Quantum noise properties of CT images with anatomical textured backgrounds across reconstruction algorithms: FBP and SAFIRE
Quantum noise properties of CT images with anatomical textured backgrounds across reconstruction algorithms: FBP and SAFIRE
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DOI：
10.1118/1.4893497
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发表时间：
2014-09-01
期刊：
影响因子：
3.8
通讯作者：
Samei, Ehsan
中科院分区：
文献类型：
--
作者：
Solomon, Justin;Samei, Ehsan
目的：CT图像的量子噪声特性通常使用具有均匀背景的简单几何模型来评估。当评估非线性重建或后处理算法时，这种幻影可能是不够的。本研究的目的是设计解剖学上知情的纹理幻影，并使用幻影，以评估量子噪声属性在两个临床可用的重建算法，滤波反投影（FBP）和正弦图确认迭代reconstruction（SAFIRE）。肺部体模包括复杂的血管样结构，沿着有嵌入的结节（球形、分叶状和毛刺状）。软组织体模是基于包含低对比度病变（球形和拟人）的三维群集亮度背景设计的。使用快速成型（3D打印）技术构建体模，并与相似尺寸的均匀体模一起沿着，在Siemens SOMATOM Definition Flash CT扫描仪上成像，并使用FBP和SAFIRE重建。对于每种背景类型采集五十次重复采集，并且通过估计像素值统计来评估噪声，例如标准偏差（即，噪声幅度）、自相关和噪声功率谱。噪声平稳性也通过检查噪声幅度的空间分布进行了评估。噪声特性进行了比较，跨背景类型和两种重建algorithm.Results之间：在FBP和SAFIRE图像，噪声是全球非平稳的所有phanteries。在所有体模的FBP图像中，以及在均匀体模的SAFIRE图像中，噪声似乎是局部稳定的（在合理的小感兴趣区域内）。噪声是局部非平稳的纹理幻影与边缘像素显示更高的噪声幅度相比，在更均匀的区域像素的SAFIRE图像。对于均匀区域中的像素，与FBP相比，SAFIRE图像中的噪声幅度平均降低了60%。然而，对于边缘像素，与FBP相比，SAFIRE图像中的噪声幅度范围从高20%到低40%。肺体模的SAFIRE图像显示出具有不同噪声纹理的不同区域（即，例如，结论：对于非线性重建算法，在均匀幻影中观察到的量子噪声特性可能不代表实际患者中的量子噪声特性。在评估使用这种非线性算法的CT系统的性能时，应考虑解剖纹理。c 2014年美国医学物理学家协会。
Purpose: Quantum noise properties of CT images are generally assessed using simple geometric phantoms with uniform backgrounds. Such phantoms may be inadequate when assessing nonlinear reconstruction or postprocessing algorithms. The purpose of this study was to design anatomically informed textured phantoms and use the phantoms to assess quantum noise properties across two clinically available reconstruction algorithms, filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE).Methods: Two phantoms were designed to represent lung and soft-tissue textures. The lung phantom included intricate vessel-like structures along with embedded nodules (spherical, lobulated, and spiculated). The soft tissue phantom was designed based on a three-dimensional clustered lumpy background with included low-contrast lesions (spherical and anthropomorphic). The phantoms were built using rapid prototyping (3D printing) technology and, along with a uniform phantom of similar size, were imaged on a Siemens SOMATOM Definition Flash CT scanner and reconstructed with FBP and SAFIRE. Fifty repeated acquisitions were acquired for each background type and noise was assessed by estimating pixel-value statistics, such as standard deviation (i.e., noise magnitude), autocorrelation, and noise power spectrum. Noise stationarity was also assessed by examining the spatial distribution of noise magnitude. The noise properties were compared across background types and between the two reconstruction algorithms.Results: In FBP and SAFIRE images, noise was globally nonstationary for all phantoms. In FBP images of all phantoms, and in SAFIRE images of the uniform phantom, noise appeared to be locally stationary (within a reasonably small region of interest). Noise was locally nonstationary in SAFIRE images of the textured phantoms with edge pixels showing higher noise magnitude compared to pixels in more homogenous regions. For pixels in uniform regions, noise magnitude was reduced by an average of 60% in SAFIRE images compared to FBP. However, for edge pixels, noise magnitude ranged from 20% higher to 40% lower in SAFIRE images compared to FBP. SAFIRE images of the lung phantom exhibited distinct regions with varying noise texture (i. e., noise autocorrelation/power spectra).Conclusions: Quantum noise properties observed in uniform phantoms may not be representative of those in actual patients for nonlinear reconstruction algorithms. Anatomical texture should be considered when evaluating the performance of CT systems that use such nonlinear algorithms. c 2014 American Association of Physicists in Medicine.