis and therapy. However, high system cost and technical barriers obstruct its step into routine clinical practice. In this study, we propose a framework to realize multi-energy cone beam CT (ME-CBCT) on the CBCT system that is widely available and has been routinely used for radiotherapy image guidance. In our method, a kVp switching technique is realized, which acquires x-ray projections with kVp levels cycling through a number of values. For this kVp-switching based ME-CBCT acquisition, x-ray projections of each energy channel are only a subset of all the acquired projections. This leads to an undersampling issue, posing challenges to the reconstruction problem. We propose a spatial spectral non-local means (ssNLM) method to reconstruct ME-CBCT, which employs image correlations along both spatial and spectral directions to suppress noisy and streak artifacts. To address the intensity scale difference at different energy channels, a histogram matching method is incorporated. Our method is different from conventionally used NLM methods in that spectral dimension is included, which helps to effectively remove streak artifacts appearing at different directions in images with different energy channels. Convergence analysis of our algorithm is provided. A comprehensive set of simulation and real experimental studies demonstrate feasibility of our ME-CBCT scheme and the capability of achieving superior image quality compared to conventional filtered backprojection-type (FBP) and NLM reconstruction methods.