JPS62253039A - Ultrasonic blood speed measuring apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] Ultrasonic blood flow velocity [ft] Measurement of transverse flow velocity using the Doppler effect is widely used for diagnosis of the cardiac region. The present invention makes it possible to measure the direction and the plane distribution of the absolute value of the flow velocity on a two-dimensional plane of blood flow velocity.

[Conventional technology]

The conventional measurement of flow velocity distribution is "Measurement of intracardiac blood flow and flow velocity distribution by M-sequence Doppler method" (Motonao Tanaka et al. Ultrasonic Medicine 3
Vol. 2, No. 2, 1976), this method attempts to obtain the flow velocity distribution only in the ultrasonic beam direction, and the flow velocity distribution cannot be obtained for the component perpendicular to the beam direction.

It is also known that the true direction and velocity of blood flow can be determined by measuring the flow velocity in each beam direction using the Doppler method using three ultrasound beams that make a certain angle to the same point ( Calculation of three-dimensional velocity vector by Motonao Tanaka et al. ultrasound Doppler method.

Nichicho Medical (32nd) Proceedings, 1977, -November).

If this method is combined with the above method, it is possible to create a flow velocity distribution that takes into account the direction of blood flow velocity.

In a clinical setting, acoustic windows through which ultrasound waves can easily pass are set on the same heart from three directions at the same time.Of course, the windows must be located between the ribs, and three windows placed in each window are used. The relative position and angle of the probe must be set accurately, and it is actually impossible to measure blood flow over one entire cross-section of the heart using this method, and to date, this method has not been possible. However, it has not been put into practical use.

[Problem that the invention seeks to solve]

As described above, in the prior art, the flow velocity in the direction perpendicular to the ultrasonic beam was not measured, and only the distribution in the beam direction was determined.

The object of the present invention is not only the ultrasound beam direction.

The velocity distribution in the direction perpendicular to this may also be determined simply and with good operability.

[Means for solving problems]

In an incompressible fluid, the rectangular coordinates of Fig. 2 and 3
In a three-dimensional (X-Y-Z') space like the cylindrical coordinates in the figure,
From the continuity equation (mass conservation equation), the following equation holds between each component of the fluid velocity vector U.

If the tomographic plane is set to include the axis of symmetry of the heart, there is no large error even if it is assumed that there is virtually no flow velocity in the direction perpendicular to the tomographic plane, so the equation for the direction perpendicular to the tomographic plane is therefore Ux or U, If the distribution of is known.

Uy or U is determined by the following formula.

Here, C and C' are determined if the boundary conditions are known.

By using Equation (5) or Equation (6), the velocity distribution of the orthogonal direction component can be easily obtained by obtaining the plane distribution of the unidirectional velocity and the boundary value.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Figure #c4 shows a drawing of the heart wall for explaining the present invention.

Boundary input terminal 1, orthogonal speed calculation circuit 2, data processing circuit 3, digital scan converter (1), S,
C3) 4 and the circuits other than the display (CRT3) 5 are well-known circuits.

That is, in FIG. 1, the beam steering circuit 6 controls the wave transmitting circuit 7 and the wave receiving circuit 8. The wave transmitting circuit 7 transmits an ultrasonic signal to the probe 9, and the ultrasonic beam 1
Generates 0. The wave receiving circuit 8 receives the echo signal of the ultrasonic beam, focuses it with the focusing circuit 11, and then sends it to the video circuit 12 and the Doppler circuit 13. The output of the video circuit 12 is a digital scan converter (DS).
CI) 14 and the information is displayed on the display (CR, TI) as a B-mode tomographic image, while the output of the Doppler detection circuit 13 passes through (DSC2) le and is transmitted to the two-dimensional Doppler IW' (unidirectional velocity component only ) as (CR,'
I'2) 17.

FIGS. 1 and 4 show a typical boundary value input method.

In the embodiment shown in FIG. 1, after freezing the two-dimensional Doppler image (only one direction velocity component), C1tT1 (or C
RT 2 > While looking at the image above, as shown in Figure 3,
The heart wall is traced by moving the trackball or joystick attached to the boundary input terminal. In the case of the sector image shown in FIG. 1, calculations can be simplified by using cylindrical coordinates as the coordinate system. The beam direction is r, the direction perpendicular to the beam is θ, and calculation is performed using equation (6). The boundary value only needs to be known at one point for each r over the entire range of r in the region to be determined. If the image is unclear and there is a point within the entire range of r that cannot be plotted, interpolation is performed using the boundary values of nearby points. After tracing the heart wall, the boundary values are found with the following assumptions. That is, the fifth
In fig.

In the vicinity of the wall, it is assumed that the blood flow velocity in the direction perpendicular to the wall is approximately zero, so that no problem occurs in actual problems. (however.

Exclude walls that move at high speed, such as valves. ) Therefore the fourth
The boundary value U can be obtained by calculation as shown in the figure. Calculate equation (7) by plotting the wall using a boundary input terminal.

Frozen speed U, t - read out simultaneously K.

The angle α between the plotted wall profile and the beam is calculated and the boundary value is automatically calculated using formula (7).
A. The boundary value thus obtained and the flow velocity value of the frozen unidirectional velocity component are manually input to the orthogonal direction velocity calculation circuit to calculate the orthogonal direction flow velocity value. The aforementioned black <
If the boundary values are discrete, interpolation and supplementation are performed in one calculation circuit to calculate the flow velocity value.

The calculated value is the CR after performing some data processing such as filtering and smoothing, and red and white S and C3.
Display on T3.

Although the above has shown a method in which the operator plots and traces the entire heart wall, it is also possible to automatically recognize the heart wall by measuring the intensity level of the B image. That is, as a method for automatically recognizing the heart wall, it is possible to detect the point at which the B-mode echo level exceeds a specific threshold value. In addition to the threshold value.

A condition may be added in which a change in echo level exceeds a specific threshold value for recognition. Items that move at high speed, such as valves, must be excluded because the assumption that the blood flow velocity is sufficiently low in their vicinity does not hold.One way to do this is to use a frequency shift (velocity) that is greater than or equal to the frequency shift (velocity) specified by the Doppler signal. , and when the reflection intensity exceeds a specified level, it can be determined that it is a valve, etc., and excluded. If a circuit is installed that automatically recognizes the heart wall, it has the advantage of being able to obtain velocity vector images in real time.

Another method for determining the boundary value is to determine the boundary value using a reference beam that intersects the main beam at an angle. FIG. 6 shows an embodiment using the sector scan method.

R is the a source of the reference beam, and the velocity U in the direction perpendicular to the sector beam at point P is determined by the following equation (8).

Here, U2 is the velocity in the sector beam direction, UR is the velocity in the reference beam direction, and β is the angle at which the sector beam and the reference beam intersect at point P. In FIG. 6, U indicates the AD speed.

Note that β=α10, and Um=f FT "e"-.

Using equation (8), a boundary value can be set for the range of r in the range where the sector beam and the reference beam intersect.

As explained in FIG. 6, it can be set in the range r > r 1. The range of r(rl becomes a blind spot, but the blind spot can be reduced by swinging the reference beam and increasing the angle α.

Still another method for determining the boundary value is to simultaneously receive a plurality of adjacent beams, determine the temporal correlation of these reflected signals, determine the flow velocity in the direction perpendicular to the beam, and use this as the boundary value. The method of receiving multiple beams and determining the flow velocity in the orthogonal direction from the temporal correlation has already been described.

For the purpose of simplifying the setting of the boundary values or shortening the time for setting the boundary values for real-time display, the boundary values can be set discretely, and the boundary values between them can be determined by interpolation means.

When using a four-chamber technique in which the heart is viewed from the apex of the heart, it is necessary to set boundary values for each chamber and atrium, so setting boundary values by interpolation means can be used as an effective means of saving labor.

The absolute value of the flow velocity is determined by the following equations (9) and (101).

UA=fVJT Dingku...(9) (Right angle coordinate) uA=
V1T711-7-...<101 (cylindrical coordinates)゛! The direction of the flow velocity can be found using equation (11).

Display of velocity distribution [In this case, distribution of beam direction component,
In addition to the distribution of the orthogonal direction component, the equation (9) can be subtracted from the equation (10) to display the distribution of the velocity absolute direct. In the embodiment shown in FIG. 1, the data processing circuit is equipped with an absolute value calculation circuit. This calculation can also be done by software. The data processing circuit is equipped with a streamline calculation circuit of formula (11).

The direction of flow velocity can be determined.

The velocity or velocity absolute value distribution calculated above is displayed in color on a color display by adding color differences depending on the velocity. Color CRT is a color display device.

LCD color display etc. can be used. Also.

A color speed distribution map may be created on a color film, color printer, etc.

The flow rate can also be displayed numerically on the display. In this case, it is easier to see the display points if they are displayed at regular intervals on the top, bottom, left and right. This method is effective when displaying by copying.

The direction of flow velocity can be shown on the display as streamlines. The direction can be more clearly read by placing a → mark on the streamline to indicate the direction. The streamlines can be displayed superimposed on a velocity distribution image, a B-mode image, etc.

When displaying the velocity distribution in color, the streamlines are displayed as velocity display (I
C You can use colors that are not in use.

By changing the spacing between adjacent streamlines.

It can also be used as a speed display. An example of this is shown in FIG.

The Doppler production circuit in Figure 7 is an FFT circuit.

Multi-channel FFT circuits, MTI circuits, etc. can be used. F
When using an FT circuit (or a multi-channel FFT circuit), the flow velocity is often obtained as a dispersion rather than a single spectrum. The magnitude of the variance has diagnostic value, especially when there is a constricted portion within the heart chamber.

Even in color display of absolute value distribution, it is a useful means to modulate the color tone depending on the magnitude of the dispersion. As the dispersion value used in this case, the dispersion value of the average velocity of the two orthogonal directions may be used, or the average value of the dispersion of the two orthogonal directions may be used.

The dispersion value may be set as a function value of the dispersion values in the two orthogonal directions, taking into account the average velocity, maximum velocity, etc. in each of the two orthogonal directions.

Dispersion = f (dispersion in r direction, same average velocity, same maximum velocity, same maximum intensity velocity..., dispersion in θ direction, same average velocity.

Same strict dog speed, same maximum strength speed,...) ...(1
2) FIG. 8 is an example in which the color is changed depending on the direction of the flow velocity. Objects approaching in the front direction are red.

In this example, things moving away are blue, things flowing to the right are purple, and things flowing to the left are yellow. In the case of an intermediate direction, the color is intermediate between the two. What is the magnitude of the flow velocity?

In this case, it is displayed by the brightness of the color.

Of course, it is possible to further add dispersion to the above method and modulate the color by making it milky white or the like.

〔Effect of the invention〕

The blood velocity distribution in the direction perpendicular to the beam is determined.

Therefore, the true direction of blood flow and the absolute value of flow velocity can be easily determined and displayed as a visible image, and dynamic observation in real time is also possible.

More accurate diagnosis of heart disease becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
8 through 8 are diagrams for explaining the present invention in detail. DESCRIPTION OF SYMBOLS 1... Boundary input terminal, 2... Orthogonal direction speed calculation circuit, 3... Data processing circuit, 4... Digital scan converter, 5... Display.

Claims (1)

[Claims] 1. An apparatus for measuring ultrasonic blood flow velocity, which calculates the blood velocity plane distribution of the ultrasonic traveling direction component and inserts a boundary condition into the continuity equation to obtain the above-mentioned An ultrasonic blood flow velocity measuring device characterized by determining a flow velocity in a direction orthogonal to a directional component and measuring a planar distribution of a flow velocity vector. 2. As a means of introducing boundary conditions, extract the heart wall of the cardiac tomogram, set the blood velocity perpendicular to the wall surface on this line to zero, and calculate the planar distribution of the flow velocity in the direction perpendicular to the direction of ultrasound propagation. The device according to claim 1, characterized in that it measures. 3. A planar distribution of flow velocity in a direction orthogonal to the measurement direction of a unidirectional blood velocity planar distribution is measured using a blood velocity measurement value on a measurement direction line that forms a certain angle as a boundary condition, Claim 1 Apparatus described in section. 4. The apparatus according to claim 1, wherein the flow velocity in the direction perpendicular to the beam is determined from the temporal correlation of reflection intensities between adjacent beams, and the planar distribution of the flow velocity in the orthogonal direction is measured using this as a boundary condition. 5. The apparatus according to claim 2, characterized in that the heart wall is automatically recognized from an ultrasound B-mode image instead of being drawn by an operator.