JPH0563169B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an intracorporeal blood flow velocity meter. More specifically, the present invention relates to a current meter using the ultrasonic pulsed Doppler method.

(b) Prior Art Figure 3 shows a block diagram of a conventional example. The ultrasonic probe 1 and the ultrasonic transmitting/receiving device 2 transmit ultrasonic waves to the subject at predetermined intervals and receive the echo signals. The oscillator 3 outputs reference signals of sinω and cosω, and the detection circuit 4 performs quadrature detection on the received signal, and sends the real part data to the fast Fourier transform circuit 5.
Output as imaginary part data. Average flow velocity calculator 6
sequentially outputs the average flow velocity from the results of the Fourier transform, and the display device 7 displays this. The average flow velocity is calculated by =ΣPiωi/ΣPi (1). Here, P is the power of each spectral line, and ω is a spectral number indicating the magnitude of the frequency of each spectral line. As shown in Figure 4, when performing a 128-point fast Fourier transform (FFT), when the spectrum numbers are arranged from the left end to the right as 0, 1, 2, 3, ...127, the positive direction is The flow is in the range of spectrum numbers 0 to 63, and the higher the number, the faster the flow velocity is.The flow in the negative direction is in the range of spectrum numbers 64 to 127, and the smaller the number, the faster the flow velocity.

In such a conventional example, when a speed is detected where the Doppler shift frequency exceeds 1/2 of the repetition frequency of ultrasound pulse transmission, for example, when the repetition frequency is 5kHz, the Doppler shift frequency becomes 2.5kHz or more. When this occurs, aliasing occurs and the spectrum suddenly transitions from, for example, a positive high speed to a negative high speed. The diagram in the upper half of Figure 4 illustrates this aliasing. Even though the average flow velocity of the previous time _-2 and the previous average flow velocity _{of -1} are increasing in the positive direction,
The latest average flow velocity of ₀ has jumped to a large negative value. In such cases, conventionally, humans determined that aliasing had occurred and took steps such as not using the data or modifying it, but this process requires skill. This method has the disadvantage that it requires a lot of time and effort when the amount of data increases. In addition, automatic data processing by a computer has the disadvantage that if aliasing exists, data processing may be incorrect.

(c) Object of the invention An object of the invention is to provide a blood flow velocity meter that discriminates aliasing.

(d) Configuration of the Invention The blood flow velocity meter of the present invention includes a memory for storing flow velocity data, a means for comparing previously inputted flow velocity data and later inputted flow velocity data to determine an increase or decrease in the data; means for determining a reversal of flow direction;
It is characterized by having means for outputting an aliasing detection signal when the flow direction is reversed and the flow velocity data has tended to increase in the past.

(E) Embodiment Figure 1 shows the overall block diagram. Ultrasonic probe 1, ultrasonic receiver 2, reference signal oscillator 3,
The quadrature detection circuit, fast Fourier transform circuit 5, average flow velocity calculator 6, and display device 7 are the same as the conventional ultrasonic Doppler current meter. A feature of the invention is that an aliasing detection and flow direction correction circuit 8 is provided.

FIG. 2 specifically shows an embodiment of the aliasing detection and flow direction correction circuit 8 using a 128-point FFT as an example.

The average flow velocity value ₀ is inputted every 25.6 mS, for example. Register 11 stores the previous average flow velocity value _-1 , register 12 stores the previous average flow velocity value _-2 , and input signal ₀ is sequentially shifted to registers 11 and 12 by the clock signal of control circuit 13.
_-1 , _-2 . The subtractor 14 is for determining the tendency of increase/decrease in flow velocity between the past two times ( _-1
ω _-2 ) is executed. The comparator 15 is for determining whether the current average flow velocity value ₀ is in the positive flow region or the negative flow region, and compares the numerical value 64 with the input value ₀ . The flip-flop 16 holds the previous determination result. AND gates 17 and 18 are for determining and storing whether there has been a change in the region in the flow direction.
The AND gate 17 outputs "1" when changing from positive to negative, and the AND gate 18 outputs "1" when changing from negative to positive. Flip-flop 19 is a flip-flop for flag indicating occurrence of aliasing. AND gate 20 is
The subtracter 14 is a circuit that determines that aliasing has occurred when the flow in the positive direction increases and enters a negative region, and aliasing is not currently occurring.
The output of the aliasing flag flip-flop 19, and the output of the AND gate 17 are input. The AND gate 21 is a circuit that determines that aliasing has occurred when the flow in the negative direction increases and enters the positive region from the negative, and aliasing is not currently occurring. , the output of the aliasing flag flip-flop 19, and the output of the AND gate 18 are input. These aliasing determination signals are taken out to the outside through the OR gate 22, and the flip-flop 19 is set to store them.

The AND gate 23 is a circuit that, when the flow area changes from positive to negative or from negative to positive during aliasing, determines that the aliasing has returned to its original normal state and resets the flip-flop 19. The output of the OR gate 24 and the Q output of the flip-flop 19 are used as inputs.

AND gates 25 and 26 indicate the true flow direction; AND gate 25 passes the output of comparator 15 as is when aliasing is not detected, and AND gate 26 indicates the true flow direction when aliasing is detected. time comparator 1
5 is inverted by an inverter 27 and passed through. The OR gate 28 outputs these two outputs to the outside as a true flow direction signal, and also controls the switching of the multiplexer 29. Subtractor 3
0 is when the average flow velocity value ₀ is a flow in the negative direction,
The larger the number (closer to 127), the lower the flow velocity,
( _128-0 ) is calculated by a circuit that performs a correction calculation to make the numerical value of equation (1), in which the smaller the numerical value (closer to 64) is, the greater the flow velocity is expressed, proportional to the actual flow velocity value. The multiplexer 29 is a switching circuit that selectively outputs either the average flow velocity value ₀ or the corrected calculated value ( _128-0 ) as flow velocity data, and outputs the former when the flow direction is positive, and the latter when it is negative. .

Next, the overall operation will be explained. The subtractor 14 outputs a Hi signal when the flow velocity is increasing, and a Lo signal when it is decreasing, and the AND gate 17 outputs a Hi signal when the flow direction changes from positive to negative.
8 outputs Hi when it changes from negative to positive, so
AND gate 20 detects that aliasing has not occurred, the flow direction has reversed from positive to negative, and the past average flow velocity has been increasing,
The AND gate 21 detects that aliasing has not occurred, the flow direction has reversed from negative to positive, and the past average flow velocity is on the decline.
Detection of these two cases passes through the OR gate 22 and is determined to be the occurrence of aliasing. When aliasing occurs, the flip-flop 19 memorizes it, and the AND gate 26 and inverter 27
When aliasing occurs, the flow direction is reversed and corrected, and the true flow direction signal is output to the outside. Also,
When the true flow direction is negative, calculate the complement of the number 128,
Flow velocity data is output after correction so that the numerical values 1 to 64 correspond to low to high average flow velocities.

In another embodiment of the present invention, the decelerator 14 calculates the difference ( _-1 - _-2 instead of calculating | ₀ - _-
1 | is calculated, and the AND gate 17 or 18 changes in the positive direction or negative direction region, and
If the value is 64 or less, it is determined that aliasing has occurred, and if it is larger than 64, it is determined that the flow velocity value has simply changed from positive to negative or from negative to positive. In other words, The presence or absence of aliasing can also be determined from the amount of change in the average flow velocity ω ₀ .

(f) Effects According to the present invention, since the occurrence of aliasing is automatically detected and the flow direction is corrected, there is no need for the user to judge whether or not the flow velocity data is abnormal while referring to images, etc. It has also become possible to directly input flow velocity data and flow direction data into a computer for data processing. Also, when performing correction in the direction of flow velocity and complement processing of flow velocity data in connection with detection of occurrence of aliasing, the display range of flow velocity data is 0 in both the positive and negative directions.
~127, which is twice as large as before.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention, and FIG. 2 is a circuit diagram showing the main part of the embodiment. FIG. 3 is a block diagram showing a conventional example, and FIG. 4 is an explanatory diagram of the operation of the conventional example. 6... Average flow velocity calculator, 8... Aliasing detection and flow direction correction circuit, 11, 12... Register, 14... Subtractor, 15... Comparator,
16...Flip-flop, 19...Flip-flop, 17, 18, 20, 21, 23, 25,
26...AND gate, 22, 28...OR gate, 29...multiplexer, 30...subtractor.

Claims (1)

[Scope of Claims] 1. A memory for storing flow velocity data, means for comparing earlier input flow velocity data and later input flow velocity data to determine an increase or decrease in data, and means for determining reversal of flow direction. and a blood flow velocity meter having means for outputting an aliasing detection signal when the flow direction is reversed and the flow velocity data has tended to increase in the past. 2. The blood according to claim 1, comprising means for determining the flow direction from a code of input flow velocity data, and means for inverting the output of the flow direction determination means when an aliasing detection signal is output. Velocity meter. 3. The blood flow velocity meter according to claim 1, further comprising means for correcting the numerical value of the input flow velocity data to the complement of a predetermined numerical value and outputting the result when the flow direction output indicates a negative direction.