JP2011143047A - Ultrasonograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonograph in which detecting sensitivity itself of a higher harmonic wave component is enhanced. <P>SOLUTION: A voltage control means 18 capable of setting the direction of a voltage in an opposite direction and in the same direction relative to the directions 51, 52 of polarization in the case of transmitting an ultrasonic signal and in the case of receiving the third higher harmonic wave is installed, and thus the ultrasonograph can transmit the basis wave length having large signal intensity and can receive the third higher harmonic wave by enhancing the sensitivity converting ultrasonic signals to voltages. <P>COPYRIGHT: (C)2011,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, the inside of a subject is scanned with ultrasound from an ultrasound probe, and the internal state inside the subject is imaged based on a received signal generated from the reflected wave of the ultrasound from inside the subject. There is an ultrasound 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 is resistant to reflected ultrasonic waves. By performing the envelope detection process, it is possible to obtain a medical image such as a B-mode image. 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.

  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 harmonic imaging technology, the intensity of the side lobe is smaller than the intensity of the fundamental frequency component, the S / N ratio (Signal to Noise ratio) is improved, the contrast is improved, and the beam width is increased by increasing the frequency. Narrowing improves horizontal resolution, sound pressure is small at short distances and there is little fluctuation in sound pressure, multiple reflections are suppressed, and attenuation beyond the focal point is the same as the fundamental wave, and high frequency is fundamental It has various advantages such as a greater depth speed compared to a wave.

  However, since the intensity of the harmonic component is smaller than the intensity of the fundamental wave component, a method for accurately detecting the harmonic component has been an issue.

  In response to such a problem, for example, a technique for broadening the frequency of ultrasonic waves detected by the ultrasonic probe (see, for example, Patent Document 1), a technique for expanding an aperture for receiving harmonic components when receiving harmonic components, and the like Is disclosed (for example, see Patent Document 2).

JP 2009-82385 A Japanese Patent Laid-Open No. 11-290318

  The technique described in Patent Document 1 can widen the band in which harmonic components can be detected, but the detection sensitivity itself does not increase. Further, the technique described in Patent Document 1 increases the harmonic component received by widening the aperture, and does not improve the detection sensitivity of the harmonic component itself.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of improving the detection sensitivity itself of harmonic components and accurately detecting harmonic components.

  The above object is achieved by the invention described below.

1. A first piezoelectric part having a plurality of first piezoelectric elements that are polarized in the same direction and arranged in parallel, and a polarization process in a direction opposite to the polarization direction of the first piezoelectric element. A plurality of second piezoelectric elements arranged in parallel with each other, a second piezoelectric part including a plurality of second piezoelectric elements stacked on the first piezoelectric part and having electrodes formed on both surfaces; and an ultrasonic probe;
A transmission unit that generates a transmission signal for driving the first piezoelectric unit and the second piezoelectric unit in order to transmit an ultrasonic signal to the subject;
Voltage control means for controlling a voltage applied to the first piezoelectric part and the second piezoelectric part;
A receiving unit that receives and converts an ultrasonic signal reflected by the first piezoelectric unit and the second piezoelectric unit from a subject;
An image processing unit for generating an ultrasound image in the subject from the electrical signal;
An ultrasonic diagnostic apparatus comprising:

2. The voltage control means includes
When transmitting an ultrasonic signal to the subject, the electrodes between the first piezoelectric part and the second piezoelectric part are controlled to have the same potential, and the same voltage is applied to the other electrodes,
When receiving an ultrasonic signal reflected from a subject, control is performed so that a voltage is not applied to the electrode between the first piezoelectric portion and the second piezoelectric portion, but a voltage is applied between the other electrodes. 2. The ultrasonic diagnostic apparatus according to 1 above.

  3. The first piezoelectric portion and the second piezoelectric portion have substantially the same thickness, and two surfaces sandwiching the first piezoelectric portion and the second piezoelectric portion are a fixed end and a free end, respectively. The ultrasonic diagnostic apparatus according to 2 above, wherein the following expression is satisfied.

d = n × λ / 4
d: Sum of thicknesses of the first piezoelectric portion and the second piezoelectric portion n: natural number λ: wavelength of the first ultrasonic signal 4. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3, wherein the piezoelectric material forming at least one of the first piezoelectric portion and the second piezoelectric portion is an organic piezoelectric material.

  5. 5. The ultrasonic diagnostic apparatus according to 4 above, wherein the organic piezoelectric material is a polymer of vinylidene fluoride or a copolymer of vinylidene fluoride and trifluoroethylene.

  6). 6. The ultrasonic diagnostic apparatus according to claim 1, wherein the frequency of the ultrasonic signal reflected from the subject is a harmonic component of the first ultrasonic signal.

  It is possible to provide an ultrasonic diagnostic apparatus that improves the detection sensitivity itself of the harmonic component and can detect the harmonic component with high accuracy.

1 is a schematic diagram showing an external configuration of an ultrasonic diagnostic apparatus according to an embodiment. 1 is a block diagram showing an electrical configuration of an ultrasonic diagnostic apparatus according to an embodiment. 1 is a schematic diagram showing a configuration of an ultrasonic probe of an ultrasonic diagnostic apparatus according to an embodiment. It is a schematic diagram explaining the waveform of the ultrasonic signal of a resonance state. 4 is a schematic diagram for explaining the direction of polarization and the direction of an electric field of a piezoelectric part 32. FIG. It is a schematic diagram showing operation | movement of the voltage control means 18 concerning 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.

  FIG. 1 is a schematic diagram illustrating an external configuration of an ultrasonic diagnostic apparatus according to an embodiment. FIG. 2 is a block diagram illustrating an electrical configuration of the ultrasonic diagnostic apparatus according to the embodiment. FIG. 3 is a schematic diagram illustrating a configuration of an ultrasonic probe of the ultrasonic diagnostic apparatus according to the embodiment.

  As shown in FIGS. 1 and 2, the ultrasonic diagnostic apparatus S transmits an ultrasonic signal (hereinafter also referred to as a first ultrasonic signal) to a subject H such as a living body (not shown), and the subject. An ultrasonic probe 2 that receives a reflected wave of the ultrasonic signal reflected by H (hereinafter also referred to as a second ultrasonic signal), and is connected to the ultrasonic probe 2 and the cable 3 through the ultrasonic probe. By transmitting a transmission signal of an electric signal to the probe 2 via the cable 3, the ultrasonic probe 2 transmits the first ultrasonic signal to the subject H and receives it by the ultrasonic probe 2. Based on the received signal of the electrical signal generated by the ultrasound probe 2 in accordance with the second ultrasound signal from the subject H, the internal state in the subject H is imaged as a medical image as an ultrasound image. And an ultrasonic diagnostic apparatus main body 1 to be configured. The ultrasonic diagnostic apparatus main body 1 is provided with an ultrasonic probe folder 4 for holding the ultrasonic probe 2 when the ultrasonic probe 2 is not used.

  For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11, a transmission unit 12, a reception unit 13, a signal processing unit 14, an image processing unit 15, a display unit 16, The control unit 17, the storage unit 19, and the voltage control means 18 of the present invention are provided.

  The operation input unit 11 inputs data such as a command instructing the start of diagnosis and personal information of the subject H, for example, and is an operation panel or a keyboard provided with a plurality of input switches, for example.

  The transmission unit 12 is a circuit having a function of generating a transmission signal of an electrical signal for driving a first piezoelectric unit and a second piezoelectric unit described later according to the control of the control unit 17. The transmission unit 12 supplies a transmission signal to the first piezoelectric unit and the second piezoelectric unit in the ultrasonic probe 2 via the voltage control means 18 and the cable 3, and the first probe is supplied to the ultrasonic probe 2. An ultrasonic signal is generated. The transmission unit 12 includes, for example, a high voltage pulse generator that generates a high voltage pulse.

  The receiving unit 13 is a circuit that receives a reception signal of an electrical signal from the ultrasound probe 2 via the cable 3 under the control of the control unit 17, and outputs the reception signal to the signal processing unit 14. The receiving unit 13 includes, for example, an amplifier that amplifies the reception signal at a predetermined amplification factor set in advance, an analog-digital converter that converts the reception signal amplified by the amplifier from an analog signal to a digital signal, and the like. Configured.

  The signal processing unit 14 is a circuit that performs predetermined signal processing on the electrical signal from the reception unit 13 under the control of the control unit 17, and outputs the reflected reception signal subjected to the signal processing to the image processing unit 15.

  Under the control of the control unit 17, the image processing unit 15 generates an ultrasonic image of the internal state in the subject H using, for example, a harmonic imaging technique based on the reflected reception signal signal-processed by the signal processing unit 14. Circuit. For example, a B-mode signal corresponding to the amplitude intensity of the second ultrasonic signal is generated by performing envelope detection processing on the reflected reception signal.

  The storage unit 19 includes a RAM and a ROM, and stores a program used for the control unit 17 and also records various image templates to be displayed on the display unit 16.

  The voltage control means 18 of the present invention controls how the transmission signal of the electrical signal from the transmission unit 12 is applied to the first piezoelectric unit and the second piezoelectric unit according to the control of the control unit 17. It has a function. Details will be described later.

  The display unit 16 is a device that displays the ultrasonic image generated by the image processing unit 15 under the control of the control unit 17. The display unit 16 is, for example, a display device such as a CRT display, LCD, EL display, or plasma display, or a printing device such as a printer.

  The control unit 17 includes, for example, a microprocessor, a storage element, and peripheral circuits thereof. The operation input unit 11, the transmission unit 12, the reception unit 13, the signal processing unit 14, the image processing unit 15, and a voltage control unit. 18 and a circuit that controls the entire ultrasound diagnostic apparatus S by controlling the storage unit 19 according to the function.

  On the other hand, the ultrasonic probe 2 includes a vibration unit 30. The vibration unit 30 transmits the first ultrasonic signal to the subject H such as a living body (not shown) and receives the second ultrasonic signal from the subject H. As shown in FIG. 3, for example, the vibration unit 30 includes an acoustic braking member 31, a piezoelectric unit 32, an acoustic matching layer 33, and an acoustic lens 34.

  The acoustic braking member 31 is a flat plate member made of a material that absorbs ultrasonic waves, and absorbs ultrasonic waves radiated from the piezoelectric portion 32 toward the acoustic braking member 31.

  The piezoelectric part 32 includes a first piezoelectric part 321 and a second piezoelectric part 322. The first piezoelectric unit 321 and the second piezoelectric unit 322 include a piezoelectric material, and convert signals between an electric signal and an ultrasonic signal by using a piezoelectric phenomenon.

  In the first piezoelectric unit 321, a plurality of piezoelectric elements (first piezoelectric elements) that have been subjected to polarization processing in the same direction along the direction in which ultrasonic signals are transmitted and received are arranged in parallel. Electrodes are formed on both surfaces of the first piezoelectric portion 321.

  In the second piezoelectric part 322, a plurality of piezoelectric elements (second piezoelectric elements) subjected to polarization processing in a direction opposite to the polarization direction of the first piezoelectric part 321 are arranged in parallel. Electrodes are formed on both surfaces of the second piezoelectric portion 322.

  In the present embodiment, the first piezoelectric portion 321 and the second piezoelectric portion 322 are laminated and the electrodes in contact with each other are shared.

  The piezoelectric unit 32 converts a transmission electrical signal input from the transmission unit 12 of the ultrasonic diagnostic apparatus main body 1 via the cable 3 into a first ultrasonic signal, transmits the first ultrasonic signal, and receives the first ultrasonic signal. The second ultrasonic signal is converted into an electric signal, and this electric signal (reception signal) is output to the receiving unit 13 of the ultrasonic diagnostic apparatus body 1 via the cable 3. When the ultrasonic probe 2 is brought into contact with the subject H, the first ultrasonic signal generated by the piezoelectric unit 32 is transmitted into the subject H, and the second ultrasonic signal from within the subject H is transmitted. Received by the piezoelectric unit 32.

  The first piezoelectric part 321 and the second piezoelectric part 322 may be formed of the same material or different materials. When they are formed of different materials, the acoustic impedances are often different, so an intermediate layer (not shown) may be provided between the first piezoelectric portion 321 and the second piezoelectric portion 322.

Next, an ultrasonic signal transmitted and received by the piezoelectric unit 32 will be described. FIG. 4 is a schematic diagram for explaining the waveform of an ultrasonic signal in a resonance state. 4A shows a case where an ultrasonic signal of a fundamental wave is transmitted / received, FIG. 4B shows a case where a third harmonic wave is transmitted / received, and FIG. 4C shows an nth harmonic wave (n is a natural number). FIG. 4 shows a displacement diagram, a distortion diagram, and a frequency diagram when transmitting / receiving. λ ₁ represents the wavelength of the fundamental wave, λ ₃ represents the wavelength of the third harmonic, and λ _n represents the wavelength of the nth harmonic.

  In each displacement diagram, the waveform of the ultrasonic signal has a fixed end 41 as a node, and forms a standing wave between the fixed end 41 and the free end. The thickness of the piezoelectric part 32 is set to ¼ of the fundamental wavelength of the first ultrasonic signal. Since the thickness of the piezoelectric part 32 is set to ¼ of the fundamental wavelength of the first ultrasonic signal, the fundamental wave becomes the resonance mode of the fundamental resonance, the third harmonic becomes the resonance mode of the 3 o'clock resonance, and the n th The harmonic becomes a resonance mode of n-th order resonance.

In FIG. 4 (a), it indicates that the thickness of the piezoelectric portion 32 is equivalent to λ _1/4, in FIG. 4 (b), the indicates that the thickness of the piezoelectric portion 32 is equivalent to λ _3/4, FIG. 4C shows that the thickness of the piezoelectric portion 32 corresponds to λ _n / 4. λ ₁ represents the wavelength of the fundamental wave, λ ₃ represents the wavelength of the second harmonic, and λ _n represents the wavelength of the nth harmonic.

When the wavelength of the nth harmonic is used, the sum d of the thicknesses of the first piezoelectric portion and the second piezoelectric portion and the wavelength λ of the first ultrasonic signal have a relationship of d = n × λ _n / 4.

  As shown in the frequency diagram, the intensities of the fundamental wave, the third harmonic wave, and the nth harmonic wave decrease in the order of the fundamental wave, the third harmonic wave, and the nth harmonic wave.

  When the standing wave of the fundamental wave, the third harmonic wave, and the nth harmonic wave stands on the piezoelectric part 32, the relationship between each first ultrasonic signal and the distortion generated in the piezoelectric part 32 is as shown in the distortion diagram. . The case where each part in the first piezoelectric part and the second piezoelectric part contracts is represented by a positive sign and the case where each part expands is represented by a negative sign.

  Next, the sensitivity that is the relationship between the first ultrasonic signal and the voltage of the piezoelectric portion 32 in the case of the basic resonance and the tertiary resonance will be described with reference to Table 1 and FIG.

  Table 1 is a table for explaining the sensitivity of the piezoelectric part 32. FIG. 5 is a schematic diagram for explaining the polarization direction and the electric field direction of the piezoelectric portion 32.

  In the stacked piezoelectric unit 32 used in the conventional ultrasonic probe, as shown in FIG. 5B, the polarization directions 51 and 52 are the same direction (parallel) with respect to the voltage direction. ) Was set. On the other hand, in the piezoelectric part 32, as shown in FIG. 5A, the directions of polarization 51 and 52 are set in opposite directions (antiparallel) with respect to the direction of voltage.

  Based on such a difference in the direction of polarization, the sensitivity of each of the first piezoelectric portion 321 and the second piezoelectric portion 322, the first piezoelectric portion 321 and the second piezoelectric portion for each resonance mode of basic resonance and tertiary resonance. Table 1 shows the total sensitivity of the entire piezoelectric portion 32 including the portion 322.

  First, when the internal polarization is parallel and in the fundamental mode, the sensitivity of the first piezoelectric unit 321 is proportional to sin 45 ° −sin 0 ° = 0.71, and the sensitivity of the second piezoelectric unit 322 is sin 90 ° −sin 45 °. = 0.71. Therefore, the total sensitivity is proportional to 1.00.

  When the internal polarization is parallel and in the third resonance mode, the sensitivity of the first piezoelectric part 321 is proportional to sin135 ° −sin0 ° = 0.71, and the sensitivity of the second piezoelectric part 322 is sin270 ° −sin135 °. = -1.71. Therefore, the total sensitivity is proportional to -1.00.

  When the internal polarization is antiparallel and in the fundamental resonance mode, the sensitivity of the first piezoelectric unit 321 is proportional to sin 45 ° −sin 0 ° = 0.71, and the sensitivity of the second piezoelectric unit 322 is sin 90 ° −sin 45 °. = -0.29. Therefore, the total sensitivity is proportional to 0.42.

  When the internal polarization is antiparallel and the third resonance mode, the sensitivity of the first piezoelectric unit 321 is proportional to sin135 ° −sin0 ° = 0.71, and the sensitivity of the second piezoelectric unit 322 is −sin270 ° + sin135. It is proportional to ° = 1.71. Therefore, the total sensitivity is proportional to 2.42. The item of distortion in Table 1 indicates that the first piezoelectric unit 321 and the second piezoelectric unit 322 are mutually compatible when the signs of sensitivity are the same, and cancel each other when the signs are different.

  As described above, the internal polarization differs depending on whether it is parallel or antiparallel, and the difference between the fundamental wave and the third harmonic is that the polarization direction and the sign of the first ultrasonic signal intensity work in the direction in which they strengthen. This is because there is a difference.

  As a result, it is understood that the best total sensitivity is obtained when the internal polarization is antiparallel and the third resonance mode. Therefore, by receiving the third harmonic wave with the polarization direction antiparallel to the parallel polarization direction employed in the conventional ultrasonic probe, both sides of the piezoelectric portion 32 are 2.42 times larger. Can be obtained.

  On the other hand, when transmitting the first ultrasonic signal, as in the prior art, transmitting the fundamental wavelength having a large signal intensity with the polarization directions 51 and 52 being the same as the voltage direction. Become. Therefore, in the case of transmitting the first ultrasonic signal and the case of receiving the third harmonic, the polarization directions 51 and 52 are set to be opposite to each other with respect to the voltage direction, and in addition, the opposite directions are set. It is desirable to provide voltage control means that can also be set. The voltage control means 18 according to the present invention will be described below.

  FIG. 6 is a schematic diagram showing the operation of the voltage control means 18. The piezoelectric part 32 has electrodes 71, 72, 73 formed so as to sandwich the first piezoelectric part 321 and the second piezoelectric part 322. The voltage control means has switches 61, 62, 63 controlled by the control unit 17. The switch 61 is a switch that controls conduction and non-conduction between the electrode 73 and the ground. The switch 62 is a switch that distributes the output from the power supply V to one of the electrodes 72 and 73. The switch 63 is a switch that controls conduction and non-conduction between the electrode 72 and the ground. Specifically, the switches 61, 62, and 63 are configured by field effect transistors or bipolar transistors.

  In FIG. 6A, the switch 61 is turned on, 63 is released, and the switch 62 is switched to the electrode 72. By switching in this way, the electric fields 64 and 65 from the electrodes 73 and 71 are set in the same direction as the polarization direction 51 of the second piezoelectric part 322 and the polarization direction 52 of the first piezoelectric part 321, that is, parallel to each other. be able to. By controlling the switches 61, 62, and 63 in this way, a state in which the fundamental wave can be transmitted can be realized.

  In FIG. 6C, the switches 61 and 63 are opened to make the switch non-conductive, and the switch 62 is switched to the electrode 73. An electric field is formed between the electrode 71 and the electrode 73. By switching in this way, an electric field 66 is formed in the first piezoelectric part 321 and the second piezoelectric part 322, and the direction of the electric field 66 is the same as the polarization direction 52 of the first piezoelectric part 321. It is set to a direction opposite to the polarization direction 51 of the second piezoelectric portion 322. That is, it can be antiparallel. By controlling the switches 61, 62, and 63 in this way, it is possible to realize a state in which the third harmonic can be received with high total sensitivity.

  In addition, when the voltage control means 18 switches to the switch state at the time of ultrasonic reception of FIG. 6C, as shown in FIG. 6B, the switch 62 is once distributed to the electrode 73 side, and It is desirable to use the switch 63 to make the electrode 72 conductive to ground. Thus, by making the electrode 72 conductive with the ground, the charge accumulated in the electrode 72 can be released, and the influence of the electrically floating electrode 72 on the electric field when receiving ultrasonic waves can be prevented. it can.

  As described above, in the case of transmitting the first ultrasonic signal and the case of receiving the third harmonic, the direction of the voltage is set to be opposite to the direction of polarization 51, 52, and in addition By providing the voltage control means 18 that can be set in the same direction, a fundamental wavelength having a large signal intensity can be transmitted, and the sensitivity of converting the first ultrasonic signal into a voltage is increased to receive the third harmonic. can do.

Next, the piezoelectric material employed in the piezoelectric unit 32 will be described. In the present embodiment, for example, the first piezoelectric part 321 and the second piezoelectric part 322 in the piezoelectric part 32 are configured by inorganic piezoelectric elements made of an inorganic piezoelectric material, for example. Examples of the inorganic piezoelectric material include so-called PZT, quartz, lithium niobate (LiNbO ₃ ), potassium niobate tantalate (K (Ta, Nb) O ₃ ), barium titanate (BaTiO ₃ ), lithium tantalate (LiTaO _3). And strontium titanate (SrTiO ₃ ). In the present embodiment, the inorganic piezoelectric element capable of increasing the transmission power in this way is used for the first piezoelectric portion 321 and the second piezoelectric portion 322.

  Further, for example, the first piezoelectric part 321 and the second piezoelectric part 322 may be composed of organic piezoelectric elements made of an organic piezoelectric material. The thickness of the organic piezoelectric element is appropriately set depending on, for example, the frequency of the ultrasonic wave to be received, the type of the organic piezoelectric material, and the like. For example, when receiving an ultrasonic wave having a center frequency of 8 MHz, the organic piezoelectric element The thickness of is about 50 μm.

  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 70 to 90 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, it is suitable as a piezoelectric material in harmonic imaging technology that requires high-frequency characteristics and broadband characteristics.

  The first piezoelectric portion 321 and the second piezoelectric portion 322 may be made of an inorganic piezoelectric material on one side and an organic piezoelectric material on the other side.

  In this embodiment, since the second ultrasonic signal can be received with high sensitivity as described above, it is suitable for a harmonic imaging technique that requires receiving a second ultrasonic signal having a relatively low signal intensity. Therefore, it is possible to provide a more accurate ultrasonic image.

  In the present embodiment, the ultrasonic probe 2 may be connected to the ultrasonic diagnostic apparatus main body 1 by wire or wirelessly.

  As described above, according to the present embodiment, the voltage direction is opposite to the polarization directions 51 and 52 when the first ultrasonic signal is transmitted and when the third harmonic is received. By providing voltage control means that can be set in the same direction and also set in the same direction, it is possible to transmit a fundamental wavelength having a large signal intensity and to increase the sensitivity of converting the second ultrasonic signal to a voltage. Third harmonics can be received.

  In addition, according to the present embodiment, a high-frequency ultrasonic signal such as the second ultrasonic signal can be received in a wide band by adopting an organic piezoelectric material as the material of the receiving element. An ultrasonic image can be obtained.

  In addition, according to the present embodiment, the organic piezoelectric material uses a vinylidene fluoride polymer or a vinylidene fluoride / trifluoroethylene copolymer to detect the second ultrasonic signal with high sensitivity. And a clearer ultrasonic image can be obtained.

  Moreover, according to this Embodiment, the frequency of a 2nd ultrasonic signal can obtain a clearer ultrasonic image by employ | adopting the harmonic component of a 1st ultrasonic signal.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 3 Cable 4 Ultrasonic probe folder 11 Operation input part 12 Transmission part 13 Reception part 14 Signal processing part 15 Image processing part 16 Display part 17 Control part 18 Voltage control means 19 Storage unit 30 Vibration unit 31 Acoustic braking member 32 Piezoelectric unit 33 Acoustic matching layer 34 Acoustic lens 61, 62, 63 switch 321 First piezoelectric unit 322 Second piezoelectric unit H Subject

Claims (6)

A first piezoelectric part having a plurality of first piezoelectric elements that are polarized in the same direction and arranged in parallel, and a polarization process in a direction opposite to the polarization direction of the first piezoelectric element. A plurality of second piezoelectric elements arranged in parallel with each other, a second piezoelectric part including a plurality of second piezoelectric elements stacked on the first piezoelectric part and having electrodes formed on both surfaces; and an ultrasonic probe;
A transmission unit that generates a transmission signal for driving the first piezoelectric unit and the second piezoelectric unit in order to transmit an ultrasonic signal to the subject;
Voltage control means for controlling a voltage applied to the first piezoelectric part and the second piezoelectric part;
A receiving unit that receives and converts an ultrasonic signal reflected by the first piezoelectric unit and the second piezoelectric unit from a subject;
An image processing unit for generating an ultrasound image in the subject from the electrical signal;
An ultrasonic diagnostic apparatus comprising: The voltage control means includes
When transmitting an ultrasonic signal to the subject, the electrodes between the first piezoelectric part and the second piezoelectric part are controlled to have the same potential, and the same voltage is applied to the other electrodes,
When receiving an ultrasonic signal reflected from a subject, control is performed so that a voltage is not applied to the electrode between the first piezoelectric portion and the second piezoelectric portion, but a voltage is applied between the other electrodes. The ultrasonic diagnostic apparatus according to claim 1. The first piezoelectric portion and the second piezoelectric portion have substantially the same thickness, and two surfaces sandwiching the first piezoelectric portion and the second piezoelectric portion are a fixed end and a free end, respectively. The ultrasonic diagnostic apparatus according to claim 2, wherein the following expression is satisfied.
d = n × λ / 4
d: sum of thicknesses of the first and second piezoelectric parts n: natural number λ: wavelength of the first ultrasonic signal   4. The ultrasonic diagnostic apparatus according to claim 1, wherein the piezoelectric material forming at least one of the first piezoelectric portion and the second piezoelectric portion is an organic piezoelectric material. 5.   The ultrasonic diagnostic apparatus according to claim 4, 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 frequency of the ultrasonic signal reflected from the subject is a harmonic component of the first ultrasonic signal.

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