Giger M L, Doi K
Med Phys. 1985 Mar-Apr;12(2):201-8. doi: 10.1118/1.595708.
The effect of pixel size on the signal-to-noise ratio (SNR) and threshold detection of low-contrast radiologic patterns was investigated theoretically for digital radiographic systems. The SNR based on the perceived statistical decision theory model, together with the internal noise of the human eye-brain system, was calculated by using two-dimensional displayed digital signal spectra and noise Wiener spectra. Threshold contrasts were predicted from the calculated SNR for various combinations of object size and shape, pixel size, resolution, and noise. Predicted threshold contrasts agreed well with those determined experimentally in an observer performance study. The threshold contrast of small objects increased substantially as the pixel size increased beyond 0.2 mm. For pixel sizes of 0.1 and 0.2 mm, however, the threshold contrasts were similar. Since a digital system is not shift invariant, a range of threshold contrast results for a small object and a large pixel, depending on the alignment of the object position relative to the sampling coordinates.
针对数字射线照相系统，从理论上研究了像素大小对低对比度放射学影像的信噪比（SNR）和阈值检测的影响。基于感知统计决策理论模型的信噪比，结合人眼-脑系统的内部噪声，通过二维显示数字信号谱和噪声维纳谱进行计算。针对物体大小和形状、像素大小、分辨率及噪声的各种组合，根据计算出的信噪比预测阈值对比度。预测的阈值对比度与在观察者性能研究中通过实验确定的结果吻合良好。当像素大小超过0.2毫米时，小物体的阈值对比度大幅增加。然而，对于0.1毫米和0.2毫米的像素大小，阈值对比度相似。由于数字系统不是平移不变的，对于小物体和大像素，根据物体位置相对于采样坐标的对齐情况，会得到一系列阈值对比度结果。
