JP5526009B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention belongs to the technical field of ultrasonic diagnostic apparatuses, and particularly relates to an ultrasonic diagnostic apparatus that can obtain an ultrasonic image having not only spatial resolution but also high depth resolution by using harmonic imaging.

In the medical field, an ultrasonic diagnostic apparatus using an ultrasonic image has been put into practical use.
In general, this type of ultrasonic diagnostic apparatus has an ultrasonic probe with a built-in transducer array and a diagnostic apparatus main body connected to the ultrasonic probe. An ultrasonic image is generated by transmitting an ultrasonic wave toward the subject, receiving an ultrasonic echo from the subject with an ultrasonic probe, and electrically processing the received signal with the diagnostic device body. The

In such ultrasonic diagnosis, Harmonic Imaging is known as a technique for obtaining an ultrasonic image with high spatial resolution (high definition).
Harmonic imaging is a technique for receiving ultrasonic echoes of second and higher harmonics of transmitted ultrasonic waves and converting them into image signals.

  By utilizing such harmonic imaging, it is possible to narrow the received ultrasonic echo beam and obtain an ultrasonic image with high spatial resolution.

However, in harmonic imaging, ultrasonic waves are transmitted on the low frequency side of the frequency band of the piezoelectric element (ultrasonic vibrator) that transmits and receives ultrasonic waves, and harmonics are transmitted on the high frequency side of the frequency band of the piezoelectric element. It must be received. That is, in harmonic imaging, transmission and reception of ultrasonic waves must be performed in a narrow band.
Therefore, in harmonic imaging, the output of ultrasonic waves to be transmitted is small and the amount of harmonics generated is small. Also, with regard to reception, since the band edge of the piezoelectric element must be used, the reception sensitivity is low.
In addition, in harmonic imaging, since transmission and reception must be performed with narrow-band ultrasonic waves, there is a problem that depth resolution deteriorates rather than normal ultrasonic images.

  As described in Patent Document 1 and Patent Document 2, such a problem is caused by piezoelectric ceramics made of inorganic ceramics such as PZT (lead zirconate titanate) that transmits (transmits / receives) ultrasonic waves to the ultrasonic probe. By providing an element and an organic piezoelectric element made of PVDF (polyvinylidene fluoride) or the like for receiving harmonics, the problem can be solved to some extent.

JP 2009-297326 A JP 2009-297327 A

In other words, when performing harmonic imaging, this ultrasonic probe has a configuration in which transmission and reception are separated, and an ultrasonic wave is oscillated using a wide band of an inorganic ceramic piezoelectric element (hereinafter referred to as an inorganic piezoelectric element). Second and higher harmonics can be received using a wide band of the organic piezoelectric element. Accordingly, the depth resolution can be improved by widening the band of ultrasonic waves to be transmitted and received, compared to harmonic imaging in which transmission and reception are performed by the same piezoelectric element.
Furthermore, since the acoustic impedance of the organic piezoelectric body and the second acoustic matching layer in a general two-layer acoustic matching configuration are close, the organic piezoelectric element can also act as an acoustic matching layer as it is.

However, even with an ultrasonic probe that uses an inorganic piezoelectric element for transmission (for transmission and reception) and an organic piezoelectric element for reception, harmonic imaging still does not achieve sufficient depth resolution. .
Therefore, the appearance of an ultrasonic diagnostic apparatus capable of obtaining an ultrasonic image by harmonic imaging with higher depth resolution is desired.

  An object of the present invention is to solve the above-described problems of the prior art, and in an ultrasonic diagnostic apparatus, an ultrasonic image capable of obtaining an ultrasonic image not only with high spatial resolution but also with high depth resolution by harmonic imaging. It is to provide a diagnostic device.

  In order to achieve the above object, an ultrasonic diagnostic apparatus of the present invention includes a plurality of inorganic ceramic piezoelectric bodies that perform transmission and reception of ultrasonic waves, and ultrasonic waves of second or higher harmonics of ultrasonic waves transmitted by the inorganic ceramic piezoelectric bodies. An ultrasonic probe having a plurality of organic piezoelectric bodies that receive acoustic echoes, convert them into electrical signals and output them as image signals, driving means for driving the inorganic ceramic piezoelectric bodies, and output from the organic piezoelectric bodies A diagnostic apparatus main body that processes the processed image signal and generates an ultrasonic image, and the drive means resonates with the inorganic ceramic piezoelectric body when the organic piezoelectric body outputs the image signal. The inorganic ceramics piezoelectric body is driven by a rectangular wave driving voltage waveform generated by selecting three or more waves from the characteristic waveform in descending order of wave height intensity and approximating the wave height intensity to be equal. To provide an ultrasonic diagnostic apparatus.

In such an ultrasonic diagnostic apparatus of the present invention, it is preferable that the wave number to be selected is 5 or less.
At this time, when the wave height intensity of the selected wave is Vp and the intensity of the point where the drive voltage waveform of the rectangular wave intersects with the selected wave is Vx, “crossing intensity = Vx / Vp”. The driving voltage waveform is a rectangular driving voltage waveform generated by selecting 5 waves from the resonance characteristic waveform in descending order of wave height intensity and generating the intersection intensity of 0.33 to 0.8. Preferably, the driving voltage waveform is a rectangular driving voltage waveform generated so that the intersection strength is 0.66 to 0.8.
Alternatively, when the wave height intensity of the selected wave is Vp and the intensity at the point where the drive voltage waveform of the rectangular wave intersects the selected wave is Vx, the driving voltage is set to “crossing intensity = Vx / Vp”. It is preferable that the waveform is a rectangular drive voltage waveform generated by selecting four waves from the resonance characteristic waveform in descending order of the wave height intensity and generating an intersection intensity of 0.33 to 0.8.
Alternatively, when the wave height intensity of the selected wave is Vp and the intensity at the point where the drive voltage waveform of the rectangular wave intersects the selected wave is Vx, the driving voltage is set to “crossing intensity = Vx / Vp”. It is preferable that the waveform is a rectangular drive voltage waveform generated by selecting three waves from the resonance characteristic waveform in descending order of wave height intensity so that the crossing intensity is 0.5 to 0.8.

  In the ultrasonic diagnostic apparatus of the present invention, it is preferable that the organic piezoelectric element functions as a second acoustic matching layer of the ultrasonic probe.

The ultrasonic diagnostic apparatus of the present invention having the above-described configuration has a frequency band of a piezoelectric element made of inorganic ceramics for transmission (for transmission / reception in normal ultrasonic diagnosis) when performing ultrasonic diagnosis by harmonic imaging. An ultrasonic wave can be transmitted using the entire region (at least -6 dB band or more).
Alternatively, when performing ultrasonic diagnosis by harmonic imaging, an ultrasonic image can be obtained by receiving ultrasonic echoes of second and higher harmonics in a wide frequency band by a receiving organic piezoelectric element.

  Therefore, according to the present invention, not only high spatial resolution (high-definition ultrasonic image), which is a characteristic of harmonic imaging, but also depth resolution (distance resolution) can be improved by ultrasonic waves in a wide frequency band. Ultrasonic images can be obtained with spatial resolution and high depth resolution (high depth / high penetration).

It is a block diagram which shows an example of the ultrasonic diagnosing device of this invention. It is a figure which shows notionally an example of a structure of the ultrasonic transducer used for the ultrasonic diagnosing device of this invention. (A) And (B) is a graph for demonstrating transmission of the ultrasonic wave in the ultrasonic diagnosing device of this invention. It is a graph for demonstrating a center frequency and a specific band.

  Hereinafter, the ultrasonic diagnostic apparatus of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 is a block diagram conceptually showing an example of the ultrasonic diagnostic apparatus of the present invention.
An ultrasonic diagnostic apparatus 10 shown in FIG. 1 includes a rechargeable ultrasonic probe (ultrasonic probe) 12 and a diagnostic apparatus main body 14 connected to the ultrasonic probe 12 by wireless communication.

The ultrasonic probe 12 (hereinafter referred to as the probe 12) has a plurality of ultrasonic transducers 18 (hereinafter referred to as transducers 18) constituting a one-dimensional or two-dimensional transducer array. A reception signal processing unit 20 is connected to each of these transducers 18, and a wireless communication unit 26 is connected to the reception signal processing unit 20 via a parallel / serial conversion unit 24.
In addition, a transmission control unit 30 is connected to each transducer 18 via a transmission drive unit 28, a reception control unit 32 is connected to each reception signal processing unit 20, and a communication control unit 34 is connected to the wireless communication unit 26. ing. A probe controller 36 is connected to the parallel / serial converter 24, the transmission controller 30, the reception controller 32, and the communication controller 34.
Further, a battery 40 is connected to the probe control unit 36 via a battery control unit 38, and a power receiving unit 42 for charging is connected to the battery 40. Electric power for driving the probe 12 is supplied from the battery 40 to each part.

  The transducer 18 transmits an ultrasonic wave according to the drive signal supplied from the transmission drive unit 28, receives an ultrasonic echo from the subject, converts it to an electrical signal, and outputs a reception signal of the ultrasonic image.

FIG. 2 conceptually shows the configuration of the transducer 18.
In the illustrated example, as an example, the transducer 18 includes a backing layer 48, an inorganic ceramic piezoelectric element 50 (hereinafter referred to as an inorganic piezoelectric element 50), a first acoustic matching layer 52, an organic piezoelectric element 54, and an acoustic lens 56. And is configured.

  The backing layer 48 is made of a material that absorbs ultrasonic waves, and absorbs ultrasonic waves transmitted from the inorganic ceramics piezoelectric element 50 and directed to the opposite side of the subject (that is, the backing layer 48). It is.

The inorganic piezoelectric element 50 is formed by sandwiching an inorganic ceramic piezoelectric material (piezoelectric ceramic) represented by PZT (lead zirconate titanate) between electrodes.
When the inorganic piezoelectric element 50 is supplied with a pulsed drive voltage from the transmission drive unit 28, the piezoelectric element expands and contracts to transmit pulsed ultrasonic waves. A plurality of ultrasonic waves are combined to form an ultrasonic beam.
Further, the inorganic piezoelectric element 50 vibrates by receiving an ultrasonic echo from a subject in a normal ultrasonic diagnosis (when harmonic imaging is not performed), and corresponds to the intensity of the received ultrasonic echo. Generate electrical signals. This electrical signal is output to the received signal processing unit 20 as a received signal.

  In addition to PZT, lithium niobate, potassium niobate tantalate, barium titanate, lithium tantalate, strontium titanate, and the like can be used as the inorganic piezoelectric element 50.

The first acoustic matching layer 52 matches the acoustic impedance between the inorganic piezoelectric element 50 and the organic piezoelectric element 54.
The first acoustic matching layer 52 may be formed of a known material that can achieve acoustic impedance matching according to the material for forming the inorganic piezoelectric element 50 and the organic piezoelectric element 54.

The organic piezoelectric element 54 is formed by sandwiching an organic polymer piezoelectric material typified by PVDF (polyvinylidene fluoride) or P (VDF / Tr-FE) between electrodes.
As described above, when performing harmonic imaging, an ultrasonic image of the second or higher harmonic wave of the ultrasonic wave transmitted to the subject is received to obtain an ultrasonic image. The organic piezoelectric element 54 vibrates by receiving a harmonic ultrasonic echo from a subject when performing ultrasonic diagnosis by harmonic imaging, and generates an electric signal corresponding to the intensity of the received ultrasonic echo. Occur. This electrical signal is also output to the reception signal processing unit 20 as a reception signal.
In the ultrasonic diagnostic apparatus 10 of the present invention, when making a diagnosis by harmonic imaging, a configuration in which transmission / reception of ultrasonic waves is separated makes it possible to widely use a band of the organic piezoelectric element 54 and to perform secondary or higher-order. Receives harmonics and improves depth resolution.

Here, the organic piezoelectric body is close to the acoustic impedance of the second acoustic matching layer (side closer to the human body) in an ultrasonic transducer having a general two-layer acoustic matching configuration.
Therefore, in the transducer 18 of the illustrated example, the organic piezoelectric element 54 performs the acoustic impedance matching between the inorganic piezoelectric element 50 and the subject and the acoustic impedance matching between the subject and the organic piezoelectric element 54 itself. Also acts as a two acoustic matching layer.
However, the present invention is not limited to this configuration, and a second acoustic matching layer may be separately provided between the organic piezoelectric element 54 and the acoustic lens 56 as necessary.

The acoustic lens 56 is a member that converges the ultrasonic waves transmitted toward the subject.
In the illustrated example, the acoustic lens 56 is arranged for each transducer 18, but in reality, one acoustic lens 56 is provided so as to cover all the transducers 18.

The transmission drive unit 28 includes, for example, a plurality of pulsers, and supplies the drive voltage to the inorganic piezoelectric element 50 of each transducer 18 to vibrate the inorganic piezoelectric element 50 and transmit ultrasonic waves.
Here, in the ultrasonic diagnostic apparatus 10 of the present invention, when performing diagnosis by harmonic imaging, the transmission drive unit 28 drives a predetermined rectangular wave created by approximating the resonance characteristic waveform of the inorganic piezoelectric element 50. A drive voltage is supplied to the inorganic piezoelectric element 50 according to the voltage waveform.
By having such a configuration, the present invention transmits ultrasonic waves using almost the entire region of the band of the inorganic piezoelectric element 50, and widely uses the band of the organic piezoelectric element 54 to obtain a secondary or higher order. In addition to the high spatial resolution characteristic of harmonic imaging, the depth resolution can be improved by ultrasonic waves in a wide frequency band. This will be described in detail later.

In the ultrasonic diagnostic apparatus 10 of the present invention, when performing normal ultrasonic diagnosis (generation of an ultrasonic image) that is not diagnosis by harmonic imaging, the transmission drive unit 28 is a known ultrasonic diagnostic apparatus. The inorganic piezoelectric element 50 is driven according to the pulse-shaped drive waveform signal of normal 1 wave or 2 waves or more performed in the above.
Alternatively, the transmission drive unit 28 may be driven according to a rectangular drive voltage waveform approximating the resonance characteristic waveform of the inorganic piezoelectric element 50 in the normal ultrasonic diagnosis as well as in harmonic imaging.
Further, a normal known method for driving the inorganic piezoelectric element 50 and a method for driving the inorganic piezoelectric element 50 approximating the resonance characteristic waveform may be selectable.

  Further, the transmission drive unit 28 generates a wide ultrasonic beam in which the ultrasonic waves transmitted from the plurality of transducers 18 cover the tissue area in the subject based on the transmission delay pattern selected by the transmission control unit 30. The delay amount of each drive signal is adjusted so as to be formed and supplied to the plurality of transducers 18.

The reception signal processing unit 20 generates a complex baseband signal by performing quadrature detection processing or quadrature sampling processing on the reception signal output from the corresponding transducer 18 under the control of the reception control unit 32. By sampling the band signal, sample data including information on the tissue area is generated, and the sample data is supplied to the parallel / serial converter 24. The reception signal processing unit 20 may generate sample data by performing data compression processing for high-efficiency encoding on data obtained by sampling a complex baseband signal.
The parallel / serial conversion unit 24 converts the parallel sample data generated by the reception signal processing unit 20 of a plurality of channels into serial sample data.

The wireless communication unit 26 modulates a carrier based on serial sample data to generate a transmission signal, supplies the transmission signal to the antenna, and transmits radio waves from the antenna, thereby transmitting serial sample data.
As the modulation scheme, for example, ASK (Amplitude Shift Keying), PSK (Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (16 Quadrature Amplitude Modulation), and the like are used.

The wireless communication unit 26 performs wireless communication with the diagnostic device main body 14 to transmit sample data to the diagnostic device main body 14 and to receive various control signals from the diagnostic device main body 14. The control signal is output to the communication control unit 34.
The communication control unit 34 controls the wireless communication unit 26 so that the sample data is transmitted with the transmission radio wave intensity set by the probe control unit 36, and also receives various control signals received by the wireless communication unit 26. It outputs to the probe control part 36.

The probe control unit 36 controls each part of the probe 12 based on various control signals transmitted from the diagnostic apparatus main body 14.
The battery 40 functions as a power source for the probe 12 and supplies power to each part that requires power in the probe 12. The battery control unit 38 controls power supply from the battery 40 to each part in the probe 12.

  In the present invention, the probe 12 may be an external probe such as a linear scan method, a convex scan method, or a sector scan method, or may be a probe for an ultrasonic endoscope such as a radial scan method. .

On the other hand, the diagnostic apparatus main body 14 includes a wireless communication unit 60, a data storage unit 64 is connected to the wireless communication unit 60 via a serial / parallel conversion unit 62, and an image generation unit 68 is connected to the data storage unit 64. Has been. Further, a display unit 72 is connected to the image generation unit 68 via the display control unit 70.
A communication control unit 74 is connected to the wireless communication unit 60, and a main body control unit 76 is connected to the serial / parallel conversion unit 62, the image generation unit 68, the display control unit 70, and the communication control unit 74. Connected to the main body control unit 76 are an operation unit 78 for an operator to perform an input operation and a storage unit 80 for storing an operation program.

A power supply unit 84 is connected to the main body control unit 76 via a power supply control unit 82.
Furthermore, a probe holder 86 for holding the probe 12 when not in use is formed in the diagnostic apparatus main body 14, and a power feeding unit 90 is disposed on the probe holder 86.

The wireless communication unit 60 transmits various control signals to the probe 12 by performing wireless communication with the probe 12. The wireless communication unit 60 also outputs serial sample data by demodulating a signal received by the antenna.
The communication control unit 74 controls the wireless communication unit 60 so that various control signals are transmitted with the transmission radio wave intensity set by the main body control unit 76.
The serial / parallel converter 62 converts the serial sample data output from the wireless communication unit 60 into parallel sample data. The data storage unit 64 is configured by a memory, a hard disk, or the like, and stores at least one frame of sample data converted by the serial / parallel conversion unit 62.

The image generation unit 68 performs reception focus processing on the sample data for each frame read from the data storage unit 64 to generate an image signal representing an ultrasonic diagnostic image. The image generation unit 68 includes a phasing addition unit 92 and an image processing unit 94.
The phasing addition unit 92 selects one reception delay pattern from a plurality of reception delay patterns stored in advance according to the reception direction set in the main body control unit 76, and sets the selected reception delay pattern to the selected reception delay pattern. Based on this, the reception focus process is performed by adding a delay to each of the plurality of complex baseband signals represented by the sample data. By this reception focus processing, a baseband signal (sound ray signal) in which the focus of the ultrasonic echo is narrowed is generated.

The image processing unit 94 generates a B-mode image signal that is tomographic image information regarding the tissue in the subject based on the sound ray signal generated by the phasing addition unit 92.
The image processing unit 94 includes an STC (sensitivity time control) unit and a DSC (digital scan converter). The STC unit corrects the attenuation due to the distance according to the depth of the reflection position of the ultrasonic wave on the sound ray signal. On the other hand, the DSC converts the sound ray signal corrected by the STC unit into an image signal in accordance with a normal television signal scanning method (raster conversion), and performs necessary image processing such as gradation processing to perform the B mode. An image signal is generated.

The display control unit 70 causes the display unit 72 to display an ultrasound diagnostic image based on the image signal generated by the image generation unit 68.
The display unit 72 includes a display device such as an LCD, for example, and displays an ultrasound diagnostic image under the control of the display control unit 70.

The main body control unit 76 controls each unit in the diagnostic apparatus main body 14.
The power supply unit 84 supplies power to each unit that requires power in the diagnostic apparatus main body 14. The power supply control unit 82 connects the power supply unit 84 to the power supply unit 90 of the probe holder 86 as necessary in accordance with the inspection status or the like by the diagnostic apparatus main body 14 input via the main body control unit 76, and The battery 40 of the child 12 is charged. The power supply unit 90 of the probe holder 86 supplies power to the power receiving unit 42 of the probe 12 held by the probe holder 86 in a non-contact manner by electromagnetic induction or the like.

  In such a diagnostic apparatus main body 14, the serial / parallel conversion unit 62, the image generation unit 68, the display control unit 70, the communication control unit 74, the main body control unit 76, and the power supply control unit 82 include a CPU and various processes for the CPU. However, they may be composed of digital circuits. The operation program is stored in the storage unit 80. As a recording medium in the storage unit 80, a flexible disk, MO, MT, RAM, CD-ROM, DVD-ROM or the like can be used in addition to the built-in hard disk.

As described above, when the ultrasonic diagnostic apparatus 10 of the present invention performs ultrasonic diagnosis (generation of an ultrasonic image) by harmonic imaging, the frequency used for harmonic imaging is the maximum output frequency of the inorganic piezoelectric element 50 (that is, Center frequency), and driving of the inorganic piezoelectric element 50 of the transducer 18 is performed by a rectangular driving voltage waveform generated by approximating the resonance characteristic waveform of the inorganic piezoelectric element 50.
Specifically, the frequency used for harmonic imaging is set to the maximum output frequency of the inorganic piezoelectric element 50, and three or more waves are selected from the resonance characteristic waveform of the inorganic piezoelectric element 50 in descending order of the wave height intensity. The inorganic piezoelectric element 50 is driven by a rectangular driving voltage waveform generated by approximation so as to be equal.

In the present invention, during harmonic imaging, transmission is performed by driving the inorganic piezoelectric element 50 such as PZT with the drive voltage waveform of the predetermined rectangular wave, so that almost all of the inorganic piezoelectric element 50 has. An ultrasonic wave can be transmitted using a frequency band (at least -6 dB band).
In addition, by receiving the higher-order ultrasonic echoes of the second and higher harmonics by the ultrasonic wave of such a wide band by the organic piezoelectric element 54 for receiving the harmonic wave, it corresponds to the ultrasonic echoes of the higher-frequency harmonics. Thus, a highly sensitive received signal can be output.
Therefore, according to the ultrasonic diagnostic apparatus 10 of the present invention, depth resolution (distance resolution (time resolution)) is achieved by transmitting and receiving ultrasonic waves in a wide frequency band as well as high spatial resolution that is a characteristic of harmonic imaging. The ultrasonic image can be created with high spatial resolution and depth resolution.

FIG. 3A shows an example of the resonance characteristic waveform (PF data) of the inorganic piezoelectric element 50. This example shows a resonance characteristic waveform when PZT is used as the inorganic piezoelectric element 50 and driven with a pulse voltage having a flat frequency characteristic at a frequency of Fc / 10 to Fc * 2 with respect to the center frequency Fc.
The resonance waveform characteristic of the inorganic piezoelectric element 50 can be obtained from each frequency response when the burst wave voltage of the same level is frequency-subtracted (generally called VTG (Voltage Transfer Gain)). ing).
In the present invention, three or more waves are selected from the resonance characteristic waveform (solid line) in descending order of the wave height intensity. In the example shown in FIG. 3, five waves are selected.
Next, a rectangular wave driving voltage waveform (broken line) is generated by approximating the selected waves so that the wave height intensities are equal, and the inorganic piezoelectric element 50 is driven by this driving voltage waveform. In the example shown in FIG. 3 (A), five waves of high wave high intensity selected from the resonance characteristic waveform intersect at a position of 1/2 intensity (intersection intensity 0.5 described later) and are equal in height. A rectangular drive voltage waveform having five pulse signals is generated.

Here, in order to vibrate the inorganic piezoelectric element 50 in a wide frequency band, the inorganic piezoelectric element indicated by a broken line with respect to the spectrum data (PZT frequency band curve) of the inorganic piezoelectric element 50 indicated by the solid line in FIG. It is preferable to match the spectrum data of the drive voltage waveform of the element 50 as much as possible.
By matching both spectrum data, it is possible to resonate the inorganic piezoelectric element 50 without waste, and to transmit ultrasonic waves using a wide frequency band of the inorganic piezoelectric element 50.

  According to the study by the present inventors, from the resonance characteristic waveform of the inorganic piezoelectric element 50, three or more waves, particularly four or more waves, having a high wave height are selected, and a drive voltage waveform approximated to have the same wave height is obtained. By generating, the spectrum data of the inorganic piezoelectric element 50 and the drive voltage waveform can be matched appropriately, and ultrasonic waves can be transmitted using the wide frequency band of the inorganic piezoelectric element 50.

Here, the spectrum data of the drive voltage waveform of the inorganic piezoelectric element 50 depends on the number of waves selected from the resonance characteristic waveform of the inorganic piezoelectric element 50 and the intensity with which the rectangular waveform is approximated with respect to the selected wave. Is adjustable.
That is, as shown in FIG. 3A, when the wave height intensity Vp of the selected wave, the intensity at the position where the rectangular wave driving waveform signal intersects the selected wave is Vx, and “crossing intensity = Vx / Vp”. Further, by appropriately combining the number of waves to be selected and the crossing intensity, the spectrum data of the inorganic piezoelectric element 50 and the spectrum data of the drive voltage waveform of the inorganic piezoelectric element 50 are suitably matched, and the inorganic piezoelectric element 50 It is possible to transmit ultrasonic waves using a wide frequency band.

In particular, by selecting three waves, the driving voltage waveform approximated so that the peak intensity becomes equal with the crossing intensity set to 0.5 to 0.8;
Drive voltage waveform approximated so that the wave height intensity is equal by selecting four waves and setting the crossing intensity to 0.33 to 0.8;
And a driving voltage waveform approximated so that the wave height intensity becomes equal by selecting the 5 waves and setting the crossing intensity to 0.33 to 0.8;
By driving the inorganic piezoelectric element 50 using any of the above, spectrum data is preferably matched with the inorganic piezoelectric element 50 and the drive voltage waveform, and ultrasonic waves are generated using the wide frequency band of the inorganic piezoelectric element 50. Can be sent.

  The degree of coincidence of the spectrum data between the inorganic piezoelectric element 50 and the drive voltage waveform can be evaluated by looking at the degree of coincidence of the -6 dB center frequency, -6 dB ratio band, and maximum intensity value of the spectrum data.

Here, −6 dB means half value.
That is, since the intensity is a voltage value [V], when it is expressed in [dB], it takes 20 times the common logarithm, that is, “20 * log (V)”. Therefore, the half value is 20 * log (1/2) ≈20 * (− 0.3) ≈−6 [dB].

As conceptually shown in FIG. 4, the −6 dB center frequency Fc of the spectrum data is an intermediate value between the lower frequency Fl and the higher frequency Fh at an intensity 6 dB lower than the maximum intensity. That is,
−6 dB center frequency Fc = (Fl + Fh) / 2
Further, the −6 dB ratio band BW of the spectrum data is a bandwidth with respect to the center frequency at an intensity 6 dB lower than the maximum intensity, and is a value obtained by dividing the bandwidth at −6 dB by the center frequency. That is,
−6 dB ratio band BW = (Fh−Fl) / Fc = 2 (Fh−Fl) / (Fl + Fh)

With respect to the resonance characteristic waveform of the inorganic piezoelectric element 50 shown in FIG. 3A, the number N of selected waves and the crossing intensity are variously changed to generate a rectangular drive voltage waveform that approximates this resonance characteristic waveform. Then, the coincidence rate of the −6 dB center frequency of the spectrum data between the inorganic piezoelectric element 50 and the generated drive voltage waveform was calculated using the following formula. In the equation below, Fc _e at -6dB center frequency of the inorganic piezoelectric element, Fc _d is -6dB center frequency of the drive voltage waveform.
−6 dB center frequency match rate [%] = 100 × {1− (| Fc _d −Fc _e | / F c _e )}

The results are shown in the table below.

In order to match the spectrum data of the inorganic piezoelectric element 50 and the drive voltage waveform, the coincidence rate of the −6 dB center frequency is preferably more than 95%. Therefore, a combination of the wave number N and the crossing intensity in the region indicated by the bold line is preferable.

Similarly, for the resonance characteristic waveform of the inorganic piezoelectric element 50 shown in FIG. 3, the coincidence ratio of the −6 dB ratio band of the spectrum data of the inorganic piezoelectric element 50 and the generated drive voltage waveform is calculated using the following equation. did. In the following formula, BW _e is a −6 dB ratio band of the inorganic piezoelectric element, and BW _d is a −6 dB ratio band of the drive voltage waveform.
−6 dB ratio band matching rate [%] = 100 × {1− (| BW _d −BW _e | / BW _e )}

The results are shown in the table below.

In order to match the spectrum data of the inorganic piezoelectric element 50 and the drive voltage waveform, the matching rate of the −6 dB ratio band is preferably 75% or more. Therefore, a combination of the wave number N and the crossing intensity in the region indicated by the bold line is preferable.

Further, for the resonance characteristic waveform shown in FIG. 3, the maximum intensity values after spectrum conversion of the spectrum data of the inorganic piezoelectric element 50 and the generated drive voltage waveform were compared in the same manner. The higher the intensity value, the more efficiently the inorganic piezoelectric element 50 can be driven.
The comparison was made with the result of each condition with the intensity at wave number N = 8 and crossing intensity 1.00 as a reference.

The results are shown in the table below.

In order to match the spectrum data of the inorganic piezoelectric element 50 and the drive voltage waveform, the ratio of the maximum intensity value after the spectrum conversion is preferably more than -6 dB. Therefore, a combination of the wave number N and the crossing intensity in the region indicated by the bold line is preferable.

The above-mentioned center frequency coincidence rate, −6 dB ratio band coincidence rate, and intensity ratio are all in the preferred range in the combination indicated by “OK” in the following table, that is, the region indicated by the bold line. .

Here, even at a wave number of 8, all elements fall within a preferable range in combination with the intersection strength of 0.33 to 1.00. On the other hand, considering the burden on the apparatus, it is advantageous that the number of driving voltage waveforms is small.
When the wave number 8 and the wave number 5 are compared, there is almost no difference in the coincidence ratio among the −6 dB center frequency, the −6 dB ratio band, and the intensity ratio. Driving the inorganic piezoelectric element 50 once with a drive voltage waveform having eight waves places a heavy burden on the transmission drive unit 28 (driver of the inorganic piezoelectric element 50), and the pulsar and the like are expensive devices. Is required. Moreover, the driving voltage waveform of the inorganic piezoelectric element 50 having a large wave number is disadvantageous also in terms of heat generation of the probe 12.
In addition, the fact that there is no significant difference between the wave number 8 and the wave number 5 means that there is no significant difference between the wave number 6 and the wave number 7 (theoretically, the difference is the wave number 8 or less).
Therefore, the wave number N is preferably 5 or less.

  That is, as shown in the above table, select 3 waves and set the crossing strength to 0.5 to 0.8, or select 4 waves and set the crossing strength to 0.33 to 0.8, Alternatively, by selecting 5 waves, setting the crossing intensity to 0.33 to 0.8, and driving the inorganic piezoelectric element 50 with a rectangular driving voltage waveform approximated to have the same peak intensity, the transmission driving unit Without burdening 28, it is possible to appropriately match the spectrum data between the inorganic piezoelectric element 50 and the drive voltage waveform using an inexpensive device, and to transmit ultrasonic waves using the wide frequency band of the inorganic piezoelectric element 50. .

Here, in order to better match the spectrum data between the inorganic piezoelectric element 50 and the drive voltage waveform, the coincidence rate of the −6 dB center frequency and the coincidence rate of the −6 dB ratio band are over 95%, and the intensity ratio is − More preferably, it is greater than 3 dB.
This condition is satisfied by an area indicated by a thick line in the following table. When the wave number is 5 or less, the wave intensity is 5 and the crossing intensity is 0.66 to 0.8.

Therefore, in the present invention, the inorganic piezoelectric element 50 is driven by a rectangular driving voltage waveform, in which five waves are selected, the crossing intensity is 0.66 to 0.8, and the wave height intensity is approximated to be equal. Is particularly preferred.

  The above example is a case where PZT is used as the inorganic piezoelectric element 50. However, according to the study of the present inventor, the electromechanical coupling constant is approximately 0.65 or more even in other inorganic ceramic piezoelectric materials. Almost the same result can be obtained. Generally, the electromechanical coupling constant of a medical ultrasonic transducer array is generally designed to be 0.65 or more.

Hereinafter, an example of the operation of the ultrasonic diagnostic apparatus 10 will be described.
In the ultrasonic diagnostic apparatus 10, at the time of diagnosis by harmonic imaging, first, ultrasonic waves are transmitted from the plurality of transducers 18 (inorganic piezoelectric elements 50) according to the drive voltage supplied from the transmission drive unit 28 of the probe 12.
This ultrasonic wave is reflected by the subject, and the received signal output from each transducer 18 (organic piezoelectric element 54) that has received an ultrasonic echo of the second or higher harmonic from the subject corresponds to the received signal processing respectively. Sample data is generated by being supplied to the unit 20, serialized by the parallel / serial conversion unit 24, and then wirelessly transmitted from the wireless communication unit 26 to the diagnostic apparatus main body 14.

  Here, since the transducer 18 is driven by a predetermined rectangular drive voltage waveform that approximates the resonance characteristic waveform of the inorganic piezoelectric element 50 as described above, the frequency band of the inorganic piezoelectric element 50 is transmitted. The ultrasonic wave of almost the whole area. In addition, since the dedicated organic piezoelectric element 54 for receiving the harmonics receives the ultrasonic echoes of the second and higher harmonics, high-sensitivity reception corresponding to the harmonic ultrasonic echoes in a wide frequency band. A signal can be output.

Sample data received by the wireless communication unit 60 of the diagnostic apparatus main body 14 is converted into parallel data by the serial / parallel conversion unit 62 and stored in the data storage unit 64.
Further, sample data for each frame is read from the data storage unit 64, an image signal is generated by the image generation unit 68, and an ultrasonic diagnostic image is displayed on the display unit 72 by the display control unit 70 based on this image signal. Is done.
As described above, since this image is an image obtained by receiving ultrasonic echoes of ultrasonic waves in a wide frequency band by the dedicated organic piezoelectric element 54 for receiving harmonics, the harmonic imaging has Not only high spatial resolution, which is a feature but also ultrasonic waves in a wide frequency band, the resolution can be improved in the depth direction, and an ultrasonic image can be obtained with high spatial resolution and depth resolution.

The above example is an example in which the ultrasonic diagnostic apparatus of the present invention is used in an apparatus in which the probe 12 and the diagnostic apparatus main body 14 are wirelessly connected. However, the present invention is not limited to this, and the probe is not limited thereto. The present invention can also be suitably used for an ultrasonic diagnostic apparatus in which the touch element 12 and the diagnostic apparatus main body 14 are connected by wire.
In the case of an ultrasonic diagnostic apparatus in which the probe 12 and the diagnostic apparatus main body 14 are connected by wire, the transmission drive unit 28 and / or the received signal processing unit 20 are not the probe 12 but the diagnostic apparatus. It may be arranged on the main body 14.
The above description is an example in which the ultrasonic diagnostic apparatus of the present invention is used in an apparatus for performing ultrasonic diagnosis by tissue harmonic imaging. However, the present invention is not limited to this, and contrast using a contrast agent is used. It can also be suitably used for an apparatus that performs harmonic imaging.

  It can be suitably used for ultrasonic diagnosis using harmonic imaging in a medical field.

DESCRIPTION OF SYMBOLS 10 Ultrasonic diagnostic apparatus 12 (Ultrasound) probe 14 Diagnostic apparatus main body 18 Transducer 20 Reception signal processing part 24 Parallel / serial conversion part 26 Wireless communication part 28 Transmission drive part 30 Transmission control part 32 Reception control part 34 Communication control part 36 probe control unit 38 battery control unit 40 battery 42 power receiving unit 48 backing layer 50 inorganic (ceramics) piezoelectric element 52 first acoustic matching layer 54 organic piezoelectric material 56 acoustic lens 60 wireless communication unit 62 serial / parallel conversion unit 64 data Storage unit 68 Image generation unit 70 Display control unit 72 Display unit 74 Communication control unit 76 Main body control unit 78 Operation unit 80 Storage unit 82 Power supply control unit 84 Power source unit 86 Probe holder 90 Power supply unit 92 Phase adjusting and adding unit 94 Image processing unit

Claims (6)

Multiple inorganic ceramic piezoelectric materials that transmit and receive ultrasonic waves, and ultrasonic echoes of the second and higher harmonics of ultrasonic waves transmitted by inorganic ceramic piezoelectric materials are received, converted into electrical signals, and output as image signals An ultrasonic probe having a plurality of organic piezoelectric bodies,
Driving means for driving the inorganic ceramic piezoelectric material;
A diagnostic apparatus main body that processes an image signal output from the organic piezoelectric body and generates an ultrasonic image;
In addition, when the organic piezoelectric body outputs an image signal, the driving means selects three or more waves in order of increasing wave height from the resonance characteristic waveform of the inorganic ceramic piezoelectric body, and the wave height intensity becomes equal. An ultrasonic diagnostic apparatus, wherein the inorganic ceramic piezoelectric body is driven by a rectangular driving voltage waveform generated by approximation.   The ultrasonic diagnostic apparatus according to claim 1, wherein the wave number to be selected is 5 or less. When the wave height intensity of the selected wave is Vp, the intensity at the point where the drive voltage waveform of the rectangular wave intersects the selected wave is Vx, and “crossing intensity = Vx / Vp”,
The drive voltage waveform is a rectangular drive voltage waveform generated by selecting five waves in descending order of wave height intensity from the resonance characteristic waveform and generating the intersection intensity of 0.33 to 0.8. An ultrasonic diagnostic apparatus according to 1.   The ultrasonic diagnostic apparatus according to claim 3, wherein the driving voltage waveform is a rectangular driving voltage waveform generated so that the crossing intensity is 0.66 to 0.8. When the wave height intensity of the selected wave is Vp, the intensity at the point where the drive voltage waveform of the rectangular wave intersects the selected wave is Vx, and “crossing intensity = Vx / Vp”,
The drive voltage waveform is a rectangular drive voltage waveform generated by selecting four waves in descending order of wave height intensity from the resonance characteristic waveform and generating an intersection intensity of 0.33 to 0.8. The ultrasonic diagnostic apparatus as described. When the wave height intensity of the selected wave is Vp, the intensity at the point where the drive voltage waveform of the rectangular wave intersects the selected wave is Vx, and “crossing intensity = Vx / Vp”,
The drive voltage waveform is a rectangular wave drive voltage waveform generated by selecting three waves in descending order of wave height intensity from the resonance characteristic waveform and generating an intersection intensity of 0.5 to 0.8. The ultrasonic diagnostic apparatus as described.