Amtey S R, Tyson R K
Med Phys. 1977 Jan-Feb;4(1):9-14. doi: 10.1118/1.594352.
In the Siemens star image, exact determination of the first disappearance frequency, which is used to measure the focal spot size, is difficult since the disappearance band has a finite width and the image also has other artifacts. The origin of these artifacts and their appearance was studied by Siemens star image simulation on a digital computer. The simulated images were manipulated by using many different modulation and phase transfer functions. It is shown that the bending of spokes is not related to zero contrast; exact triplet splitting can occur only at the disappearance frequency, and therefore splitting is a valuable indicator of that frequency.
在西门子星型图像中，由于消失带具有有限宽度且图像还存在其他伪影，所以难以精确确定用于测量焦点尺寸的首个消失频率。通过在数字计算机上进行西门子星型图像模拟，研究了这些伪影的来源及其表现。利用许多不同的调制和相位传递函数对模拟图像进行处理。结果表明，辐条的弯曲与零对比度无关；精确的三重分裂仅会在消失频率处出现，因此分裂是该频率的一个重要指标。
