Acoustic lens for ultrasonic probe, ultrasonic probe, ultrasonic probe, and ultrasonic diagnostic apparatus

Abstract

This acoustic lens (7) for an ultrasonic transducer is to be disposed at a front end of an ultrasonic transducer (1), has a concave front surface (C1), and is formed of a base material (B) in which a plurality of fine particles (G) are dispersed. The degree of dispersion of the fine particles (G) becomes higher from the central part toward both ends in the elevation direction, thereby causing acoustic velocity to decrease from the central part toward both ends in the elevation direction.

Description

Technical Field

[0001] The present invention relates to an acoustic lens for an ultrasonic probe, an ultrasonic probe having the acoustic lens for an ultrasonic probe, an ultrasonic probe having the ultrasonic probe, and an ultrasonic diagnostic apparatus having the ultrasonic probe.

Background Art

[0002] Conventionally, an ultrasonic diagnostic apparatus is known for obtaining an image of the inside of a subject. An ultrasonic diagnostic apparatus generally includes an ultrasonic probe provided with a vibrator array in which a plurality of piezoelectric vibrators are arranged. In a state where this ultrasonic probe is in contact with the body surface of the subject, an ultrasonic beam is transmitted from the vibrator array into the subject, and an ultrasonic echo from the subject is received by the vibrator array to obtain an electrical signal corresponding to the ultrasonic echo. Further, the ultrasonic diagnostic apparatus electrically processes the obtained electrical signal to generate an ultrasonic image of the relevant part of the subject.

[0003] In recent years, in order to draw a high-definition ultrasonic image of tissues such as muscle structures and nerve bundles at a depth of about 5 mm to 20 mm from the body surface of the subject and perform more detailed observation, for example, there has been an increasing demand for transmitting ultrasonic waves having a high frequency of about 12 MHz to 15 MHz to the subject. As a method of forming an ultrasonic beam having a narrow width in the elevation direction in such a shallow region, for example, as disclosed in Patent Document 1, it is known to use an acoustic lens having a plurality of radii of curvature in the elevation direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the acoustic lens of Patent Document 1 has a plurality of radii of curvature in the elevation direction, when the acoustic lens comes into contact with the subject and deforms, the focal length of the acoustic lens is likely to change, and there has been a case where the ultrasonic beam cannot converge at a desired depth. Further, since the acoustic lens of Patent Document 1 has a plurality of radii of curvature, it is locally thickened abruptly, and ultrasonic waves propagating through the acoustic lens are likely to be locally attenuated, and there may be a portion where the acoustic lens is difficult to come into contact with the subject. Therefore, there has been a problem that when an ultrasonic image is taken using the acoustic lens of Patent Document 1, the image quality of the ultrasonic image may deteriorate.

[0006] The present invention has been made to solve such conventional problems, and an acoustic lens for an ultrasonic probe capable of obtaining an ultrasonic image having high image quality regardless of depth, an ultrasonic probe having the acoustic lens for an ultrasonic probe, an ultrasonic probe having the ultrasonic probe, and an ultrasonic diagnostic apparatus having the ultrasonic probe.

Means for Solving the Problems

[0007] In order to achieve the above object, a first acoustic lens for an ultrasonic probe according to the present invention is an acoustic lens disposed at the front end portion of the ultrasonic probe, having a concave front surface, formed from a base material in which a plurality of fine particles are dispersed, and characterized in that the sound velocity decreases from the central portion in the elevation direction toward both end portions due to the higher degree of dispersion of the fine particles from the central portion in the elevation direction toward both end portions.

[0008] The first acoustic lens for an ultrasonic probe can have a high sound velocity region lens portion disposed at the central portion in the elevation direction and a low sound velocity region lens portion disposed at both end portions in the elevation direction.

[0009] The acoustic lens for the second ultrasonic probe according to the present invention is an acoustic lens disposed at the front end of the ultrasonic probe, having a convex front surface, formed from a base material in which a plurality of fine particles are dispersed, and characterized in that the degree of dispersion of the fine particles decreases from the central portion in the elevation direction toward both end portions, so that the speed of sound increases from the central portion in the elevation direction toward both end portions.

[0010] The acoustic lens for the second ultrasonic probe can have a low sound speed region lens portion disposed at the central portion in the elevation direction and a high sound speed region lens portion disposed at both end portions in the elevation direction.

[0011] The front surfaces of the acoustic lens for the first ultrasonic probe and the acoustic lens for the second ultrasonic probe preferably have the same radius of curvature from the central portion in the elevation direction to both end portions. Also, in the acoustic lens for the first ultrasonic probe and the acoustic lens for the second ultrasonic probe, it is preferable that the number of fine particles per unit volume is the same from the central portion in the elevation direction to both end portions.

[0012] Also, the fine particles preferably have a diameter of 0.01 μm or more and 100.00 μm or less, and more preferably have a diameter of 1.00 μm or more and 10.00 μm or less. Also, the fine particles preferably consist of iron, tungsten, alumina, zirconia, or silica.

[0013] The ultrasonic probe according to the present invention includes a backing material, a plurality of piezoelectric vibrators arranged and formed on the surface of the backing material, an acoustic matching layer disposed on the plurality of piezoelectric vibrators, and the first acoustic lens for the ultrasonic probe or the second acoustic lens for the ultrasonic probe of the present invention disposed on the acoustic matching layer.

[0014] The acoustic matching layer can include a first matching layer in which the transmission and reception frequency of ultrasonic waves decreases from the central portion in the elevation direction toward both end portions. The plurality of piezoelectric vibrators can each have a thickness that increases from the central portion in the elevation direction toward both end portions, so that the ultrasonic transmission and reception frequency can decrease from the central portion in the elevation direction toward both end portions.

[0015] The ultrasonic probe of the present invention is characterized by having the ultrasonic transducer of the present invention. The ultrasonic diagnostic apparatus of the present invention is characterized by having the ultrasonic probe of the present invention.

Advantages of the Invention

[0016] According to the present invention, the acoustic lens for an ultrasonic transducer has a concave front surface and is formed from a base material in which a plurality of fine particles are dispersed. The degree of dispersion of the fine particles is higher from the central portion in the elevation direction toward both end portions, so that the speed of sound decreases from the central portion in the elevation direction toward both end portions. Or, it has a convex front surface and is formed from a base material in which a plurality of fine particles are dispersed. The degree of dispersion of the fine particles is lower from the central portion in the elevation direction toward both end portions, so that the speed of sound increases from the central portion in the elevation direction toward both end portions. Therefore, an ultrasonic image with high image quality can be obtained regardless of the depth.

Brief Description of the Drawings

[0017]

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Figure 10

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The description of the constituent elements described below is based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In this specification, "identical" and "the same" shall include the error range generally acceptable in the technical field.

[0019] Embodiment 1 As shown in FIG. 1, an ultrasonic probe 1 according to Embodiment 1 of the present invention includes a backing material 2, and a plurality of piezoelectric vibrators 3 arranged at an array pitch P in the azimuth direction on the surface of the backing material 2. Acoustic matching layers 4 are respectively arranged on the surfaces of the plurality of piezoelectric vibrators 3, and an acoustic lens 7 for an ultrasonic probe according to Embodiment 1 of the present invention is arranged on the surfaces of the plurality of acoustic matching layers 4, that is, at the front end of the ultrasonic probe 1. Further, the plurality of acoustic matching layers 4 each have a first matching layer 5 arranged on the surface of the piezoelectric vibrator 3 and a second matching layer 6 arranged on the surface of the first matching layer 5. In addition, a separation portion 8 filled with an epoxy resin or the like is formed between adjacent piezoelectric vibrators 3 and between adjacent acoustic matching layers 4.

[0020] Note that extraction electrodes (not shown) are respectively connected to the plurality of piezoelectric vibrators 3, and a flexible printed circuit board (not shown) connected to the plurality of extraction electrodes is disposed on the side surface of the backing material 2, but is omitted for the sake of explanation. Further, in the following, for the sake of explanation, the azimuth direction in which the plurality of piezoelectric vibrators 3 and the plurality of acoustic matching layers 4 are arranged is defined as the X direction, the stacking direction of the backing material 2, the piezoelectric vibrator 3, the acoustic matching layer 4, and the acoustic lens 7 for the ultrasonic probe is defined as the Z direction, and the elevation direction orthogonal to the X direction and the Z direction is defined as the Y direction.

[0021] The piezoelectric vibrator 3 generates ultrasonic waves according to a drive signal supplied from a pulsar or the like (not shown) connected to the ultrasonic probe 1, receives an ultrasonic echo, and outputs a signal based on the ultrasonic echo. The piezoelectric vibrator 3 is configured, for example, by forming electrodes at both ends of a piezoelectric body made of a piezoelectric ceramic typified by PZT (Lead Zirconate Titanate), a polymer piezoelectric element typified by PVDF (Poly Vinylidene Di Fluoride), a piezoelectric single crystal typified by PMN-PT (Lead Magnesium Niobate-Lead Titanate solid solution), or the like.

[0022] The backing material 2 supports the plurality of piezoelectric vibrators 3 and absorbs ultrasonic waves emitted from the plurality of piezoelectric vibrators 3 and propagated rearward. The backing material 2 is formed of, for example, a rubber material such as ferrite rubber.

[0023] The acoustic matching layer 4 is for matching the acoustic impedance between the subject contacted by the ultrasonic probe 1 and the piezoelectric vibrator 3, making it easier for ultrasonic waves to be incident into the subject. Generally, since the acoustic impedance of the piezoelectric vibrator 3 is often higher than that of the acoustic lens 7 for the ultrasonic probe and the acoustic impedance within the subject, the acoustic matching layer 4 can be formed of a material having an acoustic impedance lower than that of the piezoelectric vibrator 3 and higher than that of the acoustic lens and the acoustic impedance within the subject. Also, the first matching layer 5 included in the acoustic matching layer 4 has a thickness of about one-fourth of the wavelength of the ultrasonic wave propagating through the first matching layer 5 in order to resonate the ultrasonic wave emitted from the piezoelectric vibrator 3 and propagating through the first matching layer 5 and enhance the intensity of the ultrasonic wave. Similarly, it is desirable for the second matching layer 6 to have a thickness of about one-fourth of the wavelength of the ultrasonic wave propagating through the second matching layer 6.

[0024] The first matching layer 5 of the acoustic matching layer 4 is formed on the surface of the piezoelectric vibrator 3 and has an acoustic impedance lower than that of the piezoelectric vibrator 3. As the material of the first matching layer 5, a resin material such as epoxy resin or urethane resin can be used. The second matching layer 6 is formed on the surface of the first matching layer 5 and has an acoustic impedance lower than that of the first matching layer 5 and higher than that of the acoustic lens 7 for the ultrasonic probe. As the material of the second matching layer 6, similar to the first matching layer 5, a resin material such as epoxy resin or urethane resin can be used.

[0025] The acoustic lens 7 for an ultrasonic probe according to Embodiment 1 of the present invention narrows an ultrasonic beam by using refraction and improves the resolution in the Y direction. As shown in FIG. 1, the acoustic lens 7 for an ultrasonic probe has a concave front surface C1 having a constant radius of curvature, and the acoustic lens 7 for an ultrasonic probe is arranged such that the front surface C1 faces the side opposite to the acoustic matching layer 4. Further, since the acoustic lens 7 for an ultrasonic probe has a concave front surface C1, it is formed of a material having a refractive index smaller than that of the subject in order to converge the ultrasonic beam in the subject. Here, as shown in FIG. 2, the acoustic lens 7 for an ultrasonic probe is formed from a base material B in which a plurality of fine particles G are dispersed.

[0026] The base material B is formed from, for example, resin materials such as epoxy resin, acrylic resin, and polymethylpentene resin, and rubber materials such as silicone rubber. Further, the fine particles G are formed from metal or ceramics, and for example, iron, tungsten, alumina, or zirconia is used as the material. The fine particles G preferably have a diameter of 0.01 μm or more and 100.00 μm or less, and more preferably have a diameter of 1.00 μm or more and 10.00 μm or less in order to reduce the attenuation of ultrasonic waves in the acoustic lens 7 for an ultrasonic probe.

[0027] Further, in the acoustic lens 7 for the ultrasonic probe, the degree of dispersion of the fine particles G increases from the central portion in the Y direction toward both ends, and the number of fine particles G per unit volume in the acoustic lens 7 for the ultrasonic probe is the same from the central portion in the Y direction to both ends. Here, the degree of dispersion of the fine particles G is an index representing the variation in the distance between adjacent fine particles G in the base material B. The higher the degree of dispersion, the more uniformly distributed the arrangement positions of the fine particles G in the base material B, and the lower the degree of dispersion, the more locally close the fine particles G are to each other and the more non-uniformly distributed the arrangement positions of the fine particles G in the base material B. In the example shown in FIG. 2, in the central portion in the Y direction, there are many fine particles G that are in contact with or close to each other, that is, a lens portion A1 for the high sound velocity region with a low degree of dispersion of the fine particles G is formed. At both ends in the Y direction, there are many fine particles G that are separated from each other and the distribution of the arrangement positions of the fine particles G in the base material B is more uniform, that is, a lens portion A2 for the low sound velocity region with a high degree of dispersion of the fine particles G is formed. Here, since the number of fine particles G per unit volume is the same from the central portion to both ends in the Y direction of the acoustic lens 7 for the ultrasonic probe, the acoustic impedance of the lens portion A1 for the high sound velocity region and the acoustic impedance of the lens portion A2 for the low sound velocity region are substantially the same as each other.

[0028] By the way, when two materials having different acoustic impedances are in contact with each other and a sound wave passes through the interface between them, the phase of the sound wave is affected, and a phenomenon is known in which the group velocity in the traveling direction of the sound wave becomes low at the interface between the two materials. As shown in FIG. 2, in the lens portion A1 for the high sound velocity region, since there are many fine particles G that are in contact with or close to each other, the total amount of the effective interfaces between the base material B and the fine particles G on the propagation path of the ultrasonic wave traveling in the Z direction in the acoustic lens 7 for the ultrasonic probe is relatively small. In the lens portion A2 for the low sound velocity region, since a plurality of fine particles G are more uniformly distributed, the total amount of the effective interfaces between the base material B and the fine particles G on the propagation path of the ultrasonic wave traveling in the Z direction in the acoustic lens 7 for the ultrasonic probe is relatively large.

[0029] Therefore, for example, the group velocity in the Z direction of the ultrasonic wave propagating through the acoustic lens 7 for the ultrasonic probe becomes relatively high in the lens portion A1 for the high sound velocity region and relatively low in the lens portion A2 for the low sound velocity region. As a result, the effective refractive index of the lens portion A1 for the high sound velocity region becomes relatively small, and the effective refractive index of the lens portion A2 for the low sound velocity region becomes relatively large. Further, the acoustic lens 7 for the ultrasonic probe has a concave front surface C1, and since the refractive index of the acoustic lens 7 for the ultrasonic probe is smaller than the refractive index of the subject, when the ultrasonic wave travels from the acoustic lens 7 for the ultrasonic probe through the front surface C1 to the subject, the ultrasonic wave transmitted through the lens portion A1 for the high sound velocity region is refracted more greatly toward the central portion side in the Y direction of the acoustic lens 7 for the ultrasonic probe than the ultrasonic wave transmitted through the lens portion A2 for the low sound velocity region. Therefore, the focal length of the lens portion A1 for the high sound velocity region becomes shorter than the focal length of the lens portion A2 for the low sound velocity region. Here, the focal length represents the distance from the central portion in the Y direction of the front surface C1 of the acoustic lens 7 for the ultrasonic probe to the position where the width of the ultrasonic beam becomes the narrowest in the Y direction.

[0030] Here, generally, the focal length F of the acoustic lens is known to be determined by the relationship R = F×|(V2 / V1) - 1|, where R is the radius of curvature of the front surface of the acoustic lens, V1 is the group velocity of the ultrasonic wave propagating through the acoustic lens, and V2 is the group velocity of the ultrasonic wave propagating through the subject. By using this relationship, it is possible to specifically confirm that the focal length F of the lens portion A1 for the high sound velocity region is shorter than the focal length F of the lens portion A2 for the low sound velocity region.

[0031] The acoustic lens 7 for the ultrasonic probe has a concave front surface C1 with a constant radius of curvature R. Since the refractive index of the acoustic lens 7 for the ultrasonic probe is smaller than the refractive index of the subject, the group velocity V1 of the ultrasonic wave propagating in the acoustic lens 7 for the ultrasonic probe is higher than the group velocity V2 of the ultrasonic wave propagating in the subject. Therefore, the velocity ratio (V2 / V1) of the group velocity V2 of the ultrasonic wave propagating in the subject to the group velocity V1 of the ultrasonic wave propagating in the acoustic lens 7 for the ultrasonic probe is greater than 0.0 and smaller than 1.0. Furthermore, since the group velocity V1 of the ultrasonic wave propagating in the lens portion A1 for the high sound velocity region is higher than the group velocity V1 of the ultrasonic wave propagating in the lens portion A2 for the low sound velocity region, the velocity ratio (V2 / V1) corresponding to the lens portion A1 for the high sound velocity region is smaller than the velocity ratio (V2 / V1) corresponding to the lens portion A2 for the low sound velocity region.

[0032] Here, as a specific example, when the velocity ratio (V2 / V1) corresponding to the lens portion A1 for the high sound velocity region is 0.8 and the velocity ratio (V2 / V1) corresponding to the lens portion A2 for the low sound velocity region is 0.9, for the lens portion A1 for the high sound velocity region, a relationship of R = 0.2×F is obtained, and for the lens portion A2 for the low sound velocity region, a relationship of R = 0.1×F is obtained. Therefore, the focal length F of the lens portion A1 for the high sound velocity region is 5×R, and the focal length F of the lens portion A2 for the low sound velocity region is 10×R. Thus, it can be confirmed that the focal length F of the lens portion A1 for the high sound velocity region is shorter than the focal length F of the lens portion A2 for the low sound velocity region.

[0033] As described above, according to the acoustic lens 7 for the ultrasonic probe according to the first embodiment of the present invention, the ultrasonic beam formed by the ultrasonic wave transmitted through the lens portion A1 for the high sound velocity region can converge to the shallow part of the subject, and the ultrasonic beam formed by the ultrasonic wave transmitted through the lens portion A2 for the low sound velocity region can converge to the deep part of the subject. Therefore, even though the front surface C1 of the acoustic lens 7 for the ultrasonic probe has a constant radius of curvature R in the Y direction, an ultrasonic image with high image quality can be obtained regardless of the depth. Further, for example, when a piezoelectric vibrator that emits high-frequency ultrasonic waves is used as the plurality of piezoelectric vibrators 3, in particular, an ultrasonic image that depicts the shallow part in the subject with high definition can be obtained.

[0034] Conventionally, as a method of forming an ultrasonic beam that converges in the shallow part and has a narrow width in the Y direction, it is known to use an acoustic lens having a front surface formed with a plurality of curvature radii R in the Y direction. However, in this method, since the front surface of the acoustic lens has a plurality of curvature radii R in the Y direction, when the acoustic lens comes into contact with the subject and deforms, the focal length F of the acoustic lens is likely to change, and the ultrasonic beam may not converge at the desired depth. Further, since the front surface of the acoustic lens has a plurality of curvature radii R, the acoustic lens becomes locally thick suddenly, the ultrasonic waves propagating through the acoustic lens are likely to be attenuated, and there may be a portion where the acoustic lens is difficult to contact the subject. These problems are factors that cause the image quality of the ultrasonic image to deteriorate.

[0035] According to the acoustic lens 7 for an ultrasonic probe according to Embodiment 1 of the present invention, since the front surface C1 having a constant curvature radius R is formed on the acoustic lens 7 for an ultrasonic probe, even if the acoustic lens 7 for an ultrasonic probe comes into contact with the subject and deforms, the influence of the deformation is small, and the ultrasonic beam can be stably converged according to the desired focal length F. Further, since the front surface C1 having a constant curvature radius R is formed on the acoustic lens 7 for an ultrasonic probe, the acoustic lens 7 for an ultrasonic probe does not become locally thick suddenly, and while reducing the attenuation of the ultrasonic waves propagating through the acoustic lens 7 for an ultrasonic probe, an ultrasonic image having high image quality can be obtained regardless of the depth. Furthermore, since the acoustic lens 7 for an ultrasonic probe does not become locally thick suddenly, the entire front surface C1 of the acoustic lens 7 for an ultrasonic probe in the Y direction can be easily brought into contact with the subject.

[0036] In addition, since the front surface C1 of the acoustic lens 7 for the ultrasonic probe is concave and the relatively thin lens portion A1 for the high sound velocity region is disposed at the center of the acoustic lens 7 for the ultrasonic probe, even when high-frequency ultrasonic waves are emitted from the plurality of piezoelectric vibrators 3, the attenuation of the high-frequency ultrasonic waves propagating through the lens portion A1 for the high sound velocity region can be further reduced, and an ultrasonic image having high image quality can be obtained.

[0037] Next, a method for manufacturing the acoustic lens 7 for the ultrasonic probe according to Embodiment 1 of the present invention will be described. First, surface treatment is performed on the fine particles G formed of iron, tungsten, alumina, zirconia, or the like.

[0038] Examples of the surface treatment for the fine particles G include oil agent treatment with hydrocarbon oil, ester oil, lanolin, etc., silicone treatment with dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane, etc., fluorine compound treatment with perfluoroalkyl group-containing ester, perfluoroalkylsilane, perfluoropolyether, polymer having a perfluoroalkyl group, etc., silane coupling agent treatment with 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, etc., titanium coupling agent treatment with isopropyltriisostearoyl titanate, isopropyltris(dioctylpyrophosphate) titanate, etc., metal soap treatment, amino acid treatment with acylglutamic acid, etc., lecithin treatment with hydrogenated egg yolk lecithin, etc., collagen treatment, polyethylene treatment, moisture retention treatment, inorganic compound treatment, mechanochemical treatment, phosphoric acid compound treatment with phosphoric acid, phosphorous acid, phosphate, phosphite, etc. Among these, from the viewpoint of controlling the degree of dispersion of the fine particles G, it is preferable to perform phosphoric acid compound treatment.

[0039] At this time, fine particles G for the high supersonic speed region with a large degree of surface treatment and fine particles G for the low supersonic speed region with a small degree of surface treatment can be obtained. For example, even when using the same surface treatment agent, the more the amount of the surface treatment agent is increased during surface treatment, the higher the degree of dispersion of the fine particles G with respect to the base material B can be obtained, and the less the amount of the surface treatment agent is, the lower the degree of dispersion of the fine particles G with respect to the base material B can be obtained. Further, for example, the more the number of surface treatment times is increased, the higher the degree of dispersion of the fine particles G with respect to the base material B can be obtained, and the less the number of surface treatment times is, the lower the degree of dispersion of the fine particles G with respect to the base material B can be obtained.

[0040] Here, in order to reduce the attenuation of the ultrasonic wave emitted from the piezoelectric vibrator 3 and propagating through the acoustic lens 7 for the ultrasonic probe, it preferably has a diameter of 0.01 μm or more and 100.00 μm or less, and more preferably has a diameter of 1.00 μm or more and 10.00 μm or less. However, the diameter of the fine particles G can be measured as follows. First, the fine particles G that have been sufficiently surface-treated are added to methanol so as to be 0.5% by mass, and ultrasonic waves are applied for 10 minutes to disperse the fine particles G in methanol. In this way, the particle size distribution of the fine particles G dispersed in methanol is measured by a laser diffraction / scattering type particle size distribution measuring device (manufactured by Horiba, Ltd., product name: LA950V2), and the diameter of the fine particles G can be obtained by calculating the volume-based median diameter based on the measured particle size distribution. The volume-based median diameter at this time is the particle diameter corresponding to 50% cumulative when the particle size distribution is represented as a cumulative distribution.

[0041] Next, as the base material B, a resin material that cures by heating such as an epoxy resin, an acrylic resin, a polymethylpentene resin, or a rubber material that cures by heating such as silicone rubber is prepared. Fine particles G for the high supersonic region are added to the resin material or rubber material before curing, and the resin material or rubber material and the fine particles G for the high supersonic region are mixed by a so-called planetary mixer or the like to obtain a mixture for the high supersonic region. Also, fine particles G for the low supersonic region are added to the resin material or rubber material before curing, and the resin material or rubber material and the fine particles G for the low supersonic region are mixed by a planetary mixer or the like to obtain a mixture for the low supersonic region.

[0042] The thus obtained mixture for the high supersonic region before curing and the mixture for the low supersonic region before curing are each put into a molding die and heated to cure, thereby obtaining a lens member for the high supersonic region and a lens member for the low supersonic region. The lens member for the high supersonic region and the lens member for the low supersonic region thus obtained each have a front surface curved so as to have the same radius of curvature R. The lens member for the high supersonic region is a member corresponding to the lens portion A1 for the high supersonic region of the acoustic lens 7 for the ultrasonic probe, and the lens member for the low supersonic region is a member corresponding to the lens portion A2 for the low supersonic region.

[0043] Finally, by using an adhesive such as an epoxy adhesive to bond the lens members for the low supersonic region to both ends of the lens member for the high supersonic region, an acoustic lens 7 for an ultrasonic probe as shown in FIGS. 1 and 2 is obtained.

[0044] By the way, as an acoustic lens for forming an ultrasonic beam having a narrow width in the Y direction, an acoustic lens having a front surface formed with a plurality of radii of curvature R in the Y direction is known. Generally, ultrasonic probes that emit ultrasonic waves at high frequencies such as 12 MHz to 15 MHz often have a small size. It has been difficult to manufacture an acoustic lens having a front surface formed with a plurality of radii of curvature R in the Y direction to match such a small-sized ultrasonic probe.

[0045] Since the acoustic lens 7 for an ultrasonic probe according to Embodiment 1 of the present invention has a front surface C1 with a constant radius of curvature R, for example, even when the ultrasonic probe 1 has a small size corresponding to the oscillation of high-frequency ultrasonic waves, it can be easily manufactured according to the size of the ultrasonic probe 1.

[0046] Next, an ultrasonic diagnostic apparatus having the ultrasonic probe 1 according to Embodiment 1 of the present invention will be described. As shown in FIG. 3, in the ultrasonic diagnostic apparatus 11, a transmission / reception circuit 12, an image generation unit 13, a display control unit 14, and a monitor 15 are sequentially connected to the ultrasonic probe 1. Further, an apparatus control unit 16 is connected to the transmission / reception circuit 12, the image generation unit 13, and the display control unit 14. Further, an input device 17 is connected to the apparatus control unit 16. Further, a memory (not shown) is connected to the apparatus control unit 16. The ultrasonic diagnostic apparatus 11 includes an ultrasonic probe 21 including the ultrasonic probe 1 and the transmission / reception circuit 12. Further, a processor 22 for the ultrasonic diagnostic apparatus 11 is configured by the image generation unit 13, the display control unit 14, and the apparatus control unit 16.

[0047] The transmission / reception circuit 12 transmits ultrasonic waves from the ultrasonic probe 1 and generates a beam signal based on the reception signal acquired by the ultrasonic probe 1 under the control of the apparatus control unit 16. As shown in FIG. 4, the transmission / reception circuit 12 has a pulsar 23 connected to the ultrasonic probe 1, an amplification unit 24, an AD (Analog Digital) conversion unit 25, and a beam former 26 that are sequentially connected in series from the ultrasonic probe 1.

[0048] The pulsar 23 includes, for example, a plurality of pulse generators, and supplies drive signals to the plurality of piezoelectric vibrators 3 of the ultrasonic probe 1 while adjusting the delay amount so that ultrasonic waves transmitted from the plurality of piezoelectric vibrators 3 form an ultrasonic beam based on a transmission delay pattern selected according to a control signal from the device control unit 16. Thus, when a pulsed or continuous-wave voltage is applied to the electrodes of the piezoelectric vibrator 3, the piezoelectric vibrator 3 expands and contracts, generating pulsed or continuous-wave ultrasonic waves from each of the piezoelectric vibrators 3, and an ultrasonic beam is formed from the combined waves of these ultrasonic waves.

[0049] The transmitted ultrasonic beam is reflected, for example, by tissues in the subject and propagates toward the ultrasonic probe 1 of the ultrasonic probe 21. Each piezoelectric vibrator 3 of the ultrasonic probe 1 expands and contracts by receiving the ultrasonic echo propagating toward the ultrasonic probe 1 in this way, generates a received signal which is an electrical signal, and outputs these received signals to the amplifier unit 24.

[0050] The amplifier unit 24 amplifies the signals input from each piezoelectric vibrator 3 of the ultrasonic probe 1 and transmits the amplified signals to the AD conversion unit 25. The AD conversion unit 25 converts the signals transmitted from the amplifier unit 24 into digital received data and transmits these received data to the beamformer 26. The beamformer 26 performs so-called reception focusing processing by giving respective delays to and adding the received data converted by the AD conversion unit 25 according to the speed of sound or the distribution of the speed of sound set based on a reception delay pattern selected according to a control signal from the device control unit 16. By this reception focusing processing, the received data converted by the AD conversion unit 25 are coherently added and a line signal with the focus of the ultrasonic echo narrowed down is obtained.

[0051] As shown in FIG. 5, the image generation unit 13 has a configuration in which a signal processing unit 27, a DSC (Digital Scan Converter) 28, and an image processing unit 29 are sequentially connected in series. The signal processing unit 27 performs attenuation correction based on distance on the acoustic beam signal generated by the beamformer 26 of the transmission / reception circuit 12 according to the depth of the reflection position of the ultrasonic wave, and then performs envelope detection processing to generate a B-mode image signal, which is tomographic image information regarding the tissue in the subject.

[0052] The DSC 28 converts (raster-converts) the B-mode image signal generated by the signal processing unit 27 into an image signal conforming to the scanning method of a normal television signal. The image processing unit 29 performs various necessary image processes such as gradation processing on the B-mode image signal input from the DSC 28, and then outputs the B-mode image signal to the display control unit 14. In the present invention, the B-mode image signal subjected to image processing by the image processing unit 29 is simply referred to as an ultrasonic image.

[0053] The display control unit 14 performs predetermined processing on the ultrasonic image generated by the image generation unit 13 under the control of the device control unit 16, and displays the ultrasonic image on the monitor 15. The monitor 15 displays the ultrasonic image generated by the image generation unit 13 under the control of the display control unit 14, and includes, for example, a display device such as an LCD (Liquid Crystal Display) or an organic EL display (Organic Electroluminescence Display).

[0054] The device control unit 16 controls each part of the ultrasonic diagnostic apparatus 11 based on a control program stored in advance and the like. The input device 17 is for the user to perform input operations, and can be configured to include a keyboard, a mouse, a trackball, a touch pad, a touch panel, and the like.

[0055] Although not shown, the memory connected to the device control unit 16 stores the control program of the ultrasonic diagnostic device 11 and the like. As the memory, a recording medium such as a flash memory, HDD (Hard Disc Drive), SSD (Solid State Drive), FD (Flexible Disc), MO disc (Magneto-Optical disc), MT (Magnetic Tape), RAM (Random Access Memory), CD (Compact Disc), DVD (Digital Versatile Disc), SD card (Secure Digital card), USB memory (Universal Serial Bus memory), or a server or the like can be used.

[0056] Note that the processor 22 having the image generation unit 13, the display control unit 14, and the device control unit 16 is composed of a CPU (Central Processing Unit) and a control program for causing the CPU to perform various processes. However, it may be configured using an FPGA (Field Programmable Gate Array), DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), GPU (Graphics Processing Unit), or other IC (Integrated Circuit), or may be configured by combining them.

[0057] In addition, the image generation unit 13, the display control unit 14, and the device control unit 16 of the processor 22 can also be configured to be integrated partially or entirely into one CPU or the like.

[0058] Since the ultrasonic diagnostic apparatus 11 in the first embodiment of the present invention includes the ultrasonic probe 1 having the acoustic lens 7 for the ultrasonic probe according to the first embodiment of the present invention, an ultrasonic image having high image quality can be obtained regardless of the depth. In particular, when ultrasonic waves of a relatively high frequency are emitted from the ultrasonic probe 1, an ultrasonic image in which a shallow region is depicted with high definition can be obtained.

[0059] Note that the degree of dispersion of the fine particles G with respect to the base material B in the acoustic lens 7 for the ultrasonic probe is adjusted by subjecting the fine particles G to surface treatment, but the method for adjusting the degree of dispersion of the fine particles G is not limited to surface treatment. For example, by changing the method of mechanically mixing the fine particles G in the base material B, the degree of dispersion of the fine particles G in the base material B can be changed. For example, by mixing the fine particles G in the base material B using a so-called propeller type mixer, the degree of dispersion of the fine particles G can be made lower than in the case of mixing the fine particles G using a planetary mixer. Therefore, when producing a mixture for a high sound velocity region, the fine particles G can be mixed in the base material B using a propeller type mixer, and when producing a mixture for a low sound velocity region, the fine particles G can be mixed in the base material B using a planetary mixer. Also, for example, the degree of dispersion of the fine particles G can be changed by changing the time for mixing the fine particles G in the base material B.

[0060] Also, for example, the degree of dispersion of the fine particles G can be changed by changing the time required for curing the base material B. For example, if the temperature for heating the mixture of the base material B and the fine particles G is lowered and the time required for curing the base material B is lengthened, the degree of dispersion of the fine particles G can be lowered, and if the temperature for heating the mixture of the base material B and the fine particles G is raised and the time required for curing the base material B is shortened, the degree of dispersion of the fine particles G can be raised.

[0061] In addition, an example is shown in which the acoustic lens 7 for an ultrasonic probe is composed of two types of regions, i.e., a lens portion A1 for a high sound velocity region and a lens portion A2 for a low sound velocity region. However, if the degree of dispersion of the fine particles G in the base material B increases from the central portion in the Y direction toward both end portions, the acoustic lens 7 for an ultrasonic probe can also be composed of three or more types of regions having different degrees of dispersion of the fine particles G. Further, the acoustic lens 7 for an ultrasonic probe can be configured such that the degree of dispersion of the fine particles G in the base material B continuously increases from the central portion in the Y direction of the acoustic lens 7 for an ultrasonic probe toward both end portions. Thereby, an ultrasonic image having a more uniform image quality can be obtained.

[0062] In addition, although it is described that the number of fine particles G per unit volume in the lens portion A1 for a high sound velocity region is the same as the number of fine particles G per unit volume in the lens portion A2 for a low sound velocity region, it can also be finely adjusted in order to adjust the acoustic impedances of the lens portion A1 for a high sound velocity region and the lens portion A2 for a low sound velocity region.

[0063] Embodiment 2 The acoustic lens 7 for an ultrasonic probe according to Embodiment 1 of the present invention has a concave front surface C1, but it can also have a convex front surface. As shown in FIG. 6, the ultrasonic probe 1A in Embodiment 2 of the present invention includes an acoustic lens 7A for an ultrasonic probe instead of the acoustic lens 7 for an ultrasonic probe in the ultrasonic probe 1 in Embodiment 1 shown in FIGS. 1 and 2.

[0064] The acoustic lens 7A for an ultrasonic probe according to Embodiment 2 of the present invention is formed from a base material B in which a plurality of fine particles G are dispersed, in the same manner as the acoustic lens 7 for an ultrasonic probe in Embodiment 1. However, it has a convex front surface C2 having a certain radius of curvature R. In the central portion of the acoustic lens 7A for an ultrasonic probe in the Y direction, there is a lens portion A2 for a low sound velocity region where the degree of dispersion of the fine particles G is high. At both ends of the acoustic lens 7A for an ultrasonic probe in the Y direction, there are lens portions A1 for a high sound velocity region where the degree of dispersion of the fine particles G is low. Thus, in the acoustic lens 7A for an ultrasonic probe, the degree of dispersion of the fine particles G decreases from the central portion in the Y direction toward both ends. Also, the number of fine particles G per unit volume in the acoustic lens 7A for an ultrasonic probe is the same from the central portion in the Y direction to both ends. Therefore, the acoustic impedance of the lens portion A2 for a low sound velocity region and the acoustic impedance of the lens portion A1 for a high sound velocity region are substantially the same as each other. Further, the acoustic lens 7A for an ultrasonic probe is formed of a material having a refractive index larger than that of the subject in order to converge an ultrasonic beam in the subject.

[0065] Here, the group velocity V1 in the Z direction of the ultrasonic wave propagating through the acoustic lens 7A for an ultrasonic probe becomes relatively low in the lens portion A2 for a low sound velocity region arranged in the central portion in the Y direction, and becomes relatively high in the lens portion A1 for a high sound velocity region arranged at both ends in the Y direction. Therefore, the effective refractive index of the lens portion A2 for a low sound velocity region becomes relatively large, and the effective refractive index of the lens portion A1 for a high sound velocity region becomes relatively small. Further, the acoustic lens 7A for an ultrasonic probe has a convex front surface C2, and since the refractive index of the acoustic lens 7A for an ultrasonic probe is larger than the refractive index of the subject, when the ultrasonic wave travels from the acoustic lens 7A for an ultrasonic probe through the front surface C2 to the subject, the ultrasonic wave transmitted through the lens portion A2 for a low sound velocity region refracts more greatly toward the central portion side in the Y direction of the acoustic lens 7A for an ultrasonic probe than the ultrasonic wave transmitted through the lens portion A1 for a high sound velocity region. Therefore, the focal length F of the lens portion A2 for a low sound velocity region becomes shorter than the focal length F of the lens portion A1 for a high sound velocity region.

[0066] In addition, a convex front surface C2 having a constant radius of curvature R is formed on the acoustic lens 7A for an ultrasonic probe. Since the refractive index of the acoustic lens 7A for an ultrasonic probe is larger than the refractive index of the subject, the group velocity V1 of ultrasonic waves propagating in the acoustic lens 7A for an ultrasonic probe is lower than the group velocity V2 of ultrasonic waves propagating in the subject. Therefore, the velocity ratio (V2 / V1) of the group velocity V2 of ultrasonic waves propagating in the subject to the group velocity V1 of ultrasonic waves propagating in the acoustic lens 7A for an ultrasonic probe becomes larger than 1.0. Furthermore, since the group velocity V1 of ultrasonic waves propagating in the lens portion A2 for the low sound velocity region is lower than the group velocity V1 of ultrasonic waves propagating in the lens portion A1 for the high sound velocity region, the velocity ratio (V2 / V1) corresponding to the lens portion A2 for the low sound velocity region becomes larger than the velocity ratio (V2 / V1) corresponding to the lens portion A1 for the high sound velocity region.

[0067] Here, as a specific example, when the velocity ratio (V2 / V1) corresponding to the lens portion A2 for the low sound velocity region is set to 1.2 and the velocity ratio (V2 / V1) corresponding to the lens portion A1 for the high sound velocity region is set to 1.1, from the relationship of R = F × |(V2 / V1) - 1|, for the lens portion A2 for the low sound velocity region, a relationship of R = 0.2 × F is obtained, and for the lens portion A1 for the high sound velocity region, a relationship of R = 0.1 × F is obtained. Therefore, the focal length F of the lens portion A2 for the low sound velocity region becomes 5 × R, and the focal length F of the lens portion A1 for the high sound velocity region becomes 10 × R. Thus, it can be confirmed that the focal length F of the lens portion A2 for the low sound velocity region is shorter than the focal length F of the lens portion A1 for the high sound velocity region.

[0068] As described above, according to the acoustic lens 7A for an ultrasonic probe according to the second embodiment of the present invention, the ultrasonic beam formed by the ultrasonic waves transmitted through the lens portion A2 for the low sound velocity region can converge on the shallow part of the subject, and the ultrasonic beam formed by the ultrasonic waves transmitted through the lens portion A1 for the high sound velocity region can converge on the deep part of the subject. Therefore, even though the front surface C2 of the acoustic lens 7A for an ultrasonic probe has a constant radius of curvature R in the Y direction, an ultrasonic image having high image quality can be obtained regardless of the depth. Further, for example, when a piezoelectric vibrator that emits high-frequency ultrasonic waves is used as the plurality of piezoelectric vibrators 3, an ultrasonic image that depicts the shallow part in the subject with high definition can be obtained in particular.

[0069] In addition, since the front surface C2 having a constant radius of curvature R is formed on the acoustic lens 7A for the ultrasonic probe, even if the acoustic lens 7A for the ultrasonic probe comes into contact with the subject and is deformed, the influence of the deformation is small, and the ultrasonic beam can be stably converged according to the desired focal length F. Further, since the front surface C2 having a constant radius of curvature R is formed on the acoustic lens 7A for the ultrasonic probe, the acoustic lens 7A for the ultrasonic probe does not thicken locally and rapidly, and while reducing the attenuation of the ultrasonic wave propagating through the acoustic lens 7A for the ultrasonic probe, an ultrasonic image having high image quality can be obtained regardless of the depth. Furthermore, since the acoustic lens 7A for the ultrasonic probe does not thicken locally and rapidly, the entire front surface C2 of the acoustic lens 7A for the ultrasonic probe in the Y direction can be easily brought into contact with the subject.

[0070] Although an example in which the acoustic lens 7A for the ultrasonic probe is composed of two types of regions, i.e., the lens portion A2 for the low sound velocity region and the lens portion A1 for the high sound velocity region, is shown, if the degree of dispersion of the fine particles G in the base material B becomes lower from the central portion in the Y direction toward both end portions, the acoustic lens 7A for the ultrasonic probe can also be composed of three or more types of regions having different degrees of dispersion of the fine particles G. Further, the acoustic lens 7A for the ultrasonic probe can be configured such that the degree of dispersion of the fine particles G in the base material B continuously decreases from the central portion in the Y direction of the acoustic lens 7A for the ultrasonic probe toward both end portions. Thereby, an ultrasonic image having more uniform image quality can be obtained.

[0071] Embodiment 3 The acoustic lens 7 for the ultrasonic probe according to Embodiment 1 is formed from a base material B in which a plurality of fine particles G are dispersed. Further, the acoustic matching layer 4 may also include a layer formed from a base material B in which a plurality of fine particles G are dispersed. As shown in Fig. 7, the ultrasonic probe 1B in Embodiment 3 includes an acoustic matching layer 4B instead of the acoustic matching layer 4 in the ultrasonic probe 1 in Embodiment 1 shown in Fig. 2. Further, the acoustic matching layer 4B has a first matching layer 5B instead of the first matching layer 5 in the acoustic matching layer 4 in Embodiment 1. As shown in Fig. 7, the first matching layer 5B is formed from a base material B in which a plurality of fine particles G are dispersed.

[0072] In the first matching layer 5B, the degree of dispersion of the fine particles G increases from the central portion in the Y direction toward both ends, and the number of fine particles G per unit volume in the first matching layer 5 is the same from the central portion in the Y direction to both ends. In the example shown in Fig. 7, at the central portion in the Y direction, a matching portion H1 for a high-frequency region with a low degree of dispersion of the fine particles G is formed, and at both ends in the Y direction, a matching portion H2 for a low-frequency region with a high degree of dispersion of the fine particles G is formed. Here, the matching portion H1 for the high-frequency region is formed at a position in the Y direction corresponding to the lens portion A1 for the high-speed region of the acoustic lens 7 for the ultrasonic probe, and the matching portion H2 for the low-frequency region is formed at a position in the Y direction corresponding to the lens portion A2 for the low-speed region of the acoustic lens 7 for the ultrasonic probe. Further, since the number of fine particles G per unit volume is the same from the central portion to both ends in the Y direction of the first matching layer 5B, the acoustic impedance of the matching portion H1 for the high-frequency region and the acoustic impedance of the matching portion H2 for the low-frequency region are substantially the same as each other.

[0073] Here, assuming that the group velocity of sound is V, the frequency is Q, and the wavelength is W, the relationship V = Q × W is known. Due to the resonance condition caused by the thickness of the first matching layer 5B, ultrasonic waves having a certain wavelength W are strengthened. Therefore, when the wavelength W is constant, the group velocity V of the ultrasonic waves propagating through the matching portion H1 for the high-frequency region of the first matching layer 5B is relatively fast, so its frequency Q is high, and the group velocity V of the ultrasonic waves propagating through the matching portion H2 for the low-frequency region is relatively slow, so its frequency is low.

[0074] In addition, since the matching section H1 for the high-frequency region is arranged at the central portion of the acoustic matching layer 4B in the Y direction, it has a relatively wide aperture width compared to the overall width of the acoustic matching layer 4 in the Y direction. On the other hand, since the matching section H2 for the low-frequency region is arranged at both end portions of the acoustic matching layer 4B, it has a relatively wide aperture width. Therefore, the width in the Y direction of the ultrasonic beam converged by the ultrasonic probe acoustic lens 7 from the ultrasonic wave transmitted through the matching section H1 for the high-frequency region becomes relatively narrow, and the width in the Y direction of the ultrasonic beam converged by the ultrasonic probe acoustic lens 7 from the ultrasonic wave transmitted through the matching section H2 for the low-frequency region becomes relatively wide.

[0075] Therefore, the ultrasonic beam formed from the ultrasonic wave transmitted through the matching section H1 for the high-frequency region of the first matching layer 5B and the lens section A1 for the high-speed sound region of the ultrasonic probe acoustic lens 7 has a relatively high frequency Q and a relatively narrow width in the Y direction, and further converges according to a short focal length F. Also, the ultrasonic beam formed from the ultrasonic wave transmitted through the matching section H2 for the low-frequency region of the first matching layer 5B and the lens section A2 for the low-speed sound region of the ultrasonic probe acoustic lens 7 has a relatively low frequency Q and converges according to a long focal length F. Thereby, according to the ultrasonic probe 1B in the third embodiment of the present invention, an ultrasonic image having higher image quality can be obtained regardless of the depth.

[0076] Note that although the aspect of the third embodiment is shown to be applicable to the ultrasonic probe 1 in the first embodiment, it can be similarly applied to the ultrasonic probe 1A in the second embodiment. For example, as shown in FIG. 8, the ultrasonic probe 1C in the modified example of the third embodiment is the ultrasonic probe 1A in the second embodiment shown in FIG. 6, in which the first matching layer 5B is provided instead of the first matching layer 5.

[0077] In this case, the ultrasonic beam formed from the ultrasonic waves that have passed through the matching section H1 for the high-frequency region of the first matching layer 5B and the lens section A2 for the low-velocity region of the acoustic lens 7A for the ultrasonic probe has a relatively high frequency Q and a relatively narrow width in the Y direction, and further converges according to a short focal length F. Also, the ultrasonic beam formed from the ultrasonic waves that have passed through the matching section H2 for the low-frequency region of the first matching layer 5B and the lens section A1 for the high-velocity region of the acoustic lens 7A for the ultrasonic probe has a relatively low frequency Q and converges according to a long focal length F. Thus, according to the ultrasonic probe 1C in the modification of Embodiment 3 of the present invention, in the same manner as the ultrasonic probe 1B in Embodiment 3, an ultrasonic image having higher image quality can be obtained regardless of the depth.

[0078] Also, by making the length of the matching section H1 for the high-frequency region in the Y direction longer than the length of the matching section H2 for the low-frequency region in the Y direction, the ratio of the ultrasonic waves transmitted and received through the matching section H1 for the high-frequency region can be increased. Although ultrasonic waves having a higher frequency are more likely to be attenuated, by making the matching section H1 for the high-frequency region longer in the Y direction, even if relatively high-frequency ultrasonic waves are attenuated in the subject, the amount of ultrasonic echoes received through the matching section H1 for the high-frequency region can be sufficiently ensured, and it is possible to prevent the brightness of the ultrasonic image in a relatively shallow part from decreasing. Thereby, an ultrasonic image having more uniform image quality can be obtained.

[0079] In this case, for example, it is preferable that the length of the matching section H1 for the high-frequency region in the Y direction is longer than 1 / 2 of the total length of the first matching layer 5B in the Y direction. Specifically, for example, the length of the matching section H1 for the high-frequency region in the Y direction may be 2 times or 3 times the length of the matching section H2 for the low-frequency region in the Y direction.

[0080] In addition, an example is shown in which the first matching layer 5B is composed of two types of regions, i.e., a matching section H1 for high-frequency regions and a matching section H2 for low-frequency regions. However, if the degree of dispersion of the fine particles G in the base material B increases from the central portion in the Y direction toward both end portions so that the transmission and reception frequencies of the ultrasonic waves decrease from the central portion in the Y direction toward both end portions, the first matching layer 5B can also be composed of three or more types of regions with different degrees of dispersion of the fine particles G. Further, the first matching layer 5B can be configured such that the degree of dispersion of the fine particles G in the base material B continuously increases from the central portion in the Y direction toward both end portions. Therefore, an ultrasonic image having a more uniform image quality can be obtained.

[0081] In addition, for example, the first matching layer 5B can also be configured with a multilayer structure composed of a plurality of layers having different acoustic impedances from each other. For example, a layer in which a plurality of fine particles G are dispersed in the base material B having a high acoustic impedance can be arranged so as to approach the piezoelectric vibrator 3 side in the Z direction, and a layer in which a plurality of fine particles G are dispersed in the base material B having a low acoustic impedance can be arranged so as to approach the second matching layer 6 in the Z direction. Further, since the acoustic impedance can be increased as the number of fine particles G per unit volume dispersed in the base material B increases, for example, a layer in which the number of fine particles G per unit volume dispersed in the base material B is large can be arranged so as to approach the piezoelectric vibrator 3 side in the Z direction, and a layer in which the number of fine particles G per unit volume dispersed in the base material B is small can be arranged so as to approach the second matching layer 6 in the Z direction.

[0082] Thus, by having the first matching layer 5B have a multilayer structure composed of a plurality of layers having different acoustic impedances from each other, the acoustic impedance between the subject contacted by the ultrasonic probe 1B and the piezoelectric vibrator 3 can be accurately matched, and ultrasonic waves can be more easily incident into the subject.

[0083] Also, although not shown, an ultrasonic diagnostic apparatus 11 having the ultrasonic probe 1B or the ultrasonic probe 1C in the third embodiment is provided with a so-called low-pass filter and a high-pass filter, and using the low-pass filter and the high-pass filter, for example, filter processing according to depth can be performed on reception data digitized by the AD conversion unit 25. More specifically, for example, in the shallow part above the focal depth of the ultrasonic beam, signals of low-frequency components below a determined lower limit value are cut, and an ultrasonic image is generated only by signals of high-frequency components. In the deep part deeper than the focal depth of the ultrasonic beam, signals of high-frequency components above a determined upper limit value are cut, and an ultrasonic image can be generated only by signals of low-frequency components.

[0084] Also, for example, in the deep part deeper than the focal depth of the ultrasonic beam, the high-frequency component signals can be gradually cut so that the ratio of the low-frequency component signals gradually increases as the depth increases. In this way, by performing filter processing according to depth on the reception data, an ultrasonic image having higher image quality can be obtained regardless of the depth.

[0085] Embodiment 4 In the ultrasonic probe 1 in the first embodiment, the plurality of piezoelectric vibrators 3 have a constant thickness in the Y direction, but the thickness may vary depending on the position in the Y direction. As shown in FIG. 9, the ultrasonic probe 1D in the fourth embodiment of the present invention is the ultrasonic probe 1 in the first embodiment shown in FIGS. 1 and 2, in which a backing material 2D is provided instead of the backing material 2, and a plurality of piezoelectric vibrators 3D are provided instead of the plurality of piezoelectric vibrators 3.

[0086] The backing material 2D has a constant thickness at the central part in the Y direction. Also, at both ends in the Y direction, the thickness of the backing material 2D gradually becomes thinner toward both ends in the Y direction.

[0087] Each of the plurality of piezoelectric vibrators 3D includes a piezoelectric section K1 for a high-frequency region having a constant thickness T1 at the central portion in the Y direction, and at both end portions in the Y direction, each piezoelectric vibrator 3D includes a piezoelectric section K2 for a low-frequency region in which the thickness of each piezoelectric vibrator 3D gradually increases from the thickness T1 to a constant thickness T2 from the central portion in the Y direction toward both end portions. The piezoelectric section K1 for the high-frequency region is disposed at a position corresponding to the lens section A1 for the high sound velocity region of the acoustic lens 7 for the ultrasonic probe in the Y direction, and the piezoelectric section K2 for the low-frequency region is disposed at a position corresponding to the lens section A2 for the low sound velocity region of the acoustic lens 7 for the ultrasonic probe in the Y direction. In the example shown in FIG. 9, each of the piezoelectric sections K2 for the low-frequency region of the plurality of piezoelectric vibrators 3D has an inclined surface portion J that is inclined at a constant inclination so as to be in contact with the backing material 2D and move away from the acoustic matching layer 4 from the central portion in the Y direction toward both end portions.

[0088] Here, as the piezoelectric vibrator 3D becomes thicker, the transmission and reception frequency of the ultrasonic wave by the piezoelectric vibrator 3D becomes lower, and as the piezoelectric vibrator 3D becomes thinner, the transmission and reception frequency of the ultrasonic wave by the piezoelectric vibrator 3D becomes higher. Therefore, the piezoelectric section K1 for the high-frequency region transmits and receives relatively high-frequency ultrasonic waves, and the piezoelectric section K2 for the low-frequency region transmits and receives relatively low-frequency ultrasonic waves.

[0089] Therefore, the relatively high-frequency ultrasonic waves emitted from the piezoelectric sections K1 for the high-frequency region of the plurality of piezoelectric vibrators 3D propagate through the lens section A1 for the high sound velocity region of the acoustic lens 7 for the ultrasonic probe, and the ultrasonic beam formed from the ultrasonic waves transmitted through the lens section A1 for the high sound velocity region has a narrow width in the Y direction and converges according to a relatively short focal length F. Also, the relatively low-frequency ultrasonic waves emitted from the piezoelectric sections K2 for the low-frequency region of the plurality of piezoelectric vibrators 3D propagate through the lens section A2 for the low sound velocity region of the acoustic lens 7 for the ultrasonic probe, and the ultrasonic beam formed from the ultrasonic waves transmitted through the lens section A2 for the low sound velocity region converges according to a relatively long focal length F.

[0090] In this way, according to the ultrasonic probe 1D in the fourth embodiment of the present invention, since the plurality of piezoelectric vibrators 3D become thicker from the central portion in the Y direction toward both ends, the transmission and reception frequencies of ultrasonic waves by the respective piezoelectric vibrators 3D become lower from the central portion in the Y direction toward both ends. Therefore, an ultrasonic beam having a narrow width in the Y direction and a relatively high frequency converges in the shallow part, and an ultrasonic beam having a relatively low frequency that is less likely to attenuate converges in the deep part. Therefore, an ultrasonic image having high image quality can be obtained regardless of the depth.

[0091] Although the aspect of the fourth embodiment is shown to be applicable to the ultrasonic probe 1 in the first embodiment, it can be similarly applied to the ultrasonic probe 1A in the second embodiment. For example, as shown in FIG. 10, the ultrasonic probe 1E in the modified example of the fourth embodiment is provided with a backing material 2D instead of the backing material 2 in the ultrasonic probe 1A shown in FIG. 6, and is provided with a plurality of piezoelectric vibrators 3D instead of the plurality of piezoelectric vibrators 3.

[0092] In this case, the relatively high-frequency ultrasonic waves emitted from the high-frequency region piezoelectric portion K1 of the plurality of piezoelectric vibrators 3D propagate through the lens portion A2 for the low sound velocity region of the acoustic lens 7A for the ultrasonic probe, and the ultrasonic beam formed from the ultrasonic waves transmitted through the lens portion A2 for the low sound velocity region has a narrow width in the Y direction and converges according to the relatively short focal length F. Further, the relatively low-frequency ultrasonic waves emitted from the low-frequency region piezoelectric portion K2 of the plurality of piezoelectric vibrators 3D propagate through the lens portion A1 for the high sound velocity region of the acoustic lens 7A for the ultrasonic probe, and the ultrasonic beam formed from the ultrasonic waves transmitted through the lens portion A1 for the high sound velocity region converges according to the relatively long focal length F.

[0093] In this way, according to the ultrasonic probe 1E in the modified example of the fourth embodiment of the present invention, similar to the ultrasonic probe 1D in the fourth embodiment, an ultrasonic image having higher image quality can be obtained regardless of the depth.

[0094] Also, FIGS. 9 and 10 show that the piezoelectric portions K2 for the low-frequency regions of the plurality of piezoelectric vibrators 3D each have an inclined surface portion J having a certain inclination and inclined so as to move away from the acoustic matching layer 4 from the central portion in the Y direction toward both end portions. However, if the plurality of piezoelectric vibrators 3D each become thicker from the central portion in the Y direction toward both end portions, it is not particularly limited to this mode. Further, for example, the inclination of the inclined surface portion J may gradually change from the central portion in the Y direction toward both end portions so that the thickness of the piezoelectric portion K2 for the low-frequency region gradually changes from the thickness T1 to the thickness T2 from the central portion in the Y direction toward both end portions. Further, for example, the piezoelectric portion K2 for the low-frequency region may have a flat surface portion (not shown) extending along the X direction and the Y direction instead of the inclined surface portion J so as to have a constant thickness T2 thicker than the thickness T1.

[0095] Also, by making the length in the Y direction of the piezoelectric portion K1 for the high-frequency region longer than the length in the Y direction of the piezoelectric portion K2 for the low-frequency region, the ratio of relatively high-frequency ultrasonic waves oscillated by the plurality of piezoelectric vibrators 3D can be increased. Although ultrasonic waves having higher frequencies are more likely to attenuate, by making the piezoelectric portion K1 for the high-frequency region longer in the Y direction, even if relatively high-frequency ultrasonic waves attenuate in the subject, the amount of ultrasonic echo received by the piezoelectric portion K1 for the high-frequency region can be sufficiently ensured, and it is possible to prevent the brightness of a relatively shallow ultrasonic image from decreasing. Thereby, an ultrasonic image having more uniform image quality can be obtained.

[0096] In this case, for example, it is preferable that the length in the Y direction of the piezoelectric portion K1 for the high-frequency region is longer than 1 / 2 of the total length in the Y direction of the piezoelectric vibrator 3D. Specifically, for example, the length in the Y direction of the piezoelectric portion K1 for the high-frequency region may be twice or three times the length in the Y direction of the piezoelectric portion K2 for the low-frequency region.

[0097] Further, although not shown, an ultrasonic diagnostic apparatus 11 having an ultrasonic probe 1D or an ultrasonic probe 1E in Embodiment 4 is provided with a so-called low-pass filter and a high-pass filter. Using the low-pass filter and the high-pass filter, for example, filter processing according to depth can be performed on reception data digitized by an AD conversion unit 25. More specifically, for example, in the shallower part shallower than the focal depth of the ultrasonic beam, signals of low-frequency components below a determined lower limit value are cut, and an ultrasonic image is generated only by signals of high-frequency components. In the deeper part deeper than the focal depth of the ultrasonic beam, signals of high-frequency components above a determined upper limit value are cut, and an ultrasonic image can be generated only by signals of low-frequency components.

[0098] Also, for example, in the deeper part deeper than the focal depth of the ultrasonic beam, the signals of high-frequency components can be gradually cut so that the ratio of the signals of low-frequency components gradually increases as the depth increases. In this way, by performing filter processing according to depth on the reception data, an ultrasonic image with higher image quality can be obtained regardless of the depth.

[0099] Also, the aspect of Embodiment 4 can be applied to Embodiment 3 in the same manner as Embodiments 1 and 2.

Explanation of Reference Numerals

[0100] 1, 1A, 1B, 1C, 1D, 1E ultrasonic probe, 2, 2D backing material, 3, 3D piezoelectric vibrator, 4, 4B acoustic matching layer, 5, 5B first matching layer, 6 second matching layer, 7, 7A acoustic lens for ultrasonic probe, 8 separation part, 11 ultrasonic diagnostic apparatus, 12 transmission / reception circuit, 13 image generation unit, 14 display control unit, 15 monitor, 16 apparatus control unit, 17 input device, 21 ultrasonic probe, 22 processor, 23 pulser, 24 amplifier unit, 25 AD conversion unit, 26 beamformer, 27 signal processing unit, 28 DSC, 29 image processing unit, A1 lens part for high sound velocity region, A2 lens part for low sound velocity region, B base material, C1, C2 front surface, G fine particle, H1 matching part for high frequency region, H2 matching part for low frequency region, K1 piezoelectric part for high frequency region, K2 piezoelectric part for low frequency region, P array pitch, T1, T2 thickness.

Claims

1. An acoustic lens disposed at the front end of an ultrasonic probe, having a concave front surface, formed from a base material in which a plurality of fine particles are dispersed, from the central portion in the elevation direction toward both end portions, the total amount of the effective interfaces between the base material and the fine particles on the propagation path of the ultrasonic wave traveling through the acoustic lens is large, and due to the high degree of dispersion of the fine particles, the speed of sound decreases from the central portion in the elevation direction toward both end portions, The front surface is an acoustic lens for an ultrasonic probe having the same radius of curvature from the central portion in the elevation direction to both end portions.

2. The acoustic lens for an ultrasonic probe according to claim 1, having a high sound speed region lens portion disposed at the central portion in the elevation direction and a low sound speed region lens portion disposed at both end portions in the elevation direction.

3. An acoustic lens disposed at the front end of an ultrasonic probe, having a convex front surface, formed from a base material in which a plurality of fine particles are dispersed, from the central portion in the elevation direction toward both end portions, the total amount of the effective interfaces between the base material and the fine particles on the propagation path of the ultrasonic wave traveling through the acoustic lens is small, and due to the low degree of dispersion of the fine particles, the speed of sound increases from the central portion in the elevation direction toward both end portions, The front surface is an acoustic lens for an ultrasonic probe having the same radius of curvature from the central portion in the elevation direction to both end portions.

4. The acoustic lens for an ultrasonic probe according to claim 3, having a low sound speed region lens portion disposed at the central portion in the elevation direction and a high sound speed region lens portion disposed at both end portions in the elevation direction.

5. The acoustic lens for an ultrasonic probe according to any one of claims 1 to 4, wherein the number of the fine particles per unit volume is the same from the central portion in the elevation direction to both end portions.

6. The acoustic lens for an ultrasonic probe according to any one of claims 1 to 5, wherein the fine particles have a diameter of 0.01 μm or more and 100.00 μm or less.

7. The acoustic lens for an ultrasonic probe according to claim 6, wherein the fine particles have a diameter of 1.00 μm or more and 10.00 μm or less.

8. The acoustic lens for an ultrasonic probe according to any one of claims 1 to 7, wherein the fine particles are made of iron, tungsten, alumina, zirconia or silica.

9. A backing material, A plurality of piezoelectric vibrators arranged and formed on the surface of the backing material; An acoustic matching layer disposed on the plurality of piezoelectric vibrators; An acoustic lens for an ultrasonic probe according to any one of claims 1 to 8 disposed on the acoustic matching layer An ultrasonic probe comprising the same.

10. The ultrasonic probe according to claim 9, wherein the acoustic matching layer includes a first matching layer in which the transmission and reception frequency of ultrasonic waves decreases from the central portion in the elevation direction toward both end portions.

11. The ultrasonic probe according to claim 9 or 10, wherein each of the plurality of piezoelectric vibrators becomes thicker from the central portion in the elevation direction toward both end portions, so that the transmission and reception frequency of ultrasonic waves decreases from the central portion in the elevation direction toward both end portions.

12. An ultrasonic probe having the ultrasonic probe according to any one of claims 9 to 11.

13. An ultrasonic diagnostic apparatus having the ultrasonic probe according to claim 12.

Images