Ultrasonic probe

Abstract

To improve image quality of an ultrasonogram.SOLUTION: An ultrasonic probe includes an oscillator group and an acoustic lens. The oscillator group includes a plurality of ultrasonic transducers. The acoustic lens is provided on a transmission and reception side of the oscillator group and includes a first curved surface and a second curved surface that correspond to at least an acoustic effective aperture of the oscillator group. A sound speed of the acoustic lens is faster than a sound speed of a first medium in contact with the first curved surface and is faster than a sound speed of a second medium in contact with the second curved surface or a sound speed of a soft tissue in contact with the second curved surface. The first curved surface is a concave surface and faces the transmission and reception side. The second curved surface is a concave surface and faces the first curved surface. A curvature radius of the first curved surface is different from a curvature radius of the second curved surface.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The embodiments disclosed in this specification and the drawings relate to an ultrasonic probe.

Background Art

[0002] Generally, an ultrasonic probe has an acoustic lens that converges an ultrasonic beam in a slice direction. The acoustic lens converges the ultrasonic beam by utilizing refraction due to the difference in the speed of sound with the contacting medium (for example, the body surface). The focal length of the acoustic lens is based on, for example, the radius of curvature of the curved surface that is the boundary between the acoustic lens and the medium (that is, the radius of curvature of the curved surface of the acoustic lens).

[0003] Also, when an ultrasonic beam propagates through an interface with different acoustic impedances, a part of it is reflected and the rest is transmitted. At this time, the larger the incident angle of the ultrasonic beam with respect to the boundary with different acoustic impedances, the larger the reflectivity of the ultrasonic beam.

[0004] By the way, there is a high-frequency probe for the purpose of depicting tissues (superficial tissues) in a shallow part from the body surface in an ultrasonic probe. In a high-frequency probe, a plano-concave lens may be used as the acoustic lens. A plano-concave lens is a lens with one flat surface and the other concave surface.

[0005] In a high-frequency probe using a plano-concave lens as the acoustic lens, since it is necessary to shorten the focal length for the purpose of depicting superficial tissues, it is necessary to reduce the radius of curvature of the concave surface. However, when the radius of curvature of the concave surface is reduced, the incident angle of the ultrasonic beam increases, so the reflectivity of the ultrasonic beam increases. When the reflectivity of the ultrasonic beam is large, the radiation efficiency of the ultrasonic beam incident on the body surface decreases, and the influence of artifacts due to multiple reflections of the ultrasonic beam in the acoustic lens increases. Therefore, in an ultrasonic probe, a decrease in the reflectivity of the ultrasonic beam on the surface of the acoustic lens can be a factor in reducing the image quality of the ultrasonic image.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] One of the problems to be solved by the embodiments disclosed in this specification and the drawings is to improve the image quality of ultrasonic images. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. The problems corresponding to the respective effects of each configuration shown in the embodiments described later can also be regarded as other problems.

Means for Solving the Problems

[0008] The ultrasonic probe according to the embodiment includes a vibrator group and an acoustic lens. The vibrator group has a plurality of ultrasonic vibrators. The acoustic lens is provided on the transmission / reception side of the vibrator group and has at least a first curved surface and a second curved surface corresponding to the acoustic effective aperture of the vibrator group. The speed of sound of the acoustic lens is faster than the speed of sound of the first medium in contact with the first curved surface and faster than the speed of sound of the second medium in contact with the second curved surface or the speed of sound of the soft tissue in contact with the second curved surface. The first curved surface is a concave surface facing the transmission / reception side. The second curved surface is a concave surface facing the first curved surface. The radius of curvature of the first curved surface is different from the radius of curvature of the second curved surface.

Brief Description of the Drawings

[0009]

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Figure 2

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Figure 14

[0010] Hereinafter, embodiments of the ultrasonic probe will be described in detail with reference to the drawings.

[0011] (First Embodiment) FIG. 1 is a diagram illustrating the appearance of an ultrasonic probe 100 according to the first embodiment. The ultrasonic probe 100 corresponds to, for example, a high-frequency linear probe. The ultrasonic probe 100 executes an ultrasonic scan on a scan region in a living body in accordance with control from an ultrasonic diagnostic apparatus. Hereinafter, the ultrasonic beam generated by the ultrasonic scan is referred to as an ultrasonic beam.

[0012] The appearance of the ultrasonic probe 100 is composed of a tip cover 110 (which may be simply referred to as a “cover”) and a case 120. The tip cover 110 is provided at the tip of the ultrasonic probe 100. Hereinafter, the specific configuration of the ultrasonic probe 100 will be described with reference to FIG. 2.

[0013] Hereinafter, the X-axis is set in the slice direction (also referred to as the elevation direction), which is the long side direction of the ultrasonic vibrator (also simply referred to as a vibrator), the Y-axis is set in the scan direction (also referred to as the lateral direction), which is the direction in which the vibrators are arranged, and the Z-axis is set in the acoustic radiation direction in which the ultrasonic beam is radiated.

[0014] FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. Further, FIG. 2 shows a part of the cross-section of the ultrasonic probe 100 in the slice direction. As shown in FIG. 2, the ultrasonic probe 100 includes a tip cover 110 and a case 120, and further includes an acoustic lens 210, an adhesive layer 220, an acoustic matching layer 230, and a vibrator group 240. Note that the configuration after the backing material provided in the vibrator group 240 is not shown.

[0015] The tip cover 110 is formed of, for example, polybutadiene (also referred to as butadiene rubber). The speed of sound of the ultrasonic beam passing through the tip cover 110 is substantially the same as the speed of sound of the ultrasonic beam passing through the soft tissue of the living body. The tip cover 110 is formed so as to cover at least the radiation surface of the acoustic lens 210, which is the surface from which the ultrasonic beam is radiated. Further, the tip cover 110 is joined to the radiation surface without a gap. In the example of FIG. 2, the tip cover 110 is formed so as to cover substantially the entire acoustic lens 210.

[0016] Hereinafter, the "speed of sound of the ultrasonic beam passing through the tip cover" will simply be referred to as the "speed of sound of the tip cover". The same applies to other components or the soft tissue of the living body. Also, the material forming each component (for example, polybutadiene in the case of the tip cover) may be used as a single material or as a main material.

[0017] The case 120 is formed of, for example, polycarbonate resin and ABS resin. The case 120 houses the above-described components incorporated in the ultrasonic probe 100 and is also used as a handle. In the example of FIG. 2, the case 120 houses the acoustic matching layer 230 and the oscillator group 240.

[0018] The acoustic lens 210 is formed of, for example, a material mainly composed of polymethylpentene. The acoustic lens 210 has two curved surfaces such that the thickness at the central portion in the slice direction is thinner than the thickness at the peripheral portion. The two curved surfaces are each concave. The acoustic lens 210 includes a region forming a biconcave lens. The two curved surfaces are formed on the incident surface and the radiation surface of the acoustic lens 210, respectively. The radiation surface of the acoustic lens 210 is joined to the tip cover 110 without a gap. The incident surface of the acoustic lens 210 is joined to the acoustic matching layer 230 via the adhesive layer 220. In the example of FIG. 2, the acoustic lens 210 is covered by the tip cover 110 except for the incident surface. Note that both the first curved surface and the second curved surface may be called concave lenses.

[0019] The adhesive layer 220 is, for example, a silicone-based adhesive. The adhesive layer 220 joins the acoustic lens 210 and the acoustic matching layer 230.

[0020] The acoustic matching layer 230 is formed of, for example, an epoxy resin. The acoustic matching layer 230 is joined to the acoustic lens 210 via the adhesive layer 220. The acoustic matching layer 230 performs acoustic impedance matching (impedance matching) between the oscillator group 240 and the body surface (or a structure provided between the acoustic matching layer 230 and the body surface). Note that the acoustic matching layer 230 may be configured by laminating a plurality of materials having different acoustic impedances.

[0021] The oscillator group 240 has a plurality of ultrasonic oscillators and is arranged in the scanning direction. The ultrasonic oscillator is formed of, for example, a piezoelectric ceramic material (e.g., lead zirconate titanate) or a polymer electronic film material (e.g., polyvinylidene fluoride). The oscillator group 240 is joined to the acoustic lens 210 via the acoustic matching layer 230 and the adhesive layer 220. Note that, with respect to the oscillator group 240, the side that transmits and receives the ultrasonic beam may be referred to as the transmission / reception side.

[0022] FIG. 3 is an explanatory diagram of the acoustic lens 210 in FIG. 2. The acoustic lens 210 has a first region 211 corresponding to the acoustic effective aperture A ef and a second region 212 other than that. The acoustic effective aperture A ef corresponds to, for example, the length in the slice direction of the ultrasonic oscillator. The first region 211 has a first curved surface 310 formed on the incident surface of the acoustic lens 210 and a second curved surface 320 formed on the radiation surface of the acoustic lens 210. The first curved surface 310 and the second curved surface 320 may have the same curvature (may have the same radius of curvature), or may have different curvatures (may have different radii of curvature).

[0023] In other words, the acoustic lens 210 is provided on the transmission / reception side of the oscillator group 240 and has a first curved surface 310 and a second curved surface 320 corresponding to at least the acoustic effective aperture A ef of the oscillator group 240. The first curved surface 310 is a concave surface facing the transmission / reception side, and the second curved surface 320 is a concave surface facing the first curved surface 310.

[0024] FIG. 4 is an explanatory diagram regarding the sound velocities of the tip cover 110, the acoustic lens 210, and the adhesive layer 220 in FIG. 2. The tip cover 110, the acoustic lens 210, and the adhesive layer 220 have sound velocities of c m2 , c l , and c m1 , respectively. For example, if c l >c m2 and c l >c m1 , they are made of materials that satisfy these relationships. According to this configuration, due to the biconcave lens of the acoustic lens 210, the acoustic lens 210 can converge the ultrasonic beam in the slice direction.

[0025] 具体的には、接着層220から音響レンズ210に超音波ビームが入射する際、それぞれの音速が c l >c m1 , when the ultrasonic beam is refracted in the converging direction by the first curved surface 310. Also, when the ultrasonic beam is incident from the acoustic lens 210 to the tip cover 110, when the respective sound velocities are c l >c m2 , the ultrasonic beam is refracted in the converging direction by the second curved surface 320. Note that since the sound velocity of the tip cover 110 is substantially the same as the sound velocity of the soft tissue (body surface) of the living body, almost no refraction of the ultrasonic beam occurs when the ultrasonic beam is incident from the tip cover 110 to the body surface.

[0026] From the above, the acoustic lens 210 can converge the ultrasonic beam with both the first curved surface 310 and the second curved surface 320. Therefore, since the acoustic lens 210 can perform two convergences to satisfy the desired focal length, the radius of curvature of each of the first curved surface 310 and the second curved surface 320 can be made larger than the radius of curvature in the case of using a plano-concave lens. Note that the focal length of the first embodiment is the distance based on the contact surface between the tip cover 110 covering the acoustic lens 210 and the body surface, and is, for example, 45 mm or less.

[0027] As described above, the ultrasonic probe according to the first embodiment includes an oscillator group having a plurality of ultrasonic oscillators, and an acoustic lens provided on the transmission / reception side of the oscillator group and having a first curved surface and a second curved surface corresponding at least to the acoustic effective aperture of the oscillator group. The speed of sound in the acoustic lens is faster than the speed of sound in the first medium in contact with the first curved surface, and faster than the speed of sound in the second medium in contact with the second curved surface, or the speed of sound in the soft tissue in contact with the second curved surface. The first curved surface is a concave surface facing the transmission / reception side, the second curved surface is a concave surface facing the first curved surface, and the radius of curvature of the first curved surface is different from the radius of curvature of the second curved surface.

[0028] Further, the ultrasonic probe according to the first embodiment further includes a tip cover formed of the second medium and covering at least the second curved surface of the acoustic lens.

[0029] Therefore, since the ultrasonic probe according to the first embodiment includes an acoustic lens composed of a bi-concave lens, the radius of curvature per lens can be increased, so that a decrease in radiation efficiency due to the incident angle of the ultrasonic beam can be prevented. In addition, since the ultrasonic probe according to the first embodiment can improve the radiation efficiency of the ultrasonic beam from the acoustic lens to the living body, the influence of artifacts on the ultrasonic image due to multiple reflections of the ultrasonic beam in the acoustic lens can be reduced. Therefore, the ultrasonic probe according to the first embodiment can improve the image quality of the ultrasonic image.

[0030] (Second Embodiment) The ultrasonic probe according to the first embodiment has a configuration in which the acoustic lens is covered with the tip cover. On the other hand, the ultrasonic probe according to the second embodiment has a configuration in which the acoustic lens also serves as the tip cover.

[0031] FIG. 5 is a diagram illustrating the appearance of an ultrasonic probe 500 according to the second embodiment. The ultrasonic probe 500 corresponds to, for example, a high-frequency linear probe. The ultrasonic probe 100 performs an ultrasonic scan on a scan region in a living body according to control from an ultrasonic diagnostic apparatus.

[0032] The appearance of the ultrasonic probe 500 is composed of an acoustic lens 510 as a tip cover and a case 520. The acoustic lens 510 is provided at the tip of the ultrasonic probe 500. Hereinafter, the specific configuration of the ultrasonic probe 500 will be described with reference to FIG. 6.

[0033] FIG. 6 is a sectional view taken along line VI-VI of FIG. 5. Further, FIG. 6 shows a part of the cross section of the ultrasonic probe 500 in the slice direction. As shown in FIG. 6, the ultrasonic probe 500 includes an acoustic lens 510 and a case 520, and further includes an adhesive layer 620, an acoustic matching layer 630, and a vibrator group 640. Note that the configuration after the backing material provided in the vibrator group 640 is not shown.

[0034] The acoustic lens 510 is formed of a material mainly composed of, for example, polymethylpentene. The acoustic lens 510 has two curved surfaces such that the thickness at the central portion in the slice direction is thinner than the thickness at the peripheral portion. The two curved surfaces are concave surfaces respectively. The acoustic lens 510 includes a region forming both concave lenses. The two curved surfaces are formed on the incident surface and the radiation surface of the acoustic lens 510 respectively. The radiation surface of the acoustic lens 510 constitutes the tip of the ultrasonic probe 500. The incident surface of the acoustic lens 510 is joined to the acoustic matching layer 630 via the adhesive layer 620. In the example of FIG. 6, the acoustic lens 510 is joined to the end of the case 520.

[0035] Since the case 520, the adhesive layer 620, the acoustic matching layer 630, and the vibrator group 640 have the same configurations as the case 120, the adhesive layer 220, the acoustic matching layer 230, and the vibrator group 240 respectively, the description thereof will be omitted.

[0036] FIG. 7 is an explanatory diagram regarding the acoustic lens 510 of FIG. 6. The acoustic lens 510 has an acoustic effective aperture A efIt has a first region 511 corresponding thereto and a second region 512 other than that. The first region 511 has a first curved surface 710 formed on the incident surface of the acoustic lens 510 and a second curved surface 720 formed on the radiation surface of the acoustic lens 510. The first curved surface 710 and the second curved surface 720 may have the same curvature (may have the same radius of curvature), or may have different curvatures (may have different radii of curvature).

[0037] In other words, the acoustic lens 510 is provided on the transmission / reception side of the oscillator group 640, and has at least the acoustic effective aperture A of the oscillator group 640 ef corresponding first curved surface 710 and second curved surface 720. Further, the first curved surface 710 is a concave surface facing the transmission / reception side, and the second curved surface 720 is a concave surface facing the first curved surface 710.

[0038] The relationship between the sound velocities of the acoustic lens 510 and the adhesive layer 620 is the same as the relationship between the sound velocities of the acoustic lens 210 and the adhesive layer 220. That is, for the acoustic lens 510 and the adhesive layer 620, when their respective sound velocities are c l and c m1 respectively, for example, they are composed of materials satisfying the relationship of c l > c m1 . Further, for the acoustic lens 510, when the sound velocity of the soft tissue of the living body is c t respectively, for example, it is composed of materials satisfying the relationship of c l > c t . According to these configurations, due to the double concave lens of the acoustic lens 510, the acoustic lens 510 can converge the ultrasonic beam in the slice direction.

[0039] Specifically, when an ultrasonic beam is incident from the adhesive layer 620 on the acoustic lens 510, when their respective sound velocities are in the relationship of c l > c m1 , the ultrasonic beam is refracted in the converging direction by the first curved surface 710. Also, when an ultrasonic beam is incident from the acoustic lens 510 on the soft tissue (body surface) of the living body, when their respective sound velocities are in the relationship of c l > c tWhen it is in such a relationship, the ultrasonic beam is refracted in the converging direction by the second curved surface 720.

[0040] From the above, the acoustic lens 510 can converge the ultrasonic beam on both the first curved surface 710 and the second curved surface 720. Therefore, since the acoustic lens 510 can perform two convergences to satisfy the desired focal length, the radius of curvature of each of the first curved surface 710 and the second curved surface 720 can be made larger than the radius of curvature in the case of using a plano-concave lens. Note that the focal length of the second embodiment is the distance based on the contact surface between the acoustic lens 510 and the body surface, and is, for example, 45 mm or less.

[0041] As described above, the ultrasonic probe according to the second embodiment includes an oscillator group having a plurality of ultrasonic oscillators, and an acoustic lens provided on the transmission / reception side of the oscillator group and having at least a first curved surface and a second curved surface corresponding to the acoustic effective aperture of the oscillator group. The speed of sound of the acoustic lens is faster than the speed of sound of the first medium in contact with the first curved surface, faster than the speed of sound of the second medium in contact with the second curved surface, or faster than the speed of sound of the soft tissue in contact with the second curved surface. The first curved surface is a concave surface facing the transmission / reception side, the second curved surface is a concave surface facing the first curved surface, and the radius of curvature of the first curved surface is different from the radius of curvature of the second curved surface.

[0042] Therefore, the ultrasonic probe according to the second embodiment can obtain the same effects as the first embodiment.

[0043] (Third Embodiment) In the first embodiment and the second embodiment, the acoustic lens composed of a double concave lens has been described. On the other hand, in the third embodiment, the method of determining the radius of curvature of each lens of the double concave lens will be described. Further, in the third embodiment, the case where the radius of curvature of the concave lens formed on the radiation surface of the acoustic lens is smaller than the radius of curvature of the concave lens formed on the incident surface of the acoustic lens will be described.

[0044] In the third embodiment, a description will be given focusing on the region corresponding to the acoustic effective aperture in the acoustic lens (effective lens region). Hereinafter, for convenience of explanation, an acoustic lens having only the effective lens region will be described. Further, the content of the third embodiment is applicable to both the acoustic lens in the first embodiment and the acoustic lens in the second embodiment.

[0045] FIG. 8 is an explanatory diagram of an acoustic lens 800 in the third embodiment. The acoustic lens 800 corresponds to an acoustic effective aperture A ef . The acoustic lens 800 has a first curved surface 810 corresponding to the incident surface and a second curved surface 820 corresponding to the radiation surface.

[0046] In the example of FIG. 8, the sagitta L ef with respect to the acoustic effective aperture A corresponding to the chord length when the first curved surface 810 is an arc c11 is lower than the sagitta L ef with respect to the acoustic effective aperture A corresponding to the chord length when the second curved surface 820 is an arc. That is, the curvature of the first curved surface 810 is smaller than the curvature of the second curved surface. In other words, the radius of curvature of the first curved surface 810 is larger than the radius of curvature of the second curved surface. c12

[0047] FIG. 9 is a graph 900 illustrating the relationship between the radius of curvature r 1 [mm] of the first curved surface and the radius of curvature r 2 [mm] of the second curved surface of the acoustic lens in the third embodiment. The horizontal axis of the graph 900 represents the radius of curvature r 2 of the second curved surface, and the vertical axis of the graph 900 represents the radius of curvature r 1 of the first curved surface. The graph 900 represents a combination of the radius of curvature r 1 and the radius of curvature r 2 when the focal length is constant (for example, 45 mm). The graph 900 shows that as the radius of curvature r 2 increases, the radius of curvature r 1 decreases. Also, in the graph 900, when the radius of curvature is 30 mm, the radius of curvature r 1 and the radius of curvature r 2 ​are the same. The radius of curvature r of the first curved surface 1 and the radius of curvature r of the second curved surface 2 are related by, for example, the following equation (1).

[0048]

Equation

[0049] In Equation (1), A ef is the acoustically effective aperture, f is the focal length, c m1 is the speed of sound in the medium (e.g., the adhesive layer) on the first curved surface side, c l is the speed of sound in the acoustic lens, c m2 is the speed of sound in the medium (e.g., the tip cover or the body surface) on the second curved surface side.

[0050] Graph 900 is calculated for the above Equation (1) with each parameter set as f = 45 mm, c m1 = 1000 m / s, c l =, 2000 m / s, and c m2 = 1500 m / s. Note that the speed of sound of the material mainly composed of polymethylpentene constituting the acoustic lens is 2000 m / s or more.

[0051] Figure 10 is a graph 1000 illustrating the relationship between the sound pressure transmittance T [%] of the acoustic lens in the third embodiment and the radius of curvature r 2 [mm] of the second curved surface. The horizontal axis of Graph 1000 indicates the radius of curvature r 2 of the second curved surface, and the vertical axis of Graph 1000 indicates the sound pressure transmittance T. The sound pressure transmittance T is the ratio of the sound pressure of the ultrasonic beam emitted from the acoustic lens to the sound pressure of the ultrasonic beam incident on the acoustic lens. In this embodiment, the sound pressure transmittance T is shown as a percentage. Note that in Graph 1000, the change in the sound pressure transmittance T with respect to the change in the radius of curvature r 2 of the second curved surface is shown, but it is assumed that the radius of curvature r 1 of the first curved surface also changes according to the radius of curvature r 2 of the second curved surface. Specifically, the radius of curvature r 1is based on the graph 900 in FIG. 9 and changes according to the radius of curvature r of the second curved surface 2 accordingly.

[0052] To calculate the sound pressure transmittance T, it is necessary to calculate the transmittance at an interface with different acoustic impedances (for example, the interface between the adhesive layer and the acoustic lens, or the interface between the acoustic lens and the tip cover (or the body surface)). The sound pressure transmittance t at this interface is expressed by, for example, the following formula (2).

[0053]

Equation

[0054] In Equation (2), Z 1 is the acoustic impedance of the medium on the incident side of the ultrasonic beam, θ i is the incident angle of the ultrasonic beam, Z 2 is the acoustic impedance of the medium on the radiation side of the ultrasonic beam, and θ t is the transmission angle of the ultrasonic beam.

[0055] The sound pressure transmittance T of the graph 1000 is calculated using the above formula (2) etc., with the acoustic impedance of the adhesive layer being 1.8 MRayl, the acoustic impedance of the acoustic lens being 1.6 MRayl, and the acoustic impedance of the tip cover being 1.725 MRayl. Note that since the sound pressure transmittance T of the graph 1000 focuses on the change in the radius of curvature, the absorption coefficient (attenuation rate) of each medium is not considered.

[0056] Next, the shape of the acoustic lens at each point on the graph 1000 will be described with reference to FIG. 11. The graph 1000 shows points 1010, 1020, 1030, and 1040 with different radii of curvature r 2 .

[0057] FIG. 11 is an explanatory diagram illustrating the shape of the acoustic lens at each point of the graph 1000 in FIG. 10. In FIG. 11, an acoustic lens 800A, an acoustic lens 800B, an acoustic lens 800C, and an acoustic lens 800D are shown. These acoustic lenses respectively correspond to the above-described points.

[0058] The acoustic lens 800A has a first curved surface 810A and a second curved surface 820A. The radius of curvature of the second curved surface 820A corresponds to the point 1010 of the graph 1000. At the point 1010, the radius of curvature r 2 is 7.5 mm. That is, the radius of curvature (r 2 ) of the second curved surface 820A is 7.5 mm. At this time, the radius of curvature (r 1 ) of the first curved surface 810A is substantially infinite compared to the graph 900. When the radius of curvature is infinite, since the curved surface can be regarded as a plane, the first curved surface 810A can be regarded as a plane. Therefore, the acoustic lens 800A can be regarded as a plano-concave lens. The sound pressure transmittance T (T th ) of the acoustic lens 800A is 88.2%.

[0059] The acoustic lens 800B has a first curved surface 810B and a second curved surface 820B. The radius of curvature of the second curved surface 820B corresponds to the point 1020 of the graph 1000. At the point 1020, the radius of curvature r 2 is 15 mm. That is, the radius of curvature (r 2 ) of the second curved surface 820B is 15 mm. At this time, the radius of curvature (r 1 ) of the first curved surface 810B is 45 mm compared to the graph 900. The sound pressure transmittance T (T max ) of the acoustic lens 800B is 90.2%.

[0060] The acoustic lens 800C has a first curved surface 810C and a second curved surface 820C. The radius of curvature of the second curved surface 820C corresponds to the point 1030 of the graph 1000. At the point 1030, the radius of curvature r 2 is 30 mm. That is, the radius of curvature (r 2) is 30 mm. At this time, the radius of curvature (r 1 ) is 30 mm from graph 900. The sound pressure transmittance T of the acoustic lens 800C is 89.8%.

[0061] The acoustic lens 800D has a first curved surface 810D and a second curved surface 820D. The radius of curvature of the second curved surface 820D corresponds to point 1040 on graph 1000. At point 1040, the radius of curvature r 2 is 45 mm. That is, the radius of curvature (r 2 ) of the second curved surface 820D is 45 mm. At this time, the radius of curvature (r 1 ) of the first curved surface 810D is 27 mm from graph 900. The sound pressure transmittance T of the acoustic lens 800D is 89.5%.

[0062] From the above, it can be seen that for the acoustic lens in the third embodiment, when the focal length is constant, regardless of the combination of the radii of curvature of the two curved surfaces that form a biconcave lens, the sound pressure transmittance is higher than that of a plano-concave lens. Also, for the acoustic lens in the third embodiment, there is a combination of the radii of curvature of the two curved surfaces at which the sound pressure transmittance is maximized in the range where the radius of curvature of the first curved surface is larger than the radius of curvature of the second curved surface (i.e., the range where r 1 > r 2 ).

[0063] As described above, the ultrasonic probe according to the third embodiment has the same configuration as the ultrasonic probe according to the first embodiment or the ultrasonic probe according to the second embodiment. Also, for the acoustic lens provided in the ultrasonic probe according to the third embodiment, the radius of curvature of the first curved surface may be the same as or different from the radius of curvature of the second curved surface.

[0064] In addition, for the acoustic lens included in the ultrasonic probe according to the third embodiment, the radius of curvature of the first curved surface may be larger than the radius of curvature of the second curved surface. Further, the acoustic impedance of the acoustic lens included in the ultrasonic probe according to the third embodiment is smaller than the acoustic impedance of the first medium in contact with the first curved surface and smaller than the acoustic impedance of the second medium in contact with the second curved surface, and the acoustic impedance of the first medium may be larger than the acoustic impedance of the second medium.

[0065] Therefore, the ultrasonic probe according to the third embodiment can obtain the same effects as those of the first embodiment and the second embodiment.

[0066] (Fourth Embodiment) In the third embodiment, the case where the radius of curvature of the concave lens formed on the radiation surface of the acoustic lens is smaller than the radius of curvature of the concave lens formed on the incident surface of the acoustic lens has been described. On the other hand, in the fourth embodiment, the case where the radius of curvature of the concave lens formed on the radiation surface of the acoustic lens is larger than the radius of curvature of the concave lens formed on the incident surface of the acoustic lens will be described.

[0067] In the fourth embodiment, similar to the third embodiment, the description will be made focusing on the effective lens region in the acoustic lens. Hereinafter, for the sake of convenience of description, only the acoustic lens having the effective lens region will be described. Further, the content of the fourth embodiment is applicable to both the acoustic lens in the first embodiment and the acoustic lens in the second embodiment.

[0068] FIG. 12 is an explanatory diagram of an acoustic lens 1200 according to the fourth embodiment. The acoustic lens 1200 corresponds to an acoustic effective aperture A ef The acoustic lens 1200 has a first curved surface 1210 corresponding to the incident surface and a second curved surface 1220 corresponding to the radiation surface.

[0069] In the example of FIG. 12, the sagitta L ef with respect to the acoustic effective aperture A corresponding to the chord length when the first curved surface 1210 is an arc c21is the acoustic effective aperture A corresponding to the chord length when the second curved surface 1220 is an arc ef with respect to the sagitta L c22 is higher. That is, the curvature of the first curved surface 1210 is greater than the curvature of the second curved surface. In other words, the radius of curvature of the first curved surface 1210 is smaller than the radius of curvature of the second curved surface 1220.

[0070] FIG. 13 is a graph 1300 illustrating the relationship between the radius of curvature r 1 [mm] of the first curved surface and the radius of curvature r 2 [mm] of the second curved surface of the acoustic lens in the fourth embodiment. The horizontal axis of the graph 1300 represents the radius of curvature r 2 of the second curved surface, and the vertical axis of the graph 1300 represents the radius of curvature r 1 of the first curved surface. The graph 1300 represents the combination of the radius of curvature r 1 and the radius of curvature r 2 when the focal length is constant (for example, 45 mm). The graph 1300 shows that as the radius of curvature r 2 increases, the radius of curvature r 1 decreases. Also, in the graph 1300, when the radius of curvature is 20 mm, the radius of curvature r 1 and the radius of curvature r 2 coincide. The relationship between the radius of curvature r 1 of the first curved surface and the radius of curvature r 2 of the second curved surface is represented by, for example, the aforementioned formula (1).

[0071] The graph 1300 is calculated for the aforementioned formula (1) with each parameter set as f = 30 mm, c m1 = 1500 m / s, c l =, 2000 m / s, and c m2 = 1000 m / s. Note that the speed of sound of the material mainly composed of polymethylpentene constituting the acoustic lens is 2000 m / s or more.

[0072] FIG. 14 shows the sound pressure transmittance T [%] of the acoustic lens in the fourth embodiment and the radius of curvature r 2Graph 1400 which illustrates the relationship with [mm]. The horizontal axis of Graph 1400 represents the radius of curvature r of the second curved surface 2 is shown, and the vertical axis of Graph 1400 represents the sound pressure transmittance T. Note that in Graph 1400, the change in the sound pressure transmittance T with respect to the change in the radius of curvature r 2 of the second curved surface is shown, but it is assumed that the radius of curvature r 1 of the first curved surface also changes according to the radius of curvature r 2 of the second curved surface. Specifically, the radius of curvature r 1 of the first curved surface changes according to the radius of curvature r 2 of the second curved surface based on the graph 1300 in FIG. 13.

[0073] The calculation of the sound pressure transmittance T is the same as in the third embodiment. The sound pressure transmittance T of Graph 1400 is calculated using the aforementioned formula (2) etc., with the acoustic impedance of the adhesive layer being 1.725 MRayl, the acoustic impedance of the acoustic lens being 1.6 MRayl, and the acoustic impedance of the tip cover being 1.6 MRayl. Note that since the sound pressure transmittance T of Graph 1400 focuses on the change in the radius of curvature, the absorption coefficient (attenuation rate) of each medium is not considered.

[0074] Next, the point 1410 where the sound pressure transmittance T is maximum in Graph 1400 will be explained using the acoustic lens 1200.

[0075] The radius of curvature of the second curved surface 1220 of the acoustic lens 1200 corresponds to the point 1410 of Graph 1400. At the point 1410, the radius of curvature r 2 is 34 mm. That is, the radius of curvature (r 2 ) that the second curved surface 1220 has is 34 mm. At this time, the radius of curvature (r 1 ) that the first curved surface 1210 has is 9 mm from Graph 1300. The sound pressure transmittance T of the acoustic lens 1200 is 93.8%.

[0076] From the above, when the focal length is constant, the acoustic lens 1200 has a range where the radius of curvature of the first curved surface is smaller than the radius of curvature of the second curved surface (that is, r 1<r 2 In the range where it becomes (), there is a combination of the radii of curvature of two surfaces where the sound pressure transmittance is maximized.

[0077] As described above, the ultrasonic probe according to the fourth embodiment has the same configuration as the ultrasonic probe according to the first embodiment or the ultrasonic probe according to the second embodiment.

[0078] Also, for the acoustic lens included in the ultrasonic probe according to the fourth embodiment, the radius of curvature of the first surface may be smaller than the radius of curvature of the second surface. Further, the acoustic impedance of the acoustic lens included in the ultrasonic probe according to the fourth embodiment is smaller than the acoustic impedance of the first medium in contact with the first surface, smaller than the acoustic impedance of the second medium in contact with the second surface, and the acoustic impedance of the first medium may be smaller than the acoustic impedance of the second medium.

[0079] Therefore, the ultrasonic probe according to the fourth embodiment can obtain the same effects as the first embodiment and the second embodiment.

[0080] According to at least one of the embodiments described above, the image quality of the ultrasonic image can be improved.

[0081] Although several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations of the embodiments can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0082] 100, 500 Ultrasonic probe 110 Tip cover 120, 520 Case 210, 510, 800, 800A, 800B, 800C, 800D, 1200 Acoustic lens 211, 511 First region 212, 512 Second region 220, 620 Adhesive layer 230, 630 Acoustic matching layer 240, 640 Transducer group 310, 710, 810, 810A, 810B, 810C, 810D, 1210 First curved surface 320, 720, 820, 820A, 820B, 820C, 820D, 1220 Second curved surface 900, 1000, 1300, 1400 Graph 1010, 1020, 1030, 1040, 1410 Point

Claims

1. A group of transducers having a plurality of ultrasonic transducers, An acoustic lens provided on the transmission / reception side of the transducer group and having a first curved surface and a second curved surface corresponding at least to the acoustic effective aperture of the transducer group Comprising, The speed of sound of the acoustic lens is, Faster than the speed of sound of the first medium in contact with the first curved surface, Faster than the speed of sound of the second medium in contact with the second curved surface, or the speed of sound of the soft tissue in contact with the second curved surface, The first curved surface is a concave surface facing the transmission / reception side, The second curved surface is a concave surface facing the first curved surface, The radius of curvature of the first curved surface is different from the radius of curvature of the second curved surface, An ultrasonic probe.

2. The radius of curvature of the first curved surface is larger than the radius of curvature of the second curved surface, The ultrasonic probe according to Claim 1.

3. The acoustic impedance of the acoustic lens is, Smaller than the acoustic impedance of the first medium, Smaller than the acoustic impedance of the second medium, The acoustic impedance of the first medium is larger than the acoustic impedance of the second medium, The ultrasonic probe according to Claim 2.

4. The radius of curvature of the first curved surface is smaller than the radius of curvature of the second curved surface, The ultrasonic probe according to Claim 1.

5. The acoustic impedance of the acoustic lens is, Smaller than the acoustic impedance of the first medium, Smaller than the acoustic impedance of the second medium, The acoustic impedance of the first medium is smaller than the acoustic impedance of the second medium, The ultrasonic probe according to Claim 4.

6. The acoustic lens converges the ultrasonic beam generated by the transducer group in the slice direction, The ultrasonic probe according to any one of Claims 1 to 5.

7. The focal length of the ultrasonic beam converged by the acoustic lens is the distance based on the contact surface between the acoustic lens and the body surface, The ultrasonic probe according to Claim 6.

8. The focal length is 45 mm or less, The ultrasonic probe according to Claim 7.

9. The acoustic lens is formed of a material having a speed of sound of 2000 m / s or more, The ultrasonic probe according to any one of Claims 1 to 5.

10. The acoustic lens is formed of a material mainly composed of polymethylpentene, The ultrasonic probe according to Claim 9.

11. A cover that at least covers the second curved surface of the acoustic lens and is formed of a second medium that contacts the second curved surface further comprising The ultrasonic probe according to claim 6

12. The focal length of the ultrasonic beam converged by the acoustic lens is a distance based on the contact surface between the cover and the body surface The ultrasonic probe according to claim 11

13. The focal length is 45 mm or less The ultrasonic probe according to claim 12

14. The acoustic lens is formed of a material having a sound speed of 2000 m / s or more The ultrasonic probe according to claim 11

15. The acoustic lens is formed of a material mainly composed of polymethylpentene The ultrasonic probe according to claim 14

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