Hangiandreou N J, Fetterly K A, Felmlee J P
Department of Diagnostic Radiology, Mayo Clinic and Foundation, Rochester, MN, USA.
J Digit Imaging. 1999 May;12(2):60-7. doi: 10.1007/BF03168844.
The authors previously reported a general technique based on contrast-detail methods to provide an overall quantitative evaluation of electronic image display quality. The figure-of-merit reflecting overall display quality is called maximum threshold contrast or MTC. In this work we have optimized the MTC technique through improvements in both the test images and the figure-of-merit computation. The test images were altered to match the average luminance with that observed for clinical computed radiographic images. The figure-of-merit calculation was altered to allow for contrast-detail data with slopes not equal to -1. Preliminary experiments also were conducted to demonstrate the response of the MTC measurements to increased noise in the displayed image. MTC measurements were obtained from five observers using the improved test images displayed with maximum monitor luminance settings of 30-, 50-, and 70-ft-Lamberts. Similar measurements were obtained from two observers using test images altered by the addition of a low level of image noise. The noise-free MTC and MTC difference measurements exhibited standard deviations of 0.77 and 1.55, respectively. This indicates good measurement precision, comparable or superior to that observed using the earlier MTC technique. No statistically significant image quality differences versus maximum monitor luminance were seen. The noise-added MTC measurements were greater than the noise-free values by an average of 4.08 pixel values, and this difference was statistically significant. This response is qualitatively correct, and is judged to indicate good sensitivity of the MTC measurement to increased noise levels.
作者之前报道了一种基于对比度-细节方法的通用技术，用于对电子图像显示质量进行全面的定量评估。反映整体显示质量的品质因数称为最大阈值对比度或MTC。在这项工作中，我们通过改进测试图像和品质因数计算对MTC技术进行了优化。测试图像经过修改，使其平均亮度与临床计算机X线摄影图像的亮度相匹配。品质因数计算方法也进行了修改，以考虑斜率不等于-1的对比度-细节数据。还进行了初步实验，以证明MTC测量对显示图像中增加的噪声的响应。使用最大监视器亮度设置为30、50和70英尺朗伯显示的改进测试图像，从5名观察者那里获得了MTC测量结果。使用添加了低水平图像噪声的测试图像，从2名观察者那里获得了类似的测量结果。无噪声的MTC和MTC差值测量的标准差分别为0.77和1.55。这表明测量精度良好，与使用早期MTC技术观察到的精度相当或更高。未观察到与最大监视器亮度相关的具有统计学意义的图像质量差异。添加噪声后的MTC测量值比无噪声值平均大4.08个像素值，且这种差异具有统计学意义。这种响应在定性上是正确的，并且被判定表明MTC测量对增加的噪声水平具有良好的敏感性。
