JP2005278892A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide ultrasonic diagnostic apparatus where deterioration of S/N caused by a long coaxial cable and deterioration of spatial resolution caused by a small opening for transmitting and receiving ultrasonic waves are improved. <P>SOLUTION: The apparatus is provided with: an ultrasonic transducer 13 consisting of a pair of piezoelectric vibrators 11 and 12; a pulser means 14 for applying voltage to the piezoelectric transducer 11 to generate ultrasonic waves; a received signal processing means 15 for processing a signal by using an ultrasonic received signal received by the pair of piezoelectric vibrators 11 and 12; and a display 25 for displaying an ultrasonic diagnostic image. received signal processing means 15 multiplies the frequency of the ultrasonic received signal received by the pair of piezoelectric transducers 11 and 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic diagnostic apparatus.

Conventionally, as an intracorporeal ultrasonic diagnostic apparatus, an ultrasonic diagnostic image is obtained by performing rotational scanning by transmitting and receiving an ultrasonic beam while mechanically rotating one piezoelectric vibrator arranged at the distal end portion of an endoscope. 2. Description of the Related Art A mechanical scanning intracorporeal ultrasound endoscope for rendering has been proposed.
Also, radial scanning, convex scanning, linear scanning, or sector scanning is performed by arranging a plurality of piezoelectric vibrators in an array at the distal end of the endoscope and switching the piezoelectric vibrators that transmit ultrasonic waves electronically. An electronic scanning intracorporeal ultrasound endoscope that renders an ultrasound diagnostic image has been proposed (see, for example, Patent Document 1).
Further, a thin ultrasonic transducer disposed in the sheath is inserted through the forceps hole of the endoscope, and the sheath is protruded at the distal end portion of the endoscope, and mechanical rotation scanning is performed while contacting the living body surface. A small-diameter probe ultrasonic endoscope for rendering an ultrasonic diagnostic image has been proposed (see, for example, Patent Document 2).
Note that these intra-body-cavity ultrasonic diagnostic apparatuses are used by transmitting and receiving ultrasonic waves through a balloon filled with an acoustic coupling liquid in order to achieve good acoustic connection with the surface of a living tissue.

Of these, the former machine-scanning and electronic-scanning intracorporeal ultrasound endoscopes cannot be applied to thin lumens such as the common bile duct and pancreaticobiliary duct, but are thick such as the esophagus, stomach, duodenum, and large intestine. Can be applied to the lumen.
In addition, a mechanical scanning intracorporeal ultrasound endoscope that mechanically scans a single transducer has high transmission / reception sensitivity, and a good B-mode diagnostic image can be obtained by generating no grating lobes in principle. It is done.
On the other hand, the electronic scanning intracorporeal ultrasound endoscope can increase the frame rate and can perform Doppler blood flow diagnosis. In addition, since the transmitted ultrasonic beam can be controlled in various ways, it is possible to construct a good image by variable focus, transmission / reception separation, and the like. Then, A / D conversion is performed, and image quality improvement is facilitated by various algorithms.
Further, the latter thin probe ultrasonic endoscope can be applied to thin lumens such as the common bile duct and pancreaticobiliary duct.

Moreover, although it is for external use, the scanning method for the purpose of high-depth diagnosis is proposed (for example, refer patent document 3). The outline of this scanning method will be described with reference to FIG.
The scanning method shown in FIG. 20 is for preventing image deterioration in the deep part, and the reception beam convergence point is moved to the deep part with Δy1, Δy2,... .., And by sequentially moving the receiving transducer group R1, R2,... In the arrangement direction from the transmitting ultrasonic transducer group T1, the received beam deflection angle is maintained at a substantially constant θ. The control of the receiving beam convergence point and the center position in the arrangement direction of the receiving transducer groups R1, R2,... Is performed using a transmission / reception switching electronic switch and a reception delay circuit for an in-array reception channel different from the transmission channel. Is done by.
According to the scanning method shown in FIG. 20, the deflection angle of the reception beam can be kept substantially constant, so that the side lobe generation in the reception beam is suppressed by setting the reception beam deflection angle so as not to become too large. In addition, it is possible to avoid image degradation in the deep part of ultrasonic diagnosis.
JP-A-5-277103 (FIG. 1) JP 2003-33353 A (FIG. 2) JP-A-6-125908 (FIG. 1)

However, the conventional ultrasonic diagnostic apparatus has the following problems. That is, in the conventional ultrasonic diagnostic apparatus, since the transducer element is disposed at the distal end of the endoscope, the maximum dimension of the transducer element is slightly smaller than about 10 mmφ which is the diameter of the bellows of the endoscope. When the ultrasonic transducer is not an electronic sector scanning ultrasonic transducer, or the ultrasonic transducer used for the thin probe ultrasonic endoscope, the maximum size thereof needs to be smaller than the forceps hole diameter of 3.9 mmφ. . For this reason, the transmission ultrasonic wave output is limited, and it becomes extremely difficult to obtain a high depth of penetration. Also, an array type ultrasonic transducer also has a very small size per transducer element, depending on the number of transducer elements. Therefore, the output of ultrasonic waves to be transmitted is limited, and it becomes difficult to obtain a high depth of penetration.
In addition, since a coaxial cable of 2 m or more is used, it is essential only for body cavity such as current loss due to displacement current flowing through the capacitance component of the cable and superposition of rf incoming noise due to incomplete electromagnetic shielding of the coaxial cable. There is a significant S / N reduction factor. Furthermore, in the electronic scanning intracorporeal ultrasound endoscope, coaxial cables are bundled and used, so there is an S / N reduction factor called crosstalk between coaxial cables.

  The present invention has been made in view of the above circumstances, and provides an ultrasonic diagnostic apparatus in which a reduction in S / N due to a long coaxial cable and a reduction in spatial resolution due to a small opening for transmitting and receiving ultrasonic waves are improved. The purpose is to do.

  The present invention employs the following configuration in order to solve the above problems. That is, the ultrasonic diagnostic apparatus according to the present invention applies ultrasonic waves to an ultrasonic transducer composed of N (N ≧ 2) transducer elements and m (m ≦ N) transducer elements. Pulsar means for transmitting a signal, reception signal processing means for signal processing using ultrasonic reception signals received by the n (n ≦ N) transducer elements, and a display device for displaying an ultrasonic diagnostic image. The reception signal processing means multiplies the frequency of the ultrasonic reception signal received by the n transducer elements.

  According to this invention, the beam width of the ultrasonic beam can be reduced by multiplying the frequency of the ultrasonic reception signal received by the n transducer elements. Thereby, the horizontal resolution can be improved.

In the ultrasonic diagnostic apparatus according to the present invention, the reception signal processing means performs correlation processing between ultrasonic reception signals received by two or more different transducer elements among the n transducer elements. It is preferable to provide correlation processing means.
According to the present invention, it is possible to remove ultrasonic noise that has come to the coaxial cable by performing correlation processing on a pair of received signals received by two or more different piezoelectric vibrators. This can reduce the noise level of the S / N ratio and improve the S / N ratio. Therefore, a deeper diagnosis in the body cavity can be performed.
Further, by performing correlation processing, the frequency of the received signal after processing is doubled. Thereby, the beam width of the ultrasonic beam is reduced, and the lateral resolution can be improved.

In the ultrasonic diagnostic apparatus according to the present invention, the received signal processing means computes the absolute value of the ultrasonic received signal received by one transducer element among the n transducer elements. It is preferable to include at least one of power detection means, harmonic extraction means for extracting a harmonic component from the ultrasonic reception signal, and frequency multiplication means for multiplying the frequency of the ultrasonic reception signal.
According to the present invention, the power of the ultrasonic reception signal is calculated using the power detection means and the absolute value thereof is calculated. For example, when the power detection means squares the ultrasonic reception signal, The frequency is doubled. Thereby, the beam width of the ultrasonic beam is reduced, and the lateral resolution can be improved. Furthermore, the pulse width of the ultrasonic beam is shortened, and the depth resolution can be improved.
Moreover, the following effects are produced by extracting the harmonic component from the ultrasonic reception signal using the harmonic extraction means. That is, the ultrasonic wave reception signal irradiated from the transducer element includes a harmonic component due to nonlinearity of the biological tissue or the like by passing through the biological tissue or the like. This harmonic component has less variation in sound pressure in the near field than the fundamental component, and the beam width and side lobe level of the ultrasonic beam are small. Therefore, the lateral resolution and the contrast resolution can be improved by extracting the harmonic component from the ultrasonic reception signal.
Further, by multiplying the frequency of the ultrasonic reception signal using the frequency multiplication means, for example, when the frequency is doubled, the frequency of the reception signal after the calculation is doubled. Therefore, the beam width of the ultrasonic beam is reduced, and the lateral resolution is improved.

In the ultrasonic diagnostic apparatus according to the present invention, it is preferable that the signal processing means includes a filter means for removing a high frequency generated by the correlation processing means.
According to this invention, it is possible to remove a high-frequency component generated when correlation processing is performed between two ultrasonic reception signals by the correlation processing means, and an ultrasonic diagnostic image with fewer noise components can be obtained. .

In the ultrasonic diagnostic apparatus according to the present invention, the signal processing means includes addition processing means for adding the ultrasonic reception signals received by the n transducer elements, and the addition processing means It is preferable to add the weighted sound wave reception signal.
According to the present invention, the grating lobes can be reduced by performing, for example, Gaussian distribution weighting or cosine distribution weighting on the ultrasonic reception signals received by the n transducer elements.

In the ultrasonic diagnostic apparatus according to the present invention, it is preferable that the ultrasonic transducer is a small-diameter ultrasonic transducer including the two transducer elements.
According to this invention, it can be set as the thin-diameter ultrasonic transducer with improved S / N ratio.

Further, in the ultrasonic diagnostic apparatus according to the present invention, the ultrasonic transducer includes a ring-shaped vibrator and a disk-shaped vibrator disposed on an inner diameter portion thereof. It is preferable that an ultrasonic wave is transmitted by applying a voltage and received by the ring-shaped piezoelectric vibrator and the disk-shaped vibrator.
According to this invention, the ultrasonic wave transmitted from the ring-shaped vibrator is received by the ring-shaped vibrator and the disk-shaped vibrator.

In the ultrasonic diagnostic apparatus according to the present invention, it is preferable that a ratio of resonance frequencies of the ring-shaped vibrator and the disk-shaped vibrator is 1: k (k ≧ 2).
According to the present invention, the disk-shaped vibrator selectively receives the second harmonic wave, the third harmonic wave, or the fourth harmonic wave component among the ultrasonic waves transmitted from the ring-shaped vibrator. Thereby, a harmonic component can be extracted easily and the resolution in the depth direction can be improved. Here, harmonics higher than the fifth harmonic may be received, but the reception sensitivity is too low, and there is almost no substantial effect.

The ultrasonic diagnostic apparatus according to the present invention is premised on that the correlation processing means performs correlation processing on the ultrasonic reception signals of the two transducer elements adjacent to each other.
According to the present invention, by performing correlation processing between two transducer elements adjacent to each other, it is possible to reduce the phase difference between the two ultrasonic reception signals and to suppress the reduction in the lateral resolution.

In the ultrasonic diagnostic apparatus according to the present invention, it is preferable that the ultrasonic transducer has the N transducer elements arranged in an array.
According to the present invention, of the N transducer elements arranged in an array, ultrasonic waves are transmitted from m transducer elements, and ultrasonic reception signals are received by the n transducer elements.

In the ultrasonic diagnostic apparatus according to the present invention, it is preferable that a mechanical quality factor Qm of the ultrasonic transducer is 30 or more and 300 or less.
According to the present invention, when the mechanical quality factor Qm is 30 or more, the amplitude of the pulse signal can be increased when the ultrasonic signal is transmitted. Moreover, the ratio which is mixed with an unnecessary vibration can be suppressed because it is 300 or less. That is, superimposition of unnecessary vibration noise on the diagnostic ultrasonic signal is suppressed.

In the ultrasonic diagnostic apparatus according to the present invention, it is preferable that the pulsar means applies a trapezoidal waveform or a double rectangular wave as a drive signal to the m transducer elements.
According to the present invention, since the drive signal applied to the transducer element that transmits ultrasonic waves is a trapezoidal waveform, it is possible to suppress the deterioration in resolution in the depth direction due to an increase in the reverberation time of the pulse signal.

The ultrasonic diagnostic apparatus according to the present invention preferably includes Doppler diagnostic means for displaying a Doppler diagnostic image on the display means.
According to the present invention, the diagnostic performance can be further improved by displaying the Doppler diagnostic image together with the ultrasonic diagnostic image.

In addition, the ultrasonic diagnostic apparatus according to the present invention preferably includes harmonic signal Doppler diagnostic means for displaying a harmonic Doppler diagnostic image on the display means.
According to the present invention, a Doppler diagnostic image with improved lateral resolution and contrast resolution can be obtained by using a harmonic signal.

In the ultrasonic diagnostic apparatus according to the present invention, it is preferable that the reception signal processing unit includes an A / D converter that performs analog / digital conversion on an ultrasonic reception signal received by the n transducer elements.
According to the present invention, signal processing with less deterioration can be performed by converting the ultrasonic reception signal into a digital signal by the A / D converter.

In the ultrasonic diagnostic apparatus according to the present invention, it is preferable that the reception signal processing means can process the ultrasonic reception signal converted by the A / D converter.
According to this invention, the received signal processing means performs signal processing on the digital signal converted by the A / D converter.

The ultrasonic diagnostic apparatus according to the present invention includes an orthogonal detection unit that converts the ultrasonic reception signal processed by the reception signal processing unit into reception complex data, a complex data storage unit that stores the reception complex data, Complex data reading means for reading complex data at an approximate position determined by the positional relationship between the n transducer elements and the focal point by the complex data storage means, and the complex data obtained by the complex data reading means It is preferable that a phase correction processing unit that performs phase correction processing of the reception complex data corresponding to an accurate delay time determined by a positional relationship between the n transducer elements and the focal point is preferable.
According to this invention, it is possible to match the variation in the ultrasonic propagation time of the ultrasonic reception signal received by each transducer element, that is, the variation in the phase, and further suppress unnecessary response components such as side lobes.

  The ultrasonic diagnostic apparatus according to the present invention is preferably an intracorporeal ultrasonic diagnostic apparatus used for ultrasonic diagnosis in a body cavity.

According to the ultrasonic diagnostic apparatus of the present invention, the beam width of the ultrasonic beam is reduced by multiplying the frequency of the ultrasonic reception signal received by the n transducer elements. Thereby, the horizontal resolution can be improved.
Further, by performing correlation processing between a pair of received signals received by two different piezoelectric vibrators, high-frequency noise flying on the coaxial cable is removed. This can reduce the noise level of the S / N ratio and improve the S / N ratio.

Next, a first embodiment of the present invention will be described with reference to FIGS.
The ultrasonic diagnostic apparatus according to the present embodiment is an intracorporeal ultrasonic diagnostic apparatus using, for example, a small-diameter ultrasonic probe that can be inserted into a forceps hole of an endoscope.
As shown in FIG. 1, this intra-body-cavity ultrasonic diagnostic apparatus includes a small-diameter ultrasonic probe (ultrasonic transducer) 13 having a pair of piezoelectric vibrators (vibrator elements) 11 and 12, and one piezoelectric vibrator 11. A pulser 14 for applying an ultrasonic transmission drive voltage to the signal, a reception signal processing means 15 for processing an ultrasonic signal received by the pair of piezoelectric vibrators 11 and 12, and a logarithm for amplifying the output from the reception signal processing means 15. An amplifier 21, an envelope detector 22 that detects an envelope of the received signal, an A / D converter 23 that performs analog / digital conversion on the received signal detected by the envelope detector 22, and converts the received signal into an image signal An image converter 24 and a monitor 25 for displaying an ultrasonic diagnostic image are provided.
The piezoelectric vibrator 11 is configured to transmit an ultrasonic wave having a frequency f by the pulser 14. The pair of piezoelectric vibrators 11 and 12 receives the ultrasonic signal having the frequency f and an integer multiple of the frequency f.

  The pair of piezoelectric vibrators 11 and 12 are arranged together with an acoustic coupling liquid in a sheath (not shown), and mechanically rotate around the insertion axis S of the small-diameter ultrasonic probe 13 as a central axis. The configuration is such that an ultrasonic diagnostic image is obtained by transmitting and receiving a sound wave while rotating in the arrow S1 direction. The pair of piezoelectric vibrators 11 and 12 are branched into three via coaxial cables 31 and 32, respectively, and an RF signal processing unit 37, a square wave detection unit 38, and a second harmonic extraction of the processing unit 35 described later. Each of the units 39 is connected.

The reception signal processing means 15 includes a processing means 35 for processing the received ultrasonic signal and an addition processing means 36 for finally converting it into a single reception signal.
The processing means 35 includes an RF signal processing unit 37, a square detection unit 38, and a second harmonic extraction unit 39.
The RF signal processing unit 37 includes a pair of normalization processing means 41 for normalizing the ultrasonic reception signals of the pair of piezoelectric vibrators 11 and 12 so that the maximum value is 1, and the two ultrasonic reception signals. Correlation processing means 42 for performing correlation processing and a low-pass filter (hereinafter abbreviated as LPF) 43 for removing high-frequency components from the correlation processed signal.
The square detection unit 38 includes a pair of square detection means (power detection means) 45 that square-detects the ultrasonic reception signals of the pair of piezoelectric vibrators 11 and 12, respectively, and a square detection ultrasonic reception signal. A pair of normalization processing means 46 that performs normalization processing, a correlation processing means 47 that correlates two ultrasonic reception signals, and an LPF 48 are included.
The second harmonic extraction unit 39 is a second harmonic extraction means (harmonic extraction) that is a pair of bandpass filters that extract the second harmonic components from the ultrasonic signals of the pair of piezoelectric vibrators 11 and 12, respectively. Means) 51, a pair of normalization processing means 52 for normalizing the ultrasonic reception signals extracted from the second harmonic components, a correlation processing means 53 for correlating the two ultrasonic reception signals, and an LPF 54, It consists of

The addition processing means 36 is configured to add the reception signal processed by the square wave detection unit 38, the reception signal processed by the second harmonic extraction unit 39, and the reception signal processed by the RF signal processing unit 37. It has become.
Here, arrows A 1, B 1, D 1, E 1, G 1, and H 1 are ultrasonic reception signals by the pair of piezoelectric vibrators 11 and 12, and arrows A 2 and B 2 are normalized signals that are normalized by the normalization processing means 41. , Arrow C1 indicates a normalized correlation signal subjected to correlation processing by the correlation processing means 42, and arrow C2 indicates a normalized correlation signal from which high-frequency components have been removed by the LPF 43. Arrows D2 and E2 are square detection signals by the square detection means 45, arrows D3 and E3 are normalization square detection signals by the normalization processing means 46, and arrow F1 is a normalization square by the correlation processing means 47. The detection correlation signal, and the arrow F2 indicates a normalized square detection correlation signal from which high-frequency components have been removed by the LPF 48. Arrows G2 and H2 are second harmonic signals from the second harmonic extraction means 51, arrows G3 and H3 are normalized second harmonic signals from the normalization processing means 52, and arrow I1 is from the correlation processing means 53. The normalized second harmonic correlation signal indicates the normalized second harmonic correlation signal, and the arrow I2 indicates the normalized second harmonic correlation signal from which the high frequency component has been removed by the LPF 54. Arrows N1 and N2 indicate rf incoming noise which is high-frequency noise superimposed on the coaxial cables 31 and 32.

First, the RF signal processing unit 37 will be described in detail.
As shown in FIG. 2, rf incoming noises N1 and N2 are superimposed on the coaxial cables 31 and 32 on the reception signals received by the pair of piezoelectric vibrators 11 and 12, respectively, and the ultrasonic reception signals A1 and B1. Become. Then, normalized signals A2 and B2 having a maximum value of 1 are obtained by the normalization processing means 41.
The normalized signals A2 and B2 are almost the same waveform signal because the pair of piezoelectric vibrators 11 and 12 are arranged close to each other. On the other hand, as shown in FIGS. 3A and 3B, the rf incoming noise superimposed on the received signal is slightly different in phase, so the relationship between the normalized signals A2 and B2 is The waveforms of the received signals of the piezoelectric vibrators 11 and 12 are the same and have the same phase, and the rf incoming noise component is superimposed with a slightly different phase even if slightly.
Here, taking the correlation corresponds to taking the product of both signals. As a result, the rf incoming noise components superimposed at different phases become zero by taking the correlation. Further, as shown below, a signal of frequency f is converted into a signal of frequency 2f in the received signal portions having the same phase.

Here, a beam pattern from a single piezoelectric vibrator will be described with reference to FIG.
As shown in FIG. 4A, the piezoelectric vibrator 61 having a width 2a in the rotation direction, a length 2b in the insertion axis direction, and a thickness corresponding to a predetermined resonance frequency is formed on both surfaces of the piezoelectric vibrator 61. A coaxial cable 64 is connected to the pair of electrodes 62 and 63.
The directivity De of the ultrasonic beam possessed by the piezoelectric vibrator 61 is expressed by the following equation.

  Here, k is the wave number, and α and β are elevation angles with respect to the point P in the X axis (width direction) and Y axis (insertion axis direction), as shown in FIG. Here, the wave number k is expressed by the following equation, where f is the frequency and v is the speed of sound in the ultrasonic propagation medium.

  Further, the directivity De only in the width direction is a Sinc function as shown below.

Here, FIG. 4C shows directivity Dea in only the width direction when the width 2a in the rotation direction is 2.4 mm and the frequencies are 5 MHz, 10 MHz, and 15 MHz. In this figure, the directivity value at each frequency indicates the amplitude normalized by the maximum value.
As shown in FIG. 4C, it can be seen that the directivity of the ultrasonic beam becomes sharper as the wave number k increases, that is, as the frequency f increases.

From the above, the correlation processing means 42 narrows the beam width of the ultrasonic beam and contributes to improving the lateral resolution.
Here, the waveforms of the absolute values of the normalized signals A2 and B2 that have been subjected to normalization processing with the maximum value set to 1 by the normalization processing means 41 are as shown in FIG. As shown in FIG. The envelope of the normalized correlation signal C1, which is an output from the correlation processing means 42, is as shown in FIG.
Here, the normal output which is the output of the correlation processing means 42 shown in FIG. 5C is less than the −20 dB pulse width W1, which is a pulse width at a value 20 dB lower than the peak value of the envelope shown in FIG. It can be seen that the -20 dB pulse width W2 of the envelope of the generalized correlation signal C1 is narrower.
The high frequency component generated by the correlation processing means 42 is removed by the LPF 48, and a normalized correlation signal C2 from which the high frequency component has been removed is obtained.
Note that the noise component is more efficiently suppressed by performing normalization by the normalization processing unit 41 before the correlation processing unit 42 performs the correlation processing.

Next, the square detection unit 38 will be described in detail with reference to FIG.
As shown in FIG. 6A, the square detection means 45 performs square detection on the ultrasonic reception signals D1 and E1 received by the pair of piezoelectric vibrators 11 and 12.
The square detection means 45 converts the ultrasonic reception signals D1 and E1 into square detection signals D2 and E2 that are twice the frequency of the ultrasonic reception signals D1 and E1 as in the above-described Expression 4.
That is, the square detection means 45 narrows the beam width of the ultrasonic beam and contributes to improving the lateral resolution.

  A drive signal from the pulsar 14 is applied to the piezoelectric vibrator 11, and the ultrasonic reception signals D1 and E1 received by the pair of piezoelectric vibrators 11 and 12 are square-detected signals D2 and E2 by the square detection means 45, respectively. It becomes. The square detection signals D2 and E2 are normalized by the normalization processing unit 46 to become normalized square detection signals D3 and E3. Furthermore, the normalized square detection correlation signal F1 is obtained by correlating the normalized square detection signals D3 and E3 with the correlation processing means 42. The high frequency component generated by the correlation processing means 42 is removed by the LPF 48, and becomes a normalized squared correlation signal F2 with high resolution and high S / N.

  Since the correlation processing means 47 correlates the normalized square detection signals D3 and E3 whose frequency has been doubled by the square detection means 45, the normalized square detection correlation signal F2 from which the high frequency component has been removed by the LPF 48. Is four times the frequency of the ultrasonic reception signals D1 and E1. That is, the square wave detection unit 38 further narrows the beam width of the ultrasonic beam, which contributes to further improving the lateral resolution.

Next, the second harmonic extraction unit 39 will be described with reference to FIG.
As shown in FIG. 7A, the second harmonic extraction means 51 extracts the second harmonic component from the ultrasonic reception signals G1 and H1 received by the pair of piezoelectric vibrators 11 and 12.
The ultrasonic signal irradiated from the piezoelectric vibrator 11 irradiates the biological tissue or contrast agent with the ultrasonic signal, and thereby a harmonic signal is induced by the nonlinearity of the biological tissue or contrast agent. Therefore, the ultrasonic signals received by the piezoelectric vibrators 11 and 12 include this induced harmonic.
Here, the fundamental wave of frequency f ₀ the relationship between the ultrasonic wave propagation distance and the center Jikuon field, Figure 7 those to match the maximum sound pressure at harmonics of the fundamental wave and the frequency 2f ₀ of the frequency 2f ₀ (b ). FIG. 7C shows the beam widths of the fundamental wave with the frequency f _0, the fundamental wave with the frequency 2 f ₀ , and the harmonic with the frequency 2 f ₀ .

As shown in FIG. 7B, in the region closer to the surface of the piezoelectric vibrator than the position where the sound pressure maximum value on the central axis is close, the harmonic sound pressure fluctuation of the frequency 2f _{0 is} the fundamental of the frequency f ₀ . it can be seen that much smaller than that of the fundamental wave of waves and frequency 2f _0. Further, in the region far from the position where the sound pressure on the central axis is maximum, the sound pressure attenuation is the largest at the fundamental wave at the frequency 2f ₀ and the smallest at the fundamental wave at the frequency f ₀ . . However, it is close to the attenuation in the case of the attenuation of the harmonic of frequency 2f _{0 and} the fundamental wave of frequency f ₀ .
Further, as shown in FIG. 7 (c), the ultrasonic beam width, greatest fundamental wave of frequency _{f 0} is then harmonic frequency 2f _0, and the fundamental frequency 2f ₀ is the smallest, the frequency 2f ₀ the beam width of the harmonic is approximately 1 / √2 times the fundamental frequency f _0. Further, as long as the side lobe is a fundamental wave, the fundamental wave of the frequency f _{0 and} the fundamental wave of the frequency 2 f ₀ are at the same level, whereas the side lobe level of the harmonic of the frequency 2 f ₀ is the side wave of the fundamental wave. It can be seen that it is much smaller than the level. That is, the second harmonic component extraction means 51 suppresses the side lobe level and contributes to improving the contrast resolution.

  The ultrasonic signals G1 and H1 obtained by applying the drive signal from the pulsar 14 to the piezoelectric vibrator 11 and piezoelectrically converting the ultrasonic waves received by the piezoelectric vibrators 11 and 12 have harmonic components generated by propagating through the living body. Have. The ultrasonic signals G1 and H1 become the harmonic signals G2 and H2 from which the second harmonic component has been extracted by the second harmonic extraction means 51 as described above. Then, the normalization processing means 52 normalizes these harmonic signals G2 and H2, thereby obtaining normalized harmonic signals G3 and H3. Further, the correlation processing means 53 and the LPF 54 provide a normalized harmonic correlation signal I2 with high resolution and high S / N.

The addition processing means 36 is configured to add the normalized correlation signal C2, the normalized square wave correlation signal F2, and the normalized harmonic correlation signal I2 and convert it to a single addition processing signal.
The envelope detector 22 is configured to detect an envelope of the addition processing signal amplified by the logarithmic amplifier 21.
The image converter 24 is configured to convert the addition processing signal converted into a digital signal by the A / D converter 23 into an ultrasonic image signal and display an ultrasonic diagnostic image on the monitor 25.

Next, the reception signal directivity with respect to the distance between the centers of the pair of piezoelectric vibrators 11 and 12 will be described with reference to FIG.
As shown in FIG. 8A, coaxial cables 31 and 32 are connected to the pair of piezoelectric vibrators 11 and 12, respectively, and ultrasonic reception signals J1 and J2 are transmitted. Note that the transmission of ultrasonic waves may be performed using one of the piezoelectric vibrators 11 and 12 or using both piezoelectric vibrators 11 and 12.
Here, when the reception signals of the pair of piezoelectric vibrators 11 and 12 are J1 and J2, respectively, the reception signal directivity in the pair of piezoelectric vibrators 11 and 12 is a signal obtained by adding J1 and J2, that is, J1 + J2. Become. FIG. 8B shows the reception signal directivity with respect to the center distance d between the pair of piezoelectric vibrators 11 and 12. This shows the result of integrating the following expression, which is a directivity function due to separation, into the above-described expression (4).

As shown in FIG. 8B, it can be seen that as the separation distance d increases, the level of the side lobe increases and the side lobe approaches the main lobe. In addition, the beam width of the main lobe is reduced.
When this pair of piezoelectric vibrators 11 and 12 is used for a thin-diameter ultrasonic probe, since the piezoelectric vibrators 11 and 12 are disposed at a thin sheath position, d cannot be increased. Therefore, in the case of the fundamental wave, the nearest side lobe level is between −13 dB and −10 dB, and the nearest side lobe generation angle is 0.15 Rad (8.6 °) ˜0. It will be between 13 Rad (7.5 °).
If there is a phase difference φ between the ultrasonic reception signals received by the pair of piezoelectric vibrators 11 and 12, the directivity Rres is expressed by the following equation. The directivity Rres with respect to this phase difference θ is shown in FIG.

As shown in FIG. 8C, it can be seen that as the phase difference φ increases, the peak is divided, and the lateral resolution decreases.
In FIG. 8A, when the difference between the distances r ₁ and r ₂ from the pair of piezoelectric vibrators 11 and 12 to the point P is large, ultrasonic waves received by the piezoelectric vibrators 11 and 12 are used. The signal phase difference increases and the lateral resolution deteriorates. This gives a phase delay difference to both the received signals J1 and J2, and when the point P is to be observed, as the angle θ between the point P and the center line T increases, the division of the main beam becomes severe. It means that the thing of the point becomes visible as two divided points.
Actually, with respect to the same point, the phase difference increases as the distance d between the pair of piezoelectric vibrators 11 and 12 increases. Therefore, when observing one point using the pair of piezoelectric vibrators 11 and 12, it can be seen that the distance between the pair of piezoelectric vibrators 11 and 12 needs to be as small as possible.

According to the intra-body-cavity ultrasonic diagnostic apparatus configured as described above, the correlation processing means 42 performs correlation processing between the two received signals, thereby removing rf flying noise that has come to the coaxial cable. This can reduce the noise level of the S / N ratio and improve the S / N ratio.
Thereby, even if the sensitivity is increased in order to diagnose the deep part of the body, the logarithmic amplifier 21 or the like enables ultrasonic diagnosis sufficiently useful for diagnosis.

Further, by performing the correlation process, the frequency of the received signal is doubled. This reduces the beam width of the ultrasonic beam and improves the lateral resolution. The noise components can be suppressed by removing the high frequency components generated by the correlation processing means 42, 47, and 53 by the LPFs 43, 48, and 54, respectively.
Further, by doubling the frequency of the received signal by the square detection means 45, the beam width of the ultrasonic beam is reduced, which not only contributes to the improvement of the lateral resolution, but also shortens the pulse width, As a result, the depth resolution can be improved.
Further, by extracting the second harmonic component from the received signal by the second harmonic extraction means 51, the beam width of the ultrasonic beam is reduced, which not only contributes to the improvement of the lateral resolution, but also the pulse width. It is also possible to improve the depth direction resolution. Furthermore, since the side lobe level is suppressed, the contrast resolution can be improved.

In the present embodiment, the square detection means 45 performs an operation of squaring the received signal. However, the present invention is not limited to this, and the ultrasonic received signal is raised to a power of three or more, and its absolute value. It is also possible to perform an operation that takes By doing so, the beam width of the ultrasonic beam is further reduced, and the lateral resolution and depth resolution can be improved.
In addition, the second harmonic extraction unit 51 extracts the second harmonic component from the received signal. However, the second harmonic extraction unit 51 is not limited thereto, and may extract a harmonic component higher than the third harmonic. Good. By doing so, the beam width of the ultrasonic beam is further reduced, the side lobe level can be suppressed, and the contrast resolution can be further improved.

The addition processing unit 36 adds the outputs from the square detection unit 45, the second harmonic extraction unit 51, and the correlation processing unit 42, respectively, but the square detection unit 45 and the second harmonic extraction unit 51 are added. Also, the outputs of the correlation processing means 42 may be weighted and added.
In this way, for example, when performing ultrasonic observation with priority given to contrast resolution, the output from the second harmonic extraction means 51 is weighted more than the output from the correlation processing means 42 and the square detection means 45. By increasing the value, it is possible to perform a diagnosis in which the contrast resolution is prioritized.
The weighting coefficient can be set to a desired weighting from a control device (not shown) such as a computer.

Further, as shown in FIG. 9, the received signal processing means 15 has a frequency doubler 72 having a pair of frequency doublers (frequency multipliers) 71 that respectively double the frequency of the received signal. Also good.
The frequency doubling unit 72 normalizes the pair of frequency doubling means 71 for doubling the frequency of the ultrasonic signals of the pair of piezoelectric vibrators 11 and 12 and the ultrasonic reception signal obtained by doubling the frequency, respectively. A pair of normalization processing means 73 for processing, a correlation processing means 74 for correlation processing of two ultrasonic reception signals, and an LPF 75 are provided.

Here, the frequency doubler 71 converts the input signal into a digital signal by AD conversion, performs double conversion to double the frequency without changing the signal level, and returns to the time axis pulse signal by Fourier conversion. Is.
Further, arrows K1 and L1 indicate ultrasonic reception signals from the pair of piezoelectric vibrators 11 and 12, arrows K2 and L2 indicate frequency doubled signals by the frequency doubler 71, and arrows K3 and L3 indicate normalization processor 73. The normalized frequency doubled signal, the arrow M1 indicates the normalized frequency doubled correlation signal by the correlation processing means 74, and the arrow M2 indicates the normalized doubled correlation signal from which high-frequency components have been removed by the LPF 75.

Thus, by using the frequency doubling means 71, the frequency of the received signal can be doubled and the pulse width can be reduced.
It should be noted that the frequency is not limited to double and may be triple or higher. By doing so, the pulse width can be further reduced.

Next, a second embodiment according to the present invention will be described with reference to FIG. In the following description, the same reference numerals are given to the components described in the above embodiment, and the description thereof is omitted.
The difference between the second embodiment and the first embodiment is that the intracorporeal ultrasound diagnostic apparatus in the first embodiment is applied to a small-diameter ultrasonic probe, and the ultrasonic transducer is rectangular. The pair of piezoelectric vibrators 11 and 12 that are plates are arranged side by side in parallel. However, in the intracorporeal ultrasound diagnostic apparatus according to the second embodiment, the ultrasonic transducer 100 includes the ring-shaped vibrator 101 and the ring-shaped vibrator. The disk-shaped vibrator 102 is arranged at the inner diameter portion of the vibrator 101.

  As shown in FIG. 10, the intracorporeal ultrasound diagnostic apparatus includes a ring-shaped transducer 101, a disk-shaped transducer 102, a pulser 14 that applies an ultrasonic transmission drive voltage to the ring-shaped transducer 101, a ring Reception signal processing means 103 for processing ultrasonic signals received by the cylindrical vibrator 101 and the disk-like vibrator 102, a logarithmic amplifier 21, an envelope detector 22, an A / D converter 23, and an image converter 24 and a monitor 25.

The ring-shaped vibrator 101 is configured to transmit a fundamental ultrasonic wave by an ultrasonic transmission drive voltage from the pulser 14. And it is connected to the received signal processing means 103 via the coaxial cable 31.
The disc-like vibrator 102 has a thickness approximately half that of the ring-like vibrator 101, and is configured to receive the second harmonic. Then, it is connected to the reception signal processing means 103 via the coaxial cable 32.
The ring-shaped vibrator 101 and the disk-shaped vibrator 102 each have a mechanical quality factor Qm of 30 or more and 300 or less.

  The reception signal processing means 103 is a square detection means 111 that squarely detects the ultrasonic reception signal of the ring-shaped vibrator 101, and a second harmonic that is extracted from the ultrasonic reception signal of the disk-shaped vibrator 102. A harmonic extraction means 112, a pair of normalization processing means 113 for normalizing each ultrasonic reception signal, a correlation processing means 114 for correlating two ultrasonic reception signals, and an LPF 115 are provided.

  The pulser 14 applies a drive signal that transmits a trapezoidal waveform to the ring-shaped vibrator 101. In this trapezoidal waveform, when the piezoelectric response signal for the voltage rise of the ring-shaped vibrator 101 and the piezoelectric response signal for the voltage effect overlap, by setting the width of the trapezoid so as to cancel out, leaving several waves, Only the pulse width can be suppressed without changing the maximum amplitude.

  According to the intra-body-cavity ultrasonic diagnostic apparatus configured as described above, the correlation processing unit 114 converts the ultrasonic signals received by the ring-shaped transducer 101 and the disc-shaped transducer 102 as in the first embodiment described above. By performing the correlation process in step 1, the noise component flying on the coaxial cable can be removed. Thereby, the noise level of S / N ratio can be made small and S / N ratio can be improved. Therefore, even if the sensitivity is increased for diagnosing the deep part of the body, sufficiently useful ultrasonic diagnosis is possible.

In addition, since the mechanical quality factor Qm of the ring-shaped vibrator 101 and the disk-shaped vibrator 102 is 30 or more and 300 or less, it is possible to suppress unnecessary vibration noise from being superimposed on the ultrasonic reception signal.
Further, since the pulser 14 applies a driving signal for transmitting a trapezoidal waveform from the ring-shaped vibrator 101, the piezoelectric response signal when the voltage of the ring-shaped vibrator 101 rises overlaps with the piezoelectric response signal when the voltage drops. Sometimes, by setting the trapezoidal width so as to cancel each other leaving several waves, it is possible to suppress the degradation in the depth direction resolution due to an increase in the reverberation time of the pulse signal.

In the present embodiment, as shown in FIG. 11, the processing unit 116 may be configured such that the ring-shaped vibrator 101 is connected to the normalization processing unit 113 via the second harmonic extraction unit 117. Even in this case, as described above, the beam width of the ultrasonic beam can be reduced to improve the lateral resolution, and the pulse width can be shortened to improve the depth resolution.
Further, although the pulser 14 is configured to transmit a trapezoidal waveform from the ring-shaped vibrator 101, the pulser 14 is not limited to the trapezoidal waveform but may be a double rectangular wave. At this time, when the piezoelectric response of the first rectangular wave of the ring-shaped vibrator 101 overlaps, the interval between the two rectangular pulses is set so as to cancel out by leaving several waves, so that the maximum amplitude is not changed. Only the pulse width can be suppressed.

Further, the ratio of the resonance frequencies of the ring-shaped vibrator 101 and the disk-shaped vibrator 102 is 1: 2, but may be 1: 3 or 1: 4. By doing so, the disc-like vibrator 102 receives the third harmonic or the fourth harmonic of the ultrasonic wave oscillated from the ring-like vibrator 101, so that the resolution in the depth direction is further improved. Here, when the disc-like vibrator 102 receives the third harmonic, the ring-like vibrator 101 is a cube detecting means for calculating the absolute value of the received signal to the third power or the third harmonic component. When the disc-like vibrator 102 receives the fourth harmonic wave, the fourth harmonic wave detection means for raising the received signal to the fourth power or the fourth harmonic component is extracted. Connected to 4th harmonic extraction means.
However, the ratio of the resonance frequencies of the ring-shaped vibrator 101 and the disk-shaped vibrator 102 is 1: 5 or more, that is, the resonance frequency of the disk-shaped vibrator 102 is five times the resonance frequency of the ring-shaped vibrator 101. If it is above, the harmonics higher than the fifth harmonic are smaller than the fundamental wave of the ultrasonic signal by 50 dB or more, and it is difficult to amplify while maintaining a high S / N ratio.

Next, an intracorporeal ultrasound diagnostic apparatus according to a third embodiment of the present invention will be described with reference to FIGS. In the following description, the same reference numerals are given to the components described in the above embodiment, and the description thereof is omitted.
The difference between the third embodiment and the first embodiment is that the intracorporeal ultrasound diagnostic apparatus according to the first embodiment is an ultrasound probe, whereas the intracavity ultrasound according to the third embodiment. The diagnostic device is an intracorporeal ultrasound scope using an electronic scanning array type transducer.

  As shown in FIG. 12, the intracorporeal ultrasound diagnostic apparatus includes an ultrasonic transducer 202 including N piezoelectric vibrators 201, and a pulser unit 211 that applies a driving voltage for ultrasonic transmission to the piezoelectric vibrators 201. , Reception signal processing means 212 for processing ultrasonic signals received by n piezoelectric vibrators out of N piezoelectric vibrators 201, and Doppler shift amount from the ultrasonic reception signals received by n piezoelectric vibrators 201 A Doppler shift amount analysis unit (Doppler diagnostic means) 213, a logarithmic amplifier 21, an envelope detector 22, an A / D converter 25, an image converter 24, and a monitor 25.

  As shown in FIG. 13, the N piezoelectric vibrators 201 are arranged on a circumference around the axis of the insertion axis, and are sealed together with the acoustic coupling liquid 214a in the balloon 214 so as to prevent bubbles from entering. It is fixed with the tool 214b. The piezoelectric transducer 201 is connected to an electronic switch circuit 216 that switches between transmission and reception of ultrasonic waves via a coaxial cable bundle 215 constituted by N coaxial cables.

The pulsar means 211 is configured to apply an ultrasonic transmission drive voltage to m piezoelectric vibrators adjacent to each other among the N piezoelectric vibrators 201. The pulsar means 211 drives m number of piezoelectric vibrators 201 via a waveform generator 221 and m number of transmission delay circuits 222 that make the waveform of the ultrasonic signal to be transmitted a predetermined shape. Circuit 223.
The m drive circuits 223 are connected to the m piezoelectric vibrators for transmission via the electronic switch circuit 216.
The electronic switch circuit 216 is configured to select the m piezoelectric vibrators 11 that transmit ultrasonic waves from the N piezoelectric vibrators 201, and performs linear scanning from the selected m piezoelectric vibrators 201. However, it is configured to perform multi-beam convergence, sector scanning, or both.

  The reception signal processing means 212 includes n reception delay circuits 231 that adjust the delay of the ultrasonic reception signals from the n adjacent piezoelectric transducers 201 selected by the electronic switch circuit 216, and 2 adjacent to each other. A processing means 232 for processing an ultrasonic reception signal from each piezoelectric vibrator 201, a memory 233 for temporarily recording the ultrasonic reception signal, and an ultrasonic reception signal recorded in the memory 233 as a single signal Addition processing means 234 for converting to.

The processing means 232 includes an electronic switch circuit 241 and n precorrelators 242.
The electronic switch circuit 241 pre-correlates a set of ultrasonic reception signals from two adjacent piezoelectric vibrators 201 among the ultrasonic reception signals of the n piezoelectric vibrators 201 that are reception piezoelectric vibrators. It is configured to input to the device 242.
As shown in FIG. 14, the pre-correlator 242 includes second harmonic extraction means 251 that extracts the second harmonic from the ultrasonic reception signal of the reception delay circuit 231 by the electronic switch circuit 241, and normalization means 252. And a correlation processing means 253. The pre-correlator 242 outputs a signal with improved lateral resolution and noise removed to the memory 233.

  The ultrasonic reception signal converted into a single signal by the addition processing means 234 is amplified by the logarithmic amplifier 21 and passes through the envelope detector 22, the A / D converter 23 and the image converter 24 in the same manner as described above. It is displayed on the monitor 25.

  The Doppler shift amount analysis unit 213 includes a local oscillator 261 that transmits a reference signal, a Cos converter 262 that orthogonally converts the reference signal from the local transmitter 261, and an ultrasonic reception signal and a Cos converter 262 from the addition processing unit 234. A mixer 264 that mixes the reference signal orthogonally transformed by the signal, an LPF 265 that removes high-frequency components of the mixed ultrasonic reception signal, an A / D converter 266 that converts the ultrasonic reception signal into a digital signal, and A / And a spectrum analyzer 267 for analyzing the Doppler shift amount from the output of the D converter 266.

The mixer 263 is configured to output a difference signal and a sum signal between the ultrasonic reception signal and the reference signal by mixing the ultrasonic reception signal and the reference signal. Further, the mixer 264 is configured to output a difference signal and a sum signal between the ultrasonic reception signal and the orthogonally converted reference signal. The LPF 265 is configured to output a difference signal by removing each sum signal, which is a high-frequency component, from the outputs of the mixers 263 and 264.
The spectrum analyzer 267 is configured to calculate a Doppler shift amount by performing quadrature detection between two difference signals and converting it to frequency characteristics. The output of the spectrum analyzer 267 is connected to the image converter 24 and a Doppler image is superimposed on the monitor 25 and displayed.

  As shown in FIG. 7B, the fundamental wave has a sound pressure fluctuation at a short distance from the center, and the radius of the balloon 214 is the focal point of the fundamental wave field where the sound pressure level of the fundamental wave is maximized. If it is further away, this sound pressure fluctuation region is in the vicinity of the balloon 214, and artifacts due to multiple reflection occur. On the other hand, the harmonic has a smaller sound pressure level, although the maximum value of the sound pressure level is smaller than that of the fundamental wave, and the attenuation is similar to that of the fundamental wave.

  The intra-body-cavity ultrasonic diagnostic apparatus configured as described above has the same operations and effects as those of the first embodiment described above. However, by using the harmonic component of the ultrasonic reception signal, multiplexing by the balloon 214 is performed. The occurrence of reflection can be suppressed.

In this embodiment, the pre-correlator 242 includes a square detection unit 271 that square-detects the ultrasonic reception signal of the reception delay circuit 231 and a normalization unit 272, as shown in FIG. And correlation processing means 273. Further, as shown in FIG. 15 (b), it comprises a cube detection means 275 that calculates the absolute value of the ultrasonic reception signal to the third power, a normalization means 276, and a correlation processing means 277. Also good. Further, as shown in FIG. 15C, a frequency doubler 281 that doubles the frequency of the ultrasonic reception signal, a normalization processing unit 282, and a correlation processing unit 283 may be included. Further, as shown in FIG. 15 (d), third harmonic extraction means 285, normalization processing means 286, and correlation processing means 287 may be included.
In either case, the same effects as those described in the first embodiment can be obtained.

  In addition, the addition processing means 234 can use a function of weighting n ultrasonic reception signals in the same manner as in the first embodiment described above. For example, a Gaussian distribution weighting for reducing the grating, And cosine distribution weighting.

Next, an intracorporeal ultrasound diagnostic apparatus according to the fourth embodiment of the present invention will be described with reference to FIG. In the following description, the same reference numerals are given to the components described in the above embodiment, and the description thereof is omitted.
The difference between the fourth embodiment and the third embodiment is that, in the intracorporeal ultrasound diagnostic apparatus according to the fourth embodiment, the Doppler shift amount analysis unit 301 analyzes the Doppler shift amount using the harmonic Doppler signal. It is a point to do.

That is, as shown in FIG. 16, the intracorporeal ultrasound diagnostic apparatus according to the fourth embodiment generates a harmonic Doppler signal, so that a BPF 302 for extracting harmonic components is connected to the output side of the addition processing means 234. Has been.
In addition, the Doppler shift amount analysis unit 301 includes a local oscillator 311 that transmits a reference signal having an oscillation frequency near the harmonic signal of the ultrasonic reception signal received by the piezoelectric vibrator 201. The Doppler shift amount analysis unit 301 also branches from the Cos converter 312 that orthogonally transforms the reference signal from the local oscillator 311, the mixer 313 that mixes the ultrasonic reception signal branched from the BPF 302 and the reference signal, and the BPF 302. A mixer 314 that mixes the ultrasonic reception signal and the reference signal orthogonally transformed by the Cos converter 312, an LPF 315 that removes high-frequency components of the mixed ultrasonic reception signal, and A that converts the ultrasonic reception signal into a digital signal A / D converter 316 and a spectrum analyzer 317 for analyzing the Doppler shift amount from the output of the A / D converter 316 are provided.

  According to the intracorporeal ultrasound diagnostic apparatus configured as described above, the same function and effect as the intracorporeal ultrasound diagnostic apparatus in the third embodiment described above are obtained, but the oscillation frequency of the local oscillator 311 is a harmonic signal. Therefore, a harmonic Doppler can be realized.

Also in this embodiment, the configuration as shown in FIG. 15 may be used for the precorrelator 242 as in the third embodiment described above.
In this embodiment, the ultrasonic wave reception signal received by the piezoelectric vibrator 201 may be processed as a digital signal by appropriately performing A / D conversion. By doing so, however, the reference signal oscillated by the local oscillator 311 is an analog signal, and the mixers 313 and 314 mix with the analog signal. Therefore, when the output of the BPF 302 is a digital signal, A D / A converter is provided between the mixers 313 and 314 to convert a digital signal into an analog signal.

Next, an intracorporeal ultrasound diagnostic apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. In the following description, the same reference numerals are given to the components described in the above embodiment, and the description thereof is omitted.
The difference between the fifth embodiment and the third embodiment is that in the intracorporeal ultrasound diagnostic apparatus according to the fifth embodiment, the ultrasonic propagation time from the N piezoelectric vibrators 201 is between each piezoelectric vibrator. In other words, a phase matching unit 351 is provided for matching variations in phase, i.e., phase variations.

  That is, as shown in FIG. 17, the intracorporeal ultrasound diagnostic apparatus according to the fifth embodiment performs reception signal processing for processing ultrasonic signals received by n piezoelectric transducers out of N piezoelectric transducers 201. Means 352 and a phase matching unit 351 that is connected to the output terminal of the reception signal processing means 352 and that matches the phase variation of the ultrasonic reception signals received by the n piezoelectric vibrators 201 are provided.

  The phase matching unit 351 includes a timing controller 361 that transmits a common reference signal for all ultrasonic beams, and n quadrature detections that quadrature-detect the output of a pre-correlator 392 described later from a reference signal of the timing controller 361. Means 362, two wavefront memories (complex data storage means) 363 and 364 for recording the wavefront data of the real signal component and the imaginary signal component from the orthogonal detection means 362, and a wavefront locus lookup table (complex data reading means, Hereinafter, abbreviated as wavefront local LUT) 365, real component phase correction memory 367 and imaginary component level complementary memory 368, real component phase correction memory (complex data reading means) 367 and imaginary component level complementary memory (complex data). Readout means) From the phase correction information recorded in 368, the wavefront memory 363, And a phase correction circuit (phase correction processing means) 369 for correcting the phase of the wavefront data recorded in the 64.

The timing controller 361 is configured to transmit a reference signal, which is a reference signal common to all ultrasonic beams, to the waveform generator 221 and the n orthogonal detection units 362 in order to match the phase variation. ing.
The quadrature detection means 362 mixes the ultrasonic reception signal branched from the pre-correlator 392 and the reference signal from the timing controller 361, the ultrasonic reception signal branched from the pre-correlator 392, and cos. A multiplier 383 that mixes the reference signal orthogonally transformed by the converter 382 and a pair of LPFs 384 that remove harmonic components of the mixed ultrasonic reception signal are provided.

The wavefront memories 363 and 364 are configured to record complex wavefront data composed of real signal components and imaginary signal components from the n orthogonal detectors 362, respectively.
The wavefront locus LUT 365 corrects the phase of wavefront data recorded in the wavefront memories 363 and 364 along the wavefront locus having a positional relationship such that the point to be imaged is a focal point based on the address information recorded therein. It is configured to output to the circuit 369.
The phase correction circuit 369 refers to the phase correction information of the real component and the imaginary component recorded in the real component phase correction memory 367 and the imaginary component phase correction memory 368 and adjusts the focus of each piezoelectric vibrator so as to be in the same phase. Complementation is performed in consideration of the delay time determined by the acoustic distance, and the composition processing is performed by taking the sum of squares of each corrected complex data. This synthesis process is performed over a two-dimensional area so as to cover a tomographic area that is an area to be displayed in the ultrasonic scanning area by the piezoelectric vibrator 201.

The reception signal processing means 352 includes n reception delay circuits 231 and processing means 390 for processing ultrasonic reception signals from two piezoelectric vibrators 201 adjacent to each other.
The processing unit 390 is connected to the electronic switch 241 and the output terminal of the electronic switch 241, and n A / D converters 391 that A / D convert ultrasonic reception signals received by the n piezoelectric vibrators 201. And a pre-correlator 392 that receives as input a set of ultrasonic reception signals from two adjacent piezoelectric vibrators 201 from the outputs of the n A / D converters 391.

The pre-correlator 392 has the same configuration as the pre-correlator 242 in the third embodiment described above. However, the precorrelator 242 in the third embodiment performs correlation processing on the analog signal, whereas the precorrelator 392 in the fifth embodiment performs correlation processing on the digital signal. It is the composition which performs.
The ultrasonic reception signal subjected to correlation processing by the pre-correlator 392 is output to the quadrature detection means 362.

  According to the intra-body-cavity ultrasonic diagnostic apparatus configured as described above, among the echo signals obtained by the piezoelectric vibrator 201, reception signals from a plurality of adjacent piezoelectric vibrators are correlated with each other, and the correlation output is obtained. Is converted into a real component signal and an imaginary component signal by quadrature detection by the quadrature detection means 362, and corresponds to a delay time determined by a spatial arrangement or the like with respect to the focal position of each piezoelectric vibrator 201 with respect to the wavefront data. By performing the beam synthesis process with phase rotation process, which is the phase matching process, an ultrasonic tomographic image (B-mode image) in which unnecessary beam components represented by side lobes are further suppressed by the beam characteristics at the time of synthesis Can be obtained.

Next, a sixth embodiment will be described with reference to FIG. In the following description, the same reference numerals are given to the components described in the above embodiment, and the description thereof is omitted.
The difference between the sixth embodiment and the third embodiment is that in the intracorporeal ultrasound diagnostic apparatus according to the third embodiment, the reception signal processing means 212 is different from the ultrasonic reception signal by two adjacent piezoelectric vibrators 201. Whereas the correlation process is performed, the intracorporeal ultrasound diagnostic apparatus according to the sixth embodiment includes reception signal processing means 401 corresponding to the ultrasonic reception signals from three adjacent piezoelectric transducers. It is a point.

  That is, as shown in FIG. 18A, the intracorporeal ultrasound diagnostic apparatus according to the sixth embodiment includes the ultrasonic signals received by the n piezoelectric vibrators among the N piezoelectric vibrators 201. A reception signal processing unit 401 is provided for processing ultrasonic reception signals from three adjacent piezoelectric vibrators.

The reception signal processing unit 401 includes n reception delay circuits 231, a processing unit 410, a memory 233, and an addition processing unit 234 that converts the ultrasonic reception signal recorded in the memory 233 into a single signal. I have.
The processing means 410 includes an electronic switch circuit 412 and n pre-correlators 413.
The electronic switch circuit 412 is a pre-correlator with a set of ultrasonic reception signals from three adjacent piezoelectric transducers among the ultrasonic signals received by n piezoelectric transducers that are reception piezoelectric transducers. 413 is input.

As shown in FIG. 18B, the pre-correlator 413 performs RF signal 414 and square detection means 415 for performing signal processing on each of the received ultrasonic reception signals from the three piezoelectric vibrators. And second harmonic extraction means 416 and addition processing means 417 for adding the ultrasonic reception signals that have passed through them.
The RF means 414 has a function of passing the inputted ultrasonic reception signal as it is.
The three ultrasonic reception signals that have passed through the RF unit 414, the square wave detection unit 415, and the second harmonic extraction unit 416 are respectively converted into an A / D converter 418, a logarithmic amplifier 419, an envelope detector 420, and a normalization process. Via the means 421, the addition processing means 417 is configured to perform addition processing.

  According to the intra-body-cavity ultrasonic diagnostic apparatus configured as described above, an ultrasonic diagnostic image with a good S / N ratio and excellent spatial resolution can be obtained as described above.

In the present embodiment, the pre-correlator 413 does not perform correlation processing between the ultrasonic reception signals of each channel, but is configured to sequentially perform correlation processing on three adjacent ultrasonic reception signals. Another precorrelator 451 may be used.
As shown in FIG. 19, the pre-correlator 451 includes an RF reception unit 414, a square detection unit 415, a second harmonic extraction unit 416, and an ultrasonic reception signal that has passed through the square detection unit 415. Correlation processing 452 that performs correlation processing of the ultrasonic reception signal that has passed through the second harmonic extraction means 416, and correlation processing between the ultrasonic reception signal that has passed through the RF means 414 and the ultrasonic reception signal that has passed through the correlation processing means 452. Correlation processing means 453 for performing the processing.
Buffers 454 and 455 are provided before the correlation processing unit 453 so that a crosstalk phenomenon does not occur between the correlation processing unit 452 and the correlation processing unit 453.
Even when the pre-correlator 451 configured in this way is used, an ultrasonic diagnostic image having a good S / N ratio and excellent spatial resolution can be obtained as described above.

In the present embodiment, the electronic scanning type intracorporeal ultrasonic diagnostic apparatus in which the piezoelectric vibrators are arranged on the circumference is used. However, the present invention is not limited to this, and the mechanical radial scanning type intracorporeal ultrasonic diagnostic apparatus is used. You may apply to.
Further, the addition processing means 234 can use a function of weighting n ultrasonic reception signals, as in the third embodiment described above.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the present invention is applied to an intracorporeal ultrasonic diagnostic apparatus, but may be applied to an external ultrasonic diagnostic apparatus.
In the third to sixth embodiments, the N piezoelectric vibrators 201 are arranged on the circumference, but the present invention is not limited to this, and may be arranged in an array. In the fourth embodiment, the Doppler shift amount analysis unit 213 analyzes the Doppler shift amount using the two reference signals orthogonal to each other by the spectrum analyzer 267. However, the Doppler shift amount analysis unit 213 uses only one of the reference signals. The shift amount may be analyzed.

1 is a functional block diagram illustrating an intracorporeal ultrasound diagnostic apparatus according to a first embodiment of the present invention. It is a functional block diagram for demonstrating the correlation process part in the 1st Embodiment of this invention. It is a graph which shows the ultrasonic reception signal and normalized correlation processing signal in the 1st Embodiment of this invention. It is for demonstrating the directivity of the piezoelectric vibrator in the 1st Embodiment of this invention, (a) is a functional block diagram, (b) is a perspective view of a piezoelectric vibrator, (c) is an ultrasonic frequency. It is a graph which shows the directivity of the piezoelectric vibrator with respect to. It is a graph which shows the intensity | strength with respect to the time of the ultrasonic pulse of the piezoelectric vibrator in the 1st Embodiment of this invention. It is a functional block diagram for demonstrating the square detection part in the 1st Embodiment of this invention. It is for demonstrating the 2nd harmonic extraction part in the 1st Embodiment of this invention, (a) is a functional block diagram, (b) is a graph which shows the sound pressure level with respect to the depth of each fundamental wave and a harmonic. (C) is a graph which shows the directivity of each fundamental wave and a harmonic. (A) is an explanatory diagram, (b) is a graph showing directivity with respect to a distance, and (c) is directivity with respect to a phase difference. It is a graph which shows. It is a functional block diagram for demonstrating the frequency multiplication part in the 1st Embodiment of this invention. 1 shows an intracorporeal ultrasound diagnostic apparatus according to a second embodiment of the present invention, in which (a) is a plan view of an ultrasonic transducer and (b) is a functional block diagram. It is a functional block diagram of the other form of the 2nd Embodiment of this invention. It is a functional block diagram which shows the intracorporeal ultrasound diagnostic apparatus in the 3rd Embodiment of this invention. It is the schematic which shows the ultrasonic transducer in the 3rd Embodiment of this invention. It is a functional block diagram which shows the pre-correlator in the 3rd Embodiment of this invention. It is a functional block diagram which shows the other form of the pre-correlator in the 3rd Embodiment of this invention. It is a functional block diagram which shows the intraluminal ultrasonic diagnostic apparatus in the 4th Embodiment of this invention. It is a functional block diagram which shows the intraluminal ultrasonic diagnostic apparatus in the 5th Embodiment of this invention. In the 6th Embodiment of this invention, (a) is a functional block diagram which shows an intracorporeal ultrasound diagnostic apparatus, (b) is a functional block diagram which shows a pre-correlator. It is a functional block diagram which shows the other form of the pre-correlator in the 6th Embodiment of this invention. It is the schematic which shows the scanning method of the conventional array type ultrasonic transducer | vibrator.

Explanation of symbols

11, 12, 201 Piezoelectric vibrator (vibrator element)
13, 100, 202 Ultrasonic transducer 14, 211 Pulsar means 15, 103, 116, 212, 352, 401 Received signal processing means 23, 25, 266, 316, 391, 418 A / D converter 25 Monitor (display means)
36, 234 Addition processing means 42, 47, 53, 74, 114, 253, 273, 277, 283, 287, 452, 453 Correlation processing means 43, 48, 54, 75, 115, 384 Low pass filter (filter means)
45, 111, 271, 415 Square power detection means (power detection means)
51, 112, 251, 416 Second harmonic extraction means (harmonic extraction means)
71, 281 Frequency multiplying means 101 Ring-shaped vibrator 102 Disk-shaped vibrator 213, 301 Doppler shift amount analysis unit (Doppler diagnostic means)
275 Third power detection means (power detection means)
285 Third harmonic extraction means (harmonic extraction means)
362 Quadrature detection means 363, 364 Wavefront memory (complex data storage means)
365 Wavefront locus lookup table (complex data reading means)
367 Real component phase correction memory (complex data reading means)
368 Imaginary component complementary memory (complex data reading means)
369 Phase correction circuit (phase correction processing means)

Claims (18)

An ultrasonic transducer comprising N (N ≧ 2) transducer elements, pulsar means for applying a voltage to the m transducer elements (m ≦ N) and transmitting ultrasonic waves, and n (n ≦ n) N) a reception signal processing means for performing signal processing using the ultrasonic reception signal received by the transducer element, and a display device for displaying an ultrasonic diagnostic image,
The ultrasonic diagnostic apparatus, wherein the reception signal processing means multiplies the frequency of an ultrasonic reception signal received by the n transducer elements.   The reception signal processing means includes correlation processing means for performing correlation processing between ultrasonic reception signals received by two or more different transducer elements among the n transducer elements. The ultrasonic diagnostic apparatus according to claim 1.   The received signal processing means is a power detection means for calculating an absolute value by raising an ultrasonic reception signal received by one of the n transducer elements, and an ultrasonic reception signal. The ultrasonic diagnostic apparatus according to claim 1, comprising at least one of a harmonic extraction unit that extracts a harmonic component and a frequency multiplication unit that multiplies the frequency of the ultrasonic reception signal. .   The ultrasonic diagnostic apparatus according to claim 2, wherein the signal processing unit includes a filter unit that removes a high frequency generated by the correlation processing unit. The signal processing means includes an addition processing means for adding an ultrasonic reception signal received by the n transducer elements;
The ultrasonic diagnostic apparatus according to any one of claims 1 to 4, wherein the addition processing means weights and adds the ultrasonic reception signal.   The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic transducer is a small-diameter ultrasonic transducer including two transducer elements. The ultrasonic transducer is composed of a ring-shaped vibrator and a disk-shaped vibrator disposed on the inner diameter portion thereof,
6. The pulser means applies a voltage to the ring-shaped vibrator to transmit an ultrasonic wave, and receives the ring-shaped piezoelectric vibrator and the disk-shaped vibrator. The ultrasonic diagnostic apparatus of any one of Claims.   The ultrasonic diagnostic apparatus according to claim 7, wherein a ratio of resonance frequencies of the ring-shaped vibrator and the disk-shaped vibrator is 1: k (k ≧ 2).   The ultrasonic diagnostic apparatus according to claim 2, wherein the correlation processing unit performs a correlation process on the ultrasonic reception signals of the two transducer elements adjacent to each other.   The ultrasonic diagnostic apparatus according to any one of claims 1 to 5, wherein the ultrasonic transducer has the N transducer elements arranged in an array.   The ultrasonic diagnostic apparatus according to any one of claims 1 to 9, wherein a mechanical quality factor Qm of the ultrasonic transducer is 30 or more and 300 or less.   The ultrasonic diagnostic apparatus according to any one of claims 1 to 11, wherein the pulser means applies a trapezoidal waveform or a double rectangular wave as a drive signal to the m transducer elements.   The ultrasonic diagnostic apparatus according to claim 10, further comprising a Doppler diagnostic unit that displays a Doppler diagnostic image on the display unit.   The ultrasonic diagnostic apparatus according to claim 10, further comprising: a harmonic signal Doppler diagnostic unit that displays a harmonic Doppler diagnostic image on the display unit.   15. The reception signal processing unit according to claim 1, further comprising an A / D converter that performs analog / digital conversion on an ultrasonic reception signal received by the n transducer elements. The ultrasonic diagnostic apparatus as described.   The ultrasonic diagnostic apparatus according to claim 15, wherein the reception signal processing means is capable of signal processing the ultrasonic reception signal converted by the A / D converter.   Orthogonal detection means for converting the ultrasonic reception signal processed by the reception signal processing means into reception complex data, complex data storage means for storing the reception complex data, and the n transducers by the complex data storage means Complex data reading means for reading out complex data at an approximate position determined by the positional relationship between the element and the focus, and positions of the n transducer elements and the focus with respect to the complex data obtained by the complex data reading means The ultrasonic wave according to any one of claims 1 to 16, further comprising phase correction processing means for performing phase correction processing of the reception complex data corresponding to an accurate delay time determined by a relationship. Diagnostic device. The ultrasonic diagnostic apparatus according to claim 1, wherein the ultrasonic diagnostic apparatus is an intracorporeal ultrasonic diagnostic apparatus used for ultrasonic diagnosis in a body cavity.

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