摘要
本文针对数字放射系统的调制传递函数测量问题,提出一种基于维纳解卷积方法,从倾斜刀口图像中测量过采样调制传递函数的新方法。首先根据实际数字放射系统特性,模拟给定调制传递函数下倾斜刀口带噪图像,并获取对应的经过系统恶化后的过采样边界扩散函数,而后依据该边界扩散函数的中心边界位置,构建无恶化效应的理想边界扩散函数。为了满足傅里叶变换的绝对可积条件,对上述两类边界扩散函数进行镜像操作,构成偶对称模式的边界扩散函数。基于维纳解卷积,在已知理想边界扩散函数对称模式,并考虑系统噪声影响,可以从恶化过采样边界扩散函数的对称模式中获取过采样线扩散函数。该过采样线扩散函数的傅里叶归一化幅度即为系统的调制传递函数。本文同时给出了维纳参数值以及对称模式下边界响应函数宽度对解卷积结果准确性的影响。结果表明,针对倾斜刀口图像,基于本文提出的维纳解卷积方法可以有效的测量过采样调制传递函数。
A Novel method for determining the presampling modulation transfer function (MTF) of digital radiography systems from slanted edge images was developed based on Wiener deconvolution. The supersampled degraded edge spread function (ESF) was obtained from simulated slanted edge images with known MTF in the presence of poisson noise, and its corresponding ideal ESF without degration was constructed according to its central edge position. To meet the requirements of the absolute integrable condition of Fourier transformation, the origianl ESFs were mirrored to construct the symmetric pattern of ESFs. Then based on Wiener deconvolution technique, the supersampled line spread function (LSF) could be acquired from the symmetric pattern of supersampled degraded ESFs in the presence of ideal symmetric ESFs and system noise. The MTF is then the normalized magnitude of the Fourier transform of the LSF. The determined MTF showed a strong agreement with the theoritical true MTF when appropriated Wiener parameter was chosen. The effects of Wiener parameter value and the width of square-like wave peak in symmetric ESFs were illustrated and discussed. In conclusion, an accurate and simple method to measure the presampling MTF was established using Wiener deconvolution technique according to slanted edge images.
出处
《新型工业化》
2013年第3期58-66,共9页
The Journal of New Industrialization
基金
National Natural Science Foundation of China(30870657,30970775,81101106,61108081)
Chinese National Programs for High Technology Research and Development(2009AA02Z413)
Tianjin Municipal Government of China(09JCZDJC18200,10JCZDJC17300)
Tianjin Natural Science Foundation of China(12JCQNJC09400)
Ph.D.Programs Foundation of Ministry of Education of China(20100032120064 and 20110032120069)
关键词
调制传递函
线扩散函数
边界扩散函数
维纳解卷积
modulation transfer function(MTF)
line spread function(LSF)
edge spread function(ESF)
Wiener deconvolution
