Ultrasonic image construction method, apparatus and signal-processing method

Patent metadata

Field	Value
Publication number	US-2021150709-A1
Application number	US-202017097086-A
Country	US
Kind code	A1
Filing date	Nov 13, 2020
Priority date	Nov 19, 2019
Publication date	May 20, 2021
Grant date	—

Abstract

This invention provides a signal-processing method that makes it possible to acquire, relatively easily and surely, a highly reliable normalized impulse-response signal without relying on the signal-correction processing after normalization. The signal-processing method of this invention includes a low-frequency extraction step, a high-frequency extraction step and a synthesizing step. In the low-frequency extraction step, only the low-frequency component is extracted from the spectrum of the first normalized signal NS1 obtained by normalizing the target signal Stgt in the time domain. In the high-frequency extraction step, only the high-frequency component is extracted from the spectrum of the second normalized signal NS2 obtained by normalizing the target signal Stgt in the frequency domain using the reference signal Sref. In the synthesizing step, the low-frequency component, derived from the first normalized signal NS1, and the high-frequency component, derived from the second normalized signal NS2, are synthesized to obtain a normalized impulse-response signal NS.

First claim

1 . An ultrasonic-image construction method characterized in comprising: a transmitting/receiving step in which an ultrasonic pulse is transmitted through the substrate in the state whereof the target substance and the reference substance are in contact with the substrate and in which the target signal from the target substance and the reference signal from the reference substance are received; a signal-normalization step to extract only the low-frequency component from the first normalized signal obtained by normalizing the target signal in the time domain, and to extract only the high-frequency component from the second normalized signal obtained by normalizing the target signal in the frequency domain using the reference signal, so as to synthesize the low-frequency component derived from the first normalized signal with the high-frequency component derived from the second normalized signal, thus obtaining the normalized impulse signal; a characteristic acoustic-impedance distribution-estimation step to estimate sequentially the characteristic acoustic-impedance distribution in the target substance from the front side to the back side in the depth direction according to the normalized impulse-response signal; and an image-construction step to construct the image data of the acoustic property image according to the characteristic acoustic-impedance distribution in the depth direction.

2 . An ultrasonic-image construction method according to claim 1 , characterized in that in the signal-normalization step, before extracting only the high-frequency component from the second normalized signal, a waveform is formed by applying a window function to the reference signal and to the target signal.

3 . An ultrasonic-image construction method according to claim 1 , characterized in that in the signal-normalization step, the first normalized signal after extracting only the low-frequency component is converted into the frequency domain by Fourier transform.

4 . An ultrasonic-image construction method according to claim 1 , characterized in that in the signal-normalization step, the low-frequency component derived from the first normalized signal and the high-frequency component derived from the second normalized signal are synthesized in the frequency domain and thereon the acquired normalized impulse-response signal is converted into the time domain from the frequency domain by inverse Fourier transform.

5 . An ultrasonic-image construction method according to claim 1 , characterized in that in the signal-normalization step, down-sampling processing is performed after removing the high-frequency component from the reference signal and from the target signal, respectively, thereafter, the target signal, after the down-sampling process, is normalized in the time domain using the reference signal after the down-sampling process, thus extracting only the low-frequency component from the first normalized signal.

6 . A signal-processing method according to claim 1 , characterized in that in the signal-normalization step, the source signal is obtained by removing the low-frequency component and the high-frequency component from the spectrum of the second normalized signal, thereon such an source signal is converted in the time domain for a peak detection, thereafter a base signal having an impulse is generated around the peak, thus normalizing the target signal in the time domain using the base signal instead of the reference signal, thus extracting only the low-frequency component from the first normalized signal.

7 . An ultrasonic-image-construction apparatus, characterized in comprising: a substrate; an ultrasonic transducer to transmit an ultrasonic pulse through the substrate in a state where the target substance and the reference substance are in contact with the substrate and which can receive the target signal from the target substance and receive the reference signal from the reference substance; a signal-normalization means to extract only the low-frequency component from the first normalized signal obtained by normalizing the target signal in the time domain and to extract only the high-frequency component from the second normalized signal obtained by normalizing the target signal in the frequency domain using the reference signal, so as to synthesize the low-frequency component derived from the first normalized signal with the high-frequency component derived from the second normalized signal, thus obtaining a normalized impulse-response signal; a characteristic acoustic-impedance distribution-estimation means to estimate sequentially the characteristic acoustic-impedance distribution in the target substance from the front side to the back side in the depth direction according to the normalized impulse-response signal; and an image-construction means to construct the image data of the acoustic property image according to the acoustic-impedance distribution in the depth direction obtained by the characteristic acoustic-impedance distribution-estimation means.

8 . An ultrasonic-image-construction apparatus according to claim 7 , characterized in that by the signal-normalization means, before extracting only the high-frequency component from the second normalized signal, a waveform is formed by applying a window function to the reference signal and to the target signal.

9 . An ultrasonic-image-construction apparatus according to claim 7 , characterized in that by the signal-normalization means, the first normalized signal after extracting only the low-frequency component is converted into the frequency domain by Fourier transform.

10 . An ultrasonic-image-construction apparatus according to claim 7 , characterized in that by the signal-normalization means, the low-frequency component derived from the first normalized signal and the high-frequency component derived from the second normalized signal are synthesized in the frequency domain and thereon the acquired normalized impulse-response signal is converted into the time domain from the frequency domain by inverse Fourier transform.

11 . An ultrasonic-image-construction apparatus according to claim 7 , characterized in that by the signal-normalization means, down-sampling processing is performed after removing the high-frequency component from the reference signal and from the target signal, respectively, thereafter, the target signal, after the down-sampling process, is normalized in the time domain using the reference signal after the down-sampling process, thus extracting only the low-frequency component from the first normalized signal.

12 . An ultrasonic-image-construction apparatus according to claim 7 , characterized in that by the signal-normalization means, the source signal is obtained by removing the low-frequency component and the high-frequency component from the spectrum of the second normalized signal, thereon such an source signal is converted in the time domain for a peak detection, thereafter a base signal having an impulse is generated around the peak, thus normalizing the target signal in the time domain using the base signal instead of the reference signal, thus extracting only the low-frequency component from the first normalized signal.

13 . A signal-processing method for acquiring a normalized impulse-response signal based on a target signal obtained by pulse-wave irradiation against a target substance, and a reference signal obtained by pulse-wave irradiation against a reference substance, characterized in comprising: a low-frequency extraction step to extract only the low-frequency component from the spectrum of the first normalized signal obtained by normalizing the target signal in the time domain; a high-f

Assignees

• Honda Electronic
• National Univ Corporation Toyohashi Univ Of Technology

Inventors

• Kobayashi Kazuto
• Hozumi Naohiro

Classifications

• A61B8/0858

  involving measuring tissue layers, e.g. skin, interfaces · CPC title

• G01S7/52026

  Extracting wanted echo signals (Doppler systems G01S15/50; Doppler short range imaging systems G01S15/8979) · CPC title

• G01S7/5206 Primary

  Two-dimensional coordinated display of distance and direction; B-scan display · CPC title

• G01S15/8977

  using special techniques for image reconstruction, e.g. FFT, geometrical transformations, spatial deconvolution, time deconvolution · CPC title

• G06T7/0012 Primary

  Biomedical image inspection · CPC title