JP5325617B2 - Ultrasonic probe and ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of signal lines for connecting an ultrasonic probe and an ultrasonograph body or to perform wireless communication by reducing a volume of data of reception signals outputted by a plurality of ultrasonic transducers. <P>SOLUTION: The ultrasonic probe includes: a plurality of ultrasonic transducers for receiving ultrasonic echoes to output reception signals; a signal processing means for performing orthogonal detection processing or orthogonal sampling processing on the reception signals outputted by the respective ultrasonic transducers to generate a complex baseband signal and generate an amplitude signal representing an amplitude of the complex baseband signal and a phase signal representing a phase of the complex baseband signal; a sampling means for sampling the amplitude signal and the phase signal to generate sample data; a serializing means for converting the parallel sample data into serial sample data; and a transmitting means for transmitting the serial sample data. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an ultrasonic probe that includes a plurality of ultrasonic transducers that transmit and receive ultrasonic waves, and an ultrasonic diagnostic apparatus that generates an ultrasonic diagnostic image using such an ultrasonic probe.

  In the medical field, various imaging techniques have been developed in order to observe and diagnose the inside of a subject. In particular, ultrasonic imaging that acquires internal information of a subject by transmitting and receiving ultrasonic waves enables real-time image observation, and other medical uses such as X-ray photographs and RI (radio isotope) scintillation cameras. Unlike imaging technology, there is no radiation exposure. Therefore, ultrasonic imaging is used as a highly safe imaging technique in a wide range of areas including gynecological system, circulatory system, digestive system, etc. in addition to fetal diagnosis in the obstetrics field.

  The principle of ultrasonic imaging is as follows. Ultrasound is reflected at the boundary between regions having different acoustic impedances, such as the boundary between structures in the subject. Therefore, an ultrasonic beam is transmitted into a subject such as a human body, an ultrasonic echo generated in the subject is received, and a reflection position and a reflection intensity at which the ultrasonic echo is generated are obtained. The contour of an existing structure (for example, a viscera or a diseased tissue) can be extracted.

  In general, in an ultrasonic diagnostic apparatus, an ultrasonic probe including a plurality of ultrasonic transducers (vibrators) having an ultrasonic transmission / reception function is used. The reception signal output from the transducer that has received the ultrasonic echo is accompanied by a delay according to the difference in distance from the focal point of the ultrasonic to each transducer. A beam forming process (reception focus process) for focusing on a specific position is performed by adding the received signals after giving them to the signal. At that time, the received signals are treated as parallel data until a plurality of received signals are added.

  This reception focus processing is usually performed by digital signal processing. In other words, the A / D converted received signal is stored in the memory, then read out while changing the reading time as needed, appropriately interpolated, and added. When a plurality of received signals are added, the number of signal channels becomes one, so that signal transmission can also be performed by wireless communication. Therefore, if a circuit for performing the reception focus processing is incorporated in the ultrasonic probe, the number of signal lines connecting the ultrasonic probe and the ultrasonic diagnostic apparatus main body can be reduced or wireless can be achieved.

  However, in the reception focus processing, the amount of delay given to the reception signal differs depending on the position of the focal point. Therefore, the control of the read time from the memory becomes extremely complicated, and a large-scale circuit is required. When such a circuit is incorporated into an ultrasonic probe, it is no longer practical enough to be easily operated with one hand.

  As a related technique, Japanese Patent Application Laid-Open No. H10-228867 discloses that a transmission cable can be reduced in diameter and weight even when the number of vibration elements increases with higher definition, and the operability can be maintained and improved. An ultrasonic diagnostic apparatus having an acoustic probe is disclosed. This ultrasonic diagnostic apparatus includes an ultrasonic probe that transmits and receives ultrasonic pulses to and from a living body using a plurality of vibration elements, and an ultrasonic probe connected to the ultrasonic probe via a transmission cable. Generation of a transmission signal for transmitting an ultrasonic pulse from a touch element and formation of an ultrasonic image from the received signal based on an ultrasonic pulse (echo) reflected by a living body and received by an ultrasonic probe The transmission signal and reception signal passed between the ultrasound probe and the device body via the transmission cable are separated in a time-sharing manner corresponding to each vibration element before transmission. Each chip is sequentially transmitted using a shared signal line in the transmission cable.

  However, in the ultrasonic diagnostic apparatus disclosed in Patent Document 1, since the received signal output from each vibration element is transmitted in the same band, the amount of data cannot be reduced and a high transmission rate is required. . In addition, since the received signal is transmitted by time division, there is no guarantee that the beam forming process can be reliably performed after transmission.

  Patent Document 2 discloses a wireless ultrasonic diagnostic apparatus that performs wireless transmission between an ultrasonic probe and an apparatus main body. In this ultrasonic diagnostic apparatus, the ultrasonic probe includes a plurality of transducers, an amplifier and an A / D converter corresponding to the transducers, a digital beam former, a PS conversion unit, a control data insertion unit, , Including a modulator and a power amplifier, digital beam forming processing is performed in the ultrasonic probe to generate phasing addition data, and the phasing addition data is parallel / serial converted.

  However, in order to perform the digital beam forming process in the ultrasonic probe, the front end circuit in the conventional ultrasonic diagnostic apparatus must be entirely contained in the ultrasonic probe, and the circuit scale becomes enormous.

JP 2003-299648 A (page 3, FIG. 1) Japanese Patent Laying-Open No. 2008-18107 (page 4-5, FIG. 1)

  Accordingly, in view of the above points, the present invention reduces the number of received signals output from a plurality of ultrasonic transducers, thereby reducing the number of signal lines connecting the ultrasonic probe and the ultrasonic diagnostic apparatus body. The purpose is to reduce or make it wireless.

  In order to solve the above-described problem, an ultrasonic probe according to one aspect of the present invention transmits a plurality of ultrasonic waves according to a plurality of drive signals, receives an ultrasonic echo, and outputs a plurality of reception signals. A complex baseband signal is generated by performing orthogonal detection processing or orthogonal sampling processing on a transducer and a reception signal output from each ultrasonic transducer, and an amplitude signal and a complex baseband signal representing the amplitude of the complex baseband signal Signal processing means for generating a phase signal representing the phase of the signal, sampling means for generating sample data by sampling the amplitude signal and phase signal generated by the signal processing means, and parallel sample data generated by the sampling means Serialization means to convert the data into serial sample data Comprises a transmitting means for transmitting the serial sample data converted by the serial means.

  An ultrasonic diagnostic apparatus according to one aspect of the present invention converts an ultrasonic probe according to the present invention and serial sample data transmitted from the ultrasonic probe into parallel sample data. Parallelizing means for extracting the amplitude signal and phase signal, and phase correcting means for correcting the phase value represented by the phase signal extracted by the parallelizing means in accordance with the relative positions of the reception focus and the plurality of ultrasonic transducers Calculating means for obtaining a real component and / or an imaginary component of the complex baseband signal based on the amplitude value represented by the amplitude signal extracted by the parallelizing means and the phase value corrected by the phase correcting means; Real number generation of complex baseband signals determined by multiple means for multiple ultrasonic transducers To generate a phasing addition real number signal and / or to generate a phasing addition imaginary number signal by adding the imaginary components of the complex baseband signal obtained for a plurality of ultrasonic transducers by the arithmetic means. Adding means.

  According to one aspect of the present invention, in an ultrasonic probe, a complex baseband signal is generated by performing quadrature detection processing or quadrature sampling processing on a reception signal output from each ultrasonic transducer. Generates an amplitude signal representing the amplitude of the baseband signal and a phase signal representing the phase of the complex baseband signal, and converts the parallel sample data generated by sampling the amplitude signal and the phase signal into serial sample data. By transmitting to the ultrasonic diagnostic equipment body, the amount of received signal data output from multiple ultrasonic transducers can be reduced, reducing the number of signal lines connecting the ultrasonic probe and the ultrasonic diagnostic equipment. , Wireless can be achieved.

1 is a block diagram illustrating a configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. It is a figure which shows the 1st structural example of the transmission / reception part shown in FIG. It is a figure which shows the 2nd structural example of the transmission / reception part shown in FIG. It is a wave form diagram for demonstrating operation | movement of the orthogonal sampling part shown in FIG. It is a figure which shows the structural example of the phasing addition part shown in FIG. It is a figure for demonstrating operation | movement of the phasing addition part shown in FIG. FIG. 10 is a diagram illustrating a state of a reception signal when an ultrasonic beam is transmitted in the direction of a point O by an array transducer. FIG. 10 is a diagram illustrating a state of a reception signal when an ultrasonic beam is transmitted in the direction of a point O by an array transducer. It is a block diagram which shows the structure of the ultrasonic probe which concerns on the modification of one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same referential mark is attached | subjected to the same component and description is abbreviate | omitted.
FIG. 1 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. As shown in FIG. 1, this ultrasonic diagnostic apparatus includes an ultrasonic probe 1 according to an embodiment of the present invention and an ultrasonic diagnostic apparatus body 2.

  The ultrasonic probe 1 may be an external probe such as a linear scan method, a convex scan method, or a sector scan method, or an ultrasonic endoscope probe such as a radial scan method. As shown in FIG. 1, the ultrasonic probe 1 includes a plurality of ultrasonic transducers 10 constituting a one-dimensional or two-dimensional transducer array, a plurality of channels of transmission / reception units 20, a serialization unit 30, and a transmission control unit 40. And a transmission circuit 50.

  The plurality of ultrasonic transducers 10 transmit ultrasonic waves according to a plurality of applied driving signals, receive propagating ultrasonic echoes, and output a plurality of reception signals. Each ultrasonic transducer is, for example, a piezoelectric ceramic represented by PZT (Pb (lead) zirconate titanate) or a polymer piezoelectric element represented by PVDF (polyvinylidene difluoride). It is constituted by a vibrator in which electrodes are formed at both ends of a piezoelectric material (piezoelectric body).

  When a pulsed or continuous wave voltage is applied to the electrodes of such a vibrator, the piezoelectric body expands and contracts. By this expansion and contraction, pulsed or continuous wave ultrasonic waves are generated from the respective vibrators, and an ultrasonic beam is formed by combining the ultrasonic waves. Each vibrator expands and contracts by receiving propagating ultrasonic waves and generates an electrical signal. These electrical signals are output as ultrasonic reception signals.

  The transmission / reception unit 20 of each channel generates a drive signal under the control of the transmission control unit 40, supplies the drive signal to the ultrasonic transducer 10, and outputs a received signal output from the ultrasonic transducer 10. Generates a complex baseband signal by performing quadrature detection processing, etc., further generates an amplitude signal representing the amplitude of the complex baseband signal and a phase signal representing the phase of the complex baseband signal, and samples the amplitude signal and the phase signal The parallel sample data generated in this way is supplied to the serialization unit 30.

  FIG. 2 is a diagram illustrating a first configuration example of the transmission / reception unit illustrated in FIG. 1. As shown in FIG. 2, the transmission / reception unit 20 of each channel includes a transmission circuit 21, a preamplifier 22, a low-pass filter (LPF) 23, an analog / digital converter (ADC) 24, an orthogonal detection processing unit 25, An amplitude calculation unit 26a, a phase calculation unit 26b, sampling units 27a and 27b, and memories 28a and 28b are included. Here, the transmission circuit 21 to the phase calculation unit 26b constitute signal processing means.

  The transmission circuit 21 is configured by, for example, a pulsar, generates a drive signal under the control of the transmission control unit 40, and supplies the generated drive signal to the ultrasonic transducer 10. The scanning control unit 140 illustrated in FIG. 1 sequentially sets the transmission direction of the ultrasonic beam to generate a scanning control signal, and the transmission circuit 60 transmits the scanning control signal generated by the scanning control unit 140 to the transmission circuit 50. To do. The transmission control unit 40 controls the operation of the multiple-channel transmission circuit 21 based on the scanning control signal supplied from the transmission circuit 50.

  For example, the transmission control unit 40 selects one pattern from a plurality of delay patterns according to the transmission direction set by the scanning control signal, and based on the pattern, the drive signals for the plurality of ultrasonic transducers 10 are selected. The delay time given to each is set. Alternatively, the transmission control unit 40 may set the delay time so that the ultrasonic waves transmitted from the plurality of ultrasonic transducers 10 reach the entire imaging region of the subject.

  Based on the transmission delay pattern selected by the transmission control unit 40, the multi-channel transmission circuit 21 delays a plurality of drive signals so that the ultrasonic waves transmitted from the plurality of ultrasonic transducers 10 form an ultrasonic beam. A plurality of drive signals are supplied to a plurality of ultrasonic transducers 10 by adjusting the amount, or a plurality of drive signals are transmitted so that ultrasonic waves transmitted at a time from the plurality of ultrasonic transducers 10 reach the entire imaging region of the subject. It is supplied to the sonic transducer 10.

  The preamplifier 22 amplifies the reception signal (RF signal) output from the ultrasonic transducer 10, and the LPF 23 limits the band of the reception signal output from the preamplifier 21, thereby preventing aliasing in A / D conversion. To do. The ADC 24 converts the analog reception signal output from the LPF 23 into a digital reception signal. For example, if the ultrasonic frequency is about 5 MHz, a sampling frequency of 40 MHz is used. In this case, since the in-vivo distance corresponding to one sample is about 0.038 mm, data up to a depth of about 15.7 cm can be obtained with 4096 samples.

If the number of ultrasonic transducers in the reception aperture is 64, and 100 ultrasonic reception lines (sound rays) are required for one frame of an ultrasonic diagnostic image, it is necessary to display an image of one frame. The amount of data is 4096 × 64 × 100≈26 × 10 ⁶ , and in order to display an image of 10 frames per second, data transfer of about 260 × 10 ⁶ / sec is required. Here, since the resolution required for the ultrasonic diagnostic image is usually about 12 bits for one piece of data, a transmission bit rate of about 3120 Mbps is required to transmit the above data.

  Thus, when data is serialized with an RF signal as it is, the transmission bit rate becomes extremely high, and the communication speed and the operation speed of the memory cannot keep up with it. On the other hand, as described in the description of the background art, when data is serialized after the reception focus process, the transmission bit rate can be reduced. However, a circuit for reception focus processing is large in scale and is difficult to incorporate into an ultrasonic probe. Therefore, in this embodiment, the received signal is subjected to orthogonal detection processing or the like to reduce the frequency band of the received signal to the baseband frequency band, and further, the amplitude information and phase information of the complex baseband signal are obtained to obtain the data By performing serialization, the transmission bit rate is reduced.

The quadrature detection processing unit 25 performs quadrature detection processing on the received signal to generate a complex baseband signal (I signal and Q signal). As shown in FIG. 2, the quadrature detection processing unit 25 includes mixers (multiplication circuits) 25a and 25b and low-pass filters (LPF) 25c and 25d. The mixer 25a multiplies the received signal converted into a digital signal by the ADC 24 with the local oscillation signal cosω ₀ t, and the LPF 25c applies a low-pass filter process to the signal output from the mixer 25a, thereby representing the real component I A signal is generated. On the other hand, the mixer 25b multiplies the received signal converted into the digital signal by the ADC 24 with the local oscillation signal sin ω ₀ t rotated in phase by π / 2, and the LPF 25d applies the low-pass filter to the signal output from the mixer 25b. By performing the processing, a Q signal representing an imaginary component is generated.

The amplitude calculation unit 26a generates an amplitude signal representing the amplitude of the complex baseband signal generated by the quadrature detection processing unit 25. Here, when the I and Q signals constituting the complex baseband signal obtained based on the reception signal output from the i-th ultrasonic transducer are R (i) and I (i), respectively, the complex baseband The amplitude A (i) of the signal is expressed by the following equation (1).
A (i) = (R (i) ² + I (i) ² ) ^1/2 (1)

The phase calculation unit 26b generates a phase signal representing the phase of the complex baseband signal generated by the quadrature detection processing unit 25. Here, when the I and Q signals constituting the complex baseband signal obtained based on the reception signal output from the i-th ultrasonic transducer are R (i) and I (i), respectively, the complex baseband The phase φ (i) of the signal is expressed by the following equation (2).
φ (i) = arctan (I (i) / R (i)) (2)

In the case of a 12-bit AD converter that is most widely used at present, it is appropriate to set the operation word length after quadrature detection to 12 bits. Accordingly, if the I signal and the Q signal are serialized, a data amount of 24 bits is required in combination with the I signal and the Q signal. On the other hand, the data amount of the amplitude signal is ^21/2 times that of the I signal and the Q signal according to the equation (1), so 13 bits are sufficient.

  The data amount of the phase information depends on how much resolution the phase information at 2π is acquired. Since the resolution of the phase information corresponds to the time resolution, it is sufficient that the period is about 1/16 of the period of the transmitted / received ultrasonic frequency as compared with the conventional phasing addition. If this is the case, the data length of the phase information may be 4 bits. If the data length of the phase information is set to 6 bits, phase control can be performed with four times the accuracy compared to normal phasing addition.

  Even in this case, the data length of the amplitude signal and the data length of the phase signal are 19 bits, and the data amount can be reduced as compared with the case where the I signal and the Q signal are serialized. In serializing data using amplitude information and phase information, an optimum data word length can be selected for each according to the performance scale of the target device.

  The sampling unit 27a samples (resamples) the amplitude signal generated by the amplitude calculation unit 26a. The sampling unit 27b samples (resamples) the amplitude signal generated by the phase calculation unit 26b. Thereby, 2-channel sample data is generated. The generated 2-channel sample data is stored in the memories 28a and 28b, respectively.

  FIG. 3 is a diagram illustrating a second configuration example of the transmission / reception unit illustrated in FIG. 1. In the second configuration example shown in FIG. 3, an orthogonal sampling unit 25e is provided instead of the mixers 25a and 25b in the first configuration example shown in FIG.

FIG. 4 is a waveform diagram for explaining the operation of the orthogonal sampling unit shown in FIG. Quadrature sampling unit 25e is to synchronize the received signal converted into a digital signal to the phase of the cos .omega _{0 t} to generate a first signal sequence by sampling by ADC 24, synchronizes the received signal to the phase of sin .omega _{0 t} To generate a second signal sequence.

  Further, the LPF 25c performs low-pass filter processing on the first signal sequence output from the orthogonal sampling unit 25e, thereby generating an I signal representing a real component, and the LPF 25d is output from the orthogonal sampling unit 25e. A Q signal representing an imaginary component is generated by performing low-pass filter processing on the signal series. Thereby, the mixers 25a and 25b shown in FIG. 2 can be omitted.

  Referring to FIG. 1 again, the serialization unit 30 converts the parallel sample data generated by the transmission / reception unit 20 of a plurality of channels into serial sample data. For example, the serialization unit 30 converts 128 channel parallel sample data obtained based on 64 received signals output from 64 ultrasonic transducers into 1-4 channel serial sample data. This significantly reduces the number of transmission channels compared to the number of ultrasonic transducers.

  The transmission circuit 50 receives the scanning control signal from the ultrasonic diagnostic apparatus body 2, outputs the received scanning control signal to the transmission control unit 40, and ultrasonically converts the serial sample data converted by the serializing unit 30. It transmits to the diagnostic apparatus main body 2. Signal transmission between the ultrasonic probe 1 and the ultrasonic diagnostic apparatus main body 2 is, for example, ASK (Amplitude Shift Keying), PSK (Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation). Or the like using a communication method such as wired or wireless. When using ASK or PSK, it is possible to transmit one channel of serial data with one system. When using QPSK, it is possible to transmit two channels of serial data with one system. When 16QAM is used, four channels of serial data can be transmitted in one system.

  The power supply voltage of the ultrasonic probe 1 is supplied from the ultrasonic diagnostic apparatus main body 2 when signal transmission between the ultrasonic probe 1 and the ultrasonic diagnostic apparatus main body 2 is performed by wire. When signal transmission with the sonic diagnostic apparatus main body 2 is performed wirelessly, it is supplied by a battery or the like. When the power supply voltage of the ultrasonic probe 1 is supplied from the ultrasonic diagnostic apparatus body 2, phantom power supply is performed using a signal line connected between the ultrasonic probe 1 and the ultrasonic diagnostic apparatus body 2. Also good.

  In the above, the quadrature detection processing unit 25 (FIG. 2), the amplitude calculation unit 26a (FIG. 2), the phase calculation unit 26b (FIG. 2), the sampling units 27a and 27b (FIG. 2), the quadrature sampling unit 25e (FIG. 3), The LPFs 25c and 25d (FIG. 3) and the serializing unit 30 may be configured by digital circuits, or by a central processing unit (CPU) and software (program) for causing the CPU to perform various processes. It may be configured. Alternatively, the ADC 24 may be omitted by configuring the quadrature detection processing unit 25 with an analog circuit. In that case, A / D conversion of the complex baseband signal is performed by the sampling units 27a and 27b.

  On the other hand, the ultrasonic diagnostic apparatus main body 2 shown in FIG. 1 includes a transmission circuit 60, a parallelization unit 70, a phasing addition unit 80, a B-mode image signal generation unit 90, a display unit 100, and an operation unit 110. , A control unit 120, a storage unit 130, and a scanning control unit 140.

  The transmission circuit 60 receives serial sample data from the ultrasonic probe 1. The parallelizing unit 70 converts the serial sample data received by the transmission circuit 60 into parallel sample data, and obtains the parallel sample data from the parallel sample data based on a plurality of reception signals output from the plurality of ultrasonic transducers 10. The plurality of amplitude signals and the plurality of phase signals thus obtained are extracted and supplied to the phasing adder 80. The scanning control unit 140 sequentially sets the reception direction of the ultrasonic echoes and controls the phasing addition unit 80.

  FIG. 5 is a diagram illustrating a configuration example of the phasing addition unit illustrated in FIG. 1. As shown in FIG. 5, the phasing addition unit 80 includes a phase correction unit 81, a phase correction value table 82, a multi-channel delay I signal calculation unit 83, a multi-channel delay Q signal calculation unit 84, and a delay. An I signal adding unit 85 and a delayed Q signal adding unit 86 are included.

  The phase correction unit 81 uses the phase correction value stored in the phase correction value table 82 to thereby extract the phase signal extracted by the parallelizing unit 70 according to the relative position between the reception focus and the plurality of ultrasonic transducers. The phase value represented by is corrected. The delayed I signal calculation unit 83 is based on the amplitude value represented by the amplitude signal extracted by the parallelization unit 70 and the phase value corrected by the phase correction unit 81, and the real component of the delayed complex baseband signal (Delayed I signal) is obtained. Further, the delayed Q signal calculation unit 84 is based on the amplitude value represented by the amplitude signal extracted by the parallelization unit 70 and the phase value corrected by the phase correction unit 81, and An imaginary component (delayed Q signal) is obtained.

  The delay I signal addition unit 85 adds the delay I signals obtained for the plurality of ultrasonic transducers by the delay I signal calculation unit 83 of the plurality of channels, thereby obtaining a phasing addition real signal (phasing addition I signal). Generate. Further, the delay Q signal adding unit 86 adds the delay Q signals obtained for the plurality of ultrasonic transducers by the plurality of channels' delay Q signal calculating unit 84 to thereby obtain a phasing addition imaginary signal (phasing addition Q signal). ) Is generated.

FIG. 6 is a diagram for explaining the operation of the phasing adder shown in FIG. FIG. 6 shows signal processing for one channel corresponding to one ultrasonic transducer.
The phase correction value table 82 stores a phase correction value φ for correcting the phase value θ represented by the phase signal in accordance with the geometric relative position between the reception focus and the plurality of ultrasonic transducers. Yes. The phase correction unit 81 reads the phase correction value φ from the phase correction value table 82 according to the reception direction set in the scanning control unit 11, and subtracts the phase correction value φ from the phase value θ represented by the phase signal. Thus, a correction phase value (θ−φ) is obtained. This corresponds to delaying the complex baseband signal by a time corresponding to the phase correction value φ.

  The delayed I signal calculation unit 83 is based on the amplitude value A represented by the amplitude signal and the phase value (θ−φ) corrected by the phase correction unit 81, and the real component (delayed) of the delayed complex baseband signal. A · cos (θ−φ) which is an I signal) is obtained. Further, the delay Q signal calculation unit 84 is based on the amplitude value A represented by the amplitude signal and the phase value (θ−φ) corrected by the phase correction unit 81, and the imaginary component of the delayed complex baseband signal. A · sin (θ−φ) which is (delayed Q signal) is obtained.

  Referring to FIG. 5 again, the delay I signal adding unit 85 performs the reception focus process by adding the delay I signals respectively obtained for the plurality of ultrasonic transducers by the plurality of channels of the delay I signal calculating unit 83. By this reception focus processing, a phasing addition I signal in which the focus of the ultrasonic echo is narrowed is generated. The delay Q signal addition unit 86 performs reception focus processing by adding the delay Q signals obtained for the plurality of ultrasonic transducers by the delay Q signal calculation unit 84 of the plurality of channels. By this reception focus processing, a phasing addition Q signal in which the focus of the ultrasonic echo is narrowed is generated.

  As described above, by correcting the phase value θ, the complex baseband signal obtained by quadrature detection or the like is not subjected to data interpolation processing, and is more accurately adjusted using a continuous delay amount than before. A reception focus process for performing phase addition can be realized. In addition, the phasing and adding circuit can be simplified, and focus setting with a high degree of freedom is possible.

  Referring back to FIG. 1, the B-mode image signal generation unit 90 includes the phasing addition I signal generated by the delay I signal addition unit 85 and / or the phasing addition Q generated by the delay Q signal addition unit 86. Based on the signal, a B-mode image signal representing the ultrasonic diagnostic image is generated. Here, the B mode is a mode for displaying the two-dimensional tomographic image by converting the amplitude of the ultrasonic echo into luminance. The B-mode image signal generation unit 90 includes an amplitude value calculation unit 91, an STC (sensitivity time control) unit 92, and a DSC (digital scan converter) 93.

  The amplitude value calculation unit 91 obtains the square root of the sum of squares of the phasing addition I signal and the phasing addition Q signal, thereby generating a phasing addition signal representing the amplitude value of the complex baseband signal subjected to the phasing addition. . The STC unit 92 corrects attenuation with respect to the phasing addition signal generated by the phasing addition unit 80 according to the depth of the reflection position of the ultrasonic wave.

  The DSC 93 converts the phasing addition signal corrected by the STC unit 92 into an image signal in accordance with a normal television signal scanning method (raster conversion), and performs necessary image processing such as gradation processing to perform the B mode. An image signal is generated. The display unit 100 includes a display device such as an LCD, for example, and displays an ultrasound diagnostic image based on the B-mode image signal generated by the B-mode image signal generation unit 90.

  Alternatively, the image signal generation unit 70 can also generate an image signal based on one of the phasing addition I signal and the phasing addition Q signal. While omitted, the delay Q signal calculation unit 84 and the delay Q signal addition unit 86 may be omitted, or the delay I signal calculation unit 83 and the delay I signal addition unit 85 may be omitted.

  The control unit 120 controls the scanning control unit 140 and the like according to the operation of the operator using the operation unit 110. In this embodiment, the parallel unit 70, the phasing addition unit 80, the B-mode image signal generation unit 90, the control unit 120, and the scanning control unit 140 perform various processes on the central processing unit (CPU) and the CPU. Although it is configured by software (program) for execution, it may be configured by a digital circuit or an analog circuit. The software (program) is stored in the storage unit 130. As a recording medium in the storage unit 130, a flexible disk, MO, MT, RAM, CD-ROM, DVD-ROM, or the like can be used in addition to the built-in hard disk.

Here, the principle of the present invention will be described in detail with reference to FIGS.
7 and 8 are views showing the state of the reception signal when the ultrasonic beam is transmitted in the direction of the point O by the array transducer. In FIG. 7, it is assumed that the matrix above the transducers p _{1 to} p ₉ represents a digitized reception signal. The column above each transducer indicates the received signal from that transducer at time t. For example, if the center of the vibrator p ₅ at a certain time receiving ultrasonic echoes from the point O, the received signal is stored in the position of e _5. The received signals from the transducers p ₁ and p _{9 at} both ends received at the same timing are stored at positions e ₁ and e ₉ , respectively.

However, these received signals represent ultrasonic echoes from a shorter distance than point O, and the ultrasonic echoes from point O arrive with a delay of time t ₁ and t ₉ , respectively. , Respectively, at the positions e ₁ ′ and e ₉ ′. At this time, if the point O is directly below the transducer p ₅ , t ₁ = t ₉ , so the positions of e ₁ ′ and e ₉ ′ are also the same. In conventional beam forming, a method is adopted in which the received signal at the position e ₅ is actually delayed by time t ₁ and added to the received signals at the positions e ₁ ′ and e ₉ ′.

In FIG. 8, it is assumed that the received signal e (nT) at the position of e1 by the vibrator p1 is expressed by Expression (3).
e (nT) = A (nT) · exp {j (2πf ₀ nT + θ ₀ )} (3)
Here, A (nT) is the signal intensity of the ultrasonic echo from the point O, and nT indicates that the sampling interval is the nth data AD-converted at the sampling rate of T. This received signal has a phase rotation corresponding to the time nT with respect to the transmission frequency f ₀ , and θ ₀ is an initial value of the phase according to the depth. Here, the received signal e _i (nT) by other vibrators received at the same time is expressed by Expression (4).
e _i (nT) = A (nT + t (i, n))
Exp {j (2πf ₀ (nT + t (i, n)) + θ ₀ )} (4)

Since this received signal e _i (nT) is a signal from a depth corresponding to the time t ₁ , it is a received signal from a point O ′ deeper than the point O. For example, in FIG. 8, considering the signal received by the transducer p _5, as compared with the received signal at the position of e _1, the time is that they are preceded by (t 1 _{-t 5).} Since this time difference is represented by the position of the transducer and the reception time, it can be represented by t (i, n). Further, t (i, n) can be calculated from the geometric relative position between the sound source and the vibrator. In conventional beamforming, the received signal e _i (nT) is delayed by the time difference t (i, n), thereby causing the received signal e _i (nT) to be in phase with the received signal e (nT). And phasing addition is performed by adding them.

In the baseband method, the received signal is converted into a baseband I signal and Q signal by performing quadrature detection on the received signal. The received signals represented by Expression (3) and Expression (4) are converted to baseband and represented by Expression (5) and Expression (6).
E (nT) = e (nT) · exp {−j (2πf ₀ nT)}
= A (nT) · exp {−jθ ₀ } (5)
E _i (nT) = e _i (nT) · exp {−j (2πf ₀ nT)}
= A (nT + t (i, n)) · exp {j (2πf ₀ t (i, n) + θ ₀ )} (6)

Here, when t (i, n)> nT, the state of t (i, n) <nT can be obtained by changing the sample point n. For example, since it is possible to set t (i, n) = mT + t _i , the mth data is used instead of the nth data in E _i (nT). This means that data corresponding to different depths is used in the memory, where t _i <T. At this time, if T <1 / (2f ₀ ) before re-sampling, 2πf ₀ t _i <π. This indicates that delays greater than or equal to T can be corrected by using different sample point data, and only delays t _i less than or equal to T need to be corrected. From this, equation (6) can be replaced by equation (7).
E _i (nT) = A (mT + t _i ) · exp {j (2πf ₀ t _i + θ ₀ )} (7)

Here, considering that t _i is sufficiently small, A (nT + t _i ) is considered to be equal to or lower than the resolution, and therefore may be replaced with A (nT). For simplicity, replacement is performed as shown in equations (8) and (9). However, An and .theta.n _i is the amplitude and phase after the orthogonal detection.
A (nT) = A (mT + t _i ) = An (8)
2πf ₀ t _i + θ ₀ = θn _i (9)

Therefore, delaying the signal of equation (7) by time t _i corresponds to returning the phase by time t _i . Therefore, the I signal and the Q signal can be obtained by Expression (10) and Expression (11), respectively.
Rn _i = An · cos {θn _i −φ (i, n)} (10)
In _i = An · sin {θn _i −φ (i, n)} (11)
However, (phi) (i, n) is shown by Formula (12), and can be calculated from the geometric relative position of a sound source and a vibrator.
φ (i, n) = 2πf ₀ t (i, n) (12)

画像表示に当たっては、例えば、整相加算された式（１３）及び式（１４）に基づいて、式（１５）に示すように振幅値Ｖｎを算出すれば良い。

The I signal and the Q signal obtained by Expression (10) and Expression (11) are added by the number of transducers, and as shown in Expression (13) and Expression (14), the information subjected to phasing addition is obtained. Rn and In can be obtained.

In displaying an image, for example, the amplitude value Vn may be calculated as shown in Expression (15) based on Expressions (13) and (14) subjected to phasing addition.

  Next, a modification of one embodiment of the present invention will be described. FIG. 9 is a block diagram showing a configuration of an ultrasonic probe according to a modification of the embodiment of the present invention. In the ultrasonic probe 1 a shown in FIG. 9, a switching circuit that switches the connection relationship between the plurality of ultrasonic transducers 10 provided in the ultrasonic probe and the transmission / reception unit 20 with respect to the ultrasonic probe 1 shown in FIG. 1. 11 has been added.

  In general, in an ultrasonic probe of a linear scan method or a convex scan method, a subject is scanned while the apertures in transmission and reception are sequentially switched. When the number of ultrasonic transducers provided in the ultrasonic probe 1a is N and the number of ultrasonic transducers used at the same time is M (M <N), the switching circuit 11 includes N ultrasonic transducers. M ultrasonic transducers are selected, and the selected M ultrasonic transducers are connected to the M transmitting / receiving units 20, respectively. Thereby, compared with the ultrasonic probe 1 shown in FIG. 1, the number of the transmission / reception parts 20 can be reduced.

  INDUSTRIAL APPLICABILITY The present invention can be used in an ultrasonic diagnostic apparatus that performs imaging of an organ or the like in a living body by transmitting and receiving ultrasonic waves and generates an ultrasonic diagnostic image used for diagnosis.

DESCRIPTION OF SYMBOLS 1 Ultrasonic probe 2 Ultrasonic diagnostic apparatus main body 10 Ultrasonic transducer 11 Switching circuit 20 Transmission / reception part 21 Transmission circuit 22 Preamplifier 23 LPF
24 ADC
25 Quadrature detection processing unit 25a, 25b Mixer 25c, 25d LPF
25e Quadrature sampling unit 26a Amplitude calculation unit 26b Phase calculation unit 27a, 27b Sampling unit 28a, 28b Memory 30 Serialization unit 40 Transmission control unit 50, 60 Transmission circuit 70 Parallelization unit 80 Phased addition unit 90 B-mode image signal generation unit 91 Amplitude value calculation unit 92 STC unit 93 DSC
DESCRIPTION OF SYMBOLS 100 Display part 110 Operation part 120 Control part 130 Storage part 140 Scan control part

Claims (9)

A plurality of ultrasonic transducers for transmitting ultrasonic waves according to a plurality of drive signals, receiving ultrasonic echoes and outputting a plurality of received signals;
A complex baseband signal is generated by performing quadrature detection processing or quadrature sampling processing on the reception signal output from each ultrasonic transducer, and the amplitude signal indicating the amplitude of the complex baseband signal and the phase of the complex baseband signal are calculated. Signal processing means for generating a representing phase signal;
Sampling means for generating sample data by sampling the amplitude signal and the phase signal generated by the signal processing means;
Serializing means for converting parallel sample data generated by the sampling means into serial sample data;
Transmission means for transmitting serial sample data converted by the serialization means;
An ultrasonic probe comprising:   The ultrasonic probe according to claim 1, further comprising a switching circuit that switches a connection relationship between the plurality of ultrasonic transducers provided in the ultrasonic probe and the signal processing means. The signal processing means is
A preamplifier for amplifying the reception signal output from each ultrasonic transducer;
A low-pass filter for limiting the band of the received signal output from the preamplifier;
An analog / digital converter that converts an analog reception signal output from the low-pass filter into a digital reception signal;
Orthogonal detection processing means for generating a complex baseband signal by performing orthogonal detection processing on the digital received signal converted by the analog / digital converter;
Amplitude calculating means for generating an amplitude signal representing the amplitude of the complex baseband signal generated by the quadrature detection processing means;
Phase calculating means for generating a phase signal representing the phase of the complex baseband signal generated by the quadrature detection processing means;
The ultrasonic probe according to claim 1, comprising: The signal processing means is
A preamplifier for amplifying the reception signal output from each ultrasonic transducer;
A low-pass filter for limiting the band of the received signal output from the preamplifier;
An analog / digital converter that converts an analog reception signal output from the low-pass filter into a digital reception signal;
Orthogonal sampling means for generating a first signal sequence and a second signal sequence by subjecting a digital received signal converted by the analog / digital converter to orthogonal sampling processing;
Low-pass filter means for generating a complex baseband signal by limiting the bands of the first and second signal sequences generated by the orthogonal sampling means, respectively;
Amplitude calculating means for generating an amplitude signal representing the amplitude of the complex baseband signal generated by the low-pass filter means;
Phase calculating means for generating a phase signal representing the phase of the complex baseband signal generated by the low-pass filter means;
The ultrasonic probe according to claim 1, comprising:   The ultrasonic probe according to claim 3 or 4, wherein the signal processing means further includes a plurality of transmission circuits that respectively supply a plurality of drive signals to the plurality of ultrasonic transducers.   The ultrasonic probe according to claim 1, wherein the transmission unit wirelessly transmits the serial sample data converted by the serialization unit. The ultrasonic probe according to any one of claims 1 to 6,
Parallelizing means for converting serial sample data transmitted from the ultrasonic probe into parallel sample data, and extracting an amplitude signal and a phase signal from the parallel sample data;
Phase correction means for correcting a phase value represented by the phase signal extracted by the parallelization means according to a relative position between the reception focus and the plurality of ultrasonic transducers;
Arithmetic means for obtaining a real component and / or an imaginary component of the complex baseband signal based on the amplitude value represented by the amplitude signal extracted by the parallelization means and the phase value corrected by the phase correction means;
A phasing addition real signal is generated by adding the real component of the complex baseband signal obtained for the plurality of ultrasonic transducers by the calculation means, and / or for the plurality of ultrasonic transducers by the calculation means. Adding means for generating a phasing addition imaginary signal by adding the imaginary component of the obtained complex baseband signal;
An ultrasonic diagnostic apparatus comprising: The arithmetic means obtains a real component and an imaginary component of the complex baseband signal based on the amplitude value represented by the amplitude signal extracted by the parallelization means and the phase value corrected by the phase correction means,
The adding means generates a phasing addition real number signal by adding the real number components of the complex baseband signals obtained for the plurality of ultrasonic transducers by the calculating means, and the calculating means sets the plurality of ultrasonic waves. The ultrasonic diagnostic apparatus according to claim 7, wherein a phasing addition imaginary signal is generated by adding an imaginary component of a complex baseband signal obtained for the transducer.   The image signal generating means for generating an image signal representing an ultrasonic diagnostic image based on the square root of the square sum of the phasing addition real signal and the phasing addition imaginary signal obtained by the adding means. 8. The ultrasonic diagnostic apparatus according to 8.

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