JPH0221253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasound probe used in a medical ultrasound diagnostic apparatus.

Structure of conventional example and its problems A conventional ultrasonic probe, particularly a probe used in a medical ultrasonic diagnostic apparatus, generally has a structure as shown in FIG. FIG. 1 shows a general structure used in a linear electronic scanning ultrasonic probe in which strip-shaped piezoelectric vibrators are arranged in a straight line.

The one in Fig. 1 has a structure in which one or more acoustic matching layers 2 are provided on a piezoelectric vibrator 1, and an electrical signal controlled from the outside is sent to an electrode 4 provided in the vibration direction of the piezoelectric vibrator 1. By applying ultrasound 6
is radiated from the acoustic matching layer 2 side, and a back loading material 5 is provided on the opposite side of the acoustic matching layer 2 of the piezoelectric vibrator 1.
It has a configuration with. This back load material 5 is generally made of a relatively hard material (hardness (JIS-A) of 85 or more) such as plastic material filled with tungsten powder or ferrite rubber, and has an acoustic impedance of 6×10 ⁵ g/cm ² . sec or more and has a large absorption of sound waves, or a gel-like material made of silicone rubber filled with alumina oxide etc. and whose acoustic impedance is 1.5×10 ⁵ g/cm ²・sec or less. There is. Note that the sound wave absorption coefficient of these materials is approximately 1.5 dB/mm (3 MHz) or higher.

If the former material is used as the back loading material 5, it has the advantage of high mechanical strength due to its high hardness and less damage to the probe vibrator surface, but the acoustic impedance is 6 x 10 ⁵ g/cm. ² sec or more, and the acoustic impedance of piezoelectric vibrator 1 (in the case of piezoelectric ceramic, the acoustic impedance is 30×10 ⁵
It is around g/cm ² ·sec. ), the acoustic matching is relatively better in the latter case, but the latter has the disadvantage that the sound waves propagate also to the back load material 5 side, resulting in a decrease in sensitivity. On the other hand, when the latter material is used as the back load material 5, the acoustic impedance is 1 to 1.5×10 ⁵ g/contrary to the former.
cm ² ·sec, and due to the acoustic mismatch with the piezoelectric vibrator 1, the propagation of the sound wave toward the back load material 5 side becomes smaller. Therefore, compared to the former, it has the advantage of less deterioration in sensitivity. However, the back load material 5
Since it is soft, it has the disadvantage that the probe is easily damaged by mechanical shock or pressure applied to the probe vibrator surface.

Purpose of the Invention The present invention has been made in order to solve the above-mentioned conventional problems, and is equipped with a new back-loading material that reduces sensitivity loss, increases mechanical strength, and eliminates the disadvantage of breakage. The purpose of the present invention is to provide an ultrasonic probe with improved characteristics.

Structure of the Invention In order to achieve this object, an ultrasonic probe according to the present invention comprises at least a piezoelectric vibrator, a single layer or multilayer acoustic composite layer, and a back load, and the back load has a predetermined hardness. , a sound wave absorption coefficient, and an acoustic impedance.

DESCRIPTION OF EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 2 is a perspective view showing an embodiment of the present invention, in which single-layer or multi-layer acoustic matching layers 12 and 13 are provided on the side of the piezoelectric vibrator 11 in contact with the subject, and if necessary, acoustic matching layers 12 and 13 are provided. A lens 17 is provided. A back load material 15 is provided on the opposite side of the piezoelectric vibrator 11.
A back load material 15 formed by pouring or molding is bonded. Note that one end surface of the back load material 15 may have an uneven structure in order to scatter ultrasonic waves. Use the one you made. For example, Adapt E-No.1 (manufactured by Kokusai Chemical)
In the case of urethane rubber, the acoustic impedance is
2.1×10 ⁵ g/cm ²・sec, hardness (JIS-A) is 98
The acoustic absorption coefficient is 2 dB/mm at 3 MHz. Furthermore, when using the above urethane rubber and filling 15% by weight of glass hollow bodies with a particle size of around 100 μm, the acoustic impedance is 1.7 × 10 ⁵ g/cm ² sec.
The hardness (JIS-A) is 98 to 99, and the sound absorption coefficient is 2.5 dB/mm at 3 MHz.

In order to eliminate unnecessary reflection of sound waves from the end surface of the back load material 15 facing the surface to which the piezoelectric vibrator 11 is attached, and furthermore to obtain a wide signal dynamic range, it is necessary to use a material with a large sound wave absorption coefficient. Back loading material is preferred. For example, dynamite cleanse
If 100dB is required, the above sound wave absorption coefficient
For the material of this example with a rating of 2.5 dB/mm, the thickness must be 20 mm in order to eliminate the reflection of sound waves from the end face of the back load material.
The above is sufficient, and there is no inferiority to that of a conventional smoke sonic probe.

In addition, some urethane rubbers have a hardness of approximately 85, an acoustic impedance of approximately 3 x 10 ⁵ g/cm ² sec, and a sound wave absorption coefficient of approximately 1.5 to 2 dB/mm at 3 MHz.
This can be used as it is as the back load material 15 of this embodiment. Of course, in terms of sensitivity, the lower the acoustic impedance of the back load, the better, but by varying the filling amount of the glass hollow body based on the urethane rubber mentioned above, the acoustic impedance can be reduced while maintaining the hardness and sound wave absorption coefficient at approximately the above levels. It was possible to lower the value to about 1×10 ⁵ g/cm ² ·sec. In this case, considering viscosity etc., the lower limit of the acoustic impedance is industrially 1×10 ⁵ g/cm ² ·sec, and the acoustic impedance of the back load material 15 is 1 to 3×10 ⁵ g/cm ² · Preferably sec. This is compared to the case without back load.
The maximum sensitivity decrease is about 2 dB, but the sensitivity decrease of about 2 dB is acceptable in terms of device design or clinical application. We were able to achieve almost the same sensitivity as when using a back-loaded material.

The hardness of the back loading material 15 is directly related to the mechanical strength of the probe, and the harder it is, the better, but the value at which mechanical damage to the transducer surface does not pose a practical problem is 85 (JIS
-A) That's all. By the way, in the case of this example,
In terms of hardness, it is approximately equal to or higher than ferrite rubber, which is said to be resistant to mechanical damage, and is approximately 10 times more durable than gel-like back loading materials such as silicone rubber. We were able to improve the strength.

Furthermore, it goes without saying that the larger the acoustic wave absorption coefficient of the back loading material 15, the thinner the thickness of the back loading material 15 can be. It becomes difficult to satisfy. Considering these points, it is practically desirable that the sound wave absorption coefficient is 1.5 dB/mm or more (3 MHz). For example, as described in the above embodiment, the sound wave absorption coefficient is 1.5 to
When using a probe using a 2.5 dB/mm (3 MHz) back load material 15 connected to an ultrasonic diagnostic device with a display dynamic range of 100 dB, in order to eliminate reflections from the end face of the back load. The thickness is 20~
34mm, which allows the ultrasonic probe to be configured without significantly increasing its external dimensions.

Furthermore, the back load material according to this example can also be manufactured by pouring the material after all the piezoelectric vibrators, acoustic matching layers, acoustic ranges, etc. have been constructed.
It is also possible to manufacture the piezoelectric vibrator by molding the backside load material in advance with a mold of a predetermined shape, and then bonding the formed backside load material (block) to the piezoelectric vibrator.

In the above embodiment, the acoustic impedance was controlled by filling the urethane rubber with a glass hollow body, but the same effect was obtained when the urethane rubber was filled with a plastic hollow body.

Furthermore, in the embodiment, a case has been described in which the piezoelectric vibrators are applied to a so-called array type ultrasonic probe in which the piezoelectric vibrators are arranged in a linear manner. It is clear that the present invention can be applied to various ultrasonic probes such as a probe and an arcuate array type ultrasonic probe.

Effects of the Invention As described above, according to the present invention, one of the sound wave transmitting and receiving sides of the piezoelectric vibrator that transmits and receives sound waves has an acoustic impedance of 1.0×10 ⁵ to 3×10 ⁵ g/cm ² ·sec,
The present invention provides an ultrasonic probe equipped with a material with hardness (JIS-A) of 85 or higher and an ultrasonic absorption coefficient of 1.5 dB/mm or higher at a frequency of 3 MHz as a back load. Signals are less likely to propagate to the backside load material, preventing a decrease in sensitivity and providing a wide dynamic range. Furthermore, since it has high hardness, it has high mechanical strength and can prevent damage to the transducer surface of the probe. Therefore, it has the advantage that a highly reliable probe can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional ultrasound probe, and FIG. 2 is a perspective view of an ultrasound probe according to an embodiment of the present invention. 11... Piezoelectric vibrator, 12, 13... Acoustic matching layer, 15... Back load material, 17... Acoustic lens.

Claims (1)

[Claims] 1. Acoustic impedance is 1.0×10 ⁵ to 3× on one sound wave transmitting/receiving side of the piezoelectric vibrator that transmits and receives sound waves.
10 ⁵ g/cm ² sec, hardness (JIS-A) of 85 or more, and an ultrasonic absorption coefficient of 1.5 dB/mm or more at a frequency of 3 MHz provided as a back load. Child. 2. The ultrasonic probe according to claim 1, characterized in that urethane rubber is used for the back load. 3. The ultrasonic probe according to claim 1, characterized in that a material made of urethane rubber filled with glass hollow bodies or plastic hollow bodies is used for back loading.