JPH043221B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in an ultrasonic blood flow observation device that uses ultrasound to obtain blood flow information in a living body for use in living body diagnosis.

[Technical Background of the Invention] An ultrasonic blood flow observation device using the ultrasonic Doppler effect is based on the following operating principle. That is, the ultrasonic wave of frequency c transmitted to the bloodstream in the living body is scattered by the flowing blood cells and causes a Doppler shift of frequency fd, so the frequency f of the received ultrasonic wave is = c +
d. Since d reflects the blood flow velocity v as shown in equation (1) below, by detecting d,
Information on blood flow velocity v can be obtained non-invasively.

d2vcosθ/c・c...(1) v; Blood velocity θ; Angle c that the ultrasound beam makes with the blood vessel; Sound velocity Here, the above d is obtained by phase detection of the echo signal, and is usually used as a detector. 90 different phases
A quadrature phase detector that can obtain a signal X(t) containing a signal component of d is often used. and,
Two signals from the quadrature phase detector, namely X(t)
The imaginary part of Im{X(t)}, the real part of X(t) Re{X
(t)} are output respectively. Here, signal X(t)
To approximately find the average d of d, use the following formula (2)
A method called the autocorrelation method is used as shown in the figure below.

C(τ)=1/N−τ _N- 〓 〓 ⁱ⁼¹ X _i X ^* _i +τ ……(2) Xi; Discrete representation of X(t) Corresponding to +jIm{X(t)}, let Xi=Re{Xi}+jIm{Xi}xi +jyi.

*; indicates complex conjugation.

N: Total number of data points (number of samples) τ: Number of steps to shift when taking autocorrelation, generally called "lag".

C(τ); Autocorrelation function Here, if we expand the autocorrelation function C(τ), we get C(τ)=1/N−τ _N- 〓 〓 ⁱ⁼¹ (x _i + jy _i ) (x _i+1 −jy _i+1 ) =1/N−τ _N- 〓 〓 ⁱ⁼¹ (x _i・x _i+1 +y _i・y _i+1 )+j1/N−τ _N− 〓 〓 ⁱ⁼¹ (x _{i +1} ·y _i −x _i ·y _i+1 ) ≡Re{C(τ)}+jIm{C(τ)}, and furthermore, it can be obtained as shown in equation (3) below.

=r/2π・tan ^-1 Im{C(τ)}/Re{C
(τ)}...(3) r: Repetition frequency of ultrasonic pulse (referred to as rate frequency) When calculating d using the above formula (3), -π/2< tan ^-1 <π/2 Therefore, if the above equation (3) is used as is, only the range −r/4<<r/4 can be expressed.

Therefore, as shown in Figure 2, r/4<<r/
4 can be expressed by detecting Re{C(τ)}<0, Im{C(τ)}>0, and −
It is generally possible to express the entire region by detecting Re{C(τ)}<0, Im{C(τ)}<0 to express the region r/2<<-r/4. It is being done.

Calculation by the autocorrelation method can be performed in real time using a high-speed digital calculation method, so by scanning the ultrasound beam transmitted from the ultrasound probe, the scan plane of the ultrasound beam can be It is possible to display the flow of blood in the observation area in real time.

[Problems with the background art] Conventionally, when calculating by the above autocorrelation method, -r/2<<r/2 can be calculated, but Re{
C (τ)}=0, the value of d cannot be obtained from equation (3) and has the drawback of being undefined. For this reason, unnatural methods such as setting d=0 when Re{C(τ)}=0 have been taken, making it impossible to provide highly accurate diagnostic information.

[Object of the invention] The present invention has been made based on the above circumstances, and
The purpose is to provide an ultrasonic blood flow observation device that eliminates the problems that occur when using the autocorrelation method and makes it possible to obtain highly accurate blood flow information.

[Summary of the Invention] In order to achieve the above object, an ultrasonic blood flow observation device according to the present invention transmits and receives ultrasonic pulses within a living body to detect frequency shift information due to the Doppler effect, and detects frequency shift information due to the Doppler effect. In an ultrasonic blood flow observation device that calculates the average flow velocity of the autocorrelation function based on the frequency shift information using the autocorrelation method, when the real part of the autocorrelation function in the autocorrelation method is zero, the value of the imaginary part of the autocorrelation function is zero. The present invention is characterized by comprising means for determining the above-mentioned average flow velocity based on.

[Embodiments of the Invention] The ultrasonic blood flow observation device according to the present invention will be described below as a first embodiment.
An explanation will be given according to an embodiment shown in the figure.

In FIG. 1, reference numeral 1 denotes an ultrasonic probe for sector scanning, for example, in which minute ultrasonic transducers are arranged, and is used to transmit and receive ultrasonic waves to and from a living body P. Reference numeral 2 denotes a wave transmitting/receiving circuit that applies excitation pulses to the ultrasonic probe 1 and obtains received echo signals. Reference numeral 3 denotes a quadrature phase detection circuit which performs quadrature phase detection on the echo signal from the transmitting/receiving circuit 2 and outputs a real part component Re{Xi} and an imaginary part component Im{Xi}, respectively.

4 is the real part component Re from the quadrature phase detection circuit 3
{Xi}, imaginary component Im {Xi}, respectively, into digital signals.
C). 5 takes in the real part component Re{Xi} and the imaginary part component Im{Xi} which were digitized by the A/D-C4, and based on the above formula (2), the real part signal S ₁ = of the autocorrelation function of Xi is obtained. This is a correlation processing circuit that calculates and obtains Re{C(τ)} and imaginary part signal S ₂ =Im{C(τ)} and outputs them respectively.

Reference numeral 6 denotes an arithmetic circuit composed of a determining section 6A, a first arithmetic section 6B, and a second arithmetic section 6C. The determining unit 6A of the arithmetic circuit 6 takes in the real part signal S ₁ =Re{C(τ)} and determines whether this is zero (signal S ₃ ). In addition, the first calculation unit 6
B is the real part signal S ₁ =Re{C(τ)} and the imaginary part signal
Take in S ₂ = Im {C(τ)} and obtain the imaginary part signal S ₂ = Im
Check the polarity of {C(τ)} (signal S ₄ ), and further check the polarity of real part signal S ₁ =Re{C(τ)} (signal S ₅ ) Im{C
(τ)}/Re{C(τ)} (signal S ₆ ). Furthermore, the second calculation unit 6C takes in the outputs of the determination unit 6A and the first calculation unit 6B, and calculates d by executing the calculation of the above equation (3).

Reference numeral 7 denotes a display system that displays video information of d from the arithmetic circuit 6 and the blood flow velocity v based on the above equation (1) in real time.

Next, the operation of this embodiment configured as described above will be explained.

In FIG. 1, a power source (not shown) is turned on and the ultrasound probe 1 is brought into contact with the observation site of the living body P. Ultrasonic pulses are transmitted from the ultrasonic probe 1 while scanning by the transmitting/receiving circuit 2, and the transmitted ultrasonic pulses have a Doppler shift d that reflects the velocity v of blood flow inside the object. is received by the wave transmitting/receiving circuit 2. Doppler shift d, which is the output of the transmitter/receiver circuit 2
The echo signal including .

These Re{Xi} and Im{Xi} are input to the A/D-C4, and a digitized version of Re{Xi} and Im{Xi} is output. Digitized Re{Xi},
Im{Xi} is input to the correlation processing circuit 5, and the real part Re{C(τ)} and the imaginary part Im of the autocorrelation function of Xi
{C(τ)} is calculated and output as described above.

Then, the signal S ₁ of Re{C(τ)}, Im{C(τ)},
S ₂ is input to the arithmetic circuit 6.

Here, according to Fig. 2, when Re{C(τ)=0, d is r/4 or -r/4, and when = r/4, Im {C(τ)}>0, When d=-r/4, Im{C(
τ)} <0.

Therefore, when Re{C(τ)}=0, at the same time
By detecting the polarity of Im{C(τ)}, the value of can be determined as ±r/4. That is, the determination unit 6A determines that Re{C(τ)}=0, and when Re{C(τ)}=0, for example, 1 (positive logic H level), Re{C(τ)}≠0. For example, 0 if
(positive logic L level) signal _S3 is output.

Further, the signal of Re{C(τ)} is input to the first calculation unit 6B together with the signal of Im{C(τ)}, and the signal of Im{C(τ)} is input to the first calculation unit 6B.
(τ)}/Re{C(t)} operation result S ₆ and Im{C
(τ)} polarity signal S ₄ and Re{C(τ)} polarity signal S ₅ are output. Here, the polarity signal outputs, for example, 0 when it is positive, and outputs, for example, 1 when it is negative. output signal
S ₃ , S ₄ , S ₅ , and S ₆ are input to the second calculation unit 6C, and the second calculation unit 6C refers to the signal S ₃ and calculates Re{C
(τ)}≠0, the signal _S6 Im{C(τ)}/Re
The calculation result of {C(τ)} and Im of each of the signals S ₄ and S ₅
Due to the polarity signals of {C(τ)} and Re{C(τ)}, d
Calculate.

Here, Re{C(τ)}=0 means that the signal S ₃
When indicated by the signal, the second calculation unit 6C outputs the signal
Based on the polarity of Im{C(τ)} of S ₄ , Im{C
When (τ)}>0, it outputs =r/4, and when Im{C(τ)}<0, it outputs =-r/4.

d thus obtained by the arithmetic circuit 6 is displayed as an image by the display system 7.

As described above, according to this embodiment, the value of d does not become undefined even when Re{C(τ)}=0, so it is possible to obtain highly accurate blood flow information.

The present invention is not limited to the above embodiments. For example, the input to the second calculation unit 6C is changed from the determination unit 6A to the input from the first calculation unit 6B as Re{C(τ)}=
0 determination result, polarity of Re{C(τ)} and Im{C(τ)}, Im{C(τ)}/Re{C(τ)
}
, but other combinations can also be calculated as Re{C
The present invention is not limited to this, as long as the configuration can determine the polarity of Im{C(τ)} when (τ)}=0. In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the present invention, when the real part of the autocorrelation function in the autocorrelation method is zero, it is provided with means for determining the real part based on the value of the imaginary part. An ultrasonic blood flow observation device capable of obtaining accurate blood flow information can be provided.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the ultrasonic blood flow observation device according to the present invention, and FIG. 2 is a diagram for explaining the problems of the autocorrelation method. 1... Ultrasonic probe, 2... Transmission/reception circuit, 3...
... Quadrature phase detection circuit, 4 ... Analog/digital converter, 5 ... Correlation processing circuit, 6 ... Arithmetic circuit,
6A...determination section, 6B...first calculation section, 6C...
...Second calculation unit, 7...Display system.

Claims (1)

[Claims] 1 Ultrasonic pulses are transmitted and received within a living body to detect frequency shift information due to the Doppler effect, and the average flow velocity of blood flow in the living body is calculated from the frequency shift information using an autocorrelation method. An ultrasonic blood flow observation device, characterized in that the ultrasound blood flow observation device comprises means for determining the average flow velocity based on the value of the imaginary part when the real part of the autocorrelation function in the autocorrelation method is zero. Device.