Lopez H, Loew M H, Butler P F, Hill M C, Allman R M
U.S. Department of Health and Human Services, Center for Devices and Radiological Health, Rockville, Maryland 20857.
Med Phys. 1990 Jan-Feb;17(1):48-57. doi: 10.1118/1.596527.
We report on the reproducibility of human observers' vanishing detection thresholds for visual targets in contrast-detail (C/D) analysis of ultrasound B-mode images. The images used in this study contain visual targets which are circular cross sections of constant-contrast conical structures in the C/D phantom. The vanishing threshold diameters for these targets vary as a function of the perceived size of the imaged target, target-to-background contrast, image noise content, and reproducibility of the decision levels of human observers for repeated observations. Our study indicates that the determination of absolute vanishing threshold diameter values for several targets of different contrast by human observers yields a high degree of error that is not predicted by existing theoretical assumptions based on a static threshold detector. We find that systematic error is introduced by the observers during the course of the experiment and that the levels of sensitivity of the observers differ widely at all times, and increase the amount of total observer error. These results suggest that, due to the large total observer error, C/D analysis may be impractical in a clinical environment, unless there is access to a team of observers specifically and extensively trained in this task. We suggest that a computer-based observer may be more reliable for the objective performance of contrast-detail analysis as a method for evaluating ultrasound image quality and comparison of imaging systems.
我们报告了在超声B模式图像的对比度-细节（C/D）分析中，人类观察者对视觉目标的消失检测阈值的可重复性。本研究中使用的图像包含视觉目标，这些目标是C/D体模中恒定对比度锥形结构的圆形横截面。这些目标的消失阈值直径随成像目标的感知大小、目标与背景的对比度、图像噪声含量以及人类观察者对重复观察的决策水平的可重复性而变化。我们的研究表明，人类观察者对几个不同对比度目标的绝对消失阈值直径值的测定会产生高度误差，而基于静态阈值检测器的现有理论假设无法预测这种误差。我们发现，在实验过程中观察者引入了系统误差，并且观察者的敏感度水平在任何时候都有很大差异，这增加了观察者总误差的量。这些结果表明，由于观察者总误差较大，除非有一组专门且经过广泛培训以执行此任务的观察者，否则C/D分析在临床环境中可能不切实际。我们建议，基于计算机的观察者对于作为评估超声图像质量和成像系统比较方法的对比度-细节分析的客观性能可能更可靠。
