Acoustic lenses for ultrasonic transducers, ultrasonic transducers, ultrasonic probes, and ultrasonic diagnostic equipment

Abstract

To provide an acoustic lens for an ultrasound transducer which can obtain an ultrasound image having high image quality regardless of a depth.SOLUTION: An acoustic lens (7) for an ultrasound transducer that is disposed in a front end portion of an ultrasound transducer (1) has a concave front surface (C1) and is formed from a base material (B) in which a plurality of fine particles (G) is dispersed. As a degree of dispersion of the fine particles (G) is higher from a central portion toward both end portions in an elevation direction, an acoustic velocity is lower from the central portion toward both end portions in the elevation direction, and the number of the fine particles (G) per unit volume is the same from the central portion toward both end portions in the elevation direction.SELECTED DRAWING: Figure 2

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 transducer array in which a plurality of piezoelectric transducers are arranged. In a state where this ultrasonic probe is brought into contact with the body surface of the subject, an ultrasonic beam is transmitted from the transducer array into the subject, and an ultrasonic echo from the subject is received by the transducer 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 high-definition ultrasonic images 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 observations, for example, there has been an increasing demand for transmitting ultrasonic waves with 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, because the acoustic lens described in Patent Document 1 has multiple radii of curvature in the elevation direction, when the acoustic lens deforms upon contact with the object being tested, the focal length of the acoustic lens is prone to changing, and the ultrasonic beam may not be able to focus at the desired depth. Furthermore, because the acoustic lens described in Patent Document 1 has multiple radii of curvature, it becomes locally and abruptly thicker, which makes it prone to local attenuation of ultrasonic waves propagating through the acoustic lens, and can result in areas where the acoustic lens does not easily contact the object being tested. Therefore, there was a problem that when ultrasonic images were taken using the acoustic lens described in Patent Document 1, the image quality of the ultrasonic images may deteriorate.

[0006] The present invention was made to solve the aforementioned problems of the past, and aims to provide an acoustic lens for an ultrasonic transducer that can obtain ultrasonic images with high image quality regardless of depth, an ultrasonic transducer having the acoustic lens for the ultrasonic transducer, an ultrasonic probe having the ultrasonic transducer, and an ultrasonic diagnostic apparatus having the ultrasonic probe. [Means for solving the problem]

[0007] To achieve the above objective, the first acoustic lens for an ultrasonic probe according to the present invention is 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, characterized in that the degree of dispersion of the fine particles increases from the center to both ends in the elevation direction, the speed of sound decreases from the center to both ends in the elevation direction, and the number of fine particles per unit volume is the same from the center to both ends in the elevation direction.

[0008] The first acoustic lens for the ultrasonic probe may have a lens portion for the high-sound velocity region located in the center in the elevation direction and lens portions for the low-sound velocity region located at both ends in the elevation direction.

[0009] The second acoustic lens for an ultrasonic probe according to the present invention is 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, characterized in that the degree of dispersion of the fine particles decreases from the center to both ends in the elevation direction, the sound velocity increases from the center to both ends in the elevation direction, and the number of fine particles per unit volume is the same from the center to both ends in the elevation direction.

[0010] The second acoustic lens for the ultrasonic probe may have a lens portion for the low sound velocity region located in the center in the elevation direction and lens portions for the high sound velocity region located at both ends in the elevation direction.

[0011] Preferably, the front surfaces of the first and second acoustic lenses for the ultrasonic transducer have the same radius of curvature from the center to both ends in the elevation direction.

[0012] Furthermore, 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. Furthermore, the fine particles are preferably made of iron, tungsten, alumina, zirconia, or silica.

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

[0014] The acoustic matching layer may include a first matching layer in which the ultrasonic transmission and reception frequencies decrease from the center to both ends in the elevation direction. Multiple piezoelectric transducers can be arranged so that their thickness increases from the center towards both ends in the elevation direction, thereby allowing the ultrasonic transmission and reception frequencies to decrease from the center towards both ends in the elevation direction.

[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, since 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, and the degree of dispersion of the fine particles increases from the central portion in the elevation direction toward both end portions, the speed of sound decreases from the central portion in the elevation direction toward both end portions, and the number of fine particles per unit volume is the same from the central portion to both end portions in the elevation direction, an ultrasonic image having high image quality can be obtained regardless of the depth.

Brief Description of the Drawings

[0017] [Figure 1] It is a perspective view of an ultrasonic transducer having an acoustic lens for an ultrasonic transducer according to Embodiment 1 of the present invention. [Figure 2] It is a cross-sectional view of an ultrasonic transducer having an acoustic lens for an ultrasonic transducer according to Embodiment 1 of the present invention. [Figure 3] It is a block diagram showing the configuration of an ultrasonic diagnostic apparatus having an ultrasonic transducer according to Embodiment 1 of the present invention. [Figure 4] It is a block diagram showing the internal configuration of a transmission / reception circuit according to Embodiment 1 of the present invention. [Figure 5] It is a block diagram showing the internal configuration of an image generation unit according to Embodiment 1 of the present invention. [Figure 6] It is a cross-sectional view of an ultrasonic transducer having an acoustic lens for an ultrasonic transducer according to Embodiment 2 of the present invention. [Figure 7] It is a cross-sectional view of an ultrasonic transducer according to Embodiment 3 of the present invention. [Figure 8] It is a cross-sectional view of an ultrasonic transducer in a modified example of Embodiment 3 of the present invention. [Figure 9]Cross-sectional view of the ultrasonic probe in Embodiment 4 of the present invention. [Figure 10] Cross-sectional view of the ultrasonic probe in a modified example of Embodiment 4 of the present invention.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of this invention will be described based on the accompanying drawings. The description of the constituent elements described below is made based on representative 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 ranges generally acceptable in the technical field.

[0019] Embodiment 1 As shown in FIG. 1, the ultrasonic probe 1 in 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 are arranged 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 portion of the ultrasonic probe 1. Further, each of the plurality of acoustic matching layers 4 has 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. Also, 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 multiple piezoelectric transducers 3 are each connected to lead electrodes (not shown), and flexible printed circuit boards (not shown) connected to the multiple lead electrodes are arranged on the side of the backing material 2, but these are omitted for the sake of explanation. Furthermore, for the sake of explanation below, the azimuth direction in which the multiple piezoelectric transducers 3 and multiple acoustic matching layers 4 are arranged is referred to as the X direction, the stacking direction of the backing material 2, piezoelectric transducers 3, acoustic matching layers 4, and acoustic lens 7 for the ultrasonic probe is referred to as the Z direction, and the elevation direction perpendicular to the X and Z directions is referred to as the Y direction.

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

[0022] The backing material 2 supports the multiple piezoelectric transducers 3 and absorbs the ultrasonic waves emitted from the multiple piezoelectric transducers 3 and propagated backward. The backing material 2 is made of a rubber material such as ferrite rubber.

[0023] The acoustic matching layer 4 is designed to match the acoustic impedance between the object in contact with the ultrasonic transducer 1 and the piezoelectric transducer 3, thereby facilitating the injection of ultrasound into the object. Generally, the acoustic impedance of the piezoelectric transducer 3 is often higher than that of the acoustic lens 7 for the ultrasonic transducer and the object itself. Therefore, the acoustic matching layer 4 can be formed from a material having an acoustic impedance lower than that of the piezoelectric transducer 3 and higher than that of the acoustic lens and the object itself. Furthermore, the first matching layer 5 included in the acoustic matching layer 4 is preferably thicker than one-quarter of the wavelength of the ultrasound propagating through the first matching layer 5 in order to resonate the ultrasound emitted from the piezoelectric transducer 3 and propagating through the first matching layer 5, thereby increasing the intensity of the ultrasound. Similarly, the second matching layer 6 is preferably thicker than one-quarter of the wavelength of the ultrasound 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 a lower acoustic impedance than the piezoelectric vibrator 3. A resin material such as epoxy resin or urethane resin can be used as the material for the first matching layer 5. 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 with the first matching layer 5, a resin material such as epoxy resin or urethane resin can be used as the material for the second matching layer 6.

[0025] The acoustic lens 7 for an ultrasonic probe according to Embodiment 1 of the present invention utilizes refraction to focus the ultrasonic beam and improve resolution in the Y direction. As shown in Figure 1, the acoustic lens 7 for the ultrasonic probe has a concave front surface C1 having a constant radius of curvature, and the acoustic lens 7 for the ultrasonic probe is positioned so that the front surface C1 faces away from the acoustic matching layer 4. Furthermore, the acoustic lens 7 for the ultrasonic probe is formed from a material having a smaller refractive index than the object to be examined in order to focus the ultrasonic beam into the object. Here, as shown in Figure 2, the acoustic lens 7 for the 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. The fine particles G are formed from metal or ceramics, and the materials used include, for example, iron, tungsten, alumina, or zirconia. The fine particles G preferably have a diameter of 0.01 μm to 100.00 μm, and more preferably have a diameter of 1.00 μm to 10.00 μm, in order to reduce the attenuation of ultrasonic waves in the acoustic lens 7 for the ultrasonic probe.

[0027] Furthermore, in the acoustic lens 7 for the ultrasonic probe, the dispersion of fine particles G increases from the center in the Y direction towards 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 center in the Y direction to both ends. Here, the dispersion of fine particles G is an index that represents the variation in the distance between adjacent fine particles G in the base material B. The more uniformly the arrangement positions of the fine particles G in the base material B are distributed, the higher the dispersion, and the more locally close the fine particles G are and the more unevenly the arrangement positions of the fine particles G in the base material B are distributed, the lower the dispersion. In the example shown in Figure 2, in the center in the Y direction, there are many fine particles G that are in contact with or close to each other, i.e., lens section A1 for the high-sound-velocity region is formed, i.e., the dispersion of fine particles G is low. In the ends in the Y direction, there are many fine particles G that are far apart from each other and the distribution of the arrangement positions of the fine particles G in the base material B is more uniform, i.e., lens section A2 for the low-sound-velocity region is formed, i.e., the dispersion of fine particles G is high. Here, since the number of microparticles G per unit volume is the same from the center to both ends in the Y direction of the acoustic lens 7 for the ultrasonic probe, the acoustic impedance of the lens section A1 for the high sound velocity region and the acoustic impedance of the lens section A2 for the low sound velocity region are approximately the same.

[0028] Incidentally, it is known that when two materials having different acoustic impedances are in contact with each other and sound waves pass through their interface, the phase of the sound waves is affected, resulting in a decrease in the group velocity in the direction of sound wave propagation at the interface between the two materials. As shown in Figure 2, in the high-speed lens section A1, there are many fine particles G that are in contact with or close to each other, so the total effective interface area between the base material B and the fine particles G on the propagation path of the ultrasonic waves traveling in the Z direction through the acoustic lens 7 for the ultrasonic probe is relatively small. In the low-speed lens section A2, the multiple fine particles G are more uniformly distributed, so the total effective interface area between the base material B and the fine particles G on the propagation path of the ultrasonic waves traveling in the Z direction through 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 waves propagating through the acoustic lens 7 for the ultrasonic probe is relatively high in the high-speed lens section A1 and relatively low in the low-speed lens section A2. As a result, the effective refractive index of the high-speed lens section A1 is relatively small, and the effective refractive index of the low-speed lens section A2 is relatively large. Furthermore, the acoustic lens 7 for the ultrasonic probe has a concave front surface C1, and the refractive index of the acoustic lens 7 for the ultrasonic probe is smaller than the refractive index of the object being tested. Therefore, when ultrasonic waves propagate from the acoustic lens 7 for the ultrasonic probe through the front surface C1 to the object being tested, the ultrasonic waves that pass through the high-speed lens section A1 are refracted more towards the central part in the Y direction of the acoustic lens 7 than the ultrasonic waves that pass through the low-speed lens section A2. As a result, the focal length of the high-speed lens section A1 is shorter than the focal length of the low-speed lens section A2. Here, the focal length is defined as the distance from the center of the front surface C1 of the acoustic lens 7 for the ultrasonic probe in the Y direction to the position where the width of the ultrasonic beam is narrowest in the Y direction.

[0030] Here, it is generally known that the focal length F of an acoustic lens is 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 waves propagating through the acoustic lens, and V2 is the group velocity of the ultrasonic waves propagating through the subject. By using this relationship, it can be specifically confirmed that the focal length F of the lens section A1 for the high sound velocity region is shorter than the focal length F of the lens section 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 that of the object being tested, the group velocity V1 of the ultrasonic waves propagating through the acoustic lens 7 for the ultrasonic probe is higher than the group velocity V2 of the ultrasonic waves propagating through the object being tested. Therefore, the velocity ratio (V2 / V1) of the group velocity V1 of the ultrasonic waves propagating through the acoustic lens 7 to the group velocity V2 of the ultrasonic waves propagating through the object being tested is greater than 0.0 and less than 1.0. Furthermore, since the group velocity V1 of the ultrasonic waves propagating through the high-speed lens section A1 is higher than the group velocity V1 of the ultrasonic waves propagating through the low-speed lens section A2, the velocity ratio (V2 / V1) corresponding to the high-speed lens section A1 is smaller than the velocity ratio (V2 / V1) corresponding to the low-speed lens section A2.

[0032] Here, as a specific example, if we set the velocity ratio (V2 / V1) corresponding to the high-speed lens section A1 to 0.8 and the velocity ratio (V2 / V1) corresponding to the low-speed lens section A2 to 0.9, then for the high-speed lens section A1, we obtain the relationship R = 0.2 × F, and for the low-speed lens section A2, we obtain the relationship R = 0.1 × F. Therefore, the focal length F of the high-speed lens section A1 becomes 5 × R, and the focal length F of the low-speed lens section A2 becomes 10 × R. In this way, it can be confirmed that the focal length F of the high-speed lens section A1 is shorter than the focal length F of the low-speed lens section A2.

[0033] Thus, according to the acoustic lens 7 for an ultrasonic probe of Embodiment 1 of the present invention, the ultrasonic beam formed by ultrasonic waves passing through the lens portion A1 for the high-sound-velocity region can be focused to the shallow part of the subject, and the ultrasonic beam formed by ultrasonic waves passing through the lens portion A2 for the low-sound-velocity region can be focused 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 depth. Furthermore, for example, if piezoelectric transducers that emit high-frequency ultrasound are used as multiple piezoelectric transducers 3, it is possible to obtain ultrasound images that depict the shallow parts of the subject with high resolution.

[0034] Furthermore, it has been conventionally known that an acoustic lens with a front surface having multiple radii of curvature R in the Y direction is used as a method for forming an ultrasonic beam that converges at a shallow depth and has a narrow width in the Y direction. However, in this method, because the front surface of the acoustic lens has multiple radii of curvature R in the Y direction, the focal length F of the acoustic lens is prone to change when the acoustic lens deforms upon contact with the subject, and the ultrasonic beam may not converge at the desired depth. In addition, because the front surface of the acoustic lens has multiple radii of curvature R, the acoustic lens becomes locally and abruptly thicker, making it prone to attenuation of ultrasonic waves propagating through the acoustic lens, and sometimes creating areas where the acoustic lens does not easily contact the subject. These problems contribute to a decrease in the quality of ultrasonic images.

[0035] According to the first embodiment of the present invention, the acoustic lens 7 for an ultrasonic probe has a front surface C1 with a constant radius of curvature R. Therefore, even if the acoustic lens 7 for the ultrasonic probe is deformed upon contact with a test subject, the effect of deformation is minimal, and the ultrasonic beam can be stably focused according to the desired focal length F. Furthermore, because the acoustic lens 7 for the ultrasonic probe has a front surface C1 with a constant radius of curvature R, the acoustic lens 7 does not become locally and abruptly thickened. This reduces the attenuation of ultrasonic waves propagating through the acoustic lens 7, while still allowing for the acquisition of high-quality ultrasonic images regardless of depth. Moreover, because the acoustic lens 7 does not become locally and abruptly thickened, the entire front surface C1 of the acoustic lens 7 in the Y direction can be easily brought into contact with the test subject.

[0036] Furthermore, since the front surface C1 of the acoustic lens 7 for the ultrasonic probe is concave, and a relatively thin high-speed region lens section A1 is arranged in the central part of the acoustic lens 7 for the ultrasonic probe, even when high-frequency ultrasonic waves are emitted from multiple piezoelectric transducers 3, the attenuation of high-frequency ultrasonic waves propagating through the high-speed region lens section A1 can be further reduced, and an ultrasonic image with high image quality can be obtained.

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

[0038] Surface treatments for fine particles G include, for example, oil treatment with hydrocarbon oils, ester oils, lanolin, etc.; silicone treatment with dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane, etc.; fluorine compound treatment with perfluoroalkyl group-containing esters, perfluoroalkyl silanes, perfluoropolyethers, and polymers having perfluoroalkyl groups; silane coupling agent treatment with 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, etc.; titanium coupling agent treatment with isopropyltriisostearoyl titanate, isopropyltris(dioctyl pyrophosphate) titanate, etc.; metal soap treatment; amino acid treatment with acyl glutamic acid, etc.; lecithin treatment with hydrogenated egg yolk lecithin, etc.; collagen treatment; polyethylene treatment; moisturizing treatment; inorganic compound treatment; mechanochemical treatment; and phosphate compound treatment with phosphoric acid, phosphorous acid, phosphate, phosphate, etc. Among these, phosphate compound treatment is preferred from the viewpoint of controlling the dispersion of fine particles G.

[0039] In this process, fine particles G for high-sound velocity regions with a high degree of surface treatment and fine particles G for low-sound velocity regions with a low degree of surface treatment can be obtained. For example, even when using the same surface treatment agent, increasing the amount of surface treatment agent during surface treatment will yield fine particles G with a high degree of dispersion in the base material B, while decreasing the amount of surface treatment agent will yield fine particles G with a low degree of dispersion in the base material B. Furthermore, for example, increasing the number of surface treatments will yield fine particles G with a high degree of dispersion in the base material B, while decreasing the number of surface treatments will yield fine particles G with a low degree of dispersion in the base material B.

[0040] Here, in order to reduce the attenuation of the ultrasonic waves emitted from the piezoelectric transducer 3 and propagating through the acoustic lens 7 for the ultrasonic probe, it is preferable that the particles have a diameter of 0.01 μm or more and 100.00 μm or less, and more preferably 1.00 μm or more and 10.00 μm or less. The diameter of the fine particles G can be measured as follows. First, fine particles G that have been sufficiently surface-treated are added to methanol to a concentration of 0.5 mass%, and the methanol is subjected to ultrasonic waves for 10 minutes to disperse the fine particles G. The particle size distribution of the fine particles G dispersed in methanol in this way is measured using a laser analysis scattering particle size distribution analyzer (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 in this case is the particle diameter corresponding to 50% of the cumulative distribution when the particle size distribution is expressed as a cumulative distribution.

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

[0042] The mixture for the high-sound-velocity region and the mixture for the low-sound-velocity region obtained in this way are placed in a molding mold and heated to cure them, respectively, to obtain a lens member for the high-sound-velocity region and a lens member for the low-sound-velocity region. The lens member for the high-sound-velocity region and the lens member for the low-sound-velocity region obtained in this way each have a curved front surface having the same radius of curvature R. The lens member for the high-sound-velocity region is the member corresponding to the lens portion A1 for the high-sound-velocity region of the acoustic lens 7 for the ultrasonic probe, and the lens member for the low-sound-velocity region is the member corresponding to the lens portion A2 for the low-sound-velocity region.

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

[0044] Incidentally, an acoustic lens is known for forming an ultrasonic beam with a narrow width in the Y direction, which has a front surface with multiple radii of curvature R in the Y direction. Generally, ultrasonic probes that emit high-frequency ultrasonic waves such as 12 MHz to 15 MHz are often small in size, and it has been difficult to manufacture an acoustic lens with a front surface having multiple radii of curvature R in the Y direction to fit such a small ultrasonic probe.

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

[0046] Next, an ultrasonic diagnostic apparatus having an ultrasonic probe 1 according to Embodiment 1 of the present invention will be described. As shown in Figure 3, in the ultrasonic diagnostic apparatus 11, a transmitting / receiving circuit 12, an image generation unit 13, a display control unit 14, and a monitor 15 are sequentially connected to the ultrasonic probe 1. In addition, a device control unit 16 is connected to the transmitting / receiving circuit 12, the image generation unit 13, and the display control unit 14. An input device 17 is also connected to the device control unit 16. Furthermore, a memory (not shown) is connected to the device control unit 16. Furthermore, the ultrasound diagnostic device 11 includes an ultrasound probe 21 which includes an ultrasound transducer 1 and a transmitting / receiving circuit 12. In addition, a processor 22 for the ultrasound diagnostic device 11 is configured by an image generation unit 13, a display control unit 14, and a device control unit 16.

[0047] The transmitting / receiving circuit 12 transmits ultrasonic waves from the ultrasonic transducer 1 and generates a sound line signal based on the received signal acquired by the ultrasonic transducer 1, under the control of the device control unit 16. As shown in Figure 4, the transmitting / receiving circuit 12 has a pulser 23 connected to the ultrasonic transducer 1, and an amplifier 24, an AD (Analog Digital) converter 25, and a beamformer 26 connected sequentially in series from the ultrasonic transducer 1.

[0048] The pulser 23 includes, for example, multiple pulse generators and, based on a transmission delay pattern selected in accordance with a control signal from the device control unit 16, supplies each drive signal to the multiple piezoelectric transducers 3 of the ultrasonic probe 1, adjusting the delay amount, so that the ultrasonic waves transmitted from the multiple piezoelectric transducers 3 form an ultrasonic beam. In this way, when a pulsed or continuous wave voltage is applied to the electrodes of the piezoelectric transducers 3, the piezoelectric transducers 3 expand and contract, generating pulsed or continuous wave ultrasonic waves from each piezoelectric transducer 3, and an ultrasonic beam is formed from the combined wave of these ultrasonic waves.

[0049] The transmitted ultrasonic beam is reflected, for example, by tissue within the subject and propagates toward the ultrasonic transducer 1 of the ultrasonic probe 21. Each piezoelectric transducer 3 of the ultrasonic transducer 1 expands and contracts upon receiving the ultrasonic echo propagating toward the ultrasonic transducer 1 in this manner, generating a received signal which is an electrical signal, and outputs these received signals to the amplification unit 24.

[0050] The amplification unit 24 amplifies the signals input from each piezoelectric transducer 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 amplification unit 24 into digital received data and transmits this received data to the beamformer 26. The beamformer 26 performs so-called receive focus processing by adding each received data converted by the AD conversion unit 25 with a corresponding delay, according to the sound velocity or sound velocity distribution set based on the received delay pattern selected according to the control signal from the device control unit 16. Through this receive focus processing, each received data converted by the AD conversion unit 25 is added in phase and a sound ray signal with a focused ultrasonic echo is obtained.

[0051] As shown in Figure 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 connected in series in sequence. The signal processing unit 27 applies distance-dependent attenuation correction to the sound line signal generated by the beamformer 26 of the transmitting / receiving circuit 12 according to the depth of the ultrasonic reflection position, and then performs envelope detection processing to generate a B-mode image signal, which is tomographic image information about the tissue within the subject.

[0052] The DSC28 converts the B-mode image signal generated by the signal processing unit 27 into an image signal that follows the scanning method of a normal television signal (raster conversion). The image processing unit 29 performs various necessary image processing, 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 this invention, the B-mode image signal processed by the image processing unit 29 is simply referred to as an ultrasonic image.

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

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

[0055] Although not shown in the diagram, the memory connected to the device control unit 16 stores the control program for the ultrasound diagnostic device 11, etc. The memory can be a flash memory, HDD (Hard Disk Drive), SSD (Solid State Drive), FD (Flexible Disc), MO (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.

[0056] The processor 22, which includes an image generation unit 13, a display control unit 14, and a 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 also be composed of FPGAs (Field Programmable Gate Arrays), DSPs (Digital Signal Processors), ASICs (Application Specific Integrated Circuits), GPUs (Graphics Processing Units), and other ICs (Integrated Circuits), or a combination thereof.

[0057] Furthermore, the image generation unit 13, display control unit 14, and device control unit 16 of the processor 22 can be partially or entirely integrated into a single CPU or the like.

[0058] The ultrasound diagnostic apparatus 11 in Embodiment 1 of the present invention is equipped with an ultrasound probe 1 having an acoustic lens 7 for the ultrasound probe according to Embodiment 1 of the present invention, so that ultrasound images with high image quality can be obtained regardless of depth. In particular, when relatively high-frequency ultrasound is emitted from the ultrasound probe 1, ultrasound images in which shallow areas are depicted with high resolution can be obtained.

[0059] The dispersion of fine particles G in the base material B of the acoustic lens 7 for the ultrasonic probe is adjusted by surface treatment of the fine particles G, but the method of adjusting the dispersion of fine particles G is not limited to surface treatment. For example, the dispersion of fine particles G in the base material B can be changed by changing the method of mechanically mixing the fine particles G into the base material B. For example, by mixing fine particles G into the base material B using a so-called propeller-type mixer, the dispersion of fine particles G can be made lower than when mixing fine particles G using a planetary-type mixer. Therefore, when preparing a mixture for the high-sonic-velocity region, fine particles G can be mixed into the base material B using a propeller-type mixer, and when preparing a mixture for the low-sonic-velocity region, fine particles G can be mixed into the base material B using a planetary-type mixer. Furthermore, the degree of dispersion of fine particles G can also be changed, for example, by changing the time during which the fine particles G are mixed into the base material B.

[0060] Furthermore, the degree of dispersion of the fine particles G can also be changed by altering the curing time of the base material B. For example, lowering the heating temperature of the mixture of base material B and fine particles G and increasing the curing time of base material B can lower the degree of dispersion of the fine particles G, while raising the heating temperature of the mixture of base material B and fine particles G and shortening the curing time of base material B can increase the degree of dispersion of the fine particles G.

[0061] Furthermore, while an example is shown in which the acoustic lens 7 for the ultrasonic probe is composed of two types of regions, a lens section A1 for the high-sound velocity region and a lens section A2 for the low-sound velocity region, the acoustic lens 7 for the ultrasonic probe can also be composed of three or more regions with different dispersion degrees of the fine particles G, provided that the dispersion degree of the fine particles G in the base material B increases from the center to both ends in the Y direction. In addition, the acoustic lens 7 for the ultrasonic probe can also be composed such that the dispersion degree of the fine particles G in the base material B increases continuously from the center to both ends in the Y direction. This makes it possible to obtain ultrasonic images with more uniform image quality.

[0062] Furthermore, it has been explained that the number of microparticles G per unit volume in the high-speed lens section A1 and the number of microparticles G per unit volume in the low-speed lens section A2 are the same, but they can also be finely adjusted to match the acoustic impedance of the high-speed lens section A1 and the low-speed lens section A2.

[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 may also have a convex front surface. As shown in Figure 6, the ultrasonic probe 1A in Embodiment 2 of the present invention is equipped with an acoustic lens 7A for ultrasonic probes instead of the acoustic lens 7 for ultrasonic probes in the ultrasonic probe 1 in Embodiment 1 shown in Figures 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, similar to the acoustic lens 7 for an ultrasonic probe in Embodiment 1, but has a convex front surface C2 with a constant radius of curvature R. The acoustic lens 7A for an ultrasonic probe has a lens portion A2 for the low sound velocity region with a high degree of dispersion of fine particles G in the central part in the Y direction, and a lens portion A1 for the high sound velocity region with a low degree of dispersion of fine particles G at both ends in the Y direction. Thus, in the acoustic lens 7A for an ultrasonic probe, the degree of dispersion of fine particles G decreases from the central part in the Y direction towards both ends. Furthermore, the number of fine particles G per unit volume in the acoustic lens 7A for an ultrasonic probe is the same from the central part in the Y direction to both ends. Therefore, the acoustic impedance of the lens portion A2 for the low sound velocity region and the acoustic impedance of the lens portion A1 for the high sound velocity region are approximately the same. Furthermore, the acoustic lens 7A for the ultrasonic probe is made of a material with a refractive index greater than that of the subject in order to focus the ultrasonic beam into the subject.

[0065] Here, the group velocity V1 in the Z direction of the ultrasonic waves propagating through the acoustic lens 7A for the ultrasonic probe is relatively low in the low-speed region lens section A2 located in the center in the Y direction, and relatively high in the high-speed region lens sections A1 located at both ends in the Y direction. Therefore, the effective refractive index of the low-speed region lens section A2 is relatively large, and the effective refractive index of the high-speed region lens section A1 is relatively small. Furthermore, the acoustic lens 7A for the ultrasonic probe has a convex front surface C2, and the refractive index of the acoustic lens 7A for the ultrasonic probe is greater than the refractive index of the subject. Therefore, when ultrasonic waves propagate from the acoustic lens 7A for the ultrasonic probe through the front surface C2 to the subject, the ultrasonic waves that pass through the low-speed region lens section A2 are refracted more towards the center in the Y direction of the acoustic lens 7A than the ultrasonic waves that pass through the high-speed region lens section A1. Therefore, the focal length F of lens section A2 for the low-sonic-velocity region is shorter than the focal length F of lens section A1 for the high-sonic-velocity region.

[0066] Furthermore, the acoustic lens 7A for the ultrasonic probe has a convex front surface C2 with a constant radius of curvature R, and the refractive index of the acoustic lens 7A for the ultrasonic probe is greater than that of the object being tested. Therefore, the group velocity V1 of the ultrasonic waves propagating through the acoustic lens 7A for the ultrasonic probe is lower than the group velocity V2 of the ultrasonic waves propagating through the object being tested. Consequently, the velocity ratio (V2 / V1) of the group velocity V1 of the ultrasonic waves propagating through the acoustic lens 7A to the group velocity V2 of the ultrasonic waves propagating through the object being tested is greater than 1.0. Moreover, the group velocity V1 of the ultrasonic waves propagating through the lens section A2 for the low-sound-velocity region is lower than the group velocity V1 of the ultrasonic waves propagating through the lens section A1 for the high-sound-velocity region. Therefore, the velocity ratio (V2 / V1) corresponding to the lens section A2 for the low-sound-velocity region is greater than the velocity ratio (V2 / V1) corresponding to the lens section A1 for the high-sound-velocity region.

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

[0068] Thus, according to the acoustic lens 7A for an ultrasonic probe of Embodiment 2 of the present invention, the ultrasonic beam formed by ultrasonic waves passing through the lens portion A2 for the low sound velocity region can be focused to the shallow part of the subject, and the ultrasonic beam formed by ultrasonic waves passing through the lens portion A1 for the high sound velocity region can be focused to 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 with high image quality can be obtained regardless of depth. Furthermore, for example, if piezoelectric transducers that emit high-frequency ultrasound are used as multiple piezoelectric transducers 3, it is possible to obtain ultrasound images that depict the shallow parts of the subject with high resolution.

[0069] Furthermore, because the acoustic lens 7A for the ultrasonic transducer has a front surface C2 with a constant radius of curvature R, even if the acoustic lens 7A for the ultrasonic transducer deforms upon contact with the subject, the effect of the deformation is minimal, and the ultrasonic beam can be stably focused according to the desired focal length F. Also, because the acoustic lens 7A for the ultrasonic transducer has a front surface C2 with a constant radius of curvature R, the acoustic lens 7A for the ultrasonic transducer does not thicken rapidly in a localized area, and while reducing the attenuation of ultrasonic waves propagating through the acoustic lens 7A, high-quality ultrasonic images can be obtained regardless of depth. Moreover, because the acoustic lens 7A for the ultrasonic transducer does not thicken rapidly in a localized area, the entire front surface C2 of the acoustic lens 7A in the Y direction can be easily brought into contact with the subject.

[0070] Although an example is shown in which the acoustic lens 7A for the ultrasonic probe is composed of two types of regions, a lens section A2 for the low sound velocity region and a lens section A1 for the high sound velocity region, the acoustic lens 7A for the ultrasonic probe can also be composed of three or more types of regions with different dispersion degrees of the fine particles G, provided that the dispersion degree of the fine particles G in the base material B decreases from the center to both ends in the Y direction. Furthermore, the acoustic lens 7A for the ultrasonic probe can also be composed such that the dispersion degree of the fine particles G in the base material B decreases continuously from the center to both ends in the Y direction. This makes it possible to obtain ultrasonic images with more uniform image quality.

[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, but the acoustic matching layer 4 may also include a layer formed from the base material B in which a plurality of fine particles G are dispersed. As shown in Figure 7, the ultrasonic probe 1B in Embodiment 3 is equipped with an acoustic matching layer 4B instead of the acoustic matching layer 4 in the ultrasonic probe 1 in Embodiment 1 shown in Figure 2. Furthermore, the acoustic matching layer 4B is equipped with a first matching layer 5B instead of the first matching layer 5 in the acoustic matching layer 4 in Embodiment 1. As shown in Figure 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 dispersion of fine particles G increases from the center in the Y direction towards both ends, and the number of fine particles G per unit volume in the first matching layer 5 is the same from the center in the Y direction to both ends. In the example shown in Figure 7, a matching section H1 for the high frequency region with a low dispersion of fine particles G is formed in the center in the Y direction, and matching sections H2 for the low frequency region with a high dispersion of fine particles G are formed at both ends in the Y direction. Here, the matching section H1 for the high frequency region is formed at a position in the Y direction corresponding to the lens section A1 for the high sound velocity region of the acoustic lens 7 for the ultrasonic probe, and the matching section H2 for the low frequency region is formed at a position in the Y direction corresponding to the lens section A2 for the low sound velocity region of the acoustic lens 7 for the ultrasonic probe. Furthermore, since the number of fine particles G per unit volume is the same from the center in the Y direction to both ends of the first matching layer 5B, the acoustic impedance of the matching section H1 for the high frequency region and the acoustic impedance of the matching section H2 for the low frequency region are approximately the same.

[0073] Here, the relationship V = Q × W is known, where V is the group velocity of sound, Q is the frequency, and W is the wavelength. Due to the resonance conditions caused by the thickness of the first matching layer 5B, ultrasonic waves with a constant wavelength W are amplified. Therefore, if the wavelength W is kept constant, the group velocity V of the ultrasonic waves propagating through the high-frequency matching section H1 of the first matching layer 5B is relatively fast, resulting in a high frequency Q. Conversely, the group velocity V of the ultrasonic waves propagating through the low-frequency matching section H2 is relatively slow, resulting in a low frequency.

[0074] Furthermore, since the high-frequency region matching section H1 is located in the center 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 low-frequency region matching sections H2 are located at both ends of the acoustic matching layer 4B, they also have relatively wide aperture widths. Therefore, the width in the Y direction of the ultrasonic beam focused by the acoustic lens 7 for the ultrasonic transducer after ultrasonic waves have passed through the high-frequency region matching section H1 is relatively narrow, while the width in the Y direction of the ultrasonic beam focused by the acoustic lens 7 after ultrasonic waves have passed through the low-frequency region matching section H2 is relatively wide.

[0075] Therefore, the ultrasonic beam formed from ultrasound transmitted through the high-frequency matching section H1 of the first matching layer 5B and the high-sound-velocity lens section A1 of the acoustic lens 7 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. On the other hand, the ultrasonic beam formed from ultrasound transmitted through the low-frequency matching section H2 of the first matching layer 5B and the low-sound-velocity lens section A2 of the acoustic lens 7 for the ultrasonic probe has a relatively low frequency Q and converges according to a long focal length F. As a result, the ultrasonic probe 1B in Embodiment 3 of the present invention makes it possible to obtain ultrasonic images with higher image quality regardless of depth.

[0076] Although the aspects of Embodiment 3 are shown to be applied to the ultrasonic probe 1 in Embodiment 1, they can also be applied to the ultrasonic probe 1A in Embodiment 2 in the same manner. For example, as shown in Figure 8, the ultrasonic probe 1C in the modified form of Embodiment 3 is the ultrasonic probe 1A in Embodiment 2 shown in Figure 6, in which the first matching layer 5 is replaced with a first matching layer 5B.

[0077] In this case, the ultrasonic beam formed from ultrasound transmitted through the high-frequency matching section H1 of the first matching layer 5B and the low-sound velocity lens section A2 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. On the other hand, the ultrasonic beam formed from ultrasound transmitted through the low-frequency matching section H2 of the first matching layer 5B and the high-sound velocity lens section A1 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 modified embodiment 3 of the present invention, an ultrasonic image with higher image quality can be obtained regardless of depth, similar to the ultrasonic probe 1B in embodiment 3.

[0078] Furthermore, by making the Y-direction length of the high-frequency region matching section H1 longer than the Y-direction length of the low-frequency region matching section H2, the proportion of ultrasound transmitted and received through the high-frequency region matching section H1 can be increased. Ultrasound with higher frequencies is more susceptible to attenuation, but by making the Y-direction length of the high-frequency region matching section H1 longer, even if relatively high-frequency ultrasound is attenuated within the subject, a sufficient amount of ultrasound echo received through the high-frequency region matching section H1 can be ensured, preventing a decrease in the brightness of the ultrasound image at relatively shallow depths. This makes it possible to obtain ultrasound images with more uniform image quality.

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

[0080] Furthermore, while an example is shown in which the first matching layer 5B is composed of two types of regions, a matching section H1 for the high-frequency region and a matching section H2 for the low-frequency region, the first matching layer 5B can also be composed of three or more regions with different dispersion degrees of the particles G, provided that the transmission and reception frequencies of the ultrasound decrease from the center to both ends in the Y direction, and the dispersion degree of the particles G in the base material B increases from the center to both ends in the Y direction. Alternatively, the first matching layer 5B can be configured such that the dispersion degree of the particles G in the base material B increases continuously from the center to both ends in the Y direction. Therefore, ultrasound images with more uniform image quality can be obtained.

[0081] Furthermore, for example, the first matching layer 5B can be constructed as a multilayer structure consisting of multiple layers with different acoustic impedances. For example, layers with multiple fine particles G dispersed in a base material B with high acoustic impedance can be arranged as you move toward the piezoelectric vibrator 3 in the Z direction, and layers with multiple fine particles G dispersed in a base material B with low acoustic impedance can be arranged as you move toward the second matching layer 6 in the Z direction. Also, 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, layers with a large number of fine particles G per unit volume dispersed in the base material B can be arranged as you move toward the piezoelectric vibrator 3 in the Z direction, and layers with a small number of fine particles G per unit volume dispersed in the base material B can be arranged as you move toward the second matching layer 6 in the Z direction.

[0082] Thus, by having a multilayer structure in which the first matching layer 5B consists of multiple layers having different acoustic impedances, the acoustic impedance between the object in contact with the ultrasonic probe 1B and the piezoelectric transducer 3 can be accurately matched, making it easier to introduce ultrasound into the object.

[0083] Furthermore, although not shown in the figures, the ultrasound diagnostic apparatus 11 having the ultrasound probe 1B or ultrasound probe 1C in Embodiment 3 is equipped with a so-called low-pass filter and a high-pass filter, and by using the low-pass filter and high-pass filter, depth-dependent filtering can be performed on the received data digitized by the AD conversion unit 25, for example. More specifically, for example, in shallow areas greater than or equal to the focal depth of the ultrasound beam, low-frequency component signals below a predetermined lower limit can be cut, and an ultrasound image can be generated using only high-frequency component signals. In deep areas greater than the focal depth of the ultrasound beam, high-frequency component signals above a predetermined upper limit can be cut, and an ultrasound image can be generated using only low-frequency component signals.

[0084] Furthermore, for example, at depths greater than the focal depth of the ultrasound beam, it is possible to gradually cut out high-frequency components of the signal so that the proportion of low-frequency components increases as the depth increases. In this way, by applying depth-dependent filtering to the received data, it is possible to obtain ultrasound images with higher image quality regardless of depth.

[0085] Embodiment 4 In the ultrasonic transducer 1 of Embodiment 1, the plurality of piezoelectric transducers 3 have a constant thickness in the Y direction, but their thickness may change depending on their position in the Y direction. As shown in Figure 9, the ultrasonic probe 1D in Embodiment 4 of the present invention is the same as the ultrasonic probe 1 in Embodiment 1 shown in Figures 1 and 2, but with a backing material 2D instead of backing material 2, and a plurality of piezoelectric transducers 3D instead of a plurality of piezoelectric transducers 3.

[0086] The backing material 2D has a constant thickness in the center in the Y direction. At both ends in the Y direction, the thickness of the backing material 2D gradually decreases as it approaches the ends in the Y direction.

[0087] Each of the multiple piezoelectric transducers 3D includes a high-frequency piezoelectric section K1 having a constant thickness T1 at its center in the Y direction, and a low-frequency piezoelectric section K2 at both ends in the Y direction, the thickness of each piezoelectric transducer 3D gradually increasing from thickness T1 to a constant thickness T2 as it moves from the center to both ends in the Y direction. The high-frequency piezoelectric section K1 is positioned in the Y direction at a location corresponding to the high-sound-velocity lens section A1 of the acoustic lens 7 for the ultrasonic transducer, and the low-frequency piezoelectric section K2 is positioned in the Y direction at a location corresponding to the low-sound-velocity lens section A2 of the acoustic lens 7 for the ultrasonic transducer. In the example shown in Figure 9, each of the low-frequency piezoelectric sections K2 of the multiple piezoelectric transducers 3D has an inclined surface section J that contacts the backing material 2D and is inclined with a constant inclination so as it moves from the center to both ends in the Y direction away from the acoustic matching layer 4.

[0088] Here, the thicker the piezoelectric transducer 3D becomes, the lower the transmission and reception frequency of the ultrasonic waves transmitted by the piezoelectric transducer 3D becomes, and the thinner the piezoelectric transducer 3D becomes, the higher the transmission and reception frequency of the ultrasonic waves transmitted by the piezoelectric transducer 3D becomes. Therefore, the piezoelectric unit K1 for the high-frequency range transmits and receives relatively high-frequency ultrasonic waves, and the piezoelectric unit K2 for the low-frequency range transmits and receives relatively low-frequency ultrasonic waves.

[0089] Therefore, the relatively high-frequency ultrasonic waves emitted from the high-frequency piezoelectric sections K1 of the multiple piezoelectric transducers 3D propagate through the high-speed region lens section A1 of the acoustic lens 7 for the ultrasonic probe, and the ultrasonic beam formed from the ultrasonic waves that have passed through the high-speed region lens section A1 has a narrow width in the Y direction and converges according to a relatively short focal length F. In addition, the relatively low-frequency ultrasonic waves emitted from the low-frequency piezoelectric sections K2 of the multiple piezoelectric transducers 3D propagate through the low-speed region lens section A2 of the acoustic lens 7 for the ultrasonic probe, and the ultrasonic beam formed from the ultrasonic waves that have passed through the low-speed region lens section A2 converges according to a relatively long focal length F.

[0090] In this way, according to the ultrasonic probe 1D in Embodiment 4 of the present invention, the multiple piezoelectric transducers 3D become thicker from the center to both ends in the Y direction. As a result, the transmission and reception frequencies of the ultrasonic waves from each piezoelectric transducer 3D become lower from the center to both ends in the Y direction. Therefore, a relatively high-frequency ultrasonic beam with a narrow width in the Y direction is focused at shallow depths, while a relatively low-frequency ultrasonic beam that is less attenuated is focused at deeper depths. Consequently, ultrasonic images with high image quality can be obtained regardless of depth.

[0091] Although the aspects of Embodiment 4 are shown to be applied to the ultrasonic probe 1 in Embodiment 1, they can also be applied to the ultrasonic probe 1A in Embodiment 2 in the same manner. For example, as shown in Figure 10, the ultrasonic probe 1E in the modified form of Embodiment 4 is the same as the ultrasonic probe 1A shown in Figure 6, but with a backing material 2D instead of backing material 2, and multiple piezoelectric transducers 3D instead of multiple piezoelectric transducers 3.

[0092] In this case, relatively high-frequency ultrasonic waves emitted from the high-frequency piezoelectric sections K1 of the multiple piezoelectric transducers 3D propagate through the low-sound-velocity lens section A2 of the acoustic lens 7A for the ultrasonic probe. The ultrasonic beam formed from the ultrasonic waves that have passed through the low-sound-velocity lens section A2 has a narrow width in the Y direction and converges according to a relatively short focal length F. In addition, relatively low-frequency ultrasonic waves emitted from the low-frequency piezoelectric sections K2 of the multiple piezoelectric transducers 3D propagate through the high-sound-velocity lens section A1 of the acoustic lens 7A for the ultrasonic probe. The ultrasonic beam formed from the ultrasonic waves that have passed through the high-sound-velocity lens section A1 converges according to a relatively long focal length F.

[0093] Thus, according to the ultrasonic probe 1E in the modified embodiment 4 of the present invention, an ultrasonic image with higher image quality can be obtained regardless of depth, similar to the ultrasonic probe 1D in embodiment 4.

[0094] Furthermore, Figures 9 and 10 show that the piezoelectric portion K2 for the low frequency range of the multiple piezoelectric resonators 3D each has an inclined surface portion J that has a constant inclination and moves away from the acoustic matching layer 4 as it moves from the center to both ends in the Y direction. However, the invention is not particularly limited to this embodiment, as long as the multiple piezoelectric resonators 3D each become thicker as they move from the center to both ends in the Y direction. Also, for example, the inclination of the inclined surface portion J may gradually change from the center to both ends in the Y direction so that the thickness of the piezoelectric portion K2 for the low frequency range changes smoothly from a thickness T1 to a thickness T2 as it moves from the center to both ends in the Y direction. Also, for example, the piezoelectric portion K2 for the low frequency range may have a planar portion (not shown) extending along the X and Y directions instead of the inclined surface portion J so that it has a constant thickness T2 that is thicker than the thickness T1.

[0095] Furthermore, by making the Y-direction length of the high-frequency piezoelectric section K1 longer than the Y-direction length of the low-frequency piezoelectric section K2, the proportion of relatively high-frequency ultrasound emitted by the multiple piezoelectric transducers 3D can be increased. Although ultrasound with higher frequencies is more susceptible to attenuation, by making the Y-direction length of the high-frequency piezoelectric section K1 longer, even if relatively high-frequency ultrasound is attenuated within the subject, a sufficient amount of ultrasound echo received by the high-frequency piezoelectric section K1 can be ensured, preventing a decrease in the brightness of the ultrasound image at relatively shallow depths. This makes it possible to obtain ultrasound images with more uniform image quality.

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

[0097] Furthermore, although not shown in the figures, the ultrasound diagnostic apparatus 11 having the ultrasound probe 1D or ultrasound probe 1E in Embodiment 4 is equipped with a so-called low-pass filter and a high-pass filter, and by using the low-pass filter and high-pass filter, depth-dependent filtering can be performed on the received data digitized by the AD conversion unit 25, for example. More specifically, for example, in shallow areas greater than or equal to the focal depth of the ultrasound beam, low-frequency component signals below a predetermined lower limit can be cut, and an ultrasound image can be generated using only high-frequency component signals. In deep areas greater than the focal depth of the ultrasound beam, high-frequency component signals above a predetermined upper limit can be cut, and an ultrasound image can be generated using only low-frequency component signals.

[0098] Furthermore, for example, at depths greater than the focal depth of the ultrasound beam, it is possible to gradually cut out high-frequency components of the signal so that the proportion of low-frequency components increases as the depth increases. In this way, by applying depth-dependent filtering to the received data, it is possible to obtain ultrasound images with higher image quality regardless of depth.

[0099] Furthermore, the aspects of Embodiment 4 can also be applied to Embodiment 3 in the same manner as to Embodiments 1 and 2. [Explanation of Symbols]

[0100] 1,1A,1B,1C,1D,1E Ultrasonic probe, 2,2D Backing material, 3,3D Piezoelectric transducer, 4,4B Acoustic matching layer, 5,5B First matching layer, 6 Second matching layer, 7,7A Acoustic lens for ultrasonic probe, 8 Separation unit, 11 Ultrasonic diagnostic device, 12 Transceiver circuit, 13 Image generation unit, 14 Display control unit, 15 Monitor, 16 Device control unit, 17 Input device, 21 Ultrasonic probe, 22 Processor, 23 Pulsar, 24 Amplifier, 25 AD conversion unit, 26 Beamformer, 27 Signal processing unit, 28 DSC, 29 Image processing unit, A1 Lens unit for high sound velocity region, A2 Lens unit for low sound velocity region, B Base material, C1,C2 Front surface, G Fine particles, H1 Matching unit for high frequency region, H2 Matching unit for low frequency region, K1 Piezoelectric unit for high frequency region, K2 Piezoelectric element for low frequency range, P array pitch, T1, T2 thickness.

Claims

1. An acoustic lens positioned at the front end of an ultrasonic probe, Having a concave front surface, Formed from a base material in which multiple fine particles are dispersed, The base material has a plurality of regions arranged in the elevation direction, As the degree of dispersion of the fine particles increases from the center to both ends in the elevation direction, the speed of sound decreases from the center to both ends in the elevation direction. An acoustic lens for an ultrasonic probe, wherein the number of fine particles per unit volume in each of the aforementioned multiple regions is the same.

2. The acoustic lens for an ultrasonic probe according to claim 1, comprising a lens portion for a high-sound velocity region located in the center of the elevation direction and lens portions for a low-sound velocity region located at both ends of the elevation direction.

3. An acoustic lens positioned at the front end of an ultrasonic probe, Having a convex front surface, Formed from a base material in which multiple fine particles are dispersed, The base material has a plurality of regions arranged in the elevation direction, As the degree of dispersion of the fine particles decreases from the center to both ends in the elevation direction, the speed of sound increases from the center to both ends in the elevation direction. An acoustic lens for an ultrasonic probe, wherein the number of fine particles per unit volume in each of the aforementioned multiple regions is the same.

4. The acoustic lens for an ultrasonic probe according to claim 3, comprising a lens portion for the low sound velocity region located in the center of the elevation direction and lens portions for the high sound velocity region located at both ends of the elevation direction.

5. The acoustic lens for an ultrasonic probe according to any one of claims 1 to 4, wherein the front surface has the same radius of curvature from the center to both ends in the elevation direction.

6. The aforementioned fine particles have a diameter of 0.01 μm or more and 100.00 μm or less, as described in any one of claims 1 to 5, for use as an acoustic lens for an ultrasonic probe.

7. The aforementioned fine particles have a diameter of 1.00 μm or more and 10.00 μm or less, as described in claim 6, for an ultrasonic probe acoustic lens.

8. The aforementioned fine particles are made of iron, tungsten, alumina, zirconia, or silica, as described in any one of claims 1 to 7.

9. Backing material and 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 equipped with [a specific feature].

10. The ultrasonic probe according to claim 9, wherein the acoustic matching layer includes a first matching layer in which the transmission and reception frequencies of ultrasonic waves decrease as you move from the center to both ends in the elevation direction.

11. The ultrasonic probe according to claim 9 or 10, wherein each of the plurality of piezoelectric transducers becomes thicker from the center to both ends in the elevation direction, thereby lowering the ultrasonic transmission and reception frequency from the center to both ends in the elevation direction.

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

13. An ultrasound diagnostic apparatus having an ultrasound probe as described in claim 12.

Images