JPH06142101A - Ultrasonic doppler device - Google Patents

Abstract

PURPOSE:To save trouble of adjustment, and also, to suppress a mirror image irrespective of a frequency of an ultrasonic probe to be used. CONSTITUTION:The device is provided with a DSP 7 for calculating an amplitude ratio A related to component signal I1, Q1 obtained by eliminating a DC component from component signals I, Q, and a sine component sintheta of a phase shift theta, calculating a new component signal (q) by (q)={(Q/A)-I.sintheta}/costhetao, basing on the component signals I, Q and the calculated ratio A, and the sine component sintheta of the phase shift theta, and substituting the component signal Q for its component signal (q). From the component signals I, (q), a Doppler spectrum is generated by an FFT analyzing part 9. In such a way, at the time of delivery from a plant and at the time of periodical inspection, an operator can save trouble of adjustment. A mirror image can always be suppressed irrespective of an ultrasonic probe to be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic Doppler device, and more particularly to an ultrasonic Doppler device for obtaining a Doppler spectrum by performing FFT analysis after orthogonal detection of ultrasonic echo signals.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of an essential part of an example of a conventional ultrasonic Doppler device. In this ultrasonic Doppler device 51, the ultrasonic echo signals obtained by the ultrasonic probe 2 and the beam former 3 are input to the quadrature detection unit 54. The quadrature detection unit 54 generates component signals I and Q from the ultrasonic echo signal.

The component signals I and Q are input to an FFT analysis section 9 through a low pass filter 5, an A / D converter 6 and a wall filter 8. The FFT analysis unit 9 frequency-analyzes the component signals I and Q to generate Doppler spectrum data.

The DSC 10 converts the Doppler spectrum data into image data. The CRT 11 performs Doppler spectrum display based on the image data.

By the way, if the amplitudes of the component signals I and Q output from the quadrature detector 54 are not uniform or the phase difference is deviated from 90 °, a mirror image is generated. For example, in FIG. 3, D is the Doppler spectrum and M is the mirror image. In order to suppress the generation of this mirror image, conventionally, an operator uses a single tone generator 62 (see FIG. 2) to send a single tone signal of an appropriate frequency to the quadrature detection unit 54 at the time of factory shipment or regular inspection. Input and quadrature detector 54
Operate the semi-fixed volume control on the
The Q amplitudes are adjusted and the phase difference is adjusted to 90 °. FIG. 4 conceptually shows image data when a single tone signal is input to the quadrature detection unit 54. When a single tone signal is input, a Doppler spectrum D is obtained at a speed corresponding to the frequency, and a mirror image M that is easy to specify is generated near the speed of the opposite sign to the speed.

[0006]

In the above-mentioned conventional ultrasonic Doppler device 51, the quadrature detection unit 5 uses the single tone generator 62 to output a single tone signal of an appropriate frequency.
4 and the semi-fixed potentiometer provided in the quadrature detection unit 54 is operated to make the adjustment, so that there is a problem that the adjustment is troublesome. Further, the adjustment using the semi-fixed volume cannot be performed for all different frequencies of the plurality of ultrasonic probes, and thus adjustment is performed for only one typical frequency. Therefore, when an ultrasonic probe having a frequency different from the frequency used for the adjustment is used, the adjustment is incomplete and the mirror image cannot be suppressed.

Therefore, an object of the present invention is to obtain the component signals I,
Even if the amplitude of Q is not uniform or the phase difference does not reach 90 °, it is compensated by calculation, eliminating the trouble of adjustment and suppressing the mirror image regardless of the frequency of the ultrasonic probe used. The purpose of the present invention is to provide an ultrasonic Doppler device.

[0008]

According to a first aspect of the present invention, a quadrature detector generates two component signals I and Q, and an FFT analyzer generates a Doppler spectrum from these component signals I and Q. In the ultrasonic Doppler device,
DC component calculating means for calculating the DC components of the component signals I and Q from the time average of the two component signals I and Q, and the time integral value I2 of the square of the component signal I1 obtained by subtracting the DC component from the component signal I. Then, an amplitude ratio calculating means for dividing the squared time integrated value average Q2 of the component signal Q1 obtained by subtracting the direct current component from the component signal Q to obtain the square root of the quotient as the amplitude ratio A, and the component signal I1. The time integral value of the product of the component signal Q1 is divided by the square root of the product of the time integral value I2 and the time integral value Q2, and the quotient is the sine component s of the phase shift θ.
Phase deviation calculating means for in θ and the component signals I and Q
Based on the amplitude ratio A and the sine component sin θ of the phase shift θ, a new component signal q is calculated by q = {(Q / A) −I · sin θ} / cos θ (1), and the component signal q According to the present invention, there is provided an ultrasonic Doppler device characterized in that the arithmetic means for replacing the component signal Q is provided between the quadrature detection section and the FFT analysis section.

In a second aspect, the present invention is, in addition to the above configuration, a storage means for storing a set of an amplitude ratio A and a sine component sin θ of a phase shift θ corresponding to a plurality of different ultrasonic probes, and use. Amplitude ratio A corresponding to the ultrasonic probe
An ultrasonic Doppler apparatus further comprising: a selection unit configured to extract a set of a sine component sin θ of the phase shift θ from the storage unit and use the set for calculation.

[0010]

When the amplitude of the component signal Q with respect to the component signal I is A times and the phase difference is (90 ° + θ), I = cosωt (2) Q = Asin (ωt + θ) (3) By modifying equations (2) and (3), sinωt = {(Q / A) -I · sinθ} / cosθ (4). If q = sinωt (5), then q is considered to be a component signal having the same amplitude as the component signal I and a phase difference of 90 °.

In the ultrasonic Doppler device according to the first aspect of the present invention, the component signals I and Q are not inherently included in the component signals, but a DC component that may be included in the component signals I and Q in terms of hardware may be included. In consideration of this, the DC component calculating means calculates the DC component on the component signals I and Q from the time average of the two component signals I and Q. That is, the calculated DC component is I
If DC and QDC are used, I-IDC = cosωt (2a) and Q-QDC = Asin (ωt + θ) (3a) can be expressed by the above equations (2) and (3).

The amplitude ratio calculating means is a square root of the time integral value I2 of the square of the component signal I1 obtained by subtracting the DC component from the component signal I, and the component signal Q obtained by subtracting the DC component from the component signal Q.
The square root of the time integral value Q2 of 1 2 is divided. This is the calculation of √ (Q2) / √ (I2) = √ (∫ {Asinωt} ² dt) / √ (∫ {cosωt} ² dt) from the equations (2a) and (3a). If is set appropriately, the quotient becomes the amplitude ratio A. The phase shift calculating means is configured to calculate the component signal I.
The time integral value of the product of 1 and the component signal Q1 is divided by the square root of the product of the time integral value I2 and the time integral value Q2. This is the calculation of {∫cosωt · Asin (ωt + θ) dt} / √ ([∫ {cosωt} ² dt] [∫ {Asinωt} ² dt]) from the equations (2a) and (3a), and sin ( ωt + θ) = sinωt · cosθ + cosω
If t · sin θ is taken into consideration and the integration time is set appropriately, the quotient becomes the sine component sin θ of the phase shift θ.

The calculating means replaces the component signal Q with the new component signal q obtained by the calculation of the equation (1) based on the component signals I and Q, the amplitude ratio A and the sine component sin θ. Therefore, the Doppler spectrum is generated by the FFT analysis unit from the component signals I and q. From the above equations (4) and (5), the component signal q has the same amplitude as the component signal I and has a phase difference of 90 °. Therefore, the mirror image can be suppressed. Further, the component signals I and Q do not have to have the same amplitude and the phase difference does not have to be 90 °, so that the labor of adjustment can be saved.

From the above equations (2a) and (3a), (1)
Q = {(Q1 / A) −I1 · sin θ} / cos θ (1a) corresponding to the equation is obtained, but considering that the DC component is invalidated in the FFT analysis unit, the component signal q in the calculation means is obtained. Equation (1) is sufficient for calculating The time for averaging in the DC component calculating means, the integration time in the amplitude ratio calculating means, and the integration time in the phase shift calculating means are on the order of several kHz of the component signals I and Q. Therefore, good accuracy can be obtained in a short time.

In the ultrasonic Doppler device of the present invention according to the second aspect, the amplitude ratio A and the phase shift θ used in the equation (1) are used.
The set of the sine component sin θ of the above is stored in correspondence with a plurality of different ultrasonic probes, taken out according to the ultrasonic probe to be used, and used in the calculation of the equation (1). Therefore, the mirror image can be suppressed regardless of the frequency of the ultrasonic probe used.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail based on the embodiments shown in the drawings. The present invention is not limited to this. FIG. 1 is a block diagram of essential parts of an embodiment of the ultrasonic Doppler device of the present invention. The same components as those of the conventional device 51 are designated by the same reference numerals. In this ultrasonic Doppler device 1, the ultrasonic echo signals obtained by the ultrasonic probe 2 and the beam former 3 are detected by the quadrature detection unit 4 to extract the component signals I and Q. The quadrature detection unit 4 is not provided with an operation component such as a semi-fixed volume. This is because adjustment is unnecessary. The component signal I
Is input to the DSP 7 through the low pass filter 5 and the A / D converter 6. Further, it is input to the FFT analysis unit 9 through the low pass filter 5, the A / D converter 6 and the wall filter 8. The component signal Q is
D through the low-pass filter 5 and A / D converter 6
Input to SP7.

In the DSP 7, based on the component signals I and Q, the predetermined amplitude ratio A, and the sine component sin θ of the phase shift θ, q = {(Q / A) −I · sin θ} / cos θ (1) The component signal q is calculated. Then, the component signal q is input to the FFT analysis unit 9 through the wall filter 8. Note that the amplitude ratio A and the sine component si of the phase shift θ are
nθ is obtained in advance and stored. A method for obtaining the sine component sin θ of the amplitude ratio A and the phase shift θ will be described later.

The FFT analysis section 9 carries out frequency analysis based on the component signals I and q to obtain Doppler spectrum data.
The DSC 10 converts the Doppler spectrum data into image data and stores it in the frame memory. CRT1
1 performs Doppler spectrum display based on the image data stored in the frame memory in the DSC 10.

Next, the sine component s of the amplitude ratio A and the phase shift θ
The operation for obtaining inθ will be described. First, the ultrasonic probe 2 and the beam former 3 obtain ultrasonic echo signals for the common carotid artery, the ventricular outflow tract, etc., in which the blood flow direction is only one direction, and input to the quadrature detection unit 4. Alternatively, for example, a (pseudo) ultrasonic echo signal obtained by continuously tapping the ultrasonic probe 2 at a time interval of about 1 sec is obtained and input to the quadrature detection unit 4.

The DSP 7 time-averages the component signal I input from the quadrature detector 4 during a predetermined period to obtain a DC component IDC. Also, the component signal Q input during the same period
Is averaged over time to obtain the DC component QDC. A component signal I1 obtained by subtracting the DC component IDC from the component signal I input during the next predetermined period is obtained, squared, time-integrated, and squared to obtain a time integrated value I2. Further, a component signal Q1 obtained by subtracting the DC component QDC from the component signal Q input during the same period is obtained, squared, integrated with time, squared, and integrated with time Q.
Set to 2. Then, the time integration value Q2 is divided by the time integration value I2, and the square root of the quotient is set as the amplitude ratio A. Further, from the component signals I and Q input during the next predetermined period, the component signal I
1, Q1 are obtained, these component signals I1, Q1 are multiplied, and time integration is performed to obtain a time integrated value. Then, the time integrated value is calculated as the time integrated value I1 and the time integrated value Q2.
It is divided by the square root of the product of, and the quotient is taken as the sine component sin θ of the phase shift θ. In this way, a set of the amplitude ratio A and the sine component sin θ of the phase shift θ suitable for the ultrasonic probe 2 is obtained. Since the frequencies of the component signals I and Q are on the order of several kHz, the predetermined period is 1
Sufficient accuracy can be obtained in about sec. If the predetermined period is about 1 sec, the time required to obtain the sine component sin θ of the amplitude ratio A and the phase shift θ is about 3 sec.

Also, if the ultrasonic probe 2 is replaced with a different ultrasonic probe, a set of the amplitude ratio A and the sine component sin θ of the phase shift θ suitable for the different ultrasonic probe can be obtained. A pair of the amplitude ratio A and the sine component sin θ of the phase shift θ is obtained for all of a certain ultrasonic probe and stored in the DSP 7, and the sine of the amplitude ratio A and the phase shift θ suitable for the ultrasonic probe actually used is obtained. The set with the component sin θ may be extracted and used in the calculation.

[0022]

According to the ultrasonic Doppler device of the present invention,
The mirror image can be suppressed without the need for the operator to adjust the quadrature detection unit at the time of factory shipment or regular inspection. In addition, the mirror image can always be suppressed regardless of the frequency of the ultrasonic probe used.

[Brief description of drawings]

FIG. 1 is a block diagram of essential parts of an embodiment of an ultrasonic Doppler device of the present invention.

FIG. 2 is a principal block diagram of an example of a conventional ultrasonic Doppler device.

FIG. 3 is an exemplary diagram of a Doppler spectrum and a mirror image.

FIG. 4 is an exemplary diagram of a Doppler spectrum and a mirror image for a single tone.

[Explanation of symbols]

 1 Ultrasonic Doppler device 4 Quadrature detection unit 7 DSP 9 FFT analysis unit 10 DSC D Doppler spectrum M Mirror image

Claims (2)

[Claims] 1. A quadrature detection section for generating two component signals I and Q.
In the ultrasonic Doppler device that generates a Doppler spectrum from the component signals I and Q by the FFT analysis unit, a DC component that calculates the DC component of the component signals I and Q from the time average of the two component signals I and Q. A component calculating means and a squared time integral value I2 of a component signal Q1 obtained by subtracting a DC component from the component signal Q by a squared time integral value I2 of a component signal I1 obtained by subtracting a DC component from the component signal I. Of the product of the component signal I1 and the component signal Q1, and the time integral value of the time integral value I2 and the time integral value Q2. Divide by the square root of the product and the quotient is the sine component s of the phase shift θ.
Phase deviation calculating means for in θ and the component signals I and Q
Based on the amplitude ratio A and the sine component sin θ of the phase shift θ, a new component signal q is calculated by q = {(Q / A) −I · sin θ} / cos θ, and the component signal q is used to calculate the component An ultrasonic Doppler device characterized in that an arithmetic means for replacing the signal Q is provided between the quadrature detection section and the FFT analysis section. 2. The ultrasonic Doppler device according to claim 1, wherein an amplitude ratio A corresponding to a plurality of different ultrasonic probes.
And a sine component sin θ of the phase shift θ, and a set of the amplitude ratio A corresponding to the ultrasonic probe to be used and the sine component sin θ of the phase shift θ, which are taken out from the storage means and used for the calculation. An ultrasonic Doppler device further comprising a selecting means.