A Local Frequency Estimation Method Based on Log-Normal Filter
A log-normal and frequency estimation technology, applied in digital signal processing technology in the field of nuclear magnetic resonance elastography, can solve the problems of poor anti-noise performance, serious inversion artifacts, and low detection sensitivity of small tumors, so as to improve sensitivity and Effect of Noise Immunity
Active Publication Date: 2021-04-02
HEFEI UNIV OF TECH
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[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a local frequency estimation method based on a log-normal filter to solve the problem of severe inversion artifacts and serious inversion artifacts in the prior art although the AIDE algorithm has high detection sensitivity. Poor anti-noise performance, although the LFE algorithm has few inversion artifacts, it is also very sensitive to noise interference, and the detection sensitivity of small tumors is not high.
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[0023] The present embodiment provides a local frequency estimation method based on a lognormal filter, the method comprising the following steps:
[0024] Step 1. Obtain the signal S to be analyzed that needs to analyze the local frequency properties A , set the estimated bandwidth B according to the sensitivity requirement, divide the whole frequency range from 0 to π with N center frequencies sequentially, and the i-th center frequency is ρ i , i=1,2,...,N, and make the center frequency ρ in two adjacent frequency ranges i+1 / ρ i As a fixed value, determine the parameters, β=1 / log 2 (ρ i+1 / ρ i ), β is the logarithmic reciprocal proportional relationship coefficient of adjacent center frequencies;
[0025] Step 2, the S A respectively by the center frequency ρ i The determined transfer function is The lognormal filter of , obtains N output results, among which the i-th output result is S Ai ;
[0026] Step 3. Divide the directions from 0 to 360 degrees into M blo...
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The invention discloses a lognormal filter-based local frequency estimation algorithm, and relates to the technical field of digital signal processing. A new narrowband estimation result expression defined in the specification and a new broadband estimation result calculation formula defined in the specification are proposed; an original technology only can perform narrowband estimation under thecondition that alpha is equal to 1, so that after the filter bandwidth is set, a central frequency ratio relationship of a filter bank used for covering frequency bands 0-pi cannot be changed, and theestimated filter bandwidth and the filter number are mutually restricted; and the limitation is broken through theoretically, so that more filters can be adopted under the condition that the estimated filter bandwidth is kept unchanged, the superiority of the lognormal filters can be exerted to the maximum extent, and the beneficial effect of improving the sensitivity and anti-noise performance of the lognormal filter-based local frequency estimation algorithm at the same time is achieved.
Description
technical field [0001] The invention mainly relates to the application of digital signal processing technology in the field of nuclear magnetic resonance elastography, in particular to a local frequency estimation method based on a logarithmic normal filter. Background technique [0002] Clinically, doctors have a long history of using manual palpation to judge tissue lesions. Tissue puncture is also an important means to obtain tissue characteristics, but it is very detrimental to the health of patients. Magnetic resonance elastography is a very useful non-destructive tissue elasticity measurement technique, but it is mainly used in scientific research at present, and no formal clinical diagnostic standards and specifications have been formed. Magnetic resonance elastography needs to input mechanical waves into human tissue to vibrate the tissue, collect the displacement distribution of mechanical waves in human tissue through a special phase-sensitive sequence for magnetic...
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IPC IPC(8): G06F17/15
CPCG06F17/15
Inventor 李炳南胡亮亮单翔
Owner HEFEI UNIV OF TECH