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DESCRIPTION JP2009273784

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DESCRIPTION JP2009273784
The present invention provides an ultrasonic diagnostic apparatus that performs correlation
processing by setting a reference signal in accordance with the order of harmonics to be
detected, the diagnostic site of a subject, and the diagnostic depth of the subject. An ultrasonic
diagnostic apparatus S according to the present invention includes a transmitter 12 for
transmitting a first ultrasonic signal into a subject, a receiver 13 for receiving ultrasonic waves,
and a receiver 13 And an image processing unit 15 for forming an image of the inside of the
subject based on the reception of the second ultrasound signal from the inside of the subject
based on the first ultrasound signal, And a correlation unit for detecting a second ultrasound
signal from the output of the reception unit 13 by performing correlation processing between
the output of the unit 13 and a preset reference signal, the reference signal being a signal of the
first ultrasound signal. The frequency is set in accordance with the order of harmonics to be
detected, the diagnostic region of the subject, and the diagnostic depth of the subject when the
frequency is a fundamental frequency. [Selected figure] Figure 2
Ultrasonic diagnostic equipment
[0001]
The present invention transmits a first ultrasonic signal into a subject and receives a second
ultrasonic signal from within the subject based on the first ultrasonic signal and receives the
second ultrasound signal based on the second ultrasonic signal. The present invention relates to
an ultrasonic diagnostic apparatus for forming an image in a subject, and in particular, when the
frequency of the first ultrasonic signal is a fundamental frequency, the image in the subject is
formed based on harmonic components of the second ultrasonic signal. Related to an ultrasonic
diagnostic apparatus.
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[0002]
Ultrasound generally refers to sound waves of 16000 Hz or higher, and can be inspected
nondestructively, harmlessly, and in near real time, and is therefore applied to various fields such
as inspection of defects and diagnosis of diseases.
One of them is an ultrasonic wave which scans the inside of a subject with ultrasound and images
the internal state inside the subject based on a reception signal generated from a reflected wave
(echo) of the ultrasound coming from inside the subject. There is a diagnostic device. This
ultrasonic diagnostic device is small and inexpensive compared to other medical imaging devices
for medical use, and there is no radiation exposure such as X-rays and high safety, and a blood
flow to which the Doppler effect is applied It has various features, such as display capability. For
this reason, the ultrasound diagnostic apparatus includes a circulatory system (for example,
coronary arteries of the heart), a digestive system (for example, the gastrointestinal tract), an
internal medicine system (for example, liver, pancreas and spleen), a urinary system (for example,
kidney and bladder) And widely used in obstetrics and gynecology. In the ultrasonic diagnostic
apparatus, an ultrasonic probe that transmits and receives ultrasonic waves (ultrasound signals)
to and from a subject is used. The ultrasonic probe mechanically vibrates based on the
transmission electric signal to generate an ultrasonic wave (ultrasound signal) by utilizing the
piezoelectric phenomenon, and an ultrasonic impedance generated inside the object due to a
mismatch of the acoustic impedance. A plurality of piezoelectric elements for receiving a
reflected wave of an acoustic wave (ultrasound signal) to generate an electric signal of reception,
and the plurality of piezoelectric elements are two-dimensionally arranged in an array, for
example (for example, patent document 1).
[0003]
Also, in recent years, harmonic imaging that forms an image of the internal state of the subject
by its harmonic frequency components rather than the frequency (fundamental frequency)
component of the ultrasound transmitted from the ultrasound probe into the subject Harmonic
Imaging technology is being researched and developed. This harmonic imaging technology has a
lower side lobe level compared to the level of the fundamental frequency component, an
improved S / N ratio (signal to noise ratio) and an improved contrast resolution, and a beam
width due to an increase in frequency. Narrows to improve the lateral resolution, the sound
pressure is small and the variation of the sound pressure is small at a short distance, so multiple
reflections are suppressed, and the attenuation beyond the focus is the same as the fundamental
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wave and the high frequency It has various advantages such as obtaining a large depth velocity
as compared to the case of using the fundamental wave.
[0004]
The harmonic imaging technology can be roughly divided into two methods: a filter method and
a phase inversion method (pulse inversion method). This filter method is a method in which a
fundamental wave component and a harmonic component are separated by a harmonic detection
filter, only the harmonic component is extracted, and an ultrasonic image is generated from this
harmonic component. In addition, this phase inversion method transmits first and second
transmission signals whose phases are mutually inverted following in the same direction, and
transmits first and second reception signals corresponding to these first and second transmission
signals. It is a method of extracting a harmonic component by adding and generating an
ultrasound image from this harmonic component. Although the fundamental wave components in
the first and second received signals are inverted in phase, for example, the second harmonic
component of the harmonics is in phase, so this is added by adding the first and second received
signals. Second harmonic components are extracted (see, for example, Patent Document 2). JP,
2004-88056, A JP, 2001-286472, A
[0005]
By the way, it is difficult to receive harmonic components in the ultrasonic signal from inside the
object because the signal level is weak compared to the signal level of the fundamental frequency
component. For this reason, the second ultrasonic signal coming from the inside of the subject
based on the first ultrasonic signal transmitted into the inside of the subject is predicted as a
reference signal in advance and correlation processing is performed using this reference signal. A
method of detecting the wave component is conceivable. However, it is difficult to set the
reference signal uniquely because harmonic components are generated in the process of
propagating the first ultrasonic signal in the subject.
[0006]
The present invention is an invention made in view of the above-mentioned circumstances, and
its object is to set a reference signal according to the order of harmonics to be detected, the
diagnostic site of the subject and the diagnostic depth of the subject. An ultrasonic diagnostic
apparatus that performs correlation processing is provided.
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[0007]
As a result of various studies, the present inventor has found that the above object can be
achieved by the present invention described below.
That is, in the ultrasonic diagnostic apparatus according to one aspect of the present invention,
the transmitting unit for transmitting the first ultrasonic signal into the subject, the receiving unit
for receiving the ultrasonic wave, and the receiving unit And an image processing unit configured
to form an image in the subject based on reception of a second ultrasound signal from the
subject based on the first ultrasound signal. The signal processing apparatus further comprises a
correlation unit that detects the second ultrasound signal from the output of the receiving unit by
performing correlation processing between the output of the receiving unit and a preset
reference signal, and the reference signal is the first When the frequency of the sound wave
signal is a fundamental frequency, the frequency is set according to the order of harmonics to be
detected, the diagnostic region of the subject, and the diagnostic depth of the subject.
[0008]
In the ultrasound diagnostic apparatus with such a configuration, the reference signal is set
according to the order of harmonics to be detected, the diagnostic site of the subject, and the
diagnostic depth of the subject, so using this reference signal Correlation processing can be
performed, and harmonic components can be acquired with a higher SN ratio.
[0009]
Further, in the above-described ultrasonic diagnostic apparatus, according to the order of
harmonics to be detected, the diagnosis region of the subject, and the diagnostic depth of the
subject when the frequency of the first ultrasonic signal is a fundamental frequency. And a
correlation signal storage unit for storing a plurality of reference signals that are set, the
correlation unit being an order of harmonics to be detected when the frequency of the first
ultrasonic signal is a fundamental frequency, the object The correlation processing is performed
by selecting one reference signal from the plurality of reference signals in accordance with the
diagnosis site and the diagnosis depth of the subject.
[0010]
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According to this configuration, a plurality of different reference signals are stored in the
reference signal storage unit, and the correlation unit corresponds to the order of harmonics to
be detected, the diagnostic site of the subject, and the diagnostic depth of the subject. Since one
reference signal is selected from the reference signals and correlation processing is performed, a
more appropriate reference signal is selected over the entire diagnostic region, and correlation
processing is performed.
For this reason, it is possible to obtain harmonic components with a higher S / N ratio over the
entire diagnosis region.
[0011]
Further, in the above-described ultrasonic diagnostic apparatus, the reference signal is a function
generated based on the first ultrasonic signal.
[0012]
According to this configuration, an ultrasound diagnostic apparatus using a reference signal that
is a function generated based on the first ultrasound signal is provided.
[0013]
Further, in the above-described ultrasonic diagnostic apparatus, the first ultrasonic signal is a
chirp wave whose frequency is changed with the passage of time.
[0014]
According to this configuration, since the first ultrasonic signal is a chirp wave that is not
normally present in the natural world, it is easy to distinguish it from the noise component when
detecting its harmonic component.
For this reason, it is possible to acquire harmonic components with a higher SN ratio.
Here, the frequency of the high frequency part of the chirp wave is preferably set so as not to
overlap with the frequency of the harmonic component.
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[0015]
Further, in the above-described ultrasonic diagnostic apparatus, when the frequency of the first
ultrasonic signal is a basic frequency, the reference signal is an order of harmonics to be detected
in 2 n (n is a positive integer). If the first ultrasonic signal has a positive value, then it is 2n
power of the first ultrasonic signal multiplied by +1, and if the first ultrasonic signal has a
negative value, -1 And the second power of the first ultrasonic signal multiplied by.
[0016]
According to this configuration, it is possible to generate a reference signal for acquiring the 2nth harmonic component.
[0017]
In the above-described ultrasonic diagnostic apparatus, the reference signal is set to (2n + 1) (n is
a positive integer) the order of harmonics to be detected when the frequency of the first
ultrasonic signal is a basic frequency. In this case, it is characterized in that it is the (2n + 1) th
power of the first ultrasonic signal.
[0018]
According to this configuration, it is possible to generate a reference signal for acquiring the (2n
+ 1) -th harmonic component.
[0019]
Further, in the above-described ultrasonic diagnostic apparatus, the reference signal is
characterized in that its amplitude is increased or decreased according to the focal point depth.
[0020]
According to this configuration, an ultrasonic diagnostic apparatus using a reference signal
whose amplitude is increased or decreased according to the focal point depth is provided.
[0021]
Further, in the above ultrasonic diagnostic apparatus, the correlation unit is characterized by
being provided with an analog product-sum operation apparatus based on the CCD principle.
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[0022]
According to this configuration, since the correlation unit is configured to include the analog
product-sum operation device based on the CCD principle, it is possible to perform correlation
processing more appropriately even for harmonic components that are weak signal levels.
[0023]
In addition, the above-described ultrasonic diagnostic apparatus further includes a piezoelectric
element that includes a piezoelectric material and can convert signals between an electric signal
and an ultrasonic signal by utilizing a piezoelectric phenomenon. The piezoelectric element is
characterized by being separated into one for transmission and one for reception.
[0024]
According to this configuration, since the piezoelectric element is separated into the transmitting
and receiving parts, the transmitting part of the piezoelectric element can be a piezoelectric
element suitable for transmission, and the piezoelectric Among the elements, the portion for
reception can be a piezoelectric element suitable for reception.
For this reason, it is possible to further obtain harmonic components.
[0025]
Further, in the above-described ultrasonic diagnostic apparatus, a plurality of the piezoelectric
elements are arranged in a two-dimensional array.
[0026]
According to this configuration, it is possible to provide an ultrasonic diagnostic apparatus
including an ultrasonic probe in which a plurality of piezoelectric elements are arranged in a twodimensional array.
[0027]
Further, in the above-described ultrasonic diagnostic apparatus, the piezoelectric element for
reception includes an organic piezoelectric material.
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[0028]
According to this configuration, since the organic piezoelectric element capable of receiving
ultrasonic waves in a relatively wide band is used for the receiving piezoelectric element, it is
possible to more appropriately receive the high frequency component.
[0029]
The ultrasonic diagnostic apparatus according to the present invention can perform correlation
processing by setting the reference signal in accordance with the order of harmonics to be
detected, the diagnostic site of the subject, and the diagnostic depth of the subject, and thus
higher SN It is possible to obtain harmonic components by ratio.
[0030]
Hereinafter, an embodiment according to the present invention will be described based on the
drawings.
In addition, the structure which attached | subjected the same code | symbol in each figure
shows that it is the same structure, and abbreviate | omits the description.
Further, in the present specification, suffixes are denoted by reference symbols in which suffixes
are omitted as appropriate when collectively referred to, and suffixes are denoted in the case of
indicating individual configurations.
[0031]
FIG. 1 is a view showing an appearance configuration of an ultrasonic diagnostic apparatus in the
embodiment.
FIG. 2 is a block diagram showing an electrical configuration of the ultrasonic diagnostic
apparatus in the embodiment.
FIG. 3 is a view showing the configuration of an ultrasonic probe in the ultrasonic diagnostic
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apparatus of the embodiment.
FIG. 3A is a perspective view showing the entire configuration of the ultrasonic probe, and FIG.
3B is a diagram showing one of the plurality of first piezoelectric elements constituting the
ultrasonic probe. It is a sectional view showing.
[0032]
As shown in FIGS. 1 and 2, the ultrasonic diagnostic apparatus S transmits an ultrasonic wave
(first ultrasonic signal) to a subject such as a not illustrated living body, and the ultrasonic wave
reflected by the subject Connected to the ultrasonic probe 2 via the cable 3 and the ultrasonic
probe 2 for receiving the reflected wave (echo, second ultrasonic signal) of the The transmission
signal of the electric signal is transmitted to cause the ultrasonic probe 2 to transmit the first
ultrasonic signal to the subject, and the second received from the ultrasonic probe 2 from the
inside of the subject And an ultrasonic diagnostic apparatus main body 1 for imaging the internal
state in the subject as an ultrasonic image based on the reception signal of the electric signal
generated by the ultrasonic probe 2 according to the ultrasonic signal Ru.
[0033]
For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 controls the
operation input unit 11, the transmission unit 12, the reception unit 13, the correlation unit 14,
the image processing unit 15, the display unit 16, and The configuration includes a unit 17 and a
reference signal storage unit 18.
[0034]
The operation input unit 11 receives, for example, an instruction to start a diagnosis, an input of
data such as personal information of a subject, and an instruction to finely adjust each weighting
coefficient g (n) of a reference signal described later. , An operation panel having a plurality of
input switches, a keyboard, and the like.
[0035]
The transmission unit 12 is a circuit that supplies a transmission signal of an electrical signal to
the ultrasound probe 2 via the cable 3 according to the control of the control unit 17 to generate
a first ultrasound signal in the ultrasound probe 2. is there.
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For the first ultrasonic signal, for example, a chirp wave in which the frequency is changed at a
predetermined rate set in advance as time passes is used.
The predetermined ratio of the chirp wave may be a chirp wave whose frequency gradually
increases with time, and may be a chirp whose frequency gradually decreases with time.
For example, each of the transmission beam former circuit 122 that forms a transmission beam
according to the transmission signal s (t) from the control unit 17 and each of the ultrasonic
wave probes 2 described later from the transmission beam former circuit 122 A drive signal
generation circuit 121 or the like that generates a drive signal for driving the first piezoelectric
element 22 is provided (see FIG. 4).
The receiving unit 13 is a circuit that receives a received signal of an electrical signal from the
ultrasound probe 2 via the cable 3 according to the control of the control unit 17, and outputs
the received signal to the correlation unit 14.
The receiving unit 13 includes, for example, an amplifier for amplifying the received signal at a
predetermined amplification factor.
[0036]
The correlation unit 14 detects the second ultrasonic signal from the output of the receiving unit
13 by performing correlation processing between the output of the receiving unit 13 and a
reference signal set in advance.
This reference signal is set according to the order of harmonics to be detected when the
frequency of the first ultrasonic signal is the fundamental frequency, the diagnostic site of the
subject (type of diagnostic site), and the diagnostic depth of the subject It is done.
[0037]
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The reference signal storage unit 18 includes, for example, a storage element such as a ROM or
an EEPROM, and when the frequency of the first ultrasonic signal is a basic frequency, the order
of harmonics to be detected, the diagnostic site of the subject, And storing a plurality of reference
signals set in accordance with the diagnostic depth of the subject.
Then, the correlation unit 14 is a reference signal storage unit according to the order of
harmonics to be detected when the frequency of the first ultrasonic signal is a fundamental
frequency, the diagnostic site of the subject, and the diagnostic depth of the subject Correlation
processing is performed by selecting one reference signal from a plurality of reference signals
stored in 18.
The order of harmonics to be detected, the diagnostic site of the subject, and the diagnostic depth
of the subject are input from the operation input unit 11, for example.
[0038]
Here, the reference signal may be a function generated based on the first ultrasound signal as
described later.
More specifically, for example, when the frequency of the first ultrasonic signal is a fundamental
frequency, the reference signal is, for example, 1st over when the order of harmonics to be
detected is 2n (n is a positive integer). The first ultrasonic signal multiplied by +1 if the sound
wave signal is a positive value, the first ultrasonic wave multiplied by -1 if the first ultrasonic
signal is a negative value It is the 2n power of the signal.
Further, for example, when the frequency of the first ultrasonic signal is a fundamental frequency
and the order of harmonics to be detected is (2 n + 1) (n is a positive integer), the reference
signal It is the (2n + 1) power.
The amplitude of the reference signal may be increased or decreased according to the focal point
depth.
[0039]
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The timing generation unit 19 generates operation timings of the respective units of the
ultrasonic diagnostic apparatus main body 1, and outputs the operation timings to the respective
units requiring operation timings.
[0040]
The image processing unit 15 is a circuit that generates an image (ultrasound image) of the
internal state in the subject based on the reception signal subjected to the correlation processing
by the correlation unit 14 under the control of the control unit 17.
For example, the image processing unit 15 outputs y-1, y-2, y-3,... From each of the correlation
processing units 50-1, 50-2, 50-3,. The delay correction circuit 151 that corrects the delay time
with respect to y−n, and the phasing addition circuit 152 that performs phasing addition on the
output of the delay correction circuit 151 and the like are configured (see FIG. 4).
The display unit 16 is a device that displays the ultrasonic image of the subject generated by the
image processing unit 15 according to the control of the control unit 17.
The display unit 16 is, for example, a display device such as a CRT display, an LCD, an organic EL
display, a plasma display, or a printing device such as a printer. The control unit 17 includes, for
example, a microprocessor, a memory element, and peripheral circuits thereof, and the operation
input unit 11, the transmission unit 12, the reception unit 13, the correlation unit 14, the
reference signal storage unit 18, and the image processing unit It is a circuit that performs
overall control of the ultrasound diagnostic apparatus S by controlling the display unit 15 and
the display unit 16 according to the functions.
[0041]
The ultrasound probe (ultrasound probe) 2 is a device that transmits a first ultrasound signal into
a subject and receives a second ultrasound signal from within the subject based on the first
ultrasound signal. For example, as shown in FIG. 3 (A), a plurality of the piezoelectric materials
are provided, and by using the piezoelectric phenomenon, signals can be mutually converted
between an electrical signal and an ultrasonic signal. It comprises one piezoelectric element 22.
That is, in the case where the plurality of first piezoelectric elements 22 transmit the first
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ultrasonic signal into the subject, the electric signal of the transmission input from the
transmission unit 12 of the ultrasonic diagnostic apparatus 1 via the cable 3 is In the case where
the first ultrasonic signal is converted into a first ultrasonic signal by utilizing the piezoelectric
phenomenon and the first ultrasonic signal is transmitted into the subject and the second
ultrasonic signal from the inside of the subject is received, By utilizing the phenomenon, the
received second ultrasonic signal is converted into an electric signal, and the received signal is
output to the receiving unit 13 of the ultrasonic diagnostic apparatus main body 1 through the
cable 3. When the ultrasound probe 2 is applied to the subject, the first ultrasound signal
generated by the first piezoelectric element 22 is transmitted into the subject, and the second
ultrasound signal from inside the subject is the first It is received by the piezoelectric element 22.
[0042]
More specifically, for example, as shown in FIG. 3B, each of the plurality of first piezoelectric
elements 22 includes a signal electrode layer 222 made of a conductive material connected to
the signal line 24 of the conductive line, and a signal A piezoelectric layer 221 formed on the
electrode layer 222 and made of a piezoelectric material, and a ground electrode layer 223
formed on the piezoelectric layer 221 and made of a conductive material are configured. That is,
each of the plurality of first piezoelectric elements 22 includes a pair of first and second
electrodes facing each other, and a piezoelectric portion made of a piezoelectric material is
formed between the first and second electrodes. For example, an inorganic piezoelectric material
is used as the piezoelectric material. Inorganic piezoelectric materials include, for example, socalled PZT, quartz, quartz, lithium niobate (LiNbO3), potassium niobate tantalate (K (Ta, Nb) O3),
barium titanate (BaTiO3), lithium tantalate (LiTaO3) and titanate. Strontium (SrTiO3) or the like.
[0043]
The plurality of first piezoelectric elements 22 may be arranged in one direction, and may be
configured in a one-dimensional array, or, as shown in FIG. For example, they may be arranged in
m rows x n columns in two directions orthogonal to each other, and may be configured in a twodimensional array (m and n are positive integers). FIG. 3A shows an example in which twentyfour first piezoelectric elements 22-11 to 22-46 constitute a two-dimensional array in which two
directions orthogonal to each other are arranged. In an actual ultrasonic probe, for example, the
first piezoelectric element 22 is 4096 of 64 × 64, for example, the first piezoelectric element 22
is 16900 of 128 × 128, or a large number of first piezoelectric elements are used. It goes
without saying that the element 22 is provided.
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[0044]
In the present specification, suffixes are denoted by reference numerals with suffixes omitted
when referring to generic names, and suffixes are denoted by suffixes when individual
configurations are indicated. Also, the subscript on the left side of the subscript indicates a line
number, and the subscript on the right side indicates a column number. For example, the first
piezoelectric elements 22-23 are the first piezoelectric elements 22 of row number 2 and column
number 3.
[0045]
The plurality of first piezoelectric elements 22 are disposed on one main surface of the flat
acoustic damping member 21, and the acoustic matching layer 23 is stacked on the plurality of
first piezoelectric elements 22. The plurality of first piezoelectric elements 22 are disposed on
the acoustic damping member 21 with a predetermined gap (groove, gap, gap) therebetween in
order to reduce mutual interference such as crosstalk. In order to further reduce mutual
interference, it is preferable that an ultrasonic absorbing material that absorbs ultrasonic waves
be filled in this gap. For example, a thermosetting resin such as a polyimide resin or an epoxy
resin is used as the ultrasonic absorbing material.
[0046]
The acoustic braking member 21 is made of a material that absorbs ultrasonic waves, and
absorbs ultrasonic waves emitted from the plurality of first piezoelectric elements 22 in the
direction of the acoustic braking member 21. The acoustic damping member 21 is also generally
referred to as a damper or backing layer. A plurality of signal lines 24 (signal lines 24-11 to 2446 in FIG. 3A) connected to the respective first piezoelectric elements 22 penetrate the acoustic
braking member 21. The plurality of ground lines (ground lines) connected to the respective first
piezoelectric elements 22 are drawn from the top surface of the respective first piezoelectric
elements 22, although the illustration is omitted.
[0047]
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The acoustic matching layer 23 is a member for matching the acoustic impedance of the first
piezoelectric element 22 with the acoustic impedance of the subject. Therefore, the acoustic
matching layer 23 is set such that the difference between the acoustic impedance of the first
piezoelectric element 22 and the acoustic impedance of the subject is minimized. The acoustic
matching layer 23 may be composed of a single layer or multiple layers. In FIG. 3A, the acoustic
matching layer 23 is not shown. In addition, the acoustic matching layer 23 may be formed into a
circularly bulging shape, and may also have the function of an acoustic lens that converges the
ultrasonic wave transmitted toward the object, and such an acoustic lens It may be laminated on
the acoustic matching layer 23.
[0048]
Then, in the ultrasound probe 2, each of the plurality of first piezoelectric elements 22 is divided
into a plurality of areas, and each of the plurality of areas (sections, areas) has a plurality of
second It has a piezoelectric element.
[0049]
For example, in the example shown in FIG. 3 (B), the first piezoelectric element 22 has first and
second boundaries parallel to one side of the first piezoelectric element 22 in a plan view (in FIG.
(A boundary along the direction) is divided into first to third sections Ar-a to Ar-c.
These three first to third areas Ar-a to Ar-c are rectangular in the same shape in plan view in the
example shown in FIG. 3 (B). In the first area Ar-a, a piezoelectric portion 221-a made of a
piezoelectric material having a first thickness t1 is formed as the piezoelectric portion 221
between the signal electrode layer 222 and the ground electrode layer 223, and the first
resonance frequency A second piezoelectric element 220-a having fc1 is configured. In the
second area Ar-b, a piezoelectric portion 221-b made of a piezoelectric material having a second
thickness t2 is formed as the piezoelectric portion 221 between the signal electrode layer 222
and the ground electrode layer 223, and the second resonance frequency fc2 The second
piezoelectric element 220-b is configured. In the third area Ar-c, a piezoelectric portion 221-c
made of a piezoelectric material having a third thickness t3 is formed as the piezoelectric portion
221 between the signal electrode layer 222 and the ground electrode layer 223, and the third
resonance frequency fc3 The second piezoelectric element 220-c is configured. The first to third
resonance frequencies fc1 to fc3 are different from each other by making the first to third
thicknesses t1 to t3 different from each other. When the performance is the same as the
piezoelectric materials of the second piezoelectric elements 220-a to 220-c, the resonance
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frequency constant is constant. For example, the first thickness t1> the second thickness t2> the
third thickness In the case of t3, the first resonance frequency fc1 <the second resonance
frequency fc2 <the third resonance frequency fc3, and the first to third sections Ar-a to Ar-c have
resonance frequencies from low to high. The second piezoelectric elements 220-a to 220-c are
arranged to be arranged in order of frequency. The resonance frequency constant is given by
(resonance frequency) × (thickness in the vibration direction of the piezoelectric element). For
example, in the case where PZT having a resonance frequency constant of about 2000 Hz · m is
used as the piezoelectric material of the piezoelectric portions 221-a to 221-c, if the first
thickness t1 is designed to be 200 μm, the first area Ar− The resonant frequency of the second
piezoelectric element 220-a in a is 10 Mz, and when the second thickness t2 is designed to be
100 μm, the resonant frequency of the second piezoelectric element 220-b in the second area
Ar-b is 20 Mz Then, when the third thickness t3 is designed to be 50 μm, the resonance
frequency of the second piezoelectric element 220-c in the third area Ar-c is 40 Mz.
[0050]
Here, since the thickness of each of the piezoelectric portions 221-a to 221-c in each of the areas
Ar-a to Ar-c is different as described above, the piezoelectric portion 221-a to 221-c on the
ground electrode layer 223 side When the respective surfaces are made flush and the surface on
the signal electrode layer 222 side of the piezoelectric portion 221-a abuts on the signal
electrode layer 222, the signal electrode layer in the piezoelectric portion 221-b and the
piezoelectric portion 221-c An air gap is formed between each surface on the 222 side and the
signal electrode layer 222. Therefore, the dielectric material 224 is filled in the air gap. Thus, by
filling the space with the dielectric material 224, the voltage applied between the signal electrode
layer 222 and the ground electrode layer 223 acts on the piezoelectric portions 221-b and 221c, and the piezoelectric portion 221- Since the dielectric material 224 does not substantially act
on the resonance frequency of the piezoelectric portions 221-b and 221-c while the b and 221-c
mechanically vibrate due to the piezoelectric phenomenon, the piezoelectric portions 221-b and
221-c have It is possible to resonate at a resonance frequency corresponding to t1 and t2. The
dielectric constant of the dielectric material 224 filled in the air gap by such action is preferably
about 2 to about 40.
[0051]
In the ultrasonic diagnostic apparatus S having such a configuration, for example, when an
instruction to start diagnosis is input from the operation input unit 11, the transmission unit 12
generates a transmission signal of an electric signal under the control of the control unit 17. The
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transmission signal of the generated electrical signal is supplied to the ultrasound probe 2 via the
cable 3. More specifically, the transmission signal of this electric signal is supplied to the first
piezoelectric element 22 in the ultrasonic probe 2, and in the first piezoelectric element 22, a
plurality of second piezoelectric elements in the first piezoelectric element 22. And 220
respectively. In the first piezoelectric element 22, of the plurality of second piezoelectric
elements 220, the second piezoelectric element 220 having a resonant frequency corresponding
to the electric signal is supplied with a transmission signal of the electric signal, and the
thickness of the second piezoelectric element 220 is It expands and contracts in the longitudinal
direction, and ultrasonically vibrates according to the transmission signal of this electric signal.
The ultrasonic vibration causes the first piezoelectric element 22 to emit a first ultrasonic signal.
The first ultrasonic signal emitted from the first piezoelectric element 22 in the direction of the
acoustic damping member 21 is absorbed by the acoustic damping member 21. Further, the first
ultrasonic signal emitted from the first piezoelectric element 22 in the direction of the acoustic
matching layer 23 is emitted through the acoustic matching layer 23. For example, when the
ultrasound probe 2 is in contact with the subject, a first ultrasound signal is transmitted from the
ultrasound probe 2 to the subject.
[0052]
The ultrasonic probe 2 may be used in contact with the surface of the subject, or may be inserted
into the subject and inserted into a body cavity of a living body, for example. .
[0053]
The ultrasonic waves transmitted to the subject are reflected at one or a plurality of interfaces
different in acoustic impedance in the inside of the subject, and become reflected waves of
ultrasonic waves (second ultrasonic signal).
The second ultrasonic signal includes not only the frequency (fundamental frequency of the
fundamental wave) component of the transmitted first ultrasonic signal, but also the frequency
component of the harmonic of an integral multiple of the fundamental frequency. For example,
the second harmonic component (= 2 × 1 harmonic component), the third harmonic component
(= (2 × 1 + 1) harmonic component), and the fourth harmonic, such as 2 times, 3 times and 4
times the fundamental frequency Harmonic components (= 2 × 2nd harmonic components) and
the like are also included. The second ultrasonic signal is received by the ultrasonic probe 2.
More specifically, this second ultrasonic signal is received by the first piezoelectric element 22
through the acoustic matching layer 23. That is, the second ultrasonic signal is received by the
plurality of second piezoelectric elements 220 in the first piezoelectric element 22, and
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mechanical vibration is converted into an electric signal in each of the plurality of second
piezoelectric elements 220. It is taken out as a received signal.
[0054]
Here, the second piezoelectric element 220 mechanically vibrates at a frequency component
substantially corresponding to the resonance frequency of the frequency components included in
the second ultrasonic signal, and outputs an electrical signal according to the vibration. Then,
since the first piezoelectric element 22 includes the plurality of second piezoelectric elements
220 having different resonance frequencies, the second ultrasonic wave is generated over a
plurality of frequency components included in the second ultrasonic signal, that is, a wide
frequency band. It can receive a signal.
[0055]
Then, the reception signal of the electric signal extracted by the first piezoelectric element 22
(the plurality of second piezoelectric elements 220) is received by the receiving unit 13
controlled by the control unit 17 via the cable 3. The receiving unit 13 performs reception
processing of the received signal that is input, and more specifically, for example, amplifies and
outputs the signal to the correlation unit 14. Then, by performing correlation processing in the
correlation unit 14, harmonic components of a predetermined order are obtained and output to
the image processing unit 15.
[0056]
Here, in the above, ultrasonic waves are sequentially transmitted from the first piezoelectric
elements 22 toward the subject, and the second ultrasonic signals reflected by the subject are
received by the plurality of first piezoelectric elements 22.
[0057]
Then, based on the received signal received by the receiving unit 13 and subjected to correlation
processing by the correlation unit 14 under the control of the control unit 17, the image
processing unit 15 determines whether the object is exceeded from the time from transmission
to reception, reception intensity, etc. A sound wave image is generated, and the display unit 16
displays the ultrasonic image of the subject generated by the image processing unit 15 under the
control of the control unit 17.
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[0058]
Next, the correlation processing will be described more specifically.
[0059]
FIG. 4 is a view showing a more specific configuration of the ultrasonic diagnostic apparatus
according to the embodiment in the explanation of the correlation processing.
FIG. 5 is a diagram for explaining the correlation operation.
FIG. 6 is a diagram for explaining an analog product-sum operation.
[0060]
If correlation processing is performed after converting an analog signal into a digital signal, the
amount of energy occupied by the harmonic components in the entire received signal is weak, so
the dynamic range necessary for forming a high quality ultrasound image can not be obtained.
Therefore, in the correlation unit 14 in the present embodiment, the correlation processing itself
is performed in an analog manner.
[0061]
In FIG. 4, the correlation unit 14 includes a plurality of correlation processing units 50-1, 50-2,
50-3,... For each of the plurality (n) of first piezoelectric elements 22 of the ultrasound probe 2.
The correlation processing units 50-1, 50-2, 50-3, ..., 50-n are configured in the same manner.
The correlation processing unit 50 is a circuit that calculates the correlation between the output
of the receiving unit 13 and the reference signal by performing an analog product-sum operation
based on the CCD principle. The charge transfer unit 52, the weight setting unit 53, the digital /
analog multiplication unit 54, and the addition unit 55 are provided.
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[0062]
The sample hold unit 51 is a circuit that holds the output of the reception unit 13 at a sampling
cycle corresponding to the operation timing from the timing generation unit 19. The sample hold
unit 51 outputs the charge corresponding to the held output of the reception unit 13 to the
charge transfer unit 52 at a timing according to the operation timing.
[0063]
The charge transfer unit 52 is configured to include a plurality of charge holding units 521-1,
521-2, 521-3,..., 521-n holding charges. These charge holding portions 521-1, 521-2, 521-3,...,
521-n are connected in series, and hold their charge at timing according to the operation timing
from the timing generation portion 19. The charge held in the portion 521 is sequentially
transferred to the charge holding portion 521 in the subsequent stage. This point is based on the
CCD principle.
[0064]
The digital / analog multiplication unit 54 includes a plurality of digital / analog multipliers (DA
multipliers) 541-1, 541-2, 541-3, ..., 541-n provided corresponding to the respective charge
holding units 521. It is configured to be equipped. The DA multiplier 541 multiplies the output
value from the charge holding unit 521 by the weighting set by the weighting setting unit 53 in
itself, and outputs the multiplication result to the addition unit 55.
[0065]
The weighting setting unit 53 sets each DA multiplier 541-1, 541-2, 541-3,..., 541-n of the digital
/ analog multiplication unit 54 based on the reference signal stored in the reference signal
storage unit 18. The weighting value is set with respect to. The weighting value is corrected by
the input correction value when the correction value is input from the correction value input unit
111 of the operation input unit 11.
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[0066]
The addition unit 55 adds the multiplication results input from the respective DA multipliers
541-1, 541-2, 541-3,..., 541-n of the digital / analog multiplication unit 54, and performs image
processing on the addition results. It is a circuit that outputs to the unit 15.
[0067]
The correlation unit 14 (correlation processing unit 50) having such a configuration operates as
follows.
[0068]
In analog correlation processing, addition is performed by grouping two or more charges into
one capacitive element using charge transfer technology used for CCD, one charge is divided into
two, one is further divided into two, and so on. Prepare the charges of 1/2, 1/4, 1/8, 1/16, ...
according to the binary expression of the multiplier, discard them, and combine them into one
charge again. An analog charge product sum delay is performed.
This point is an analog product-sum operation.
The correlation processing referred to here is processing to determine how similar two
waveforms are, for example, when there are two number sequences x n and yn, the larger z
shown in the following equation 1, the more 2 The two series will be similar (usually, when the
signal is detected, it shows a sharp peak as in the graph of FIG. 5). z = Σxkyk (1) where Σ is the
sum from k = 1 to k = n.
[0069]
By multiplying the charge amount Qk stored in each stage of the charge holding unit 521 of the
charge transfer unit 52 by the corresponding weighting value of the reference signal (template)
and taking the sum, it is determined whether or not there is a signal in the noise. Can be
calculated with a high S / N ratio.
[0070]
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21
The correlation processing unit 50 is a device capable of delaying, adding and multiplying using
the charge amount Q which is an analog amount, and by using this, calculation processing such
as correlation processing for high resolution, high speed and low power consumption Is possible.
As an actual device configuration, as described above, a CCD-like device form is obtained. For
example, in the case of charge transfer in a CCD, this is done by adjusting the depth of the
potential well to be deeper in the transfer direction. As shown in FIG. 6A, the signal flow is
controlled by moving the charge from left to right in the figure. When the addition is performed,
as shown in FIG. 6B, the drive voltage is controlled so that two or more potential wells become
one. When multiplication is performed, for example, a drive voltage that divides one potential
well into two is controlled (for example, the reverse of the above adder), and the charge Q is Q /
2, Q / 4, Q / 8, Q / Divide into 16, Q / 32, Q / 64, and so on, and discard or leave it according to
the bit of the multiplier (digital value). That is, if the bit is 0, it is discarded, and if the bit is 1, it is
left. Thereafter, the multiplier M performs multiplication of 0 ≦ M <1 by adding all the
remaining charges. For example, Q × 0.36827 (decimal number) becomes Q × 0.01011110
(binary number), and becomes Q × (0 + 0/2 + 1⁄4 + 0/8 + 1/16 + 1/32 + 1/64 + 1/128 +
0/256).
[0071]
In addition to these absolute value charges, a product-sum operation is realized using a sign bit
representing the positive or negative of the charge amount which is an absolute value.
[0072]
The correlation process is a process of determining how similar two waveforms are, for example,
as described above, when there are two number sequences x n and yn, z represented by the
above equation 1 is It becomes a judgment standard.
[0073]
Assuming that the transmission signal is s (t), that in which the transmission signal s (t) contains
noise is z (t), and the judgment criterion consisting of the above equation 1 is z, as shown by the
broken line in FIG. , A sharp peak is detected at the moment when the reference signal and the
reception signal overlap.
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The larger this peak is, the more similar the signal to the reference signal has been received.
In order to improve the noise resistance, it is desirable to use a signal which is as natural as
possible and not natural as a transmission signal (reference signal) s (t). In practice, as shown in
FIG. 4, the continuous signal s (t) received by the receiving unit 13 is sampled and held at time
τ, and discrete amounts f (t), f (t−τ), f (t−2τ) , F (t-3τ), f (t-4τ),. These can be obtained by
multiplying them by weighting coefficients g (1) to g (n) respectively corresponding to each other
(Equation 2). z = Σf (t−kτ) g (k) (2) where Σ is the sum of k = 1 to k = n.
[0074]
When the value of z is larger than a certain threshold value, the harmonic component of the
second ultrasonic signal is output to the image processing unit 15 as being received at an
intensity proportional to z. The image processing unit 15 obtains a delay time and a signal
strength from this z to generate an ultrasonic image.
[0075]
For example, a transmission signal using a chirp wave of 3 MHz to 5 MHz is as follows. s (t) =
A.sin {2π [(fc−Bw / 2) t + (Bw / (2Tw)) t <2>]} · W (t) (3) W (t) is a window A function (in the
present embodiment, for example, a Hamming window is used), fc is a center frequency of the
chirp wave, Bw is a sweep frequency of the chirp wave, and Tw is a time width of the chirp wave.
In the present embodiment, fc = 4 MHz and Bw = 2 MHz, and Tw is set by the area of the
diagnosis region.
[0076]
Assuming that the order of the harmonics detected by the correlation process is n, the reference
waveform r (t) in the case where n is an even number is expressed by Equation 4. r (t) = f (d, n) (s
(t) / s (t)) {s (t)} <n> (4) On the other hand, reference when n is an odd number The waveform r (t)
is expressed by Equation 5. r (t) = f (d, n) {s (t)} <n> (5) f (d, n) is a term determined by the
diagnostic depth, the diagnostic target and the order, The user may select an optimal value while
looking at the output image by a weighting slider or the like of the correction value input unit
111 prepared for each focal point. A value obtained by digitizing this function r (t) at a specified
14-04-2019
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sampling frequency is written to g (1) to g (n) of the reference signal, and is used as reference
signal data for each diagnostic depth, diagnostic target, and detection order It is stored in the
reference signal storage unit 18.
[0077]
The delay of the beam former is set by the transmission beam former circuit 122 from the
steering angle and focal point depth specified by the control unit 17 based on the ROI, and the
chirp wave formed by the PCM by the drive signal generation circuit 121 is ultrasonic probe. The
voltage is applied to the first piezoelectric element 22 of the element 2 and a first ultrasonic
signal is generated by electroacoustic conversion (piezoelectric phenomenon). The ultrasound
signal focused at the focal point is reflected at the tissue interface in the subject and generates
harmonics depending on the sound pressure intensity. The second ultrasonic signal reflected at
the tissue interface and propagated in the subject is received by the first piezoelectric element 22
of the ultrasonic probe 2 and subjected to reception processing by the receiving unit 13. The
output from the receiving unit 13 is discretized in the time direction by the sample and hold unit
51 for each first piezoelectric element 22 in order to sample and hold the received waveform.
They are input to the charge transfer unit 52 at a timing (control clock) of constant operation
timing. The charge transfer unit 52 has n stages of charge holding units 521-1, 52 1-2, 52 1-3,...,
521-n of xa (1) to xa (n), and each of the charge transfer units The value moves to the next stage.
The respective stages xa (1) to xa (n) of the charge holding units 521-1, 521-2, 521-3,..., 521-n of
the charge transfer unit 52 respectively output the values to be held. DA multipliers 541-1, 5412, 541-3,..., 541-n, each connected to a corresponding DA multiplier 541. In each of the DA
multipliers 541-1, 541-2, 541-3, ..., 541-n, weighting coefficients g (1) to g (n) for correlation
processing are set by the weighting setting unit 53. The weighting coefficients are stored in the
control unit 17 and can be rewritten by the weighting setting unit 53 under control. The control
unit 17 selects the data of the optimum reference signal (template) from the reference signal
storage unit 18 according to the order of harmonics to be detected, the diagnostic site and the
focal point depth (diagnosis depth), etc. The weighting coefficients g (1) to g (n) held by the DA
multipliers 541-1, 541-2, 541-3,. Each DA multiplier 541-1, 541-2, 541-3,..., 541-n has a delay
proportional to the number of bits of the weighting coefficient g (k) and xa (k) × g (k) Are output
by the addition unit 55 to obtain the correlation coefficient za.
The subscript a represents that it is associated with the a-th first piezoelectric element 22 among
the plurality of first piezoelectric elements 22 of the ultrasound probe 2. The correlation
coefficient za is obtained for each of the first piezoelectric elements 22 arranged in an array of
the ultrasound probe 2, and the delay correction circuit 151 performs delay correction based on
the peak position of the correlation coefficient za. After that, the correlation coefficient of each
14-04-2019
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first piezoelectric element 22 is phasing-added by phasing addition circuit 152 to obtain the
entire correlation coefficient z, that is, the reception signal y (t) subjected to correlation
processing, An ultrasound image is formed on the basis of
[0078]
As described above, in the ultrasonic diagnostic apparatus S of the present embodiment, the
reference signal is set according to the order of harmonics to be detected, the diagnostic site of
the subject, and the diagnostic depth of the subject, so this reference signal is used. By using it,
correlation processing can be performed, and it becomes possible to acquire harmonic
components with a higher SN ratio.
[0079]
Further, in the above-described ultrasound diagnostic apparatus S, a plurality of different
reference signals are stored in the reference signal storage unit 18, and the correlation unit 14
diagnoses the order of harmonics to be detected, the diagnostic site of the subject and the
subject. Since one reference signal is selected from the plurality of reference signals in
accordance with the depth and correlation processing is performed, a more appropriate
reference signal is selected over the entire diagnostic region, and correlation processing is
performed.
For this reason, it is possible to obtain harmonic components with a higher S / N ratio over the
entire diagnosis region.
[0080]
Further, in the above-described ultrasound diagnostic apparatus S, the reference signal is a
function generated based on the first ultrasound signal. More specifically, the reference signal is
the first ultrasonic signal when the order of harmonics to be detected is 2n (n is a positive
integer) when the frequency of the first ultrasonic signal is the fundamental frequency. Is a 2n
power of the first ultrasonic signal multiplied by +1 if it is a positive value, and the first
ultrasonic signal multiplied by -1 if the first ultrasonic signal is a negative value Of 2n. Therefore,
it is possible to generate a reference signal for acquiring the 2n-th harmonic component.
Alternatively, when the order of the harmonics to be detected in the case where the frequency of
the first ultrasonic signal is the basic frequency is (2 n + 1) (n is a positive integer), the reference
14-04-2019
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signal It is 2n + 1). Therefore, it is possible to generate a reference signal for acquiring the (2n +
1) -th harmonic component.
[0081]
Further, in the above-described ultrasonic diagnostic apparatus S, since the first ultrasonic signal
is a chirp wave that is not normally present in the natural world, it is easy to distinguish it from
the noise component when detecting its harmonic component. For this reason, it is possible to
acquire harmonic components with a higher SN ratio.
[0082]
Further, in the above-described ultrasonic diagnostic apparatus S, the correlation unit 14 is
configured to include an analog product-sum operation apparatus based on the CCD principle.
For this reason, it is possible to perform correlation processing more appropriately even for
harmonic components that are weak signal levels.
[0083]
Next, a method of manufacturing an ultrasound probe will be described.
[0084]
(Method of Manufacturing Ultrasonic Probe) FIG. 7 is a view showing a configuration of a jig
used for manufacturing the ultrasonic probe in the embodiment.
FIG. 7A shows a top view of the jig, and FIG. 7B shows a cross-sectional view of the jig. FIG. 8 is a
view showing the manufacturing process of the ultrasonic probe in the embodiment.
[0085]
The ultrasonic probe 2 of the above configuration in the present embodiment can be
manufactured, for example, by using a jig T having a configuration shown in FIG. 7.
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[0086]
As shown in FIG. 7, the jig T includes a plurality of circles having different diameters and
including particles 32 harder than the piezoelectric material of the second piezoelectric element
220 (piezoelectric material of the first piezoelectric element 22) at least on the peripheral surface
portion. It is a thing of the shape which made the center axis correspond and overlapped the
board 31. As shown in FIG.
The circumferential surface portion is in the vicinity of the circumferential surface and / or the
circumferential surface. The thickness of the jig T, that is, the thickness in the stacking direction
in which the plurality of disks 31 in the jig T are stacked is the pitch between the first
piezoelectric elements 22 (the size of the first piezoelectric elements (length of one side) It is a
value corresponding to). The thickness of the jig T is a value corresponding to the width of the
second piezoelectric element 220. Moreover, the level | step difference of each disc 31 in the jig |
tool T is a value corresponding to the difference of the thickness t of each 2nd piezoelectric
element. Such a jig T disperses hard fine particles 32 such as, for example, diamond and
zirconium in a resin, and molds the resin in which the fine particles 32 are dispersed using a
mold having a shape corresponding to the jig T. It can be formed. The particles 32 have, for
example, an average particle size of about 10 nm to about 10 μm. In FIG. 4, three disks 31-a to
31-c for forming the piezoelectric portions 221-a to 221-c of the three second piezoelectric
elements 220-a to 220-c shown in FIG. A jig T in the form of overlapping is shown. The thickness
of the jig T is a value corresponding to the pitch between the first piezoelectric elements 22, and
the thickness of each of the disks 31-a to 31-c is the width of each of the piezoelectric portions
221-a to 221-c. The step between the disc 31-a and the disc 31-b adjacent thereto is the first
thickness t 1 of the piezoelectric portion 221-a and the second thickness of the piezoelectric
portion 221-b adjacent thereto. The level difference between the disc 31-b and the disc 31-c
adjacent to the disc 31-b is equal to the difference between t 2 and t 2, and the difference
between the disc 31-b and the disc 31-c It is made equal to the difference with the third
thickness t3.
[0087]
And the ultrasonic probe 2 of the said structure in this embodiment can be manufactured at each
following process, for example by using the jig | tool T of the structure shown in FIG.
[0088]
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27
In FIG. 8, first, a piezoelectric material body D having a predetermined size is prepared (FIG. 8A),
and a plurality of first piezoelectric elements 22 are assumed for this piezoelectric material body
D, and each assumed first piezoelectric is The piezoelectric material body D is cut by using the jig
T shown in FIG. 4 so as to form each piezoelectric portion 221 in each area Ar in the element 22
(FIG. 8 (B)).
In cutting the piezoelectric material body D, the jig T is rotated while the circumferential surface
of the jig T is in contact with the piezoelectric material body D, and the jig T is moved along the
element row direction of the first piezoelectric element 22. It is done by. Next, the dielectric
material 224 is applied to the cutting surface, and the dielectric material 224 is polished so as to
be a flat surface (FIG. 8C). Next, the signal electrode layer 222 and the ground electrode layer
223 are formed on both surfaces of the dielectric material body D subjected to the cutting
process and the polishing process, for example, by a thin film forming technique such as
evaporation or sputtering (FIG. 8D) . Next, the acoustic damping member 21 is formed on the
signal electrode layer 222 (FIG. 8E). Next, a plurality of first piezoelectric elements 22 are formed
by grooving using, for example, a dicing saw (FIG. 8F). Then, the acoustic matching layer 23 is
formed on the ground electrode layer 223, and the ultrasonic probe 2 configured as shown in
FIG. 3 is manufactured by these steps.
[0089]
Further, in the ultrasonic probe 2 described above, between the adjacent second piezoelectric
elements 220 in the plurality of second piezoelectric elements 220, there are grooves (gaps,
gaps, gaps) in the thickness direction along their boundaries. It may be formed. By forming the
grooves between the second piezoelectric elements 220 adjacent to each other as described
above, mutual interference such as crosstalk between the plurality of second piezoelectric
elements 220 is reduced.
[0090]
Further, in the above-described ultrasonic diagnostic apparatus S, the ultrasonic probe 2
preferably comprises a piezoelectric material, and by using a piezoelectric phenomenon, signals
between the electric signal and the ultrasonic signal are mutually signaled. The piezoelectric
element can be divided into one for transmission and one for reception. The piezoelectric
element for transmission and the piezoelectric element for reception may be stacked in the
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transmission / reception direction of the ultrasonic signal, or juxtaposed in a plane substantially
perpendicular to the transmission / reception direction of the ultrasonic signal, and twodimensional array The plurality of piezoelectric elements arranged in the matrix may be divided
into areas.
[0091]
In such a configuration, since the piezoelectric element is separated into the transmission and
reception parts, the transmission part of the piezoelectric element can be a piezoelectric element
suitable for transmission, and the piezoelectric element Among them, the receiving portion can
be a piezoelectric element suitable for receiving. For this reason, it is possible to further obtain
harmonic components.
[0092]
Further, in the above-described ultrasonic diagnostic apparatus S, the piezoelectric element for
receiving the ultrasonic probe 2 may preferably include an organic piezoelectric material. In such
a configuration, since the organic piezoelectric element capable of receiving ultrasonic waves in a
relatively wide band is used for the receiving piezoelectric element, it is possible to more
appropriately receive the high frequency component.
[0093]
As the organic piezoelectric material, for example, a polymer of vinylidene fluoride can be used.
Also, for example, as the organic piezoelectric material, a vinylidene fluoride (VDF) based
copolymer can be used. This vinylidene fluoride-based copolymer is a copolymer (copolymer) of
vinylidene fluoride and other monomers, and as the other monomers, trifluoroethylene,
tetrafluoroethylene, perfluoroalkyl vinyl ether PFA), perfluoroalkoxyethylene (PAE),
perfluorohexaethylene and the like can be used. Since the electromechanical coupling constant
(piezoelectric effect) in the thickness direction changes depending on the copolymerization ratio
of the vinylidene fluoride-based copolymer, an appropriate copolymerization ratio is adopted
according to, for example, the specification of the ultrasonic probe. . For example, in the case of a
copolymer of vinylidene fluoride / ethylene fluoride, the copolymerization ratio of vinylidene
fluoride is preferably 60 mol% to 99 mol%, and in the case of a composite element in which an
organic piezoelectric element is laminated on an inorganic piezoelectric element The
14-04-2019
29
copolymerization ratio of vinylidene is more preferably 85 mol% to 99 mol%. Further, in the case
of such a composite element, the other monomers are preferably perfluoroalkylvinylether (PFA),
perfluoroalkoxyethylene (PAE) and perfluorohexaethylene. For example, polyurea can be used as
the organic piezoelectric material. In the case of this polyurea, it is preferable to form a
piezoelectric by vapor deposition polymerization. As monomers for polyurea, one may cite the
general formula H2N-R-NH2 structure. Here, R may contain an alkylene group which may be
substituted with any substituent, a phenylene group, a divalent heterocyclic group, or a
heterocyclic group. The polyurea may be a copolymer of a urea derivative and another monomer.
As preferred polyureas, mention may be made of aromatic polyureas using 4,4'diaminodiphenylmethane (MDA) and 4,4'-diphenylmethane diisocyanate (MDI).
[0094]
While the present invention has been properly and sufficiently described above through the
embodiments with reference to the drawings in order to express the present invention, those
skilled in the art can easily change and / or improve the above embodiments. It should be
recognized that it is possible. Therefore, unless a change or improvement implemented by a
person skilled in the art is at a level that deviates from the scope of the claims set forth in the
claims, the change or the improvement is the scope of the rights of the claim It is interpreted as
being included in
[0095]
It is a figure showing the appearance composition of the ultrasonic diagnostic equipment in an
embodiment. It is a block diagram which shows the electric constitution of the ultrasound
diagnosing device in embodiment. It is a sectional view showing the composition of the
ultrasound probe in the ultrasound diagnostic device of an embodiment. It is a figure which
shows the more concrete structure of the ultrasound diagnosing device concerning embodiment
in description of a correlation process. It is a figure for demonstrating correlation operation. It is
a figure for demonstrating an analog product sum operation. It is a figure which shows the
structure of the jig | tool used for manufacture of the ultrasound probe in embodiment. It is a
figure which shows the manufacturing process of the ultrasound probe in embodiment.
Explanation of sign
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[0096]
S ultrasonic diagnostic apparatus T jig 1 ultrasonic diagnostic apparatus main body 2 ultrasonic
probe 14 correlation unit 18 reference signal storage unit 22 first piezoelectric element 50
correlation processing unit 51 sample hold unit 52 charge transfer unit 53 weighting setting unit
54 Digital / analog multiplier 55 Adder 220 Second piezoelectric element
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