JPH0947456A - Ultrasonic doppler diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve real-time performance when a B mode image and a Doppler mode image are observed in a switching system by reducing a level of a transitional response generated in output of a high-pass filter in the initial stage of transferring a Doppler mode. SOLUTION: After output signals of interval integrating circuits 12a and 12b are converted into digital signals by ADCs 14a and 14b in a Doppler mode image detecting display system, they are sent to a filter processing part 16. A delay register setting value operation means 17 approximately calculates a setting value of a delay register in a secondary filter section as the inside constitution of wall filters 13a' and 13b' on the basis of signal series inputted to the filter processing part 16 in the initial stage of a Doppler time phase, and its result is preset in the delay register. Therefore, since the wall filters 13a' and 13b' are put in an already set condition to an initial input signal row of a Doppler mode time phase, ringing is removed as a response to a clutter signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic Doppler diagnostic apparatus for measuring blood flow velocity by the Doppler method while transmitting and receiving ultrasonic waves in a subject and observing a real-time B-mode image of a diagnostic region. The present invention relates to an ultrasonic Doppler diagnostic apparatus capable of improving real-time property when switching between a B-mode image and a Doppler mode image for observation.

[0002]

2. Description of the Related Art A conventional ultrasonic Doppler diagnostic apparatus of this kind transmits a ultrasonic wave into a subject and receives a reflection echo from the inside thereof to collect and display a B mode image. The system and the ultrasonic wave of a pulse or a continuous wave is transmitted to the inside of the subject and the reflection echo from the inside is received, and the component of the frequency signal that is Doppler-shifted of the moving body is extracted from this reflection echo, and the blood flow. A Doppler mode image detection and display system that displays a signal as an image or outputs acoustically as an audio signal, and an ultrasonic wave transmission and reception operation in the B mode image detection and display system and an ultrasonic wave transmission and reception in the Doppler mode image detection and display system. The operation and the time division are performed to display ultrasonic images of both systems.

That is, as shown in FIG. 12, the electric pulse generated by the pulser 3 in the ultrasonic wave transmitter / receiver 2 is transmitted to the probe 1
And ultrasonic pulses are transmitted from the probe 1 into the subject (not shown). The echo signal reflected from the diagnostic region inside the subject is received by the probe 1 and converted into an electric signal again. This received signal is amplified by the preamplifier 4 in the ultrasonic wave transmitter / receiver 2 and sent to the detector 6 in the B-mode image detection / display system. The detector 6 performs envelope detection to obtain a luminance signal. This brightness signal is AD
The signal is converted into a digital signal in C7, image-processed in a DSC (digital scan converter) 8, sent to a monitor 9, and displayed as a B-mode image on the screen of the monitor 9.

On the other hand, in the Doppler mode image detection display system, the reception signal amplified by the preamplifier 4 in the ultrasonic wave transmitting / receiving section 2 is multiplied by the reference wave in the mixers 10a and 10b,
It is converted into a complex baseband signal through the low-pass filters 11a and 11b. This complex baseband signal is input to the interval integration circuits 12a and 12b, and the interval integration circuit 12
Reference numerals a and 12b integrate and hold the complex signal in the section corresponding to the sample volume. The interval integration circuit 12
The signals output from a and 12b pass through wall filters 13a and 13b, which are high-pass filters for removing clutter components from fixed tissues in the subject, and are frequency signals subjected to Doppler shift from blood flow or the like. Only (blood flow signal) is taken out. This extracted blood flow signal is AD
It is converted to a digital signal by C14a and 14b, and F
Frequency analysis circuit 1 composed of FT (Fast Fourier Transform)
Sent to 5. Then, frequency analysis is performed by the frequency analysis circuit 15, image processing is performed by the DSC 8 and the image is sent to the monitor 9, and a Doppler spectrum (Doppler mode image) of the blood flow is displayed on the screen of the monitor 9.

Here, since the directions of the ultrasonic transmission / reception beam for displaying the B-mode image and the directions of the ultrasonic transmission / reception beam for performing the Doppler mode image are different in most cases, the B-mode The ultrasonic wave transmitting / receiving operation for obtaining an image and the ultrasonic wave transmitting / receiving operation for obtaining a Doppler mode image are performed in a time division manner. Therefore, the display operation of the Doppler mode image is stopped when the B-mode image is displayed in real time, and the B-mode image is frozen when the Doppler mode image is displayed in other time phases in real time. It In this case, in the Doppler mode image, since it is necessary to set the position of the sample volume using the real-time B-mode image as a guide, the real-time property of the B-mode image is important even in the Doppler mode.
For this reason, in the conventional apparatus, as shown in FIG. 13, the B-mode time phase and the Doppler mode time phase are alternately switched to prevent the real-time property from being impaired as much as possible.

[0006]

However, in such a conventional ultrasonic Doppler diagnostic apparatus, the complex baseband signals output from the low pass filters 11a and 11b shown in FIG. 12 are passed through the interval integrating circuits 12a and 12b. Wall filters 13a and 13b for removing the clutter component from the fixed tissue in the subject from this signal.
It had the lowest cut-off frequency among the components of the entire device, from about 50 Hz to about 1 KHz, and required steep characteristics. This means that the wall filter 13
Comparing the transient response when a signal is input to a and 13b with other filters in the entire device, the wall filters 13a,
This means that 13b causes the longest ringing (oscillation of the signal until it stabilizes). As a result, as shown in FIG. 13, when switching from the B-mode time phase to the Doppler mode time phase, at the beginning of the Doppler mode time phase, the clutter signal S ₁ input to the wall filters 13a and 13b is applied to the wall. Filters 13a and 13b
A strong ringing S ₂ is always generated in the output signal of the. Therefore, it was necessary to wait a sufficient time until the ringing S ₂ converged and the filter output was stabilized. Therefore, the B mode time phase and the Doppler mode time phase cannot be frequently switched, and the real-time property of the image is low.

Therefore, the present invention provides an ultrasonic Doppler diagnostic apparatus which can cope with such a problem and improve the real-time property when observing by switching the B-mode image and the Doppler mode image. With the goal.

[0008]

In order to achieve the above object, an ultrasonic Doppler diagnostic apparatus according to the present invention transmits an ultrasonic wave into a subject and receives a reflection echo from the inside thereof to obtain a B mode image. And a B-mode image detection and display system for collecting and displaying, and transmitting a pulse or continuous wave ultrasonic wave into the subject and receiving a reflection echo from the inside thereof, and Doppler shift of the moving body from the reflection echo. It has a Doppler mode image detection display system that extracts a frequency signal component, displays a blood flow signal as an image, or outputs acoustically as an audio signal,
An ultrasonic Doppler diagnostic apparatus for displaying ultrasonic images of both systems by time-divisionally performing the ultrasonic wave transmission / reception operation in the B-mode image detection display system and the ultrasonic wave transmission / reception operation in the Doppler mode image detection display system. A high-pass filter constituted by a digital filter as a means for extracting the Doppler shift frequency signal, and the delay register of the high-pass filter at the time of switching from the B-mode image receiving operation to the Doppler mode image receiving operation. Is provided with a filter processing unit having means for initializing the above value to a predetermined value according to the received signal so as to reduce the level of the transient response occurring in the output of the high pass filter at the initial stage of the Doppler mode transition.

Further, the means for initializing the value of the delay register of the high-pass filter to a predetermined value according to the received signal changes the initialized value from the receiving operation of the B mode image to the receiving operation of the Doppler mode image. It is supposed to be calculated by linear combination from one or more values of the initial received signal sequence at the time of switching.

Alternatively, the means for initializing the value of the delay register of the high-pass filter to a predetermined value according to the received signal changes the initialized value from the B-mode image receiving operation to the Doppler mode image receiving operation. An estimated signal corresponding to the start of the Doppler mode time phase estimated using the angular frequency of the input signal detected before the time of switching and the initial received signal sequence at the time of switching to the receiving operation of the Doppler mode image It may be calculated by linear combination of sequences.

Further, the high pass filter may be a recursive filter.

The ultrasonic Doppler diagnostic apparatus according to the second aspect of the present invention transmits the ultrasonic waves into the subject and receives the reflected echoes from the inside thereof to collect and display the B mode image. The system and the ultrasonic wave of a pulse or a continuous wave is transmitted to the inside of the subject and the reflection echo from the inside is received, and the component of the frequency signal that is Doppler-shifted of the moving body is extracted from this reflection echo, and the blood flow. A Doppler mode image detection and display system that displays a signal as an image or outputs acoustically as an audio signal, and an ultrasonic wave transmission and reception operation in the B mode image detection and display system and an ultrasonic wave transmission and reception in the Doppler mode image detection and display system. In an ultrasonic Doppler diagnostic apparatus that displays the ultrasonic images of both systems by performing time-division of the motion and With a high-pass filter to, after the means for frequency analysis the blood flow signal after extracting the Doppler-shifted frequency signal component with this high-pass filter, the DC component of the spectrum in the frequency domain after the frequency analysis. The window processing means for removing or reducing the low frequency components including is provided.

Then, the high-pass filter has a DC component of the spectrum in the frequency domain after frequency analysis by the frequency analysis means as a cut-off frequency for removing the clutter component from the fixed tissue in the subject from the received signal in the time domain. It is set to be lower than the cutoff frequency for reducing the window function for removing or reducing low frequency components including.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an ultrasonic Doppler diagnostic apparatus according to the first invention. This ultrasonic Doppler diagnostic apparatus measures the blood flow velocity by the Doppler method while transmitting and receiving ultrasonic waves in the subject and observing a real-time B-mode image of the diagnostic region. As shown in FIG. The tentacle 1 and the ultrasonic transmitter / receiver 2
, Oscillator 5, detector 6, ADC 7, DSC 8
, Monitor 9, mixers 10a and 10b, low-pass filters 11a and 11b, and interval integration circuits 12a and 12b.
And ADCs 14a and 14b and a frequency analysis circuit 15, and a filter processing section 16 is further provided.

The probe 1 transmits / receives ultrasonic waves to / from a diagnosis site in a subject, and inside the probe 1, it converts an electric signal into an ultrasonic wave and an ultrasonic wave into which the received ultrasonic wave is converted into an electric signal. Built-in sound wave oscillator. Ultrasonic transceiver 2
Is a device for driving the probe 1 to transmit and receive ultrasonic waves. The pulsar 3 for inputting the frequency from the oscillator 5 to generate an electric pulse and the probe 1 receive the ultrasonic wave. And a preamplifier 4 for amplifying the received signal converted into an electric signal.

The detector 6 inputs the received signal output from the preamplifier 4 in the ultrasonic wave transmitting / receiving section 2 and performs envelope detection to obtain a luminance signal. The ADC 7 inputs the luminance signal output from the detector 6 and converts it into a digital signal. In addition, DSC8 is the above A
The digital image data output from the DC 7 is input and required image processing is performed for displaying on the monitor 9. Further, the monitor 9 receives the image data output from the DSC 8, converts it into an analog video signal and displays it as a B-mode image, and is composed of, for example, a television monitor. Then, the detector 6, the ADC 7, and the DS
The C8 and the monitor 9 constitute a B-mode image detection display system.

On the other hand, the mixers 10a and 10b are for receiving the reception signal output from the preamplifier 4 in the ultrasonic wave transmitting / receiving section 2 and multiplying it by the frequency of the reference wave output from the oscillator 5. Low-pass filter 11a, 1
1b is for inputting the received signal multiplied by the frequency of the reference wave in the mixers 10a, 10b and converting it to a complex baseband signal. The interval integration circuits 12a and 12b are
The complex baseband signals output from the low-pass filters 11a and 11b are input, and the complex baseband signals in the section corresponding to the sample volume are integrated and held. The ADCs 14a and 14b convert the signals output from the interval integration circuits 12a and 12b into digital signals.

In the present invention, the above ADCs 14a, 1
The filter processing unit 16 is provided in the subsequent stage of 4b.
The filter processing unit 16 is a wall filter 13a ', 1 which is a high-pass filter composed of a digital filter as a means for extracting the Doppler shift frequency signal.
3b 'and the wall filter 13 at the time of switching from the B-mode image receiving operation to the Doppler mode image receiving operation.
The delay register settling value calculating means 17 is means for initializing the values of the delay registers a ', 13b' to a predetermined value according to the received signal. The wall filter 13
As shown in FIG. 2, the internal structure of a ', 13b' is a recursive filter (referred to as an IIR filter) having a sharp cutoff characteristic by connecting a plurality of secondary filter sections 18 ₁ to 18 k in series. ) Is configured. Further, the individual second-order filter sections 18 ₁ ~18k,
As shown in FIG. 3, the adders 19a and 19b and the multiplier a
₁₁ , a ₁₂ , b ₁₀ , b ₁₁ , b ₁₂ and the delay register (T) 2
0a and 20b. Then, by the operation of the filter processing unit 16 having such a configuration, the level of the transient response generated in the outputs of the wall filters 13a 'and 13b' is reduced at the initial stage of the transition from the B mode image to the detection of the Doppler mode image. Has become.

The frequency analysis circuit 15 inputs the signal processed by the filter processing section 16 and analyzes the frequency, and is composed of, for example, an FFT. The mixers 10a and 10b and the low-pass filters 11a and 11b as described above.
And the interval integration circuits 12a and 12b and the ADCs 14a and 1
4b, the filter processing unit 16, and the frequency analysis circuit 15
The DSC 8 and the monitor 9 constitute a Doppler mode image detection display system.

Next, the operation of the ultrasonic Doppler diagnostic apparatus thus constructed will be described. Here, the operation in the B-mode image detection display system and the operation up to the interval integration circuits 12a and 12b in the Doppler mode image detection display system are
Since it is similar to the conventional example shown in FIG. 12, the description thereof is omitted. In the Doppler mode image detection display system, the signals output from the interval integration circuits 12a and 12b are ADC1
After being converted into a digital signal by 4a and 14b, it is sent to the filter processing section 16. The delay register settling value calculation means 17 in the filter processing unit 16 has an internal configuration of the wall filters 13a 'and 13b' based on the signal series input to the filter processing unit 16 at the initial stage of the Doppler mode time phase. Of the second-order filter sections 18 _{1 to} 18 k (see FIG. 2) of the delay registers 20 a and 20 b (see FIG. 3)
Approximately calculates the settling value of, and the calculation result is preset in the delay registers 20a and 20b. As a result, the wall filters 13a ′, 13 in the filter processing unit 16 are
b ', since the state already settled to the initial input signal sequence of the Doppler mode phase, so that the ringing S ₂ as a response to the clutter signals S ₁ shown in FIG. 13 is removed.

The operation of removing the ringing S ₂ will be described below. First, the wall filter 13 shown in FIG.
a ', 13b' in the interior construction of the individual second-order filter sections 18 ₁ ~18k, and those using common filter operation as shown in FIG. Then, the difference equation regarding the values of the delay registers 20a and 20b for the first second-order filter section 18 ₁ can be calculated from FIG. Given in. Here, assuming that the input signal sequence x ₁ n can be represented by a linear function, the settling value of the delay register 20a for this input signal sequence can also be represented by a linear function due to the linearity of the equation. this, It expresses. Note that Δx and Δu are the amount of change (constant) in the value of the input variable and the delay register 20a, respectively.

From the above equations (1) and (3), the value preset in the delay register 20a is It is represented by Further, when the difference of the difference equation (1) is obtained and the difference of the input signal and the difference of the delay register 20a are arranged using Δx and Δu defined by the equations (2) and (3), respectively, Therefore, if this Δx is expressed by the difference of the input signal series, Becomes Substituting this equation (6) into the above equation (4) and rearranging, However, Becomes The above equation (7) means that when the input signal sequence is approximated by a linear function, the settling value of the delay register 20a can be calculated by linear combination of the input signals at two points. The coefficient of the linear combination also becomes a known parameter according to the equations (8) and (9), and may be held as a table on the memory.

A block diagram of such an operation is as follows:
It becomes like FIG. FIG. 4 is a detailed view of the inside of the filter processing unit 16 shown in FIG.
Shows a connection state of the next filter section 18 ₁ ~18k. Here, the delay register settling value calculation means 1
Reference numeral 7 includes delay registers (T) 21a and 21b, four multipliers having predetermined coefficients, and adders 22a and 22b. The output signals from the adders 22a and 22b are respectively the second-order filter section 1 described above.
8 _{1 to} 18 k, and via the changeover switches 23 a and 23 b provided therein, the first delay register 2
0a or the second delay register 20b.

In the structure shown in the block diagram, the operation timing in the initial stage of the Doppler mode time phase is shown in FIG. In FIG. 5, assuming that the number of input signals is n and the time point at which the first definite data is received after the transition to the Doppler mode time phase is n = 0, n
The period <3 is the preset period of the settling value, and the delay register settling value calculating means 17 shown in FIG.
(8), the approximation calculated preset value according to (9) wall filter 13a ', 13b' delay register 20a of the second-order filter sections 18 ₁ ~18k in, 20
preset to b. At this time, in FIG. 4, the second-order filter sections 18 ₁ changeover switch 23a in ～18K, 23b are connected to each indicated by a solid line.

After that, the period of n ≧ 3 becomes the period of normal filter operation, and in FIG. 4, the changeover switches 23a and 23b in the secondary filter sections 18 _{1 to} 18k are shown.
Are connected as shown by broken lines and perform normal filter operation. This operation can be realized by hardware composed of, for example, a multiplier, a register, and a multiplexer, or a general-purpose DSP.
It can also be realized by using (digital signal processor). In particular, when a DSP is used, no special hardware is required as the delay register settling value calculation means 17 shown in FIG. 4, and the required calculation coefficient value is stored in advance in the ROM (read-only memory) and the Doppler It suffices to execute the preset routine that should be performed by the delay register settling value calculation means 17 at the start of the mode time phase. in this case,
The operation uses linear combination, that is, the product-sum operation, which is the most basic function of the DSP, and thus can be easily realized.

As described above, the delay registers 20a and 20b (see FIG. 4) of the second-order filter sections 18 _{1 to} 18k in the wall filters 13a 'and 13b' are set at the start of the Doppler mode time phase shown in FIG. Since the preset value is set to the set value, the ringing S ₂ as the response of the clutter signal S ₁ in the input signal as shown in FIG. 13 is suppressed as the output signal of the wall filters 13a 'and 13b'. Therefore, the B mode time phase and the Doppler mode time phase can be frequently switched, and the real-time property of the image can be improved. In the above description, although the calculation formula is derived by approximating the input variable to the linear function in the formulas (1) to (7), even if the order of the input variable is approximated to the 0th order (constant value). Alternatively, the similar operation can be realized by approximating a higher-order function form of quadratic or higher. For example, when the input variable is approximated by an m-order function, the delay registers 20a, 20
The settling value of b can be calculated by linear combination of input variables at (m + 1) points. Among these, the simplest construction method is a method of performing 0th-order approximation. In this case, the set values of the delay registers 20a and 20b are calculated from one point of the input variable.

Delay register set value calculating means 1 shown in FIG.
As another operation example of 7, If "0" is set to, the operation will be performed using the 0th-order approximation. In this case, the error from the settling becomes large due to the rough approximation, but in the configuration of the delay register settling value calculation means 17, the number of multipliers and the number of adders can each be reduced by 2 and the noise level of the input signal. Is relatively high,
Since there is no differential operation, there is an advantage that it is less susceptible to the noise. This operation example is suitable when the level of the clutter signal S ₁ in the input signal of the wall filter shown in FIG. 13 is relatively high and the frequency is low enough to be regarded as direct current.

FIG. 6 is a block diagram of an essential part showing a second embodiment of the present invention. In this embodiment, as the delay register settling value calculating means 17 shown in FIG. 1, settling values for presetting the delay register T of the secondary filter sections 18 _{1 to} 18 k in the wall filters 13 a ′ and 13 b ′ are set to the B mode. Estimated using the angular frequency of the input signal detected before the time point when the image receiving operation is switched to the Doppler mode image receiving operation, and the initial received signal train at the time point when the Doppler mode image receiving operation is switched. The calculation is performed by linear combination of estimated signal sequences corresponding to the start of the Doppler mode time phase. 6 is an internal detailed diagram of the filter processing unit 16 in this embodiment, in which the delay register settling value calculation means 17 and the secondary filter section 1 in the wall filters 13a 'and 13b' are provided.
Shows a connection state between 8 ₁ ~18k.

The operation of the embodiment shown in FIG. 6 will be described below. In FIG. 6, the input signal series x ₁ n and the output signal series y ₁ n are complex numbers. In the delay register settling value calculation means 17, an angle obtained from the difference in phase angle between two time points with M sample intervals in the received complex signal sequence in the past Doppler mode time phase during the B mode time phase period Tb. With the frequency as the estimated angular frequency, the above-mentioned estimated angle is added to the initial representative complex number obtained by linear combination from the numerical values of one or more points of the initial complex received signal sequence when switching to the Doppler mode time phase (n = 0). For example, four points (A to D) of initial estimated complex time series data that are sequentially generated by repeatedly multiplying a rotor having a frequency are obtained, and for each element of the time series data A to D, linear values of one or more points are obtained. The coupling is adopted as a value for initializing the delay register T of the secondary filter sections 18 _{1 to} 18 k in the wall filters 13 a ′ and 13 b ′. In this embodiment, the input variable is approximated to a cubic function, but the DSP used as the delay register settling value calculation means 17 has a calculation capability, and when precise settling is required, it is relatively The error from the settling value can be further reduced by using an approximation with a high order and observing the frequency of the clutter signal S ₁ (see FIG. 13) more accurately.

In the above embodiment, the linear combination of the estimated complex time series data generated by multiplying the rotator is used instead of the linear combination of the actual data, because the high frequency component included in the input signal is removed. By doing so, the settling effect is improved by the relatively low-order approximation of the cubic function. In general, input variables have complicated waveforms, so if you try to perform precise settling, an approximation with a very high order will be required, and the scale of calculation will become enormous. Using the linear combination of the estimated complex time series data generated by the above is effective in reducing the calculation amount.

FIG. 7 is a block diagram showing an embodiment of an ultrasonic Doppler diagnostic apparatus according to the second invention. This ultrasonic Doppler diagnostic apparatus has wall filters 13a and 13b as high-pass filters that remove clutter components from fixed tissues in the subject from the received signal in the time domain, and the Doppler polarized waves are filtered by the wall filters 13a and 13b. A window process for removing or reducing low-frequency components including a direct-current component of the spectrum in the frequency region after the frequency analysis is performed after the frequency analysis circuit 15 that performs frequency analysis on the blood flow signal after extracting the components of the transferred frequency signal. The part 24 is provided. That is, in the conventional apparatus shown in FIG. 12, the window processing section 24 is provided between the frequency analysis circuit 15 and the DSC 8 so that the same effect as that of the first invention shown in FIG. 1 is exerted.

Then, the wall filters 13a, 1
3b is a cutoff frequency for removing the clutter component from the fixed tissue in the subject from the received signal in the time domain, and the low frequency component including the direct current component of the spectrum in the frequency domain after frequency analysis by the frequency analysis circuit 15. It is set to be lower than the low-frequency cutoff frequency of the window function to be removed or reduced.

Next, the operation of the ultrasonic Doppler diagnostic apparatus according to the second aspect of the invention configured as described above will be described. First, in FIG. 7, the Doppler signal converted into a digital signal by the ADCs 14a and 14b is input to the frequency analysis circuit 15, where the frequency analysis is performed and the power spectrum is calculated. At this time, the frequency analysis score is, for example, 12
About 8 points. Now, when the number of analysis points is n,
Data of the result of analysis performed by the window processing unit 24 composed of n multipliers as shown in FIG. Is calculated by each multiplier Are sent to the next DSC 8, the required image processing is performed, and the frequency spectrum is displayed on the monitor 9. As shown in FIG. 9, the window function in the window processing unit 24 has a shape shown by a solid curve on the frequency axis, and removes or reduces low-frequency components including direct current. .

Here, from the level of the pass band, for example, 3 dB
The attenuating frequency is the cutoff frequency of the window function, and the cutoff frequency is Fc ₂ in FIG.
When the cutoff frequency of the wall filters 13a and 13b is Fc ₁ , this cutoff frequency Fc
₁ is set low with respect to the cutoff frequency Fc ₂ of the window function. In such a state, in the conventional device shown in FIG. 12, as shown in FIG. 10, the wall filter 13a on the time axis of the cutoff frequency Fc,
With only 13b, when the B-mode time phase shown in FIG. 13 is switched to the Doppler mode time phase, the frequency spectrum thereof causes ringing having a peak in the vicinity of the cutoff frequency Fc.

On the other hand, in the second invention shown in FIG. 7, as shown in FIG. 11, the cutoff frequency Fc ₁ of the wall filters 13a and 13b on the time axis is set to be smaller than the cutoff frequency Fc of the conventional example. By setting it low,
The ringing frequency generated when the B-mode time phase is switched to the Doppler mode time phase can be suppressed to a low value. At this time, the conventional cutoff frequency F is added to the window function after frequency analysis by the frequency analysis circuit 15 shown in FIG.
By setting the cutoff frequency Fc ₂ equal to c, Fc ₂ > Fc ₁ , so that the frequency component of the ringing generated in the wall filters 13a and 13b on the time axis can be reduced or removed. Therefore, also in the second invention, the B-mode time phase and the Doppler mode time phase can be frequently switched, and the real-time property of the image can be improved.

[0036]

Since the present invention is constructed as described above,
When the B-mode time phase is switched to the Doppler mode time phase, at the beginning of the Doppler mode time phase, strong ringing occurs in the output signal of the high-pass filter with respect to the clutter signal from the fixed tissue input to the high-pass filter. Can be suppressed. Therefore, it is possible to frequently switch between the B mode time phase and the Doppler mode time phase without waiting for a sufficient time until the ringing converges and the filter output stabilizes as in the conventional case, and the real-time property of the image is improved. can do. From this, it is possible to improve the real-time property when switching between the B-mode image and the Doppler mode image for observation, and to perform good blood flow measurement.

Also in the second invention, similarly to the above, the B mode time phase and the Doppler mode time phase can be frequently switched, and the real-time property of the image can be improved. Therefore, it is possible to improve the real-time property when observing by switching the B-mode image and the Doppler mode image, and it is possible to perform good blood flow measurement.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an ultrasonic Doppler diagnostic apparatus according to the first invention.

FIG. 2 is a block diagram showing an internal configuration of a wall filter.

FIG. 3 is a block diagram showing an internal configuration of a secondary filter section in the wall filter.

FIG. 4 is a block diagram showing a connection state and calculation between a delay register settling value calculation means in the filter processing section and a secondary filter section in the wall filter.

5 is an explanatory diagram showing a calculation timing in an initial stage of a Doppler mode time phase in the configuration shown in FIG. 4;

FIG. 6 is a block diagram of an essential part showing a second embodiment of the first invention.

FIG. 7 is a block diagram showing an embodiment of an ultrasonic Doppler diagnostic apparatus according to the second invention.

FIG. 8 is a block diagram showing an internal configuration of a window processing unit.

FIG. 9 is a graph showing a window function in the window processing unit.

10 is an explanatory diagram showing that ringing occurs when the B-mode time phase is switched to the Doppler mode time phase in the conventional apparatus shown in FIG.

FIG. 11 shows the device B according to the second invention shown in FIG.
It is explanatory drawing which shows suppressing the frequency of the ringing which occurs when switching from a mode time phase to a Doppler mode time phase.

FIG. 12 is a block diagram showing a conventional ultrasonic Doppler diagnostic apparatus.

FIG. 13 is a timing diagram for explaining a problem of the conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Probe 2 ... Ultrasonic wave transmission / reception part 5 ... Oscillator 6 ... Detector 7, 14a, 14b ... ADC 8 ... DSC 9 ... Monitor 10a, 10b ... Mixer 11a, 11b ... Low pass filter 12a, 12b ... Section integration circuit 13a. , 13b, 13a ', 13b' ... wall filter 15 ... frequency analyzing circuit 16 ... filtering unit 17 ... delay register set value calculator 24 ... window processing unit S ₁ ... clutter signal S ₂ ... ringing

Claims (6)

[Claims] 1. A B-mode image detection display system for transmitting an ultrasonic wave into a subject and receiving a reflection echo from the inside to collect and display a B-mode image, and a pulse or a continuous wave in the subject. The ultrasonic wave is transmitted and the reflection echo from the inside is received, and the component of the frequency signal that is Doppler-shifted of the moving body is extracted from this reflection echo, and the blood flow signal is displayed as an image or is acoustically output as an audio signal. A Doppler mode image detection / display system, and ultrasonic transmission / reception operation in the B mode image detection / display system and ultrasonic wave transmission / reception operation in the Doppler mode image detection / display system are performed in a time division manner. An ultrasonic Doppler diagnostic apparatus for displaying a sound wave image, having a high-pass filter constituted by a digital filter as a means for extracting the Doppler shift frequency signal, and The Doppler mode is provided with a filter processing unit having means for initializing the value of the delay register of the high-pass filter to a predetermined value at the time of switching from the reception operation of the B-mode image to the reception operation of the Doppler mode image. An ultrasonic Doppler diagnostic apparatus characterized in that the level of transient response occurring in the output of the high-pass filter is reduced at the initial stage of transition. 2. The means for initializing the value of the delay register of the high-pass filter to a predetermined value according to the received signal changes the value to be initialized from the B-mode image receiving operation to the Doppler mode image receiving operation. The ultrasonic Doppler diagnostic apparatus according to claim 1, wherein the ultrasonic Doppler diagnostic apparatus is calculated by linear combination from one or more values of an initial received signal sequence at the time of switching. 3. The means for initializing the value of the delay register of the high-pass filter to a predetermined value according to the received signal changes the value to be initialized from the B-mode image receiving operation to the Doppler mode image receiving operation. An estimated signal corresponding to the start of the Doppler mode time phase estimated using the angular frequency of the input signal detected before the time of switching and the initial received signal sequence at the time of switching to the receiving operation of the Doppler mode image The ultrasonic Doppler diagnostic apparatus according to claim 1, which is calculated by linear combination of sequences. 4. The ultrasonic Doppler diagnostic apparatus according to claim 1, wherein the high-pass filter is a recursive filter. 5. A B-mode image detection display system for transmitting an ultrasonic wave into a subject and receiving a reflection echo from the inside to collect and display a B-mode image, and a pulse or a continuous wave in the subject. The ultrasonic wave is transmitted and the reflection echo from the inside is received, and the component of the frequency signal that is Doppler-shifted of the moving body is extracted from this reflection echo, and the blood flow signal is displayed as an image or is acoustically output as an audio signal. A Doppler mode image detection / display system, and ultrasonic transmission / reception operation in the B mode image detection / display system and ultrasonic wave transmission / reception operation in the Doppler mode image detection / display system are performed in a time division manner. An ultrasonic Doppler diagnostic apparatus for displaying a sound wave image has a high-pass filter for removing clutter components from fixed tissues in the subject in the time domain, and After extracting the Doppler-shifted frequency signal component with a pass filter, the low-frequency component including the DC component of the spectrum is removed or reduced after the means for frequency-analyzing the blood flow signal. An ultrasonic Doppler diagnostic apparatus, which is provided with window processing means for performing the operation. 6. The high-pass filter is a direct-current component of a spectrum in a frequency domain after frequency analysis by a frequency analysis means as a cutoff frequency for removing a clutter component from a fixed tissue in a subject from a received signal in a time domain. 6. The ultrasonic Doppler diagnostic apparatus according to claim 5, wherein the cutoff frequency is set to be lower than a cutoff frequency for reducing a window function for removing or reducing low frequency components including.