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DESCRIPTION JP2011160856

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DESCRIPTION JP2011160856
An ultrasonic probe suitable for high-order harmonic ultrasonic waves is provided. A transmitting
array (10) is formed by a plurality of transmitting transducer elements (12) each transmitting an
ultrasonic wave of a fundamental wave. The plurality of transmission transducer elements 12 are
arranged in accordance with the arrangement condition corresponding to the fundamental wave.
The receiving array 20 is formed by a plurality of receiving transducer elements 22 each
receiving an ultrasonic wave of a higher harmonic. The plurality of receiving transducer elements
22 are arranged according to the arrangement condition corresponding to the harmonics. There
is a difference between the arrangement condition corresponding to the fundamental wave and
the arrangement condition corresponding to the harmonics according to the order of the higher
harmonics. As a result, when transmitting the fundamental wave and receiving the higher
harmonics, it is possible to obtain a very good beam profile. [Selected figure] Figure 1
Ultrasound probe
[0001]
The present invention relates to an ultrasonic probe corresponding to ultrasonic waves of a
fundamental wave and higher harmonics.
[0002]
Microbubbles (or nanobubbles) mean fine bubbles injected into a liquid or the like.
14-04-2019
1
These microbubbles are used in many fields because they have various excellent properties. For
example, as an application to the medical field, since microbubbles become suitable reflectors of
ultrasonic waves, they are used as contrast agents in forming ultrasonic images.
[0003]
In the formation of an ultrasound image using a contrast agent, harmonic components obtained
from bubbles contained in the contrast agent are used. For example, Patent Document 1
describes a ground-breaking technology for transmitting an ultrasonic wave under transmission
conditions based on the behavior of a bubble to form an image based on a harmonic component
obtained from the bubble. Further, Patent Document 2 describes a technique for detecting a
harmonic signal by making the pitch of the transducer element different at the time of
transmission and at the time of reception (e.g., claim 3 of Patent Document 2).
[0004]
JP, 2009-136626, A JP, 11-221215, A
[0005]
In view of the background art described above, the inventor of the present application has
researched and developed ultrasonic imaging technology using bubbles (microbubbles and the
like).
In particular, research and development have been conducted on imaging techniques using
harmonic components.
[0006]
The present invention was made in the process of its research and development, and its object is
to provide an ultrasonic probe suitable for high harmonics ultrasonic waves. Another object of
the present invention is to provide an ultrasonic diagnostic apparatus using the ultrasonic probe.
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[0007]
A preferred ultrasonic probe meeting the above object is a fundamental wave array composed of
a plurality of fundamental wave vibration elements corresponding to the fundamental wave
ultrasonic waves, and a plurality of ultrasonic waves corresponding to the higher harmonics
related to the fundamental waves. And a harmonic array configured of harmonic vibration
elements, wherein the plurality of fundamental wave vibration elements are arranged according
to an arrangement condition corresponding to a fundamental wave, and the plurality of harmonic
vibration elements are arranged to the fundamental wave. It arranges according to the
arrangement condition corresponding to the harmonic which has a difference according to the
order of the high-order harmonic as compared with the corresponding arrangement condition.
[0008]
In the above configuration, there is a difference between the arrangement condition
corresponding to the fundamental wave and the arrangement condition corresponding to the
harmonics according to the order of the higher harmonics.
Thus, for example, an ultrasound probe is provided which is suitable for transmitting the
fundamental wave and for receiving the higher harmonics. Incidentally, Patent Document 2
mentioned above does not describe a technique to make the arrangement condition different
according to the order of the higher harmonics.
[0009]
In a desirable embodiment, each of the fundamental wave vibrating elements is formed in a size
SL along the arrangement direction, and each of the harmonic vibrating elements has a size SH in
which the size SL is reduced according to the order of the higher harmonics. It is characterized in
that it is formed along the arrangement direction.
[0010]
In a desirable embodiment, the order of the high-order harmonics is N, and the size SH is 1 / N of
the size SL.
[0011]
In a desirable embodiment, the plurality of fundamental wave vibration elements are arranged at
a pitch PL along the arrangement direction, and the plurality of harmonic vibration elements
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have a pitch PL reduced according to the order of the higher harmonics. It is characterized in
that it is arranged along the arrangement direction at PH.
[0012]
In a desirable embodiment, the order of the higher harmonics is N, and the pitch PH is 1 / N of
the pitch PL.
[0013]
In a desirable embodiment, the fundamental wave array and the harmonic wave array are
arranged in close proximity to each other, and the harmonic wave array is longer along the
arrangement direction than the fundamental wave array. .
[0014]
Further, according to a preferred ultrasonic diagnostic apparatus satisfying the above object, in
the ultrasonic diagnostic apparatus having the ultrasonic probe, the fundamental wave array is
controlled to transmit an ultrasonic wave of the fundamental wave, and the harmonic wave array
is generated. A transmitter / receiver unit for obtaining a reception signal corresponding to a
high-order harmonic ultrasonic wave; several fundamental vibration elements selected from the
fundamental array; and several harmonic vibration elements selected from the harmonic array It
has a selector connected to the transmitting and receiving unit, and an image forming unit for
forming an ultrasonic image based on the received signal.
[0015]
In a desirable embodiment, the fundamental wave array and the harmonic wave array are
disposed close to each other in substantially parallel to each other to form a composite array
composed of the plurality of fundamental wave vibration elements and the plurality of harmonic
vibration elements. A common serial number is assigned to a plurality of fundamental wave
vibrating elements and a plurality of harmonic vibrating elements in order from one end of the
composite array, and the selectors are sequentially assigned a number of basics A wave vibrating
element and several harmonic vibrating elements are selected and connected to the transmitting
and receiving unit.
[0016]
According to the present invention, an ultrasonic probe suitable for high-order harmonics is
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provided.
Further, according to the present invention, an ultrasonic diagnostic apparatus using the
ultrasonic probe is provided.
[0017]
It is a figure for describing the preferred embodiment of the ultrasonic probe concerning the
present invention.
It is a figure for demonstrating the arrangement condition of several vibration elements.
It is a figure which shows the transmission beam profile at the time of transmitting a
fundamental wave.
It is a figure which shows a transmit / receive beam profile at the time of transmitting a
fundamental wave and receiving a harmonic.
It is a figure which shows the transmission / reception beam profile at the time of transmitting /
receiving a harmonic.
It is a figure which shows the modification of the array structure of several vibration elements.
It is a figure for describing the preferred embodiment of the ultrasound diagnostic device
concerning the present invention.
[0018]
FIG. 1 is a view for explaining a preferred embodiment of an ultrasonic probe according to the
present invention, and FIG. 1 shows an array structure of a plurality of transducer elements
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provided in the ultrasonic probe. In this embodiment, the ultrasound probe comprises a
transmitting array 10 and a receiving array 20. The transmitting array 10 and the receiving
array 20 are arranged in parallel and close proximity to one another.
[0019]
The transmitting array 10 is formed of a plurality of transmitting transducer elements 12 each
transmitting a fundamental ultrasonic wave. The plurality of transmission transducer elements
12 are one-dimensionally arranged along the X-axis direction in accordance with the
arrangement condition corresponding to the fundamental wave. The arrangement conditions will
be described in detail later.
[0020]
On the other hand, the receiving array 20 is formed of a plurality of receiving transducer
elements 22 each receiving an ultrasonic wave of a high-order harmonic. The plurality of
receiving transducer elements 22 are one-dimensionally arranged along the X-axis direction in
accordance with the arrangement condition corresponding to the harmonics. The arrangement
conditions will be described in detail later.
[0021]
Channel numbers are assigned to the plurality of transmission vibration elements 12 and the
plurality of reception vibration elements 22 by a common serial number for transmission and
reception. That is, from one end of the transmitting array 10 and the receiving array 20
(composite array), that is, from the origin side of the X axis shown in FIG. 1, first, from the
channel 1 (CH1) to the three receiving vibrating elements 22 The channel 3 (CH3) is assigned,
and the channel 4 (CH4) is assigned to one transmission vibration element 12 disposed opposite
to them. Furthermore, the channel 5 (CH5) to the channel 7 (CH7) are assigned to the three
receiving transducer elements 22 and the channel 8 (CH8) is assigned to one transmitting
transducer element 12 disposed opposite to them. Is assigned. Thus, channel numbers are
assigned to a plurality of transducer elements included in the composite array consisting of the
transmitting array 10 and the receiving array 20, with a common serial number from one end to
the other end of the composite array.
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[0022]
The ultrasonic probe provided with the arrangement structure shown in FIG. 1 is suitable for
extraction of high-order harmonics obtained from bubbles and the like. For example, a
fundamental wave of ultrasonic waves is transmitted from the transmitting array 10 in a
direction orthogonal to the X-axis and the Y-axis from the transmitting array 10 with respect to a
diagnostic region including the bubbles, and higher harmonics included in the ultrasonic waves
emitted from the bubbles. A wave is received by the receiving array 20.
[0023]
In the present embodiment, the plurality of transmission transducer elements 12 are arranged
according to the arrangement condition corresponding to the fundamental wave, and the
plurality of reception transducer elements 22 are further arranged according to the arrangement
condition corresponding to the harmonics. Therefore, for example, when transmitting a
fundamental wave and receiving a high-order harmonic, a very good beam profile can be
obtained. Therefore, the arrangement conditions and the beam profile in the present embodiment
will be described below.
[0024]
FIG. 2 is a diagram for explaining the arrangement condition of a plurality of transducer
elements. FIG. 2 shows conditions (1) to (4) in which the ratio of the number of elements of the
transmitting vibration element to the number of elements of the receiving vibration element
(transmission: reception) is made different. However, in all of the conditions (1) to (4), the total
number (total number) of the number of transmitting vibrating elements and the number of
receiving vibrating elements is 192 (190 in the case of 1: 4). Keep the length and transmit
aperture constant, and the receive array length and receive aperture constant.
[0025]
The condition (1) is that the ratio of the number of transmitting vibrating elements to the number
of receiving vibrating elements is 1: 1. That is, the number of transmission vibration elements is
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96 and the number of reception vibration elements is 96. Then, the pitch of the transmitting
vibrating element is 0.4 mm, and the pitch of the receiving vibrating element is 0.4 mm. The
pitch is, for example, the distance between the centers of two adjacent vibrating elements. If a
plurality of transducer elements are arranged without gaps, the size (size) of each transducer
element in the arrangement direction is equal to the pitch.
[0026]
The condition (2) is that the ratio of the number of transmitting vibrating elements to the number
of receiving vibrating elements is 1: 2. That is, the number of transmitting vibration elements is
64 and the number of receiving vibration elements is 128. Then, the pitch of the transmitting
vibrating element is 0.6 mm, and the pitch of the receiving vibrating element is 0.3 mm. Further,
in FIG. 2, the condition (3) in which the ratio of the number of transmitting vibrating elements to
the number of receiving vibrating elements is 1: 3, and the ratio of the number of transmitting
vibrating elements to the number of receiving vibrating elements is 1: 4. For certain condition
(4), specific numerical values of the number of vibrating elements and the pitch are described.
[0027]
The results of simulation analysis of the beam profile obtained under each condition shown in
FIG. 2 are shown in FIGS. 3 to 5.
[0028]
FIG. 3 is a diagram showing a transmission beam profile when a fundamental wave is
transmitted.
In FIG. 3, when focusing on a pulse wave with a transmission center frequency of 2 MHz to a
depth of 20 mm by using a transmission array, azimuths obtained under each of the arrangement
conditions of conditions (1) to (4) in FIG. The transmit beam profile of the direction is shown.
Each of the conditions (1) to (4) in FIG. 2 corresponds to the waveforms (1) to (4) in FIG.
[0029]
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The main lobe near 0 ° in the azimuthal direction shown on the horizontal axis is considered to
be related to, for example, the resolution of the image. With respect to the main lobe, for
example, with respect to the height and the width, a large difference does not appear among the
waveforms (1) to (4), that is, the conditions (1) to (4).
[0030]
On the other hand, the height of the side lobes extending from the main lobe to the left and right
in the horizontal axis direction increases in the order of the waveforms (1) to (4). That is, the
condition (1) is the best for the side lobes, and gradually worsens in the order of the conditions
(1) to (4).
[0031]
FIG. 4 is a diagram showing transmit and receive beam profiles in the case where a fundamental
wave is transmitted and a harmonic is received. A transmit / receive beam profile obtained by
estimating the profile of the third harmonic based on the transmit beam profile of the
fundamental wave shown in FIG. 3 and receiving the third harmonic by the receiving array is
shown in FIG. There is. 4 shows transmit and receive beam profiles obtained under each of the
arrangement conditions of conditions (1) to (4) of FIG. 2, and each of conditions (1) to (4) of FIG.
Correspond to the waveforms (1) to (4) of FIG.
[0032]
For the main lobe around 0 ° in the azimuth direction shown on the horizontal axis, conditions
(1) to (4), that is, conditions (1) to (4) do not appear, but conditions for side lobes 3) is the
smallest and good. That is, in the case of transmitting an ultrasonic wave of a fundamental wave
(for example, center frequency 2 MHz) and receiving an ultrasonic wave of a third harmonic (for
example 6 MHz), the ratio of the number of transmitting vibrating elements to the number of
receiving vibrating elements By setting condition (3) in which is 1: 3, it is possible to obtain a
good beam profile with a small side lobe, for example.
[0033]
The ratio of the number of transmitting transducer elements to the number of receiving
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transducer elements in the condition (3), that is, 1: 3, is the ratio of the frequency of the
transmitted ultrasonic wave to the frequency of the received ultrasonic wave, ie, the fundamental
wave It corresponds to 1: 3, which is the ratio of the third harmonic.
[0034]
If this fact is generalized, in the case of transmitting the ultrasonic wave of the fundamental wave
and receiving the ultrasonic wave of the Nth harmonic related to the fundamental wave, the ratio
of the number of transmitting vibration elements to the number of receiving vibration elements
is An arrangement condition of 1: N is considered desirable.
Assuming that the ratio of the number of vibrating elements is 1: N, the ratio of the pitch of the
transmitting vibrating element to the pitch of the receiving vibrating element is 1: 1 / N, that is,
N: 1. Similarly, the ratio of the size of the transmitting vibrating element to the size of the
receiving vibrating element is also 1: 1 / N, that is, N: 1.
[0035]
Thus, according to the order N of the higher harmonics, the ratio of the number of vibrating
elements is set to 1: N, that is, the condition to set the number of receiving vibrating elements to
N times the number of transmitting vibrating elements is optimal. Conceivable. For example, in
the case of transmitting the fundamental wave and receiving the third harmonic, it is desirable to
set the number of receiving transducer elements to three times the number of transmitting
transducer elements.
[0036]
However, when the side lobes of the beam profile shown in FIG. 4 are compared, waveform (2)
and waveform (4) are also relatively better than waveform (1). That is, the condition (2) in which
the number of receiving vibrating elements is twice the number of transmitting vibrating
elements than the condition (1) in which the number of receiving vibrating elements is equal to
the number of transmitting vibrating elements, or the number of receiving vibrating elements
The condition (4) in which the number of transmission transducer elements is four times is a
better beam profile. Therefore, for example, even if it is difficult to make the number of receiving
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vibrating elements three times the number of transmitting vibrating elements due to, for
example, design restrictions or cost constraints, for example, the number of receiving vibrating
elements may be It is thought that a beam profile better than the condition (1) can be realized by
setting it to about twice or more (or three times or more) of the number.
[0037]
Next, for example, in the case of observing a bubble, an ultrasonic image of the bubble is formed
on the basis of the component of the third harmonic obtained from the bubble by transmitting
the ultrasonic wave of the fundamental wave. On the other hand, when observing tissue, for
example, it is desirable to use ultrasonic waves of the same frequency in transmission and
reception. Therefore, when imaging a tissue with an ultrasonic probe provided with the array
structure shown in FIG. 1, harmonic ultrasonic waves are transmitted and received using only the
receiving array 10, for example.
[0038]
FIG. 5 is a diagram showing transmit and receive beam profiles when harmonics are transmitted
and received. Fig. 5 shows the transmit and receive beam profiles when transmitting array pulses
with a transmission center frequency of 6 MHz (harmonics) and receiving 6 MHz ultrasonic
waves using the receiving array as a harmonic (linear) transducer. It is done. The transmission
focus is 20 mm in depth. Each of the conditions (1) to (4) in FIG. 2 corresponds to the waveforms
(1) to (4) in FIG. Compared to the case of the conditions (1) and (2), for example, a good beam
profile with a small side lobe can be obtained in the case of the conditions (3) and (4). Further,
under the condition (3) suitable for bubble imaging, a beam profile as good as the condition (4) is
obtained. That is, it can be seen that the condition (3) is a suitable condition both in bubble
imaging and tissue imaging.
[0039]
FIG. 6 is a view showing a modification of the array structure of the plurality of transducer
elements. FIG. 6A shows a structure in which two rows of transmitting arrays 10 are disposed
outside so as to sandwich the receiving array 20. Similarly to the arrangement structure shown
in FIG. 1, in FIG. 6A, the transmission array 10 is formed of a plurality of transmission vibration
elements each transmitting an ultrasonic wave of a fundamental wave, and a plurality of
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transmission vibrations The elements are arranged according to the arrangement condition
corresponding to the fundamental wave. Further, the receiving array 20 is formed of a plurality
of receiving vibrating elements each receiving an ultrasonic wave of a high-order harmonic, and
the plurality of receiving vibrating elements are arranged in accordance with the arrangement
condition corresponding to the harmonics. For example, the number of receiving transducer
elements constituting the receiving array 20 is set to three times (N in the case of the N-th
harmonic) of the number of transmitting transducer elements constituting the transmission array
10 in one column.
[0040]
Then, in FIG. 6A, the receiving array 20 is longer along the arrangement direction than the
transmitting array 10. For example, the receiving array 20 is 1.2 times the transmitting array 10.
Along with this, the reception aperture is also set to, for example, 1.2 times the transmission
aperture. Note that as a result of lengthening the receiving array 10, in the case of the third
harmonic, the pitch of the transmitting vibrating element is smaller than three times the pitch of
the receiving vibrating element, but it is desirable to be, for example, twice or more .
[0041]
Furthermore, also in FIG. 6A, channel numbers are assigned from one end of the transmit array
10 and the receive array 20 with a common serial number for transmit and receive. However, the
same channel number is assigned to the two transmission vibration elements disposed to face
each other, and the two transmission vibration elements are controlled by the common signal
line. For example, the same transmission signal is supplied to two transmission vibration
elements of channel 1 (CH1) via a common signal line.
[0042]
FIG. 6B shows a structure in which two rows of receiving arrays 20 are arranged on the outside
so as to sandwich the transmitting array 10. Also in FIG. 6B, the transmission array 10 is formed
of a plurality of transmission vibration elements each transmitting an ultrasonic wave of a
fundamental wave, and the plurality of transmission vibration elements correspond to the
arrangement condition corresponding to the fundamental wave. It is arranged. Further, the
receiving array 20 is formed of a plurality of receiving vibrating elements each receiving an
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ultrasonic wave of a high-order harmonic, and the plurality of receiving vibrating elements are
arranged in accordance with the arrangement condition corresponding to the harmonics. For
example, the number of receiving transducer elements forming the receiving array 20 in one row
is three times (N in the case of the N-th harmonic) the number of transmitting transducer
elements forming the transmitting array 10.
[0043]
Further, the receiving array 20 is longer along the arrangement direction than the transmitting
array 10. As a result of lengthening the receiving array 20, in the case of the third harmonic,
although the pitch of the transmitting vibration element is smaller than three times the pitch of
the receiving vibration element, it is desirable to be, for example, twice or more.
[0044]
Further, from one end of the transmitting array 10 and the receiving array 20, channel numbers
are assigned with common serial numbers for transmitting and receiving. However, the same
channel number is assigned to two receiving vibration elements arranged to face each other.
Then, for example, two receiving vibration elements of channel 1 (CH1) are connected to each
other via a common signal line.
[0045]
As shown in FIG. 6, by making the reception aperture wider than the transmission aperture,
transmission with a relatively uniform sound pressure distribution in the depth direction
becomes possible, and relatively good sensitivity in reception And azimuth resolution can be
realized.
[0046]
FIG. 7 is a view for explaining a preferred embodiment of the ultrasonic diagnostic apparatus
according to the present invention, and FIG. 7 is a block diagram showing the entire
configuration of the ultrasonic diagnostic apparatus.
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The ultrasonic diagnostic apparatus shown in FIG. 7 has the ultrasonic probe described using
FIGS. 1 to 6.
[0047]
For example, the plurality of vibration elements in FIG. 7 are a plurality of transmission vibration
elements 12 constituting the transmission array 10 of FIG. 1 and a plurality of reception
vibration elements 22 constituting the reception array 20. As described with reference to FIG. 1,
channel numbers are assigned to the plurality of transmission vibration elements 12 and the
plurality of reception vibration elements 22 by a common serial number for transmission and
reception. The channel (CH) numbers assigned to the respective transducer elements in FIG. 7
are the common serial numbers. For example, the vibration elements of channel 1 (CH1) to
channel 3 (CH3) are for reception, and channel 4 (CH4) is for transmission. Similar to the
example of FIG. 1, the ultrasonic probe is configured of the vibration elements of 192 channels in
total also in FIG.
[0048]
In FIG. 7, 96 channels of transmission / reception circuits 40 are provided for the 192 channels
of vibration elements. That is, the transmission / reception circuit 40 of channel 1 (CH1) to
channel 96 (CH96) is provided. A selector 30 is provided between the 192-channel vibrating
element and the 96-channel transmitting / receiving circuit 40.
[0049]
The selector 30 selects a 96-channel vibrating element from among the 192-channel vibrating
elements, and connects the selected 96-channel vibrating element to the 96-channel transmitting
/ receiving circuit 40. The vibrating element of one channel and the transmission / reception
circuit 40 of one channel are electrically connected to each other through the selector 30.
[0050]
The selector 30 selects 96 vibration elements to which continuous channel numbers are
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assigned, and connects them to each transmission / reception circuit 40. For example, 96
vibration elements from channel 1 (CH1) to channel 96 (CH96) are first selected and connected
to the transmission / reception circuit 40 of 96 channels. When transmission and reception of
ultrasonic waves end in this connected state, 96 vibration elements from channel 2 (CH1) to
channel 97 (CH96) are then selected and connected to the transmission and reception circuit 40
of 96 channels to transmit and receive ultrasonic waves. Is executed. Thus, the 96 transducer
elements are connected to the 96-channel transmission / reception circuit 40 while shifting the
channel numbers of the transducer elements one after another, and, for example, linear scanning
electronic scanning is realized.
[0051]
The beam former 50 forms a reception beam based on the reception signals obtained from the
plurality of transmission and reception circuits 40. That is, the reception signal is obtained from
the transmission / reception circuit 40 connected to the reception vibration element among the
96 channels transmission / reception circuit 40, and the reception signals obtained from the
plurality of reception vibration elements are received by performing phase adjustment addition
processing Form a signal along the beam. Then, in the image forming unit 60, an ultrasonic
image is formed from the signal along the received beam.
[0052]
In the ultrasonic diagnostic apparatus shown in FIG. 7, the image forming process described in
Patent Document 1 (Japanese Patent Laid-Open No. 2009-136626) may be used. For example, a
set of ultrasonic waves having phases inverted with each other is transmitted, and a first received
signal corresponding to one of the sets and a second received signal corresponding to the other
are obtained, and The difference between the two received signals may be calculated to extract
the harmonic component. Of course, other methods may be used to extract harmonic
components.
[0053]
While the preferred embodiments of the present invention have been described above, the abovedescribed embodiments are merely illustrative in every respect, and do not limit the scope of the
present invention. The present invention includes various modifications without departing from
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the essence thereof.
[0054]
DESCRIPTION OF SYMBOLS 10 Array for transmissions, 12 elements for transmission, 12 arrays
for reception, 22 elements for reception, 30 selectors, 40 transmission / reception circuits, 50
beam formers, 60 image formation part.
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