JPH05111486A - Ultrasonic doppler diagnostic device - Google Patents

Abstract

PURPOSE:To display only the blood flow, etc., by eliminating the influence of wall motion. CONSTITUTION:A normalizer 8 which takes in and normalizes the output of an orthogonal detector 4 via A/D converters 7a, 7b is provided. Amplitude information is eliminated by the normalization. The lower region in the output of the normalizer 8 is attenuated by high-pass filters 6a, 6b to make the attenuation quantity and the frequency correspondent to each other. The signal of the small attenuation quantity is selected by a signal selector 10 and is subjected to computation of a velocity, such as blood flow. The influence of Doppler components by the wall motion of a powerful amplitude is eliminated and the necessary blood flow information is easily visibly displayed.

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 detecting the motion velocity of a reflector such as blood, and more particularly to an apparatus having a two-dimensional blood flow display function for displaying blood flow in two dimensions.

[0002]

2. Description of the Related Art Conventionally, ultrasonic Doppler diagnostic devices have been used in the medical field. This type of device transmits an ultrasonic wave into the living body and detects the Doppler shift of the frequency of the reflected wave. If the object reflecting the ultrasonic waves is a moving object such as blood, the Doppler shift frequency depends on the velocity of this reflector. That is, the ultrasonic Doppler diagnostic apparatus is an apparatus that obtains and displays velocity information of a moving reflector in a living body to obtain significant information for medical treatment.

The information thus obtained must be displayed so that the doctor can understand it intuitively and as easily as possible. In order to perform such a display, an image display capable of two-dimensional display is used.

FIG. 6 shows the configuration of an ultrasonic Doppler diagnostic apparatus according to a conventional example. This device has substantially the same configuration as the two-dimensional blood flow imaging device disclosed in Japanese Patent Publication No. 62-44494 of the present applicant.

This device comprises a probe 2 which comes into contact with a living body 1. The probe 2 has a predetermined number of piezoelectric vibrators and is excited by the transceiver 3. That is, according to the signal of the predetermined repetition frequency from the transceiver 3, the probe 2
Generates ultrasonic vibrations, and reflected echoes from the blood flow in the living body are captured by the transceiver 3 as electric signals.

The output of the transceiver 3 is taken into the quadrature detector 4. The quadrature detector 4 converts the reflected echo into two types of complex signals that are 90 ° out of phase with each other. For this reason,
The mixers 4a and 4b are provided for taking in the reference signals 5a and 5b, which are 90 ° out of phase with each other, from the timing signal generator 12 and mixing them with the reflected echoes. The timing signal generator 12 gives the transceiver 3 a repetition frequency as a clock.

Low-pass filters 6a and 6b are connected to the subsequent stages of the mixers 4a and 4b, respectively. Mixer 4
Since the outputs of a and 4b include the components of the sum frequency and the difference frequency of the electric signal related to the reflection echo and the reference signals 5a and 5b, in this conventional example, the low-pass filter 6 is used.
Only the difference frequency component is extracted by a and 6b.
This difference frequency component is a Doppler shift frequency component.

An A / D converter 7 is provided after the quadrature detector 4.
a and 7b are provided. This A / D converter 7a, 7
b converts the difference frequency component into a digital signal.
The high-pass filters 9a and 9b provided in the subsequent stage of the A / D converters 7a and 7b are so-called wall motion filters. Wall motion is a motion of the heart wall or the like, and in the device of this conventional example, a Doppler shift frequency of a relatively low frequency is generated. For the purpose of measuring and displaying the blood flow velocity, the Doppler shift frequency due to wall motion is unnecessary.
The lower frequency of the Doppler shift frequency is removed from the I and Q vector outputs by the / D converters 7a and 7b, respectively.

Further, in this conventional example, a speed calculator 11 is provided. Speed calculator 11, the high-pass filter 9a, 9b of the _I F, determined the motion velocity of the blood flow based on the _{Q F} vector output is supplied to the digital scan converter 14.

This motion velocity calculation is performed, for example, according to the following algorithm.

First, the speed calculator 11 calculates R and I by the following equation.

R = x1x2 + y1y2 = 4sin ² (2πfdT / 2) cos (2πfdT) I = x2y1-x1y2 = 4sin ² (2πfdT / 2) sin (2πfdT) However, the repetition period is T, the Doppler shift frequency is fd, and high. The output of the high-pass filter 9a is x1, and the high-pass filter 9 is
High-pass filter 9 in which the output of b is delayed by y1 and T
High-pass filter 9 in which the output of a is delayed by x2, T
The output of b is y2.

Next, the argument tan ^-1 (I / R) is obtained based on the argument vectors R and I (or the average value of R and I for noise removal) thus obtained. This can be performed by referring to, for example, a ROM that stores a table that associates the values of I and R with the values of the declination. The declination has a value proportional to the Doppler shift frequency fd. The Doppler shift frequency fd becomes information indicating the blood flow velocity if the influence of the wall motion is completely removed.

On the other hand, the electric signal relating to the reflected echo output from the transceiver 3 is supplied to the detector 13. The detector 13 detects the signal and outputs the signal. This signal represents a black and white tomographic image and is supplied to the digital scan converter 14 to be two-dimensionally mapped. As a result, the display on the image display 15 is performed. By using the output of the velocity calculator 11 here, the blood flow distribution can be continuously measured and displayed.
For example, the screen can be colored according to the speed information.

[0015]

However, the conventional ultrasonic Doppler diagnostic apparatus has a problem that the effect of wall motion is not completely removed.
This is because the Doppler component due to wall motion has a strong amplitude.

Therefore, in the conventional apparatus, the effect of wall motion may appear on the display image. For example,
Structures such as the heart wall sometimes appeared colored on the screen. Such a phenomenon is clinically unnecessary information for a doctor and, in extreme cases, may be more noticeable than blood flow.

The present invention has been made to solve the above problems, and an ultrasonic Doppler diagnostic apparatus capable of displaying only clinically necessary blood flow information by eliminating the influence of wall motion. The purpose is to provide.

[0018]

In order to achieve such an object, the present invention has a normalizer for normalizing the amplitude of an output signal of a quadrature detector and outputting the normalized signal. A signal selector that removes a signal with an amplitude of a predetermined value or less from the output of the high-pass filter and outputs the signal is provided after the high-pass filter. It is characterized in that information corresponding to the speed is output.

[0019]

In the present invention, the amplitude of the output signal of the quadrature detector is normalized by the normalizer. Then, the output signal of the normalizer does not include the amplitude information, and only the phase (frequency) information remains. When this is supplied to a high pass filter, low frequency components are attenuated. At this time, if the characteristics of the high-pass filter are known, the frequency can be known from the amount of attenuation. That is, the frequency is associated with the amount of attenuation. In the present invention, the output of such a high pass filter is supplied to the signal selector. The signal selector removes signals of small amplitude, resulting in the removal of low frequency components. In this way, low frequency components are removed regardless of the Doppler component amplitude. That is, the influence of wall motion is significantly eliminated.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. It should be noted that the same components as those of the conventional example shown in FIG.

FIG. 1 shows the configuration of an embodiment of the present invention. In this embodiment, a normalizer 8 is provided after the A / D converters 7a and 7b, and the I'and Q'vectors output from the normalizer 8 are supplied to a high-pass filter 9a or 9b. A feature is that a signal selector 10 is provided between the band-pass filters 9a and 9b and the speed calculator 11.

The configuration of the normalizer 8 is shown in FIG.

As shown in this figure, the normalizer 8 is
Amplitude calculator 100, normalization calculators 101a and 101b,
It is composed of a comparator 102 and switches 103a and 103b. The amplitude calculator 100 takes in the I and Q vectors output from the A / D converters 7a and 7b and calculates the amplitude (I ² + Q ² ) ^1/2 . The normalization arithmetic units 101a and 101b respectively convert I and Q into amplitudes (I ² +
Q ² ) ^Divide by ^1/2 . As a result, I and Q are normalized. The comparator 102 compares the amplitude (I ² + Q ² ) ^1/2 with the set value V _TH1, and only when the former is large, that is, only when it can be considered that the input I and Q are not noise, the normalization operator The switches 103a and 103b provided at the subsequent stages of 101a and 101b are closed.
As a result, when the amplitude (I ² + Q ² ) ^1/2 is larger than the set value V _TH1 , the normalized values I ′ and Q ′ obtained by the normalization calculators 101a and 101b are output, When the amplitude (I ² + Q ² ) ^1/2 is smaller than the set value V _TH1, 0 is output. Output I of normalizer 8
'And Q'are input to the high pass filters 9a and 9b,
Low frequencies are removed. In the case of this embodiment, the high pass filters 9a and 9b have the characteristics shown in FIG. That is, when the repetition period of the ultrasonic beam is expressed as T, the high-pass filters 9a and 9b have the attenuation amount of 0 dB at the frequency 1 / 2T and the characteristics are set to have the attenuation amount of AdB at the frequency f _TH . There is. As mentioned above, since the output of the normalizer 8 is normalized,
Depending on the output level from the high pass filters 9a and 9b, that is, the amount of attenuation in the high pass filters 9a and 9b,
High-pass filter 9a, 9b output _I F of a state that can know the frequency of the _{Q F.}

The high-pass filter 9a, 9b output _I F of,
Q _F is input to the signal selector 10. FIG. 4 shows the configuration of the signal selector 10. As shown in this figure, the signal selector 10 includes an amplitude calculator 200, a comparator 201, and switches 202a and 202b. The amplitude calculator 200 includes a high-pass filter 9
Amplitude (I _F ² + Q _F ² ) from outputs I _F and Q _{F of} a and 9 b
Calculate ^1/2 . The comparator 201 has an amplitude (I _F ²
+ Q _F ² ) ^1/2 is compared with a predetermined value V _TH2, and the switches 202a and 202b are turned on only when the former is large.
The switches 202a and 202b are each high-pass filter 9a, 9b output _I F of, _{Q F} of speed calculator 1
It is provided to open and close the output to 1. Therefore, when the switch 202a and 202b are turned on, the high-pass filter 9a, 9b output _I F of, _{Q F} is _I'F, applied to the speed calculator 11 as _Q'F. Also, the switch 20
If 2a and 202b are turned off, 0 is _I'F, applied to the speed calculator 11 as _Q'F. As shown in FIG. 5, I ′ before attenuation by the high-pass filters 9a and 9b,
Q ′ is located on the unit circle in the complex coordinate system, and I _F after attenuation,
Q _F is to be positioned inside the unit circle. This I _F ,
When the amplitude (I _F ² + Q _F ² ) ^1/2 determined by Q _F is smaller than the predetermined value V _TH2 , for example, within the shaded area in FIG. 5, 0 is input to the speed calculator 11.

As a result, the speed calculator 11 determines the amplitude (I _F
For signals for which ² + Q _F ² ) ^1/2 is smaller than the predetermined value V _TH2 , information regarding speed is not calculated and output, but only for large signals. High pass filter 9
In a and 9b, the low frequency components are largely attenuated, so that the signal processed by the speed calculator 11 is only the signal related to the relatively high frequency Doppler component among the Doppler components. As a result, the Doppler component related to the wall motion having a low frequency does not affect the speed display. Further, since the normalization is performed and the amplitude information is removed, it is not affected by the strong amplitude of the Doppler component related to the wall motion.

As described above, according to the present embodiment, only the clinically necessary blood flow information can be displayed without the influence of wall motion.

In this embodiment, the speed calculator 11 is based on the one described in Japanese Patent Publication No. 62-44494, but other devices may be used. That is, any speed display may be performed by an image based on the Doppler shift frequency. Further, the characteristics of the high-pass filters 9a and 9b may be set so as to clearly distinguish the frequency related to the wall motion from other bands.

[0028]

As described above, according to the present invention,
After normalizing the output of the quadrature detector, the low frequency range is attenuated and the velocity calculation is performed only for signals with small attenuation. Therefore, the influence of the Doppler component with a strong amplitude is eliminated to display the velocity image. You can As a result, the influence of wall motion can be eliminated, and only clinically necessary blood flow information can be displayed.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a normalizer in this embodiment.

FIG. 3 is a diagram showing characteristics of a high-pass filter in this embodiment.

FIG. 4 is a block diagram showing a configuration of a signal selector in this embodiment.

FIG. 5 is a complex plan view showing the input / output relationship of the high pass filter in this embodiment.

FIG. 6 is a block diagram showing a configuration of an ultrasonic Doppler diagnostic apparatus according to a conventional example.

[Explanation of symbols]

 2 probe 3 transceiver 4 quadrature detector 8 normalizer 9a, 9b high-pass filter 10 signal selector 11 speed calculator 12 timing signal generator 13 detector 14 digital scan converter 100, 200 amplitude calculator 101a, 101b Normalization arithmetic unit 102,201 Comparator 103a, 103b, 202a, 202b Switch

Claims (1)

[Claims] 1. An ultrasonic beam is transmitted to a motion reflector such as a bloodstream existing in a living body while scanning along a predetermined direction, and a reflection echo from the motion reflector is received and output as an electric signal. Transmitting and receiving means, a detector that detects the electrical signal related to the reflection echo and outputs a signal representing a black and white tomographic image, and an electric signal related to the reflection echo into two types of signals that are orthogonal to each other and have Doppler shift frequency A quadrature detector that converts and outputs, a normalizer that normalizes and outputs the output signal amplitude of the quadrature detector, and a high-pass filter that removes the frequency component below a predetermined value from the output of the normalizer and outputs it. A filter, a signal selector that removes signals with amplitudes below a predetermined value from the output of the high-pass filter, and outputs the Doppler shift frequency based on the output of the signal selector to correspond to the velocity of the motion reflector. Information output speed Based on the calculator, the output signal of the detector and the output information of the speed calculator,
An ultrasonic Doppler diagnostic apparatus comprising: a display unit for displaying a black-and-white tomographic image with coloring according to the speed of a motion reflector.