JPH03215255A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To enhance the measuring accuracy of a flow rate and the reliability of the title apparatus by mounting a means calculating a plurality of the beam angles formed by a plurality of different ultrasonic beam directions and a blood flow direction, and an operation means calculating the effective component and ineffective component of blood flow velocity and a blood flow rate from those beam angles and the max. blood flow velocity. CONSTITUTION:By moving an ultrasonic probe 1 along the surface of a living body, the angles theta1, theta2 formed by a blood flow direction and ultrasonic beams are calculated by a controller 10 and an operation circuit 50 calculating the max. flow velocity value of an effective blood flow component wherein an ineffective blood flow component is removed on the basis of the calculated angles and the apparent max. flow velocities at said angles is provided. At first, the Doppler max. velocity of the angle formed by the ultrasonic beam and blood flow in the surface of a living body is detected by an FFT 5C. Next, the ultrasonic probe 1 is moved along the surface of the living body to detect the Doppler max velocity of the angle formed by ultrasonic beam and blood flow. The operation circuit 5D inputs the angles theta1, theta2 from the controller 10 and inputs the max. velocity from the FFT 5C to simultaneously display the effective component, the ineffective component and a blood flow rate and the B-mode image from an envelope detection circuit 4A on a TV monitor 6B.

Description

Detailed Description of the Invention [Purpose of the Invention (Industrial Application Field) The present invention relates to ultrasonic diagnostics capable of detecting or measuring the speed of a moving reflector such as blood flow within the heart or blood vessels. Regarding equipment.

(Prior Art) Among ultrasonic diagnostic devices, a number of Doppler blood flow measurement devices have been developed because they can non-invasively measure the blood flow velocity in a living body. Here, the configuration and operation of one of the pulse Doppler blood flow measurement devices that have been put into practical use will be explained. This device non-invasively measures blood flow velocity at any set point within a living body using the pulsed Doppler method.

That is, the ultrasonic Doppler method utilizes the ultrasonic Doppler effect in which when an ultrasonic wave is reflected by a moving object, the frequency of the reflected wave shifts in proportion to the moving speed of the object. Specifically, by transmitting ultrasonic rate pulses to a living body and obtaining the frequency deviation due to the Doppler effect from the phase change of the reflected wave echo, we can obtain motion information of a moving object at the depth position where the echo was obtained. I can do it.

According to this ultrasonic Doppler method, it is possible to know the direction of the flow of blood at a position in the living body and the state of the flow, whether it is turbulent or regular.

Next, this ultrasonic diagnostic apparatus will be explained. First, the transmitter/receiver circuit is driven to repeatedly transmit ultrasound pulses from the ultrasound probe to the bloodstream within the body of the subject a predetermined number of times. Then, the center frequency fc of the transmitted ultrasound beam is scattered by the flowing blood cells and subjected to Doppler shift, resulting in the frequency fd
The transmitter/receiver circuit changes the reception frequency f−fc+f
d is received. Note that the frequencies fc and fd are as shown in the following equations.

fd-2vcos θ φ f c/C where, V:
Blood flow velocity θ: Angle C between the ultrasound beam and the blood vessel: Sound velocity Since this frequency fd is a function of the blood flow velocity V, if the Doppler shift frequency fd is detected and processed, the blood flow A flow velocity V can be obtained.

In addition, in the ultrasonic Doppler method, the maximum deviation frequency fdtiaX is determined from the maximum blood flow velocity V■aX among the temporal changes in blood flow velocity, as shown in FIG. Further, the power relative to the blood flow velocity is as shown in FIG. Then, using the tomographic image shown in FIG. 9, the angle θ between the blood vessel direction P and the ultrasound beam direction and the tube diameter 2' are measured. Also, if the range gate width is adjusted to the blood vessel and this length is g, then 2r-1c
It becomes osθ.

Furthermore, the blood flow Q that is clinically desired is: Q-v A-vmax /2 πr2 However, vsax
−cafdsax/(2f@cosθ), where f is the ultrasound frequency and C is the speed of sound. Here, the angle is corrected by COSθ.

(Problem to be solved by the invention) However, as shown in Fig. 10, as the angle θ increases, the maximum flow velocity value V It comes to show. This has caused a problem in that the blood flow Q is overestimated.

The cause of this is thought to be the influence of turbulence components. FIGS. 11 and 12 are diagrams showing this type of blood flow state. Blood flow has two states: laminar flow shown in FIG. 11 and turbulent flow shown in FIG. 12. The laminar flow is v (x) − vmax (1 − (x/R) 2
) is displayed. Here, R is the pipe diameter (radius).

Moreover, the turbulent flow is v (x) - vmax (1 - (x/R))
”.

is displayed. Here, n changes depending on the Reynolds number. R is the pipe diameter (radius). The flow at this time is v (x
) There are other things besides directions.

Next, the conditions for the occurrence of the turbulent flow are: (1) When the Raynoise number RD increases Ro-4Qρ/πDη where Q is the flow rate ρ is the fluid density D is the tube diameter (diameter), and η is the fluid viscosity.

(2) When the condition inside the pipe changes entrance area Bent pipe (development of secondary flow) (3) When time changes pulsatile flow is possible.

In this way, many blood vessels can be considered to have turbulent flow, and this turbulence synthesizes the velocity component in the direction along the blood vessel and the blood flow component in other directions, so the maximum flow velocity value V la
X was apparently larger.

Further, as shown in FIG. 13, the flow in the blood flow direction is defined as Vo. This V. is the velocity that contributes to the flow rate and is a function of the position X in the pipe radial direction. Further, the velocity during laminar flow is VQ mVIaX (1-(x/R) 2) as described above, and the velocity during turbulent flow is Vo -vmax (1-x/R) 1''.

Here, v wax is the maximum value of v0.

Turbulent flow includes a component Vr that moves in random directions within a microvolume and a component V that contributes to the flow rate. Think about it separately.

Overall, the speed is V. When viewed microscopically, the scatterers (red blood cells) move arbitrarily, but statistically they are balanced, so they are not biased. In other words, it appears to be coming towards you at a speed of vr from any angle.

Therefore, the Doppler detection speed on the ultrasound beam is V as shown in FIG. cos θ 0 V' becomes. Then, when this is corrected for the angle, Vmax − (V. co
sθ V r ) / c o sθ■V6+Vr/
cos θ. That is, as shown in FIG. 15, the component V', which is ineffective for the flow rate, increases at a rate of 1/cos θ as the angle θ increases.

When the angle θ increases in this way, the measured value VlaX will show a large value, causing an overestimation of the flow rate Q, and an error with the value measured under different angle conditions, resulting in poor reproducibility. It was getting scarce.

Therefore, the purpose of the present invention is to
It is an object of the present invention to provide an ultrasonic diagnostic device that improves the accuracy of flow rate measurement and improves the reliability of the device without causing measurement errors in blood flow velocity.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention takes the following measures. The present invention is an ultrasonic diagnostic apparatus that transmits and receives ultrasonic waves to and from a subject using an ultrasonic probe, extracts a Doppler signal from the received signal, and measures blood flow based on this Doppler signal. In this method, there is a means for determining a plurality of beam angles formed by different ultrasound beam directions and blood flow directions, and a maximum blood flow velocity for each beam angle obtained by this means is detected, and from these beam angles and maximum blood flow velocity. The present invention is characterized by comprising a calculating means for determining an effective component, an inactive component of blood flow velocity, and the blood flow rate.

(Effects) By taking such measures, the following effects are achieved. A plurality of beam angles formed by different ultrasound beam directions and blood flow directions are determined, the maximum blood flow velocity for each beam angle is detected, and the effective component of the blood flow velocity is calculated from these beam angles and maximum blood flow velocity using a calculation means. , the inactive component and the blood flow rate, even if the beam angle becomes large, the accuracy of blood flow measurement can be improved without causing an error in measuring the blood flow velocity. Furthermore, since the flow status of active ingredients, inactive ingredients, etc. can be displayed, the reliability of the device can be improved.

(Example) Specific examples of the present invention will be described below. Fig. 1 is a schematic block diagram showing an embodiment of the ultrasonic diagnostic apparatus according to the present invention, and Fig. 2 explains the angle setting between the blood flow direction and the M raster at an arbitrary observation point on the M raster of the monitor. FIG. 3 is a diagram for explaining the operation of the embodiment.

As shown in FIG. 1, the ultrasonic diagnostic apparatus includes an ultrasonic probe 1, a transmission system 2 including a pulse generator 2A, a transmission delay circuit 2B, and a pulser 2C, and a reception system 3 including a briambe 3A and a reception delay circuit 3B. have.

The device also includes an envelope detection circuit 4A as the B-mode processing system 4, a phase detection circuit 5A as the Doppler mode processing system,
L/:/Digate circuit 5B, FFT5C, arithmetic circuit 5D
, a DSC 6A (digital scan φ converter) and a TV monitor 6B as a display system 6, and a controller 1o as a control system.

The ultrasonic probe 1 has multiple ultrasonic transducers (channels).
In order to perform the sector electronic scanning shown in Fig. 2, the excitation timing of each transducer is set in the desired direction so that the transmission direction of the ultrasonic beam sequentially changes in a fan shape for each pulse of the ultrasonic beam. We will change it accordingly.

That is, first, when the pulse generator 2A receives a clock pulse (not shown), it generates a rate pulse corresponding to the ultrasonic repetition frequency and outputs it to the transmission delay circuit 2B.

The transmission delay circuit 2B provides a predetermined delay time for each channel so that the ultrasound probe 1 transmits the ultrasound in a desired direction.

The balsa 2C generates a drive pulse from the delayed rate pulse output from the transmission delay circuit 2B, and drives each transducer of the ultrasound probe 1.

Thus, the ultrasound probe 1 generates ultrasound and transmits the ultrasound into the living body via the living body surface 5. This ultrasonic wave is partially reflected by the blood vessels in the living body and the blood flow (mainly red blood cells) in the blood vessels, and its echo No. 12 is received by the same transducer.

The preamplifier 3A amplifies the echo signal input from the ultrasound probe 1, and then outputs this echo signal to the reception delay circuit 3B.

The reception delay circuit 3B provides a delay time to restore the delay time given by the transmission delay circuit 2B, and then the signals of each channel are combined by an adder (not shown).

The combined signal is then output to an envelope detection circuit 4A and a phase detection circuit 5A.

The envelope detection circuit 4A performs envelope detection on the received signal from the reception delay circuit 3B, and outputs B-mode image data (tomographic image data) to the DSC 6A.

The phase detection circuit 5A inputs the manually input echo signal and a reference signal (not shown) from the reception delay circuit 3B, performs phase detection, and obtains phase information, that is, a Doppler shift frequency consisting of a Doppler signal and a clutter component.

This signal is converted into a digital signal by an A/D converter (not shown), and clutter components are removed by a filter (not shown) to obtain a Doppler signal.

Then, in order to extract the Doppler signal only at the depth of the blood flow in the living body, the Doppler signal is input to the range gate circuit 5B.

Here, as shown in FIG. 2, a fan-shaped tomographic image and blood flow information are displayed simultaneously on the monitor, and a raster M is set so as to intersect with the blood flow S. Further, a sample volume SV (range gate position) is set near the intersection, and a mark R is displayed so as to rotate around the center O.

This mark R is rotated by an arbitrary angle θ around the center 0 by rotating an encoder (not shown). Then, the angle θ is determined by estimating the mark R as the blood flow direction and adjusting it to this direction.

Further, when the encoder is manually rotated in an arbitrary direction, the controller 10 rotates the mark R in conjunction with this, calculates the angle θ, and outputs this angle to the arithmetic circuit 5D.

As shown in Fig. 2, the range gate circuit 5B applies a range gate to the sampling volume 3y (also referred to as range gate position) on an arbitrary rask M displayed on the TV monitor, and detects only Doppler signals within this range. Extract.

The FFT 5C, which serves as a frequency analyzer, performs frequency analysis on the Doppler signal from the range gate circuit 5B to determine temporal changes in blood flow velocity, thereby determining the maximum flow velocity V Wax.

Next, the features of this embodiment will be explained with reference to FIG. The feature of this embodiment is that, as shown in FIG. 3, by moving the ultrasound probe 1 in contact with the living body surface a1 to the living body surface a2, the angle θ1 between the blood flow direction and the ultrasound beam is , θ2 are determined by the controller 10, and based on the angles θ1, θ2 and the apparent maximum flow velocities Vmaxi, Vmax2 at these angles, the effective blood flow components are removed, that is, the true maximum flow velocity value. The point is that an arithmetic circuit 5D is provided to obtain the .

That is, first, the maximum Doppler velocity v max at the angle θ1 between the ultrasonic beam and the blood flow on the biological surface a1
i is detected by the FFT5C. Next, the ultrasound probe 1 is moved to the biological surface a2, and the maximum Doppler velocity v sax2 at the angle θ2 between the ultrasound beam and the blood flow is
Detect.

The arithmetic circuit 5D inputs the angles θ1 and θ2 from the controller 10, and calculates the maximum speed v maxi,
Input v *ax2 from FFT5C, V■az-v
Substitute each value into o+vr/cosθ. Then vsaxl=
v o +v r/c o s θ 1vl
aX2-Vo +vr/cos θ2.

Solving the above equation yields the active ingredient V. , the invalid component V ``is Vo'' (
vlaxllICOSθ1-VlaX2'eOθ2)/
(COSθ1-cosθ2) vr-eOsθl@COθ2 (v maxi −
v wax2)/(eosθ2−cos′θl).

Further, using the blood vessel diameter 2R obtained by the range gate circuit 5B, the calculation circuit 5D calculates the cross-sectional area A of the blood vessel at the observation point from A-π'2. Then, the arithmetic circuit 5D can obtain the blood flow rate QQA-VO/2.

Thus, the effective component V from the arithmetic circuit 5D. ．． Inactive component V
r, blood flow rate Q, and B-mode image data from the envelope detection circuit 4A are simultaneously displayed on the TV monitor 6B via the DSC 6A.

That is, as shown in FIG. 6, the effective component V of blood flow velocity. ，
The invalid component Vr and blood flow Q can be displayed simultaneously. In other words, 2
If we measure the maximum velocity from each angle, Vo,
Vr can be found.

This makes it possible to improve the accuracy of blood flow measurement.

Also active ingredient V. , the flow status can be displayed, such as the reactive component vr display, so the reliability of the device can be improved.

Thus, according to this example, the active ingredient V. , the invalid component V' can be separated, angle dependence is eliminated, and the true blood flow rate can be determined. Therefore, for example, in a blood vessel near the body surface (such as a carotid artery), although the ultrasonic beam angle θ is large, the true blood flow rate can be determined without increasing the flow rate measurement error.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the ultrasound probe 1 is divided into two parts, and these ultrasound probes 1a and 1b simultaneously transmit echo signals from the blood vessel in parallel in real time to the ultrasound beam and the blood flow direction. The angle α. It is designed to be received at β.

As shown in the figure, there is a wave transmitting/receiving circuit 2 on the ultrasonic probe la side.
D, FFT 5C1, and arithmetic circuit 5D1 are provided, and the DSC 6A is connected behind them. The ultrasonic probe 1b also includes a receiving circuit 3C, an FFT 5C2, and an arithmetic circuit 5.
D2 is provided, after which the DSC 6A is connected.

In the device configured in this manner, the ultrasonic beam is transmitted from the transceiver circuit 2D at an angle α with respect to the blood flow direction, and when receiving, the ultrasonic beam from the blood vessel is received by the transceiver circuit 2D at the angle α. At the same time, the receiving circuit 3C transmits the ultrasound from the blood vessel to the angle β between the ultrasound beam and the blood flow direction.
Receive at.

Furthermore, each echo signal is processed by each FFT5C
1,5C2 allows the maximum flow rate V aaxl. V aax2
seek. After that, the arithmetic circuit 5D performs the FFT 5C.
Maximum flow velocity V maxl, V sax2 from 1,5C2
Based on the angles α and β, the angle θ1−α and the angle θ2−(α+β)/2 are first determined, and the effective component V of the blood flow velocity is calculated using the formula in the first embodiment. and the inactive component V' can be determined, and furthermore, the blood flow Q can be determined. In other words, by measuring the respective maximum velocities from two angles, v0 and vr can be determined. Thereby, the accuracy of blood flow measurement can be improved. Furthermore, since the flow status can be displayed, such as by displaying the active component vO r and the inactive component vr, the reliability of the device can be improved.

Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment is a modification of the second embodiment, and includes a transmitting circuit 2E and receiving circuits 3C and 3D to receive echo signals in parallel and simultaneously in real time. The receiving circuit 3C includes FFT5C2. Arithmetic circuit 5D
is connected to the receiving circuit 3D, and an FFT 5C1 and an arithmetic circuit 5D are connected to the receiving circuit 3D.

In the device configured in this way, the transmitting circuit 2E transmits an ultrasound beam at an angle θ0 with respect to the blood flow direction, and upon reception, the receiving circuit 3D receives the ultrasound beam from the blood vessel at the angle α. , and at the same time, the receiving circuit 3C receives the ultrasonic waves from the blood vessel at the angle β between the ultrasonic beam and the blood flow direction.
Receive at.

Furthermore, each echo signal is processed by each FFT5C
Maximum flow velocity V saxl, V max2 due to 1,5C2
seek. After that, the arithmetic circuit 5D performs the FFT 5C.
Maximum flow velocity Vsaxl, Vsax2 from 1,5C2 and angle α. Based on β, first find the angle θ1-(θ0+α)/2 and the angle θ2-(θ0+β)/2, then use the formula in the first embodiment to find the effective component v0 and the invalid component Vr of the blood flow velocity, Furthermore, blood flow ffi
Q can be found. In other words, vO rvr can be determined by measuring the respective maximum velocities from two angles. Thereby, the accuracy of blood flow measurement can be improved. In addition, the reliability of the device can be improved because the flow status can be displayed, such as by displaying "active component vO + inactive component V".

In this way, according to this embodiment, two beam angles formed by different ultrasound beam directions and blood flow directions are determined, the maximum blood flow velocity for each beam angle is detected, and these beam angles and maximum blood flow Effective component of blood flow velocity from velocity. Since the inactive component and the blood flow rate are determined, for example, the blood flow is made to be in a turbulent state, and the active component (2) is determined. , a reactive component vr, the detected maximum speed vmax (after angle correction) can be expressed as v@:1x-vo+v r/co s θ. In other words, if you measure the maximum speed from two angles,
v, ), vr can be obtained. Thereby, the accuracy of blood flow measurement can be improved.

It should be noted that the present invention is not limited to the embodiments described above, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] According to the present invention, a plurality of beam angles formed by different ultrasound beam directions and blood flow directions are determined, the maximum blood flow velocity for each beam angle is detected, and these beam angles and Since the effective component, the ineffective component, and the blood flow rate of the blood flow velocity are determined from the maximum blood flow velocity, even if the beam angle becomes large, there will be no measurement error in the blood flow velocity, and the accuracy of blood flow measurement can be improved. I can do it. Furthermore, since the flow state of active ingredients, ineffective ingredients, etc. can be displayed, it is possible to provide an ultrasonic diagnostic device that can improve the reliability of the device.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of the ultrasonic diagnostic device according to the present invention, FIGS. 2 and 3 are diagrams for explaining the operation of the device shown in FIG. 1, and FIG. FIG. 5 is a schematic block diagram showing a second embodiment of the invention, FIG. 5 is a schematic block diagram showing a third embodiment of the invention, and FIG. 6 shows an active component of blood flow velocity displayed on a monitor. Diagram showing ineffective components and blood flow,
FIG. 7 to FIG. 15 are diagrams for explaining an upward change in blood flow velocity with respect to a beam angle in a conventional ultrasonic diagnostic apparatus. 1... Ultrasonic probe, 2A... Pulse generator, 2B
...Transmission delay circuit, 2C...Pulser, 2D...Transmission/reception circuit, 2E...Transmission circuit, 3A...Brieamp, 3B...Reception delay circuit, 3C, 3D...Reception circuit , 4A... Envelope detection circuit, 5A... Phase detection circuit, 5B... Range gate circuit, 5C, 5C1.5C2
...FFT, 5D... Arithmetic circuit, 6A... DSC
, 6B...TV monitor, 10...controller.

Claims (1)

[Claims] Ultrasonic diagnostic equipment transmits and receives ultrasound waves to and from a subject using an ultrasound probe, extracts a Doppler signal from the received signal, and measures blood flow based on this Doppler signal. A means for determining a plurality of beam angles formed by the sound wave beam direction and the blood flow direction, and a maximum blood flow velocity for each beam angle obtained by this means are respectively detected, and the blood flow velocity is calculated from these beam angles and maximum blood flow velocity. active ingredient,
An ultrasonic diagnostic apparatus characterized by comprising a calculating means for determining an ineffective component and the blood flow rate.