JPH0523334A - Ultrasonic Doppler imaging device - Google Patents

Abstract

(57) [Abstract] [Purpose] A high-precision speed calculation can be performed without increasing the signal processing scale, and a good Doppler color image can be obtained. [Structure] The received signals of reflected ultrasonic waves obtained from the ultrasonic probe 1 are subjected to quadrature phase detection by mixers 4 and 5. From the obtained I and Q signal intensities, the high-pass filter 1 is controlled by the control signal A, which is evaluated by the amplitude evaluator 14 as having many clutter components.
The cutoff frequencies of 5 and 16 are increased to remove the low frequency clutter component. The outputs from the high-pass filters 15 and 16 are converted into speed information by the speed calculator 17, written in the scan converter 20, and displayed on the display 21 as a Doppler color image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic Doppler imaging apparatus used for medical ultrasonic diagnosis and for measuring blood flow velocity in a living body in real time.

[0002]

2. Description of the Related Art Recently, ultrasonic pulse Doppler measurement and pulse reflection method are used together to obtain blood flow information and tomographic image (B-mode image) information of a living body with one ultrasonic probe, and to obtain this tomographic image. There is known an ultrasonic Doppler imaging apparatus for medical use that displays blood flow information in real time in color. Such an ultrasonic Doppler image device is disclosed in Japanese Patent Laid-Open No. 63-599.
The ultrasonic diagnostic apparatus disclosed in Japanese Patent No. 38 can be mentioned.

A conventional ultrasonic Doppler imaging apparatus will be described below. FIG. 5 shows the configuration of a conventional ultrasonic Doppler imaging apparatus. In FIG. 5, the ultrasonic waves reflected from the subject are received by the ultrasonic probe 71 and amplified by the receiving circuit 72. The received signal includes the reflected wave from the fixed object and the reflected wave from the moving object in the subject, and the output signal of the receiving circuit 72 is supplied in parallel to the first and second signal processing systems.

In the first signal processing system, the output signal is amplified and detected by the detection circuit 73 to become a B-mode signal, and the DSC
At 74, it is converted into a digital signal and stored in the image memory 74a. A determination level is set in advance in the clutter map 75, and the address of the signal exceeding the determination level is recorded in comparison with the signal stored in the image memory 74a to create a map of the position where the clutter exists.

In the second signal processing system, the output signal is input to two MTI (Moving Target Indicator) circuit processes. On the other hand, the low-speed MTI processing circuit 77 outputs the reflected wave from the slow moving body without erasing it. Therefore, when clutter exists, clutter cannot be erased and is output.

On the other hand, in the high-speed MTI processing circuit 78, the reflected wave from the moving object whose position changes little is eliminated, and the clutter is also eliminated completely. Therefore, the reflected wave from the slow object is erased in the absence of clutter. The switching of these MTI processing circuits is performed by the switch 79 controlled by the switch control circuit 76. Normally, it is processed by the low-speed MTI processing circuit 77 to display a color image of a moving object. However, when a sound ray enters the position where clutter exists, that is, the signal at the address of the clutter map 75 and the B mode. Signal DSC74
When the signal of the address of the image memory 74a of
The output from the clutter map 75 activates the switch control circuit 76 to switch the changeover switch 79, and the received signal is processed by the high-speed MTI processing circuit 78 to be processed by the DSC.
The MTI output signal is sent to 80.

In this way, the clutter presence position is recorded in the clutter map 75, the switch 79 is switched according to the clutter presence, and the clutter map 75 is successively stored in the image memory 80a. The color image is output, combined with the color image, and displayed on the display unit 82.

[0008]

However, in the above-mentioned conventional ultrasonic Doppler imaging apparatus, the low speed MTI processing circuit 7 is used.
7. Two MTI processing circuits, that is, the high-speed MTI processing circuit 78 are required, and in this case, there is a drawback that the signal processing scale increases.

The present invention solves the above problems and provides an ultrasonic Doppler imaging apparatus capable of performing highly accurate speed calculation without increasing the signal processing scale and obtaining excellent Doppler color images. The purpose is to

[0010]

In order to achieve the above object, in the ultrasonic Doppler imaging apparatus of the invention of claim 1, an ultrasonic pulse is transmitted to the inside of the object and a scatterer inside the object is used. Ultrasonic pulse transmitting / receiving means for outputting the received signal that has received the reflected ultrasonic wave, storage means for storing the received signal, a high-pass filter to which the received signal from this storage means is supplied, and the storage means for subject Amplitude evaluation means for reading out received signals of the same depth in the inside and amplitude evaluation means, and when this amplitude evaluation means evaluates that there are many clutter components, the cutoff frequency of the high-pass filter is increased to reduce the low frequency clutter components. It is provided with a control means for performing the removal control and a speed calculation means for performing a calculation for obtaining the moving speed of the scatterer in the subject from the output signal from the high pass filter.

In the ultrasonic Doppler imaging apparatus of the second aspect of the invention, the amplitude evaluation means is provided with low frequency component removing means for removing extremely low frequency clutter components.

In the ultrasonic Doppler imaging apparatus according to the invention of claim 3, the high-pass filter has a constant delay time, and
When the clutter strength is small, the passing signal is provided so that the received signal does not pass through the high-pass filter and the speed is directly calculated by the speed calculating means.

[0013]

Therefore, in the ultrasonic Doppler imaging apparatus according to the first aspect of the present invention, the cutoff frequency of the high-pass filter is increased when the clutter component is large by transmitting the ultrasonic wave into the subject and evaluating the amplitude of the received signal. Since the low frequency clutter component is efficiently removed, high-accuracy speed calculation can be performed without increasing the MTI processing scale.
A good Doppler color image can be obtained.

Further, in the ultrasonic Doppler imaging apparatus according to the second aspect of the present invention, since the clutter component of extremely low frequency is efficiently removed when the amplitude is evaluated, the MTI processing scale does not increase. , High precision speed calculation is possible,
A good Doppler color image can be obtained.

Further, in the ultrasonic Doppler imaging apparatus according to the invention of claim 3, the delay time of the high-pass filter is made constant, and a passing function is provided so that when the clutter strength is small, the high-pass filter is not passed and the received signal is not passed. Since the speed is directly obtained, the timing design of the signal processing circuit can be facilitated, the sensitivity at low speed can be increased, and the MTI processing scale does not increase, and highly accurate speed calculation can be performed. Doppler color images can be obtained.

[0016]

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

FIG. 1 shows the configuration of the embodiment. In FIG. 1, 1 is an ultrasonic probe, 2 is a pulse generator, 3 is a receiving circuit, 4 and 5 are mixers, 6 is an oscillator, 7 is a shifter,
Reference numerals 8 and 9 are low-pass filters, 10 and 11 are A / D converters, 12 and 13 are memories, 14 is an amplitude evaluation section, 15 and 1
6 is a high-pass filter, 17 is a speed calculation unit, 18 is a detector, 19 is a frame memory, 20 is a scan converter, and 21 is a display unit.

Amplitude evaluation section 14, high-pass filter 15,
16 and the speed calculator 17 perform MTI processing, which will be described in detail below.

Next, the operation of the above configuration will be described.
In FIG. 1, an ultrasonic probe 1 is driven by a pulse generator 2 and sequentially emits ultrasonic pulses in the directions a, b, c, ... The emitted ultrasonic pulse is first emitted N times in the direction a, for example, about 8 times. In the first transmission / reception in the direction a, a signal reflected by the blood flow in the subject and Doppler-shifted is received by the ultrasonic probe 1, converted into an electric signal, and sent to the receiving circuit 3. One of the received signals from the receiving circuit 3 is sent to the frame memory 19 through the detector 18, and the other is quadrature-phase detected.

In the quadrature detection, the output signal of the oscillator 6 synchronized with the pulse generator 2 is phase-shifted by 90 degrees by the mixer 4 and the shifter 7, and then input to the mixer 5. The outputs of the mixers 4 and 5 are passed through the low-pass filters 8 and 9 so that I and Q
Become a signal.

The I and Q signals are converted into digital data by the A / D converters 10 and 11 and then stored in the memories 12 and 13. In the memories 12 and 13, reception data obtained by transmitting and receiving N times of the emitted ultrasonic pulse in the direction a is recorded.

Next, the data stored in the memories 12 and 13 are read out with the same depth in the subject as a group. In this case, the amplitudes of the memory outputs of the N pieces of I and Q signal data are evaluated by the amplitude evaluation section 14, and the control signal A is obtained. On the other hand, the high-pass filters 15 and 16 remove low-frequency clutter components from the I and Q signals that have passed through the amplitude evaluator 14 as they are. At this time, when the amplitudes of the I and Q signals are large, the cutoff frequencies of the high-pass filters 15 and 16 are increased because the clutter component is large.
The I and Q signal data from which the clutter components have been removed by the high-pass filters 15 and 16 are converted into speed information by the speed calculator 17. This speed information color image is written in the scan converter 20 together with the B-mode amplitude information from the frame memory 19.

The above velocity calculation is sequentially performed for each depth in the direction a. After the velocity calculation in the direction a is completed, velocity calculation is sequentially performed in the directions b, c, ... N to form a Doppler image, which is displayed on the display unit 21 as a Doppler color image.

In this way, the frequency characteristics of the high pass filters 15 and 16 can be changed when the clutter component in the received signal is large, and accurate speed calculation can be performed,
A good quality Doppler color image can be obtained.

FIG. 2 shows the detailed construction of the amplitude evaluation section 14. In the figure, 31 and 32 are delay circuits, 33 is an absolute value circuit, and 34 is a cumulative adder. In the absolute value circuit 33,
The root mean square of the I and Q signal data is obtained. In addition, the cumulative adder 34 obtains N sums of the root mean squares obtained by the absolute value circuit 33, and the high-pass filter 1 is used as the control signal A.
It is used to control the characteristics of 5 and 16. Delay circuits 31, 32
Is a data delay, and the control signal A from the accumulator 34 is time-axis aligned with the high-pass filter 15,
It is for transmitting I and Q signal data to 16.

As described above, the amplitude evaluation section 14 can obtain the control signal A for controlling the characteristics of the high-pass filters 15 and 16 according to the strength of the received signal.

FIG. 3 is a detailed block diagram of the high pass filters 15 and 16. In the figure, 40 is a coefficient generator, 41,
42, 43 and 44 are multipliers, 45, 47 and 49 are latch circuits, and 46, 48 and 50 are adders.

The coefficient generator 30 generates coefficients W ₀ , W ₁ , W ₂ , W ₃
And the values of the respective coefficients W ₀ , W ₁ , W ₂ and W ₃ are the control signal A
It depends on the value of. For example, when the strength of the received signal is high, the control signal A controls the coefficient generator 40 to increase the cutoff frequency of the high pass filters 15 and 16.
As specific examples of the coefficients, W ₀ = 1, W ₁ = −3, W ₂ = 3,
When W ₃ = -1, it becomes a third-order FIR filter. When W ₀ = 1, W ₁ = -1, and W ₂ = W ₃ = 0, the FIR filter is a first-order FIR filter. Also, W ₀ = 1 and W ₁ = W ₂ = W ₃
When = 0, the data only passes. When the data passes through the high-pass filters 15 and 16, the coefficient is selected so that the data always passes through the latch circuits 45, 47 and 49 (W ₃ = 0) so that the latency (delay time) is constant. is there.

In this way, the high pass filter 15,
In the case of 16, by setting the latency constant, the timing design of the signal processing becomes easy. Further, by providing the high-pass filters 15 and 16 with a passing function, when the clutter strength is small, I, without passing through the high-pass filter,
The velocity can be obtained from the Q signal data, and the sensitivity to low-speed blood flow can be increased.

FIG. 4 shows the configuration of the low frequency component removing section 67 provided in parallel with the amplitude evaluating section 14. 6 in the figure
1, 62 are delay circuits, 63 and 64 are average value circuits, 65,
66 is a subtractor. The average value circuit 63 calculates the average value of each of the N pieces of I signal data. After the average value is obtained by the average value circuit 63, this average value is subtracted from the I signal data that has passed through the delay circuit 61.

By performing the above calculation, the average value, that is, the DC component or the extremely low frequency signal component can be removed from the I signal data. Similarly, it is possible to remove extremely low frequency signal components from the Q signal data.

As described above, the clutter component of extremely low frequency can be removed from the I and Q signal data. Output of the amplitude evaluation unit 14 or low frequency component removal unit 6
One of the outputs of 7 is high-pass filter 15, 16
Sent to. When the output of the low frequency component removing unit 67 is sent to the high pass filters 15 and 16, the high pass filters 15 and 16 may be forced to pass.

As described above, the low-frequency component removing unit 67 provided in parallel with the amplitude evaluating unit 14 can remove only the extremely low-frequency clutter component and enhance the sensitivity to low-speed blood flow.

[0034]

As is apparent from the above description, in the ultrasonic Doppler imaging apparatus according to the first aspect of the invention, when the ultrasonic wave is transmitted into the subject and the amplitude of the received signal is evaluated, the clutter component is large. Since the cutoff frequency of the high-pass filter is increased to efficiently remove the low-frequency clutter component, the MTI processing scale does not increase,
This has the effect that a highly accurate speed calculation can be performed and a good Doppler color image can be obtained.

Further, in the ultrasonic Doppler imaging apparatus of the second aspect of the present invention, the clutter component of extremely low frequency is efficiently removed when performing the amplitude evaluation, so that the processing scale of MTI does not increase. , High precision speed calculation is possible,
It has an effect that a good Doppler color image can be obtained.

Further, in the ultrasonic Doppler imaging apparatus according to the invention of claim 3, the latency of the high-pass filter is made constant, and a pass-through function is provided so that when the clutter strength is small, the high-pass filter does not pass through the high-pass filter and the signal is directly received. Since the speed is determined, the timing design of the signal processing circuit can be facilitated, the sensitivity at low speed can be increased, the MTI processing scale does not increase, and highly accurate speed calculation can be performed, which is favorable. This has the effect of obtaining a Doppler color image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an ultrasonic Doppler imaging apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of an amplitude evaluation unit in the present embodiment.

FIG. 3 is a block diagram showing a detailed configuration of a high pass filter according to the present embodiment.

FIG. 4 is a block diagram showing a detailed configuration of a low frequency component removing unit in the present embodiment.

FIG. 5 is a block diagram showing a configuration of a conventional ultrasonic Doppler imaging device.

[Explanation of symbols]

1 Ultrasonic probe 3 Receiver circuit 4,5 mixer 12, 13 memory 14 Amplitude evaluation section 15, 16 High pass filter

Claims (3)

[Claims] 1. An ultrasonic pulse transmission / reception means for transmitting an ultrasonic pulse into a subject and outputting a reception signal obtained by receiving a reflected ultrasound at a scatterer in the subject, and storing the reception signal. Storage means for this, a high-pass filter to which the received signal from this storage means is supplied, an amplitude evaluation means for performing amplitude evaluation by reading the received signal of the same depth in the subject from the storage means, and this amplitude When the evaluation means evaluates that there are many clutter components, the control means for increasing the cutoff frequency of the high-pass filter to remove the low-frequency clutter component, and the output signal from the high-pass filter inside the subject Ultrasonic Doppler imaging apparatus comprising: speed calculation means for calculating the moving speed of the scatterer. 2. The ultrasonic Doppler imaging apparatus according to claim 1, wherein the amplitude evaluating means is provided with low frequency component removing means for removing extremely low frequency clutter components. 3. The high-pass filter is provided with a passage means for directly obtaining the speed by the speed calculation means without passing the received signal through the high-pass filter when the delay time is constant and the clutter strength is small. The ultrasonic Doppler imaging device according to claim 1 or 2.