JPS62249640

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DESCRIPTION JPS62249640
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic lens mainly used for an ultrasonic probe of an ultrasonic diagnostic apparatus and the
ultrasonic probe. (Conventional art) In general, in an ultrasonic diagnostic apparatus, an acoustic
lens is conventionally used in order to improve the resolution of the obtained image. This
acoustic lens uses, as a lens material, a material whose sound velocity (hereinafter also referred
to as the velocity of sound) at an acoustic velocity of 1 that is slower than the sound velocity of
an organism to converge the ultrasonic beam on the organism. The shape is convex as shown in
FIG. 4 (a), and it is concave as shown in FIG. 4 (b) when a material of sound velocity v2 faster
than the sound velocity VO of the living body is used. However, as an acoustic lens for an
ultrasonic probe to be used by being brought into direct contact with the surface of a living body,
if the surface is a concave shape, the adhesion to the living body is deteriorated and a good
tomographic image can not be obtained. Therefore, as an acoustic lens for an ultrasonic probe to
be brought into direct contact with a living body surface, one having a convex surface shape is
widely used. The acoustic lens material whose surface shape is convex is required to have sound
velocity sufficiently slower than the sound velocity of the living body. Furthermore, the acoustic
impedance is as close as possible to that of the living body in addition to the sound velocity, and
attenuation of ultrasonic waves is small. And other properties are required. At present, as such a
convex lens material, silicone rubber having a sound velocity of about 1000 m / s, which is
sufficiently lower than the sound velocity (about 1530 m / s) of a living body, and acoustic
impedance similar to that of the living body is widely used. (A problem to be solved by the
invention) However, silicone rubber has a considerably large attenuation, for example, 1 for
ultrasonic waves of frequency 5 and 2! Ｉｕ！ It is an attenuation of 3 to 4 d8 per unit, which is
one of the causes of deterioration in S / N of the ultrasonic diagnostic apparatus. In addition,
silicone rubber has high moisture permeability, and moisture penetrates into the inside of the
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ultrasonic probe through the silicone rubber to cause deterioration of internal materials such as
vibrators, which is one of the causes of sensitivity deterioration of the ultrasonic probe. ing.
SUMMARY OF THE INVENTION The object of the present invention is to solve the problems of
the prior art as described above, to provide an acoustic lens having characteristics of low sound
wave attenuation and low moisture transmission, and further to use this acoustic lens as an
ultrasonic diagnostic system. An object of the present invention is to provide an ultrasonic probe
which is improved in S / N, is easy to use, and is excellent in long-term reliability by applying to
an ultrasonic probe. [Composition of the invention] (Means for solving the problems) The
composite acoustic lens according to the first invention is a convex first focusing surface made of
a material whose propagation speed of sound wave is slower than that in living body An acoustic
lens and a concave second focusing acoustic lens made of a material having a speed of
propagation of sound waves faster than the speed of propagation in a living body are constructed
by combining and integrating the convex surface and the concave surface.
In the ultrasonic probe according to the second aspect of the present invention, the composite
acoustic lens according to the first aspect of the present invention is disposed on the
transmission / reception wavefront side of the ultrasonic transducer. (Operation) Since the
present invention is configured as described above, it operates as follows. That is, the first
convergent acoustic lens made of a material whose sound velocity is slower than the sound
velocity of the living body has a convex shape, and the second convergent acoustic lens made of
a material whose sound velocity is faster than the sound velocity of the living body has its shape
Has a concave shape. Therefore, by combining and combining the uneven surfaces of the two
lenses, it is possible to form a single substantially flat composite acoustic lens (hereinafter also
referred to as a composite lens). In this case, since the first and second lenses both have a
converging action, the thickness of one compound lens is reduced, whereby the attenuation of
ultrasonic waves is reduced. Further, as a material forming the second focusing lens has a sound
velocity faster than the sound velocity of the living body, for example, there is a waterproof
material such as plastic, so a compound lens in which the second focusing lens is combined is
And the permeation of water can be reduced. In addition, an ultrasonic probe using such a
complex lens has good S / N because the ultrasonic wave attenuation of the complex lens is
small, and the adhesion to the body surface is good because the shape of the lens surface is
almost flat. And the second focusing acoustic lens of the compound lens is waterproof so that
moisture does not intrude into the inside of the ultrasonic probe and cause deterioration of the
internal material such as the transducer, and hence long-term reliability It will be excellent in sex.
(Embodiment) An embodiment shown in the drawings will be described below. An embodiment of
a composite acoustic lens according to the first invention is shown in FIG. In this embodiment,
the present invention is applied to a cylindrical lens, and its structure is a structure in which a
convex lens and a concave lens are combined and integrated as shown in FIG. 1 (b). 10 is a first
convex lens for focusing formed by a material (for example, silicone rubber) whose sound
velocity is slower than the sound velocity of a living body, and 11 is a first formed by a plastic
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material (for example, TPX) whose sound velocity is faster than the sound velocity of a living
body 2 is a concave lens for convergence. Each lens acts as a focusing lens even if used alone.
The features obtained by combining the two lenses are described below in comparison to using
each alone. Now with silicone rubber (sonic velocity Vl = 1000 m / S), focal length F = 6071 in
vivo (sonic velocity Vo z 1530 'rr L / S)! When a single lens of aperture D = 15 m for converging
the ultrasonic beam to I11 is constructed, this lens curvature R1 is R1 = 20.4 s because R1 = (1V1 / Vo) F = 0.34F, and the lens thickness is The gap dl is d1 = 1.43 m from dx = Rt-1-D / 2) 2.
On the other hand, when a plastic lens is used to construct a single focusing lens for the same
purpose, the curvature R2 is R2 = (1-vo / V2) F = when using a plastic (for example, TPX) having
an acoustic velocity V2 of 200 OTrt / S. R2 = 15 m from 0.25F. Accordingly, the depth d2 of the
recess valve is in the order of d2 ← 35.4 from d2 = R2-2- / 2 ′ ′, and the thickness of the lens
is d = 0.8 m. Therefore, in this case, the attenuation of the ultrasonic wave at the central portion
is 4.8 to 6.4 dB at 58 H 2, and the attenuation is 3.8 to 5.1 dB less than that of the silicone
rubber single lens. FIG. 2 shows an embodiment of an ultrasonic probe using this composite lens.
A compound lens 1 is mounted on the tip of the probe body 2 as described above. As shown in
FIG. 3, in the compound lens 1, a flange 12 is formed on a second converging concave lens 11
made of a plastic material, and the flange 2 is engaged with the tip of the probe body 2. Thus, by
disposing the plastic second focusing concave lens 11 on the outer side, it is possible to prevent
the intrusion of water from the outside of the probe into the inside more securely. The ultrasonic
transducer 3 is disposed at the back of the composite acoustic lens 1. The ultrasonic transducer
3 is provided with an electrode 5 and an earth electrode 6 for driving by applying a voltage
thereto. A backing material 4 is disposed on the back of the ultrasonic transducer 3 so as to
absorb ultrasonic waves directed in the back direction of the transducer 3. The complex lens and
the ultrasonic probe as described above have the following effects. That is, (1) The uneven
surfaces of the second and second lenses 10.11 are combined and united to form a single flat
shape; Since both second lenses 10.11 have a converging action, the thickness d of one
compound lens is small, which reduces the attenuation of ultrasonic waves. (2) Further, since the
second focusing lens 11 is formed of waterproof plastic, it is possible to reduce the permeation of
water. Therefore, the ultrasonic probe using such a complex lens 1 has good S / N because the
ultrasonic wave attenuation of the complex lens is small, and the adhesion to the body surface is
good because the shape of the lens surface is flat. It is easy to use, and the second focusing
acoustic lens 11 of the compound lens is free from the fact that waterproof moisture penetrates
into the inside of the ultrasonic probe 7 to cause deterioration of the internal material of the
vibrator 3 etc. It will be highly reliable.
Furthermore, since the second focusing lens 11 is disposed on the outer side, it is possible to
more reliably prevent the entry of water from the outside to the inside of the probe. Although the
embodiments of the present invention have been described above, it is needless to say that the
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present invention is not limited to the above-described embodiments, and appropriate
modifications can be made within the scope of the present invention. For example, the shape of
the complex lens is not limited to a flat shape, but may be a somewhat convex shape. [Effects of
the Invention] As described in detail above, the complex lens of the present invention has a small
thickness so that the attenuation of ultrasonic waves is small, and the size of the lens is 5 mm. (G)
V V2 <VO (b) Fig. 4
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