Tilted-wire method for measuring resolution properties of CT images under extremely low-contrast and high-noise conditions.
Tilted-wire method for measuring resolution properties of CT images under extremely low-contrast and high-noise conditions.
复制标题
斜线法用于测量极低对比度和高噪声条件下 CT 图像的分辨率特性。
DOI：
10.1007/s12194-018-0443-8
复制
发表时间：
2018
影响因子：
1.6
通讯作者：
and Issei Mori
中科院分区：
文献类型：
--
作者：
Chiaki Tominaga;Hiroki Azumi;Mitsunori Goto;Masaaki Taura;Noriyasu Homma;and Issei Mori
边缘方法主要用于调制传递函数（MTF）测量的计算机断层扫描（CT）图像重建使用迭代方法。然而，边缘方法采用相对较大且明显的测试对象，旨在模拟相对较大且明显的临床器官。如果想要评估在嘈杂背景下视觉上模糊的小的低对比度对象的图像质量，则需要一个小而模糊的测试对象。另一个问题是，在MTF测量期间，与信号量相关的信息被丢弃。选择弱脉冲作为最终的小测试对象，我们开发了一种倾斜线方法，这是一种适用于极低噪比（CNR）条件的点扩展函数（PSF）方法。信号量以PSF体积来测量。我们使用两套商用CT系统来评估斜丝法的测量精度。当使用集合平均图像时，即使电线无法从噪声中分辨出来，也可以测量MTF。在这种条件下，对MTF和信号量的测量误差都只有几个百分点。我们还将斜丝法应用于AIDR-3D和ASiR两种混合迭代重建方法。结果表明，ASiR的MTF完全依赖于cnr，而AIDR-3D的MTF则依赖于噪声。用ASiR获得的信号量与通过滤波后的反投影（FBP）获得的信号量没有变化。根据噪声水平的不同，AIDR-3D获得的信号量小于FBP获得的信号量。
Edge methods are predominantly used for modulation transfer function (MTF) measurements in computed tomography (CT) images reconstructed using iterative methods. However, edge methods employ a relatively large and distinct test object, which is intended to simulate relatively large and distinct clinical organs. If one wants to assess the image quality of a small low-contrast object that is visually indistinct against a noisy background, a small and indistinct test object is desired. Another concern is that information related to the signal amount is discarded during MTF measurements. Choosing a weak impulse as the ultimately small test object, we have developed a tilted-wire method, which is a type of point spread function (PSF) method compatible with extremely low contrast-to-noise ratio (CNR) conditions. The signal amount is measured as the PSF volume. We used two commercial CT systems to evaluate the measurement accuracy of the tilted-wire method. When ensemble-averaged images are used, one can measure the MTF even when the wire is indiscernible from noise. The measurement error under such conditions is a few percent for both the MTF and signal amount. We also applied the tilted-wire method to two hybrid iterative reconstruction methods, namely AIDR-3D and ASiR. The results show that the MTF of ASiR is completely CNR-dependent, but that of AIDR-3D is noise-dependent. The signal amount obtained with ASiR is unchanged from that obtained through filtered back-projection (FBP). The signal amount obtained with AIDR-3D is less than that obtained through FBP, depending on the noise level.