JPH0620453B2 - Ultrasonic Doppler device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic Doppler device, and more particularly to an ultrasonic Doppler device that accurately displays a state such as the velocity of a moving reflector such as blood flow on a screen.

[Prior Art] An ultrasonic Doppler device that displays an image of a moving state of a reflector that radiates an ultrasonic beam into a living body or the like at a constant repetition period or continuously is known. The velocity distribution state of the reflector is obtained by receiving the reflected echo from the and the Doppler effect received by the reflected echo as the frequency shift of the ultrasonic carrier frequency.

Therefore, by satisfactorily detecting the Doppler shift frequency, it is possible to accurately display an image of the motion state of the blood flow and body flow in the living body, especially the cardiac blood flow, and as this image display,
M mode that shows the change in speed on the time axis with a waveform, spectrum display that displays the spectrum of speed (shift frequency),
Alternatively, there is a B-mode display or the like in which the velocity distribution state is superimposed and displayed on the tomographic image, and image display is performed according to the purpose.

[Problems to be Solved by the Invention] However, since the Doppler effect that an ultrasonic wave receives shows only a change in the velocity of the ultrasonic beam on the radiation, a reflector moving on the beam line is good, but other reflectors are preferable. I couldn't get an accurate measurement of the speed.

That is, as shown in FIG. 5, when the ultrasonic beam is emitted from the probe 12 to the blood vessel 10 and the velocity of the blood flow is obtained, the velocity Va at which the ultrasonic beam can be detected as the Doppler effect is , And V is the velocity of blood flow, Va = Vco
s θ. Therefore, there is a problem that an error occurs in the detected speed by the speed of V-Va, and the speed direction cannot be detected accurately.

Conventionally, as a device for determining the vector velocity of a motion reflector, Japanese Patent Application No. 60-292112 (Japanese Patent Laid-Open No. 62-1 / 1987)
Japanese Patent Laid-Open No. 52437).

SUMMARY OF THE INVENTION The present invention has been made in view of the above conventional problems, and an object thereof is to provide an ultrasonic Doppler device capable of detecting an accurate motion state based on the absolute velocity of a motion reflector. is there.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention images a motion state of a reflector by demodulating a reflected echo signal from a moving reflector to detect a Doppler shift frequency. In the ultrasonic Doppler device to be displayed, one transducer in which a large number of transducers are arranged and a transducer row in the probe are divided into a plurality of transducer groups, and the divided transducer groups are A vector velocity is calculated from a transmitter / receiver unit that transmits and receives ultrasonic waves of different frequencies from different directions to the same site by electronic scanning, and a plurality of Doppler shift frequencies obtained by the transmitter / receiver unit. And a vector velocity calculation unit,
The distance between the plurality of transducer groups is set such that the plurality of ultrasonic beams intersecting at the same portion form a predetermined angle.

[Operation] According to the above configuration, a plurality of transducer groups in one probe are electronically scanned at the same time, whereby a plurality of ultrasonic beams,
For example, two (or three) ultrasonic beams are emitted from different directions toward the same specified portion. In this case, the deflection angle of the two ultrasonic beams is controlled to be a predetermined angle. And 2 from this part
Each of the two reflected echoes is received by the same transducer group,
The Doppler shift frequency is detected for the two received signals.

This Doppler shift frequency information is supplied to the vector velocity calculation unit, where, for example, the vector velocity is calculated from the crossing angle between the two frequency information and the ultrasonic beam, and the two frequency information are calculated as Δf _A , Δf _B , If the angle is Δθ, the absolute velocity V is Thus, the absolute velocity and the moving direction of the moving body can be accurately obtained.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block circuit of a schematic configuration of an ultrasonic Doppler device according to a first embodiment of the present invention. A plurality of transducers are provided inside a probe 12 that emits ultrasonic waves. For example, a device in which 64 or 128 oscillators are arranged is used.

What is characteristic of the present invention is that the ultrasonic beam is angularly deflected by electronic scanning from different directions of the same probe and radiated toward the same site, and this probe 12 is sometimes driven. It is divided into a plurality of transducer groups.
That is, in the present invention, the detection site (sample volume)
Since it is important that the plurality of ultrasonic beams intersecting each other form a predetermined angle, the distance between the plurality of transducer groups is set so as to satisfy the condition that the predetermined intersection angle is formed. Then, this intersection angle is specified from the distance between the transducer groups, that is, the distance between the plurality of ultrasonic beams emitted from the probe 12 and the distance to the detection site (distance from the probe 12). can do. In the first embodiment, a case will be described in which the two transducer groups are divided into two ultrasonic beams.

First, the transmitter 100, which supplies a transmission signal for ultrasonic radiation to the probe 12, includes an oscillation circuit 13, two frequency setting circuits 14a and 14b, and a driving circuit 16, and two types of frequencies. The transmission signal (vibrator excitation signal) can be supplied. In the present invention, it is possible to use one type of ultrasonic waves (frequency) and radiate these at the same time or with a slight time difference, but in order to avoid interference between ultrasonic waves, two types of different frequencies are used in the embodiment. The ultrasonic beams (A and B) are emitted toward the same site.

FIG. 2 shows a state in which the two ultrasonic beams are emitted to the blood vessel (site S) in FIG. 2A, and an enlarged view of the detection site S portion is shown in FIG. 2B. When the ultrasonic beams A and B are radiated toward the point S as shown in the figure,
The intersection angle of the two beams is Δθ. Then, the angle formed by the radiation direction of the ultrasonic beam A and the blood flow direction is θ
Then, the speed detected by each ultrasonic beam A and B is V
a = Vcos θ and Vb = Vcos (θ + Δθ). Therefore, as will be described later, the true velocity (absolute velocity) V and the movement direction θ are obtained from Va, Vb and Δθ.

The receiving unit 200 that receives the echo wave received by the probe 12 includes an electronic scanning receiver 18, two quadrature detectors 20a and 20b, and a phase change of π / 2 in the quadrature detector 20a. Phase shifter 22 and two high-pass filters 26
a, 26b, two low pass filters 28a, 28b,
It is composed of two amplifiers 30a and 30b, two A / D (analog / digital) converters 32a and 32b, and an FFT 34 as a frequency analyzer, and the phase shifter 22 inputs a signal from the oscillation circuit 13. And this receiver 20
0 is the same as the configuration of the conventional ultrasonic Doppler device. The receiving units 200 are provided corresponding to the number of ultrasonic beams emitted simultaneously or with a slight time difference. In the embodiment, the receiving units 2 having the same configuration for the ultrasonic beams A and B are provided.
00A and 200B are provided.

According to this receiving unit 200, the echo signal is treated as a complex signal composed of a real number part and an imaginary number part, whereby F
The shift frequency at the ultrasonic carrier frequency is output from the FT 34, and this shift frequency is a result of the Doppler effect, and therefore indicates the velocity in each ultrasonic beam direction.

Next, the receiving units 200A and 200B are provided with a vector velocity calculation unit 36 for inputting the signals output from them, and the vector velocity of the motion reflector is calculated by this. The calculation of the vector velocity will be briefly described with an equation.

Assuming that the ultrasonic beams A and B are simultaneously emitted to the same site S as shown in FIG. 2, the Doppler shift frequencies Δf _A (for the ultrasonic wave A) and Δf _B (for the ultrasonic wave) for each echo signal are assumed. (For B) is as follows:

Δf _A = (2V / c) focos θ (1) Δf _B = (2V / c) focos (θ + Δθ) (2) where c is the speed of sound in the medium and V is the motion reflector (blood flow). , Θ is the angle between the ultrasonic beam A direction and the blood flow direction, Δθ is the crossing angle of the two ultrasonic beams, f
o is the ultrasonic frequency.

Therefore, in the equations (1) and (2), Δf _A and Δf _B
Is obtained by measurement, and c, V, Δθ, and fo are known values. Therefore, the vector velocity can be calculated from the following equation by the above-mentioned two equations.

That is, (Δf _B −Δf _A ) / Δθ = (2V / c) fo · {cos (θ + Δθ) −cos θ} Δθ = (2V / c) fo · {(cos θ cos Δθ / Δθ) − (sin θsin Δθ / Δθ)-(cos θ / Δθ)} Here, when Δθ is close to 0 radian, Then, substituting these equations into the above equation, Δf _B −Δf
_A = −2Vfo Δθ sin θ / c (3) Then, if θ is deleted from the equations (1) and (3), Therefore, Becomes

Equation (4) is obtained by approximating Δθ to 0 as described above.

Further, in this embodiment, the absolute velocity V can be obtained without approximating to Δθ0.

That is, from the above formula (2), Substituting equation (1) into this, Therefore, Is required. Then, sin ² θ + cos ² θ = 1 (1),
By substituting the equation (5), the unmeasurable θ is erased, and V is represented by Δf _A , Δf _B , c, and fo as shown in the following equation (6).

As described above, since the expression (6) does not use the approximation of Δθ, it holds even if Δθ takes any value.

The embodiment has the above configuration, and its operation will be described below.

First, different frequency signals are transmitted from the transmitter 100 to the probe 12
The ultrasonic beam is supplied to the two transducer groups in the inside, and the ultrasonic beam is radiated to the predetermined site S from the two transducer groups having a predetermined interval. Then, the echo signals are respectively received by the two receiving units 200A and 200B via the same transducer group, and the electronic scanning receiver 1 in the receiving unit 200 is received.
The echo signals received at 8 are quadrature detectors 20a, 2
At 0b, the signals are converted into complex signals having phases different from each other by π / 2, and predetermined signal processing is performed for each of them.

That is, the high pass filter 26 and the low pass filter 2
8, unnecessary signal components and noise components are removed, and this signal is amplified by the amplifier 30 at a predetermined amplification factor.
Then, the output signal of the amplifier 30 is converted into a digital signal by the A / D converter 32 and then supplied to the FFT 34. Since the outputs of the two amplifiers 30a and 30b correspond to the signals (real number part and imaginary number part) that form the complex signal, the FFT 34 calculates the shift frequency of the carrier frequency from the complex signal. .

In this way, the shift frequency signals output from the receivers 200A and 200B are supplied to the vector velocity calculator 36, where the absolute velocity is calculated based on the equation (6).

Since the absolute velocity is supplied to the display device 38, the motion state of the motion reflector is displayed on the display device 38 as a spectrum (or M mode) according to the absolute velocity, whereby the accurate motion state can be grasped.

Also, the vector speed calculator 36 is
The direction of movement can also be measured. That is, with respect to the velocity Va of the ultrasonic beam A, Va = Vcos θ holds, so that the movement direction of the blood flow can be obtained from θ = cos ⁻¹ (Va / V) (7).

This movement direction is suitable for displaying the velocity state on the B-mode tomographic image so that the actual blood flow state can be accurately observed on the image.

Next, a second embodiment of the present invention will be described in which the velocity is detected by three ultrasonic beams.

FIG. 3 shows a state in which three ultrasonic beams are radiated to a predetermined portion of blood flow, and FIG. 4 shows a circuit block in this case.

As shown in FIG. 3, according to the three ultrasonic beams, the motion state of the part S has three velocity values Va and V.
It can be detected by b and Vc.

Therefore, the configuration of FIG. 4 differs from that of FIG. 1 in that the transmitter 100 has three individual wave number setting circuits 14a, 14b,
14c is provided, the drive circuit 16 forms a vibrator excitation signal of a predetermined frequency, and the ultrasonic beam is angularly deflected and radiated toward the detection site S. In this case as well, ultrasonic waves of the same frequency may be used as in the first embodiment, but ultrasonic waves of three different frequencies are also used in the second embodiment to avoid interference.

On the other hand, the receiving unit 200 is also provided with three receiving units 200A, 200B, and 200C corresponding to the three ultrasonic beams, and the internal configuration thereof is the same as that of the first embodiment.

According to the second embodiment as described above, there is an advantage that the vector velocity can be accurately measured. That is, the larger the number of data, the more reliable the calculated value is. For example, when two ultrasonic beams are used, one of the detection speeds is a small value which is unsuitable as a measured value depending on the direction of the motion reflector. Therefore, the detection accuracy of the vector speed may be deteriorated. According to the second embodiment, such a point can be eliminated and the speed can be accurately detected.

[Effects of the Invention] As described above, according to the present invention, ultrasonic waves of a plurality of different frequencies are radiated from one probe to a same portion at a predetermined deflection angle. There is an advantage that the absolute velocity of the body or the vector velocity including the motion direction can be measured and displayed, and information useful for image diagnosis can be provided.

In addition, since the distance between the plurality of transducer groups can be changed so that the ultrasonic beam transmitted / received to / from the detection portion on the reflector forms a predetermined angle, it is assumed that the transducer group and the detection portion are separated from each other. Even if there is an obstacle in between, it is possible to avoid the obstacle and transmit / receive the ultrasonic beam to / from the detection site.

Further, according to the present invention, since three or more ultrasonic beams can be emitted to the detection site, the number of data used for calculation can be increased, and therefore, the vector velocity can be measured more accurately. Become.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing a schematic configuration of an ultrasonic Doppler device according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram showing a detection state when two ultrasonic beams are emitted, and FIG. Is an explanatory view showing a detection state when three ultrasonic beams are emitted, FIG. 4 is a circuit block diagram showing a schematic configuration of a second embodiment of the present invention, and FIG. 5 is an explanation showing a conventional speed detection state. It is a figure. 12 ... Probe 14 ... Frequency setting circuit 16 ... Driving circuit 18 ... Electronic scanning receiver 34 ... FFT 36 ... Vector velocity calculation unit 38 ... Display unit 100 ... Transmission unit 200 ... Reception unit .

Claims (1)

[Claims] 1. An ultrasonic Doppler device for displaying the motion state of a reflector by demodulating a reflection echo signal from the moving reflector to detect the Doppler shift frequency, and a plurality of transducers are arranged. One probe and a transducer row in this probe are divided into a plurality of transducer groups, and the divided transducer groups are electronically scanned to obtain ultrasonic beams of different frequencies from different directions. A transmitter / receiver unit that transmits and receives waves to and from the same site respectively, and a vector velocity calculator that calculates a vector velocity from a plurality of Doppler shift frequencies obtained by the transmitter / receiver unit. The ultrasonic Doppler device is characterized in that the distance is set so that the plurality of ultrasonic beams intersecting at the same portion form a predetermined angle.