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JPH0737111

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DESCRIPTION JPH0737111
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic diagnostic apparatus for obtaining an ultrasonic image by transmitting and receiving
ultrasonic waves, and more particularly to an ultrasonic diagnostic apparatus capable of
changing the focus position of an ultrasonic beam.
[0002]
2. Description of the Related Art Conventionally, an ultrasonic diagnostic apparatus transmits an
ultrasonic wave corresponding to an electrical signal applied to an ultrasonic probe to a living
body, and receives an ultrasonic wave returned from the living body. Generate a corresponding
electrical signal. An ultrasonic image inside the living body is obtained by the transmission and
reception of the ultrasonic waves. In order to carry out this function efficiently, in a general
ultrasonic probe, an ultrasonic transducer (piezoelectric ceramic etc.) which is a generation
source of ultrasonic waves is adhered on a backing material, and on it, biological and acoustic An
acoustic matching layer is formed to achieve good matching.
[0003]
In addition, an acoustic lens may be further provided on the acoustic matching layer to make the
emitted ultrasonic waves into a thin beam. That is, by focusing the ultrasonic beam using an
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acoustic lens, focus adjustment is performed in the direction perpendicular to the electron
direction to increase the resolution of the ultrasonic image. In order to facilitate contact with the
living body, the shape of the acoustic lens is convex, and in order to perform focus adjustment, a
material having a sound velocity slower than the sound velocity of 1530 m / sec in the living
organism is required. In general, silicone rubber having a sound velocity of about 1000 m / sec is
used for the acoustic lens.
[0004]
When performing focus adjustment of an ultrasonic probe in which a plurality of strip-shaped
ultrasonic transducers are arranged in an array, a delay circuit is used in the arrangement
direction of the ultrasonic transducers (Y direction) to A so-called electronic focusing method is
often used, in which the ultrasonic transducers are gradually delayed and excited toward the
center from both ends in the arrangement direction of the acoustic transducers. As described
above, when the ultrasonic transducer is excited, the totally synthesized ultrasonic beam can be
focused at an arbitrary depth by selecting the delay time of the delay circuit, and the focus
adjustment can be performed. it can. On the other hand, focus adjustment in the longitudinal
direction of each ultrasonic transducer, that is, in the direction (X direction) orthogonal to the
array arrangement is performed by the fixed focus method determined by the acoustic lens
shape.
[0005]
As described above, in the ultrasonic diagnostic apparatus, focus adjustment suitable for a
desired diagnostic position is performed in advance to obtain an ultrasonic image with high
resolution.
[0006]
However, in the ultrasonic probe of the conventional ultrasonic diagnostic apparatus, the focus
adjustment of the ultrasonic transducer in the X direction is determined by the shape of the
acoustic lens. Because of the focus, there is a problem that the focus can not be changed
according to the diagnosis site during diagnosis.
That is, if the diagnosis site has a complicated shape or if the diagnosis site has a depth, there is a
problem that the focus is shifted during the diagnosis and the resolution is lowered.
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[0007]
The present invention has been made to solve the above problems, and the focus position of the
acoustic lens provided in the ultrasonic probe of the ultrasonic diagnostic apparatus is changed
to facilitate focusing. An object of the present invention is to provide an ultrasonic diagnostic
apparatus capable of adjusting
[0008]
SUMMARY OF THE INVENTION In order to achieve the above object, the present invention
relates to an ultrasonic transducer for forming an ultrasonic beam in accordance with an electric
signal supplied, and to the ultrasonic transducer. An acoustic lens for focusing the formed
ultrasonic beam, a temperature control element for controlling the temperature of the acoustic
lens to change the speed of sound of the acoustic lens, and a temperature control unit for
controlling the temperature of the temperature control element It is characterized by having.
[0009]
According to the above configuration, the ultrasonic diagnostic apparatus of the present
invention changes the temperature of the acoustic lens itself by the temperature control element
controlled by the temperature control unit to control the sound velocity of the acoustic lens.
Therefore, the ultrasonic beam formed by the ultrasonic transducer can be refracted and focused
according to the speed of sound of the controlled acoustic lens to change the focus position of
the ultrasonic beam.
[0010]
DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will
be described below with reference to the drawings.
[0011]
FIG. 1 is an enlarged view of an ultrasonic probe 10 provided at the tip of a probe of an
ultrasonic diagnostic apparatus according to the present invention, wherein (a) is a cross-
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sectional view and (b) is an ultrasonic wave forming surface It is.
The ultrasonic transducers 12 made of piezoelectric ceramic or the like which is a generation
source of ultrasonic waves have a strip shape, and are arranged in an array on the backing
material 14 in the Y direction in the drawing.
Further, an acoustic lens 16 made of silicon rubber or the like is provided to cover the ultrasonic
transducer 12 in order to focus the ultrasonic beam. Then, the ultrasonic transducer 12 forms a
predetermined ultrasonic beam according to a control signal input from a signal line (not shown)
connected to the ultrasonic transducer 12, and a living body to be diagnosed via the acoustic lens
16. It emits an ultrasonic beam. The acoustic lens 16 has a semi-cylindrical shape (approximately
wedge shape), and focusing in the Y direction in the figure is performed by the electronic
focusing method using a delay circuit as described above, and focusing in the X direction in the
figure is usually an acoustic lens. It is refracted at a predetermined angle using the curved
surface shape of 16.
[0012]
A feature of this embodiment is that the temperature control element 18 is embedded inside the
acoustic lens 16 to change the temperature of the acoustic lens 16 itself to change the speed of
sound of the acoustic lens 16 to change the angle of refraction of the ultrasonic beam. It is
controlling the focus position.
[0013]
In general, Snell's law holds when a wave impinges on a medium having a different speed of
sound from a certain medium.
That is, as shown in FIG. 2, the incident wave and the refracted wave are in the normal plane, are
on the opposite side with respect to the boundary line, and the following relationship that the
sine ratio of the angle made by the both normal and constant is constant .
[0014]
Sin θ / sin ζ = C1 / C2 where θ is the refraction angle, ζ is the incident angle, C1 is the speed
of sound of the living body, and C2 is the sound of the acoustic lens.
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[0015]
On the other hand, it is known that the speed of sound of the silicone rubber forming the
acoustic lens 16 becomes slower as the temperature rises as shown in FIG. 3 (a).
Further, it is known that the sound velocity of water equivalent to a living body becomes faster as
the temperature rises as shown in FIG. 3 (b). Therefore, the angle of refraction of the ultrasonic
beam can be changed by changing the temperature of the acoustic lens 16, that is, silicon rubber.
[0016]
Next, the operation of this embodiment will be described with reference to the drawings.
[0017]
As shown in FIG. 1A, the temperature control element 18 embedded in the inside of the acoustic
lens 16 is preferably one that can be easily temperature-controlled by current control or the like,
such as a heater, etc. Controlled by the controller to change the temperature of the acoustic lens
16
[0018]
As described above, since the speed of sound of the silicone rubber forming the acoustic lens 16
is decreased as the temperature rises, the refraction angle θ when the ultrasonic beam is
incident on the living body is increased as shown in the above equation.
Accordingly, as shown in FIG. 4A, the fixed focus position F1 of the ultrasonic beam 20a, which is
conventionally determined by the curvature of the acoustic lens 16 and the temperature of the
acoustic lens 16 at the time of operation of the ultrasonic probe 10, is As shown in FIG. 4B, the
temperature control element 18 forcibly raises the temperature of the acoustic lens 16 to
increase the refraction angle θ of the ultrasonic beam 20b, and the focus position F2 is set to
the ultrasonic probe 10. It can be moved in the approaching direction.
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That is, during the diagnosis by the ultrasonic diagnostic apparatus, it is possible to improve the
diagnostic capability by moving the focus position F2 in accordance with the depth of the portion
of the living body to be diagnosed.
[0019]
In this embodiment, an example is described in which the temperature of the acoustic lens is
forcedly raised by using a heating element such as a heater as the temperature control element,
but an element which is forcedly cooled, for example, utilizing the Peltier effect The cooling
element may be used to cool the acoustic lens to move the focus position F2 farther than the
fixed focus F1. Further, by using both the heating element and the cooling element, the focus
adjustment range can be expanded up and down centering on the fixed focus position.
[0020]
Further, in the present embodiment, as shown in FIG. 1 (b), the temperature control elements 18
are disposed at four positions around the acoustic lens 16, but the silicone rubber forming the
acoustic lens 16 has thermal conductivity. The same effect can be obtained even if one or more
are provided inside or in the vicinity of the acoustic lens 16. Further, temperature control can be
performed more efficiently by surrounding the periphery of the acoustic lens 16 with the loopshaped temperature control element 18.
[0021]
Further, by embedding a temperature detection element consisting of a thermocouple or the like
in a part of the acoustic lens 16 and feeding back the detected temperature information of the
acoustic lens 16 to the temperature control unit, more accurate temperature control of the
acoustic lens 16 is achieved. This enables high precision focus adjustment.
[0022]
Also, in this embodiment, an ultrasonic probe in which a plurality of strip-shaped ultrasonic
transducers are arrayed has been described, but an ultrasonic probe consisting of a single
ultrasonic transducer is described. Can also be adapted.
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[0023]
As described above, according to the ultrasonic diagnostic apparatus of the present invention, the
temperature of the acoustic lens itself is changed by the temperature control element controlled
by the temperature control unit, and the speed of sound of the acoustic lens is increased. Can be
controlled.
[0024]
Therefore, the ultrasonic beam formed by the ultrasonic transducer is focused according to the
speed of sound of the controlled acoustic lens, and the focus position of the ultrasonic beam is
changed to supervise diagnostic positions of different depths. It is possible to focus an acoustic
beam and to perform high-resolution ultrasound diagnosis.
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