JP2000254118A - Ultrasonic imaging method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hardly receive the influence of a non-linearity in ultrasonic wave propagation by transmitting ultrasonic wave where a crest factor is set to be small, orthogonally detecting a received echo signal at every frequency component, reversely Fourier-transforming it and generating an image based on the reversely Fourier-transformed signal. SOLUTION: An ultrasonic wave probe 2 is abutted on the desired part of a testee body 100, an operating part 14 is operated and the image is picked-up by ultrasonic wave. Imaging is made under the control of a control part 12 based on a command. A transmitting/receiving part 6 exchanges an ultrasonic wave beam by a multi-tone signal with the small crest factor. The crest factor in multi-tone transmission ultrasonic wave is small so that influence of the non-linearity of ultrasonic wave propagation is hardly received. Then ultrasonic wave without a waveform distortion is transmitted. A data processing part 8 orthogonally detects the wave of the multi-tone echo signal at every frequency component, reversely Fourier-transforming it, obtaining an A scope signal, generating a B-mode image based on its and displays it in a display part 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic imaging method and apparatus, and more particularly, to an ultrasonic imaging method and apparatus for transmitting ultrasonic waves composed of a plurality of frequency components and performing imaging based on echoes thereof. About.

[0002]

2. Description of the Related Art Pulse echo
In the ultrasonic imaging of the system, a pulsed ultrasonic wave is transmitted, its echo is received, and an image is generated based on the echo reception signal. S / N (signal to noise)
In order to perform imaging with good ratio, the amplitude of the pulsed ultrasonic wave is set to be as large as possible.

[0003]

In the ultrasonic imaging of the pulse echo system, the waveform of the pulsed ultrasonic wave is distorted due to the nonlinearity of the ultrasonic wave propagation in the sound field, so that the quality of the captured image deteriorates. Was.

The present invention has been made to solve the above problems, and an object of the present invention is to realize an ultrasonic imaging method and apparatus which are hardly affected by nonlinearity of ultrasonic propagation.

[0005]

Prior to describing means for solving the problems, a preliminary crest factor (c
multi factor (mu) with small rest factor
(ltitone) signal will be described. Such multitone signals are described, for example, in the literature S.M. Boyd: Mul
titone Signal with Low Cr
est Factor, IEEE TRANSACTI
ONS ON CIRCUIT ANDSYSTEM
S, VOL. CAS-33, NO. 10, OCTOBE
R 1986.

[0006] In brief, a multi-tone signal, that is, a signal composed of a sum of a plurality of frequency components

[0007]

(Equation 1)

In the above, the phase δk of each frequency component is set to a Shapiro-Rudin phase or a Newman phase, so that the crest factor, that is, the ratio of the peak value to the effective value is set to 3 or less. be able to.

In the Shapiro-Rudin phase, for example, k is 32
In the case of, the phase δk of each frequency component is

[0010]

(Equation 2)

[0011] The Newman phase is the phase δk of each frequency component.

[0012]

(Equation 3)

[0013] In the present invention, such a multitone signal is used for transmitting an ultrasonic wave. (1) A first aspect of the present invention for solving the above-described problem is to transmit an ultrasonic wave composed of a plurality of frequency components whose phases are individually set so as to reduce a crest factor of a synthesized signal, receive the echo, An ultrasonic imaging method, comprising: performing orthogonal detection on the received echo signal for each frequency component; performing an inverse Fourier transform on the orthogonally detected signal; and generating an image based on the inverse Fourier transformed signal. .

(2) A second aspect of the present invention for solving the above-mentioned problem is to transmit an ultrasonic wave composed of a plurality of frequency components, each phase of which is set so as to reduce the crest factor of a composite signal, and to echo the echo. Ultrasonic transmitting and receiving means for receiving,
Orthogonal detection means for orthogonally detecting the received echo signal for each frequency component, conversion means for performing an inverse Fourier transform of the orthogonally detected signal, and image generation means for generating an image based on the inverse Fourier-transformed signal; An ultrasonic imaging apparatus comprising:

(3) A third aspect of the present invention for solving the above-mentioned problems is the ultrasonic imaging apparatus according to (2), wherein the phase is a Shapiro-Rudan phase. (4) A fourth invention for solving the above-mentioned problem is the ultrasonic imaging apparatus according to (2), wherein the phase is a Newman phase.

(Function) In the present invention, since an ultrasonic wave having a small crest factor is transmitted, waveform distortion due to nonlinearity of propagation in a sound field hardly occurs, and an image generated based on such an echo of the ultrasonic wave has high quality. It will be good.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the ultrasonic imaging apparatus. This apparatus is an example of an embodiment of the ultrasonic imaging apparatus of the present invention. The configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. An example of an embodiment of the method of the present invention is shown by the operation of the present apparatus.

The configuration of the present apparatus will be described. As shown in the figure, the present apparatus has an ultrasonic probe (probe) 2. The ultrasonic probe 2 is used for transmitting and receiving ultrasonic waves while being in contact with the subject 100. The ultrasonic probe 2 includes an ultrasonic transducer array (transdu) (not shown).
cer array). The ultrasonic transducer array has a plurality of ultrasonic transducers. Each ultrasonic transducer is made of a piezoelectric material such as PZT (lead zirconate titanate (Zr) (Pb)) ceramics.

The ultrasonic probe 2 is connected to a transmitting / receiving unit 6. The transmitting / receiving unit 6 drives the ultrasonic transducer array of the ultrasonic probe 2 to transmit an ultrasonic beam,
Further, it is for receiving an echo signal received by the ultrasonic transducer array.

FIG. 2 shows a block diagram of the transmission / reception section 6. As shown in the figure, the transmission / reception unit 6 has a signal generation circuit 602. The signal generation circuit 602 generates the above-described multi-tone signal.

The signal generating circuit 602 is, for example, a ROM (read on) storing waveforms of a plurality of frequency component signals.
ly memory). A Shapiro-Rudin phase or a Newman phase is assigned to the plurality of frequency component signals. These frequency component signals are read out at the same time, and D / A (digital to ana)
log) converted and fully added to form a multi-tone signal.

FIG. 3 shows an example of the waveform of the multitone signal to which the Shapiro-Rudin phase is added. FIG. 4 shows an example of the waveform of the multitone signal to which the Newman phase has been added. The signal generation circuit 602 repeatedly generates such a multitone signal at a predetermined cycle.

The output signal of the signal generation circuit 602 is input to the transmission beamformer 606. The transmission beamformer 606 generates a transmission beamforming signal based on the input signal. The transmit beam forming signal is a multi-tone drive signal applied to a plurality of ultrasonic transducers constituting a transmit aperture in the ultrasonic transducer array, and each multi-tone drive signal corresponds to the direction of the ultrasonic beam. The given delay time is given.

The transmission beam forming signal is supplied to a plurality of ultrasonic transducers constituting a transmission aperture through a transmission / reception switching circuit 608. Each of the plurality of ultrasonic transducers to which the drive signal is applied generates a multi-tone ultrasonic wave, and a transmitted ultrasonic beam in a predetermined direction is formed by wavefront synthesis of the ultrasonic waves.

The transmitted ultrasonic echo, that is, the multi-tone echo is received by a plurality of ultrasonic transducers constituting a receiving aperture of the ultrasonic probe 2. The plurality of echo reception signals received by the plurality of ultrasonic transducers are input to the reception beamformer 610 through the transmission / reception switching circuit 608.

The receiving beamformer 610 adds a delay time corresponding to the azimuth of the echo reception sound ray to each of the echo reception signals, adds them all, and converts a multitone echo reception signal along a predetermined sound ray. Form. The portion including the ultrasonic probe 2, the signal generation circuit 602, the transmission beamformer 606, the transmission / reception switching circuit 608, and the reception beamformer 610 is an example of the embodiment of the ultrasonic transmission / reception unit in the present invention.

The transmitting beam former 606 performs sound ray sequential scanning by sequentially switching the direction of the transmitting ultrasonic beam. The reception beam former 610 scans reception of sound rays sequentially by sequentially switching the direction of the reception sound ray corresponding to the transmitted ultrasonic beam. Thereby, the transmission / reception unit 6 performs scanning as shown in FIG. 5, for example. That is,
The ultrasonic beam 202 extending in the z direction from the radiation point 200 scans the fan-shaped two-dimensional area 206 in the θ direction, and performs a so-called sector scan.

When transmitting and receiving apertures are formed by using a part of the ultrasonic transducer array, the apertures are sequentially moved along the array to perform scanning as shown in FIG. 6, for example. Can be.
That is, as the ultrasonic beam 202 emitted from the radiation point 200 in the z direction moves on the linear trajectory 204, the rectangular two-dimensional area 206 is scanned in the x direction, and a so-called linear scan is performed. Will be

Incidentally, the ultrasonic transducer array is
A so-called convex array (convex array) formed along an arc extending in the ultrasonic wave transmission direction.
In the case of y), the radiation point 200 of the ultrasonic beam 202 moves on an arc-shaped trajectory 204 as shown in, for example, FIG. Is scanned in the θ direction, so that a so-called convex scan can be performed.

The transmitting / receiving unit 6 includes a data processing unit 8
It is connected to the. An echo reception signal is sequentially input to the data processing unit 8 from the transmission / reception unit 6 for each sound ray. The data processing unit 8 processes the echo reception signal to generate an image.

The data processing section 8 has a quadrature detection circuit 802 as shown in FIG. The quadrature detection circuit 802 is an example of an embodiment of the quadrature detection means in the present invention.
The quadrature detection circuit 802 performs quadrature detection on the multitone echo reception signal for each frequency component, and obtains an in-phase component i and a quadrature component q for each frequency component. As a result, a complex signal for each frequency component is obtained. These complex signals correspond to the signals of each bin in the frequency domain.

An output signal of the quadrature detection circuit 802 is input to an inverse Fourier transform circuit 804. The inverse Fourier transform circuit 804 performs an inverse Fourier transform on the input signal. The inverse Fourier transform circuit 804 is an example of an embodiment of the transform means in the present invention. Since the signal in the frequency domain is a Fourier transform of the signal in the time domain, the signal in the time domain is restored by the inverse Fourier transform. Therefore, the inverse Fourier transform circuit 804 inversely Fourier-transforms the output signal of one sound ray of the quadrature detection circuit 802, so that the signal of one sound ray in the time domain, that is, the A scope (scope)
e) A signal can be obtained.

The A scope signal is input to the image generation circuit 808. The image generation circuit 808 generates a B-mode image using each instantaneous value of the A scope signal as a luminance value of the image.
The image generation circuit 808 is an example of an embodiment of an image generation unit according to the present invention.

The display section 10 is connected to the data processing section 8. The display unit 10 includes, for example, a graphic display, and the like.
A visible image is displayed based on the image data input from the data processing unit 8.

The transmitting / receiving unit 6, the data processing unit 8 and the display unit 10 are connected to the control unit 12. Control unit 12
Supplies a control signal to each of these sections to control the operation thereof. Further, a state notification signal, a response signal, and the like are transmitted from the controlled units to the control unit 12. Ultrasonic imaging is performed under the control of the control unit 12.

An operation unit 14 is connected to the control unit 12. The operation unit 14 is operated by an operator, and the control unit 12
A desired command or information is input to the device. The operation unit 14 includes, for example, an operation panel (panel) including a keyboard and other operation tools.

The operation of the present apparatus will be described. The operator contacts the ultrasonic probe 2 with a desired part of the subject 100 and operates the operation unit 14 to perform ultrasonic imaging. Imaging is performed under the control of the control unit 12 based on an instruction from the operator. The transmission / reception unit 6 transmits and receives an ultrasonic beam using a multitone signal having a small crest factor, and performs, for example, the sector scan shown in FIG. Since the crest factor of the multi-tone transmitted ultrasonic wave is small, it is hard to be affected by the nonlinearity of the ultrasonic wave propagation, and the ultrasonic wave without waveform distortion can be transmitted. In addition, the small crest factor enhances safety for the living body.

The data processing unit 8 performs quadrature detection of the multitone echo reception signal for each frequency component, performs an inverse Fourier transform on the signal, obtains an A scope signal, and generates a B mode image based on the A scope signal. Since there is no distortion in the waveform of the transmitted ultrasonic wave, the generated image is of high quality. The generated image is displayed on the display unit 10. The high quality of the display image enables accurate diagnosis.

[0039]

As described above in detail, according to the present invention, it is possible to realize an ultrasonic imaging method and apparatus which are not easily affected by the nonlinearity of ultrasonic propagation.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a block diagram of a transmission / reception unit in the device shown in FIG.

FIG. 3 is a waveform diagram of an example of a multitone signal generated by the signal generation circuit shown in FIG. 2;

FIG. 4 is a waveform diagram of an example of a multi-tone signal generated by the signal generation circuit shown in FIG. 2;

FIG. 5 is a conceptual diagram of sound ray scanning by the transmission / reception unit shown in FIG. 2;

FIG. 6 is a conceptual diagram of sound ray scanning by the transmission / reception unit shown in FIG.

FIG. 7 is a conceptual diagram of sound ray scanning by the transmitting / receiving unit shown in FIG.

FIG. 8 is a block diagram of a data processing unit in the device shown in FIG.

[Explanation of symbols]

 2 Ultrasonic probe 6 Transmitter / receiver unit 8 Data processing unit 10 Display unit 12 Control unit 14 Operation unit 100 Subject 602 Signal generation circuit 606 Transmitting beamformer 610 Receiving beamformer 802 Quadrature detection circuit 804 Inverse Fourier transform circuit 806 Image generation circuit

Claims (4)

[Claims] 1. An ultrasonic wave comprising a plurality of frequency components, each phase of which is set so as to reduce a crest factor of a synthesized signal, is transmitted, and an echo thereof is received. And performing an inverse Fourier transform on the orthogonally detected signal and generating an image based on the inversely Fourier transformed signal. 2. An ultrasonic transmitting / receiving means for transmitting an ultrasonic wave composed of a plurality of frequency components, each phase of which is set so as to reduce a crest factor of a synthesized signal, and receiving an echo of the ultrasonic wave; A quadrature detection unit that performs quadrature detection for each of the frequency components, a conversion unit that performs an inverse Fourier transform of the quadrature detected signal, and an image generation unit that generates an image based on the inversely Fourier-transformed signal. An ultrasonic imaging apparatus characterized by the above-mentioned. 3. The ultrasonic imaging apparatus according to claim 2, wherein the phase is a Shapiro-Rudan phase. 4. The ultrasonic imaging apparatus according to claim 2, wherein said phase is a Newman phase.