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A magnetic resonance sounding signal sparse denoising method based on particle swarm optimization

A particle swarm optimization and signal sparse technology, which is applied in the fields of electronic magnetic resonance/nuclear magnetic resonance detection, instrumentation, calculation, etc. The effect of reducing information loss, fast calculation speed, and enhanced calculation accuracy

Active Publication Date: 2019-06-14
JILIN UNIV
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Problems solved by technology

[0006] Aiming at the shortcomings of low operating efficiency, rough calculation accuracy, and incomplete information of MRS signals caused by the direct application of traditional matching and pursuit algorithms, the present invention provides a sparse denoising method for magnetic resonance sounding signals based on particle swarm optimization. Not only can it realize the effective filtering of multiple power frequency harmonics and random white noise, but also effectively speed up the optimization process of matching pursuit, and then reconstruct the MRS signal through the final best atom

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  • A magnetic resonance sounding signal sparse denoising method based on particle swarm optimization
  • A magnetic resonance sounding signal sparse denoising method based on particle swarm optimization
  • A magnetic resonance sounding signal sparse denoising method based on particle swarm optimization

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Embodiment 1

[0099] This embodiment is a simulation experiment of the method of the present invention carried out under the MATLAB 7.0 programming environment.

[0100] The simulation algorithm of sparse denoising method for magnetic resonance sounding signal based on particle swarm optimization, refer to figure 1 , including the following steps:

[0101] Step (1): Use the formula Construct a Larmor frequency of 2345Hz and an amplitude of e 0 150nV, the relaxation time An ideal MRS signal of 0.18s, such as image 3 The ideal MRS signal shown ( image 3 A) and its spectrum ( image 3 B). Add power frequency interference of 2200Hz, 2250Hz, 2300Hz, 2350Hz, 2400Hz, 2450Hz and 2500Hz near the Larmor frequency of the signal and random noise with an amplitude of 100nV, and form an observation with a signal-to-noise ratio of -6.7471dB through a certain linear combination MRS signal x(t) (row vector), such as Figure 4 The noisy MRS signal shown ( Figure 4 A) and its spectrum ( Figure...

Embodiment 2

[0106] In this embodiment, the actual measured MRS signal collected on the spot in Changchun Cultural Square is used as the processing object of the method of the present invention.

[0107] A sparse denoising method for magnetic resonance sounding signals based on particle swarm optimization, such as figure 1 shown, including the following steps:

[0108] Step (1): For a set of observed MRS signals X(t) collected by the nuclear magnetic resonance sounding (MRS) water detector, such as Figure 7 The measured MRS signal shown ( Figure 7 A) and its spectrum ( Figure 7 B); Utilize the mode of band-pass filtering to preprocess it, and obtain the noisy MRS signal x(t) (for a row vector) within the target frequency band, such as Figure 8 As shown in A, calculate its signal-to-noise ratio as SNR=-7.11dB; carry out Fourier transform to it to obtain its frequency spectrum, as Figure 8 As shown in B, it can be seen that the signal is at f 1 =2300Hz, f 2 = 2400Hz has strong pow...

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Abstract

The invention discloses a magnetic resonance sounding signal sparse denoising method based on particle swarm optimization. The method is mainly used for processing the power frequency harmonic interference and the random white noise in magnetic resonance signals. The method comprises the steps of firstly, preprocessing the MRS signals collected by a magnetic resonance sounding water exploration instrument in a band-pass filtering mode, obtaining the power frequency harmonic interference contained in the collected signals and the frequency of the MRS signals through frequency spectrum analysis,and constructing the oscillation atom libraries for the MRS signals and the power frequency harmonic noise characteristics respectively; secondly, recording an individual extremum and a population extremum by adopting a particle swarm algorithm to update the speed and the position of each particle in the particle swarm, and selecting an optimal atom from a power frequency harmonic oscillation atom library to reconstruct the power frequency so as to remove harmonic interference; and finally, selecting an optimal atom from the MRS signal oscillation atom library by using a particle swarm algorithm to reconstruct the MRS signal, if the MRS signal does not meet the experimental requirements, calculating a residual error signal, and repeatedly iterating until the condition is met. According tothe method, a novel atom library for the MRS signal is constructed, the power frequency harmonic interference and the random white noise in the noise-containing MRS signal are effectively filtered, and compared with a traditional MRS signal denoising method, the method has the advantages of being fast in operation speed, high in precision, strong in practicability and the like.

Description

technical field [0001] The invention belongs to the field of magnetic resonance sounding (Magnetic Resonance Sounding, MRS) signal noise filtering, in particular to a particle swarm optimization-based sparse denoising method for magnetic resonance sounding signals. Background technique [0002] Compared with geophysical methods such as ground penetrating radar, electromagnetic method and resistivity sounding, which can only provide indirect lithology information of aquifers, magnetic resonance sounding (magnetic resonance sounding, MRS) is currently the only direct detection method in the world. The geophysical exploration method of groundwater can give quantitative explanations for information such as groundwater content, aquifer location and thickness, and underground medium porosity, so it is widely used in water resource exploration, evaluation, dam leakage, mine / tunnel water inrush and other fields. [0003] Since the MRS signal is very weak, it is at the nanovolt leve...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/50G06K9/00G01V3/14G06N3/00
Inventor 田宝凤王亮王子强刘健楠
Owner JILIN UNIV
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