A data-efficient method for local noise power spectrum (NPS) estimation in FDK-reconstructed 3D cone-beam CT.
A data-efficient method for local noise power spectrum (NPS) estimation in FDK-reconstructed 3D cone-beam CT.
复制标题
FDK 重建 3D 锥束 CT 中局部噪声功率谱 (NPS) 估计的数据高效方法。
DOI：
10.1002/mp.13428
复制
发表时间：
2019
期刊：
影响因子：
3.8
通讯作者：
Myers,KyleJ
中科院分区：
文献类型：
--
作者：
Zeng,Rongping;Torkaman,Mahsa;Ning,Holly;Zhuge,Ying;Miller,Robert;Myers,KyleJ
对于噪声非平稳的CT系统，通常需要一个局部噪声功率谱来表征其噪声特性。我们之前已经开发了一种数据高效的径向投影方法，利用CT投影的极可分性来估计滤波反投影（FBP）重建扇束CT的二维（2D）局部投影。在这项工作中，我们将这种方法扩展到估计三维（3D）局部极化CBCT（CBCT）容积的FDK重建。方法从二维极可分性出发，我们分析了CBCT的几何结构和FDK图像重建过程，推导出CBCT局部极化的3D表达的极可分性。利用极可分性，CBCT的3D局部振幅可以通过一定的几何变换分解为2D径向振幅形状函数和一维（1D）角振幅函数。2D径向波形函数是表征噪声相关结构的全局函数，而1D角幅度函数是反映变化的局部噪声幅度的局部函数。利用极可分性构造了三维径向局部插值方法。我们使用模拟和真实的CBCT数据，通过将径向局部局部平均估计值与参考局部平均估计值在归一化均方误差（NMSE）和基于任务的性能度量方面进行比较，来评估3D径向局部平均方法的准确性。结果在模拟和物理CBCT实例中，通过径向局部增强方法从少至两次扫描实现了非常小的NMSE（<5%），而对于传统的局部扫描方法，需要大约20次扫描才能达到该精度。结果还表明，基于可检测性的系统性能计算使用的本地可检测性估计的方法，在这项工作中开发的两次扫描密切反映了实际的系统performance.ConclusionsThe极可分性大大降低了三维CBCT本地可检测性的数据维数。基于此属性开发的径向局部扩散方法被证明能够从仅两个CBCT扫描以可接受的精度估计3D局部扩散。最低数据要求表明，即使在临床情况下，CBCT应用程序中的本地可重复性的潜在效用。
PurposeFor computed tomography (CT) systems in which noise is nonstationary, a local noise power spectrum (NPS) is often needed to characterize its noise property. We have previously developed a data‐efficient radial NPS method to estimate the two‐dimensional (2D) local NPS for filtered back projection (FBP)‐reconstructed fan‐beam CT utilizing the polar separability of CT NPS. In this work, we extend this method to estimate three‐dimensional (3D) local NPS for feldkamp‐davis‐kress (FDK)‐reconstructed cone‐beam CT (CBCT) volumes.MethodsStarting from the 2D polar separability, we analyze the CBCT geometry and FDK image reconstruction process to derive the 3D expression of the polar separability for CBCT local NPS. With the polar separability, the 3D local NPS of CBCT can be decomposed into a 2D radial NPS shape function and a one‐dimensional (1D) angular amplitude function with certain geometrical transforms. The 2D radial NPS shape function is a global function characterizing the noise correlation structure, while the 1D angular amplitude function is a local function reflecting the varying local noise amplitudes. The 3D radial local NPS method is constructed from the polar separability. We evaluate the accuracy of the 3D radial local NPS method using simulated and real CBCT data by comparing the radial local NPS estimates to a reference local NPS in terms of normalized mean squared error (NMSE) and a task‐based performance metric (lesion detectability).ResultsIn both simulated and physical CBCT examples, a very small NMSE (<5%) was achieved by the radial local NPS method from as few as two scans, while for the traditional local NPS method, about 20 scans were needed to reach this accuracy. The results also showed that the detectability‐based system performances computed using the local NPS estimated with the NPS method developed in this work from two scans closely reflected the actual system performance.ConclusionsThe polar separability greatly reduces the data dimensionality of the 3D CBCT local NPS. The radial local NPS method developed based on this property is shown to be capable of estimating the 3D local NPS from only two CBCT scans with acceptable accuracy. The minimum data requirement indicates the potential utility of local NPS in CBCT applications even for clinical situations.