Klymenko V, Johnston R E, Pizer S M
Department Computer Science, University of North Carolina at Chapel Hill.
Invest Radiol. 1992 Aug;27(8):598-604. doi: 10.1097/00004424-199208000-00007.
The effect of luminance range compression on the visual threshold of a target in a computed tomographic (CT) scan was investigated in eight experiments.
Both visual increment thresholds of a hot target and visual decrement thresholds of a cold target were obtained. Realistic noisy CT images simulating a scan reconstruction and partial volume blurring were tested as representative of complex medical images. Negative versions, high luminance versions, and noise-free versions of these CT images also were tested.
In all the noisy images, as the luminance range of the image was compressed, proportionately smaller physical luminance differences between the target and its local background were needed to reach visual threshold. However, the thresholds were the same in terms of the difference in CT numbers between target and background. Noise in terms of CT numbers sets the threshold for a wide range of display conditions. In the noise-free CTs, as the luminance range was compressed, the luminance differences between the target and background needed to reach threshold also decreased, but only marginally. However, in terms of CT numbers, the thresholds were increased.
通过八项实验研究了亮度范围压缩对计算机断层扫描（CT）中目标视觉阈值的影响。
获取了热目标的视觉增量阈值和冷目标的视觉减量阈值。测试了模拟扫描重建和部分容积模糊的逼真噪声CT图像，以代表复杂的医学图像。还测试了这些CT图像的负片版本、高亮度版本和无噪声版本。
在所有噪声图像中，随着图像亮度范围的压缩，目标与其局部背景之间达到视觉阈值所需的物理亮度差异成比例减小。然而，就目标与背景之间的CT值差异而言，阈值是相同的。CT值方面的噪声为广泛的显示条件设定了阈值。在无噪声CT中，随着亮度范围的压缩，目标与背景之间达到阈值所需的亮度差异也减小，但幅度很小。然而，就CT值而言，阈值增加了。
