JP2005095320A - Ultrasonic transceiver and ultrasonic transceiving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To create an image using detecting signals of vibro-sound formed by reflectedly propagating the vibro-sound generated in a subject from a reflection body in the subject, in an ultrasonic transceiver. <P>SOLUTION: This ultrasonic transceiver is provided with transmitting elements 11 and 12 transmitting ultrasonic wave to the subject according to a plurality of impressed drive signals; synthesizers 21 and 22 generating the plurality of drive signals to be impressed to the transmitting elements 11 and 21 respectively; a system control part 41 transmitting the ultrasonic wave having frequency f<SB>1</SB>from the transmitting element 11 toward an area in the subject and controlling the synthesizers 21 and 22 to transmit the ultrasonic wave having frequency f<SB>2</SB>from the transmitting element 12; a plurality of receiving parts 15a and 15c receiving the vibro-sound generated in the subject and outputting a plurality of detecting signals respectively; and a correlation part 45 and a reflected position estimating arithmetic part 46 computing a plurality of detecting signals output from the receiving parts 15a-15c respectively and generating information related to the reflection area in the subject reflecting the received vibro-sound. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultrasonic transmission / reception apparatus and an ultrasonic transmission / reception method that are used for diagnosis of an organ in a living body by transmitting / receiving ultrasonic waves.

  In the medical field, various imaging techniques have been developed in order to perform diagnosis by observing the inside of a subject. Among them, ultrasonic imaging that acquires internal information of a subject by transmitting and receiving ultrasonic waves is not exposed to radiation unlike other medical imaging techniques such as X-ray photographs and RI (radio isotope) scintillation cameras. Therefore, ultrasonic imaging is used in a wide range of areas including fetal diagnosis, gynecology, circulatory system, digestive system, etc. in the obstetric field as a highly safe imaging technique.

  In ultrasonic imaging, an image is generated by detecting ultrasonic waves reflected at the boundary between substances having different acoustic impedances. Here, in general, ultrasonic waves have a property of being easily attenuated as the frequency increases. Therefore, when imaging a shallow part of a subject, ultrasonic waves with a relatively high frequency (for example, about 5 MHz) are used, and when imaging a deep part of the subject, a relatively low frequency (for example, 2 MHz). Degree) ultrasound is used. In particular, when there is a boundary having a large difference in acoustic impedance, such as a bone, an ultrasonic wave having a relatively low frequency (for example, 0.5 MHz) is used.

By the way, in the case of a two-dimensional array of circular apertures, the azimuth resolution ΔY of the ultrasonic beam is expressed as follows using the focal length F, the wavelength λ of the ultrasonic wave, and the diameter D of the aperture. Is done.
ΔY = 1.22 × F × λ / D
If the aperture has the same size, the smaller the wavelength λ of the ultrasonic wave, that is, the higher the frequency of the ultrasonic wave, the smaller the value of ΔY and the better the azimuth resolution. On the contrary, the larger the wavelength λ of the ultrasonic wave, that is, the lower the frequency of the ultrasonic wave, the larger the value of ΔY and the lower the azimuth resolution. On the other hand, the size of the opening is limited to a certain size depending on the relationship with the size of the subject. Therefore, if low-frequency ultrasonic waves are used to image the deep part of the subject, the azimuth resolution becomes low, so that it is impossible to image a fine structure in the deep part such as the inside of a bone.

  By the way, it is known that when an object is irradiated with two ultrasonic waves having slightly different frequencies, a vibration having a frequency corresponding to the difference between the frequencies of the two ultrasonic waves is generated from the portion irradiated with the ultrasonic waves. . This vibration is also called a vibro sound. According to Non-Patent Document 1, a mechanism for generating a vibro sound is considered as follows. That is, it is explained that it is due to a physical phenomenon such as (1) a change in impedance at the examination position of the subject, radiation pressure due to absorption and diffusion of ultrasonic waves, or (2) reflection of an acoustic beam generated by nonlinear interference Has been.

  Since such a vibro sound has an audible range of several kHz to an ultrasonic band of about several hundred kHz, for example, it passes through a boundary where the difference in acoustic impedance is large, or from the deep part of the subject. Even with the vibro sound that has returned, a signal having sufficient intensity can be obtained. In addition, since high-frequency ultrasonic waves are used when generating a vibro sound, a high resolution can be realized by narrowing down the scanning area of the vibro sound. Therefore, Non-Patent Document 1 describes that the inside of a bone taken out from a subject is imaged using a vibro sound. Non-Patent Document 2 describes that a fine structure in a deep part of a subject is imaged. Furthermore, Patent Document 1 discloses receiving a vibro sound in an audible range. Patent Document 2 discloses that electronic scanning is performed using a multi-ring annular array or a plurality of ultrasonic transducers in order to generate vibro sound.

  In these documents, it is assumed that a vibro sound is generated from a position (secondary sound source) where two ultrasonic waves transmitted from a transmitting element (primary sound source) form a focal point. Sound wave information is collected by receiving using a non-directional receiving element. However, in the subject, the vibro sound generated from the secondary sound source is reflected from a reflector such as another tissue, so that the vibro sound (vibration sound) having the position of the reflector as the sound source (tertiary sound source) is obtained. Indirect waves are considered to have occurred. However, conventionally, such an indirect wave of vibro sound has not been received and imaged.

In addition, since the frequency of the vibro sound is included in the audible range or a frequency band slightly higher than that, a receiving element that covers these bands is used when receiving the vibro sound. Sound waves and ultrasonic waves in such a band propagate without being scattered even in the air. Therefore, there is no problem when receiving a frequency band generally used in ultrasonic diagnosis (for example, 3 MHz to 10 NHz), but when receiving a vibro sound, a sound wave or an ultrasonic wave propagating in the air. May be mixed into the detection signal, which may hinder ultrasonic diagnosis.
US Pat. No. 5,903,516 US Pat. No. 5,991,239 Samuel Calle et al., “Application of Vibro-Acoustography to Bone Elasticity Imaging”, 2001 IEEE Ultrasound Symposium, pages 1601-1605. Fatemi, Greenleaf, “Ultrasound-Stimulated Vibro-Acoustic Spectrography”, Science, 280, April 3, 1998, 82 Pages-85

  Therefore, the present invention provides an ultrasonic transmission / reception apparatus and an ultrasonic transmission / reception method that reflect not only a vibro sound generated by transmitting an ultrasonic wave but also such a vibro sound reflected by a reflector in a subject. A first object is to generate an image using a vibro sound detection signal that propagates next. A second object of the present invention is to reduce the influence of noise caused by sound waves and ultrasonic waves propagating in the air in an ultrasonic transmission / reception apparatus and an ultrasonic transmission / reception method for generating an image by receiving vibro sound. To do.

  In order to solve the above-described problem, an ultrasonic transmission / reception apparatus according to a first aspect of the present invention includes a first transmission unit and a second transmission that respectively transmit ultrasonic waves to a subject according to a plurality of applied drive signals. Means, drive signal generating means for generating a plurality of drive signals respectively applied to the first and second transmitting means, and a first ultrasonic wave from the first transmitting means toward a region in the subject. A control means for controlling the drive signal generation means so as to transmit a second ultrasonic wave having a frequency different from that of the first ultrasonic wave from the second transmission means toward the region, and the subject. A plurality of third ultrasonic waves or sound waves generated based on the first and second ultrasonic waves and having a difference frequency between the first ultrasonic frequency and the second ultrasonic frequency. A plurality of receiving means for outputting detection signals of Computation means for generating information on a reflection area in the subject that has reflected the received third ultrasonic wave or sound wave by performing arithmetic processing on a plurality of detection signals respectively output from the plurality of reception means. To do.

  An ultrasonic transmission / reception apparatus according to a second aspect of the present invention includes a first transmission unit and a second transmission unit that transmit ultrasonic waves to a subject according to a plurality of applied drive signals, respectively, Driving signal generation means for generating a plurality of drive signals respectively applied to the second transmission means, first ultrasonic waves are transmitted from the first transmission means toward the region within the subject, and second Control means for controlling the drive signal generation means so as to transmit a second ultrasonic wave having a frequency different from that of the first ultrasonic wave from the transmission means toward the region, and the first and the first in the subject. Receiving at least one first ultrasonic wave or sound wave generated based on the two ultrasonic waves and having a frequency that is a difference between the frequency of the first ultrasonic wave and the frequency of the second ultrasonic wave At least one first receiving means for outputting a signal A second receiving means for receiving an ultrasonic wave or a sound wave propagating from outside the subject and outputting a second detection signal; at least one first detection signal; and a gain and / or phase adjusted first The processing means for generating at least one third detection signal by taking a difference from the two detection signals, and performing arithmetic processing on at least one third detection signal, thereby receiving the received third super signal. And a calculation means for generating information on the reflection region in the subject that reflects the sound wave or the sound wave.

  The ultrasonic transmission / reception method according to the first aspect of the present invention transmits a first ultrasonic wave and a second ultrasonic wave having a frequency different from that of the first ultrasonic wave toward a region in the subject. And (a) a third frequency generated based on the first and second ultrasonic waves in the subject and having a frequency difference between the frequency of the first ultrasonic wave and the frequency of the second ultrasonic wave. Step (b) of receiving the ultrasonic waves or sound waves by using a plurality of receiving means and outputting a plurality of detection signals, respectively, and performing arithmetic processing on the plurality of detection signals respectively output from the plurality of receiving means (C) generating information on a reflection region in the subject that has reflected the received third ultrasonic wave or sound wave.

  In addition, in the ultrasonic transmission / reception method according to the second aspect of the present invention, the first ultrasonic wave and the second ultrasonic wave having a different frequency from the first ultrasonic wave are directed to the region in the subject. And a third transmission step that is generated based on the first and second ultrasonic waves in the subject and has a difference frequency between the first ultrasonic frequency and the second ultrasonic frequency. Receiving at least one first detection signal by receiving ultrasonic waves or sound waves, receiving at least one ultrasonic wave or sound waves propagating from outside the subject and outputting second detection signals, and at least one at least one Generating at least one third detection signal by taking a difference between the first detection signal and a second detection signal with adjusted gain and / or phase; and at least one third detection By performing arithmetic processing on the signal, And a step of generating information about the reflection area within a subject reflected by the third ultrasound or sound waves.

  According to the present invention, by performing arithmetic processing on the detected third ultrasonic wave or sound wave, that is, a detection signal of the vibro sound, the generated vibro sound is secondarily propagated by being reflected from the reflector. An image can be generated using the vibro sound detection signal. Therefore, it is possible to obtain information on the reflector reflecting such a vibro sound and to image the internal tissue of the bone. Further, according to the present invention, since noise propagating from outside the subject is detected and subtracted from the signal output by the vibro sound receiving means, a vibro sound detection signal with a high S / N ratio can be obtained.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The same constituent elements are denoted by the same reference numerals, and the description thereof is omitted.
FIG. 1 is a block diagram showing a configuration of an ultrasonic transmission / reception apparatus according to the first embodiment of the present invention. This ultrasonic transmission / reception apparatus transmits an ultrasonic wave, receives an ultrasonic echo from a subject, images it, generates a vibro sound in the subject, and transmits a vibro sound propagating in the subject. It is a device that receives and images.

  First, the vibro sound will be described. As shown in FIG. 2, when two ultrasonic beams US1 and US2 having slightly different frequencies are transmitted toward the object 101, vibration occurs in the vicinity of the region P irradiated with the two ultrasonic waves (also referred to as “vibro phenomenon”). Say). This vibration is a sound wave (ultrasonic wave) called a vibro sound. FIG. 2 shows the wavefront of the vibro sound. The vibro sound has a frequency corresponding to the difference frequency between the two ultrasonic waves US1 and US2 (for example, an audible range of about several kHz to an ultrasonic band of about several hundred kHz). In this way, vibro sound generally has a lower frequency than ultrasonic waves used for ultrasonic imaging, and therefore easily reaches the deep part of the subject (good penetration). In addition, since a sound wave (ultrasonic wave) having such a low frequency is formed by transmitting an ultrasonic wave having a high frequency, a narrow beam spot compared to the case of directly transmitting an ultrasonic wave having a low frequency. Can be formed. That is, by using the vibro sound, it is possible to generate an ultrasonic image in which good depth to the subject and high resolution are compatible.

As shown in FIG. 1, this ultrasonic transmission / reception apparatus includes an ultrasonic transmission unit 10, a mechanical stage 13, an ultrasonic reception unit 14, and a plurality of vibro sound reception units 15a used in contact with a subject 100. ~ 15c.
The ultrasonic transmission unit 10 includes transmission elements 11 and 12. As the transmitting elements 11 and 12, both ends of a piezoelectric element such as a ceramic piezoelectric material such as PZT (Pb (lead) zirconate titanate) or a polymeric piezoelectric material such as PVDF (polyvinyliden difluoride). It is comprised by the ultrasonic transducer which formed the electrode in. When a voltage is applied by sending a continuous wave drive signal to the electrodes of such an ultrasonic transducer, the piezoelectric element expands and contracts. Due to the expansion and contraction, continuous ultrasonic waves are generated from the respective ultrasonic transducers.

The transmission element 11 has an annular shape, and the transmission element 12 has a circular shape. Alternatively, the transmission element 12 may be formed in an annular shape. These transmitting elements 11 and 12 are arranged concentrically and constitute a coaxial annular array. In the ultrasonic transmission unit 10 shown in FIG. 1, cross sections of the transmission elements 11 and 12 are shown. By arranging the transmitting elements in this way, a plurality of ultrasonic beams transmitted from different transmitting elements 11 and 12 can be focused at the same depth in the same direction.
The mechanical stage 13 mechanically drives the ultrasonic transmission unit 10 including the transmission elements 11 and 12. Thereby, the subject 100 is linearly scanned by the ultrasonic waves transmitted from the ultrasonic transmission unit 10.

  The ultrasonic receiving unit 14 has a receiving element including PZT and the like, and is a hydrophone that receives an ultrasonic wave propagating from a subject and outputs a detection signal. The ultrasonic receiver 14 is mechanically connected to the ultrasonic transmitter 10, and moves with the ultrasonic transmitter 10 that is mechanically driven by the mechanical stage 13.

  Each of the vibro sound receiving units 15a to 15c includes a receiving element including PZT and the like, and is a hydrophone that receives a vibro sound propagating from a subject and outputs a detection signal. These receiving elements expand and contract by receiving propagating ultrasonic waves and generate electrical signals. These electric signals are output as detection signals for ultrasonic waves and vibro sounds.

  FIG. 3 shows the frequency characteristics of the transmission element and the reception element used in the ultrasonic transmission / reception apparatus according to the present embodiment. As illustrated in FIG. 3, the transmission elements 11 and 12 included in the ultrasonic transmission unit 10 are set to have the highest sensitivity in the megahertz band (for example, 3 MHz to 10 MHz). In addition, the receiving element included in the ultrasonic receiving unit 14 has a substantially constant receiving sensitivity in a frequency band of several hundred kHz to several tens of MHz. Furthermore, the receiving elements included in the vibro sound receiving units 15a to 15c have a substantially constant receiving sensitivity in a frequency band of several hundred Hz to several hundred kHz.

  Referring to FIG. 1 again, this ultrasonic transmission / reception apparatus includes synthesizers 21 and 22 and power amplifiers 23 and 24 as transmission system circuits, and a bandpass filter (BPF) 31 and a reception system circuit. 32a to 32c, preamplifiers 33 and 34a to 34c, and A / D converters 35 and 36a to 36c. The synthesizers 21 and 22 generate continuous wave drive signals given to the transmission elements 11 and 12, respectively, under the control of the system control unit 41 described later. The power amplifiers 23 and 24 amplify the power of the continuous wave drive signals generated by the synthesizers 21 and 22, respectively.

  The bandpass filters 31 and 32a to 32c pass a predetermined frequency band with respect to the detection signals of the detection signals of the ultrasonic waves or the vibro sounds output from the ultrasonic receiver 14 and the vibro sound receivers 15a to 15c, respectively. By such filter processing, an unnecessary band in the detection signal is removed and the SN ratio is increased. The preamplifiers 33 and 34a to 34c preamplify the detection signals subjected to the filter processing. The A / D converters 35 and 36a to 36c convert analog detection signals into digital signals (detection data).

The ultrasonic transmission / reception apparatus includes a processing unit 40 and an image display unit 50.
The processing unit 40 is, for example, a data processing device such as a personal computer, and includes a system control unit 41, a signal processing unit 42 that processes an ultrasonic detection signal, a memory 43, and a correlation unit 45 that processes a vibro sound detection signal. A reflection position estimation calculation unit 46, a signal processing unit 47, a memory 48, and a display image calculation unit 49.

  The system control unit 41 controls the units 41 to 49 of the processing unit 40 and also controls the frequency of the continuous wave drive signal to be generated by the synthesizers 21 and 22 and the generation time thereof. In addition, the system control unit 41 controls the mechanical stage 13 so that a desired region of the subject 100 is scanned by the ultrasonic transmission unit 10.

  The signal processing unit 42 performs signal processing such as logarithmic amplification, detection, TGC (time gain compensation) on the output signal (detection data) of the A / D converter 35. Further, the memory 43 stores the detection data subjected to the signal processing in a predetermined storage area.

  The correlation unit 45 obtains correlation values of a plurality of detection signals from the vibro sound detection signals respectively included in the output signals of the A / D converters 36a to 36c, and the plurality of detection signals so that the correlation values are maximized. Are adjusted and synthesized to generate synthesized data. The reflection position estimation calculation unit 46 performs calculation processing for estimating the reflection position of the received vibro sound based on the information regarding the phase adjustment of the plurality of detection signals obtained by the correlation unit 45.

  The signal processing unit 47 performs signal processing such as logarithmic amplification, detection, and TGC on the combined data output from the correlation unit 45 based on the reflection position obtained by the reflection position estimation calculation unit 46. The memory 48 stores the combined data subjected to the signal processing in a predetermined storage area based on the reflection position obtained by the reflection position estimation calculation unit 46.

The display image calculation unit 49 generates B-mode image data by converting the scanning format of the surface data stored in the memories 43 and 48, respectively.
The image display unit 50 is a display device such as a CRT or LCD, for example, and displays an ultrasonic image based on the B-mode image data generated by the display image calculation unit 49.

Next, an ultrasonic transmission / reception method according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 4 to 7. FIG. 4 is a flowchart showing the ultrasonic transmission / reception method according to the present embodiment.
In step S10 in FIG. 4, as shown in (a) of FIG. 5, the ultrasonic transmitting and receiving apparatus, an ultrasonic wave US1 from the transmission element 11 having a frequency _{f 1,} also ultrasonic has a frequency _{f 2} from the transmission element 12 The sound wave US2 is transmitted so as to form a focal point in the same region on the surface of the bone 110 of the subject 100.

As shown in FIG. 5A, the ultrasonic waves US1 and US2 form a focal point in a predetermined region on the surface of the bone part 110. As a result, a vibro sound having a frequency Δf = f ₁ −f ₂ is generated, and a wave front of the vibro sound having the region P as a sound source propagates concentrically. As shown in FIG. 5B, the vibro sound generated from the region P (secondary sound source P) propagates to the inside of the bone part 110 and is reflected in the region X and the region Y. Thereby, the wave front of the vibro sound which uses the area | region X and the area | region Y as a sound source (tertiary sound source) propagates concentrically.

  In step S <b> 11, as shown in FIG. 5C, the vibro sound receiving units 15 a to 15 c of the ultrasonic transmission / reception apparatus receive the vibro sound that has propagated to the surface of the subject 100. The detection signals output from the vibro sound receiving units 15 a to 15 c are subjected to filter processing and preamplification processing, converted into digital signals, and input to the correlation unit 45 of the processing unit 40.

In FIG. 6, output signals A to C represent the vibro sound signals received by the vibro sound receivers 15 a to 15 c, respectively. Here, the horizontal axis indicates time, and the vertical axis indicates signal strength. The output signals A, detection signals A1 and A2 of the detection signal P _A of vibro sound generated from the secondary sound source P as shown in (c) of FIG. 5, vibro sound reflected by the tertiary source has appeared. Further, in the detection signal B, a detection signal P _B of a vibro sound generated from the secondary sound source P and a plurality of detection signals B1 and B2 of a vibro sound reflected by the tertiary sound source appear. Further, the detection signal C, a detection signal P _C of vibro sound generated from the secondary sound source P, a plurality of detection signals C1 and C2 of the vibro sound reflected by the tertiary source appearing. Note that the vibro sound generated from the secondary sound source P and received directly is higher in intensity than the vibro sound reflected by the tertiary sound source and is received before the vibro sound from the tertiary sound source.

Next, in step S12, the correlation unit 45 obtains correlation values of a plurality of detection signals output from the A / D converters 36a to 36c. Here, generally, the waveform of the sound wave or the ultrasonic wave reflected from the reflector is influenced by the properties of the reflector such as the hardness and elasticity of the reflector. Therefore, a plurality of detection signals having a high correlation value are considered to represent vibro sounds reflected in the same reflection region. Therefore, in the present embodiment, calculation processing is performed to estimate the position of the reflection region and the intensity of the reflected vibro sound using a plurality of detection signals having a high correlation value.
As shown in FIG. 6, in the output signals A to C, the waveforms of the detection signal A2, the detection signal B1, and the detection signal C1 are correlated, and the waveforms of the detection signal A1, the detection signal B2, and the detection signal C2 are correlated. It is considered a thing.

  Next, in step S13, the correlation unit 45 adjusts the phases of the plurality of detection signals so as to maximize the correlation value, and synthesizes them. As a result, combined data of the plurality of detection signals A2, B1, and C1 and combined data of the plurality of detection signals A1, B2, and C2 are generated.

In step S <b> 14, the reflection position estimation calculation unit 46 performs a calculation for estimating the reflection position of the vibro sound represented by the plurality of correlated detection signals based on the detection result of the correlation unit 45. Hereinafter, this calculation method will be described in detail.
First, the reflection position estimation calculation section 46, the detection signal _P A of vibro sound shown in FIG. _6, P B, detection time _t = _{t PA} of _{P C,} t _PB, based on the _{t PC,} the generation position of the vibro sound ( The position of the secondary sound source P is obtained. Position of the secondary sound source P is the detection time _{t PA} and the time difference Δt _AB = _t PA _{-t PB} between detection time _{t PB} detection signal _{P B} of the detection signal _{P A,} and detection time _{t PB} detection signal _{P B} using the time difference Δt _BC = _t PB _{-t PC} between the detection time _{t PC} detection signal _{P C,} a constant propagation speed of the vibro sound within the object can be determined by calculation. Further, the reflection position estimation calculation unit 46 obtains the vibration time t = t ₀ based on the obtained position of the secondary sound source P.

Then, the reflection position estimation calculation unit 46, the arrival time of the three detection signals A2, B1, C1 to correlate, determined based on the occurrence time t = _{t 0} of vibro sound. In the case shown in FIG. 6, the arrival time of the detection signal A2 is Δt _A = t _A2 −t ₀ , the arrival time of the detection signal B1 is Δt _B = t _B1 −t ₀ , and the arrival time of the detection signal C1 is Δt _C = a t _C1 -t _0. Further, the reflection position estimation calculation unit 46 makes the propagation speed of the vibro sound constant in the subject, and determines the arrival times Δt _A , Δt _B , Δt _C of the detected signals as the lengths L _A , L _B , L Convert to _C respectively.

FIG. 7 is a diagram for explaining a method for obtaining the reflection position (tertiary sound source) of the vibro sound. The previously obtained length L _A represents the length from the secondary sound source P to the reception position A via the tertiary sound source X. In other words, the tertiary source X is a secondary sound source P and the receiving position A and 2 fixed point, the sum of the distances from two fixed points is in orbit ellipse EA is L _A. The length L _B represents the length extending from the secondary sound source P to the receiving position B via the tertiary source X, cubic sound X from the secondary sound source P and the receiving position B is 2 fixed points the sum of the distances is in orbit ellipse EB is L _B. Similarly, the length L _C represents the length from the secondary sound source P to the reception position C via the tertiary sound source X, and the tertiary sound source X has the secondary sound source P and the reception position C as two fixed points. Is on the orbit of the ellipse EC whose sum of distances is L _C. Therefore, the position of the tertiary sound source X can be specified by obtaining the intersection of the ellipse EA, the ellipse EB, and the ellipse EC.

Reflection position estimation calculation section 46 uses such a method, the positional relationship between the secondary sound source P and vibro sound receiver 15a~15c obtained above, the length _{L A,} L B, and _{L C} Based on the above, the position of the tertiary sound source X is obtained.
Similarly, the reflection position estimation calculation unit 46 obtains the position of the tertiary sound source Y (FIG. 5) using the correlated detection signals A1, B2, and C2.

In step S15 in FIG. 4, the signal processing unit 47 in FIG. 1 performs signal processing such as logarithmic amplification, detection, and TGC on the combined data generated in the correlation unit 45. At that time, the signal processing unit 47 performs gain adjustment based on the position (depth) of the tertiary sound source obtained by the reflection position estimation calculation unit 46. Further, the combined data subjected to the signal processing is stored in a predetermined storage area of the memory 48 based on the position of the tertiary sound source obtained by the reflection position estimation calculation unit 46.
By performing such processing in steps S12 to S15 for a plurality of correlated detection signals included in the output signals A to C, the memory 48 accumulates synthetic data constituting surface data in a section of the subject. Is done.

  On the other hand, on the outside of the bone part 110 of the subject 100, an ultrasonic echo is generated by the ultrasound US1 and the ultrasound US2 being reflected by the soft tissue 120 in the subject 100. In step S21 of FIG. 4, the ultrasonic receiver 14 receives an ultrasonic echo and outputs a detection signal. This detection signal is subjected to filter processing and pre-amplification processing, converted into a digital signal, and input to the signal processing unit 42.

  Next, in step S22, the signal processing unit 42 performs predetermined signal processing such as detection on the input detection data. The detection data subjected to the signal processing is stored in a predetermined storage area of the memory 43. As a result, sound ray data constituting the surface data of a cross section of the subject is accumulated in the memory 43.

  In step S31, the display image calculation unit 49 generates B-mode image data based on the plane data stored in the memories 43 and 48, respectively. As a result, as shown in FIG. 8A, an ultrasonic image representing the soft tissue 120 outside the bone portion 110 is obtained from the data obtained based on the ultrasonic waves stored in the memory 43. Generated. Further, as shown in FIG. 8B, an ultrasonic image representing the internal tissue of the bone part 110 is generated from the data obtained based on the vibro sound stored in the memory 48.

  In step S32, the display image calculation unit 49 causes the display unit 50 to display the generated B-mode image. At that time, the display image calculation unit 49 may sequentially display the ultrasonic images shown in (a) and (b) of FIG. Alternatively, as shown in FIG. 8C, by synthesizing these ultrasonic images, an ultrasonic image in which both the soft tissue outside the bone part and the internal tissue of the bone part are displayed is displayed. May be.

  As described above, according to the present embodiment, based on the detection signal of the vibro sound received using a plurality of receiving elements, the information about the reflector that reflected the vibro sound is obtained by calculation, and thus transmitted. It is possible to obtain a detailed image of the inside of a bone that is difficult to reach directly with ultrasonic waves. In addition, since information regarding a plurality of reflectors in the subject can be obtained by transmitting ultrasonic waves once, it is possible to efficiently perform ultrasonic imaging.

  In the present embodiment, the vibro sound propagating through the subject is detected using three receiving units, but four or more receiving units may be used. Thereby, the estimation accuracy of the position of the tertiary sound source can be increased.

  In the present embodiment, the ultrasonic echo from the subject is detected using one ultrasonic receiving unit 14, but the ultrasonic echo is detected using a plurality of ultrasonic receiving units arranged at different positions. You may do it. In that case, a plurality of reception system circuits (bandpass filters, preamplifiers, A / D converters) respectively corresponding to the plurality of ultrasonic reception units are provided, and those reception system circuits are connected to the front stage of the signal processing unit 42. It is desirable to provide a processing unit that performs reception focus processing by adding the output detection data with a predetermined delay.

Next, an ultrasonic transmission / reception apparatus according to the second embodiment of the present invention will be described.
FIG. 9 is a block diagram illustrating a configuration of the ultrasonic transmission / reception apparatus according to the present embodiment. In the ultrasonic transmission / reception apparatus illustrated in FIG. 9, the plurality of vibro sound reception units 15 a to 15 c are mechanically coupled to the ultrasonic transmission unit 10. About another structure, it is the same as that of the ultrasonic transmitter-receiver shown in FIG.

  In the present embodiment, when the ultrasonic transmitter 10 is moved by driving the mechanical stage 13, the vibro sound receivers 15a to 15c are also moved together. Thereby, as shown in FIG. 5, the positional relationship between the position of the secondary sound source P of the vibro sound generated based on the two ultrasonic waves transmitted from the ultrasonic transmitter 10 and the vibro sound receivers 15a to 15c. Are always constant. Therefore, it is not necessary to obtain the position of the secondary sound source P, and the arithmetic processing can be simplified.

Next, an ultrasonic transmission / reception apparatus according to the third embodiment of the present invention will be described.
FIG. 10 is a block diagram illustrating a configuration of the ultrasonic transmission / reception apparatus according to the present embodiment. The ultrasonic transmission / reception apparatus includes preamplifiers 37a to 37c, phase adjustment units 38a to 38c, and subtraction processing units 39a to 39c, respectively, upstream of the A / D converters 36a to 36c. The ultrasonic transmission / reception apparatus includes a receiving unit 16 whose direction is adjusted so as to collect a sound wave and an ultrasonic wave outside the subject, a preamplifier 17 that amplifies an output signal of the receiving unit 16, and a phase adjusting unit. 18. Similarly to the vibro sound receiving units 15a to 15c, the receiving unit 16 includes a receiving element having a substantially constant reception sensitivity in a frequency band of several hundreds of Hz to several hundreds of kHz, for example, and a sound wave that propagates in the air. And receive ultrasound. About another structure, it is the same as that of the ultrasonic transmitter-receiver shown in FIG.

Here, the vibro sound received in the present embodiment has a frequency in the audible range to about several hundred kHz. Naturally, the ultrasonic waves having a relatively low frequency of about 40 kHz to 120 kHz can propagate in the air, unlike the ultrasonic waves in the megahertz band used for normal ultrasonic imaging. Therefore, the receiving element that receives the vibro sound receives not only the vibro sound propagating through the subject but also the sound wave and the ultrasonic wave propagating in the air, so that the SN ratio of the detection signal may be significantly reduced. .
Therefore, in the present embodiment, noise that propagates in the air is detected by the receiving unit 16, and a noise component is acquired by adjusting the gain and phase of the detection signal. Then, the SN ratio of the vibro sound detection signal is improved by subtracting the noise component from the preamplified and phase-adjusted vibro sound detection signal.

  In the present embodiment, before generating composite data based on a plurality of vibro sound detection signals, a process of subtracting noise components from each vibro sound detection signal is performed. A process of subtracting the noise component may be performed. Further, the process of subtracting the noise component may be performed analogly as shown in FIG. 10 or may be performed digitally.

In the first to third embodiments of the present invention described above, a vibro sound is generated by transmitting two ultrasonic waves having different frequencies. However, the method for generating the vibro sound is not limited to this method. For example, as disclosed in US Pat. No. 5,921,928, a method of modulating the amplitude of single-frequency ultrasonic waves, a method of intermittently transmitting amplitude-modulated single-frequency ultrasonic waves, As disclosed in US Pat. No. 6,408,679, there is a method of causing a nonlinear phenomenon by pumping low-frequency ultrasonic waves and applying stimulation by high-frequency ultrasonic waves.
Further, when receiving a vibro sound, a Doppler scan may be performed as disclosed in FIG. 5 of US Pat. No. 5,903,516.

1 is a block diagram illustrating a configuration of an ultrasonic transmission / reception device according to a first embodiment of the present invention. It is a figure which shows a mode that a vibro sound is generated. It is a figure which shows the frequency characteristic of a transmitting element and a receiving element. It is a flowchart which shows the ultrasonic transmission / reception method which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the ultrasonic transmission / reception method which concerns on the 1st Embodiment of this invention. It is a figure showing the output signal of the vibro sound receiving part shown in FIG. It is a figure for demonstrating the method of calculating | requiring the position of a tertiary sound source. It is a figure which shows the ultrasonic image imaged with the ultrasonic transmitter / receiver which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the ultrasonic transmitter / receiver which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the ultrasonic transmitter / receiver which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ultrasonic transmitter 11, 12 Transmitting element 13 Mechanical stage 14 Ultrasonic receiver 15a-15c Vibro sound receiver 16 Receiver 17, 33, 34a-34c, 37a-37c Preamplifier 18 Phase adjuster 21, 22 Synthesizer 23, 24 Power amplifier 31, 32a-32c Band pass filter 35, 36a-36c A / D converter 38a-38c Phase adjustment unit 39a-39c Subtraction processing unit 40 Processing unit 41 System control unit 42, 47 Signal processing unit 43, 48 Memory 45 Correlator 46 Reflection position estimation calculator 49 Display image calculator 50 Image display unit 100 Subject 101 Object 110 Bone 120 Soft tissue

Claims (9)

First transmission means and second transmission means for respectively transmitting ultrasonic waves to a subject according to a plurality of applied drive signals;
Drive signal generation means for generating a plurality of drive signals respectively applied to the first and second transmission means;
A first ultrasonic wave is transmitted from the first transmission unit toward the region within the subject, and a second frequency different from the first ultrasonic wave is transmitted from the second transmission unit toward the region. Control means for controlling the drive signal generating means so as to transmit ultrasonic waves;
A third ultrasonic wave or sound wave generated based on the first and second ultrasonic waves in the subject and having a frequency difference between the first ultrasonic frequency and the second ultrasonic frequency is received. A plurality of receiving means for outputting a plurality of detection signals respectively;
An arithmetic unit that generates information on a reflected region in the subject that reflects the received third ultrasonic wave or sound wave by performing arithmetic processing on the plurality of detection signals output from the plurality of receiving units, respectively;
An ultrasonic transmission / reception apparatus comprising:   The calculation means obtains correlation values of a plurality of detection signals respectively output from the plurality of receiving means, and adjusts and synthesizes the phases of the plurality of detection signals so that the correlation values are maximized. Ultrasonic transmitter / receiver.   Information on the position of the reflection region in the subject that has reflected the received third ultrasonic wave or sound wave based on the information on the phase adjustment of the plurality of detection signals when the correlation value is maximized. The ultrasonic transmission / reception apparatus according to claim 2, wherein:   The ultrasonic transmission / reception apparatus according to claim 3, further comprising image generation means for generating image data based on the combined detection signal obtained by the calculation means and information on the position of the reflection region in the subject. First transmission means and second transmission means for respectively transmitting ultrasonic waves to a subject according to a plurality of applied drive signals;
Drive signal generation means for generating a plurality of drive signals respectively applied to the first and second transmission means;
A first ultrasonic wave is transmitted from the first transmission unit toward the region within the subject, and a second frequency different from the first ultrasonic wave is transmitted from the second transmission unit toward the region. Control means for controlling the drive signal generating means so as to transmit ultrasonic waves;
A third ultrasonic wave or sound wave generated based on the first and second ultrasonic waves in the subject and having a frequency difference between the first ultrasonic frequency and the second ultrasonic frequency is received. And at least one first receiving means for outputting at least one first detection signal;
Second receiving means for receiving ultrasonic waves or sound waves propagating from outside the subject and outputting a second detection signal;
Processing means for generating at least one third detection signal by taking a difference between the at least one first detection signal and the second detection signal with adjusted gain and / or phase;
A calculation means for generating information on a reflection region in the subject that reflects the received third ultrasonic wave or sound wave by performing a calculation process on the at least one third detection signal;
An ultrasonic transmission / reception apparatus comprising: Transmitting a first ultrasonic wave and a second ultrasonic wave having a frequency different from that of the first ultrasonic wave toward a region in the subject;
A third ultrasonic wave or sound wave generated based on the first and second ultrasonic waves in the subject and having a frequency difference between the frequency of the first ultrasonic wave and the frequency of the second ultrasonic wave; Receiving using a plurality of receiving means and outputting a plurality of detection signals, respectively (b);
Step (c) of generating information related to the reflection region in the subject that reflects the received third ultrasonic wave or sound wave by performing arithmetic processing on the plurality of detection signals output from the plurality of receiving units, respectively. When,
An ultrasonic transmission / reception method comprising:   Step (c) includes obtaining correlation values of a plurality of detection signals respectively output from the plurality of receiving means, and adjusting and synthesizing the phases of the plurality of detection signals so that the correlation values are maximized. The ultrasonic transmission / reception method according to claim 6.   Step (c) relates to the position of the reflection region in the subject that has reflected the received third ultrasonic wave or sound wave based on information relating to phase adjustment of the plurality of detection signals when the correlation value is maximized. The ultrasonic transmission / reception apparatus according to claim 7, comprising obtaining information. Transmitting a first ultrasonic wave and a second ultrasonic wave having a frequency different from that of the first ultrasonic wave toward a region in the subject;
A third ultrasonic wave or sound wave generated based on the first and second ultrasonic waves in the subject and having a frequency difference between the first ultrasonic frequency and the second ultrasonic frequency is received. And outputting at least one first detection signal;
Receiving ultrasonic waves or sound waves propagating from outside the subject and outputting a second detection signal; and
Generating at least one third detection signal by taking a difference between the at least one first detection signal and the second detection signal with adjusted gain and / or phase;
Generating information related to the reflection region in the subject that reflects the received third ultrasonic wave or sound wave by performing arithmetic processing on the at least one third detection signal;
An ultrasonic transmission / reception method comprising:

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