JPH0194827A - Mechanical scanning type ultrasonic probe - Google Patents

Abstract

PURPOSE:To make acoustic impedance near to that of the skin of a human body and to improve time resolving power, by using organosiloxane containing a predetermined organosiloxane unit in a window part. CONSTITUTION:The window part of a mechanical scanning type ultrasonic probe is formed of a cured substance of organosiloxane containing an organosiloxane unit represented by general formula [I] wherein R<1> and R<2> are a group selected from a substituted or non-substituted monovalent hydrocarbon group and at least 80mol.% of R<1> is a methyl group and at least 50mol.% of R<2> is a phenyl group and X is an integer of 5-400 and the phenyl group among the total org. groups is 10-50mol.%.

Description

[Detailed Description of the Invention] The present invention relates to a probe for ultrasonic diagnostic equipment, and in particular a probe having an acoustic impedance close to that of human skin and a low attenuation rate. The present invention relates to a mechanical scan type ultrasonic probe that uses a small material for the window and has good time resolution, which has not been previously achieved.

Problems that will soon be solved with conventional techniques In mechanical scan type ultrasound probes, the window portion is made of polyurethane, etc., but the acoustic impedance is different from that of the human skin. Therefore, there was a problem in that multiple reflections occurred between the probe and the skin, increasing the pulse width and worsening the temporal resolution. Another drawback is that the attenuation is large and the signal becomes small.

The material constituting the window of a mechanical scanning ultrasonic probe must have the following properties:

The ultrasonic waves transmitted from the probe pass through the window, are reflected inside the human body, and the probe receives the sound waves that return through the window.The sound pressure at that time is measured by the reflectance inside the human body, etc. Must be sufficient to indicate minute differences in acoustic characteristics. In other words, the acoustic impedance of the window should be close to the acoustic impedance of the human skin, the attenuation rate should be as small as possible, and the complex shape including the spherical surface unique to mechanical scanning ultrasound probes should be It needs to be able to be manufactured easily and not deform or break when pressed against the human body.

In order for ultrasonic waves to pass through the window, the acoustic impedance of the window should ideally be 1.58±0.04 x 10' kg/rriS, which is equal to the acoustic impedance of the human body! , 25~1.80 x 10' kg/rt
Any range of f/s is sufficient.

Further, the attenuation rate needs to be 0.80 dB/m/MHz or less.

Regarding the sound speed, it is a problem if it deviates from the sound speed of human skin, but if it is in the range of 1300 to 1700 m/s, the lens effect due to the spherical surface is small.

Furthermore, in order to minimize the attenuation within the tube wall, the thickness of the window portion is made thin, so it is necessary to have high mechanical strength.

Mechanical scan type probes can be made with materials that satisfy these conditions, but general plastics with acoustic impedance within the above range have low strength or high attenuation. There were drawbacks.

In the case of silicone resin and polydimethylsiloxane rubber, although the attenuation rate is small, the acoustic impedance is approximately 1.0×10 at a temperature of 20°C to 40°C.
6. kg/rd/s, has large multiple reflections, and is too soft to be used.

As a result of intensive studies to achieve the above object, the inventors of the present invention have discovered that the above object can be achieved by using a silicone resin with a special composition.

To explain this, this silicone (in the formula, R' and R'' are groups selected from substituted or unsubstituted monovalent hydrocarbon groups, at least 80 mol% of R1 is a methyl group, and at least 50 mol% of Rz is a phenylene group). ral group, X is an integer of 5 to 400), and contains 10 to 50 phenyl groups among all organic groups.
It is a cured product of organosiloxane in mol%.

Here, RI and R1 are substituted or unsubstituted monovalent hydrocarbon groups having 1 to 10 carbon atoms, and include alkyl groups such as methyl, ethyl, and propyl groups, vinyl groups, and allyl groups. Examples include cycloalkyl groups such as alkenyl groups and cyclohexyl groups, aryl groups such as phenyl groups and tolyl groups, and halogen-substituted-valent hydrocarbons such as trifluoropropyl groups.

However, at least 80 mol% of R1 is a methyl group R2
Of these, at least 50 mol% of phenyl groups is required. If it is outside this range, it will not have sufficient mechanical strength. In addition, the amount of phenyl groups in all organic groups is 10~
The reason why 50 mol% is essential is that when it is 10 mol% or less, the sound velocity is 1150 o+/s or less and the density is about 1.1 g/C.
Since it is l11, its acoustic impedance (sound speed ×
Density) is 1.25X10bkg/rrr/s or less, and at 50 mol% or more, the sound velocity exceeds 1500a+/s and the density is approximately 1.2g/c4, so the acoustic impedance is 1.8X106kg/rrr/ s or more, and the target acoustic impedance is 1.25 to 1.8.
Not within the range of 0XllO' kg/nf/s.

The reason why X is set to 5 to 400 is to improve mechanical strength, especially brittleness, and a cured product within this range has high toughness and can be cut.

When using an organohydrodiene siloxane as a curing method for this organopolysiloxane, it is essential that the organopolysiloxane has at least 0.1 mol% or more of alkenyl groups, and the organohydrodiene siloxane contains silicon in one molecule. Organohydrodiene polysiloxanes having three or more hydrogen atoms bonded to elementary atoms have no particular restrictions on their molecular structure;
It may be linear (linear), branched, cyclic or network-like, and may be a homopolymer consisting of a single siloxane unit or a block or random copolymer consisting of two or more types of siloxane units. There is no problem with either combination.

There is also no limit to the degree of polymerization, and it includes high degrees of polymerization with a few to several tens of silicon atoms, but from the viewpoint of ease of synthesis, it is preferable to have a few to several hundred silicon atoms. It is considered suitable.

Furthermore, examples of platinum-based compound catalysts include chloroplatinic acid and complexes of chloroplatinic acid and olefins, alcohols, aldehydes, etc., which have a pt amount of about 0.
1-100 ppm is used.

In addition, if the reactive group at the end is a type that hardens through a condensation reaction, such as a hydroxyl group or an alkoxy group, it will be a varnish type with a solvent dissolved in it, and the solvent will need to be dried during molding, and thin layers will be applied over and over again. Although it is cumbersome because the thickness is increased as it is formed, it is a material that is sufficient to achieve the intended purpose in terms of acoustic properties and other physical properties.

Preferably, it is the addition curing type described above.

The reason for this is that thick materials can be molded in a short time and can be directly molded into the desired shape.

The cured silicone resin material described above has an acoustic impedance of 1.25 to 1.80X 10 hkg/rd/s, and an ultrasonic attenuation rate of 2.0 dB/a+m/MHz or less, Not only is the sound velocity around 1,500 m8, which is close to the sound speed of water, but it is also extremely tough, with the brittleness characteristic of cured silicone resins being improved compared to cured silicone resins obtained through normal co-hydrolysis, etc. This material has excellent mechanical properties and can be machined into molded products.

The scope of the present invention will be described in detail below using examples, but the scope of the present invention is as follows:
It is not limited by the examples.

[Example 1] It is a copolymer of
is a phenyl group, 70% of all organic groups are methyl groups, and about 30% are phenyl groups. A varnish-type silicone resin solution is prepared by dissolving a silicone resin with a methyljetoxy group at the end and a condensation catalyst in toluene. Using.

The silicone resin solution was placed in a suitable container, the solvent was slowly evaporated, and the solution was cured by heating at 150° C. for 12 hours, and the same operation was repeated 20 times to form a block with a thickness of 10 aa.

The sound velocity, acoustic impedance and attenuation factor of this block are 1315m8, 1.51xlO' kg/
m/s and 0.4 dB/mn+MHz. The hardness was 85 on the Shore hardness A, and it could be machined such as cutting.

This block was hollowed out to create a window and a mechanical scan type probe was completed. This probe has better temporal resolution than a window made of polyurethane.
A clear image was obtained.

[Example 2] It had almost the same structure as the silicone resin used in Example 1, except that the reactive group was not an ethoxy group, but a vinyl dimethylsiloxane group to enable addition reaction. Polymethylhydrodienesiloxane and a platinum catalyst were added thereto, and after mixing, a block with a diameter of 15 cm was obtained by pressure molding at 150°C for 110 minutes.

The acoustic properties and mechanical properties of this block are almost the same as those of the block obtained in Example 1, and the characteristics of the mechanical scan type probe with a window section cut out of this block are also almost the same as in Example 1. Ta.

Patent applicant: Shin-Etsu Chemical Co., Ltd. 1 other person

Claims (1)

[Claims] Formula ▲ includes mathematical formulas, chemical formulas, tables, etc. ▼ and formula [R^2S
iO_1_. _5] (In the formula, R^1 and R^2 are groups selected from substituted or unsubstituted monovalent hydrocarbon groups, at least 80 mol% of R^1 is a methyl group, and at least 50 mol% of R^2 is a group selected from substituted or unsubstituted monovalent hydrocarbon groups. Mechanical scan using a cured product of organosiloxane containing an organosiloxane unit represented by a phenyl group (where X is an integer of 5 to 400) and in which phenyl groups account for 10 to 50 mol% of all organic groups as a window part. type ultrasound probe.