JP4733446B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to a circuit configuration of a receiving unit used in a continuous wave Doppler mode.

  In the continuous wave Doppler mode, a transmission aperture and a reception aperture are individually set on the array transducer, and ultrasonic waves are continuously transmitted using a plurality of vibration elements in the transmission aperture, and a plurality of oscillations in the reception aperture are transmitted. A reflected wave (continuous wave) from the body is continuously received using the vibration element. Using a technique of electronic focusing and electronic steering, a transmission beam can be formed in a predetermined direction, and a reception beam can be formed in a predetermined direction. Normally, each beam is steered so that the transmission beam and the reception beam cross at the observation site. A transmission beam and a transmission focus are formed by setting a predetermined delay relationship between a plurality of transmission signals applied to a plurality of vibration elements. Similarly, a reception beam and a reception focus are a plurality of receptions applied to a plurality of vibration elements. It is formed by setting a predetermined delay relationship between signals (see Patent Documents 1 and 2).

JP 58-212434 A U.S. Pat. No. 4,598,589

  In general, in the continuous wave Doppler mode, a dedicated receiving unit constituted by an analog circuit is used in consideration of the dynamic range of the received signal. In the reception unit, delay processing and detection processing are performed by performing phase detection processing on each received signal. There is a demand for such a receiving unit to be smaller and cheaper.

  Regarding the continuous wave Doppler mode, conventionally, several phasing and addition methods are known as follows. In the RF phasing addition method using a delay line, a cross point switch is provided between the delay line and the array transducer, and the received signal from each vibration element is one of the delay lines on the delay line by the action of the cross point switch. Input to the tap. That is, selection of a tap corresponds to selection of a delay amount. The number of taps is fixed, and the delay amount associated with each tap is also fixed. A plurality of received signals are phased and added on the delay line, and the phased and added received signal output from the delay line is input to the quadrature detector. According to this configuration, the circuit scale can be made relatively small, but the delay accuracy depends on the ultrasonic frequency (transmission frequency), and the delay accuracy decreases as the frequency increases, that is, the phasing addition accuracy decreases. In addition, it can be pointed out that if the number of delay line taps is increased, the circuit scale increases accordingly. Furthermore, there is a possibility that the S / N ratio may be deteriorated due to reflection caused by impedance mismatch on the delay line.

  In the intermediate frequency phasing addition method, frequency conversion to an intermediate frequency is once performed using a mixer with respect to the received signal from each vibration element. In that case, the phase of the reference signal applied to each mixer is individually adjusted, whereby a delay process is performed for each received signal. After the reception signals output from the mixers are added, the addition signal is input to the quadrature detector. In this configuration, it is necessary to provide a circuit such as a mixer for each vibration element, and it can be pointed out that the circuit scale of the receiving unit increases.

  In the baseband phasing addition method, a reception signal from each vibration element is input to a quadrature detector (a pair of mixers) provided for each vibration element, and each reception signal is converted into a complex signal. In that case, the phase of the complex reference signal applied to each quadrature detector is adjusted for each received signal, whereby delay processing and conversion to baseband are performed for each received signal. The real part signal and the imaginary part signal of each complex signal after the conversion are added in an adder, respectively, thereby obtaining a complex signal after phasing addition. In this configuration, it is necessary to provide a quadrature detector for each vibration element, and it can be pointed out that the circuit scale of the receiving unit increases.

  An object of the present invention is to reduce the circuit scale while ensuring desired signal processing accuracy for a receiving unit that processes a received signal in the continuous wave Doppler mode.

(1) In the present invention, in continuous wave Doppler mode, an array transducer that outputs m reception signals from m vibration elements for reception, and the m reception signals are input, and n (however, a grouping circuit that outputs n group reception signals by performing signal addition for each group by allocating to n groups corresponding to n <m) stages of delay amounts, and the n group reception signals A delay processing unit that outputs n group received signals subjected to delay processing by multiplying n reference signals having n stages of phase difference relationships corresponding to the n stages of delay amounts; And an adder that outputs the reception signal after the phasing addition by adding the delay-processed n group reception signals.

  According to the above configuration, in the continuous wave (CW) Doppler mode, generally, the transmitting vibration element array and the receiving vibration element array are set on the array vibrator. Ultrasonic waves are continuously transmitted into the living body using the transmitting vibration element array, and reflected waves from the living body are continuously received using the receiving vibration element array. The transmitting vibration element array and the receiving vibration element array can be appropriately set according to transmission / reception conditions and applications. For example, a plurality of ineffective vibration elements that do not function in transmission / reception are set between them for acoustic isolation. You may make it do. It is desirable to apply an electronic focusing technique and an electronic steering technique for forming the transmission beam and the reception beam. The array transducer may be a 1D array transducer, a 2D array transducer, or another transducer.

  A grouping circuit is provided at the subsequent stage of the array transducer. The grouping circuit is preferably configured by a cross point switch circuit or the like, and the grouping circuit groups, for example, tens or hundreds of input signals (reception signals) into a predetermined number (n) according to each delay time. For example, if n is 8, each received signal is assigned to 8 groups divided by delay time intervals corresponding to 1/8 of one wavelength, that is, λ / 8. By this grouping, it is only necessary to delay the n group received signals regardless of the number of vibration elements, so that the circuit scale can be made very small. It is desirable to provide a circuit for converting each received signal from a voltage signal to a current signal before the grouping circuit, and to provide a circuit for converting each group received signal from the current signal to the voltage signal after the grouping circuit. However, various configurations can be adopted as a configuration for grouping and a signal form therefor.

  The delay processing unit performs delay processing on the n group received signals using the corresponding reference signals. The phases of the plurality of reference signals are set stepwise (in n steps), and the frequency of each reference signal is set as a transmission frequency or an intermediate frequency adapted thereto. Even if the transmission frequency is changed, the delay processing condition is adaptively set accordingly, so that the problem that occurs when the delay time pitch is fixed as in the case of using the delay line can be solved. That is, basically, a resolution of λ / n can be obtained at any transmission frequency (λ is the wavelength of ultrasonic waves). The delay processing may convert the received signal from an RF signal to a baseband signal, or may convert the received signal from an RF signal to an intermediate frequency signal. Conversion to a complex signal may be performed in the delay processing. In the adding unit, the n group received signals after the delay processing are added, and thereby the phasing addition processing is completed. If necessary, quadrature detection processing is applied to the received signal after the addition. The above n can be appropriately set according to the phasing addition accuracy. However, in order to obtain a certain degree of phasing addition accuracy, n is desirably 4 or more, and from the viewpoint of preventing an increase in circuit scale. n is preferably 16 or less.

(2) In the present invention, in continuous wave Doppler mode, an array transducer that outputs m received signals from m vibrating elements for reception, and the m received signals are input, and n (however, a grouping circuit that outputs n group reception signals by performing signal addition for each group by allocating to n groups corresponding to n <m) stages of delay amounts, and the n group reception signals A delay processing unit for outputting n complex group reception signals subjected to delay processing by multiplying n complex reference signals having n phase differences corresponding to the n stages of delay amounts, And an addition unit that outputs the complex reception signal after phasing addition by adding the delay-processed n complex group reception signals for each real part and imaginary part.

  According to the above configuration, each group received signal can be converted into a complex signal at the stage of delay processing. Therefore, it is not necessary to provide a complex signal converter as a quadrature detector in the subsequent stage.

(3) In the present invention, in the continuous wave Doppler mode, an array transducer that outputs m reception signals from m vibration elements for reception, and the m reception signals are input, and n (however, a grouping circuit that outputs n group reception signals by performing signal addition for each group by allocating to n groups corresponding to n <m) stages of delay amounts, and the n group reception signals A delay processing unit that outputs n group signals subjected to delay processing by multiplying n intermediate reference signals having n stages of phase difference relationships corresponding to the n stages of delay amounts; By adding n complex group reception signals subjected to delay processing, an addition unit that outputs a reception signal after phasing addition, and multiplying the reception signal after phasing addition by a complex reference signal, This allows phasing A quadrature detection section for outputting a complex reception signal after calculation, characterized in that it comprises a.

  According to the above configuration, the delay process is performed at the stage of conversion to the intermediate frequency, and then the group signal after the delay process is added. Then, after the addition, conversion into a complex signal is performed.

(4) Preferably, the grouping circuit is configured by a cross point switch circuit, and a first signal conversion unit that converts each received signal from a voltage signal to a current signal is provided in a preceding stage of the cross point switch circuit, A second signal converter for converting each group received signal from a current signal to a voltage signal is provided at the subsequent stage of the crosspoint switch. Preferably, the n is 4 or more and 16 or less.

  As described above, since the delay process can be performed without using the delay line, the problem that the delay accuracy fluctuates depending on the frequency can be solved, and a decrease in the S / N ratio can be prevented. In particular, since the desired delay accuracy can be realized with a relatively small circuit configuration, the receiving unit can be manufactured at low cost and has high practical value. Note that n should be increased when priority is given to delay accuracy, and n should be reduced when priority is given to reduction in circuit scale.

  When a crosspoint switch is used, it is desirable to use a table storing switching patterns for each reception condition so that a switching pattern suitable for the reception condition can be instantly identified from the set reception conditions. In generating the reference signal set, a circuit for generating the frequency of the reference signal and a circuit for changing the phase of the frequency in stages may be provided, or a plurality of reference signals having different phases in stages. Alternatively, a circuit that simultaneously generates can be used.

  As described above, according to the present invention, it is possible to reduce the circuit scale while ensuring desired signal processing accuracy for the receiving unit that processes the received signal in the continuous wave Doppler mode.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the overall configuration of an ultrasonic diagnostic apparatus according to the present invention. This ultrasonic diagnostic apparatus has a continuous wave Doppler mode, which will be described in detail below, as well as a B mode, an M mode, a CFM (color flow mapping) mode, etc., but the corresponding configurations are not shown. Has been.

  The array transducer 10 is configured as a 1D array transducer in this embodiment. The array transducer 10 includes a plurality of vibration elements 10a arranged linearly or in an arc shape. The array transducer 10 is provided in a probe (not shown), and the probe is used in contact with the body surface or inserted into a body cavity. Instead of the 1D array transducer, a 2D array transducer may be provided.

  On the array transducer 10, a transmission signal element array 12 constituting a transmission aperture and a reception oscillation element array 14 constituting a reception aperture are set. The transmission vibration element array 12 and the reception vibration element array 14 are configured by a plurality (for example, 32) of vibration elements 10a. A plurality of reactive vibration elements corresponding to a gap region for acoustic isolation may be provided between them. For example, in the B mode or the like, the plurality of vibration elements 10a constituting the 1D array vibrator function at the time of transmission and reception, respectively, but in the continuous wave Doppler mode, the plurality of vibration elements are divided into two, and the transmission vibration element An ultrasonic wave is continuously transmitted by the row 12, thereby forming a transmission beam. In addition, continuous ultrasonic waves from inside the body are received by the reception vibration element array 14, thereby forming a reception beam. In FIG. 1, m represents the number of vibration elements constituting the reception vibration element array 14.

  A transmitter and a receiver are provided to form a transmit beam and a receive beam. In the present embodiment, a CW (continuous wave) transmitter 16 and a CW receiver 18 are provided. The CW transmitter 16 supplies a plurality of transmission signals (continuous waves) with a predetermined delay relationship to the plurality of vibration elements constituting the transmission vibration element array 12. On the other hand, the CW receiver 18 performs phasing addition processing on a plurality of reception signals output from a plurality of vibration elements constituting the reception vibration element array 14. This will be described in detail below. The control unit 20 controls the operation of each component shown in FIG. 1. In particular, in addition to the control of the CW transmission unit 16, the control of the crosspoint switch 24 and the reference signal generation unit 34 in the CW reception unit 18. It is carried out.

  The CW receiving unit 18 will be described in detail below. A plurality of reception signals output from the reception vibration element array 14 are input to the VI converter 22. The V-I converter 22 performs conversion from a voltage signal to a current signal for each received signal. That is, the received signal as a voltage signal is converted into a received signal as a current signal. This corresponds to preprocessing for adding a plurality of reception signals for each group in the cross point switch 24 in the subsequent stage.

  The crosspoint switch 24 has a function of grouping m received signals that are input into n groups. In this embodiment, n is 8. That is, in order to perform delay processing at every n stages within one wavelength, the crosspoint switch 24 groups a plurality of received signals into n. n is preferably 4 or more and 16 or less, and particularly preferably n is 8. For example, 32 received signals are converted into 8 group received signals. Each group is composed of one or a plurality of reception signals depending on the reception conditions, but there may be an exception in which a group with zero reception signals may occur. The cross point switch 24 includes a plurality of switches provided at each intersection between the m input lines and the n output lines, and a control in which the entire switching pattern is output from the control unit 20. Determined by signal 26. In the present embodiment, a table storing switching patterns determined for each reception condition is provided in the control unit 20, and when the reception condition is determined, a switching pattern corresponding to the reception condition is determined, The pattern is set in the cross point switch 24. The reception condition is defined by the steering angle and focus depth of the reception beam.

  The IV converter 28 converts the n group received signals output from the crosspoint switch 24 from current signals to voltage signals. As a result, n group received signals as voltage signals are output.

  In the configuration example shown in FIG. 1, n orthogonal detectors 32 are provided in parallel at the subsequent stage of the IV converter 28. That is, a quadrature detector 32 is provided for each group received signal. The plurality of quadrature detectors 32 constitute a quadrature detection unit 30. Each quadrature detector 32 performs quadrature detection on the input group reception signal, thereby performing conversion of the group reception signal to baseband and a reference signal (complex reference signal) mixed with the group signal. By appropriately setting the phase, a different delay amount is given to each group reception signal.

That is, in the present embodiment, eight quadrature detectors 32 from the first to the eighth are provided, and each quadrature detector 32 has a mixer 40 for a real part and a mixer 42 for an imaginary part. . Further, a band pass filter (BPF) or a low pass filter (LPF) is provided at the subsequent stage of each mixer 40, 42, but these are not shown in FIG. 1 for simplification. In each quadrature detector 32, each mixer 40, 42 is configured as a multiplier, and each multiplier 40, 42 mixes a reference signal with an input group reception signal. Specifically, the reference signal 36 is configured as a complex reference signal, that is, a cos signal and a sin signal. The latter signal is obtained by performing a 90 degree phase shift on the former signal. For this reason, a phase shifter 38 is provided. Here, as the transmission frequency F _0, the eight phases of up to phi ₁ to [phi] ₈ are is defined in stages, i.e., in between the eight reference signal, only the phase is different. In the present embodiment, phases corresponding to eight delay amounts from λ / 8 to 8λ / 8 are set, and eight reference signals having different phases are applied to the eight quadrature detectors 32, respectively. It has been. That is, the delay time for each group signal is adjusted by changing the phase of the reference signal used in quadrature detection. Therefore, if the number of n is increased, the delay accuracy can be further improved. On the other hand, if the number of n is reduced, the circuit scale can be reduced. However, there is no problem that the delay accuracy varies depending on the frequency when the frequency is different as in the conventional phasing and adding circuit using the delay line.

  The reference signal generator 34 supplies a reference signal 36 having a predetermined phase to each of the plurality of quadrature detectors 32. As described above, the sin signal is generated from the cos signal by the phase shifter 38, but the reference signal generation unit 34 may generate a pair of cos signal and sin signal that are 90 degrees out of phase. The reference signal generation unit 34 may be configured by a circuit that generates a basic frequency signal and a circuit that changes the phase of the frequency signal in stages, or a plurality of reference signals having different phases. May be configured as a circuit that simultaneously generates. In any case, it is desirable to provide a circuit that varies the frequency of each reference signal depending on the transmission frequency of the ultrasonic wave.

  As described above, each quadrature detector 32 converts the group reception signal into a group complex reception signal subjected to delay processing. The real part signal in each group complex reception signal is output to the adder 44, and the imaginary part signal is output to the adder 46. The adder 44 performs addition of eight real part signals in this embodiment, and outputs the real part signal I after addition. The adder 46 adds eight imaginary part signals in the present embodiment, and outputs an imaginary part signal Q after the addition. The real part signal I and the imaginary part signal Q constitute a complex signal after phasing addition processing.

  The FFT analysis unit 48 receives the real part signal I and the imaginary part signal Q, and performs a frequency analysis by executing a known complex FFT operation. As a result, the frequency spectrum of the received signal (Doppler information) is obtained at each time. The display processing unit 50 generates a known Doppler waveform based on the frequency spectrum at each time, and the Doppler waveform is displayed on the display 52.

  In the above configuration, since no delay line is used, it is possible to avoid the problem of deterioration of the S / N ratio due to impedance mismatch that has occurred on the delay line as in the prior art, and depending on the frequency. The problem that the delay accuracy changes, that is, the problem that the phasing addition accuracy varies depending on the frequency can be prevented. Further, in terms of circuit scale, since a large number of received signals are grouped into n in the crosspoint switch 24 and a delay process can be performed for each group, each of the received signals is individually delayed. The circuit scale can be significantly reduced as compared with the conventional configuration that performs the above. In the configuration shown in FIG. 1, an A / D converter is preferably provided after the adders 44 and 46, but conversion from an analog signal to a digital signal can be performed at any other desired location. is there. In the configuration of FIG. 1, the preamplifier provided between the reception vibration element array 14 and the VI converter 22 is not illustrated, and other detailed circuit configurations are also not illustrated. .

  In the configuration of FIG. 1, when a transmission frequency is set, the reference signal generation unit 34 generates a reference signal set corresponding to the transmission frequency. On the other hand, when the direction of the reception beam and the depth of the reception focus point are set, the switching pattern in the cross point switch 24 is set. In the state where the reception focus point is fixed, the reference signal set is continuously generated as it is, and when the transmission frequency is changed, the frequency of the reference signal is adaptively variably set (updated) accordingly. Will be.

  Next, another embodiment of the receiving unit will be described with reference to FIG. Regarding the CW receiving unit 60 shown in FIG. 2, the same components as those shown in FIG. In FIG. 2, the configuration of the array transducer 10 and the display processing unit 50 is not illustrated.

  In the CW receiving unit 60 shown in FIG. 2, the VI converter 22, the crosspoint switch 24, and the IV converter 28 are provided as in the embodiment shown in FIG. That is, m received signals are grouped into n groups, and n group received signals are obtained. The intermediate frequency conversion unit includes a mixer group 62 and a BPF group 66. In the present embodiment, eight mixers 64 and eight BPFs 68 are provided. That is, a mixer 64 and a BPF 68 are provided for each group received signal.

The first reference signal output from the first reference signal generation unit 70 is input to each mixer 64, and is mixed with the group reception signal. The first reference signal is configured as a cos signal, and its frequency F ₁ is a frequency for performing conversion to an intermediate frequency. The phases φ _{1 to} φ ₈ in each cos signal correspond to phase information for determining the delay amount. As in the embodiment shown in FIG. 1, eight stages of phases are set, that is, eight delay amounts from λ / 8 to 8λ / 8 are set. Each BPF 68 extracts necessary signal components after mixing.

In the adder 74, the group reception signals subjected to the conversion to the intermediate frequency and the delay processing are added to obtain the added reception signal. The added reception signal is input to the quadrature detector 78. The quadrature detector 78 has two mixers (not shown), that is, two multipliers, and a cos signal and a sin signal are input to each multiplier. In the present embodiment, a sin signal is obtained from the cos signal by performing a 90-degree phase shift in the phase shifter 76 on the signal generated by the second reference signal generation unit 72. Here, F ₂ represents the frequency of the reference signal, and the frequency corresponds to a frequency for performing conversion from the intermediate frequency to the baseband. For example, when the transmission frequency F ₀ is 3 MHz, the above F ₁ is 2 MHz, and in that case, F ₂ is 1 MHz.

  The complex signal composed of the real part signal I and the imaginary part signal Q output from the quadrature detector 78 is input to the FFT analyzer 48, and the same processing as the FFT analyzer 48 shown in FIG. 1 is executed.

According to the configuration shown in FIG. 2, since delay processing can be performed at the stage of frequency conversion to the intermediate frequency, there is no need to provide a pair of mixers for each received signal before the adder 74, and the circuit configuration There is an advantage that can be made smaller. When the transmission signal is changed, either the frequency F ₁ of the first reference signal or the frequency F ₂ of the second reference signal may be adaptively varied. In this case, it can be said that it is desirable to vary the frequency F ₂ of the second reference signal. Also in the circuit configuration shown in FIG. 2, since the delay line is not used as in the prior art, the problem of signal reflection or S / N ratio deterioration due to impedance mismatching or the like occurring on the delay line is prevented. Further, there is an advantage that the problem that the delay accuracy varies depending on the transmission frequency can be prevented. Further, since the circuit scale can be further reduced in terms of circuit scale, there is an advantage that an ultrasonic diagnostic apparatus having a high practical value can be configured by reducing the manufacturing cost of the receiving unit. Note that the configuration examples shown in FIGS. 1 and 2 are suitable examples of the present invention, and various configurations other than that can be adopted. In any case, on the premise of grouping, it is desirable to adopt a configuration in which delay processing can be performed using variable phase in the subsequent stage. In the configuration shown in FIG. 2, an LPF may be provided instead of the BPF 68. Such a filter may be provided after the adder 74. This also applies to the configuration shown in FIG.

1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention. It is a block diagram which shows the structure of the receiving part which concerns on other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Array vibrator | oscillator, 12 Transmission vibration element row | line | column, 14 Reception vibration element row | line | column, 16 CW transmission part, 18 CW reception part, 22 VI converter, 24 crosspoint switch, 28 IV converter, 32 orthogonal Detector, 34 Reference signal generator, 44, 46 Adder, 48 FFT analyzer.

Claims (5)

An array transducer that outputs m received signals from m transducer elements for reception in a continuous wave Doppler mode in which the transmit beam and the receive beam are steered so that the transmit beam and the receive beam cross at the observation site ;
By receiving the m received signals, distributing them to n groups corresponding to n (where n is 4 or more and n <m) stages of delay, and performing signal addition for each group A grouping circuit for outputting n group received signals;
By multiplying the n group received signals by n reference signals having an n-stage phase difference corresponding to the n-stage delay amount, the n group received signals subjected to delay processing are multiplied. A delay processing unit to output;
An adder that outputs the reception signal after phasing addition by adding the n group reception signals subjected to the delay processing;
An ultrasonic diagnostic apparatus comprising: An array transducer that outputs m received signals from m transducer elements for reception in a continuous wave Doppler mode in which the transmit beam and the receive beam are steered so that the transmit beam and the receive beam cross at the observation site ;
By receiving the m received signals, distributing them to n groups corresponding to n (where n is 4 or more and n <m) stages of delay, and performing signal addition for each group A grouping circuit for outputting n group received signals;
Multiplying the n group received signals by n complex reference signals having n stages of phase differences corresponding to the n stages of delay amounts, thereby delaying n complex groups received. A delay processing unit for outputting a signal;
An adder that outputs the complex reception signal after phasing addition by adding the delay-processed n complex group reception signals for each real part and imaginary part;
An ultrasonic diagnostic apparatus comprising: An array transducer that outputs m received signals from m vibrating elements for reception in continuous wave Doppler mode;
The m received signals are input, and are divided into n groups corresponding to n (where n <m) stages of delay amount, and signal addition is performed for each group, thereby receiving n groups. A grouping circuit for outputting signals;
Multiplying the n group received signals by n intermediate reference signals having n stages of phase differences corresponding to the n stages of delay amounts, thereby delaying the n group received signals. A delay processing unit for outputting
An adder that outputs the reception signal after phasing addition by adding the n group reception signals subjected to the delay processing;
The quadrature detection unit that multiplies the reception signal after the phasing addition by a complex reference signal, thereby outputting the complex reception signal after the phasing addition, and
An ultrasonic diagnostic apparatus comprising: The device according to claim 1, 2 or 3,
The grouping circuit is composed of a crosspoint switch circuit,
A first signal conversion unit that converts each received signal from a voltage signal to a current signal is provided in a preceding stage of the crosspoint switch circuit,
A second signal conversion unit that converts each group reception signal from a current signal to a voltage signal is provided at a subsequent stage of the crosspoint switch.
An ultrasonic diagnostic apparatus. The device according to claim 1, 2 or 3,
The ultrasonic diagnostic apparatus, wherein n is 4 or more and 16 or less.

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