The Generalized Contrast-to-Noise Ratio: A Formal Definition for Lesion Detectability.
The Generalized Contrast-to-Noise Ratio: A Formal Definition for Lesion Detectability.
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DOI：
10.1109/tuffc.2019.2956855
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发表时间：
2020-04
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影响因子：
--
通讯作者：
Torp H
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文献类型：
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作者：
Rodriguez-Molares A;Rindal OMH;D'hooge J;Masoy SE;Austeng A;Lediju Bell MA;Torp H
在过去的30年中，对比度噪声比（CNR）已被用来估计对比度和病变的超声图像的可检测性。最近的研究表明，CNR不能与现代波束形成器一起使用，因为动态范围改变可以产生任意高的CNR值，而对病变检测的概率没有真实的影响。我们推广了CNR的定义基于两个概率密度函数之间的重叠面积。这种广义对比度噪声比（gCNR）对动态范围的变化是鲁棒的;它可以应用于所有类型的图像，单位或尺度;它提供了对比度的定量测量;它有一个简单的统计解释：在分离像素的任务中，理想的观察者可以预期的成功率。我们测试gCNR的几个国家的最先进的成像算法，此外，在一个平凡的压缩的动态范围。我们观察到CNR在最先进的方法之间变化很大，改进大于100%。我们观察到，微不足道的压缩导致CNR改善超过200%。然而，所提出的索引对于压缩和未压缩的图像产生相同的值。测试方法在病变可检测性方面表现出不匹配的性能，gCNR的变化范围为-0.08至+0.29。这种新的度量方法修复了我们研究对比度的方法缺陷，并允许我们评估新成像算法的相关性。
In the last 30 years the contrast-to-noise ratio (CNR) has been used to estimate contrast and lesion detectability in ultrasound images. Recent studies have shown that the CNR can not be used with modern beamformers, as dynamic range alterations can produce arbitrarily high CNR values with no real effect on the probability of lesion detection. We generalize the definition of CNR based on the overlap area between two probability density functions. This generalized contrast-to-noise ratio (gCNR) is robust against dynamic range alterations; it can be applied to all kind of images, units, or scales; it provides a quantitative measure for contrast; and it has a simple statistical interpretation: the success rate that can be expected from an ideal observer at the task of separating pixels. We test gCNR on several state-of-the-art imaging algorithms, and, in addition, on a trivial compression of the dynamic range. We observe that CNR varies greatly between the state-of-the-art methods, with improvements larger than 100%. We observe that trivial compression leads to a CNR improvement of over 200%. The proposed index, however, yields the same value for compressed and uncompressed images. The tested methods showed mismatched performance in terms of lesion detectability, with variations in gCNR ranging from −0.08 to +0.29. This new metric fixes a methodological flaw in the way we study contrast and allows us to assess the relevance of new imaging algorithms.