JP2010213903A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus constructing a high-definition ultrasonic image by preventing the occurrence of output ringing of a resonance circuit in the ultrasonic diagnostic apparatus amplifying amplitude by resonating signals of specific frequency using the resonance circuit. <P>SOLUTION: A transmitted electric signal is generated from a first waveform 40 which is an electric signal of rectangular wave shape of at least one cycle, and a second waveform which is an electric signal of one cycle portion different in phase by 180°. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus that transmits an ultrasonic signal into a subject and generates an ultrasonic image inside the subject based on a reflected wave.

  Ultrasound generally refers to sound waves of 16000 Hz or higher and can be examined non-destructively, harmlessly and in real time, and thus is applied to various fields such as defect inspection and disease diagnosis. For example, an ultrasound that scans the inside of the subject with ultrasound and images the internal state of the subject based on a reception signal generated from the reflected wave (echo) of the ultrasound coming from inside the subject. There is a diagnostic device. This ultrasonic diagnostic apparatus is smaller and less expensive for medical use than other medical imaging apparatuses, has no radiation exposure such as X-rays, is highly safe, and has a blood flow utilizing the Doppler effect. It has various features such as display capability. For this reason, an ultrasonic diagnostic apparatus includes a circulatory system (for example, coronary artery of the heart), a digestive system (for example, gastrointestinal), an internal system (for example, liver, pancreas and spleen), and a urinary system (for example, kidney and bladder). Widely used in obstetrics and gynecology.

  An ultrasonic probe that transmits and receives an ultrasonic wave (ultrasonic signal) to a subject is used in the ultrasonic diagnostic apparatus. An ultrasonic probe uses a piezoelectric phenomenon to generate an ultrasonic wave (ultrasonic wave signal) by mechanical vibration based on an electric signal transmitted, and an ultrasonic wave generated due to mismatch of acoustic impedance inside a subject. A plurality of piezoelectric elements that receive a reflected wave of (ultrasonic signal) and generate a reception electric signal are provided, and the plurality of piezoelectric elements are arranged in a two-dimensional array, for example (for example, Patent Document 1). reference).

  Further, in recent years, harmonic imaging (Harmonic) that forms an image of the internal state in the subject not by the frequency (fundamental frequency) component of the ultrasound transmitted from the ultrasound probe into the subject but by its harmonic components. Imaging technology is being researched and developed. In the harmonic imaging technology, the side lobe level is small compared to the level of the fundamental frequency component, the S / N ratio (Signal to Noise ratio) is improved and the contrast is improved, and the beam width is narrowed by increasing the frequency. The lateral resolution is improved, the sound pressure is small and the fluctuation in sound pressure is small at short distances, and thus multiple reflections are suppressed. Compared to the case, it has various advantages such as a large depth speed.

  The detection of the harmonic component is performed by passing an electrical signal converted from the ultrasonic wave by an ultrasonic probe through a high-pass filter or the like that removes the fundamental frequency. However, since the harmonic component is considerably smaller than the fundamental component, it is necessary to employ an expensive and large-scale high-pass filter to obtain a signal level sufficient to construct a high-definition ultrasonic image. As a result, the cost and scale of the apparatus are increased.

  Proposals have been made to solve this problem. For example, there is a technique in which an electric signal converted from an ultrasonic wave is passed through a resonance circuit and only a harmonic component is amplified by resonance (see, for example, Patent Document 2).

JP 2004-088056 A JP 2007-185525 A

  The technique described in Patent Document 2 amplifies the amplitude by resonating a signal having a specific frequency using a resonance circuit, and therefore ringing corresponding to the characteristics of the resonance circuit occurs in the output of the resonance circuit. Since the electrical signals transmitted to the ultrasound probe are a set of electrical signals with a predetermined time interval, ringing that occurs between the electrical signals is superimposed on the electrical signal that is later in time. A malfunction occurs. The electrical signal on which the ringing is superimposed generates noise in the ultrasonic image, and thus prevents the construction of a high-definition ultrasonic image.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of preventing generation of ringing of an output of a resonance circuit and constructing a high-definition ultrasonic image.

  The above object is achieved by the invention described below.

1. An inorganic piezoelectric element array having a plurality of piezoelectric elements, the main component of which is an inorganic piezoelectric material, which converts a transmission electrical signal into a first ultrasonic signal and transmits the first ultrasonic signal;
A first electric signal waveform having a predetermined frequency and a second electric signal waveform having a frequency substantially the same as that of the first electric signal waveform and having a phase difference of about 180 degrees are successively generated in this order. An electrical circuit that outputs a transmission electrical signal, and a transmission unit that applies the transmission electrical signal to the piezoelectric element;
A plurality of piezoelectric elements, each of which has an organic piezoelectric material as a main component, receives a harmonic component of the second ultrasonic signal generated by reflecting the first ultrasonic signal in the subject, and converts it into a received electric signal. An organic piezoelectric element array comprising:
A receiving unit including a resonance circuit that inputs the received electrical signal and uses a harmonic component of the second ultrasonic signal as a resonance frequency;
An image processing unit 14 for generating an image of an internal state in the subject from the output of the receiving unit;
An ultrasonic diagnostic apparatus comprising:

  2. 2. The ultrasonic diagnostic apparatus according to 1 above, wherein the organic piezoelectric material is a polymer of vinylidene fluoride or a copolymer of vinylidene fluoride and trifluoroethylene.

  3. 2. The ultrasonic diagnostic apparatus according to 1 above, wherein the inorganic piezoelectric material is lead zirconate titanate.

  4). The inorganic piezoelectric element array is laminated on the organic piezoelectric element array in a direction in which the inorganic piezoelectric element array transmits a first ultrasonic signal to the subject. The ultrasonic diagnostic apparatus of Claim 1.

  It is possible to provide an ultrasonic diagnostic apparatus capable of preventing ringing of the output of the resonance circuit in the ultrasonic probe and constructing a high-definition ultrasonic image.

1 is a schematic diagram showing an external configuration of an ultrasonic diagnostic apparatus S according to the present embodiment. 1 is a block diagram showing an electrical configuration of an ultrasound diagnostic apparatus S according to the present embodiment. 1 is a schematic diagram showing a configuration of an ultrasound probe 2 in an ultrasound diagnostic apparatus S according to the present embodiment. FIG. 4A is a diagram illustrating an example of a waveform of a transmission electric signal generated by the transmission unit 12, and FIG. 4A is an example of a transmission electric signal generated by the transmission unit 12 of the conventional ultrasonic diagnostic apparatus. (B) is an example of the transmission electric signal in this embodiment. It is a schematic diagram which shows an example of the circuit structure of the transmission part 12 and the receiving part 13 which concern on this embodiment. It is a figure explaining the circuit structure and transmission electric waveform of the ultrasound probe 2 which concern on this embodiment, FIG. 6 (a) is a schematic diagram which shows an example of a circuit structure, FIG.6 (b) is FIG. It is a schematic diagram which shows one example of the transmission electrical waveform applied to a piezoelectric element. FIG. 5 is a schematic diagram of a waveform after a received electrical signal according to the present embodiment has passed through a resonance circuit 47. It is an example of the amplifier circuit which concerns on this embodiment. It is an example of the transmission electric signal which concerns on this embodiment.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments described below. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted.

  Hereinafter, each configuration and operation of the ultrasonic diagnostic apparatus and the ultrasonic probe will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic diagram showing an external configuration of an ultrasonic diagnostic apparatus. FIG. 2 is a block diagram showing an electrical configuration of the ultrasonic diagnostic apparatus. FIG. 3 is a schematic diagram showing the configuration of the ultrasonic probe in the ultrasonic diagnostic apparatus.

  As shown in FIG. 1, the ultrasonic diagnostic apparatus S transmits ultrasonic waves (first ultrasonic signals) to a subject H such as a living body (not shown) and reflects the ultrasonic waves reflected by the subject H. An ultrasonic probe 2 that receives a wave (echo, second ultrasonic signal), and is connected to the ultrasonic probe 2 via a cable 3 and to the ultrasonic probe 2 via a cable 3. The ultrasonic probe 2 is caused to transmit an ultrasonic wave to the subject H by transmitting the transmission signal, and the second ultrasonic signal from within the subject H received by the ultrasonic probe 2 is also transmitted. Accordingly, the ultrasonic diagnostic apparatus main body 1 is configured to image the internal state in the subject H as an ultrasonic image based on the reception signal generated by the ultrasonic probe 2.

For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11 for inputting a command for instructing diagnosis and data such as personal information of the subject H, and a cable to the ultrasonic probe 2. A transmission unit 12 that drives the ultrasonic probe 2 to generate ultrasonic waves by supplying a transmission signal of an electrical signal via 3, and receives a reception signal from the ultrasonic probe 2 via the cable 3. Receiving unit 13,
An image processing unit 14 that generates an image (ultrasonic image) of the internal state in the subject H based on the harmonic component of the received signal;
A storage unit 17 for storing the results obtained by the image processing unit 14, a display unit 15 for displaying an image of the internal state in the subject H generated by the image processing unit 14, the operation input unit 11, and transmission A control unit 16 that performs overall control of the ultrasound diagnostic apparatus S by controlling the unit 12, the reception unit 13, the image processing unit 14, the display unit 15, and the storage unit 17 according to the function. The

  An example of the ultrasonic probe 2 will be described with reference to FIG. The ultrasonic probe 2 includes an organic piezoelectric element array 5 and an inorganic piezoelectric element array 4.

  The inorganic piezoelectric element array 4 includes an inorganic piezoelectric element, the organic piezoelectric element array 5 includes an organic piezoelectric element, the inorganic piezoelectric element includes an inorganic piezoelectric material as a main component, and the organic piezoelectric element includes an organic piezoelectric material as a main component. Signals can be mutually converted between the received signal and the ultrasonic signal by using each piezoelectric phenomenon.

  The ultrasonic probe 2 has a flat acoustic braking member 23, an acoustic matching layer 31 stacked on the acoustic braking member 23, the inorganic piezoelectric element array 4, and an acoustic matching toward the subject H direction. The layer 26, the organic piezoelectric element array 5, and the acoustic matching layer 27 stacked on the organic piezoelectric element array 5 are included. The inorganic piezoelectric element array 4 is a piezoelectric element array that transmits an ultrasonic signal (also referred to as a first ultrasonic signal) toward the subject H, and the organic piezoelectric element array 5 is generated by being reflected from the subject H. The piezoelectric element array receives an ultrasonic signal (also referred to as a second ultrasonic signal). In this way, by laminating the transmitting and receiving piezoelectric element arrays in the direction of the subject H, the reflected ultrasonic signals can be efficiently received, and the ultrasonic probe 2 Contributes to small size.

  The inorganic piezoelectric element array 4 includes a plurality of inorganic piezoelectric elements 22, an acoustic separation unit 24 that is manufactured by filling a gap between the inorganic piezoelectric elements 22 with an acoustic separation material, and a common ground layer stacked on the inorganic piezoelectric elements 22. And an electrode 25.

  In addition, although not shown, a conductive pad for receiving an electric signal from the outside is provided below the acoustic braking member 23, and the conductive pad and the electrode of the inorganic piezoelectric element 22 are connected by a signal line.

  The acoustic braking member 23 is made of a material that absorbs ultrasonic waves, and absorbs ultrasonic waves radiated from the plurality of inorganic piezoelectric elements 22 toward the acoustic braking member 23.

  The acoustic matching layer 31 has an acoustic impedance that is intermediate between the acoustic impedances of the acoustic braking member 23 and the inorganic piezoelectric element 22, and matches the acoustic impedance of the acoustic braking member 23 and the inorganic piezoelectric element 22.

  Each inorganic piezoelectric element 22 includes electrodes 102 and 103 on opposite surfaces of the piezoelectric element 101 made of an inorganic piezoelectric material. The plurality of inorganic piezoelectric elements 22 are two-dimensionally arranged in a plan view with a predetermined interval therebetween, and are disposed on the acoustic braking member 23.

  The plurality of inorganic piezoelectric elements 22 are configured to transmit ultrasonic waves. More specifically, an electrical signal is input to the plurality of inorganic piezoelectric elements 22 from the transmitter 12 via the cable 3, the conductive pad, and the signal line. The electric signal is input between the electrode 102 and the electrode 103 of the inorganic piezoelectric element 22. The plurality of inorganic piezoelectric elements 22 transmit the first ultrasonic signal by converting the electrical signal into an ultrasonic signal.

  The acoustic separator 24 is made of a low acoustic impedance resin having a value that differs greatly from the acoustic impedance of the inorganic piezoelectric element 22. The acoustic separator 24 functions as an acoustic separator due to the great difference in acoustic impedance, and the plurality of inorganic piezoelectric elements 22. Has a function of reducing mutual interference. The acoustic separator 24 can reduce crosstalk between the inorganic piezoelectric elements 22.

  The common ground electrode 25 is made of a conductive material, is grounded by an unillustrated wiring, and is laminated in a straight line across the plurality of inorganic piezoelectric elements 22, whereby the common ground electrode 25 is formed in the inorganic piezoelectric elements 22. Each electrode 103 is electrically grounded.

  The acoustic matching layer 26 has an acoustic impedance intermediate between the acoustic impedances of the inorganic piezoelectric element array 4 and the organic piezoelectric element array 5, and matches the acoustic impedance of the inorganic piezoelectric element array 4 and the organic piezoelectric element array 5.

  The acoustic matching layer 27 is a member that matches the acoustic impedance of the organic piezoelectric element array 5 and the acoustic impedance of the subject H. The acoustic matching layer 27 has a shape that bulges in an arc shape, and has a function of an acoustic lens that converges ultrasonic waves transmitted toward the subject H.

  The organic piezoelectric element array 5 includes a piezoelectric element 105 made of a flat organic piezoelectric material having a predetermined thickness, a plurality of mutually separated electrodes 106 formed on one main surface of the piezoelectric element 105, and the piezoelectric element. This is a sheet-like piezoelectric element configured to include the electrode 107 formed uniformly over substantially the entire other surface of the element 105.

  By forming the plurality of electrodes 106 on one main surface of the piezoelectric element 105, the organic piezoelectric element array 5 includes a piezoelectric element including one electrode 107, the piezoelectric element 105, and the electrode 106 in a two-dimensional shape. Each piezoelectric element operates individually.

  The plurality of piezoelectric elements in the organic piezoelectric element array 5 do not need to be individually separated like the inorganic piezoelectric elements 22 in order to function individually, and can be configured as an integral sheet.

  In FIG. 3, a portion formed by the electrode 107, the piezoelectric element 105, and the electrode 106, such as a portion indicated by 21, can be regarded as one organic piezoelectric element, that is, the organic piezoelectric element 21.

  The organic piezoelectric element 21 is a receiving piezoelectric element that receives an ultrasonic signal of a reflected wave, and converts the received ultrasonic signal into an electric signal. This electrical signal is output from the electrode 106 and the electrode 107 in the organic piezoelectric element 21. This electrical signal is output to the receiver 13 via the cable 3.

As the inorganic piezoelectric material, for example, a sintered body such as PZT (lead zirconate titanate) or the like, a crystal, a single crystal such as LiNbO ₃ , LiTaO ₃ , or KNbO ₃ , or a thin film such as ZnO or AlN is used. be able to. By using the inorganic piezoelectric material, the first ultrasonic signal having a narrow band can be transmitted. These inorganic piezoelectric materials have characteristics such as high elastic stiffness, high mechanical loss coefficient, high density and high dielectric constant. In particular, by using PZT, it is possible to transmit (receive) an ultrasonic signal with high sensitivity and high resolution.

  As the organic piezoelectric material, for example, a polymer of vinylidene fluoride or a copolymer of vinylidene fluoride and trifluoroethylene can be used. In the case of a copolymer of vinylidene fluoride and trifluoroethylene, since the electromechanical coupling constant (piezoelectric effect) in the thickness direction varies depending on the copolymerization ratio, for example, the former copolymerization ratio is preferably 60 to 99 mol%. The optimum value varies depending on the method of using an organic binder used when the inorganic piezoelectric element and the organic piezoelectric element are stacked. The most preferable range of the former copolymerization ratio is 85 to 99 mol%. A polymer in which 85 to 99 mol% of vinylidene fluoride and 1 to 15 mol% of perfluoroalkyl vinyl ether, perfluoroalkoxyethylene, perfluorohexaethylene, etc. are used as an inorganic piezoelectric element for transmission and an organic piezoelectric element for reception. In this combination, it is possible to suppress the fundamental frequency wave in transmission and increase the sensitivity of harmonic reception.

  The copolymer of vinylidene fluoride and trifluoroethylene is relatively excellent in processability such as thinning and large area, can be made in any shape and form, has low elastic modulus, and low dielectric constant Therefore, when used as a piezoelectric element that receives an ultrasonic signal, it has a feature that enables highly sensitive detection. Further, these organic piezoelectric materials are suitable as piezoelectric materials in harmonic imaging technology that requires high-frequency characteristics and broadband characteristics.

  In addition, for example, polyurea vinylidene, a polyurea resin composed of a ureine group formed from a diisocyanate compound such as 4,4′-diphenylmethane diisocyanate (MDI) and a diamine compound such as 4,4′-diaminodiphenylmethane (MDA). Organic piezoelectric materials such as these are also suitable.

  Next, the circuit configuration of the transmitter 12, the receiver 13, and the ultrasound probe 2 in the ultrasound diagnostic apparatus body 1 and the first ultrasound signal transmitted to the subject will be described.

  FIG. 4 is a diagram illustrating an example of a waveform of a transmission electrical signal generated by the transmission unit 12. FIG. 5 is a schematic diagram illustrating an example of a circuit configuration of the transmission unit 12 and the reception unit 13. FIG. 6 is a schematic diagram showing an example of the circuit configuration of the ultrasonic probe 2 and an example of the waveform of a transmission electric signal applied to the piezoelectric element.

  First, the transmission electric signal generated by the transmission unit 12 will be described. FIG. 4A is an example of a transmission electric signal generated by the transmission unit 12 of the conventional ultrasonic diagnostic apparatus. FIG. 4B is an example of a transmission electrical signal in the present embodiment.

  A conventional transmission electric signal is a rectangular wave electric signal having at least one cycle (also referred to as a first waveform 40). On the other hand, as shown in FIG. 4B, the transmission electric signal in the present embodiment is a waveform in which an additional portion is added after a minute delay dt has elapsed in the first waveform 40 in time. The additional portion is a waveform for one period (also referred to as a second waveform) having substantially the same amplitude as the rectangular wave forming the first waveform 40 and having a phase approximately 180 degrees different. The minute delay dt is, for example, a value of 1/10 or less with respect to the time of one cycle of the first waveform and the second waveform.

  Next, the circuit configuration of the transmission unit 12 that generates the second waveform and the reception unit 13 will be described. In FIG. 5, the transmitter 1 and the receiver 13 are each surrounded by a one-dotted line. The transmission unit 12 and the reception unit 13 are connected to a cable 3 that connects the ultrasonic diagnostic apparatus main body 1 and the ultrasonic probe 2. In sharing one cable 3, when the cable 3 is used for transmission, the control unit 16 turns on the switch SW1 of the transmission unit 12 and turns off the switch SW2 of the reception unit 13. Conversely, when the cable 3 is used for reception, the control unit 16 turns off the switch SW1 of the transmission unit 12 and turns on the switch SW2 of the reception unit 13.

  The transmission electrical signal transmitted from the transmitter 12 to the ultrasound probe 2 is generated using, for example, two CMOS (Complementary Metal Oxide Semiconductor) 44 and 45 and a CMOS driver 43 that drives the CMOS. Specifically, a circuit arrangement as shown in FIG. 5 is adopted using a positive constant voltage power source Vc1 and a negative constant voltage source Vc2.

  The operation will be described below. When the control unit 16 controls the CMOS driver 43 and the CMOS driver 43 is driven to turn on the CMOS 44 and turn off the CMOS 45, the potential at the point 46 connected to the cable 3 via the switch SW1 is the same as the constant voltage source Vc1. For example, the positive voltage value V0 in FIG. 4B is obtained. Next, when the control unit 16 controls the CMOS driver 43 to turn off the CMOS 44 and turn on the CMOS 45 by driving the CMOS driver 43, the potential at the point 46 becomes the same potential as the constant voltage source Vc2, for example, FIG. The negative voltage value −V0 in (b). By repeating the above operation, the control unit 16 can obtain the first waveform 40 which is a transmission electric signal having a rectangular continuous waveform shown in FIG. Next, the control unit 16 reads a time measurement value of a clock (not shown) provided in the control unit 16, and has the same amplitude as the second waveform, that is, the rectangle forming the first waveform 40 after a predetermined time dt has elapsed. Similarly, the waveform for one period whose phase is different by 180 degrees is generated by controlling the CMOS driver 43 in the same manner as described above. Thus, the transmission electric signal 41 composed of the first waveform 40 and the second waveform 42 is transmitted to the ultrasonic probe 2 via the switch SW1 and the cable 3. As shown in FIG. 6A, the ultrasonic probe 2 includes an inorganic piezoelectric element 22 that transmits a transmission electric signal 41, an inductance L and a switch SW3 line on the substrate 50, an organic piezoelectric element 21 and a switch SW4. Are connected to one cable 3. The transmission electrical signal 41 transmitted from the ultrasonic diagnostic apparatus main body 1 is transmitted to the inductance L and the inorganic piezoelectric element 22 after the switch SW3 is turned on and the switch SW4 is turned off under the control of the control unit 16. The transmission electrical signal 41 passes through the inductance L, is converted into a sinusoidal continuous wave as shown in FIG. 6B, and is applied to the inorganic piezoelectric element 22.

  The inorganic piezoelectric element 22 receives a sinusoidal voltage application, expands and contracts in the thickness direction, is driven to vibrate ultrasonically, and generates and transmits a first ultrasonic signal having a sinusoidal intensity amplitude. The first ultrasonic signal propagates through the organic piezoelectric element array 5 and the like and is irradiated in the direction of the subject H.

  The first ultrasonic signal includes not only a frequency (fundamental fundamental frequency) component included in the transmission electrical signal 41 from the transmission unit but also a harmonic component that is an integral multiple of the fundamental frequency. For example, second harmonic components such as twice, three times, and four times the fundamental frequency, third harmonic components, and fourth harmonic components are also included. This depends on the presence of harmonic components in the electrical signal itself from the transmitter 12 and the response characteristics of the piezoelectric element.

  The first ultrasonic signal transmitted to the subject H is reflected at one or a plurality of boundary surfaces having different acoustic impedances inside the subject H, and becomes a second ultrasonic signal that is a reflected wave of the ultrasonic wave. .

  The second ultrasonic signal includes not only the frequency (fundamental fundamental frequency) component of the transmitted first ultrasonic signal but also a higher harmonic component that is an integral multiple of the fundamental frequency. The second ultrasonic signal is received by the ultrasonic probe 2. More specifically, the second ultrasonic signal is received by the organic piezoelectric element 21 that is a receiving piezoelectric element via the acoustic matching layer 27, and mechanical vibration is converted into a received electrical signal by the organic piezoelectric element 21. To be taken out. The extracted received electrical signal is received by the receiving unit 13 controlled by the control unit 16 through the cable 3 via the switch SW4 controlled by the control unit 16 and turned on. At this time, the switch SW3 is turned off by the control of the control unit 16. In the reception unit 13, the received electrical signal is input to the resonance circuit 47 through the switch SW <b> 2 that is turned on under the control of the control unit 16. At this time, the switch SW1 is turned off by the control of the control unit 16. In the received electrical signal, in addition to the fundamental frequency contained in the transmitted electrical signal 41, the harmonic component contained in the second ultrasonic signal in the subject H includes, for example, an electrical signal of the third harmonic component. In the ultrasonic diagnostic apparatus S according to the present embodiment, a high-definition ultrasonic image is obtained by analyzing the third harmonic component in the second ultrasonic signal that is a reflected wave from the subject H. For this purpose, the resonance frequency of the resonance circuit 47 is adjusted to the frequency of the third harmonic. For example, when a known LC resonance circuit as shown in FIG. 5 is adopted, the resonance frequency is selected so that the values of the inductance L and the capacitor C resonate with the frequency of the third harmonic. By doing so, it is possible to resonate the third harmonic and transmit only the third harmonic to the next stage and attenuate the fundamental frequency and the second harmonic. Further, the third harmonic is further amplified by being incident on the amplifier AMP1.

  The signal waveform of the received electrical signal having the third harmonic frequency among the received electrical signals that have passed through the resonance circuit 47 will be described with reference to FIG. FIG. 7 is a schematic diagram of the waveform after the received electrical signal has passed through the resonance circuit 47.

  7A to 7E, the horizontal axis represents time, and the vertical axis represents the amplitude of the received electrical signal. FIG. 7A shows a signal obtained by passing the transmission electric signal 41 applied to the inorganic piezoelectric element, which is a transmission piezoelectric element, through the inductance L. FIG. As described above, the transmission electric signal 41 is divided into the first waveform 40 represented by a solid line and the second waveform 42 represented by a dotted line.

  A waveform in which only the first waveform 40 passes through the resonance circuit 47 is shown in FIG. By passing through the resonance circuit 47, ringing R1 is generated. The ringing R1 has a sine wave shape in phase with the sine wave forming the first waveform 40. In particular, the ringing R11, which is the first waveform of ringing, has a relationship of canceling out the sine wave forming the first waveform 40 and the second waveform having a phase difference of 180 degrees. The ringing R1 attenuates while gradually decreasing the amplitude.

  A waveform in which only the second waveform 42 passes through the resonance circuit 47 is shown in FIG. By passing through the resonance circuit 47, ringing R2 is generated. As described above, the second waveform 42 has a relationship of canceling out with the ringing R11. Also, the ringing R2 has a relationship of canceling each other because the phase of the ringing R1 shown in FIG. 7B is 180 ° out of phase with the ringing after the ringing R11.

  FIG. 7D shows a waveform obtained by superimposing a waveform in which only the first waveform 40 has passed through the resonance circuit 47 and a waveform in which only the second waveform 42 has passed through the resonance circuit 47. When these waveforms are added, the ringing R1 of the first waveform is attenuated as shown in FIG. In this way, the ringing R1 of the first waveform and the ringing R2 of the second waveform and the second waveform are canceled out, and the ringing of the output of the resonance circuit 47 can be made extremely small. Accordingly, after the transmission unit 12 transmits the transmission electrical signal, the next transmission electrical signal can be transmitted immediately and noise due to ringing is not superimposed on the next transmission electrical signal. An image can be constructed.

  The ultrasound probe 2 may be used in contact with the surface of the subject H, or may be inserted into the subject H, for example, inserted into a body cavity of a living body. Good.

  The output of the receiving unit 13 that has extracted high-order harmonic components in this way is sent to the image processing unit 14. The image processing unit 14 is an image of an internal state in the subject H (ultrasound image) based on the reception signal received by the reception unit 13 based on the reception signal received by the reception unit 13 from the time from transmission to reception, the reception intensity, and the like. The display unit 15 displays an image of the internal state in the subject H generated by the image processing unit 14 under the control of the control unit 16.

  Since the ultrasonic probe 2 and the ultrasonic diagnostic apparatus S in the present embodiment receive the harmonics of the fundamental wave as described above, it is possible to form an ultrasonic image by so-called harmonic imaging technology. For this reason, the ultrasonic probe 2 and the ultrasonic diagnostic apparatus S in the present embodiment can provide a higher-accuracy ultrasonic image. And since the 3rd harmonic with comparatively big power is received, provision of a clearer ultrasonic image is attained.

  In addition, the circuit which produces | generates the transmission electric signal which the transmission part 12 transmits to the ultrasound probe 2 may be a circuit as shown to Fig.8 (a), (b). FIG. 8 shows an example of an amplifier circuit. This will be described below. The amplifier circuit in FIG. 8A is a circuit in which transistors tr1 and tr2 are arranged at the output end of the amplifier AMP2 in the direction shown in FIG. Here, Vc3 is a positive constant voltage, and Vc4 is a negative constant voltage. The amplification factor of such an amplifier circuit is 1 + R1 / R2. Similarly, the amplifier circuit of FIG. 8B is a circuit in which transistors tr3 and tr4 are arranged at the output terminal of the amplifier AMP2 in the direction shown in the figure, Vc5 is a positive constant voltage, and Vc6 is a negative constant voltage. is there. The amplification factor of such an amplifier circuit is −R2 / R1. The output of a circuit (not shown) that generates a desired waveform is input to such an amplifier circuit and amplified. For example, consider the case where a transmission electrical signal having a time waveform as shown in FIG. FIG. 9 is an example of a transmission electric signal. The transmission electric signal shown in FIG. 4B is a rectangular wave having an amplitude of ± V0, but the transmission electric signal shown in FIG. 9A has an amplitude of the first waveform 40 of ± V0 and a second waveform. It is assumed that the amplitude of 42 is ± V1, and V1 is larger than V0.

  In the case of such a transmission electric signal, the ringing R1 of the first waveform and the ringing R2 of the second waveform and the second waveform are better than in the case of the transmission electric signal shown in FIG. By canceling out, ringing of the output of the resonance circuit 47 can be further reduced. That is, as shown in FIG. 9B, the amplitude of the ringing 51 in the case of the transmission electric signal shown in FIG. 9A is different from the ringing 50 in the case of the transmission electric signal shown in FIG. It has the effect of becoming smaller.

  As described above, according to the present embodiment, the transmission electrical signal is a first waveform 40 that is a rectangular-wave electrical signal of at least one cycle, and a second waveform that is an electrical signal for one cycle that is 180 degrees out of phase. The ringing can be made extremely small. Accordingly, after the transmission unit 12 transmits the transmission electrical signal, the next transmission electrical signal can be transmitted immediately and noise due to ringing is not superimposed on the next transmission electrical signal. An image can be constructed.

  In addition, according to the present embodiment, by adopting a vinylidene fluoride polymer or a copolymer of vinylidene fluoride and trifluoroethylene as the organic piezoelectric material, processing such as thinning, large area, etc. It is relatively excellent in properties, can be made in any shape and shape, has low elastic modulus, low dielectric constant, etc., so it is highly suitable for use as a piezoelectric element that receives ultrasonic signals. It has a feature that enables sensitive detection. Further, these organic piezoelectric materials are suitable as piezoelectric materials in harmonic imaging technology that requires high-frequency characteristics and broadband characteristics.

  Moreover, according to the present embodiment, by using lead zirconate titanate as the inorganic piezoelectric material, it is possible to transmit an ultrasonic signal with high sensitivity and high resolution.

  In addition, according to the present embodiment, by stacking the inorganic piezoelectric element array and the organic piezoelectric element array toward the subject H direction, the reflected second ultrasonic signal can be efficiently received, This contributes to the miniaturization of the ultrasonic probe 2.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 3 Cable 4 Inorganic piezoelectric element array 5 Organic piezoelectric element array 11 Operation input part 12 Transmitting part 13 Receiving part 14 Image processing part 15 Display part 16 Control part 17 Storage part 21 Organic piezoelectric Element 22 Inorganic piezoelectric element 23 Acoustic braking member 24 Acoustic separation part 25 Common ground electrode 26, 27, 31 Acoustic matching layer 41 Transmission electric signal 43 CMOS driver 47 Resonant circuit 101 Piezoelectric element 102, 103, 106, 107 Electrode 105 Piezoelectric element H Subject S Ultrasonic diagnostic equipment

Claims (4)

An inorganic piezoelectric element array having a plurality of piezoelectric elements, the main component of which is an inorganic piezoelectric material, which converts a transmission electrical signal into a first ultrasonic signal and transmits the first ultrasonic signal;
A first electric signal waveform having a predetermined frequency and a second electric signal waveform having a frequency substantially the same as that of the first electric signal waveform and having a phase difference of about 180 degrees are successively generated in this order. An electrical circuit that outputs a transmission electrical signal, and a transmission unit that applies the transmission electrical signal to the piezoelectric element;
A plurality of piezoelectric elements, each of which has an organic piezoelectric material as a main component, receives a harmonic component of the second ultrasonic signal generated by reflecting the first ultrasonic signal in the subject, and converts it into a received electric signal. An organic piezoelectric element array comprising:
A receiving unit including a resonance circuit that inputs the received electrical signal and uses a harmonic component of the second ultrasonic signal as a resonance frequency;
An image processing unit 14 for generating an image of an internal state in the subject from the output of the receiving unit;
An ultrasonic diagnostic apparatus comprising:   The ultrasonic diagnostic apparatus according to claim 1, wherein the organic piezoelectric material is a polymer of vinylidene fluoride or a copolymer of vinylidene fluoride and trifluoroethylene.   The ultrasonic diagnostic apparatus according to claim 1, wherein the inorganic piezoelectric material is lead zirconate titanate.   4. The inorganic piezoelectric element array according to claim 1, wherein the inorganic piezoelectric element array is stacked on the organic piezoelectric element array in a direction in which the inorganic piezoelectric element array transmits a first ultrasonic signal to the subject. The ultrasonic diagnostic apparatus according to any one of the above.

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