Estimation of the noisy component of anatomical backgrounds
Estimation of the noisy component of anatomical backgrounds
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DOI：
10.1118/1.598632
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发表时间：
1999-07-01
期刊：
影响因子：
3.8
通讯作者：
Schnyder, P
中科院分区：
文献类型：
--
作者：
Bochud, FO;Valley, JF;Schnyder, P
了解辐射剂量与图像质量之间的关系是优化医学诊断放射学的先决条件。图像质量一方面取决于对比度、分辨率和噪声等物理参数，另一方面取决于评估图像的观察者的特征。虽然对比度和分辨率的作用被精确地定义和识别，但图像噪声的影响尚未完全理解。其测量通常基于成像均匀的测试对象，即使真实的图像包含解剖背景，其统计性质与用于评估系统噪声的测试对象大不相同。本研究的目的是通过量化其对一系列检测任务的影响来证明背景解剖结构变化的重要性。几种类型的乳腺摄影背景和信号进行了检查的心理物理实验中的两个选择强制选择检测任务。根据人类观察者所使用的策略的假设，确定其信噪比。这个变量也计算了一个基于统计决策理论的数学模型。通过理论模型和实验结果的对比，分析了解剖结构的感知方式。实验表明，观察者的行为高度依赖于系统噪声和解剖背景。解剖结构部分地作为可识别的信号，部分地作为干扰检测过程的纯噪声。解剖结构的这种双重性质被量化。它示出，其效果根据其幅度和被检测的对象的轮廓而变化。在某些情况下，解剖结构的噪声部分的重要性远远大于系统噪声。因此，通过增加剂量来降低系统噪声不会改善任务性能。这一观察结果表明，剂量和图像质量之间的权衡可能会通过接受更高的系统噪声来优化。这可能导致更好的分辨率、更高的对比度或更少的剂量。(C)1999年美国医学物理学家协会。[S0094-2405（99）01807-6]。
The knowledge of the relationship that links radiation dose and image quality is a prerequisite to any optimization of medical diagnostic radiology. Image quality depends, on the one hand, on the physical parameters such as contrast, resolution, and noise, and on the other hand, on characteristics of the observer that assesses the image. While the role of contrast and resolution is precisely defined and recognized, the influence of image noise is not yet fully understood. Its measurement is often based on imaging uniform test objects, even though real images contain anatomical backgrounds whose statistical nature is much different from test objects used to assess system noise. The goal of this study was to demonstrate the importance of variations in background anatomy by quantifying its effect on a series of detection tasks. Several types of mammographic backgrounds and signals were examined by psychophysical experiments in a two-alternative forced-choice detection task. According to hypotheses concerning the strategy used by the human observers, their signal to noise ratio was determined. This variable was also computed for a mathematical model based on the statistical decision theory. By comparing theoretical model and experimental results, the way that anatomical structure is perceived has been analyzed. Experiments showed that the observer's behavior was highly dependent upon both system noise and the anatomical background. The anatomy partly acts as a signal recognizable as such and partly as a pure noise that disturbs the detection process. This dual nature of the anatomy is quantified. It is shown that its effect varies according to its amplitude and the profile of the object being detected. The importance of the noisy part of the anatomy is, in some situations, much greater than the system noise. Hence, reducing the system noise by increasing the dose will not improve task performance. This observation indicates that the tradeoff between dose and image quality might be optimized by accepting a higher system noise. This could lead to a better resolution, more contrast, or less dose. (C) 1999 American Association of Physicists in Medicine. [S0094-2405(99)01807-6].