JP3592448B2 - Ultrasonic probe - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic probe that transmits ultrasonic waves to a subject and receives ultrasonic waves reflected from the subject, and particularly relates to an ultrasonic probe that can obtain an acoustic material having desired specifications. .
[0002]
[Prior art]
In an ultrasonic diagnostic apparatus, a tomographic image of a soft tissue of a subject is obtained by transmitting / receiving an ultrasonic wave to / from the subject using an ultrasound probe.
[0003]
This type of ultrasonic probe uses the piezoelectric effect of piezoelectric ceramics and polymer piezoelectrics to transmit ultrasonic waves corresponding to the applied electric signal to the subject, and to convert the ultrasonic waves from the subject into ultrasonic waves. Generate a corresponding electrical signal.
[0004]
FIG. 9 shows a side view of such an ultrasonic probe main body. The ultrasonic probe main body (vibrator) includes a backing material 11, a piezoelectric body 13, two acoustic matching layers 101a and 101b, and an acoustic lens 17.
[0005]
The backing material 11 absorbs unnecessary vibration in order to generate a short ultrasonic pulse. The piezoelectric body 13 is a piezoelectric vibrator made of a piezoelectric ceramic or the like, is laminated on the upper surface of the backing material 11, and converts an electric pulse into an ultrasonic wave and an ultrasonic pulse into an electric signal.
[0006]
The two acoustic matching layers 101 a and 101 b match the acoustic impedance of the subject with the acoustic impedance dance of the piezoelectric body 13. The acoustic matching layer 101a is laminated on the upper surface of the piezoelectric body 13, and the acoustic matching layer 101b is laminated on the upper surface of the acoustic matching layer 101a. The acoustic lens 17 is made of silicon rubber or the like, and is laminated on the acoustic matching layer 101b to improve a sound field.
[0007]
Electrodes 19a and 19b are provided below the piezoelectric body 13, and a voltage is applied to the electrodes 19a and 19b so that the piezoelectric body 13 mechanically vibrates. The piezoelectric body 13 is cut at a predetermined interval, and a plurality of vibrator pieces (not shown) are formed.
[0008]
As shown in FIG. 10, the ultrasonic probe includes an ultrasonic probe main body 1 including a vibrator, a cable 3 electrically connected to the ultrasonic probe main body 1, and an electric cable connected to the cable 3. The connector 5 is provided. A pulsar and a receiver circuit (not shown) are connected to the connector 5.
[0009]
Such an ultrasonic probe generates an ultrasonic wave according to the voltage applied to the electrodes 19a and 19b, receives the reflected ultrasonic wave, converts the reflected ultrasonic wave into an electric signal, and transmits the electric signal to an ultrasonic diagnostic apparatus main body (not shown). Supply. Then, in the ultrasonic diagnostic apparatus main body, a tomographic image is obtained based on the electric signal supplied from the ultrasonic probe.
[0010]
The transfer characteristics of such an ultrasonic probe are one factor related to the signal / noise ratio (S / N ratio), resolution, and the like of an image. This transfer characteristic is determined depending on the impedance matching characteristic between the probe and the pulsar / receiver circuit serving as the transmission / reception circuit and the exchange characteristic between the electric energy / acoustic energy of the probe itself.
[0011]
Conventionally, in order to optimize this transfer characteristic, the specifications of the optimal piezoelectric material, acoustic matching layer, and backing material that can secure desired characteristics (for example, acoustic impedance, attenuation coefficient) are grasped in advance by calculation on a desk. Had to procure these materials. From the procured materials, a piezoelectric material, an acoustic matching layer, and a backing material were trial-produced to confirm the manufacturability, characteristics, reliability, and the like.
[0012]
In particular, in order to optimize the transfer characteristics of the vibrator, a method for procuring a desired material includes a method of procuring a single material and a method of procuring and mixing a plurality of materials. However, when procured by itself, there is a limit to the materials that can be actually obtained, and there is a problem that it is difficult to obtain a material that satisfies desired specifications.
[0013]
On the other hand, it is conceivable to achieve desired specifications by mixing multiple materials, but it is difficult to mix multiple materials due to the properties of individual materials, differences between these materials, and differences in molding conditions. Material is difficult to realize.
[0014]
On the other hand, when two types of materials are mixed, there is a method in which one material is dissolved, the other material is pulverized, and then the other material is mixed with one material.
[0015]
[Problems to be solved by the invention]
However, it has been difficult to pulverize the material to a sufficiently small and uniform particle size with respect to the order of the wavelength of the ultrasonic wave. Further, the surface area of the material increases according to the degree of pulverization of the material, so that the mixing ratio of a plurality of materials is limited.
[0016]
Furthermore, depending on the relationship between the curing speed of the melted material and the difference in specific gravity between the two materials, various problems often occur, such as a possibility that the mixing ratio may be non-uniform.
[0017]
An object of the present invention is to provide an ultrasonic probe that can easily obtain an acoustic material having desired specifications as compared with a conventional method for an acoustic material obtained by mixing a plurality of types of materials. is there.
[0018]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems. According to the first aspect of the present invention, there is provided a piezoelectric body which is laminated on a base material, converts an electric signal into ultrasonic waves, and converts ultrasonic waves reflected from a subject into electric signals, An ultrasonic probe comprising an acoustic matching layer for matching the acoustic impedance of the piezoelectric body and the acoustic impedance of the piezoelectric body, wherein at least one member of the acoustic matching layer and the base material includes a plurality of types of materials having different acoustic impedances. Is formed from the composite.
[0019]
According to this invention, at least one member of the acoustic matching layer and the base material is formed from a composite in which a plurality of types of materials having different acoustic impedances are combined, so that a plurality of types of materials are mixed. For such an acoustic material, an acoustic material having desired specifications can be easily obtained as compared with the conventional method.
[0020]
The invention according to claim 2 is characterized in that, when each material of the composite is sequentially and repeatedly arranged, the length of the repetition period of each material is set to be equal to or less than the wavelength of the ultrasonic wave with respect to the average sound speed of the composite. And
[0021]
According to the present invention, when the respective materials of the composite are sequentially and repeatedly arranged, the length of the repetition period of each material is set to be equal to or less than the wavelength of the ultrasonic wave with respect to the average sound speed of the composite. Since the material is approximately regarded as one uniform material, the material is treated as a uniform transmission characteristic, and thus a desired characteristic is easily obtained.
[0022]
According to the invention of claim 3, a groove is formed in one of the plurality of types of materials, and the other is filled and cured in the groove, and the filling and curing process is performed for each of the remaining materials. And forming the complex.
[0023]
According to the present invention, a groove is formed in one of a plurality of types of materials, and the groove is filled with another material and cured, and the filling and curing process is performed for each of the remaining materials. , Forming the complex.
[0024]
That is, since individual materials are sequentially formed, it is hardly affected by differences in properties and molding conditions between materials, which have conventionally been a problem when mixing a plurality of materials.
[0025]
In addition, even when a plurality of materials are mixed by pulverization, it is possible to avoid a problem of achieving a sufficiently small and uniform particle size with respect to the wavelength order and a non-uniform mixing ratio due to a difference in specific gravity between the materials.
[0026]
As a result, the range of achievable acoustic materials can be expanded, whereby the transfer characteristics of the probe can be asymptotically approximated to the optimum characteristics that were previously obtained by calculation on a desk.
[0027]
According to a fourth aspect of the invention, at least one member of the acoustic matching layer and the base material is configured such that a single body made of a single kind of material and the composite are continuously laminated.
[0028]
According to the present invention, at least one member of the acoustic matching layer and the base material is formed by continuously laminating a single body made of a single kind of material and the composite, so that desired characteristics can be obtained. And the adhesive layer between the single body and the composite can be omitted.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the ultrasonic probe of the present invention will be described with reference to the drawings. In the present invention, description will be given focusing on acoustic impedance as one of the specifications of the acoustic material calculated by the examination on the desk.
[0030]
(Embodiment 1)
FIG. 1 is a perspective view of an ultrasonic probe according to a first embodiment of the present invention. In the first embodiment, in the case of realizing an acoustic material using a plurality of types of materials, one material in which a groove is formed in advance is prepared, and then the other material is filled into the groove and cured. That is, a desired acoustic material is realized by sequentially forming individual materials.
[0031]
Here, a case of an acoustic material configured by combining two types of materials will be described. FIG. 2 shows a side view of the ultrasonic probe according to the first embodiment.
[0032]
The ultrasonic probe shown in FIG. 2 has an ultrasonic probe main body (vibrator) including a backing material 11 as a base material, a piezoelectric body 13, two acoustic matching layers 15a and 15b, and an acoustic lens 17. .
[0033]
The backing material 11 absorbs unnecessary vibration to generate a short ultrasonic pulse. The piezoelectric body 13 is laminated on the upper surface of the backing material 11, converts electric pulses into ultrasonic waves and converts ultrasonic pulses into electric signals, and is a piezoelectric vibrator made of piezoelectric ceramics or the like.
[0034]
The two acoustic matching layers 15a and 15b match the acoustic impedance of the subject with the acoustic impedance dance of the piezoelectric body 13. The acoustic matching layer 15a is laminated on the upper surface of the piezoelectric body 13, and the acoustic matching layer 15b is laminated on the upper surface of the acoustic matching layer 15a. The acoustic lens 17 is laminated on the acoustic matching layer 15b, and is made of silicon rubber or the like to improve a sound field.
[0035]
Electrodes 19a and 19b are provided below the piezoelectric body 13, and a voltage is applied to the electrodes 19a and 19b so that the piezoelectric body 13 mechanically vibrates to generate ultrasonic waves. The piezoelectric body 13 is cut at a predetermined interval, and a plurality of vibrator pieces (not shown) are formed.
[0036]
In the acoustic matching layer 15b, an epoxy resin 21 as a first material and a silicon resin 23 as a second material are alternately and repeatedly arranged in a transducer array direction (hereinafter, referred to as an array direction). The epoxy resin 21 and the silicon resin 23 are alternately and repeatedly arranged in a direction perpendicular to the vibrator array direction (hereinafter, referred to as a slice direction).
[0037]
That is, the acoustic matching layer 15b is composed of a composite obtained by combining the epoxy resin 21 and the silicon resin 23 in a lattice shape as seen from the upper surface.
[0038]
In the acoustic matching layer 15a, the epoxy resin 21 and the silicon resin 25 are alternately and repeatedly arranged in the array direction, and the epoxy resin 21 and the silicon resin 25 are alternately and repeatedly arranged in the slice direction. It is composed.
[0039]
That is, the acoustic matching layer 15a is also composed of a composite formed by combining the epoxy resin 21 and the silicon resin 25 in a lattice shape.
[0040]
Next, a method for manufacturing such acoustic matching layers 15a and 15b will be described with reference to FIG.
[0041]
First, the epoxy resin 21 is cured using an appropriate mold, and a reference surface is created by grinding and polishing. Thereafter, a groove 31 is formed on a surface facing the reference surface using a cutting machine capable of high-precision positioning (step S1), and then a groove 33 is formed (step S3). At this time, the epoxy resin 21 becomes a columnar body as shown in FIG.
[0042]
Then, the silicon resin 23 is filled in the groove 31 and the groove 33 under a reduced pressure environment and cured (step S5). Finally, the acoustic matching layers 15a and 15b made of a composite having a desired thickness are formed by grinding and polishing.
[0043]
The acoustic impedance of the epoxy resin 21 of the acoustic matching layer 15b is about 3 [Mrayls], and the acoustic impedance of the silicon resin 23 is about 1 [Mrayls].
[0044]
Here, the composite volume ratio of the epoxy resin 21 of the acoustic matching layer 15b is V _A, the composite volume ratio of the silicon resin 23 is assumed to be V _B, the average acoustic impedance of the composite, V _A × Z It is approximated by _A + _{V B} × _{Z B.}
[0045]
Therefore, if the acoustic impedance of the target acoustic material is determined, an appropriate material can be selected from existing materials and composited, and an acoustic material having desired specifications can be realized.
[0046]
For example, when an acoustic material having an acoustic impedance of 2.5 [Mrayls] is required, the composite volume ratio of the epoxy resin 21 as the first material is set to 75%, and the composite of the silicon resin 23 as the second material is set. If the volume ratio is 25 [%], a composite having an acoustic impedance of 2.5 [Mrayls] can be easily obtained.
[0047]
As described above, according to the first embodiment, it is easier to realize an acoustic material obtained by mixing a plurality of materials than in the conventional method. That is, since the individual materials are sequentially formed, they are less susceptible to differences in properties and molding conditions between the materials, which have conventionally been a problem in mixing.
[0048]
In addition, even when a plurality of materials are mixed by pulverization, it is possible to avoid a problem of achieving a sufficiently small and uniform particle size with respect to the wavelength order and a non-uniform mixing ratio due to a difference in specific gravity between the materials.
[0049]
As a result, the range of achievable acoustic materials can be expanded, whereby the transfer characteristics of the probe can be asymptotically approximated to the optimum characteristics that were previously obtained by calculation on a desk.
[0050]
The sound speed of the epoxy resin 21 as the first material is about 2700 [m / sec], and the sound speed of the silicon resin 23 as the second material is about 1000 [m / sec]. Thus, the average sound velocity of the composite is approximated to _{V A × C A + V B} × C B.
[0051]
Further, the length P (the portion shown in FIG. 2) of the repetition period of each material constituting the composite is set to be equal to or less than the wavelength of the ultrasonic wave with respect to the average sound speed of the composite. For this purpose, the frequency of the ultrasonic wave when the fc [MHz], the wavelength is calculated based on an average acoustic velocity _{λ C (V A × C A} + V B × C B) / fc [m] On the other hand, the length P of the repetition period is set so as to satisfy λ _C > P [m].
[0052]
For example, when the frequency of the ultrasonic wave is 7.5 [MHz], the wavelength is 0.27 [mm] with respect to the composite volume ratio. Each material may be compounded by the length P of the repetition period equal to or less than this wavelength.
[0053]
As shown in FIG. 4A, when the length P of the repetition period is set smaller than the wavelength λ _C , when the composite is viewed from the ultrasonic wave, the composite is approximately a uniform material. Therefore, since the transmission characteristics are treated as uniform transmission characteristics, desired transmission characteristics are easily obtained.
[0054]
On the other hand, as shown in FIG. 4B, when the length P of the repetition period is set to be longer than the wavelength λ _C , when the composite is viewed from the ultrasonic wave, the composite is regarded as a plurality of materials. . That is, it is difficult to obtain a desired transmission characteristic when a plurality of materials are combined.
[0055]
In the first embodiment, when forming the groove portions 31 and 33, a cutting machine capable of high-precision positioning with respect to the cured epoxy resin 21 is used. The groove 31 and the groove 33 may be formed by curing and molding using a mold having a structure. Similarly, as the material, a thermosetting polymer, a thermoplastic polymer, or the like may be used.
[0056]
In the first embodiment, the acoustic matching layers 15a and 15b are formed as a composite. However, for example, the backing material 11 may be formed as a composite formed of an epoxy resin 21 and a silicon resin 23. Further, the acoustic matching layers 15a and 15b and the backing material 11 may be the composite.
[0057]
Further, the composite volume ratio of the epoxy resin 21 and the silicon resin 23 is not limited to the ratio in Embodiment 1, and may be determined according to the specification value and the characteristics and type of the combined material.
[0058]
(Embodiment 2)
Next, an ultrasonic probe according to a second embodiment of the present invention will be described. FIG. 5 is a perspective view of the ultrasonic probe according to the second embodiment.
[0059]
In the second embodiment, the configuration of the backing material 11a is different from the configuration of the first embodiment. Note that an acoustic lens 17 (not shown) is laminated on the acoustic matching layer 15b.
[0060]
The backing material 11a is made of a material having a thickness t, and has a laminated structure of a composite body composed of an epoxy resin 21 and a silicon resin 23 having an upper thickness t1 and a single body composed of an epoxy resin 21 having a lower thickness (t-t1). Consists of That is, the single body of the epoxy resin 21 is also used as the acoustic material.
[0061]
The backing material 11a having such a configuration is formed by leaving the epoxy resin 21 by a required thickness (t-t1) in the final grinding / polishing process of the first embodiment.
[0062]
By performing lamination with such a structure, an unnecessary adhesive layer between a single body and a composite body can be eliminated in terms of acoustic characteristics, which is useful for optimizing the transfer characteristics of the probe.
[0063]
Further, as the backing material 11a, silicon rubber may be used instead of the epoxy resin 21, and alumina-araldite may be used instead of the silicon resin 23.
[0064]
In this case, the acoustic impedance of alumina araldite is about 7.6 [Mrayls], and the acoustic impedance of silicon rubber is about 1 [Mrayls].
[0065]
If the composite volume ratio of alumina / araldite is 30 [%] and the composite volume ratio of silicon rubber is 70 [%], a composite having an acoustic impedance of 3 [Mrayls] can be easily obtained. By changing this ratio, the acoustic impedance of the composite can be varied.
[0066]
In the second embodiment, the backing material 11a has a laminated structure of a single body and a composite. However, for example, each of the acoustic matching layers 15a and 15b may have a laminated structure of the composite and the single body. .
[0067]
(Embodiment 3)
Next, a third embodiment of the ultrasonic probe according to the present invention will be described. FIG. 6 is a perspective view of the ultrasonic probe according to the third embodiment. In the first and second embodiments, a composite in which two kinds of materials are combined has been described. However, as shown in FIG. 6, a composite in which each of the acoustic matching layers 15c and 15d combines three kinds of materials. Consists of the body. Note that an acoustic lens 17 (not shown) is stacked on the upper surface of the acoustic matching layer 15d.
[0068]
The acoustic matching layer 15d includes an epoxy resin 21 as a first material and a silicon resin 23 as a second material alternately and repeatedly arranged in a slice direction, and an epoxy resin 21 and a third resin in the array direction. The material 26 is arranged alternately and repeatedly.
[0069]
That is, the acoustic matching layer 15b is made of a composite formed by combining the epoxy resin 21, the silicon resin 23, and the third material 26 in a lattice shape, as can be seen from the upper surface. The acoustic matching layer 15c is also composed of a composite having substantially the same configuration as the acoustic matching layer 15d.
[0070]
Next, a method of manufacturing such acoustic matching layers 15c and 15d will be described with reference to FIG.
[0071]
First, the epoxy resin 21 is cured using an appropriate mold, and a reference surface is created by grinding and polishing. Thereafter, a groove 31 is formed on the surface facing the reference surface using a cutting machine capable of high-precision positioning (step S11), and the groove 31 is filled with the silicon resin 23 under a reduced pressure environment and cured. (Step S13).
[0072]
Next, a groove 33 is formed (Step S15), and the groove 33 is filled with the third material 26 under a reduced pressure environment and cured (Step S17). Finally, the acoustic matching layers 15c and 15d made of a composite having a desired thickness are formed by grinding and polishing.
[0073]
Thus, when the composite is made of three types of materials, it becomes easier to obtain a desired acoustic impedance.
[0074]
When three or more types of composite materials are used, a composite can be manufactured in the same manner as in Embodiment 3 described above. Further, in the third embodiment, the acoustic matching layers 15c and 15d are made of a composite made of three kinds of materials. However, for example, the backing material 11 may be made of a composite made of three kinds of materials.
[0075]
(Embodiment 4)
Next, an ultrasonic probe according to a fourth embodiment of the present invention will be described. FIG. 8 shows a perspective view of the ultrasonic probe according to the fourth embodiment.
[0076]
In the fourth embodiment, the configuration of the backing material 11a is different from the configuration of the third embodiment. Note that an acoustic lens 17 (not shown) is stacked on the upper surface of the acoustic matching layer 15d.
[0077]
The backing material 11a is made of a material having a thickness t, and has a laminated structure of a composite body composed of an epoxy resin 21 and a silicon resin 23 having an upper thickness t1 and a single body composed of an epoxy resin 21 having a lower thickness (t-t1). Consists of That is, the single body of the epoxy resin 21 is also used as the acoustic material.
[0078]
The backing material 11a having such a configuration is formed by leaving the epoxy resin 21 by a required thickness (t-t1) in the final grinding / polishing process of the first embodiment.
[0079]
By performing lamination with such a structure, an unnecessary adhesive layer between a single body and a composite body can be eliminated in terms of acoustic characteristics, which is useful for optimizing the transfer characteristics of the probe.
[0080]
In the fourth embodiment, the backing material 11a has a laminated structure of a single body and a composite, but for example, each of the acoustic matching layers 15c and 15d may have a laminated structure of the composite and the single body. .
[0081]
【The invention's effect】
According to the present invention, since at least one member of the acoustic matching layer and the base material is formed from a composite in which a plurality of types of materials having different acoustic impedances are combined, the plurality of types of materials are mixed. With respect to the acoustic material, an acoustic material having desired specifications can be easily obtained as compared with the conventional method.
[0082]
In addition, when each material of the composite is arranged in order and repeatedly, the length of the repetition period of each material is set to be equal to or less than the wavelength of the ultrasonic wave with respect to the average sound speed of the composite, so that the composite has one uniform Since the material is approximately regarded as a material, it is treated as a uniform transmission characteristic, so that desired characteristics are easily obtained.
[0083]
Further, a groove is formed in one of a plurality of types of materials, and the other portion is filled and cured in the groove, and the filling and curing process is performed for each of the remaining materials. To form
[0084]
That is, since individual materials are sequentially formed, it is hardly affected by differences in properties and molding conditions between materials, which have conventionally been a problem when mixing a plurality of materials. In addition, even when a plurality of materials are mixed by pulverization, it is possible to avoid a problem of achieving a sufficiently small and uniform particle size with respect to the wavelength order and a non-uniform mixing ratio due to a difference in specific gravity between the materials.
[0085]
As a result, the range of achievable acoustic materials can be expanded, whereby the transfer characteristics of the probe can be asymptotically approximated to the optimum characteristics that were previously obtained by calculation on a desk.
[0086]
Furthermore, since at least one member of the acoustic matching layer and the base material is formed by continuously laminating a single body made of a single kind of material and the composite, desired characteristics are easily obtained, and The adhesive layer between the and the composite can be omitted.
[Brief description of the drawings]
FIG. 1 is a perspective view of an ultrasonic probe according to a first embodiment of the present invention.
FIG. 2 is a side view of the ultrasonic probe of the present invention.
FIG. 3 is a diagram for explaining a method of manufacturing the composite according to the first embodiment.
FIG. 4 is a diagram illustrating the relationship between the length of the repetition period of the complex and the wavelength of the ultrasonic wave.
FIG. 5 is a perspective view of an ultrasonic probe according to a second embodiment of the present invention.
FIG. 6 is a perspective view of an ultrasonic probe according to a third embodiment of the present invention.
FIG. 7 is a diagram for explaining a method for manufacturing a composite according to the third embodiment.
FIG. 8 is a perspective view of an ultrasonic probe according to a fourth embodiment of the present invention.
FIG. 9 is a side view of a conventional ultrasonic probe.
FIG. 10 is a diagram showing a schematic configuration of an ultrasonic probe.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ultrasonic probe main body 3 Cable 5 Connector 11, 11a Backing material 13 Piezoelectric body 15a-15d Acoustic matching layer 17 Acoustic lens 19a, 19b Electrode 21 Epoxy resin 23 Silicon resin 26 Third material 31, 33 Groove

Claims (4)

A piezoelectric body that is laminated on the base material and converts an electric signal into an ultrasonic wave and converts ultrasonic waves reflected from the subject into an electric signal, and a piezoelectric body that is laminated on the piezoelectric body and has an acoustic impedance of the subject and a piezoelectric substance. In an ultrasonic probe having an acoustic matching layer that performs matching with acoustic impedance,
An ultrasonic probe, wherein at least one member of the acoustic matching layer and the substrate is formed of a composite in which a plurality of types of materials having different acoustic impedances are composited. 2. The method according to claim 1, wherein when arranging the respective materials of the composite sequentially and repeatedly, the length of the repetition period of each material is set to be equal to or less than the wavelength of the ultrasonic wave with respect to the average sound speed of the composite. Ultrasonic probe. A groove is formed in one of the plurality of types of materials, and the groove is filled with another material and cured, and the filling and curing process is performed for each of the remaining materials to form the composite. The ultrasonic probe according to claim 1, wherein the ultrasonic probe is formed. 3. The at least one member of the acoustic matching layer and the base material, wherein a single body made of a single kind of material and the composite are continuously laminated. 4. The ultrasonic probe according to claim 3.

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