JPS61272036A - Average flow 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] [Summary] A device for measuring the average blood flow velocity using ultrasonic waves, which can modify the data input to the MFL (mean flow velocity) calculation circuit by adding means for operating the screen. In this way, it is possible to remove noise that interferes with average flow velocity calculations and to correct aliased images.

[Industrial application field]

The present invention relates to an ultrasonic diagnostic apparatus that diagnoses internal tissue by emitting ultrasonic waves into a living body and receiving the reflected waves to perform data analysis, and particularly relates to blood flow velocity measurement in cardiac diagnosis.

Among heart diagnoses, heart valves are diagnosed by measuring changes in blood flow velocity to determine valve function.

Blood flow within the heart contains complex velocity components due to the complex structure of the heart, but in order to obtain data for diagnosing the movement of heart valves, it is necessary to summarize the measured values of these velocity components. In order to capture and express the function, we calculate the average value of the values, that is, the average flow velocity.

First, the ultrasound is focused on an observation point and the reflected waves are received.
The obtained data is subjected to fast Fourier transform (hereinafter referred to as FFT transform) to obtain the power spectrum at that time.

That is, the received data is divided into frequency components, and the received strength of each frequency component is numerically expressed as a spectral quantity.

The frequency of the reflected wave is greater than the transmission frequency for blood flow approaching the ultrasonic sensor at the observation point, and becomes smaller for blood flow moving away.

Such reception frequency components and reception strengths are converted into blood flow velocity components and their component strengths.

Therefore, this power spectrum shows the distribution of flow velocity components, and although it can be displayed as an image as it is, a more universal representation can be performed using the average value image.

When calculating the MFL value, it is necessary to remove from the data factors that adversely affect the calculation results, such as electrical noise, or if the receiving frequency exceeds the expected range, aliasing (A Iias
ing) phenomenon may cause folding of the MFL curve on the screen, which is uncomfortable to observe and needs to be corrected.

Therefore, there is a need for a flow rate measuring device that eliminates such factors that are inconvenient to measurements and allows screen operations to be performed to display an accurate and easy-to-observe screen.

[Conventional technology]

FIG. 4 shows a conventional flow velocity measuring instrument, in which an ultrasonic reflection signal is input to an FFT conversion circuit, converted into a power spectrum, and output.

This power spectrum is divided, for example, into 128 flow velocity components between the maximum and minimum expected flow velocity, and is stored in a data memory as data expressed by the spectral amount of each flow velocity component.

This spectral amount is converted into luminance by the display control section and displayed as an image on the display, or the data is used to calculate MFL in the MFL calculation circuit, and the calculation result is displayed as an image on the display.

[Problem that the invention seeks to solve]

This conventional method requires a predetermined signal level for the ultrasonic sensor to receive the ultrasonic reflected wave and input it to the FFT conversion circuit.

In order to obtain this predetermined signal level, an extremely weak signal is analog amplified, but it is inevitable that noise will be mixed in at that time.

The mixed noise will be displayed as a bright spot on the screen, and will be extremely difficult to observe.

As a countermeasure to this problem, automatic gain control (AGC) is used to filter the entire signal by treating signals below a certain level as noise and removing them, or amplifying them.

For this reason, it has not been possible to remove only noise that has a strong fixed spectral component (frequency) as shown by the dotted line in FIG.

When MFL is calculated using these data, there is a drawback that the MFL curve does not take the original value due to the noise.

Similarly, when FFT conversion causes a phenomenon such as aliasing or aliasing in the power spectrum, the MFL curve no longer takes the original value.

In addition, in FIGS. 5 and 6, the horizontal (X) axis shows the passage of time, the vertical (Y) axis shows the frequency (i.e., flow velocity),
The component amount of each flow velocity is expressed by brightness.

[Means for solving problems]

FIG. 1 shows a block diagram of the principle of the average flow velocity measuring device of the present invention.

In FIG. 1, 1 is an ultrasonic sensor that receives reflected ultrasonic waves, 2 is an FFT conversion circuit that converts the received signal of the ultrasonic sensor 1 into a power spectrum, 3 is a data memory that stores the power spectrum, and 4 is data Memory 3 to MFL
an input modification circuit that modifies data input to the calculation circuit 5;
6 is a display control circuit that controls input data of the display 7;
is a screen operation section, which has a keyboard 81 for observing the screen of the display 7 and inputting operation inputs for modifying the screen.

[Effect]

The power spectrum stored in data memory 3 is
The noise is displayed on a display via a display control circuit, and the noise is displayed as a bright spot in the image displayed on the display.

The mixed noise is usually constant frequency noise and appears as a bright line perpendicular to the Y axis.

In this case, by inputting the coordinates corresponding to the bright line of the noise from the input keyboard of the screen operation section, the input modification circuit excludes the specified data from the data input to the MFL calculation circuit, and displays the data through the MFL calculation circuit. MFL
The image is the image from which noise has been removed.

In addition, as shown in Figure 6, if the image has aliasing and is a folded image, if you specify area A indicated by the double line with the input keyboard and perform screen operations, you will be able to The image of area A is separated and moved vertically to the position where the lower limit line of the area matches the upper limit line of the screen, and the display curve that was cut by the upper limit line becomes connected, and the MF
The data input to the L calculation circuit is also input as the value of the correction curve.

In this way, by inputting required data from the keyboard of the image operation section, it is possible to eliminate noise and improve the image to be easier to observe.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the input modification circuit 4 for removing noise according to the present invention, in which the noise band to be removed is specified from the keyboard 81 of the image operation section 8.

That is, the range where noise exists is determined by the Y coordinate, for example (Y +
, Yz) is input to the input modification circuit 4.

The flow velocity component Y of the power spectrum at a certain time from the data memory 3 and the spectrum measurement are read out and sent to the input modification calculation circuit 4.

The input modification arithmetic circuit 4 calculates the coordinate Y and the noise interval (y, -
The comparison circuit 41 checks Yl), and when Yl exists in the noise section, controls the multiplexer 43 so as not to take in the spectrum tDi and send it to the MFL calculation circuit 5, but to send dummy data 42.

Note that the dummy data 42 has a value that does not affect the MFL calculation.

The data from which noise has been removed will be sent to the MFL calculation circuit 5.

The MFL calculation circuit 5 calculates the MFL using the flow velocity component Y and the spectrum measurement using the following equation and outputs it.

MFL=Σ(Di·Y,)/ΣD4 In this case, i=1 to 128.

The output MFL is displayed on the display 7 via the display control unit 6.
The coordinates are displayed as a single bright spot.

Therefore, the MFL is displayed as a curve as shown in FIG. 7, which changes every moment.

Next, FIG. 53 shows an embodiment of a circuit for correcting area synchronization occurring in a power spectrum image.

If an image extending beyond the upper limit line of the screen appears on the lower limit line, area A is specified using the keyboard 81 in a trace format.

Then, in the area register 44 of the input modification circuit 4, the Y coordinate values Y, , , , Y, at each X coordinate of the address of the power spectrum stored in chronological order are added to the lower limit line B outside the specified area. The coordinate Y is stored.

The power spectrum measurement at a certain time X, is Y;(i
= 1 to 128) while increasing the reading MFL calculation circuit 5
Send the data to.

The area register 44 contains threshold values (Y, . . . ) for each Xj.

Y, ) is given, so compare this threshold Y with the read Y, and when the threshold Y is exceeded, change the Y coordinate value to (Y,
−Y, ).

This determination is made by the comparison circuit 41°, and the multiplexer 43
instruct.

Although YL is a Y coordinate value, it is also a Doppler frequency and a flow velocity component.

The subtractor 45 calculates Y and -Yi, and they are calculated as faster flow velocity components as shown in the calculation schematic diagram in Figure 8, and the calculated MFL is displayed as shown in Figure 9. Ru.

Above we have explained the method of measuring the average value of all flow velocity components, but the flow velocity approaching the observation point, that is, the toward
It goes without saying that the same method can be applied to measuring the average flow velocity for each component of the Toward flow velocity and the flow velocity moving away from the observation point, that is, the Away flow velocity.

〔Effect of the invention〕

As described above, according to the present invention, when measuring average flow velocity, noise can be removed and images with aliasing can be easily modified while observing the display screen, and an extremely useful measuring device for practical use is provided. can.

[Brief explanation of drawings]

Fig. 1 is a principle block diagram of the average flow velocity measurement according to the present invention, Fig. 2 is an embodiment of the input modification circuit, Fig. 3 is another embodiment of the input modification circuit, Fig. 4 is a conventional example, and Fig. 5 is a conventional example. The figure is a power spectrum diagram containing noise, Figure 6 is a power spectrum with aliasing and a diagram of the repair area setting, Figure 7 is an MFL diagram with noise removed, Figure 8 is a schematic diagram of MFL calculation, Figure 9 is the MFL diagram in Figure 6. In the figure, l is an ultrasonic sensor, 2 is an FFT (fast Fourier) transform circuit, 3 is a data memory, 6 is a display control unit, 7 is a display device, 8
is a screen operation unit, 41.41' is a comparison circuit, 42 is dummy data, 43 is a multiplexer, 45 is a subtracter,
81 is a keyboard. A-R Shi'1f4ff Ao-7W 1) 1 Figure 1-q Total angle λ force 4 Zuto 1 ≧ Chi 6 Go S Hanawa one - Su 5
Shazukutsu 2nd cause 0 case @ 4 Figure

Claims (3)

[Claims] (1) A data memory (3) that stores in time series the distribution of flow velocity components obtained by analyzing reflected ultrasound signals; and an MFL that calculates the average flow velocity (MFL) from the contents of the data memory (3). a calculation circuit (5), the contents of the data memory (3) and the average flow velocity (MFL);
), and a display control circuit (6) that controls input to the display (7), the screen of the display (7) is operated. Average flow velocity measurement characterized in that a screen operation section (8) and an input modification circuit (4) for modifying the input data of the MFL calculation circuit (5) by the output of the screen operation section (8) are attached. Device. (2) Y representing the specified two Y coordinate ranges on the screen of the display (7) and the flow velocity component in the data memory (3);
a comparison circuit (41) for comparing the coordinates with the comparison circuit (41);
The input modification circuit (4) includes a multiplexer (43) that selects and outputs either the spectral amount of the data in the data memory (3) or predetermined dummy data (42) according to the output of (1). An average flow velocity measuring device according to claim 1, characterized in that: (3) a comparison circuit (41') that compares the Y coordinate of a designated area boundary on the screen of the display device (7) and the Y coordinate of data in the data memory (3); ), the multiplexer (43) selectively outputs the difference between the Y coordinate of the data in the data memory (3) and the maximum Y coordinate, and the Y coordinate of the data in the data memory (3). The average flow velocity measuring device according to claim 1, characterized in that it comprises an input modification circuit (4).