JP2012143322A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus capable of obtaining clear ultrasonic images by deleting both a second-order harmonic wave component and a third-order harmonic wave component present in transmission wave from an ultrasonic probe.SOLUTION: The ultrasonic diagnostic apparatus includes: the ultrasonic probe comprising at least one piezoelectric element body that has a piezoelectric element group comprising at least four piezoelectric elements for outputting ultrasonic waves of fundamental wave, n-order wave and m-order wave and forms a set of the four piezoelectric elements in the piezoelectric element group as the first to fourth piezoelectric elements; a transmitting means; a receiving means; a higher harmonics wave extracting part; and an image processing part. The transmitting means is driven so that the phase difference in n-order wave of the first and third piezoelectric elements and the phase difference in n-order wave of the second and fourth piezoelectric elements are both 180° and that the phase difference in m-order wave of the first and second piezoelectric elements and the phase difference in m-order wave of the third and fourth piezoelectric elements are both 180°.

Description

  The present invention relates to an ultrasonic diagnostic apparatus that transmits ultrasonic waves into a subject, receives reflected ultrasonic waves generated by reflection of the ultrasonic waves in the subject, and forms an image in the subject.

  Ultrasound is used to examine the inside in a non-destructive, harmless and almost real-time manner, and is applied to various fields such as defect inspection and disease diagnosis. One of them is an ultrasonic diagnostic apparatus that scans the inside of a subject with ultrasound and images the internal state of the subject based on a reception signal generated from a reflected wave of the ultrasound coming from inside the subject. . Ultrasound diagnostic devices are smaller and cheaper for medical use than other medical imaging devices, are free of radiation exposure such as X-rays, are highly safe, and display blood flow using the Doppler effect. It has various features such as being possible. For this reason, an ultrasonic diagnostic apparatus includes a circulatory system (eg, coronary artery of the heart), a digestive system (eg, gastrointestinal), an internal system (eg, liver, pancreas, and spleen), and a urinary system (eg, kidney and bladder). Widely used in obstetrics and gynecology.

  An ultrasonic probe that transmits and receives ultrasonic waves to and from a subject is used in the ultrasonic diagnostic apparatus. The ultrasonic probe uses the piezoelectric phenomenon to generate ultrasonic waves by mechanical vibration based on the transmitted electrical signal, and to receive reflected ultrasonic waves generated by acoustic impedance mismatch within the subject. Thus, a plurality of piezoelectric elements that generate electrical signals are provided, and the plurality of piezoelectric elements are arranged in a two-dimensional array, for example.

  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 of the sound pressure is small at short distances, so that multiple reflections are suppressed. It has various advantages such as a greater depth than the case. (For example, refer to Patent Documents 1 and 2).

  In harmonic imaging technology, the harmonic component contained in the ultrasound reflected back from the subject is very small compared to the fundamental component, so advanced technology is used to extract only the harmonic component. Yes. On the other hand, since the time waveform of the ultrasonic wave transmitted from the ultrasonic probe is a pulse waveform, it contains a harmonic component. The harmonic component inherent in the transmitted ultrasonic wave has a magnitude that cannot be ignored compared to the harmonic component included in the ultrasonic wave reflected and returned from the subject. Therefore, the harmonic component inherent in the transmitted ultrasonic wave becomes a noise component when extracting the harmonic component included in the ultrasonic wave reflected and returned from the subject, and in obtaining a clear ultrasonic image. It is what you want to remove.

  To deal with this problem, Patent Document 3 discloses a technique for canceling the reflected fundamental wave into two waves and extracting the remaining harmonic components.

  In Patent Document 4, the transmission wave is divided into a plurality of parts, and the phases of the divided transmission waves are displaced by π / 3 and added together, thereby canceling the third harmonic contained in the transmission wave.

Japanese Patent Laid-Open No. 10-118065 JP 2007-185525 A JP 2010-017406 A JP 2010-063493 A

  The techniques disclosed in Patent Documents 3 and 4 are techniques that can eliminate only one higher-order harmonic among the higher-order harmonics. Therefore, even if the second harmonic component is deleted, the third harmonic component remains, and conversely, the second harmonic component remains even if the third harmonic component is deleted. The remaining high-order harmonics become noise components when extracting the harmonic components contained in the ultrasonic wave reflected back from the subject.

  An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of obtaining a clear ultrasonic image by eliminating both the second harmonic component and the third harmonic component.

  The above object is achieved by the invention described below.

1. Piezoelectric elements that output ultrasonic waves of fundamental waves, n-order waves (n is a natural number of 2 or more) and m-order waves (m is a natural number of 2 or more different from n), and 4 piezoelectric elements having the same output characteristics An ultrasonic probe comprising at least one piezoelectric element group, and at least one piezoelectric element body in which the four piezoelectric elements in the piezoelectric element group are grouped from the first piezoelectric element to the fourth piezoelectric element. When,
Transmitting means for transmitting ultrasonic waves to the ultrasonic probe;
Receiving means for receiving an electrical signal obtained by converting the reflected ultrasound from the subject by the ultrasound probe;
A harmonic extraction unit for extracting harmonic components contained in the electrical signal;
An image processing unit that generates an ultrasonic image in the subject from the harmonic component, and
In each of the piezoelectric element bodies, the transmission means includes a phase difference in the nth order wave of the first piezoelectric element and the third piezoelectric element and a phase difference in the nth order wave of the second piezoelectric element and the fourth piezoelectric element are both 180 degrees. The phase difference in the m-th order wave of the first piezoelectric element and the second piezoelectric element and the phase difference in the m-th order wave of the third piezoelectric element and the fourth piezoelectric element are both driven to be 180 degrees. A characteristic ultrasonic diagnostic apparatus.

  2. 2. The ultrasonic diagnostic apparatus according to 1, wherein the first to fourth piezoelectric elements are installed in a proximity state within 5 mm.

  3. The ultrasonic diagnostic apparatus according to 1 or 2, wherein 10 or more sets of the piezoelectric element bodies are provided, and each piezoelectric element is arranged one-dimensionally or two-dimensionally.

  4). 4. The ultrasonic diagnostic apparatus according to claim 1, wherein the n is 2 and the m is 3. 5.

  The present invention can provide an ultrasonic diagnostic apparatus capable of obtaining a clear ultrasonic image by eliminating both the second harmonic component and the third harmonic component.

1 is a schematic diagram showing an external configuration of an ultrasonic diagnostic apparatus S according to an embodiment. 1 is a block diagram showing an electrical configuration of an ultrasonic diagnostic apparatus S according to an embodiment. FIG. 3 is a diagram showing a part related to transmission of the ultrasound probe 2 and an internal configuration of a transmission unit 12. FIG. 3 is a diagram showing a part related to reception in the ultrasonic probe 2 and an internal configuration of a receiving unit 13. It is a schematic diagram which shows the structure of the vibration part 20 of the ultrasonic probe 2 which concerns on embodiment. It is explanatory drawing explaining the example of the delay time provided to the piezoelectric element 221 of each channel which comprises the piezoelectric element group 200 which concerns on embodiment. It is an example of the actual value of the time waveform of the fundamental wave and the transmission wave which concerns on this invention. It is a frequency spectrum of a fundamental wave and a transmission wave according to the present invention.

  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 showing an external configuration of an ultrasonic diagnostic apparatus S according to the embodiment. FIG. 2 is a block diagram showing an electrical configuration of the ultrasonic diagnostic apparatus S according to the embodiment.

  As shown in FIGS. 1 and 2, the ultrasonic diagnostic apparatus S transmits ultrasonic waves to a subject H such as a living body (not shown) and receives reflected ultrasonic waves reflected by the subject H. The ultrasonic probe 2 is connected to the ultrasonic probe 2 via the cable 3, and an ultrasonic signal is transmitted to the ultrasonic probe 2 via the cable 3. The child 2 transmits an ultrasonic wave to the subject H, and an electrical signal generated by the ultrasonic probe 2 in response to the reflected ultrasonic wave from the subject H received by the ultrasonic probe 2 And an ultrasonic diagnostic apparatus body 1 that images the internal state of the subject H as an ultrasonic image into a medical image based on the received signal.

  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 reception signal processing unit 14, an image processing unit 15, and a display unit 16. , A control unit 17, a storage unit 19, and a transmission signal processing unit 18.

  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 signal processing unit 18 is a circuit as a transmission unit having a function of generating a transmission signal of an electrical signal that drives a piezoelectric unit 22 described later under the control of the control unit 17.

  The transmission unit 12 amplifies the electrical signal generated by the transmission signal processing unit 18, supplies the transmission signal to the piezoelectric unit 22 in the ultrasonic probe 2 via the cable 3, and supplies the ultrasonic probe 2 to the ultrasonic probe 2. Generate ultrasound. The transmission unit 12 includes, for example, a high voltage pulse generator that generates a high voltage pulse. Further, the transmission unit 12 incorporates a transmission beam former 121 described later.

  The reception unit 13 is a circuit as a reception unit 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 this reception signal is sent to the reception signal processing unit 14. Output. The receiving unit 13 includes, for example, an amplifier that amplifies the received signal at a predetermined amplification factor, an analog-digital converter that converts the received signal amplified by the amplifier from an analog signal to a digital signal, and also described later. A receiving beamformer 131 is built in.

  The reception signal processing unit 14 is a circuit as a harmonic extraction unit that extracts a harmonic component from the electrical signal from the reception unit 13 or performs predetermined signal processing in accordance with the control of the control unit 17. The reflected reception signal is output to the image processing unit 15.

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

  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 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 reception signal processing unit 14, the image processing unit 15, a display unit, and the like. 16 is a circuit that performs overall control of the ultrasound diagnostic apparatus S by controlling the transmission signal processing unit 18 and the storage unit 19 in accordance with the function.

  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 ultrasonic probe 2 includes a vibration unit 20. The vibration unit 20 transmits ultrasonic waves to the subject H such as a living body (not shown) and receives reflected ultrasonic waves from the subject H.

  FIG. 3 is a diagram illustrating a part related to transmission of the ultrasound probe 2 and an internal configuration of the transmission unit 12.

  The vibration unit 20 provided in the ultrasonic probe 2 includes a piezoelectric element group 200 including a plurality of piezoelectric elements 221 and an amplifier 202 that amplifies a transmission signal output from the transmission beam former 121 to each piezoelectric element. ing.

  The transmission beamformer 121 functions to generate a transmission signal based on the delay table stored in the delay table storage unit 123.

  The transmission beamformer 121 includes a delay table storage unit 123 and a delay pulse generation circuit 122, and outputs a transmission signal to each of the plurality of piezoelectric elements 221 via the amplifier 202 based on the delay table.

  As described above, the delay table is a table in which the transmission timing of ultrasonic waves for each piezoelectric element 221, that is, a delay adjustment amount corresponding to all the steering angles required in electronic scanning is recorded.

  Based on the delay table acquired in the delay table storage unit 123, the delay pulse generation circuit 122 outputs a transmission signal to each piezoelectric element 221 via the amplifier 202 at an ultrasonic output timing specified by the delay table. . Thereby, the ultrasonic wave is focused in the subject.

  In addition, for example, a delay table that defines various focus positions can be stored in the delay table storage unit 123 to realize a desired focus position.

  FIG. 4 is a diagram illustrating a portion related to reception in the ultrasound probe 2 and an internal configuration of the reception unit 13.

  Each piezoelectric element 221 in the vibration unit 20 receives an ultrasonic wave reflected from the living body of the subject H and outputs a reception signal. The reception signal is output to the reception unit 13 via the amplifier 201 provided for each piezoelectric element 221.

  In the reception unit 13, the output from the vibration unit 20 is input to the reception beam former 131 through the low-pass filter 134.

  The reception beamformer 131 in the reception unit 13 includes a phasing addition unit 132 and an analog-digital converter (ADC) 133. The reception beam former 131 performs a delay adjustment for each reception signal output from each piezoelectric element 221 and performs a so-called phasing addition process in which the reception signal after the delay adjustment is added.

  The reception signal after the phasing addition output from the phasing addition unit 132 is analog-digital converted in the ADC 133 and output to the reception signal processing unit 14.

  FIG. 5 is a schematic diagram illustrating a configuration of the vibration unit 20 of the ultrasonic probe 2 according to the embodiment. The vibration unit 20 includes a piezoelectric unit 22, an acoustic matching layer 23, an acoustic lens 24, a backing layer 25, and a fixed plate 26.

  The piezoelectric unit 22 converts signals between electrical signals and ultrasonic waves by using the piezoelectric phenomenon in the plurality of piezoelectric elements 221.

  The piezoelectric unit 22 converts an electric signal of a transmission signal input from the transmission unit 12 of the ultrasonic diagnostic apparatus main body 1 via the cable 3 into an ultrasonic wave, transmits the ultrasonic wave, and converts the received reflected ultrasonic wave into an electric wave. The signal is converted into a signal, and the received signal, which is an electrical signal, is output to the receiving unit 13 of the ultrasonic diagnostic apparatus body 1 via the cable 3.

  When the ultrasound probe 2 is brought into contact with the subject H, the ultrasound generated by the piezoelectric unit 22 is transmitted into the subject H, and the reflected ultrasound from the subject H is received by the piezoelectric unit 22. Is done. An inorganic material or an organic material is used as the piezoelectric material.

  The acoustic matching layer 23 includes an acoustic impedance having a value between the acoustic impedance of the piezoelectric unit 22 and the acoustic impedance of the subject H, so that when transmitting the ultrasonic wave transmitted from the piezoelectric unit 22 to the subject H, It has a function of reducing reflected ultrasonic waves generated according to the difference in acoustic impedance between the piezoelectric unit 22 and the subject H, and the ultrasonic waves generated by the piezoelectric unit 22 are reflected to and within the subject H. Ultrasonic waves can be efficiently transmitted to the piezoelectric unit 22. If two or more acoustic matching layers are formed so that the acoustic impedance gradually approaches the subject H from the piezoelectric portion 22, reflection of ultrasonic waves between the piezoelectric portion 22 and the subject H can be reduced. Can do.

  The acoustic lens 24 has a function of focusing the ultrasonic wave transmitted from the piezoelectric unit 22 toward the measurement location.

  The backing layer 25 is a member made of a material that absorbs ultrasonic waves, and is an ultrasonic absorber that can absorb unnecessary ultrasonic waves emitted from the piezoelectric portion 22 toward the backing layer 25. A preferable backing material is made of a rubber-based composite material and / or an epoxy resin composite material, and the shape thereof can be appropriately selected according to the shape of the piezoelectric body or the probe head including the piezoelectric body.

  The fixing plate 26 has a function of fixing the backing layer 25 and imparting rigidity to the ultrasonic probe 2 or fixing at the time of processing.

  Next, a description will be given of means for eliminating high-order harmonics contained in the transmitted ultrasonic waves so that only the fundamental wave is generated.

  In the present embodiment, each piezoelectric element 221 of the piezoelectric element group 200 constituting the vibration unit 20 outputs a fundamental wave, an nth-order wave, and an mth-order ultrasonic wave, and all the piezoelectric elements 221 have the same output. It shall have characteristics. That is, the transmission signal sent from the transmission unit 12 is set so that the amplitudes of the fundamental wave, the nth order wave, and the mth order wave in the ultrasonic wave output from each piezoelectric element 221 are driven to the same. Note that n and m are two or more natural numbers different from each other.

  A group of four of the piezoelectric elements 221 constituting the piezoelectric element group 200 is regarded as a set as a piezoelectric element body 220.

  The four piezoelectric elements constituting the piezoelectric element body 220 are referred to as first to fourth piezoelectric elements. As shown in FIG. 5, the piezoelectric element 221a is a first piezoelectric element, the piezoelectric element 221b is a second piezoelectric element, the piezoelectric element 221c is a third piezoelectric element, and the piezoelectric element 221d is a fourth piezoelectric element.

  In the present embodiment, in each piezoelectric element body 220, both the phase difference in the nth order wave of the first piezoelectric element and the third piezoelectric element and the phase difference in the nth order wave of the second piezoelectric element and the fourth piezoelectric element are both. Each piezoelectric element is driven to be 180 degrees, and both the phase difference in the mth order wave of the first piezoelectric element and the second piezoelectric element and the phase difference in the mth order wave of the third piezoelectric element and the fourth piezoelectric element are both Drive to be 180 degrees.

  Hereinafter, it is assumed that n is 2 and m is 3.

  First, the elimination of the secondary wave will be described. Driving is performed so that the phase difference in the secondary wave of the first piezoelectric element 221a and the third piezoelectric element 221c and the phase difference in the secondary wave of the second piezoelectric element 221b and the fourth piezoelectric element 221d are both 180 degrees. .

  Specifically, regarding the initial phase, the phase of the first piezoelectric element 221a in the fundamental wave is 0, the phase of the second piezoelectric element 221b is π / 3, the phase of the third piezoelectric element 221c is π / 2, The phase of the four piezoelectric elements 221d is set to 5π / 6.

  Then, since the wavelength of the secondary wave is halved, the phase also advances twice, the phase of the second piezoelectric element 221b is 2π / 3, the phase of the third piezoelectric element 221c is π, The phase of the four piezoelectric elements 221d is 10π / 6.

  Accordingly, the phase difference in the secondary wave of the first piezoelectric element 221a and the third piezoelectric element 221c and the phase difference in the secondary wave of the second piezoelectric element 221b and the fourth piezoelectric element 221d are both 180 degrees. The secondary waves of the first piezoelectric element 221a and the third piezoelectric element 221c cancel each other, and the secondary waves of the second piezoelectric element 221b and the fourth piezoelectric element 221d cancel each other. As a result, the secondary wave is eliminated.

  Next, the elimination of the tertiary wave will be described. The first piezoelectric element 221a and the second piezoelectric element 221b are driven so that the phase difference in the tertiary wave of the third piezoelectric element 221c and the fourth piezoelectric element 221d is both 180 degrees.

  The initial phase between the piezoelectric elements is as described above. In the third-order wave, since the wavelength is 1/3, the phase also advances three times. Therefore, the phase of the second piezoelectric element 221b is π, the phase of the third piezoelectric element 221c is 3π / 2, The phase of the fourth piezoelectric element 221d is 15π / 6.

  Therefore, the phase difference in the third order wave of the first piezoelectric element 221a and the second piezoelectric element 221b and the phase difference in the third order wave of the third piezoelectric element 221c and the fourth piezoelectric element 221d are both 180 degrees. The tertiary waves of the first piezoelectric element 221a and the second piezoelectric element 221b cancel each other, and the tertiary waves of the third piezoelectric element 221c and the fourth piezoelectric element 221d cancel each other. As a result, the tertiary wave is eliminated.

  Since the phase relationships of the fundamental waves do not cancel each other, the fundamental waves remain without being canceled after the secondary wave and tertiary wave are canceled. As described above, high-order harmonics included in the transmitted ultrasonic wave are eliminated, and it is possible to generate an ultrasonic wave only of the fundamental wave.

  FIG. 6 is an explanatory diagram for explaining an example of the delay time given to the piezoelectric element 221 of each channel constituting the piezoelectric element group 200.

  The horizontal axis represents the channel numbers of the piezoelectric elements 221 constituting the piezoelectric element group 200, and the vertical axis represents the amount of delay time (nanoseconds) provided for driving each piezoelectric element 221.

  As shown in FIG. 5, 64 piezoelectric elements 221 of each channel constituting the piezoelectric element group 200 are linearly arranged on one plane at the same interval.

  The combination of the first channel to the fourth channel as one piezoelectric element body 220, and then the fifth channel to the eighth channel as one piezoelectric element body 220, there are 16 sets of piezoelectric element bodies 220 in up to 64 channels. Are in parallel.

  The first to fourth channels are the first piezoelectric element 221a, the second piezoelectric element 221b, the third piezoelectric element 221c, and the fourth piezoelectric element 221d, and the fifth to eighth channels are the fourth piezoelectric element 221d and the third piezoelectric element. The piezoelectric element 221c, the second piezoelectric element 221b, and the first piezoelectric element 221a are used.

  Similarly, the ninth to twelfth channels are the first piezoelectric element 221a, the second piezoelectric element 221b, the third piezoelectric element 221c, and the fourth piezoelectric element 221d, and the thirteenth to sixteenth channels are the fourth piezoelectric element 221d. , A third piezoelectric element 221c, a second piezoelectric element 221b, and a first piezoelectric element 221a.

  As shown in FIG. 6, each delay time is added to a line 70 representing the delay time given to the piezoelectric element 221 of each channel for beam forming for collecting ultrasonic waves at the measurement site of the subject. Has been. A delay time to be provided from the first piezoelectric element to the fourth piezoelectric element is given to the delay time represented by the line 70. That is, each piezoelectric element 221 is driven with a delay time set so as to have the phase relationship described above.

  Specifically, the phase of the first piezoelectric element 221a in the fundamental wave is 0, the phase of the second piezoelectric element 221b is π / 3, the phase of the third piezoelectric element 221c is π / 2, and the phase of the fourth piezoelectric element 221d is 5π / 6.

  Note that the ultrasonic waves transmitted from the piezoelectric elements from the first piezoelectric element to the fourth piezoelectric element are placed in close proximity so that the ultrasonic waves themselves interfere as described above. Specifically, it is desirable that the piezoelectric elements from the first piezoelectric element to the fourth piezoelectric element are installed in a proximity state within 5 mm.

  In addition, in order for the ultrasonic waves transmitted from the piezoelectric elements from the first piezoelectric element to the fourth piezoelectric element to effectively interfere with each other and exhibit the effects of the present invention, ten or more sets of piezoelectric element bodies 220 are provided. It is desirable. Moreover, it is desirable that the piezoelectric elements are arranged in a one-dimensional or two-dimensional manner.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these.

  Sixteen sets of piezoelectric element bodies 220 each including a first piezoelectric element to a fourth piezoelectric element were prepared.

  The focus point was set at a position 35 mm away from the ultrasonic probe by beam forming, and it was driven at a fundamental frequency of 4 MHz.

  Table 1 shows the phase relationship from the first piezoelectric element to the fourth piezoelectric element and the relationship between the second harmonic component and the third harmonic component that can be removed by the phase relationship.

  The third harmonic is canceled out by the difference between the ultrasonic waves transmitted from the first piezoelectric element and the second piezoelectric element, and the difference between the ultrasonic waves transmitted from the third piezoelectric element and the fourth piezoelectric element is also used. The third harmonic was canceled out. Further, the second harmonic is obtained by further subtracting the difference between the ultrasonic waves transmitted from the first piezoelectric element and the second piezoelectric element and the difference between the ultrasonic waves transmitted from the third piezoelectric element and the fourth piezoelectric element. The waves were canceled out.

  The obtained results are shown in FIGS. FIG. 7 is an example of measured values of the time waveform of the fundamental wave and the transmission wave according to the present invention. The horizontal axis represents time (μs), and the vertical axis represents the relative intensity of the actually measured ultrasonic waves. A line 81 represents a time waveform of a fundamental wave, and a line 82 represents a time waveform of a transmission wave according to the present invention.

  FIG. 8 is a frequency spectrum of the fundamental wave and the transmission wave according to the present invention. The horizontal axis represents frequency, and the vertical axis represents ultrasonic intensity (dB). The intensity of the ultrasonic wave corresponds to 1 Vrms at 0 dB. Line 91 represents the frequency spectrum of the fundamental wave, and line 92 represents the frequency spectrum of the transmission wave according to the present invention.

  It can be seen from FIG. 8 that the transmission wave of the present invention has a narrow frequency band with respect to the frequency spectrum of the fundamental wave, and second and higher harmonics are attenuated.

  As described above, according to the present embodiment, the piezoelectric element outputs ultrasonic waves of a fundamental wave, an nth order wave (n is a natural number of 2 or more), and an mth order wave (m is a natural number of 2 or more different from n). A piezoelectric element group including four or more piezoelectric elements having the same output characteristics, and the four piezoelectric elements in the piezoelectric element group are grouped from the first piezoelectric element to the fourth piezoelectric element. An ultrasonic probe having at least one body, a transmission means for transmitting the ultrasonic wave to the ultrasonic probe, and an electrical signal obtained by converting the reflected ultrasonic wave from the subject by the ultrasonic probe Receiving means, a harmonic extraction unit for extracting a harmonic component contained in the electrical signal, and an image processing unit for generating an ultrasonic image in the subject from the harmonic component, The transmitting means includes a first piezoelectric element and a third piezoelectric element in each piezoelectric element body. The phase difference in the nth wave of the second piezoelectric element and the phase difference in the nth wave of the fourth piezoelectric element are both 180 degrees, and the phase difference in the mth wave of the first piezoelectric element and the second piezoelectric element is Since the third piezoelectric element and the fourth piezoelectric element are driven so that the phase difference in the m-th order wave is 180 degrees, the n-th order wave and the m-order wave, which are high-order harmonics in the transmission wave, are driven. It is possible to provide an ultrasonic diagnostic apparatus for erasing.

  According to another embodiment, since the first to fourth piezoelectric elements are installed in proximity to each other within 5 mm, the ultrasonic waves transmitted from the respective piezoelectric elements effectively interfere with each other. Therefore, it is possible to provide an ultrasonic diagnostic apparatus that effectively eliminates the n-order wave and the m-order wave, which are high-order harmonics.

  According to another embodiment, ten or more sets of piezoelectric element bodies 220 are provided, and each piezoelectric element is arranged in a one-dimensional shape or a two-dimensional shape, so that it is effectively a high-order harmonic. It is possible to provide an ultrasonic diagnostic apparatus that erases the n-th wave and the m-th wave.

  According to another embodiment, since n is 2 and m is 3, an ultrasonic diagnostic apparatus that effectively eliminates secondary and tertiary waves that are higher harmonics is provided. It becomes possible to do.

DESCRIPTION OF SYMBOLS 1 Ultrasonic diagnostic apparatus main body 2 Ultrasonic probe 4 Ultrasonic probe folder 11 Operation input part 12 Transmission part 13 Reception part 14 Reception signal processing part 15 Image processing part 16 Display part 17 Control part 18 Transmission signal processing part 19 Storage unit 20 Vibrating unit 22 Piezoelectric unit 23 Acoustic matching layer 24 Acoustic lens 25 Backing layer 26 Fixed plate 121 Transmission beamformer 122 Delay pulse generation circuit 123 Delay table storage unit 131 Reception beamformer 132 Phased addition unit 133 Analog-digital converter (ADC) )
134 Low-pass filter 200 Piezoelectric element group 201, 202 Amplifier 220 Piezoelectric element body 221 Piezoelectric element 221a First piezoelectric element 221b Second piezoelectric element 221c Third piezoelectric element 221d Fourth piezoelectric element H Subject S Ultrasonic diagnostic apparatus

Claims (4)

Piezoelectric elements that output ultrasonic waves of fundamental waves, n-order waves (n is a natural number of 2 or more) and m-order waves (m is a natural number of 2 or more different from n), and 4 piezoelectric elements having the same output characteristics An ultrasonic probe comprising at least one piezoelectric element group, and at least one piezoelectric element body in which the four piezoelectric elements in the piezoelectric element group are grouped from the first piezoelectric element to the fourth piezoelectric element. When,
Transmitting means for transmitting ultrasonic waves to the ultrasonic probe;
Receiving means for receiving an electrical signal obtained by converting the reflected ultrasound from the subject by the ultrasound probe;
A harmonic extraction unit for extracting harmonic components contained in the electrical signal;
An image processing unit that generates an ultrasonic image in the subject from the harmonic component, and
In each of the piezoelectric element bodies, the transmission means includes a phase difference in the nth order wave of the first piezoelectric element and the third piezoelectric element and a phase difference in the nth order wave of the second piezoelectric element and the fourth piezoelectric element are both 180 degrees. The phase difference in the m-th order wave of the first piezoelectric element and the second piezoelectric element and the phase difference in the m-th order wave of the third piezoelectric element and the fourth piezoelectric element are both driven to be 180 degrees. A characteristic ultrasonic diagnostic apparatus.   The ultrasonic diagnostic apparatus according to claim 1, wherein the first to fourth piezoelectric elements are installed in a proximity state within 5 mm.   The ultrasonic diagnostic apparatus according to claim 1 or 2, wherein ten or more sets of the piezoelectric element bodies are provided, and each piezoelectric element is arranged one-dimensionally or two-dimensionally.   The ultrasonic diagnostic apparatus according to claim 1, wherein the n is 2 and the m is 3. 5.

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