Loo L N, Doi K, Metz C E
Phys Med Biol. 1984 Jul;29(7):837-56. doi: 10.1088/0031-9155/29/7/007.
Although various models have been proposed in an attempt to predict the usefulness of a radiographic image in terms of its physical characteristics, no previous work has shown whether a single physical image quality index, such as a signal-to-noise ratio, can reliably predict the performance of a human observer over a broad range of image characteristics. We studied the relationship between physical and visual image quality for the task of detecting nylon beads in radiographs. Thirty-seven imaging cases with different combinations of physical image characteristics were considered; these included variations in object size and magnification, X-ray beam quality, screen-film system, screen-film contact, film density and illumination, and viewing distance. For each imaging case, visual image quality was quantified in terms of observer performance in a 2AFC visual detection experiment. Physical image quality indices were calculated according to eight different models of the detection process; these indices combined data regarding object size and attenuation, screen-film system MTF, film gradient, noise Wiener spectrum, and visual system response. The results of this work indicate that, for the conditions studied, human observer detection performance most closely resembles that of a sub-optimal statistical decision process.
尽管已经提出了各种模型，试图根据射线图像的物理特征预测其有用性，但以前的工作都没有表明，像信噪比这样的单一物理图像质量指标能否在广泛的图像特征范围内可靠地预测人类观察者的表现。我们研究了在X射线照片中检测尼龙珠任务的物理图像质量与视觉图像质量之间的关系。考虑了37个具有不同物理图像特征组合的成像案例；这些包括物体大小和放大倍数、X射线束质量、增感屏-胶片系统、增感屏-胶片接触、胶片密度和照明以及观察距离的变化。对于每个成像案例，在一个二项迫选视觉检测实验中，根据观察者的表现对视觉图像质量进行量化。根据八种不同的检测过程模型计算物理图像质量指标；这些指标综合了有关物体大小和衰减、增感屏-胶片系统调制传递函数、胶片梯度、噪声维纳频谱以及视觉系统响应的数据。这项工作的结果表明，在所研究的条件下，人类观察者的检测表现与次优统计决策过程的表现最为相似。
