Chinese Journal of Magnetic Resonance >
An Improved Nonlocal Means Method for CPMG Signal Denoising
Received date: 2014-08-11
Revised date: 2015-07-22
Online published: 2015-09-05
Supported by
国家自然科学基金资助项目(60972122)，上海市教委科研创新重点资助项目(14ZZ135)，国家重大科学仪器 设备开发专项资助项目(2013YQ17046303)
Echo signals obtained on low-field NMR spectrometer are often weak, and have low signal-to-noise ratio, such that the signals are easily to be buried in background noise. Aiming at solving this problem, an improved non-local means (NLM) algorithm for filtering CPMG echo signals was proposed. First, based on analysis of parameter selection methods, an adaptive damping parameter selection method with Stein unbiased risk estimation was selected for the NLM algorithm. According to the characteristics of the echo signal, an improved method using different signal point data variance was employed to find the width of the neighborhood window for the NLM algorithm. Lastly, the NLM algorithm was implemented with optimized parameters. The results on simulated and experimental data sets were reported. Compared with the existing NLM algorithm, the improved NLM algorithm was shown to be able to produce better results concerning both the filtered signals and inversed spectra.
Key words： NMR; CPMG; signal denoising; nonlocal means; SURE
ZHAO Bin1 , ZHOU Xiao-long1 , ZHANG Ying-li2 , YANG Pei-qiang2 , NIE Sheng-dong1* . An Improved Nonlocal Means Method for CPMG Signal Denoising[J]. Chinese Journal of Magnetic Resonance, 2015 , 32(3) : 499 -510 . DOI: 10.11938/cjmr20150311
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