Acoustic lens, ultrasonic probe, and ultrasonic diagnostic device

Abstract

To provide an acoustic lens that allows an ultrasonic image with large depth of field and high spatial resolution to be generated.SOLUTION: There is provided an acoustic lens 21 applied to an ultrasonic probe, which converges ultrasonic waves sent out from a piezoelectric vibrator, and forms an ultrasonic beam. An ultrasonic radiation surface of the acoustic lens 21 includes a first region 21a positioned at a lens center part for forming a focal point at a position corresponding to a deep part of an ultrasonic beam, and a second region 21b positioned at a lens outside in the first region 21a for forming a focal point at a position corresponding to a shallow part of the ultrasonic beam. A profile is drawn in which the depth of the focal points formed by the lens parts at the respective positions of the first region 21a and the second region 21b becomes smaller continuously from the lens center part side toward the lens outside.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to an acoustic lens, an ultrasound probe, and an ultrasound diagnostic device. [Background technology]

[0002] Conventionally, there is known an ultrasound diagnostic device that transmits ultrasound waves toward a subject, receives the reflected waves, and performs predetermined signal processing on the received signals to visualize the shape, properties, or dynamics of the subject's interior as an ultrasound image (see, for example, Patent Document 1). Since ultrasound diagnostic devices can obtain ultrasound images through a simple operation of placing an ultrasound probe on the body surface or inserting it inside the body, they are safe and impose a small burden on the subject.

[0003] Ultrasound diagnostic devices are used when inserting a puncture needle into the body of a patient as a subject to sample tissue or body fluid to diagnose biological tissue, or when using a puncture needle to perform treatment. In these diagnoses or treatments, practitioners such as doctors can perform puncture while checking the position of the puncture needle and the position of the puncture site (target) by looking at ultrasound images obtained by the ultrasound diagnostic device. Note that a puncture needle is a medical instrument such as a medical needle or a catheter that is inserted into a subject. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-024777 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in this type of ultrasound diagnostic device, it is required to ensure a wide depth of field and high spatial resolution in order to enable a user to accurately visually identify the position of a puncture needle and the position of a target from an ultrasound image.

[0006] One of the means for solving such a problem is to optimize the shape of the acoustic lens of the ultrasonic probe. Specifically, if the ultrasonic waves emitted from the piezoelectric transducer can be converted into a uniformly narrow and focused ultrasonic beam over a wide range from shallow to deep areas by the acoustic lens, it becomes possible to improve the signal-to-noise ratio of the ultrasonic echo from each depth position in the depth direction inside the subject, and therefore it becomes possible to secure a wide depth of field and high spatial resolution.

[0007] Therefore, in order to form a uniformly thin and focused ultrasonic beam over a wide range from shallow to deep areas, the inventors of the present application designed the ultrasonic emission surface of the acoustic lens to be divided along the slice direction into an inner region located in the center of the lens and an outer region located outside the inner region, and investigated an acoustic lens having a shape in which the inner region forms a focus in the shallow area and the outer region forms a focus in the deep area.

[0008] However, such an acoustic lens faces the problem that a beam skirt is formed in a shallow area, and the spatial resolution in the shallow area in an ultrasound image deteriorates (described later with reference to FIG. 7).

[0009] The present disclosure has been made in consideration of the above problems, and aims to provide an acoustic lens, an ultrasound probe, and an ultrasound diagnostic device that enable the generation of ultrasound images having a wide depth of field and high spatial resolution. [Means for solving the problem]

[0010] The present disclosure, which solves the above-mentioned problems, is Applied to ultrasonic probes, Multiple An acoustic lens that focuses ultrasonic waves emitted from a piezoelectric transducer to form an ultrasonic beam, The ultrasonic emitting surface of the acoustic lens is a first region located in the center of the lens and forming a focal point at a position corresponding to a deep portion of the ultrasonic beam; and a second region located outside the first region and forming a focal point at a position corresponding to a shallow portion of the ultrasonic beam, The depth of focus formed by the lens portion at each position of the first region and the second region is In a slice direction perpendicular to the direction in which the plurality of piezoelectric transducers are arranged, A profile that becomes continuously shallower from the center of the lens toward the outside of the lens is drawn. It is an acoustic lens.

[0011] In other respects, The ultrasonic probe has the above acoustic lens.

[0012] In other respects, An ultrasonic diagnostic device having the above ultrasonic probe. Effect of the Invention

[0013] The acoustic lens according to the present disclosure makes it possible to generate ultrasound images with a wide depth of field and high spatial resolution. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram showing an example of the appearance of an ultrasound diagnostic device. [Diagram 2] FIG. 1 is a diagram showing an example of the configuration of an ultrasonic probe. [Diagram 3] A block diagram showing an example of the configuration of the main parts of a control system of an ultrasound diagnostic device. [Figure 4] FIG. 1 is a diagram showing an example of the shape of an acoustic lens according to prior art 1. [Diagram 5] FIG. 1 shows an example of the shape of an acoustic lens according to prior art 2. [Figure 6] FIG. 1 is a diagram explaining the design concept of an acoustic lens according to prior art 2. [Figure 7] FIG. 13 is a diagram showing an example of a beam tail generated in an ultrasonic beam formed by an acoustic lens according to prior art 2. [Figure 8] FIG. 1 is a diagram showing an example of the shape of an acoustic lens according to an embodiment of the present invention; [Figure 9] FIG. 1 is a diagram for explaining the design concept of an acoustic lens according to an embodiment of the present invention. [Figure 10]FIG. 1 is a diagram showing a profile indicating the depth of a focal point formed by a lens portion at each position on the ultrasonic radiation surface of an acoustic lens according to an embodiment of the present invention; [Figure 11] FIG. 1 is a schematic diagram showing a focal depth profile of an acoustic lens according to an embodiment of the present invention, superimposed on a shape profile; [Figure 12] 12A shows the sound pressure distribution of an ultrasonic beam formed by an acoustic lens of prior art 1 (FIG. 12A), the sound pressure distribution of an ultrasonic beam formed by an acoustic lens of prior art 2 (FIG. 12B), and the sound pressure distribution of an ultrasonic beam formed by an acoustic lens according to this embodiment (FIG. 12C). [Figure 13] FIG. 13A shows an ultrasound image captured using an acoustic lens according to conventional technique 1; FIG. 13B shows an ultrasound image captured using an acoustic lens according to conventional technique 2; and FIG. 13C shows an ultrasound image captured using an acoustic lens according to one embodiment of the present invention. [Figure 14] FIG. 1 is a diagram showing the shape of an acoustic lens according to a first embodiment; [Figure 15] FIG. 13 is a diagram showing the shape of an acoustic lens according to Example 2. [Figure 16] FIG. 13 is a diagram showing the shape of an acoustic lens according to Example 3. [Figure 17] FIG. 13 is a diagram showing the shape of an acoustic lens according to Example 4. [Figure 18] FIG. 13 is a diagram showing the shape of an acoustic lens according to Example 5. [Figure 19] FIG. 13 is a diagram showing the shape of an acoustic lens according to Example 6. [Figure 20] FIG. 13 is a diagram showing the shape of an acoustic lens according to Example 7. [Figure 21] FIG. 1 shows the results of evaluating the performance of the acoustic lens according to the present invention, the acoustic lens according to Prior Art 1, and the acoustic lens according to Prior Art 2 from three perspectives: "CTR (Clutter Energy to Total Energy Ratio) (dB)," "Penetration (cm)," and "Gel bubble accumulation." [Figure 22] FIG. 1 is a diagram showing the shape of an acoustic lens according to Comparative Example 1. [Figure 23] FIG. 13 is a diagram showing the shape of an acoustic lens according to Comparative Example 2. [Figure 24] FIG. 13 is a diagram showing the shape of an acoustic lens according to Comparative Example 3. [Diagram 25] FIG. 13 is a diagram showing the shape of an acoustic lens according to Comparative Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functions are denoted by the same reference numerals, and redundant description will be omitted.

[0016] [Overall configuration of ultrasound diagnostic equipment] Fig. 1 is a diagram showing an example of the external appearance of an ultrasound diagnostic device 1. Fig. 2 is a diagram showing an example of the configuration of an ultrasound probe 20. Fig. 2A is a plan view of the ultrasound probe 20, and Fig. 2B is a perspective view of the ultrasound probe 20.

[0017] FIG. 3 is a block diagram showing an example of the configuration of the main parts of a control system of the ultrasonic diagnostic apparatus 1. As shown in FIG.

[0018] 1, the ultrasonic diagnostic device 1 includes an ultrasonic diagnostic device main body 10 and an ultrasonic probe 20. The ultrasonic diagnostic device main body 10 and the ultrasonic probe 20 are connected via a cable 30.

[0019] The ultrasound diagnostic device 1 is used for visualizing the shape, properties, or dynamics inside a subject as an ultrasound image and performing image diagnosis. The ultrasound diagnostic device 1 is used, for example, in a puncture procedure in which a puncture needle is inserted toward a target (e.g., a sample collection target such as a muscle, tendon, nerve bundle, or tumor of a subject) so that a user can confirm the position of a puncture needle or the position of a puncture site (target).

[0020] The ultrasound probe 20 transmits ultrasound to the subject, receives ultrasound echoes reflected by the subject, converts them into reception signals, and transmits them to the ultrasound diagnostic device body 10. The ultrasound probe 20 can be any electronic scanning type probe such as a convex probe, a linear probe, or a sector probe, or a mechanical scanning type probe such as a mechanical sector probe.

[0021] The ultrasonic probe 20 has, in order from the ultrasonic wave emitting surface side, an acoustic lens 21, an acoustic matching layer 22, a transducer array 23, and a backing material 24 (see FIG. 2A). Note that a protective layer may be further disposed on the surface (ultrasound emitting surface) side of the acoustic lens 21.

[0022] The acoustic lens 21 focuses ultrasonic waves in the slice direction (a direction perpendicular to the scan direction in which the multiple transducers are arranged) to form an ultrasonic beam. The acoustic lens 21 according to this embodiment is made of a material (e.g., silicone resin) whose sound speed is slower than that of a living body, and has a semi-cylindrical shape (i.e., a roughly semi-cylindrical shape) with a raised central portion in the slice direction. However, the shape of the ultrasonic radiation surface of the acoustic lens 21 according to this embodiment is not a uniform spherical shape, but has a shape that combines a spherical shape and an aspherical shape so as to obtain desired lens characteristics (described later with reference to FIG. 8).

[0023] The acoustic matching layer 22 is an intermediate material for allowing ultrasonic waves to efficiently enter the subject, and matches the acoustic impedance of the piezoelectric transducer 23a with that of the subject.

[0024] The transducer array 23 is not separated in the slice direction and is composed of a plurality of rectangular piezoelectric transducers 23a arranged in a single row along the scan direction. That is, the ultrasonic probe 20 is a so-called single row probe (also called a 1D type probe).

[0025] The backing material 24 attenuates unnecessary vibrations generated in the transducer array 23 .

[0026] The ultrasonic probe 20 can obtain a beam profile of ultrasonic waves focused in the slice direction (see FIG. 2B). Note that ultrasonic waves can also be focused in the scan direction by switching and driving a plurality of piezoelectric transducers 23a (a so-called electronic scan method).

[0027] The ultrasonic diagnostic apparatus main body 10 uses the received signal from the ultrasonic probe 20 to visualize the internal state of the subject as an ultrasonic image (B-mode image).

[0028] As shown in FIG. 3, the ultrasound diagnostic apparatus main body 10 includes an operation input unit 11, a transmitting unit 12, a receiving unit 13, a signal processing unit 14, an image processing unit 15, a display processing unit 16, a display unit 17, a control unit 18, and the like.

[0029] The transmitting unit 12, the receiving unit 13, the signal processing unit 14, the image processing unit 15 and the display processing unit 16 are composed of dedicated or general-purpose hardware (electronic circuits) corresponding to each process, such as a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), etc., and realize each function in cooperation with the control unit 18.

[0030] The operation input unit 11 receives, for example, a command to start a diagnosis or input of information on a subject. The operation input unit 11 includes, for example, an operation panel having a plurality of input switches, a keyboard, and a mouse. The operation input unit 11 may be configured as a touch panel provided integrally with the display unit 17.

[0031] The transmitting unit 12 generates a transmission signal (drive signal) in accordance with an instruction from the control unit 18, and outputs the signal to the ultrasonic probe 20. Although not shown, the transmitting unit 12 includes, for example, a clock generating circuit, a pulse generating circuit, a pulse width setting unit, and a delay circuit.

[0032] The clock generating circuit generates a clock signal that determines the transmission timing and transmission frequency of the pulse signal. The pulse generating circuit generates a bipolar rectangular wave pulse with a preset voltage amplitude at a predetermined period. The pulse width setting unit sets the pulse width of the rectangular wave pulse output from the pulse generating circuit. The rectangular wave pulse generated by the pulse generating circuit is separated into different wiring paths for each piezoelectric transducer 23a of the ultrasonic probe 20 before or after input to the pulse width setting unit. The delay circuit delays the generated rectangular wave pulse according to the transmission timing for each piezoelectric transducer 23a, and outputs it to the piezoelectric transducer 23a.

[0033] The receiving unit 13 receives a reception signal from the ultrasonic probe 20 in accordance with an instruction from the control unit 18, and outputs the reception signal to the image processing unit 15. Although not shown in the figure, the receiving unit 13 includes, for example, an amplifier, an A / D conversion circuit, and a phasing addition circuit.

[0034] The amplifier amplifies the reception signals corresponding to the ultrasonic waves received by each piezoelectric transducer 23a of the ultrasonic probe 20 at a preset amplification factor. The A / D conversion circuit converts the amplified reception signals into digital data at a predetermined sampling frequency. The phasing addition circuit adjusts the time phase by providing a delay time for each wiring path corresponding to the piezoelectric transducer 23a to the A / D converted reception signals, and adds them together (phasing addition).

[0035] The signal processing unit 14 performs harmonic extraction processing and the like as necessary from the sound ray data input from the receiving unit 13, and then performs detection (envelope detection) to obtain a signal, and also performs logarithmic amplification, filtering (e.g., low-pass filtering, smoothing, etc.), emphasis processing, etc. as necessary.

[0036] The image processing unit 15 generates a diagnostic image based on the received signal acquired from the signal processing unit 14. The image processing unit 15 generates, as one of the diagnostic images, for example, a tomographic image that represents a two-dimensional structure in a cross section including the transmission direction of the signal (depth direction of the subject) and the scanning direction of the ultrasound, using a luminance signal according to the signal intensity of the received signal.

[0037] The image processing unit 15 may have a storage unit (e.g., DRAM) that stores the diagnostic image data in units of frames for a predetermined number of recent frames, and a processing unit that identifies the position of the puncture needle from the diagnostic image data and colors the identified puncture needle. For a method of identifying the position of the puncture needle, see, for example, the methods disclosed in Japanese Patent Application Laid-Open No. 2014-212922 and Japanese Patent Application Laid-Open No. 2020-010753, which are prior applications of the applicant of the present application.

[0038] The display processing unit 16, in accordance with instructions from the control unit 18, converts the data of the tomographic image generated in the image processing unit 15 into a display signal corresponding to the display unit 17, and outputs it as image data for display.

[0039] The display unit 17 is configured, for example, with a liquid crystal display, an organic EL display, a CRT display, etc. The display unit 17 displays the display image data acquired from the display processing unit 16 according to an instruction from the control unit .

[0040] The control unit 18 performs overall control of the ultrasound diagnostic apparatus 1 by controlling the operation input unit 11, the transmission unit 12, the reception unit 13, the signal processing unit 14, the image processing unit 15, the display processing unit 16, and the display unit 17 according to their respective functions.

[0041] The control unit 18 has a CPU (Central Processing Unit) 181 as an arithmetic / control device, a ROM (Read Only Memory) 182 as a main storage device, and a RAM (Random Access Memory) 183. A basic program and basic setting data are stored in the ROM 182. The CPU 181 reads out a program corresponding to the processing contents from the ROM 182, loads it in the RAM 183, and executes the loaded program to centrally control the operations of each functional block (the transmission unit 12, the reception unit 13, the signal processing unit 14, the image processing unit 15, the display processing unit 16, and the display unit 17) of the ultrasound diagnostic device main body 10.

[0042] [Configuration of acoustic lens] Next, an example of the configuration of the acoustic lens 21 will be described.

[0043] First, with reference to FIGS. 4 to 8, the circumstances by which the inventors of the present application arrived at the configuration of the acoustic lens 21 of the ultrasonic probe 20 of the present invention will be described.

[0044] Conventionally, an acoustic lens having a spherical ultrasonic radiation surface has been adopted for the ultrasonic probe 20 (hereinafter referred to as "acoustic lens 21X according to prior art 1"). However, since the acoustic lens 21X according to prior art 1 focuses ultrasonic waves radiated from each position within the ultrasonic radiation surface of the acoustic lens 21X to one focal point, when an ultrasonic beam is formed using such acoustic lens 21X, the signal-to-noise ratio of ultrasonic echoes from objects (e.g., a puncture needle, a target, etc.) present at a depth position away from the focal depth position is significantly deteriorated.

[0045] Therefore, the inventors of the present application designed the ultrasound emitting surface of the acoustic lens of the ultrasonic probe 20 to be divided along the slice direction into an inner region 21Ya located in the center of the lens and an outer region 21Yb located outside the inner region 21Ya, and investigated an acoustic lens having a shape in which the inner region 21Ya forms a focal point in a shallow portion and the outer region 21Yb forms a focal point in a deep portion (hereinafter referred to as "acoustic lens 21Y relating to prior art 2").

[0046] Fig. 4 is a diagram showing an example of the shape of an acoustic lens 21X according to Prior Art 1. Fig. 5 is a diagram showing an example of the shape of an acoustic lens 21Y according to Prior Art 2. Fig. 6 is a diagram explaining the design concept of the acoustic lens 21Y according to Prior Art 2.

[0047] In Figures 4 and 5, the upper figures (Figures 4A and 5A) show schematic shapes of acoustic lenses 21X and 21Y, and the graphs in the lower figures (Figures 4B and 5B) show details of the shapes of the ultrasound emitting surfaces of acoustic lenses 21X and 21Y.

[0048] The upper graphs in Fig. 4B and Fig. 5B show the coordinates of each position in the plane of the ultrasound emitting surface of the acoustic lenses 21X and 21Y in a two-dimensional coordinate system with the slice direction as the x-axis (the lens center is set as the zero point, and the x-axis plus direction corresponds to the lens outer direction) and the ultrasound emitting direction as the y-axis (hereinafter, also referred to as the "shape profile of the ultrasound emitting surface of the acoustic lens"). The lower graphs in Fig. 4B and Fig. 5B show the tangent angle (as shown by θ in Fig. 4B and Fig. 5B, when a tangent is drawn to each position of the shape profile of the ultrasound emitting surface of the acoustic lenses 21X and 21Y, the inclination angle of the tangent to the x-axis. The same applies below) of each position in the plane of the ultrasound emitting surface of the acoustic lenses 21X and 21Y in a two-dimensional coordinate system with the slice direction as the x-axis and the value of the tangent angle as the y-axis (hereinafter, also referred to as the "tangent angle profile of the ultrasound emitting surface of the acoustic lens").

[0049] In addition, when the ultrasonic emitting surface is spherical, the tangent angle profile has a constant value of the tangent angle gradient (= dθ / dx) toward the x-axis positive direction, as shown in Fig. 4B. Therefore, in the tangent angle profile, when the tangent angle gradient (= dθ / dx) increases toward the x-axis positive direction, the ultrasonic emitting surface has a shape in which the curvature gradually increases from the lens center toward the lens outside, and when the tangent angle gradient (= dθ / dx) decreases toward the x-axis positive direction, the ultrasonic emitting surface has a shape in which the curvature gradually decreases from the lens center toward the lens outside.

[0050] As shown in FIG. 4, the acoustic lens 21X according to the conventional technique 1 has a lens portion 21Xa having a spherical shape. The edge region 21Xe shown in FIG. 4 is a flat surface at the outermost end of the acoustic lens 21X provided for the purpose of improving the contact state between the living body and the acoustic lens 21X. The edge region 21Xe is located at the outermost end or outside of the piezoelectric transducer 23a and does not have a significant effect on the beam characteristics of the ultrasonic beam formed by the acoustic lens 21X, so it will not be mentioned in the following. In other words, the edge region 21Xe may be omitted when configuring the acoustic lens 21X. The same applies to the edge region 21Ye shown in FIG. 5 and the edge region 21d shown in FIG. 8.

[0051] 5, the acoustic lens 21Y according to the conventional technique 2 is set so that the inner region 21Ya has a spherical shape and the outer region 21Yb has an inclined shape. That is, the ultrasonic radiation surface of the acoustic lens 21Y according to the conventional technique 2 has different curvatures in the inner region 21Ya and the outer region 21Yb, and the curvature of the inner region 21Ya is greater than the curvature of the outer region 21Yb. Therefore, in the acoustic lens 21Y according to the conventional technique 2, the focusing of ultrasonic waves in the inner region 21Ya is lower than the focusing of ultrasonic waves in the outer region 21Yb.

[0052] With this configuration, the acoustic lens 21Y according to Prior Art 2 focuses ultrasonic waves emitted from the inner region 21Ya at a shallow position (see the hatched area in the left diagram of FIG. 6), and focuses ultrasonic waves emitted from the outer region 21Yb at a deep position (see the hatched area in the center diagram of FIG. 6). That is, in the acoustic lens 21Y according to Prior Art 2, ultrasonic waves emitted from the inner region 21Ya support the central axis sound pressure (representing the sound pressure of the lens central axis in the slice direction of the acoustic lens 21Y; the same applies below) of the shallow part of the ultrasonic beam, and ultrasonic waves emitted from the outer region 21Yb support the central axis sound pressure of the deep part of the ultrasonic beam.

[0053] This makes it possible to make the ultrasonic beam formed by the acoustic lens 21Y of prior art 2 an ultrasonic beam that is focused over a wider range, from shallow to deep, than the ultrasonic beam formed by the acoustic lens 21X of prior art 1.

[0054] However, as a result of intensive research by the inventors of the present application, it has been found that in the ultrasonic beam formed using the acoustic lens 21Y according to the conventional technique 2, the ultrasonic waves emitted from the outer region 21Yb are actually superimposed on the ultrasonic waves emitted from the inner region 21Ya in the shallow part, forming a beam tail. In other words, the ultrasonic beam formed using the acoustic lens 21Y according to the conventional technique 2 has a beam width that is expanded in the slice direction in the shallow part. Such a beam tail is a factor that causes a decrease in spatial resolution in the shallow part of the ultrasonic image. It is presumed that this is due to the diffused component of the ultrasonic waves emitted from the outer region 21Yb.

[0055] FIG. 7 is a diagram showing an example of a beam tail generated in an ultrasonic beam formed by an acoustic lens 21Y according to the second prior art.

[0056] 7A and 7B show an example of an acoustic energy distribution related to imaging of a shallow portion of an ultrasonic beam formed by an acoustic lens 21X according to conventional technique 1, and Fig. 7C and Fig. 7D show an example of an acoustic energy distribution of a shallow portion of an ultrasonic beam formed by an acoustic lens 21Y according to conventional technique 2. In Fig. 7A to Fig. 7D, the S axis represents the slice direction, the T axis represents the scan direction, and the U axis represents the acoustic energy value of the ultrasonic beam (here, a value converted from the brightness information of the ultrasonic image into the acoustic energy value). Fig. 7E shows the depth positions at which the data in Fig. 7A to Fig. 7D was collected.

[0057] In particular, as can be seen by comparing FIG. 7C with FIG. 7A, in the ultrasonic beam formed by the acoustic lens 21Y according to the conventional technique 2, a beam skirt occurs in a shallow portion of the ultrasonic beam.

[0058] The acoustic lens 21 of the present invention has been designed in consideration of the above-mentioned problems of the acoustic lens 21X according to the prior art 1 and the acoustic lens 21Y according to the prior art 2.

[0059] Hereinafter, the configuration of an acoustic lens 21 according to one embodiment of the present invention will be described with reference to FIGS.

[0060] Fig. 8 is a diagram showing an example of the shape of the acoustic lens 21 according to this embodiment. In Fig. 8, similarly to Figs. 4 and 5, the upper diagram (Fig. 8A) shows a schematic diagram of the shape of the acoustic lens 21, and the graph in the lower diagram (Fig. 8B) shows the shape profile of the ultrasound emitting surface of the acoustic lens 21 and the tangent angle profile of the ultrasound emitting surface of the acoustic lens 21.

[0061] FIG. 9 is a diagram for explaining the design concept of the acoustic lens 21 according to this embodiment.

[0062] Fig. 10 is a diagram (lower diagram) showing a profile (hereinafter abbreviated as "depth of focus profile") indicating the depth of focus formed by the lens portion at each position within the ultrasound emitting surface of the acoustic lens 21 according to this embodiment. In order to explain the difference between the acoustic lens 21 according to this embodiment and the acoustic lens 21 according to the prior art, Fig. 10 also plots the depth of focus profile (solid line graph) of the acoustic lens 21 according to this embodiment, as well as the depth of focus profile (dotted line graph) of the acoustic lens 21X according to prior art 1 and the depth of focus profile (dashed dot line graph) of the acoustic lens 21Y according to prior art 2.

[0063] The upper diagram of Fig. 10 (Fig. 10A) shows the shape profile of the ultrasound emitting surface of the acoustic lenses 21, 21X, and 21Y, and the lower diagram of Fig. 10 (Fig. 10B) shows the focal depth profile of the acoustic lenses 21, 21X, and 21Y. The horizontal axis of the graph in Fig. 10B shows each position in the slice direction of the ultrasound emitting surface of the acoustic lenses 21, 21X, and 21Y in the x-coordinate system common to Fig. 10A, and the vertical axis of the graph in Fig. 10B shows the focal depth formed by the lens portion at each position. In either case, the tangent to the lens surface is horizontal at X=0 mm, and the focal depth is infinity (infinity), so the focal depth at 0 mm is not shown.

[0064] 11 is a schematic diagram showing the focal depth profile of the acoustic lens 21 according to this embodiment, superimposed on the shape profile of the acoustic lens 21. F1, F2, F3, and F4 correspond to the focal point formed by the lens portion located at a distance L1 from the lens center of the acoustic lens 21, the focal point formed by the lens portion located at a distance L2 from the lens center of the acoustic lens 21, the focal point formed by the lens portion located at a distance L3 from the lens center of the acoustic lens 21, and the focal point formed by the lens portion located at a distance L4 from the lens center of the acoustic lens 21, respectively.

[0065] The acoustic lens 21 according to this embodiment includes, on its ultrasound radiation surface, an inner region 21a located at the center of the lens along the slice direction, and an outer region 21b adjacent to the inner region 21a and located outside the lens of the inner region 21a (see FIG. 8). In the acoustic lens 21 according to this embodiment, the inner region 21a forms a focal point at a position corresponding to the deep part of the ultrasound beam (see the hatched region in the left diagram of FIG. 9), and the outer region 21b forms a focal point at a position corresponding to the shallow part of the ultrasound beam (see the hatched region in the center diagram of FIG. 9). That is, in the acoustic lens 21 according to this embodiment, the ultrasound radiated from the inner region 21a supports the central axis sound pressure of the deep part of the ultrasound beam, and the ultrasound radiated from the outer region 21b supports the central axis sound pressure of the shallow part of the ultrasound beam.

[0066] The acoustic lens 21 according to this embodiment has a semicylindrical shape with a raised central portion in the slice direction, and has a line-symmetric shape along the slice direction with the lens center as the axis of symmetry. That is, the outer regions 21b are disposed on both sides of the inner region 21a on one side and the other side of the lens outer side along the slice direction, sandwiching the inner region 21a therebetween, and are formed to focus at a depth position (see T2 in FIG. 11) shallower than the focal depth of the inner region 21a on the lens central axis by the outer regions 21b on both sides of the inner region 21a on one side and the other side of the lens outer side.

[0067] The inner region 21a of the acoustic lens 21 has, for example, a spherical shape, and the outer region 21b of the acoustic lens 21 has, for example, an aspheric shape in which the gradient (=dθ / dx) of the tangent angle at each position in the plane of the ultrasonic wave emitting surface gradually increases from the lens center side toward the lens outside (see FIG. 8). That is, when the outer region 21b of the acoustic lens 21 has a curved shape, the curvature at each position in the plane of the ultrasonic wave emitting surface gradually increases from the lens center side toward the lens outside. Here, "gradually increasing" means monotonically and continuously increasing. As shown in FIG. 8, even at the connection position between the inner region 21a and the outer region 21b of the acoustic lens 21, the gradient (=dθ / dx) of the tangent angle of the ultrasonic wave emitting surface (i.e., the curvature) increases continuously from the lens center side toward the lens outside without any discontinuity.

[0068] In addition, in the acoustic lens 21 shown in FIG. 8, the inclination (= dθ / dx) of the tangent angle at each position within the ultrasonic radiation surface of the outer region 21b is not fixed and changes continuously (i.e., does not take a constant value) from the end on the central side of the lens to the end on the outer side of the lens.

[0069] In the acoustic lens 21 according to this embodiment, a connection region 21c is formed in which the inclination (=dθ / dx) of the tangent angle of the ultrasonic radiation surface gradually decreases from the lens center toward the lens outside, so that a region where the curvature changes suddenly is not formed between the outer region 21b and the edge region 21d at the outermost end of the acoustic lens 21 (see FIG. 8). However, like the edge region 21d, the connection region 21c is located at the end or outside of the piezoelectric transducer 23a, and does not have a significant effect on the beam characteristics of the ultrasonic beam formed by the acoustic lens 21. Therefore, in other words, the connection region 21c may be omitted in constructing the acoustic lens 21, like the edge region 21d.

[0070] In the acoustic lens 21 according to this embodiment, by adopting such a shape, the focal point formed by the outer region 21b is located at a shallower position than the focal point formed by the inner region 21a. Moreover, in the acoustic lens 21 according to this embodiment, the depth of the focal point formed by the lens portions at each position of the inner region 21a and the outer region 21b (i.e., focal depth profile) becomes continuously shallower from the lens center side toward the outer side of the lens (see FIGS. 10B and 11).

[0071] In the focal depth profile of this embodiment shown in FIG. 10B, the focal depth suddenly becomes deeper from a position 1.5 mm or more away from the lens center on the x-axis to the outside of the lens. This is because this region (region 1.5 mm or more away) corresponds to the concave connection region 21c and the flat edge region 21d.

[0072] 9, the design concept of the acoustic lens 21 according to this embodiment will be described in detail. In the acoustic lens 21 according to this embodiment, compared to the acoustic lens 21Y according to prior art 2, the curvature of the inner region 21a is made smaller and the inner region 21a has a smaller opening, thereby making the focal length of the inner region 21a longer (i.e., increasing the F-number), widening the narrow portion (position T1a in FIG. 9) (corresponding to the focal position of the inner region 21a) of the ultrasound emitted from the inner region 21a, and narrowing the deep portion (position T1b in FIG. 9) (corresponding to a position deeper than the focal position of the inner region 21a) of the ultrasound emitted from the inner region 21a.

[0073] In the acoustic lens 21 according to this embodiment, the focal point formed by the outer region 21b is located at a position shallower than the focal point formed by the inner region 21a (position T2 in FIG. 9), and the central axial sound pressure of the shallow part of the ultrasonic beam, which decreases due to the long focal length of the inner region 21a, is supported by the ultrasonic waves emitted from the outer region 21b. In addition, in the acoustic lens 21 according to this embodiment, the depth of the focal point formed by the lens parts at each position of the inner region 21a and the outer region 21b draws a focal depth profile that becomes continuously shallower from the lens center side toward the outside of the lens.

[0074] The acoustic lens 21 according to the present embodiment, by adopting such a configuration, realizes an ultrasonic beam that is uniformly and thinly focused over a wide range from shallow to deep. In particular, in the acoustic lens 21 according to the present embodiment, the end of the outer region 21b in the lens outer direction becomes the shallowest focal position, so that the occurrence of beam tailing in the shallow part of the ultrasonic beam is suppressed. Therefore, according to the acoustic lens 21 according to the present embodiment, it is possible to realize an ultrasonic beam that is uniformly and thinly focused over a wider range than the acoustic lens 21Y according to the conventional technique 2, and as a result, it is possible to expand the depth of field and suppress the spread of the beam tail, thereby improving the spatial resolution.

[0075] Furthermore, in the acoustic lens 21 according to this embodiment, it is possible to reduce the sound pressure peak of the central axis sound pressure, which leads to a measure against the MI (Mechanical Index) limit (an output limit stipulated in consideration of the effect of ultrasonic energy on living organisms, and in practical use, the MI value calculated based on the sound pressure peak of the central axis sound pressure, etc., must be equal to or less than a predetermined value). In other words, in the acoustic lens 21 according to this embodiment, it is possible to transmit a high-output ultrasonic beam.

[0076] Next, referring to Figures 12 and 13, an example of the sound pressure distribution of an ultrasonic beam formed using the acoustic lens 21 of this embodiment and an example of an ultrasonic image captured using the acoustic lens 21 of this embodiment are shown.

[0077] 12A and 12B are diagrams showing the sound pressure distribution of an ultrasonic beam formed by an acoustic lens 21X of conventional technology 1 (FIG. 12A), the sound pressure distribution of an ultrasonic beam formed by an acoustic lens 21Y of conventional technology 2 (FIG. 12B), and the sound pressure distribution of an ultrasonic beam formed by an acoustic lens 21 according to this embodiment (FIG. 12C). The sound pressure distributions of the ultrasonic beams in FIGS. 12A, 12B, and 12C were calculated by simulation, and the simulations were performed under conditions in which the configuration was the same except for the acoustic lens 21. Note that in FIGS. 12A, 12B, and 12C, the darker the area, the higher the sound pressure.

[0078] 13A shows an ultrasonic image captured using an acoustic lens 21X according to conventional technique 1, FIG. 13B shows an ultrasonic image captured using an acoustic lens 21Y according to conventional technique 2, and FIG. 13C shows an ultrasonic image captured using an acoustic lens 21 according to this embodiment. Note that the ultrasonic images in FIG. 13A, FIG. 13B, and FIG. 13C are ultrasonic images generated when capturing an ultrasonic diagnostic device evaluation phantom (here, a spherical cyst phantom: Gammex 408 LE).

[0079] From FIG. 12A, it can be seen that in the sound pressure distribution of the ultrasonic beam transmitted using the acoustic lens 21 of prior art 1, only the sound pressure at the depth position corresponding to the focus of the acoustic lens 21 is locally high and narrow, the beam width of the deep part of the ultrasonic beam is diffused, and the sound pressure at the center is also reduced.

[0080] 12B, it can be seen that the sound pressure distribution of the ultrasonic beam transmitted using the acoustic lens 21 of the conventional technology 2 is uniform and narrowly focused over a certain region from the shallow part of the ultrasonic beam to the deep part of the ultrasonic beam, compared to the sound pressure distribution of the ultrasonic beam transmitted using the acoustic lens 21 of the conventional technology 1. This is because the acoustic lens 21 of the conventional technology 2 is configured to increase the sound pressure of the shallow part of the ultrasonic beam in the inner region 21a and increase the sound pressure of the deep part of the ultrasonic beam in the outer region 21b. However, it can be seen that in the sound pressure distribution of the ultrasonic beam in FIG. 12B, a part of the ultrasonic beam transmitted from the outer region 21b diffuses and spreads outward in the shallow part of the ultrasonic beam, causing beam tailing and widening of the beam width.

[0081] 12C, the sound pressure distribution of the ultrasonic beam transmitted using the acoustic lens 21 according to the present embodiment is more uniform and narrowly focused over a wide range from the shallow part of the ultrasonic beam to the deep part of the ultrasonic beam, compared to the sound pressure distribution of the ultrasonic beam transmitted using the acoustic lens 21 of the conventional technique 2. This is because the beam tailing that occurs in the ultrasonic beam transmitted using the acoustic lens 21 of the conventional technique 2 is suppressed in the ultrasonic beam transmitted using the acoustic lens 21 of the present embodiment. In addition, FIG. 12C shows that the acoustic lens 21 according to the present embodiment more effectively disperses the focal point formed by the acoustic lens 21 in the depth direction, and the central axis sound pressure of the ultrasonic beam transmitted using the acoustic lens 21 according to the present embodiment is more uniform from the shallow part to the deep part than the ultrasonic beam transmitted using the acoustic lens 21 of the conventional technique 2.

[0082] 13A and 13B, the ultrasound image captured using the acoustic lens 21Y according to conventional technique 2 is a clearer image in a deeper area than the ultrasound image captured using the acoustic lens 21X according to conventional technique 1. On the other hand, the ultrasound image captured using the acoustic lens 21Y according to conventional technique 2 is a less clear image in a shallower area than the ultrasound image captured using the acoustic lens 21X according to conventional technique 1.

[0083] In this regard, as can be seen by comparing Fig. 13C with Fig. 13A and Fig. 13B, the ultrasonic image captured using the acoustic lens 21 according to this embodiment is a clear image both at the shallow part and at the deep part. In other words, it can be seen that by using the acoustic lens 21 according to this embodiment, it is possible to expand the depth of field and improve the spatial resolution compared to the case where the acoustic lenses 21X and 21Y according to the conventional techniques 1 and 2 are used.

[0084] Here, a more preferred embodiment of the acoustic lens 21 according to this embodiment will be described.

[0085] The shape of the acoustic lens 21 according to this embodiment can be defined by, for example, the minimum F-number, the F-number ratio, the focal depth profile, and the shape of the connection region 21c.

[0086] Here, the "minimum F-number" is a value defined by the minimum value among the F-numbers at each position of the acoustic lens 21. For example, if the distance from the lens center is 1.8 mm and the focal length at that position is 18.4 mm, then the F-number at that position is 18.4 / (1.8*2)=5.1, and if this F-number is the smallest among all positions, then the minimum F-number is 5.1. Also, the "F-number ratio" is a value defined by the value obtained by dividing the F-number near the lens center of the acoustic lens by the minimum F-number (center-equivalent F-number / minimum F-number) (where the center-equivalent F-number is the F-number calculated from the center-equivalent focal length and the width of the entire ultrasonic radiation surface).

[0087] The minimum F-number of the acoustic lens 21 is preferably between 5 and 7. If the minimum F-number is smaller than 5, the visualization of shallow areas is improved, but the inclination angle of the ultrasonic beam emitted from the lens portion (piezoelectric transducer 23a) at the position of the minimum F-number becomes large, the sound pressure in the shallow area becomes high, and the MI value increases. In addition, the ultrasonic beam spreads beyond the focal point, so the visualization of deep areas is reduced. On the other hand, if the minimum F-number is larger than 7, the influence of diffusion becomes greater than the focusing by the ultrasonic beam, which also reduces the visualization of deep areas.

[0088] The F-number ratio of the acoustic lens 21 is preferably in the range of 2.5 to 3.5 when the minimum F-number range is in the range of 5 to 7. If the F-number ratio is smaller than 2.5, the change in focus within the lens becomes small, narrowing the convergence range of the ultrasonic beam, which leads to an increase in the MI value due to the concentration of sound pressure, and as a result, the transmission voltage becomes more likely to be restricted. On the other hand, if the F-number ratio is larger than 3.5, the convergence of the ultrasonic beam emitted from the center is insufficient, and it spreads due to diffusion in the deep area, resulting in a decrease in the visualization of the deep area.

[0089] It is preferable that the focal depth profile of the inner region 21a and the outer region 21b of the acoustic lens 21 changes continuously without discontinuities from the lens center of the inner region 21a to the lens outer edge of the outer region 21b. By eliminating discontinuities, valleys where bubbles in the ultrasonic jelly are likely to accumulate are not formed in the outer shape of the acoustic lens 21, so that deterioration of image quality caused by bubbles in the ultrasonic jelly can be suppressed. Here, a state without discontinuities means a state in which there is no region in the focal depth profile (see FIG. 10B) where the change in focal depth per 0.1 mm in the positive x-axis direction is 10 mm or more. In the acoustic lens 21 according to this embodiment, there is a risk of a valley being formed in the connection region 21c, but as described above, the connection region 21c is located at the end or outside of the piezoelectric transducer 23a and does not have a significant effect on the beam characteristics of the ultrasonic beam formed by the acoustic lens 21, so the formation of a valley in this region is not a problem.

[0090] Moreover, it is preferable that the focal depth profile of the outer region 21b of the acoustic lens 21 is continuously variable and not fixed from the end of the outer region 21b on the lens center side to the end of the outer region 21b on the lens outer side. This makes it possible to form an ultrasonic beam that is uniformly and thinly focused over a wide range from shallow to deep, and also makes it possible to reduce the sound pressure peak of the central axis sound pressure. Note that the state of being continuously variable and not fixed here means that there is no region in the focal depth profile (see FIG. 10B) where the amount of change in focal depth per 0.1 mm in the positive x-axis direction is less than 1 mm.

[0091] The shape of the connection region 21c of the acoustic lens 21 is not particularly limited and can take various shapes such as a concave curve, a convex curve, a straight line, etc., but a straight line is preferable when the lens is provided in a manufacturing process in which the lens is attached to a prefabricated transducer. In the manufacturing process in which the lens is attached, the lens shape needs to be made larger in consideration of the fact that the attachment may be misaligned to a certain extent, but if the connection region 21c is a straight line, it becomes easier to ensure a lens width that can cover the misalignment by stretching this straight line shape as necessary. However, this does not apply to the manufacturing process in which the lens member is attached and then shaped.

[0092] [Example] Next, various shapes of the acoustic lens 21 created based on the design concept of the acoustic lens 21 according to the present invention will be shown with reference to FIGS.

[0093] 14A is a diagram showing a shape profile of acoustic lens 21 according to Example 1, and Fig. 14B is a diagram showing a focal depth profile of acoustic lens 21 according to Example 1. Acoustic lens 21 according to Example 1 is an acoustic lens 21 fabricated based on the design concept of acoustic lens 21 according to the present invention, with the center vicinity focal length (mm) set to 69.0 mm, the center vicinity equivalent F-number set to 17.2, the shortest focal length (mm) set to 18.4 mm, the minimum F-number set to 5.1, and the F-number ratio set to 3.4.

[0094] Fig. 15A is a diagram showing a shape profile of an acoustic lens 21 according to Example 2, and Fig. 15B is a diagram showing a focal depth profile of the acoustic lens 21 according to Example 1. The acoustic lens 21 according to Example 2 is an acoustic lens 21 fabricated based on the design concept of the acoustic lens 21 according to the present invention, with the center vicinity focal length (mm) set to 69.0 mm, the center vicinity equivalent F-number set to 17.2, the shortest focal length (mm) set to 18.4 mm, the minimum F-number set to 5.1, and the F-number ratio set to 3.4.

[0095] Fig. 16A is a diagram showing a shape profile of an acoustic lens 21 according to Example 3, and Fig. 16B is a diagram showing a focal depth profile of the acoustic lens 21 according to Example 1. The acoustic lens 21 according to Example 3 is an acoustic lens 21 fabricated based on the design concept of the acoustic lens 21 according to the present invention, with the center vicinity focal length (mm) set to 69.0 mm, the center vicinity equivalent F-number set to 17.2, the shortest focal length (mm) set to 29.5 mm, the minimum F-number set to 8.3, and the F-number ratio set to 2.1.

[0096] Fig. 17A is a diagram showing a shape profile of an acoustic lens 21 according to Example 4, and Fig. 17B is a diagram showing a focal depth profile of the acoustic lens 21 according to Example 1. The acoustic lens 21 according to Example 4 is an acoustic lens 21 fabricated based on the design concept of the acoustic lens 21 according to the present invention, with the center vicinity focal length (mm) set to 69.0 mm, the center vicinity equivalent F-number set to 17.2, the shortest focal length (mm) set to 13.4 mm, the minimum F-number set to 3.7, and the F-number ratio set to 4.6.

[0097] Fig. 18A is a diagram showing a shape profile of an acoustic lens 21 according to Example 5, and Fig. 18B is a diagram showing a focal depth profile of the acoustic lens 21 according to Example 1. The acoustic lens 21 according to Example 5 is an acoustic lens 21 fabricated based on the design concept of the acoustic lens 21 according to the present invention, with the center vicinity focal length (mm) set to 47.7 mm, the center vicinity equivalent F-number set to 11.9, the shortest focal length (mm) set to 18.4 mm, the minimum F-number set to 5.1, and the F-number ratio set to 2.3.

[0098] Fig. 19A is a diagram showing a shape profile of an acoustic lens 21 according to Example 6, and Fig. 19B is a diagram showing a focal depth profile of the acoustic lens 21 according to Example 1. The acoustic lens 21 according to Example 6 is an acoustic lens 21 fabricated based on the design concept of the acoustic lens 21 according to the present invention, with the center vicinity focal length (mm) set to 90.5 mm, the center vicinity equivalent F-number set to 22.6, the shortest focal length (mm) set to 18.4 mm, the minimum F-number set to 5.1, and the F-number ratio set to 4.4.

[0099] Fig. 20A is a diagram showing a shape profile of an acoustic lens 21 according to Example 7, and Fig. 20B is a diagram showing a focal depth profile of the acoustic lens 21 according to Example 1. The acoustic lens 21 according to Example 7 is an acoustic lens 21 fabricated based on the design concept of the acoustic lens 21 according to the present invention, with the center vicinity focal length (mm) set to 61.2 mm, the center vicinity equivalent F-number set to 15.3, the shortest focal length (mm) set to 27.4 mm, the minimum F-number set to 8.4, and the F-number ratio set to 1.8.

[0100] In the acoustic lenses 21 according to Examples 1 to 6 (FIGS. 14 to 19), the connection region 21c has a linear shape, while in the acoustic lens 21 according to Example 7 (FIG. 20), the connection region 21c has a concave shape.

[0101] [Verification experiment] Next, experimental results of a verification experiment in which the performance of the acoustic lens 21 according to the present invention was evaluated will be shown. The verification experiment was carried out using a Gammex 408 LE spherical cyst phantom.

[0102] FIG. 21 is a diagram showing the results of evaluating the performance of an acoustic lens 21 according to the present invention, an acoustic lens 21X according to prior art 1, and an acoustic lens 21Y according to prior art 2 from three perspectives: CTR (Clutter Energy to Total Energy Ratio) (dB), Penetration (cm), and Gel air bubble accumulation.

[0103] Here, the acoustic lens 21 according to the present invention was the acoustic lens according to Example 2 shown in Fig. 15. As the acoustic lens 21X according to Prior Art 1, the acoustic lens according to Comparative Example 1 shown in Fig. 22 and the acoustic lens according to Comparative Example 2 shown in Fig. 23 were used. As the acoustic lens 21Y according to Prior Art 2, the acoustic lens according to Comparative Example 3 shown in Fig. 24 and the acoustic lens according to Comparative Example 4 shown in Fig. 25 were used. The design parameters of the acoustic lens according to the present invention and the acoustic lenses according to Comparative Examples 1 to 4 are shown in Fig. 21.

[0104] "CTR" is an index of visualization of anechoic areas, and is an index that indicates the depth of field and the spatial resolution at each depth position. For 256-level images, CTR can be calculated using the following formula. The higher the CTR value (dB), the better the visualization of anechoic areas. On the other hand, if the brightness of the entire anechoic area increases, or if the boundary extends into the anechoic area and the apparent size becomes smaller, the CTR value decreases.

number

[0105] "Penetration (cm)" is an index that indicates the depth of field. In this study, two images were taken at the same location on a Gammex 408 LE spherical cyst phantom in a state where there was no anechoic target and all background areas were depicted. The depth at which the image correlation coefficient of the two images was 0.5 or more was used as the evaluation value for penetration.

[0106] "Gel bubble accumulation" is an evaluation item related to the presence or absence of image defects when bubbles are added to an ultrasonic jelly using a whisk and a Gammex 408 LE spherical cyst phantom is observed using this jelly. Note that in addition to cases where no gel bubble accumulation occurred, cases where image defects due to bubbles could be eliminated simply by pressing the acoustic lens against the cyst phantom were also evaluated as "absent" for gel bubble accumulation.

[0107] 21, the acoustic lens according to the present invention has a higher CTR value from shallow to deep compared to the acoustic lenses according to Comparative Examples 1 to 4. Furthermore, the acoustic lens according to the present invention has a higher penetration (cm) compared to the acoustic lenses according to Comparative Examples 1 to 4. Furthermore, gel air bubbles were trapped in the acoustic lens according to Comparative Example 3, but no gel air bubbles were trapped in the acoustic lens according to the present invention.

[0108] [effect] As described above, the acoustic lens 21 of this embodiment has an ultrasound emission surface that includes a first region (corresponding to inner region 21a) located at the center of the lens and forming a focal point at a position corresponding to the deep part of the ultrasound beam, and a second region (corresponding to outer region 21b) located outside the lens of the first region and forming a focal point at a position corresponding to the shallow part of the ultrasound beam, and has a configuration in which the focal depth profile indicating the depth of the focal point formed by the lens portion at each position of the first region and the second region describes a profile that becomes continuously shallower from the lens center side toward the outside of the lens.

[0109] Therefore, the acoustic lens 21 according to this embodiment can generate an ultrasonic image having a wide depth of field and high spatial resolution. In addition, the acoustic lens 21 according to this embodiment can reduce the sound pressure peak of the central axial sound pressure, so that a high-output ultrasonic beam can be transmitted in ultrasonic inspection.

[0110] Furthermore, according to the acoustic lens 21 of this embodiment, unlike the acoustic lens 21Y of prior art 2, due to the design concept of the ultrasonic radiation surface, no valley-shaped portion is formed at the connection position between the inner region 21a and the outer region 21b, so it is possible to suppress the occurrence of image defects due to air bubbles accumulating in the ultrasonic jelly.

[0111] Incidentally, the acoustic lens 21 according to this embodiment makes it possible to obtain an ultrasonic probe 20 with excellent penetration and a uniform slice beam width from shallow to deep areas with an inexpensive single-row probe called 1D, without using multiple rows of transducers such as 1.25D, 1.5D, or 1.75D. Therefore, the acoustic lens 21 according to this embodiment basically provides a significant improvement effect when applied to a single-row ultrasonic probe 20, but the configuration of the acoustic lens 21 according to this embodiment may also be applied to the center row of a multiple-row transducer.

[0112] (Other embodiments) The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0113] For example, in the above embodiment, a convex lens type lens using a material (e.g., silicone resin) whose sound speed is slower than that of a living body was shown as an example of acoustic lens 21, but acoustic lens 21 according to the present invention can also be applied to a concave lens using a material (e.g., polymethylpentene resin) whose sound speed is faster than that of a living body.

[0114] In addition, in the above embodiment, as an example of acoustic lens 21, a mode in which the material forming acoustic lens 21 is the same within the ultrasonic radiation surface has been shown, but the acoustic lens 21 of the present invention may be formed from a material forming acoustic lens 21 that is made of different materials within the ultrasonic radiation surface (for example, materials with different ultrasonic refractive indices).

[0115] Although the specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above. [Industrial Applicability]

[0116] The acoustic lens according to the present disclosure makes it possible to generate ultrasound images with a wide depth of field and high spatial resolution. [Explanation of symbols]

[0117] 1. Ultrasound diagnostic equipment 10. Ultrasound diagnostic device body 11 Operation input section 12 Transmitter 13 Receiving section 14 Signal Processing Section 15 Image processing section 16 Display processing section 17 Display section 18 Control Unit 20 Ultrasonic probe 21 Acoustic Lens 21a Inner Zone (1st Zone) 21b Outer area (second area) 21c Connection Area 21d Edge Area 22 Acoustic matching layer 23 Transducer Array 24 Backing material

Claims

1. An acoustic lens that is applied to an ultrasonic probe and focuses ultrasonic waves transmitted from a plurality of piezoelectric transducers to form an ultrasonic beam, The ultrasonic emitting surface of the acoustic lens is a first region located in the center of the lens and forming a focal point at a position corresponding to a deep portion of the ultrasonic beam; and a second region located outside the first region and forming a focal point at a position corresponding to a shallow portion of the ultrasonic beam, a depth of focus formed by the lens portion at each position of the first region and the second region describes a profile that becomes continuously shallower from the center side of the lens toward the outside of the lens in a slice direction perpendicular to the direction in which the plurality of piezoelectric transducers are arranged; Acoustic lens.

2. In the profile, the depth of focus is continuously changed without being fixed from an end of the second region on the lens center side to an end of the second region on the lens outer side. The acoustic lens of claim 1 .

3. In the profile, the depth of focus varies continuously without discontinuities from the lens center in the first region to the outer edge of the lens in the second region. The acoustic lens according to claim 1 .

4. The first region has a spherical shape, The second region has an aspheric shape. The acoustic lens according to claim 1 .

5. The first region and the second region are adjacent regions along a slice direction of the ultrasound probe. The acoustic lens according to claim 1 .

6. A minimum F-number defined by the minimum value among the F-numbers of the lens portions at each position of the first region and the second region of the acoustic lens is a value within a range of 5 to 7. The acoustic lens according to claim 1 .

7. an F-number ratio defined by a value obtained by dividing an F-number near the lens center of the acoustic lens by the minimum F-number is a value within a range of 2.5 to 3.5; The acoustic lens according to claim 6 .

8. An ultrasonic probe comprising the acoustic lens according to any one of claims 1 to 7.

9. An ultrasonic diagnostic apparatus comprising the ultrasonic probe according to claim 8.

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