Frequency chosen of singular-spectrum analysis-based magnetic resonance sounding signal extraction method

A technology of signal extraction and frequency selection, which is applied in magnetic resonance measurement, measurement using nuclear magnetic resonance image system, measurement of magnetic variables, etc., can solve problems such as MRS signal extraction, and achieve the effect of effective extraction

Active Publication Date: 2018-04-24
JILIN UNIV
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Problems solved by technology

[0005] The technical problem to be solved by the present invention is to provide a method for extracting magnetic resonance sounding signals based on frequency-selective singular spectrum analysis to solve the problem of MRS signal extraction caused by the influence of complex peak noise, power frequency harmonics and random noise in the environment.

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  • Frequency chosen of singular-spectrum analysis-based magnetic resonance sounding signal extraction method
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  • Frequency chosen of singular-spectrum analysis-based magnetic resonance sounding signal extraction method

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Embodiment 1

[0110] This embodiment is a simulation experiment of the method of the present invention carried out under the MATLAB 2015a programming environment. The simulation algorithm of the magnetic resonance sounding signal extraction method based on frequency-selective singular spectrum analysis, refer to figure 1 , including the following steps:

[0111] Step (1): Construct a Larmor frequency of 2114Hz and an amplitude e 0 is 180nV, the relaxation time T 2 * 0.1s, a pure MRS signal with a phase of 1.03, the signal sampling rate is 10kHz, the signal length is 500ms, and the number of data points is 5000, such as image 3 (a) and image 3 (b) shown. On the basis of this signal, 16 groups of noise-containing signals are simulated, and each group of signals is added with 100 power frequency interferences with an amplitude of 100nV, random phase, and an integer multiple of 50Hz between 0Hz and 5000Hz; the amplitude is 100nV, continuous Spike noise with a duration of 10ms and random...

Embodiment 2

[0120] In this embodiment, the MRS signals collected in Shaoguo Town, Changchun City (the Larmor frequency is about 2332.5 Hz) are used as the processing object of the method of the present invention. Such as figure 1 As shown, the magnetic resonance sounding signal extraction method based on frequency-selective singular spectrum analysis includes the following steps:

[0121] Step (1): Collect a set of observed MRS signals X using the nuclear magnetic resonance sounding (MRS) water detector 1 (t) (for a row vector), such as Figure 8 (a) and Figure 8 As shown in (b), the sampling rate is 25kHz, the number of data points is 12476, and the signal-to-noise ratio is calculated as SNR=-7.1453dB;

[0122] Step (2): The MRS signal X will be observed 1 (t) After such Figure 9 In the bandpass filter shown, the bandpass filter used is a Chebyshev filter, the left boundary of the passband is 2100Hz, the right boundary of the passband is 2500Hz, the left boundary of the stopband i...

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Abstract

The invention relates to a frequency chosen of singular-spectrum analysis-based magnetic resonance sounding signal extraction method. According to the method, a nuclear magnetic resonance sounding water detector is used to collect MRS signals of a Larmor frequency-known region; a broadband band-pass filter is adopted to suppress partial noises, and thereafter, the position of MRS signals corresponding to the Larmor frequency are found on a power spectrum based on power spectrum analysis; and frequency chosen of singular-spectrum analysis is performed, so that the MRS signals are extracted. Thefrequency chosen of singular-spectrum analysis includes the following four steps that: embedding is performed; RSVD (Regularized Singular Value Decomposition) is performed; and corresponding singularvalues are selected according to the amplitudes of the MRS signals so as to perform matrix reconstruction; and diagonal averaging is performed. With the method of the invention adopted, random noises, spike noises and power frequency harmonic interference can be effectively filtered from noise-containing MRS signals; and the effective extraction of the MRS signals under a complex strong noise interference condition can be realized. Compared with a traditional MRS signal de-noising method, the method has the advantages of high operation speed, high signal-to-noise ratio, high practicality andthe like.

Description

technical field [0001] The invention relates to the technical field of magnetic resonance sounding (also known as ground nuclear magnetic resonance) groundwater detection signal noise filtering and parameter extraction, in particular to a method for extracting magnetic resonance sounding signals based on frequency-selective singular spectrum analysis. Background technique [0002] Magnetic Resonance Sounding (MRS) technology is the only method to directly and quantitatively characterize water content and pore structure. Its basic principle is to detect groundwater by detecting the MRS signal response generated by the hydrogen-proton resonance transition in groundwater. The order of magnitude of the MRS signal is nanovolts, which is very weak, and is easily interfered by random noise, power frequency harmonics and spikes in the environment, which will affect the quality of the detected MRS signal, which in turn will affect the extraction of the characteristic parameters of the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R33/54
CPCG01R33/54
Inventor 田宝凤范頔蒋川东易晓峰
Owner JILIN UNIV
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