Full-wave magnetic resonance signal random noise abatement method combining EMD and TFPF algorithms

Abstract

The invention relates to a full-wave magnetic resonance signal random noise abatement method combining EMD and TFPF algorithms. The method is a 'blind' filtering method in which filtering range designis not needed. The method comprises the steps of firstly utilizing decomposition characteristics of the EMD algorithm to decompose full-wave magnetic resonance signals into different intrinsic mode functions, then using the TFPF algorithm to code signal dominant mode functions into instantaneous frequencies of unit amplitude analytic signals, and utilizing the characteristic that time-frequency distribution of the analytic signals is concentrated along instantaneous frequency to inhibit random noise. The full-wave magnetic resonance signal random noise abatement method combining the EMD and TFPF algorithms has the advantages that few filtering constraint conditions are needed, the operation is simple, there is no need to design a filtering range in a time-frequency domain, and the methodhas high adaptability to full-wave magnetic resonance signals with a low signal-noise rate; the detection efficiency is remarkably improved, a good denoising effect can be obtained only through once measuring, random noise is effectively reduced, signal components are not lost at the same time, the signal-to-noise ratio can be remarkably increased, and the accuracy of later inversion is improved.

Description

Technical field: [0001] The invention relates to a method for reducing noise of a magnetic resonance sounding (Magnetic Resonance Sounding, MRS) signal, in particular to a data processing method for reducing random noise contained in a full-wave magnetic resonance signal based on the principle of a combined algorithm of EMD and TFPF. Background technique: [0002] Magnetic resonance groundwater detection technology is an emerging geophysical detection technology. Due to its advantages of direct detection and quantitative evaluation, it has received extensive attention in recent years and has achieved rapid development. At present, it has gradually developed from theoretical research to the development of a relatively mature instrument detection system, and has carried out field measurements in some areas, and successfully detected shallow groundwater resources. Significance. However, due to the relaxation of excited hydrogen protons in groundwater, the magnetic resonance si...

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Problems solved by technology

[0004] The noise filtering method for full-wave nuclear magnetic resonance signals based on independent component analysis of the above invention can solve the traditional underdetermined blind source problem and amplitude uncertainty problem in independent component analysis. Compared with traditional MRS signal denoising methods, it has the advantages of calculation It has the advantages of fast speed, high signal-to-noise ratio, and strong practicability, but this method can only filter out power frequency interference and a certain frequency interference, and cannot suppress noise interference with a large frequency band distribution such as random noise; and based on cross-correlation The NMR full-wave signal noise filtering method can suppress power frequency and its harmonic noise, random noise and spike noise at the same time, but it mainly uses the uncorrelated characteristics of noise frequency and signal frequency. The part cannot be removed; the ICA-based NMR groundwater detection signal noise elimination method does not require prior knowledge of the source signal and transmission channel, and does not need to lay a reference coil during the test, which is simple, convenient and efficient, but the method It requires at least three sets of data, and the calculation process is complicated, the amount of calculation is large, and it is difficult for non-technical personnel to control; the superposition method is currently the simplest and most commonly used random noise reduction method for magnetic resonance signals. In the environment, the groundwater magnetic resonance signal with a higher signal-to-noise ratio can be obtained by using fewer stacking times, but when the noise intensity is large, multiple stacking is required, which will increase the measurement time and reduce the working efficiency of the instrument. limited effect

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