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TECHNICAL FIELD OF THE INVENTION The present invention relates to a coupler for a
polymeric ultrasonic transducer of an ultrasonic diagnostic fI device. Here, with ultrasonic
diagnostic @ setting, ultrasonic waves are emitted by a transducer consisting of a piezoelectric
vibration element toward the inside of a subject (mainly a human body but the target in
nondestructive testing etc.). It refers to one that detects and processes reflections, transmissions
or scattered waves from a subject and provides information in the body obtained from this for
diagnosis. In particular, ultrasonic pulses that emit ultrasonic pulses to detect a reflected wave
from a subject and image in-vivo information are currently widely used. [Prior Art] A polymeric
ultrasonic transducer used for ultrasonic diagnosis and the like is excellent in acoustic matching
with water or a human body, and is characterized in that it can generate short pulse ultrasonic
waves. And because of the ease of processing, it is usual to make the transducer front face
concave in order to focus the sound wave. If the front surface of the transducer is concave, air
bubbles may be mixed in the concave portion or the transducer may be lifted between the ribs. In
ultrasonic diagnosis, a method is often used in which an ultrasonic transducer is in contact with
the human body and ultrasonic pulses are emitted into the body. At this time, a coupling agent or
polymer gel is used in order to prevent the formation of an air gap between the transducer and
the subject in order to improve the sound coupling between the human body and the transducer.
It is used. Thus, coupling agents or polymer gels are particularly important substances for
concave transducers. Coupling agents are prepared by dissolving polyvinyl pyrohydrin in
propylene glycol to form a paste (JP-A-46-146) or a water-containing polymer gel (JP-A-5563636) in a tubular container. In this case, an arbitrary amount is directly applied to the
diagnosis site by hand or brush at the time of use and wiped off after the examination is
completed, but □ can not be completely wiped off, and the patient's clothes may not be stained
or not Give pleasure. In addition, various couplers are made of a polymer gel having an acoustic
velocity and acoustic impedance similar to that of a living organism, such as silicone rubber and
gelatin gel (Japanese Patent Application Laid-Open No. 5.3-107190), but continuous There are a
lot of dissatisfaction points in dealing with various living tissues. In addition, when the patient is
subjected to ultrasonic puncture or direct recovery surgery and a transducer is inserted into the
membrane, or the head portion is incised to transmit ultrasound directly from under the skull to
the brain. In the case of applying the user directly to the incision, strict sterilization is required.
However, in conventional couplers for transformers, the only structurally possible disinfection
methods are gas sterilization or immersion in formalin solution, and the current status is that
each sterilization time must be 24 hours and long hours. It is. [Object of the Invention] The object
of the present invention is to attach a coupler formed of a water-containing gel consisting of a
cross-linked three-dimensional polymer of a hydrophobic polymer and a hydrophilic polymer to
the tip of a prefabricated polymer ultrasonic transducer. By doing this, the acoustic matching
between the subject and the transducer can be improved, diagnosis can be facilitated without
giving discomfort to the patient who is the subject, and furthermore, the coupler itself can be
boiled and sterilized alone. The purpose is to provide a heat-resistant coupler that can be used
during operation in a surgical procedure as a disposable product. [Configuration of the Invention]
That is, according to the present invention, it is formed of a water-containing gel composed of a
cross-linked three-dimensional polymer of a hydrophobic polymer and a hydrophilic polymer at a
saturated water content of 50% or more and less than 80%. The present invention relates to a
coupler for a polymeric ultrasonic transducer, which is characterized. The crosslinked threedimensional polymer refers to a copolymer or a crosslinked material described below at 1 °.
Preferably used as a hydrophilic monomer for obtaining a polymer which is a material of a
coupler are N-vinyl lactams such as N-vinyl pyrrolidone, N-vinyl piperidone, N-vinyl caprolactam
and the like, 2-hydroxyethyl acrylate , 2-hydroxyethyl methacrylate, diethylene glycol
monoacrylate, diethylene glycol monomethacrylate, hydroxypropyl acrylate, human 0 xpropyl
methacrylate, tetraethylene glycol monomethacrylate, pentaethylene glycol monomethacrylate,
dipropylene glycol monoacrylate, hexaethylene glycol monoacrylate, Hexaethylene glycol
methacrylate, octaethylene glycol acrylate, octaethylene glycol Methacrylate, 4-hydroxybutyl
methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, thaxy acrylate, thaxyethyl
methacrylate, methoxypropyl acrylate, methoxypropyl methacrylate, methaoxyethaoxyethyl
acrylate, methaoxyethaoxyethyl Methacrylates, butoxyethyl acrylate, butoxyethyl methacrylate,
dodecoxyethyl acrylate, dodecoxyethyl methacrylate, propoxyethyl acrylate, propoxyethyl
methacrylate, acrylamide, and polyvinyl alcohol.
Bulk polymerization or solution polymerization is performed using one or more of these
monomers, and hydrophilic polymers are promoted. Since the hydrophilic polymer alone does
not generally satisfy the tensile strength and boiling resistance physical properties required as a
coupler, it is possible to improve the physical properties by adding a hydrophobic component.
The hydrophobic component used here is a monomer of acrylic acid ester or methacrylic acid
ester, and one or more of them are copolymerized with the hydrophilic component. Also, instead
of the weight of the hydrophobic component, a hydrophobic copolymer having a
postcrosslinkable functional group can be used. The postcrosslinkable polymer refers to a
polymer having a functional group sufficient to form a crosslink between hydrophobic
copolymers. When a hydrophobic copolymer is used, acrylic acid ester and 7 chloronitrile, acrylic
acid ester and methacrylic acid ester, methacrylic acid ester and styrene, methacrylic acid ester
are used as monomers for obtaining it. There are acrylonitrile and the like, and the preparation
ratio of the copolymer can be selected from the combination and the composition suitable for the
physical properties required as a coupler. As a monomer for introducing a functional group into
the hydrophobic copolymer, butoxy acrylamide, glycidyl methacrylate, vinylene carbonate 7-to,
hydroxyethyl methacrylate, vinyl methacrylate, allyl methacrylate or the like is used. The
copolymerization composition ratio of the monomer for obtaining the hydrophobic copolymer to
the monomer for introducing the functional group is preferably 1000: 1 to 10: 1. When a
hydrophobic copolymer contains a hydroxyl group as a functional group, it can be esterified with,
for example, methacrylic acid, and a polymer capable of post-crosslinking by introducing a
polymerizable carbon-carbon double tackiness It can be done. Also, the method for producing the
postcrosslinking hydrophobic copolymer is carried out as follows. As a monomer, two or more
kinds of monomers are selected from a system such as acrylonitrile, acrylic acid ester,
methacrylic acid ester, styrene, etc., and the above-mentioned monomer for introducing a postcrosslinking functional group is added, bulk polymerization or dissolution Manufactured by
liquid polymerization. The polymerization catalyst used is a catalyst for producing a coupler
described later, and in the case of heat, a range from room temperature to 120 ° C. is used. The
polymerization must be stopped before gelation. The gelled polymer can not be homogeneously
dissolved as a polymerization stock solution for producing a coupler. Next, a method of
manufacturing the coupler will be described. The coupler for a transducer according to the
present invention is characterized in that the sound velocity and the acoustic impedance can be
adjusted relatively freely, but if the water content is 80% or more, the sound velocity is too large.
When the water content is less than 50%, the speed of sound is small and the acoustic
attenuation is also rapidly increased, making it unusable for practical use.
From these conditions, the saturated water content of the coupler is preferably 50% or more and
less than 80%, and in consideration of matching with the speed of sound in the human body, 65%
or more and less than 80% is a more preferable value. Therefore, the mixing yield of the
hydrophilic component and the hydrophobic copolymer is preferably in the range of 90:10 to
40:60 by weight. The solvent is preferably a solvent which gives a transparent gel under the
condition that the solvent does not inhibit the polymerization reaction or the post-crosslinking
reaction. The type of solvent can be selected from a wide range depending on the combination of
the hydrophilic component and the hydrophobic copolymer. In the case of the combination of Nvinylpyrrolidone and poly (methyl acrylate and ethyl methacrylate), which is a particularly
preferred embodiment of the present invention, a solvent system in which dimethyl sulfoxide
(DMSO> or a small amount of dioxane is added thereto) is used. Used. The amount of solvent
used should be 5 to 95% of the total amount of the stock solution for polymerization. In
particular, the range of 50 to 80% by weight is preferable. When a polymer is used as a
hydrophilic component or a hydrophobic component, a crosslinking agent is optionally used
which reacts with a functional group during polymerization to form a crosslink between polymer
molecules. . For example, for polymers having a hydroxyl group as a functional group, a
polyvalent aldehyde, a polyvalent carboxylic acid, a polyvalent isocyanate or the like is used as a
crosslinking agent. When a polymerizable monomer is used as the hydrophilic component, a
crosslinking agent is added to proceed the crosslinking polymerization. The crosslinker can be
selected from compounds having at least two unsaturated double bonds in the same molecule.
Preferred examples include di- or triaryl compounds such as diallyl succinate, diallyl phthalate,
diallyl malate, diethylene glycol bisallyl carbonate, triallyl cyanurate, triallyl inocyanurate, triallyl
phosphate, triallyl trimellitate, Divinylbenzene, NN-methylenebisallylamide, ethylene glycol
diacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, hexamethylene
bismaleimide, divinyl urea, bisphenol A bis methacrylate, divinyl adipic acid, glycerin
trimethacrylate, trimethylol Propane triacrylate, trimethylolpropane trimethacrylate, trivinyl
trimellitate, 1 Di- or Toribiniru compounds such as 5-Pentajen, allyl acrylate, allyl vinyl
compounds such as allyl methacrylate, can be mentioned vinyl (meth) acrylate.
The addition amount of the crosslinking agent is in the range of 0.002 to 20% by weight with
respect to the total amount of polymerizable monomers of the hydrophilic component or the
hydrophobic component. The crosslinking polymerization is carried out by heat, light, electron
beam or the like in the presence of an initiator, if necessary. Preferred examples of the initiator
include (tertiary butyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tertiary butyl
hydroperoxide, lauroyl peroxide, and (organic) peroxide such as ammonium bisulfate. And azo
compounds such as azobisisobutyronitrile, azobiscyclohexanecarbonitrile,
phenylazoisobutyronitrile, azobisdimethylvaleronitrile, and a redox catalyst. The addition amount
of the initiator is in the range of about 0, ooi to 3% by weight with respect to the polymerizable
monomer. Additives such as a crosslinking co-catalyst and a coloring agent can be added to the
stock solution of the present invention as required. It is also possible to add polymers which can
be extracted from solvent-containing gels (e.g. poly N-vinyl pyrrolidone). Not only such
extractable poly (7-mer) but also extractable substances can be regarded as part of the solvent.
The polymerization stock solution for producing a coupler having the composition as described
above is preferably injected into a mold for forming a coupler mold of the concavo-convex
portion 211, and heat, light, electron beam or the like is made to act to advance polymerization
or a cross reaction I1. In the case of heat, the reaction is usually performed at a temperature of
120 ° C. from the chamber. The solvent-containing gel formed in the template can be easily
peeled off from the template by immersion in liquid, and the solvent in the gel can be replaced by
water. Next, the solvent-containing gel obtained from the stock solution for polymer production
of a coupler according to the present invention is converted to a water-containing gel, dried, and
then shaped into a coupler by cutting and polishing method, and then hydrated to obtain a
coupler for ultrasonic transducer. It can also be done. Furthermore, polymerization can be
carried out even in a rotary mold, and a solvent-containing gel can be formed. The watercontaining gel thus obtained can be replaced with water or any other liquid (eg, disinfectant,
preservative, etc.). FIG. 1 shows the coupler 2 according to the present invention mounted on a
single type transformer 1 and FIG. 2 shows the coupler 2 in the case where the opposite surface
of the transducer side is made convex and an acoustic lens effect is added. Although the coupler
according to the present invention is not shown in the drawings, it is of course applicable not
only for single type transducers but also for linear type and sector type transducers.
Next, methods of measuring the strength and the saturated water content will be described.
Performance test as a coupler: A glass plate of thickness 3III is cut into 7 cm × 7 B, washed and
dried, then 0.2 cm + thick and 5llll 11 size 5 CIIIX with a film of 1 inch film (manufactured by
Fujifilm) Make a 501 spacer and set it. The following polymerization stock solution is injected
under an argon atmosphere, and the interplate polymerization is temperature-programmed for
16 hours under heating at 40 to 90 ° C. After polymerization, the glass plate is immersed in a
DMSO aqueous solution at 90 ° C. as it is, the glass plate is peeled off, the gel is taken out, and
washed with water. Boiling washing (boiling at 100 ° C. for 30 minutes) was repeated three
times using a large excess of water in order to completely remove unreacted monomers and
DMSO remaining in the gel. For measurement of strength and elongation, after leaving the gel in
a temperature control room at 20 ° C. overnight, the gel is cut into a test piece of 0.211111
thickness and 2 + ua thickness, and it is measured with Toyo Baldwin's forehead tensilon. In the
measurement of the saturated water content, the gel obtained in the same manner as described
above is cut into 10llII × 1011I1 pieces, immersed in a thermostat at 37 ° C. for 1 hour or
more, and weighed 1 (W) with a chemical balance. Next, it is dried at 50 ° C. for 16 hours or
more using a vacuum dryer, and after constant weight, it is weighed again (V /) with a chemical
balance. The saturated water content (ω) is calculated by the following equation. ω = (W−W ′)
/ Wx1. OO (Effects of the Invention) 1) Since it is possible to almost eliminate the need for a
coupling agent (water, olive oil, water-containing gel, etc.) to be applied to a subject, stains on
clothes and discomfort to the patient are significantly reduced. 2) Compared with the general
value 25db / CXl (measured with 2 MHz single contact) of the silicone rubber, the sound
attenuation characteristic value is 5db / cr # (measured with 5Ml-1z single contact) with water
content 70 to 75%. It is an attenuation of 1/10 in energy ratio. 3) In terms of contact with the
living body, a very smooth, low-quality acoustic image is obtained. 4) Since it can be used also for
high frequency transducers, it is possible to manufacture couplers of various shapes having
acoustic velocity and acoustic impedance matched to each part of the living body. 5) When using
the transducer during surgery, it is possible to think separately about the transducer and the
coupler. That is, the coupler can be sterilized in the manufacturing process and supplied to the
operator as a disposable product. 6) By adding a hydrophobic component to a hydrophilic
component as a polymer substance, a polymer having strength and scarring superior to
conventional couplers can be obtained.
Example 1 A single-type ultrasonic transducer coupler shown in FIG. 1 was produced using a
molding mold (made by L, plastic) shown in FIG. The undiluted solution for polymerization
described later was put into the concave (5) under an argon atmosphere, and when the convex
(3) was inserted, the excess liquid was discharged from the liquid passage (4). The mold was
placed in a separable flask, sealed under an argon atmosphere, gradually heated from 40 ° C. to
90 ° C., and polymerization was completed in 16 hours. After polymerization, the whole mold
was immersed in an aqueous solution of DMSO at 90 ° C., the mold was peeled off, and the gel
(2) was taken out. The removed gull was thoroughly washed with water and then sterilized by
boiling. Stock solution methyl methacrylate for polymerization 35ON-vinylpyrrolidone 75Q
triallyl isocyanurate 1.0 g triethylene glycol dimethacrylate 3, 007 Zobisisobutyronitrile 0.1 g
vinyl methacrylate 0.5 g dimethyl sulfoxide 300 g this gel is transparent Excellent and flexible
elastic body. The saturated water content was 70%, and as a result of applying to the coupler for
ultrasonic transducers, the sound velocity was 1630111 / sec, and the acoustic attenuation (for
example, IBi) was 6.1 db / aI. It was very easy to remove it from the human body, and it was well
received by doctors and patients. EXAMPLE 2 An experiment was conducted using a
hydrophobic copolymer (prepolymer) having postcrosslinkable carbon thread-aluminium double
tack as a stock solution for polymerization. The synthesis of the prepolymer was carried out by
charging the following raw material chemicals into 20 three-necked flasks, heating to 50 ° C.
under an argon atmosphere, and polymerizing for 2 II. Methyl acrylate 89.111 methyl
methacrylate 9.9 g vinyl methacrylate 1Q azobisdimethylvaleronitrile o, '+ an-dodecyl mercaptan
0.050 dimethyl sulfoxide 400 g after polymerization is completed, diluted with methanol
5001119 and then polymer with water Settled and recovered. The yield after drying by heating
under vacuum was 29%, and [η] at 25 ° C. was 2.0 when using acetone as a solvent. This was
referred to as prepolymer A, and the following raw material chemicals were mixed and dissolved
to prepare a stock solution for polymerization. プレポリマーA35gN−ビニルピロリドン
7511アゾビスジメチルバレロニトリルO,’l。 Triallyl isocyanurate 0.6 g Dimethyl
sulfoxide 330 g In the same manner as in Example 1, inject into the molding mold of FIG. 3 under
an argon atmosphere and gradually raise the concentration from 40 ° C to 90 ° C for 16 hours.
It polymerized. After polymerization, the whole mold was immersed in an aqueous solution of
DMSO at 90 ° C., the mold was peeled off, and the gel was taken out.
The gel was thoroughly washed with water and then sterilized by boiling. The obtained coupler
was a flexible elastic body and excellent in transparency, and had a saturated water content of
74% and a strength of 9 to 1] / cnF1 elongation of 200%. As a result of wearing in a transducer
(5 MHz single contactor, single type) and subjecting it to inspection, it adheres closely to the
human body surface without any gap, the sound speed is 1600 I / s, the sound attenuation
(round trip) is 3.5 db / a I Images were obtained. After the examination, removal from the human
body was extremely easy and was well received by doctors and patients. In the above
embodiment, although a transducer having a concave surface is described, a coupler using the
material of the present invention is not limited to a concave transducer, and it is needless to say
that a circular or rectangular shape having a flat surface and a convex surface. It is needless to
say that it can be used for general transducers such as the above-mentioned transducers (e.g.,
linear array transducers).
Brief description of the drawings
Fig. 1 is a cross-sectional view of a single-type transducer coupler, Fig. 2 is a cross-sectional view
of a single-type transducer coupler with a lens effect, and Fig. 3 is a mold for the transducer
coupler jaw structure FIG.
1 ... Transducer, 2 ... Crosslinked three-dimensional polymer, 3 ... Convex, 4 ... Flow through, 5 ...
Concave, Patent applicant Toshi Co., Ltd.
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