基于过抽样Gabor变换的核磁共振FID信号增强算法  

NMR FID SIGNAL ENHANCEMENT VIA OVERSAMPLING GABOR TRANSFORMATION

作　　者：陶亮[1] 顾涓涓[2] 

机构地区：[1]安徽大学计算机科学与技术学院,安徽合肥230039 [2]合肥学院计算机信息工程系,安徽合肥230022

出　　处：《波谱学杂志》2004年第4期435-443,共9页Chinese Journal of Magnetic Resonance

基　　金：教育部优秀青年教师资助计划项目 (教人司 [2 0 0 2 ]40号 ) ;安徽省自然科学基金项目 ( 0 1 0 42 2 1 0 ) ;安徽省教育厅自然科学重点研究项目 ( 2 0 0 1kj0 2 0zd) ;安徽大学人才队伍建设资助项目

摘　　要：基于作者先前提出的过抽样实值离散Gabor变换 ,本文提出了一有效的算法用于核磁共振自由感应衰减 (NMRFID)信号的减噪 .由于NMRFID信号在时域中是一短暂的振荡衰减信号 ,使得变换后的NMRFID信号能量在时频域中集中在少数变换系数上 ,而噪声则遍布在整个变换系数上 ,因此通过对变换系数幅度进行阈值限制方法可达到明显地增强NMRFID信号的目的 .文中在理论和模拟实验上分析表明 ,过抽样Gabor变换比临界抽样Gabor变换更适宜于NMRFID信号的减噪 ,因为在过抽样条件下比在临界抽样条件下的综合窗及其对应的分析窗 ,无论是在时域中还是在频域中都可具有更好的局域分布集中性 ,同时 。An efficient algorithm is proposed to reduce the noise in NMR FID signals based on the real-value discrete Gabor transformation developed in our previous work. As NMR FID signals in the time domain are short oscillating decay signals, the FID signals in Gabor transformation domain (i.e., a joint time-frequency domain) are concentrated in very few number of Gabor transformation coefficients, while the noise is fairly distributed among all the coefficients. Therefore, performing a threshold-limiting work in the transform domain can significantly enhance the NMR FID signals. The theoretical and experimental analyses presented in this paper show that oversampling Gabor transformation is more suitable for NMR FID signal enhancement than critically-sampling transformation, because the synthesis window and its corresponding analysis window in the oversampling case can have better localization in both time domain and frequency domain than that in the critically-sampling case. Furthermore, the oversampling Gabor transform can lead to higher time and frequency resolution than the critically-sampling one.

关 键 词：信号增强 过抽样 变换系数 实值离散GABOR变换 时域 样条 幅度 NMR 临界 核磁共振 

分 类 号：O174.2[理学—数学] TN911[理学—基础数学]