JP2002034985A - Ultrasonograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve image quality especially at a deep part in an organism while restricting generation of higher harmonies in an ultrasonograph. SOLUTION: A specified code sequence is represented by plural frequency numbers to an array vibrator, and coding transmission signals in which waveforms are connected to each other between codes are supplied. To received signals from a transceiver, cross correlation operation is performed using reference signals for representing waveforms of the coding transmission signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ultrasonic diagnostic apparatus, and more particularly, to a pulse compression technique.

[0002]

2. Description of the Related Art In ultrasonic diagnosis, an ultrasonic pulse is transmitted into a living body and an echo from the living body is received. An ultrasonic image such as an ultrasonic tomographic image or an ultrasonic Doppler image is formed based on the received signal. Generally, an ultrasonic wave is attenuated according to a propagation distance in a living body, and the attenuation depends on a frequency. That is, the higher the frequency, the greater the attenuation. Therefore, when measuring a deep part in the living body, it is desirable to lower the center frequency of the ultrasonic wave,
In that case, there is a problem that the spatial resolution is reduced.

[0003] US Pat. No. 5,014,712 discloses an ultrasonic diagnostic apparatus to which a technique of coding a transmission signal and performing compression (correlation calculation) on the received signal using the code is used. It has been disclosed. Here, the transmission signal is a rectangular pulse train representing the code itself, which is supplied to the ultrasonic transducer (direct code system). Therefore, since many harmonics are included in the transmission signal, the problem is that the pulse waveform of the transmission signal cannot be reproduced as an ultrasonic pulse unless an ultrasonic transducer having an extremely wide operable frequency band is used. is there. The reproducibility greatly affects the correlation calculation accuracy at the time of receiving signal processing. Incidentally, this publication also mentions multi-stage transmission focus and the like.

Japanese Patent Publication No. 7-81992 discloses an ultrasonic measuring apparatus used for nondestructive inspection and the like.
In this device, a code is represented by a combination of phases of a sine wave, and the code is used as a transmission signal. That is, a phase modulation method is adopted using one transmission frequency. However, since the connection points of the sine waves having different phases are bent, that is, the sine waves are not connected smoothly, harmonics are generated, and the same problem as described above is pointed out. In addition, U.S. Pat. No. 4,788,981, JP-A-11-309145, JP-A-11-3
Japanese Patent Application Publication No. 09146 discloses a related technique.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to improve the quality of an ultrasonic image (particularly, the quality of a deep portion) without deteriorating the spatial resolution.

[0006]

(1) In order to achieve the above object, the present invention provides a transmitter / receiver for transmitting / receiving ultrasonic waves and a predetermined code sequence different from each other for the transmitter / receiver. A transmitting unit that supplies a coded transmission signal represented by a plurality of waves having a frequency, thereby transmitting an ultrasonic wave having a waveform corresponding to the coded transmission signal from the transducer; and For a received signal from a wave filter, using a reference signal representing the waveform of the coded transmission signal, a compression operation unit that performs a compression operation, and forming an ultrasound image using the signal after the compression operation And an image forming unit.

[0007] According to the above configuration, the transmission signal is frequency-modulated according to the predetermined code sequence, and the received signal is compressed based on the predetermined code sequence. Thereby, the spatial resolution can be improved, and the image quality of the ultrasonic image can be improved.
According to the present invention, since the coded transmission signal is represented as a combination of waves having a plurality of frequencies, generation of harmonics is reduced.

Preferably, the compression operation section is a circuit that performs a cross-correlation operation between the reference signal and the received signal. Desirably, the compression operation unit, for a plurality of memory elements that sequentially store each echo data constituting the received signal in chronological order, for the echo data string output in parallel from the plurality of memory elements, It includes a plurality of multipliers for multiplying a coefficient sequence as a reference signal, and an adder for adding the multiplication results of the plurality of multipliers.

Preferably, the compression operation section includes a converter for converting the received signal into a signal on a frequency axis, and a signal representing the received signal converted on the frequency axis and the reference signal on a frequency axis. And an inverter for returning the multiplied signal to a signal on the time axis. That is, the compression operation (cross-correlation operation) may be performed on the time axis or may be performed on the frequency axis.

Preferably, the plurality of frequencies are set within an operating band of the transducer. Because the coded transmission signal is composed of sine waves, it is possible to transmit and receive ultrasonic waves using a transducer that has a general use band, and specially use a broadband transducer. No need to prepare.

Preferably, the predetermined code sequence is a code sequence whose autocorrelation value is maximum at a certain point. As the code sequence, various known sequences can be used.

(2) To achieve the above object,
The present invention provides a coded transmission signal in which a predetermined code sequence is represented by a plurality of frequencies and a waveform is connected between codes to the transducer, whereby the code is transmitted from the transducer. A transmitting unit for transmitting an ultrasonic wave having a waveform corresponding to a coded transmission signal, and performing a compression operation on a reception signal from the transducer using a reference signal representing a waveform of the coded transmission signal. It is characterized by including a compression operation unit, and an image forming unit that forms an ultrasonic image using the signal after the compression operation.

According to the above configuration, since the waveform is connected between the codes in the coded transmission signal, generation of harmonics can be suppressed.

[0014] Preferably, the coded transmission signal represents the predetermined code sequence by combining sine waves having a plurality of frequencies, and a rear end of the preceding sine wave and a front end of the subsequent sine wave are formed. The phase of each sine wave is adjusted so as to continue smoothly.

According to this configuration, the sine wave is used as a code element, and the phase is adjusted so that no edge is generated at the joint between the sine waves (corresponding to so-called shift keying). It can be extremely suppressed.

(3) To achieve the above object,
The present invention is based on a combination of a plurality of transducers, a transducer for transmitting and receiving ultrasonic waves, and a combination of a plurality of frequencies constituting a first frequency group with respect to the transducer. , And a second coded transmission signal representing the second code sequence with a plurality of frequencies constituting a second frequency group, thereby simultaneously supplying a plurality of signals. A plurality of transmitting units for simultaneously forming transmission beams, and means for simultaneously forming a plurality of reception beams, wherein phasing addition is performed for each of the plurality of reception signals output from the transducer. A plurality of receivers, and a cross-correlation calculation using a first reference signal representing a waveform of the first coded transmission signal with respect to the reception signals after the phasing addition from the plurality of receivers, and 2-coded transmission A plurality of cross-correlation calculation unit for executing the alternating correlation operation using the second reference signal representing the No. of the waveform,
An image forming unit that forms an ultrasonic image based on each signal after the correlation operation.

According to the above configuration, a plurality of transmission beams and a plurality of reception beams can be simultaneously formed to improve the spatial resolution in the beam scanning direction or the frame rate. The first coded transmission signal and the second coded transmission signal are:
In the received signal processing after the transmission, it is only necessary to be able to identify (discriminate) each other.

(4) The basic principle of the present invention is to apply the pulse compression technique to ultrasonic diagnosis and to improve the spatial resolution even in a deep region where observation is generally difficult. In a preferred aspect of the present invention, when a code sequence (predetermined code) composed of binary values of 1 or 0 (or -1) is represented by a combination of two frequencies consisting of a sine wave (sine wave),
A phase adjustment is performed for each sine wave so that the trailing end of the leading sine wave and the leading end of the succeeding sine wave are smoothly continuous, and the coded transmission signal generated thereby is supplied to the transducer,
Ultrasonic waves having a waveform corresponding to the coded transmission signal are transmitted into a living body. Reflected waves (ultrasonic waves) from the body
Is received by the transmitter / receiver, and a reception signal corresponding to the waveform of the reflected wave is obtained. A cross-correlation operation is performed on the received signal using a reference signal representing the waveform of the coded transmission signal, thereby compressing the received signal. That is, it compresses the energy of the ultrasonic wave and improves the SNR (signal-to-noise ratio). Then, based on the received signal after compression, an ultrasonic image such as a B-mode image or a Doppler image is formed. In the above configuration, the modulation of the transmission wave and the demodulation of the reception wave are performed to increase the detection sensitivity while maintaining a high spatial resolution, and the sine wave whose phase has been adjusted is used as a code element. Generation of harmonics due to discontinuities or edges of the signal waveform can be effectively suppressed. As a result, the problem of the band in the transducer can be solved and the image quality of the ultrasonic image can be improved. As the predetermined code,
Various well-known types in which the autocorrelation value is maximized at a certain point can be used.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

First, the principle of the present invention will be described. Consider a code sequence that has a maximum autocorrelation value at only one point. As such a code sequence, various types such as a Barker sequence, a Gold sequence, and an M sequence have been proposed. Below is the Maximum
Length Shift Register series (called M series)
Will be described. This sequence can be generated by, for example, a simple circuit as shown in FIG. 1, and specifically, is generated cyclically using shift registers 4, 5, and 6 and an exclusive OR circuit 7. be able to. The length of the code sequence is as follows, where k is the number of stages of the shift registers 4, 5, and 6.
2 ^k -1. Since k = 3 in the example of FIG. 1, the code sequence length generated from the circuit is 7. In FIG. 1, if the initial values of all the shift registers 4, 5, and 6 are 1, ｛1,
A sequence of 1,1,0,0,1,0｝ is repeatedly generated.

Two patterns of {1,1,1,0,0,1,0} are prepared, and the autocorrelation value R (τ) is calculated according to the following equation (1) while shifting their positional relationship. The result of the calculation is as shown in FIG. However, at the time of the autocorrelation calculation, the calculation was performed with 0 as -1. As a result, a peak occurs every seven points, and all others take -1.

[0022]

(Equation 1) Here, p (t): code sequence, t1: start time of autocorrelation calculation.

As described above, when the autocorrelation operation is performed, a sharp peak occurs when the pattern is completely fitted. Although the amplitude of the code sequence is ± 1, seven times the amplitude corresponding to the code sequence length is obtained. This corresponds to a kind of energy compression and is called pulse compression. If this is applied, only the signal component can be effectively extracted from the low SNR waveform.

In general, the signal component power in the conventional method is represented by S1,
Assuming that the noise component is N1, the signal component power after pulse compression is S2, the noise component is N2, and the expansion ratio of the signal time length (corresponding to the code sequence length in the above) is M, the following equation (2) And the SNR can be improved by a factor of M.

[0025]

(Equation 2) In a preferred embodiment of the present invention, a unique frequency is assigned to each code value of the code sequence, and a sine wave of the assigned frequency is transmitted by burst transmission. That is, the conversion from the code value to the frequency is performed. Then, a cross-correlation operation is performed between the reflected signal obtained by the burst transmission and the transmitted sine wave train, thereby performing pulse compression. As a prerequisite, the phase of the waveform for each code is further adjusted so that the phases of adjacent waveforms in the sine wave train are continuous.
This will be described with reference to FIG.

In FIG. 3, (a) shows a code sequence, and (b) shows a signal waveform when frequencies f1 and f2 are simply assigned to each code (without phase adjustment). . (C) shows a signal waveform obtained as a result of performing a phase adjustment on the signal waveform of (b) so that the waveform becomes smooth between adjacent sine waves.

More specifically, the code sequence shown in (a) is an M-sequence code having a code sequence length of seven. This code sequence is +1
And -1. The time of one section of the code sequence is defined as To.

Next, a frequency f1 is assigned to +1.
The frequency f2 is assigned to -1. This is the waveform shown in FIG. In this example, f1 = 5 * (f2) / 4. Of course, other relationships may be used. The thus obtained sine wave train can be burst-transmitted at the transmission repetition cycle of the ultrasonic diagnostic apparatus.

The waveform s (t) of (b) is expressed by the following equation (3).

[0030]

(Equation 3) Where ω ₁ = 2 * π * f ₁ and ω ₂ = 2 * π * f ₂ and n (i)
= [1,1,1,0,0,1,0] (where i = 0,1, ..., 6)
θ _1i : initial phase, θ _2i : initial phase.

In the waveform (b), the boundary of each sine wave is discontinuous, and a harmonic is generated at that portion. Therefore, the waveform obtained by making the waveform continuous between adjacent sine waves is (c).
5 is a waveform shown in FIG. In the waveform, the phase of the succeeding sine wave is adjusted such that the trailing end of the preceding sine wave is connected to the leading end of the succeeding sine wave.

Specifically, in the waveform (b), since the discontinuity occurs at the boundary between i = 0 and 1, the phase of the waveform in the region of i = 1 is shifted by + π / 2. Similarly, the phase of the waveform in the region of i = 2 is + π, and the phase of the waveform in the region of i = 3 is + π.
The phase of the waveform in the region of 3 * π / 2, i = 4 is + 3 * π /
2, and the phase of the waveform in the region of i = 5 is shifted by + 3 * π / 2.

By supplying a burst signal (coded transmission signal) having a waveform as shown in (c) to the ultrasonic vibrator, it is possible to generate an ultrasonic wave with less harmonic distortion. In that case, a cross-correlation operation is performed between the received signal and the reference signal having the waveform (c), thereby compressing the signal energy of the ultrasonic wave.

In FIG. 4, the spectrum of the waveform shown in FIG. 3B is represented by a thin line, and the spectrum of the waveform shown in FIG. 3C is represented by a thick line. The horizontal axis in FIG. 4 corresponds to the frequency, and represents a range from 0 to 2 * f1. The vertical axis is logarithmic and represents the power of each frequency component. Looking at the spectrum of the thin line, a swell is observed near the return frequency. This is shown in FIG.
This is because the waveform has a discontinuous portion, and a harmonic is generated due to the discontinuous portion.

Generally, the frequency bandwidth of an ultrasonic transducer is
Since the -6 dB ratio band is not as wide as about 60%, it is advantageous that the frequency bandwidth of the transmission waveform be as narrow as possible in order to faithfully transmit and receive the transmission waveform. Therefore,
The waveform shown in FIG. 3C is one in which the discontinuity of the transmission waveform is avoided and the frequency bandwidth of the transmission waveform is narrowed.

Looking at the spectrum of the waveform (c) shown by the thick line in FIG. 4, the spectrum is smaller than that of the thin line.
It can be seen that high frequency components are greatly attenuated. By doing so, it becomes possible to narrow the frequency bandwidth of the signal, and it is possible to perform transmission and reception sufficiently even with a normal vibrator.

FIG. 5 shows a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention, and FIG. 5 is a block diagram showing the overall configuration.

In FIG. 5, the array vibrator 10 includes a plurality of vibrating elements 10a. The transmission unit 12
In the present embodiment, the transmission signal generation unit 16 includes a plurality of transmission amplifiers 18 provided for the respective vibration elements 10a (channels).

Here, the transmission signal generator 16 will be described later with reference to FIG.
, A transmission waveform generator provided for each channel.

The receiving section 14 includes a plurality of input protectors 20 provided for each channel, a plurality of receiving amplifiers 22 provided for each channel, and a receiving beamformer 24. The input protector 20 is a circuit for preventing the transmission signal from wrapping around and protecting the receiving unit 14. The reception beamformer 24 is a circuit for electronically forming a reception beam by performing phasing addition on a reception signal for each channel, as will be described later with reference to FIG.

The reception signal after the phasing addition output from the reception beam former 24 is input to the compression calculator 26. As will be described later with reference to FIG. 8, the compression calculator 26 is a circuit that performs a cross-correlation calculation on the received signal and the reference signal representing the waveform of the coded transmission signal. The received signal output from the compression calculator 26 is input to a beam processor 28 described later with reference to FIG. 9, and the received signal output from the beam processor 28 is
Is input to The scan converter 30 has a coordinate conversion function, an interpolation function, and the like.
An ultrasonic image, such as a B-mode image, is formed by the action of, and the image is displayed on the display device 32.

FIG. 6 shows the transmission signal generator 16 shown in FIG.
Is shown. Transmission signal generator 16
Is the timing control unit 36 in the example shown in FIG.
And a transmission waveform generator 34 provided for each channel.
It is composed of The transmission waveform generator 34 includes a memory table 38, a DA converter 40, a low-pass filter (LPF) 42, and an attenuator 44.
In the memory table 38, the transmission waveform shown in FIG. 3C is stored as digital data. In this regard, digital data of a transmission waveform that is delayed by a set time in order to form a transmission beam and change the transmission beam is stored. The waveform data read from the memory table 38 is input to the DA converter 40, and a transmission waveform as an analog signal is generated by the operation of the DA converter 40. This corresponds to the waveform shown in FIG. Low-pass filter 42
Removes a frequency component corresponding to the read rate from the memory table 38. The attenuator 44 is a circuit for performing on / off control for aperture control, weighting for improving ultrasonic beam characteristics, amplitude control for overall transmission amplitude control, and the like. The transmission signal (coded transmission signal) output from the transmission waveform generator 34 is supplied to the vibration element 10a via the transmission amplifier 18 shown in FIG.

The timing controller 36 controls the read timing of the memory table 38 of each transmission waveform generator 34. By appropriately adjusting the read timing, focusing of the transmission beam, deflection of the transmission beam, and the like can be performed. Alternatively, a plurality of memory tables 3 storing different transmission conditions
8 and the transmission condition may be changed by selecting any one of the memory tables 38. Various known methods can be used for such transmission control. In the present embodiment, the memory table 38 is provided for each channel. However, a single memory table 38 is provided.
By adjusting the amount of delay with respect to the signal of the transmission waveform generated therefrom for each channel, the transmission signal of each channel may be generated.

FIG. 7 shows a specific configuration example of the reception beam former 24 shown in FIG. The reception beamformer 24 includes a low-pass filter (LPF) 50 provided for each channel, a plurality of AD converters 52 provided for each channel, a data interpolator 54 provided for each channel, Delay line 5
6 and an adder 58 for adding the delayed received signal. The low-pass filter 50 is a filter for removing unnecessary high-frequency components, and the AD converter 52 has a sampling rate of, for example, 4 * f ₂ . That is, it is desirable to set a sampling rate such that aliasing does not occur in the received signal component. The data interpolator 54 performs an interpolation process on the received signal after sampling, and the delay line 56 is a circuit for providing a predetermined delay amount for each channel, thereby realizing phasing addition. .

FIG. 8 shows a specific configuration example of the compression calculator 26 shown in FIG. This compression calculator 26
Is roughly composed of an FIR filter 63 and a memory 64. In the memory 64, for example, FIG.
A waveform obtained by sampling the waveform shown in (c) at 4 * f ₂ is stored. Specifically, 4 * 7 = 28 pieces of sampling data are stored in the cells 64-1 to 64-n. . This sampling data is a reference waveform (reference signal)
It is used as

Meanwhile, FIR filter 63, which is composed of n delay lines 60-1 to 60-n which are connected in series, the amount corresponding to one wavelength of each delay line 4 * f ₂ It has a delay time. Each delay line has a storage capacity of one word. Here, one word is a bit length of the output digital signal of the reception beam former 24, and is, for example, 16 bits.

The data extracted from the front and rear ends and the middle of each delay line is divided into n multipliers 62-1 to 6-6.
2-n, and the other input terminals of the multipliers 62-1 to 62-n are connected to a memory 64.
Are input from the plurality of cells 64-1 to 64-n. That is, by performing multiplication of two signals in these multipliers, a cross-correlation operation between the received signal and the reference signal can be performed, and the result of the multiplication is added in the adder 66. Thereby, a pulse compression operation is realized. Of course, various methods can be used as the method of the cross-correlation calculation.

In any case, FIG.
Various configuration examples can be adopted as long as the cross-correlation operation can be performed using the reference signal having the waveform shown in (c). As shown in FIG. 2, if such a correlation operation is performed, a strong peak is generated at the time when the pattern of the code sequence matches, thereby greatly improving detection sensitivity while maintaining high spatial resolution. It is possible.

Next, FIG. 9 shows a specific configuration example of the beam processor 28 shown in FIG. The converter 68 is a circuit that compresses the signal output from the compression calculator 26 according to a logarithmic function. That is, such logarithmic conversion is performed in order to adjust the signal amplitude to the display dynamic range of the display device 32.

The adder 70 is a circuit for adding the coefficient α to the signal output from the converter 68, and corresponds to a gain adjustment. The multiplier 72 is a circuit that multiplies the signal output from the adder 70 by a coefficient β.
This corresponds to contrast adjustment. The low-pass filter 74 and the decimator 76 are circuits for implementing a thinning process. When the number of data per beam is excessive, the data cannot be displayed as it is. It is.

As described above, according to the ultrasonic diagnostic apparatus shown in FIG. 5, the detection sensitivity can be improved particularly in the deep part by the frequency modulation and the compression of the received signal.
As shown in (c), since the transmission waveform in which the sine wave is used as an element and the connection between the sine waves is improved is used, generation of unnecessary harmonics can be effectively prevented, and thereby the signal There is an advantage that discrimination accuracy can be improved.

FIG. 10 is a block diagram showing the overall configuration of an ultrasonic diagnostic apparatus according to another embodiment. Note that the same components as those shown in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted. In the configuration example shown in FIG. 10, the output of the compression calculator 26 is input to the quadrature detector 82, and the received signal is converted into a complex signal. The filter unit 84 performs a predetermined filtering on each of the real part signal and the imaginary part signal constituting the complex signal, and the filtered complex signal is sent to the color Doppler operation unit 86 and the spectrum Doppler operation unit 88. Has been entered. The color Doppler computing unit 86 computes information on the average velocity and variance of blood flow using, for example, autocorrelation computation. The spectrum Doppler calculator 88 is, for example, F
This is a circuit that executes an FT operation or the like and performs frequency analysis on echo data for a sample volume set on a tomographic image. The outputs of the color Doppler operation unit 86 and the spectrum Doppler operation unit 88 are output from the scan converter 30.
And the Doppler information is synthesized on the tomographic image as needed. A Doppler image representing the Doppler information is generated by the scan converter 30. These images are displayed on the display device 32.

FIG. 11 shows the quadrature detector 8 shown in FIG.
2, a received signal and a detection signal whose phase is shifted by 90 degrees via a π / 2 phase shifter 94 are mixed in a mixer 90, and the output of the mixer 90 is low. The signal is input to the band-pass filter 96. In the mixer 92, a detection signal is mixed with the received signal, and an output signal of the mixer 92 is input to the low-pass filter 98. Here, the detection signal corresponds to an integral multiple of the repetition frequency of the transmission pulse.

FIG. 12 shows a specific configuration example of the filter section 84. In this example, high-pass filters 100 and 102 are provided for each of the real and imaginary parts.
That is, these high-pass filters 100 and 102 function as so-called wall motion filters, and remove strong echo components of a stationary portion such as a heart wall. Of course, when actively displaying the motion of the tissue such as the heart wall as an image, a low-pass filter may be provided instead of the high-pass filters 100 and 102. Alternatively, both may be dealt with by switching the filter coefficient.

FIG. 13 shows a main configuration of a compression arithmetic unit 104 according to still another embodiment. In each of the above-described embodiments, the cross-correlation calculation is realized on the time axis. However, as shown in FIG. 13, the cross-correlation calculation can be performed on the frequency axis. The pulse compression filter coefficient generator 108 generates a reference signal on the frequency, and the received signal is
At 06, the signal is converted into a signal on the frequency axis, and the received signal and the reference signal are multiplied on the frequency axis. That is, a correlation operation is being performed. The operation result is IF
The signal is input to the FT circuit 112, that is, a circuit that performs inverse Fourier transform, and is restored to the original signal on the frequency axis.

FIG. 14 shows still another embodiment.

First transmitting section 116 and second transmitting section 118
Have the same configuration as the transmission unit 12 shown in FIG. However, the first transmission unit 116 generates the waveform shown in FIG. 3C using the frequencies f1 and f2. On the other hand, the second transmitting unit 118 generates a waveform corresponding to the waveform shown in FIG. 3C using the frequencies f3 and f4. However, these frequencies may be different from each other, or f1 = f3 and f2 = f4 if the code sequence used in the first transmission unit 116 and the code sequence used in the second transmission unit 118 are different.

The array vibrator 120 includes a plurality of vibrating elements 12.
0a, the plurality of vibrating elements 120
a is divided into an A group and a B group in this example. The first transmitting unit 116 is connected to the B group, and the second transmitting unit 118 is connected to the A group. Therefore, the frequencies f1 and f
The frequency-modulated ultrasonic wave having the frequency 2 is transmitted into the living body, and similarly, the frequency-modulated ultrasonic wave with the frequency f3 and the frequency f4 is transmitted into the living body by the group A. . Thus, even if the code sequence is the same, by making the frequencies different, even if two transmission beams are formed at the same time, it becomes possible to discriminate the reception signal corresponding to each transmission beam later.

The first receiving section 122 and the second receiving section 124
Have the same configuration as the receiving unit 14 shown in FIG. Here, the first receiving unit 122 is connected to the B group, and the second receiving unit 124 is connected to the A group. In each of the receiving units 122 and 124, a phasing addition process for forming a reception beam is executed.
The received signal after the processing is input to the compression calculator 126 and the compression calculator 128, respectively.

These compression operation units 126 and 128 have the same configuration as the compression operation unit 26 shown in FIG.
However, in the compression calculator 126, the frequencies f1 and f2
Are performed, and the cross-correlation calculation corresponding to the frequencies f3 and f4 is performed in the compression calculator 128. An ultrasonic image is formed based on the signals after the compression operation.

Therefore, according to the embodiment shown in FIG.
By making the frequencies different, two transmission beams and two reception beams can be formed at once, and as a result, it is possible to improve the spatial resolution or the frame rate. Also, in such an embodiment, basically, the waveform shown in FIG. 3C is used, and the detection sensitivity is improved particularly in a deep part of a living body while effectively suppressing the generation of harmonics. can do.

FIGS. 15 and 16 show still another embodiment. In the embodiment shown in FIG. 14, the array transducers 120 are divided into two groups, but in the embodiments shown in FIGS. 15 and 16, such grouping is not performed. In FIGS. 15 and 16, the same components as those shown in FIG. 14 are denoted by the same reference numerals.

In FIG. 15, the transmission signals of each channel output from first transmission section 116 and second transmission section 118 are added for each channel by adder 130, and the transmission signal after the addition is added to the array vibration. It is supplied to the vibrating element of each channel constituting the child 120. On the other hand, the reception signals of each channel output from the array transducer 120 are input to the first receiving unit 122 and the second receiving unit in parallel, respectively. According to this configuration, the transmitting / receiving aperture (corresponding to the number of vibrating elements (the number of channels) used in one transmission / reception) formed on the array transducer 120 can be increased, so that the detection sensitivity and the spatial resolution can be further improved. .

In the embodiment shown in FIG. 16, one transmission unit 1
Only 17 are used. The transmitting section 117 outputs a composite waveform obtained by adding the waveforms of the two transmission signals. That is, two different transmission frequencies or two different transmission frequencies
The embodiment shown in FIG. 15 is the same as the embodiment shown in FIG. 15 in that a signal having two encoded sequences is supplied to the array transducer 120, but the transmission signal after addition generated in the embodiment shown in FIG. This is different from the embodiment shown in FIG. The configuration relating to the processing of the received signal is the same as that of the embodiment of FIG.

[0065]

As described above, according to the present invention, the image quality of an ultrasonic image can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a basic circuit configuration for generating a code sequence.

FIG. 2 is a diagram showing an autocorrelation value for a code sequence.

FIG. 3 is a diagram for explaining a coded transmission signal according to the present invention.

FIG. 4 is a diagram illustrating a difference in spectrum between a case where phase adjustment is performed and a case where phase adjustment is not performed.

FIG. 5 is a block diagram showing an overall configuration of the ultrasonic diagnostic apparatus.

FIG. 6 is a block diagram illustrating a specific configuration example of a transmission signal generation unit.

FIG. 7 is a diagram illustrating a specific configuration example of a reception beam former.

FIG. 8 is a block diagram illustrating a specific configuration example of a compression arithmetic unit.

FIG. 9 is a block diagram illustrating a specific configuration example of a beam processor.

FIG. 10 is a block diagram illustrating a configuration example of an ultrasonic diagnostic apparatus according to another embodiment.

FIG. 11 is a block diagram illustrating a configuration example of a quadrature detector.

FIG. 12 is a block diagram illustrating a specific configuration example of a filter unit.

FIG. 13 is a block diagram illustrating a main configuration according to another embodiment.

FIG. 14 is a block diagram showing another embodiment of the compression arithmetic unit.

FIG. 15 is a block diagram illustrating a main configuration according to another embodiment.

FIG. 16 is a block diagram illustrating a main configuration according to another embodiment.

[Explanation of symbols]

10 array vibrator, 12 transmitter, 14 receiver, 1
6 transmission signal generator, 18 transmission amplifier, 20 input protector, 22 reception amplifier, 24 reception beamformer, 26 compression calculator, 28 beam processor, 30 scan converter, 32 display device.

Claims (9)

[Claims] 1. A transmitter / receiver for transmitting and receiving ultrasonic waves, and a coded transmission signal representing a predetermined code sequence by a plurality of waves having different frequencies to the transmitter / receiver, A transmitting unit for transmitting an ultrasonic wave having a waveform corresponding to the coded transmission signal from the transducer, and a reference representing a waveform of the coded transmission signal with respect to a reception signal from the transducer. An ultrasonic diagnostic apparatus comprising: a compression operation unit that performs a compression operation using a signal; and an image forming unit that forms an ultrasonic image using the signal after the compression operation. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the compression operation unit is a circuit that performs a cross-correlation operation between the reference signal and the received signal. 3. The apparatus according to claim 2, wherein the compression operation section includes: a plurality of memory elements for sequentially storing echo data constituting the received signal in a time-series order; and a parallel output from the plurality of memory elements. A plurality of multipliers for multiplying the echo data sequence to be performed by the coefficient sequence as the reference signal; and an adder for adding the multiplication results of the plurality of multipliers. apparatus. 4. The apparatus according to claim 2, wherein the compression calculating unit converts the received signal into a signal on a frequency axis, and converts the received signal converted on the frequency axis and the reference signal. An ultrasonic diagnostic apparatus comprising: a multiplier that multiplies a signal represented on a frequency axis; and an inverter that returns the multiplied signal to a signal on a time axis. 5. The ultrasonic diagnostic apparatus according to claim 1, wherein the plurality of frequencies are set within an operating band of the transducer. 6. The ultrasonic diagnostic apparatus according to claim 1, wherein the predetermined code sequence is a code sequence whose autocorrelation value is maximized at a certain point. 7. A transmitter / receiver for transmitting / receiving an ultrasonic wave, and a coded transmission signal in which a predetermined code sequence is represented by a plurality of frequencies and a waveform is connected between codes for the transmitter / receiver. A transmitting unit for transmitting an ultrasonic wave having a waveform corresponding to the coded transmission signal from the transducer, thereby, for a reception signal from the transducer, the coded transmission signal An ultrasonic diagnostic apparatus comprising: a compression operation unit that performs a compression operation using a reference signal representing a waveform; and an image forming unit that forms an ultrasonic image using the signal after the compression operation. . 8. The apparatus according to claim 7, wherein the coded transmission signal represents the predetermined code sequence by combining sine waves having a plurality of frequencies. An ultrasonic diagnostic apparatus, wherein the phase of each sine wave is adjusted so that the front end of the succeeding sine wave is smoothly continued. 9. A transducer comprising a plurality of vibrating elements for transmitting and receiving ultrasonic waves, and a first code sequence for the transducer is represented by a combination of a plurality of frequencies constituting a first frequency group. A first coded transmission signal and a second coded transmission signal representing a second code sequence with a plurality of frequencies constituting a second frequency group, thereby simultaneously providing a plurality of signals in the transducer. A plurality of transmission units for simultaneously forming a plurality of transmission beams, and a means for simultaneously forming a plurality of reception beams, wherein phasing addition is performed for each of the plurality of reception signals output from the transducer by each reception beam. A plurality of receiving units to be executed, for the reception signals after the phasing addition from the plurality of receiving units, a cross-correlation calculation using a first reference signal representing a waveform of the first coded transmission signal, and Second coding A plurality of cross-correlation calculation units that execute a cross-correlation calculation using a second reference signal representing the waveform of the transmission signal; and an image forming unit that forms an ultrasound image based on each signal after the correlation calculation. An ultrasonic diagnostic apparatus comprising: