基于能量运算的磁共振信号尖峰噪声抑制方法

发布时间：2018-02-25 04:03

本文关键词： 磁共振信号参考对消算法能量运算尖峰噪声噪声相关性　出处：《地球物理学报》2016年06期 　论文类型：期刊论文

【摘要】：磁共振探测信号微弱,使用高灵敏度的核磁共振地下水探测仪,极易受到环境噪声干扰.其中,工频谐波噪声和尖峰噪声,是影响信号质量最严重的两类噪声.国内外研究表明,通过参考线圈的布设,依据探测线圈和参考线圈中噪声相关性,利用自适应参考对消算法,能够有效抑制工频谐波噪声.然而,尖峰噪声的存在严重影响了主通道与参考道的数据相关性,成为了参考对消算法应用的难题与障碍.为解决这一问题,本文提出磁共振信号中尖峰噪声的抑制方法,推导了能量域磁共振信号表达式,通过计算信号能量,可有效检测尖峰噪声并突出不易识别的小幅度尖峰噪声,采用基于中位数的绝对偏差法确定阈值,进而剔除尖峰噪声.为了验证去噪效果,与应用较广的统计叠加法进行对比研究.仿真结果表明,对于干扰幅度较大、持续时间较长的尖峰噪声,能量运算法和统计叠加法均能识别并剔除,且不损失有效的磁共振信号,标准差偏差控制在0.3%以内,可以满足实际应用的要求;对于小于信号幅度1.5倍的尖峰噪声,能量运算法可有效识别并剔除,而统计叠加法无法实现.针对多通道探测系统,使用能量运算法剔除尖峰噪声后,可明显提高主通道和参考道的数据相关性,为后续自适应参考对消算法的应用奠定了基础.实测数据处理结果进一步证明了本文方法的实用性.
[Abstract]:The magnetic resonance detection signal is weak, and the high sensitivity nuclear magnetic resonance groundwater detector is easy to be disturbed by the environmental noise, among which, the power frequency harmonic noise and the peak noise, Domestic and foreign studies show that, according to the noise correlation between the detection coil and the reference coil, the adaptive reference cancellation algorithm is used. However, the existence of peak noise seriously affects the data correlation between the main channel and the reference channel, and becomes a difficult problem and obstacle in the application of the reference cancellation algorithm. In this paper, the suppression method of peak noise in magnetic resonance signal is presented, and the expression of magnetic resonance signal in energy domain is derived. By calculating the signal energy, the peak noise can be effectively detected and the small amplitude peak noise which is not easily recognized can be highlighted. The median based absolute deviation method is used to determine the threshold value, and then the peak noise is eliminated. In order to verify the denoising effect, a comparative study is carried out with the widely used statistical superposition method. The simulation results show that the interference amplitude is large, The long duration peak noise, the energy operation method and the statistical superposition method can be recognized and eliminated, and the effective magnetic resonance signal is not lost, and the standard deviation is controlled within 0.3%, which can meet the requirements of practical application. For the peak noise which is less than 1.5 times the signal amplitude, the energy operation method can effectively identify and eliminate the peak noise, but the statistical superposition method can not be realized. For the multi-channel detection system, the energy operation method is used to eliminate the peak noise. The data correlation between the main channel and the reference channel can be improved obviously, which lays a foundation for the application of the subsequent adaptive reference cancellation algorithm. The experimental data processing results further prove the practicability of the proposed method.
【作者单位】：吉林大学仪器科学与电气工程学院/地球信息探测仪器教育部重点实验室;
【基金】：国家重大科学仪器设备开发和应用专项(2011YQ030113) 国家自然科学基金面上项目(41374075) 吉林省科技重点攻关项目(20150519008JH,20140204022GX) 中国博士后科学基金面上项目(2014M561296)联合资助
【分类号】：P631.2

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