Normalization of the modulation transfer function: The open-field approach
Normalization of the modulation transfer function: The open-field approach
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DOI：
10.1118/1.2977536
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发表时间：
2008-10-01
期刊：
影响因子：
3.8
通讯作者：
Cunningham, I. A.
中科院分区：
文献类型：
--
作者：
Friedman, S. N.;Cunningham, I. A.
调制传递函数（MTF）被广泛用于描述x射线成像系统的空间分辨率。MTF定义为零频率值为1，通常的做法是通过用零频率值对测量的MTF曲线进行归一化来确保这一点。然而，在有限感兴趣区域（ROI）内截断线扩展函数（LSF）会导致频谱泄漏，并导致测量到的MTF零频率值减少，减少的面积等于截断的LSF尾部的面积。随后按此值进行规范化可能导致MTF值膨胀。我们表明，无论ROI大小如何，使用边缘方法的开场归一化在所有非零频率下产生准确的MTF值，而无需进一步归一化零频率值。虽然这两种归一化技术对于足够大的ROI是等效的，但当使用10厘米的ROI时，观察到基于csi的平板系统的MTF值增加了5%。使用开场归一化避免了零频率归一化造成的潜在通货膨胀。(C) 2008年美国医学物理学家协会。
The modulation transfer function (MTF) is widely used to describe the spatial resolution of x-ray imaging systems. The MTF is defined to have a zero-frequency value of unity, and it is common practice to ensure this by normalizing a measured MTF curve by the zero-frequency value. However, truncation of the line spread function (LSF) within a finite region of interest (ROI) results in spectral leakage and causes a reduction in the measured MTF zero-frequency value equal to the area of truncated LSF tails. Subsequent normalization by this value may result in inflated MTF values. We show that open-field normalization with the edge method produces accurate MTF values at all nonzero frequencies without need for further normalization by the zero-frequency value, regardless of ROI size. While both normalization techniques are equivalent for a sufficiently large ROI, a 5% inflation in MTF values was observed for a CsI-based flat-panel system when using a 10 cm ROI. Use of open-field normalization avoids potential inflation caused by zero-frequency normalization. (C) 2008 American Association of Physicists in Medicine.