Ultrasound diagnostic equipment

Abstract

To acquire a good ultrasonic image when there is an acoustic shielding object.SOLUTION: A transmission opening of an ultrasonic probe 2L includes an inside first vibrator group and an outside second vibrator group. An ultrasonic diagnostic device outputs a first drive signal and a second drive signal to a plurality of vibrator groups for one sound ray, and receives a plurality of reception signals from the ultrasonic probe 2L and calculates them to generate ultrasonic image data. The first drive signal includes a third drive signal and a fourth drive signal. The second drive signal includes a fifth drive signal that is cancelled when added to the third drive signal, and a sixth drive signal in which a cancellation residue is generated when added to the fourth drive signal. The ultrasonic diagnostic device outputs the third and fifth drive signals to the first vibrator group to output an ultrasonic beam U1, and outputs the fourth and sixth drive signals to the second vibrator group to output an ultrasonic beam U2.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an ultrasound diagnostic apparatus. [Background technology]

[0002] Ultrasound diagnosis is a simple procedure in which an ultrasound probe is placed on the surface of a patient's body or inside a body cavity to obtain ultrasound images of the heart or fetus, and is highly safe and can be performed repeatedly. Ultrasound diagnostic devices used for such ultrasound diagnosis are known.

[0003] One known technology for displaying such ultrasound diagnostic images is tissue harmonic imaging (THI), which produces images with good contrast by imaging harmonic components (components not included in the transmitted ultrasound) generated within biological tissue.

[0004] Also known is an ultrasonic diagnostic device that outputs a first drive signal to a first group of transducers arranged inside a transmission aperture among multiple transducers of an ultrasonic probe, and outputs a second drive signal to a second group of transducers arranged outside the first group of transducers, and the frequency band of the frequency power spectrum of the transmission pulse of the first drive signal is broad and includes the frequency band of the frequency power spectrum of the transmission pulse of the second drive signal, and includes components higher than the frequency band of the frequency power spectrum of the transmission pulse of the second drive signal (see Patent Document 1). The ultrasonic diagnostic device of Patent Document 1 suppresses acoustic noise and improves penetration (depth of penetration). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-114195 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in THI, high sound pressure (ultrasonic sound pressure) is required to generate harmonics. High sound pressure can be achieved by transmitting and collecting strong ultrasonic waves. Here, referring to FIG. 25, the strength of the ultrasonic sound pressure when there is an acoustic barrier will be explained. FIG. 25 is a diagram showing the strength of the sound pressure of ultrasonic waves transmitted by the ultrasonic probe 2L.

[0007] Figure 25 shows the sound pressure intensity of transmitted ultrasound when an acoustic obstruction AS1 is present on the probe side of the transmission focus of transmitted ultrasound from an ultrasound probe 2L with a linear scanning method. In Figure 25, higher sound pressures in the transmitted ultrasound from ultrasound probe 2L are represented as white, and lower sound pressures are represented as black. Acoustic obstruction AS1 is an obstruction such as tissue with high reflection and high attenuation, and is represented by a shaded area in the figure. The presence of acoustic obstruction AS1 prevents the sound pressure of the transmitted ultrasound from increasing, reducing the amount of harmonic components generated. This creates a posterior shadow AS2 with low sound pressure that extends deep into the body. In particular, small diameter convex type probes, such as transvaginal probes, are susceptible to this effect because there is a limit to how much the aperture can be expanded in the azimuth direction even if the number of elements used for transmission is increased.

[0008] The ultrasound diagnostic device of Patent Document 1 is useful for suppressing acoustic noise and improving penetration, but it images harmonic components that are highly dependent on sound pressure, and has poor resistance to shadows when there is an acoustic obstruction.

[0009] An object of the present invention is to obtain a good ultrasound image in the presence of an acoustic obstruction. [Means for solving the problem]

[0010] In order to solve the above problem, the invention described in claim 1 is: An ultrasound diagnostic apparatus that generates ultrasound image data based on a reception signal obtained by an ultrasound probe that transmits transmission ultrasound to a subject and receives reception ultrasound from the subject, the ultrasonic probe has a transmission aperture formed by a plurality of transducers, the transmission aperture has a plurality of transducer groups including at least a first transducer group arranged inside the transmission aperture and a second transducer group arranged outside the first transducer group, The ultrasonic diagnostic device includes: a transmitter that generates a drive signal and outputs it to the plurality of transducer groups; a control unit that causes the transmission unit to output a plurality of drive signals including at least a first drive signal and a second drive signal to the plurality of transducer groups along one acoustic line; a receiving unit that receives a plurality of reception signals corresponding to the plurality of drive signals from the ultrasonic probe; an image generating unit that generates ultrasound image data by calculating the plurality of received signals, the first drive signal includes a third drive signal and a fourth drive signal; The second drive signal is a fifth drive signal that is canceled when added to the third drive signal, and a fourth drive signal that is canceled when added to the fourth drive signal. Linear component a sixth drive signal that generates a cancellation residual; the fourth drive signal and the sixth drive signal are asymmetric PI drive signals, the transmitted ultrasonic waves corresponding to the fourth drive signal and the sixth drive signal are low frequency; The control unit causes the transmitting unit to impart a time delay to the first drive signal and the second drive signal so that the transmitted ultrasonic waves are focused at the same focal point, and to output the third drive signal and the fifth drive signal to the first group of transducers, and to output the fourth drive signal and the sixth drive signal to the second group of transducers.

[0011] The invention described in claim 2 is the ultrasound diagnostic device described in claim 1, The image generator generates the ultrasound image data by adding up the received signals.

[0012] The invention described in claim 3 is the ultrasonic diagnostic apparatus described in claim 1 or 2, The first drive signal and the second drive signal have the same drive voltage.

[0013] The invention described in claim 4 is the ultrasound diagnostic apparatus according to any one of claims 1 to 3, The center frequency of the frequency power spectrum of the transmitted ultrasonic waves of the fourth drive signal and the sixth drive signal is smaller than the center frequency of the frequency power spectrum of the transmitted ultrasonic waves of the third drive signal and the fifth drive signal.

[0014] The invention described in claim 5 is the ultrasound diagnostic apparatus according to any one of claims 1 to 4, The bandwidth of the frequency power spectrum of the transmitted ultrasonic waves of the fourth drive signal and the sixth drive signal is smaller than the bandwidth of the frequency power spectrum of the transmitted ultrasonic waves of the third drive signal and the fifth drive signal.

[0015] The invention described in claim 6 is the ultrasound diagnostic apparatus according to any one of claims 1 to 5, In a frequency range higher than the center frequency of the ultrasonic probe, the signal strength of the frequency power spectrum of the transmitted ultrasonic waves of the fourth drive signal and the sixth drive signal is smaller than the signal strength of the frequency power spectrum of the transmitted ultrasonic waves of the third drive signal and the fifth drive signal.

[0016] The invention described in claim 7 is the ultrasonic diagnostic apparatus according to any one of claims 1 to 6. And, The above 4 The center frequencies of the frequency power spectra of the transmitted ultrasonic waves of the drive signal and the sixth drive signal are smaller than the center frequency of the cancellation residual component.

[0017] The invention described in claim 8 is the ultrasound diagnostic apparatus according to any one of claims 1 to 7, The above 4 The bandwidth of the frequency power spectrum of the transmitted ultrasonic waves of the drive signal and the sixth drive signal is smaller than the bandwidth of the cancellation residual component. [Effects of the Invention]

[0018] According to the present invention, a good ultrasound image can be obtained even when an acoustic obstruction is present. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is an external view of an ultrasonic diagnostic apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing the functional configuration of the ultrasound diagnostic apparatus. [Figure 3] FIG. 2 is a block diagram showing the functional configuration of a transmission unit. [Figure 4] 1A is a diagram showing the transmission intensity of transmitted ultrasonic waves for the channels of a transducer of an ultrasonic probe, and FIG. 1B is a diagram showing the degree of contribution of sound pressure increase in the direction of the transmission center of the transducer channel of the ultrasonic probe. [Figure 5] 3A and 3B are diagrams showing ultrasonic beams corresponding to a first group of transducers and a second group of transducers output from an ultrasonic probe. [Figure 6] 10A is a diagram showing an example of the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to a fourth drive signal, and FIG. 10B is a diagram showing an example of the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to a sixth drive signal. [Figure 7] 6(a) is a diagram showing an example of the time characteristics of the transmitted ultrasonic waves of the fourth drive signal of FIG. 6(a) and the sixth drive signal of FIG. 6(b) and the signal strength of their combined signal. FIG. 6(b) is a diagram showing an example of the frequency characteristics of the transmitted ultrasonic waves of the fourth drive signal of FIG. 6(a) and the fourth drive signal of FIG. 6(b) and the signal strength of their combined signal, and the transmission band of an ultrasonic probe. [Figure 8] 10 is a diagram showing a preferred embodiment of frequency characteristics of signal strength of ultrasonic waves transmitted from the first transducer group and the second transducer group. FIG. [Figure 9] 1A is a diagram showing the time characteristics of the signal strength of a drive signal having a first drive waveform, and FIG. 1B is a diagram showing the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to the drive signal having the first drive waveform. [Figure 10]10A is a diagram showing the time characteristics of the signal strength of a drive signal having a second drive waveform, and FIG. 10B is a diagram showing the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to the drive signal having the second drive waveform. [Figure 11] 10A is a diagram showing the time characteristics of the signal strength of a drive signal having a third drive waveform, and FIG. 10B is a diagram showing the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to the drive signal having the third drive waveform. [Figure 12] 10A is a diagram showing the time characteristics of the signal strength of a drive signal having a fourth drive waveform, and FIG. 10B is a diagram showing the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to the drive signal having the fourth drive waveform. [Figure 13] 10A is a diagram showing the time characteristics of the signal strength of a drive signal having a fifth drive waveform, and FIG. 10B is a diagram showing the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to the drive signal having the fifth drive waveform. [Figure 14] 10A is a diagram showing the time characteristics of the signal strength of a drive signal having a sixth drive waveform, and FIG. 10B is a diagram showing the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to the drive signal having the sixth drive waveform. [Figure 15] 1A is a diagram showing the time characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals with first and second drive waveforms, and FIG. 1B is a diagram showing the frequency characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals with first and second drive waveforms. [Figure 16] 1A is a diagram showing the time characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals of the third and fourth drive waveforms, and FIG. 1B is a diagram showing the time characteristics of the first combined waveform of transmitted ultrasonic waves corresponding to drive signals of the third and fourth drive waveforms. [Figure 17] 10 is a diagram showing frequency characteristics of the signal strength of a transmitted ultrasonic wave corresponding to drive signals of third and fourth drive waveforms and a combined signal of a first combined waveform. FIG. [Figure 18] 10 is a diagram showing the time characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals of fifth and fourth drive waveforms. FIG. [Figure 19]10A is a diagram showing the time characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals of the sixth and fourth drive waveforms, and FIG. 10B is a diagram showing the time characteristics of the second combined waveform of transmitted ultrasonic waves corresponding to drive signals of the sixth and fourth drive waveforms. [Figure 20] 10 is a diagram showing frequency characteristics of the signal strength of a transmitted ultrasonic wave corresponding to drive signals of sixth and fourth drive waveforms and a combined signal of the second combined waveform. FIG. [Figure 21] 10(a) is a diagram showing an ultrasound image of a first subject in a fourth comparative example, and (b) is a diagram showing an ultrasound image of a first subject in a first example. [Figure 22] 21(a) is a 3D graph of the luminance values ​​of the partial region in FIG. 21(a), and FIG. 21(b) is a 3D graph of the luminance values ​​of the partial region in FIG. [Figure 23] 10(a) is a diagram showing an ultrasound image of a second subject in a fourth comparative example, and (b) is a diagram showing an ultrasound image of a second subject in the first embodiment. [Figure 24] 23(a) is a 3D graph of the luminance values ​​of the partial region in FIG. 23(a), and FIG. 23(b) is a 3D graph of the luminance values ​​of the partial region in FIG. 23(b). [Figure 25] FIG. 2 is a diagram showing the intensity of sound pressure of ultrasonic waves transmitted by an ultrasonic probe. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the illustrated examples.

[0021] First, the device configuration of an ultrasound diagnostic device S according to the present embodiment will be described with reference to Figures 1 to 3. Figure 1 is an external view of the ultrasound diagnostic device S according to the present embodiment. Figure 2 is a block diagram showing the functional configuration of the ultrasound diagnostic device S. Figure 3 is a block diagram showing the functional configuration of a transmission unit 12.

[0022] 1 and 2, an ultrasound diagnostic device S according to this embodiment includes an ultrasound diagnostic device main body 1 and an ultrasound probe 2. The ultrasound probe 2 transmits ultrasound waves (transmitted ultrasound waves) to a subject such as a living organism (not shown), and receives received ultrasound waves including reflected ultrasound waves and scattered ultrasound waves reflected by the subject. The ultrasound diagnostic device main body 1 is connected to the ultrasound probe 2. The ultrasound diagnostic device main body 1 transmits an electrical drive signal to the ultrasound probe 2 to cause the ultrasound probe 2 to transmit transmitted ultrasound waves to the subject, and also visualizes the internal state of the subject as ultrasound image data based on a received signal, which is an electrical signal generated by the ultrasound probe 2 in response to the received ultrasound waves from within the subject and received by the ultrasound probe 2.

[0023] The ultrasonic probe 2 has an ultrasonic probe body 21, a cable 22, and a connector 23. The ultrasonic probe body 21 is a header portion of the ultrasonic probe 2 that transmits and receives ultrasonic waves. The cable 22 is connected between the ultrasonic probe body 21 and the connector 23, and is a cable through which a drive signal for the ultrasonic probe body 21 and an ultrasonic reception signal flow. The connector 23 is a plug connector for connecting to a receptacle connector (not shown) of the ultrasonic diagnostic apparatus body 1.

[0024] The ultrasound diagnostic device main body 1 is connected to the ultrasound probe main body 21 via a connector 23 and a cable 22. The ultrasound probe main body 21 is a main body of an intracavity probe (transvaginal probe) for examining a body cavity (e.g., the inside of the vagina) of a subject, and includes transducers 2a formed from piezoelectric elements and an acoustic lens that focuses transmitted ultrasound toward a focal point. The transducers 2a are arranged, for example, in a 180° semicircular pattern. In this embodiment, an ultrasound probe 2 including, for example, 192 transducers 2a is used. The transducers 2a may be arranged in a two-dimensional array. The number of transducers 2a can be set arbitrarily. In this embodiment, an electronically scanned intracavity probe is used for the ultrasound probe 2. However, either an electronically scanned or mechanically scanned probe may be used, and any of a linear scanning method, a sector scanning method, or a convex scanning method may also be used.

[0025] The frequency bandwidth of the ultrasonic probe 2 is preferably such that the -20 dB fractional bandwidth of the transmission / reception sensitivity is 100% or more, and more preferably 120% or more. Specifically, if the center frequency of the ultrasonic probe 2 is 6 MHz, the -20 dB bandwidth is preferably wider than 3 to 9 MHz, and more preferably 2.4 to 9.8 MHz. By using a wideband ultrasonic probe 2, it is possible to transmit both high frequencies that drive shallow harmonic generation and low frequencies that are important for ensuring penetration, making it possible to obtain a good S / N (Signal to Noise Ratio) from shallow to deep areas. Furthermore, since the upper bandwidth limit of the cancellation residual component is limited by the bandwidth of the ultrasonic probe, using a wideband ultrasonic probe 2 contributes to improved resolution.

[0026] As shown in FIG. 2, the ultrasound diagnostic device main body 1 includes, for example, an operation input unit 11, a transmitting unit 12, a receiving unit 13, an image generating unit 14, an image processing unit 15, a DSC (Digital Scan Converter) 16, a display unit 17, a control unit 18, and a storage unit 19.

[0027] The operation input unit 11 is equipped with various switches, buttons, a trackball, a mouse, a keyboard, etc. for inputting commands to start a diagnosis and data such as personal information of the subject, and accepts operation inputs from users such as doctors and technicians, and outputs the operation signals to the control unit 18.

[0028] The transmitter 12 is a circuit that supplies drive signals, which are electrical signals, to the ultrasonic probe 2 under the control of the controller 18, causing the ultrasonic probe 2 to generate transmitted ultrasonic waves. The transmitter 12 also divides the multiple transducers 2a of the transmission aperture of the ultrasonic probe 2 into two types: a first transducer group arranged inside the transmission aperture (center of the transmission aperture) and a second transducer group arranged outside the first transducer group (periphery of the transmission aperture). The transmitter 12 generates drive signals with different drive waveforms aimed at the same focal point, applies time delays to the drive signals so that the transmitted ultrasonic waves are focused at the same focal point, and outputs the drive signals to the first transducer group and the second transducer group, respectively. In this embodiment, "different drive waveforms" refers to drive signals with different drive control signals. The transmission aperture is the opening of a series of a predetermined number (e.g., 46) of transducer groups among all the transducers 2a of the ultrasonic probe 2, which output drive signals for ultrasonic transmission.

[0029] As shown in FIG. 3, the transmission unit 12 includes, for example, a clock generation circuit 121, a pulse generation circuit 122, a time and voltage setting unit 123, and a delay circuit .

[0030] The clock generation circuit 121 is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of the drive signal. The pulse generation circuit 122 is a circuit that generates a pulse signal as a drive signal at a predetermined cycle. The pulse generation circuit 122 can generate a square wave drive signal by switching between three voltage values ​​(+HV / 0 (GND) / -HV) and outputting them, for example. At this time, the amplitude of the pulse signal is the same for positive and negative polarities, but is not limited to this. In this embodiment, the drive signal is output by switching between three voltage values, but is not limited to three values ​​and can be set to an appropriate value such as five values ​​(+HV / +MV / 0 (GND) / -MV / -HV), although five values ​​or less are preferable. This makes it possible to improve the degree of freedom in controlling frequency components at low cost and obtain transmitted ultrasound with higher resolution.

[0031] The time and voltage setting unit 123 sets the duration and voltage level of each section of the drive signal output from the pulse generating circuit 122, which has the same voltage level. That is, the pulse generating circuit 122 outputs a drive signal having a pulse waveform in accordance with the duration and voltage level of each section set by the time and voltage setting unit 123. The duration and voltage level of each section set by the time and voltage setting unit 123 can be varied, for example, by inputting data using the operation input unit 11.

[0032] The delay circuit 124 is a circuit that sets a delay time for the transmission timing of the drive signal for each individual path corresponding to each transducer, and delays the transmission of the drive signal by the set delay time to focus the transmission beam formed by the transmitted ultrasound.

[0033] The transmitting unit 12, under the control of the control unit 18, sequentially switches between the multiple transducers 2a of the transmitting aperture to which the drive signal is supplied, shifting them by a predetermined number for each transmission and reception of ultrasound, and performs scanning by supplying drive signals to the multiple transducers 2a whose outputs are selected.

[0034] In this embodiment, a pulse inversion method can be implemented to extract the harmonic components of THI. The pulse inversion method is a method of canceling out the fundamental wave components and extracting only the harmonic components by adding the received signals (echo signals) when two drive signals with fundamental waves whose phases are inverted from each other are transmitted. That is, when the pulse inversion method is implemented, the transmitter 12 can transmit, as (transmitted) drive signals, a first drive signal with a first drive waveform and a second drive signal with a second drive waveform whose signal intensity (voltage) is inverted in polarity from the first drive signal, on the same scanning line at a time interval. The first drive signal and the second drive signal with inverted polarity are referred to as drive signals for symmetric pulse inversion (hereinafter referred to as symmetric PI) in this invention.

[0035] The transmitter 12 can also transmit a second drive signal in which at least one of the multiple duties of the first drive signal is changed to invert the polarity. In this case, when drive signals corresponding to the first drive signal and the second drive signal are added, a component remains, and this component is called a cancellation residue. The first drive signal and the second drive signal in which a cancellation residue occurs are called asymmetric pulse inversion (hereinafter referred to as asymmetric PI) drive signals in this invention.

[0036] As described above, the symmetry / asymmetry of the PI in this embodiment is defined by the positive / negative symmetry of the (transmitted) drive signal, and symmetry based on other symmetry axes such as time reversal symmetry is not taken into consideration. Furthermore, the positive / negative asymmetry due to the characteristics of the drive device, such as asymmetry in the rise / fall time of the drive voltage or differences in overshoot / undershoot characteristics, is also not taken into consideration. In other words, the symmetry / asymmetry of the PI is defined by the positive / negative symmetry of the drive (control) signal.

[0037] Here, the first drive signal includes a third drive signal and a fourth drive signal, and the second drive signal includes a fifth drive signal and a sixth drive signal. The third drive signal and the fifth drive signal are drive signals having a symmetric PI relationship, and the fourth drive signal and the sixth drive signal are drive signals having an asymmetric PI relationship. The transmitter 12 configured as described above generates a first drive signal including the third drive signal and the fourth drive signal, and a second drive signal of a second drive waveform including the fifth drive signal and the sixth drive signal. The transmitter 12 outputs a first drive signal to output a third drive signal to the first transducer group inside the transmission aperture and a fourth drive signal to the second transducer group outside the transmission aperture so as to be parfocal, and then outputs a second drive signal to output a fifth drive signal to the first transducer group inside the transmission aperture and a sixth drive signal to the second transducer group outside the transmission aperture so as to be parfocal with the first drive signal. The relationship between the first to sixth drive signals and the first and second transducer groups is summarized in Table I below. [Table 1]

[0038] The receiving unit 13 is a circuit that receives an electrical reception signal from the ultrasound probe 2 under the control of the control unit 18. The receiving unit 13 includes, for example, an amplifier, an A / D conversion circuit, and a phasing and summing circuit. The amplifier is a circuit that amplifies the reception signal at a predetermined amplification factor that is set in advance for each individual path corresponding to each transducer 2a. The A / D conversion circuit is a circuit that performs analog-to-digital conversion (A / D conversion) on the amplified reception signal. The phasing and summing circuit is a circuit that adjusts the time phase by providing a delay time for the A / D converted reception signal for each individual path corresponding to each transducer 2a, and adds these signals (phasing and summing) to generate sound ray data.

[0039] The image generation unit 14 performs envelope detection processing, logarithmic amplification, etc. on the sound ray data from the receiving unit 13, and performs gain adjustment and other processes to convert the brightness, thereby generating B-mode image data. In other words, the B-mode image data represents the strength of the received signal by brightness. The B-mode image data generated by the image generation unit 14 is transmitted to the image processing unit 15. The image generation unit 14 also includes a harmonic component extraction unit 14a, and generates B-mode image data from the harmonic components extracted by the harmonic component extraction unit 14a.

[0040] The harmonic component extraction unit 14a extracts harmonic components from the acoustic ray data of the received signal output from the receiving unit 13 by performing pulse inversion. More specifically, the harmonic component extraction unit 14a adds (combines) the acoustic ray data of the first received signal corresponding to the first drive signal and the acoustic ray data of the second received signal corresponding to the second drive signal, removes the fundamental wave component contained in the received signal, and performs filtering as needed to extract harmonic components. The harmonic components of odd-order harmonic components are obtained by subtracting (combining) the acoustic ray data of the same first and second received signals, removing the even-order harmonic components, and performing filtering as needed. The extracted even-order harmonic components and odd-order harmonic components are then added (combined) after performing phase adjustment processing using an all-pass filter or the like as needed, thereby enabling the even-order and odd-order harmonics to combine without canceling each other out, thereby obtaining a wideband received signal.

[0041] The image processing unit 15 includes an image memory unit 15a configured with a semiconductor memory such as a DRAM (Dynamic Random Access Memory). The image processing unit 15 stores the B-mode image data output from the image generation unit 14 in the image memory unit 15a in frame units. Image data in frame units is sometimes referred to as ultrasound image data or frame image data. The image processing unit 15 appropriately reads out the ultrasound image data stored in the image memory unit 15a and outputs it to the DSC 16.

[0042] The DSC 16 performs processing such as coordinate conversion on the ultrasound image data received from the image processing unit 15 to convert it into an image signal, and outputs it to the display unit 17 .

[0043] Display devices such as an LCD (Liquid Crystal Display), a CRT (Cathode-Ray Tube) display, an organic EL (Electronic Luminescence) display, an inorganic EL display, and a plasma display are applicable to the display unit 17. The display unit 17 displays an ultrasound image on a display screen in accordance with the image signal output from the DSC 16.

[0044] The control unit 18 is configured with, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), reads various processing programs such as a system program stored in the ROM, expands them into the RAM, and centrally controls the operation of each unit of the ultrasound diagnostic apparatus S in accordance with the expanded programs. The ROM is configured with non-volatile memory such as a semiconductor, and stores the system program corresponding to the ultrasound diagnostic apparatus S, various processing programs executable on the system program, and various data. These programs are stored in the form of computer-readable program code, and the CPU sequentially executes operations in accordance with the program code. The RAM forms a work area that temporarily stores various programs executed by the CPU and data related to these programs.

[0045] The ROM stores an ultrasonic image display program for executing an ultrasonic image display process, which will be described later. The control unit 18 selects a first drive signal (a third drive signal and a fourth drive signal) and a second drive signal (a fifth drive signal having a symmetric PI with the third drive signal and a sixth drive signal having an asymmetric PI with the fourth drive signal) from a plurality of drive signals having different drive waveforms in accordance with the ultrasonic image display program, and causes the transmission unit 12 to apply a time delay to the first drive signal and the second drive signal so that the transmitted ultrasonic waves are focused at the same focal point and output the signals to the transducers 2a of the ultrasonic probe 2 in order on the same acoustic line. At this time, the third drive signal and the fifth drive signal are output to the first transducer group that is inside the transmission aperture of the transducers 2a, and the fourth drive signal and the sixth drive signal are output to the second transducer group that is outside the transmission aperture of the transducers 2a, thereby transmitting the transmitted ultrasonic waves to the subject. Then, the control unit 18 causes the receiving unit 13 to generate received signals of received ultrasound corresponding to the third to sixth drive signals, causes the image generating unit 14 to add the received signals corresponding to the first drive signal and the second drive signal by pulse inversion and extract harmonic components to generate ultrasound image data, and causes the ultrasound image data to be displayed as an ultrasound image on the display unit 17 via the image processing unit 15 and the DSC 16. The control unit 18 performs live image display by repeatedly generating and displaying the ultrasound image data, and holds and saves the ultrasound image data in response to freeze and save operation inputs from the user via the operation input unit 11.

[0046] The storage unit 19 is a storage unit such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive) that can read and write information, and stores information such as ultrasound image data.

[0047] Next, the sound pressure characteristics of the ultrasound probe 2, which is an intracavity probe, will be described with reference to Figures 4(a) and 4(b). Figure 4(a) is a diagram showing the transmission strength of the transmitted ultrasound for the channel of the transducer 2a of the ultrasound probe 2. Figure 4(b) is a diagram showing the sound pressure increase contribution in the transmission center direction of the channel of the transducer 2a of the ultrasound probe 2.

[0048] In the ultrasonic probe 2, the acoustic radiation surface of the transducer 2a is a small-diameter arc, and there is a limit to how much the transmission aperture width can be increased even if the number of elements in the transducer 2a is increased. As shown in Figure 4(a), even if ultrasonic waves are transmitted at the same transmission intensity for each channel of the transducer 2a of the transmission aperture, due to the influence of directivity angle sensitivity, as shown in Figure 4(b), the contribution of ultrasonic transmission to the increase in sound pressure from the channels outside the transmission aperture (parts far from the transmission center) is small. For this reason, if the transmission center of the transmission aperture is blocked by an acoustic obstruction, the resistance to rear obstruction (shadow) is weak.

[0049] Specific examples of acoustic obstructions that exhibit high reflection and high attenuation and cause shadows in the transvaginal echo region include uterine fibroids with calcification due to calcium accumulation and air bubbles that have entered the cervix, while specific examples of objects that exhibit high attenuation include uterine fibroids without calcification, malignant tumors, and cervical mucus.

[0050] Next, with reference to Figs. 5 to 7(b), pulse signals of transmitted ultrasound corresponding to the drive signals (the above-mentioned first drive signal (third drive signal + fourth drive signal) and second drive signal (fifth drive signal + sixth drive signal) of the asymmetric PI of this embodiment will be described. Fig. 5 is a diagram showing ultrasonic beams corresponding to the first transducer group and the second transducer group output from the ultrasound probe 2L. Fig. 6(a) is a diagram showing an example of the time characteristic of the signal strength of the transmitted ultrasound corresponding to the fourth drive signal. Fig. 6(b) is a diagram showing an example of the time characteristic of the signal strength of the transmitted ultrasound corresponding to the sixth drive signal. Fig. 7(a) is a diagram showing an example of the time characteristic of the signal strength of the transmitted ultrasound of the fourth drive signal of Fig. 6(a) and the sixth drive signal of Fig. 6(b) and their combined signal. Fig. 7(b) is a diagram showing an example of the frequency characteristic of the signal strength of the transmitted ultrasound of the fourth drive signal of Fig. 6(a) and the fourth drive signal of Fig. 6(b) and their combined signal, as well as the transmission band of the ultrasound probe 2.

[0051] In FIG. 5, in order to clearly illustrate the ultrasonic beam, a linear ultrasonic probe 2L is used instead of the ultrasonic probe 2 as an intracavity probe, but the generation of the ultrasonic beam of the ultrasonic probe 2 is similar to that of the ultrasonic probe 2L.

[0052] As shown in Fig. 5, symmetric PI drive signals (the third drive signal of the first drive signal and the fifth drive signal of the second drive signal) are input from the ultrasonic probe 2L to the first transducer group located inside the transmit aperture, and a symmetric PI ultrasonic beam U1 is output from the first transducer group located inside to be focused at a focal point along the center line C1 of the transmit center of the transmit aperture. At the same time, asymmetric PI drive signals (the fourth drive signal of the first drive signal and the sixth drive signal of the second drive signal) are input from the ultrasonic probe 2L to the second transducer group located outside the transmit aperture, and an asymmetric PI ultrasonic beam U2 is output from the second transducer group located outside the ultrasonic beam U1 to be similarly focused at a focal point. The center line C1 moves in the scanning direction (the direction of the transducer arrangement) due to the sub-scanning for generating a B-mode image.

[0053] The generation region of the harmonic components of the ultrasonic beam U1 is shown as region AR1. The generation region of the harmonic components of the ultrasonic beam U2 is shown as region AR2. The generation region of the cancellation residue of the combined signal obtained by adding (summing) the second pulse signal and the fourth pulse signal of the asymmetric PI is shown as region AR3.

[0054] Here, an example of the transmitted ultrasonic waves and summed signals of the drive signals of the asymmetric PI will be described. As a pulse signal of the transmitted ultrasonic waves corresponding to the fourth drive signal, a transmitted ultrasonic wave having a drive waveform (dashed line in the figure) of the signal strength [mV] of the transmitted ultrasonic waves with respect to time [μs] shown in FIG. 6(a) is output, and as a pulse signal of the transmitted ultrasonic waves corresponding to the sixth drive signal, a transmitted ultrasonic wave having a drive waveform (dashed line in the figure) of the signal strength [mV] of the transmitted ultrasonic waves with respect to time [μs] shown in FIG. 6(b) is output. When these are reflected and obtained as received signals, the imaging signal obtained by computing these signals is the sum (addition) of the transmitted ultrasonic waves corresponding to the fourth drive signal in FIG. 6(a) and the transmitted ultrasonic waves corresponding to the sixth drive signal in FIG. 6(b). As a result, as shown in Figure 7(a), the signal strength [mV] of the transmitted ultrasonic wave over time [μs] (the signal strength of the combined signal is shown as a solid line in the figure) is obtained as a calculation result for the combined signal of the transmitted ultrasonic wave (dashed line) corresponding to the fourth drive signal in Figure 6(a) and the transmitted ultrasonic wave (dash-dotted line) corresponding to the sixth drive signal in Figure 6(b). Furthermore, by performing a Fourier transform on the pulse signals of the transmitted ultrasonic wave corresponding to the fourth drive signal in Figure 7(a), the transmitted ultrasonic wave corresponding to the sixth drive signal, and the combined signal, the signal strength [dB] (frequency power spectrum) of the transmitted ultrasonic wave over frequency [MHz] of the transmitted ultrasonic wave corresponding to the fourth drive signal, the transmitted ultrasonic wave corresponding to the sixth drive signal, and the combined signal is obtained, as shown in Figure 7(b). The components of the combined signal in Figures 7(a) and 7(b) are cancellation residues.

[0055] The first feature of the combined signal of asymmetric PIs is that, as shown in Figure 7(a), the cancellation residual of asymmetric PIs is a linear component, unlike harmonics generated in high sound pressure regions, making it possible to obtain it even at low sound pressures. The second feature is that, as shown in Figure 7(b), a wideband signal component can be obtained by combining the low-frequency transmitted ultrasonic waves corresponding to the fourth drive signal in Figure 6(a) and the received signal corresponding to the low-frequency transmitted ultrasonic waves corresponding to the sixth drive signal in Figure 6(b). This makes it possible to obtain ultrasound image data with excellent axial resolution and speckle granularity. The third feature is that, as shown in Figure 7(a), the transmitted ultrasonic waves of the fourth drive signal and the sixth drive signal are low-frequency, so they tend to spread (diffract) and wrap around the shadow areas of acoustic obstructions, making them suitable for filling in the shadow areas.

[0056] FIG. 7(b) shows an example of the transmission band (transmission frequency band) (signal strength [dB] of transmitted ultrasound relative to frequency [MHz]) (two-dot chain line in the figure) of the ultrasonic probe 2. In this embodiment and in the comparative example and examples described later, an ultrasonic probe 2 having the transmission band characteristics of FIG. 7(b) is used. However, the transmission band of FIG. 7(b) is the transmission characteristic when a wideband impulse is input, and although it shows the transmission band characteristics of the ultrasonic probe 2, the input energy is not the same, so the absolute value on the vertical axis (signal strength [dB]) is a reference value.

[0057] Next, preferred conditions for the transmitted ultrasonic waves of symmetric PI and the transmitted ultrasonic waves of asymmetric PI will be described with reference to Fig. 8. Fig. 8 is a diagram showing preferred aspects of the frequency characteristics of the signal intensity of the transmitted ultrasonic waves of the first transducer group and the second transducer group.

[0058] FIG. 8 shows the -20 dB transmission frequency band of the ultrasonic probe 2 (dashed line on the figure), the signal component ITx as the frequency characteristic (frequency power spectrum) of the signal strength of the transmitted ultrasonic waves from the first group of transducers, and the signal component OTx as the frequency characteristic (frequency power spectrum) of the signal strength of the transmitted ultrasonic waves from the second group of transducers.

[0059] First, condition (a) is set to: the center frequency of the signal component OTx<the center frequency of the signal component ITx. Here, the center frequency ([MHz]) is the average value of the upper and lower limit frequencies that first fall below -6 dB from the signal intensity value of the peak frequency in the frequency power spectrum.

[0060] Furthermore, condition (b) is that the bandwidth of the signal component OTx is less than the bandwidth of the signal component ITx. Here, the (frequency) bandwidth ([MHz]) is the difference between the upper and lower limit frequencies that first fall below -6 dB from the intensity value of the peak frequency of the frequency power spectrum. The relative bandwidth [%] is the percentage obtained by dividing the above bandwidth by the above center frequency.

[0061] Moreover, as a condition (c), in the high frequency region above the −20 dB center frequency of the ultrasonic probe 2, the signal intensity of the signal component OTx is smaller than the signal intensity of the signal component ITx.

[0062] It is known that when ultrasound hits scatterers much smaller than its wavelength, the scattering intensity is proportional to the fourth power of the frequency. By configuring conditions (a), (b), and (c), the high-frequency components of the transmitted waves are prevented from scattering in biological tissue and entering the receiving area as acoustic noise, which is particularly useful for improving the visualization of shallow, anechoic to hypoechoic areas. Furthermore, only low-frequency components necessary for generating high-frequency harmonics near the transmission focus are transmitted to the second transducer group, while high-frequency components that do not contribute to this are not transmitted. This reduces the amount of heat generated on the probe surface, etc., and improves transmission efficiency, thereby improving penetration.

[0063] Furthermore, condition (d) is set such that the center frequency of the transmitted ultrasonic wave corresponding to the fourth drive signal of the first drive signal<the center frequency of the combined signal of the cancellation residual (cancellation residual component), and the center frequency of the transmitted ultrasonic wave corresponding to the sixth drive signal of the second drive signal<the center frequency of the cancellation residual component. For example, condition (d) is satisfied in FIG. 7(b).

[0064] Furthermore, the condition (e) is that the bandwidth of the transmitted ultrasonic wave corresponding to the fourth drive signal is less than the bandwidth of the cancellation residual component, and the bandwidth of the transmitted ultrasonic wave corresponding to the sixth drive signal is less than the bandwidth of the cancellation residual component. For example, the condition (e) is satisfied in FIG. 7(b).

[0065] By designing the canceling residual components to satisfy conditions (d) and (e), the characteristics of the low frequency components are utilized to increase the amount of wraparound of the transmitted wave components into the shadow areas of acoustic obstructions in ultrasound images (the effect of covering the shadow areas is enhanced), but the image signal of the canceling residual components obtained in this way has a higher frequency than the transmitted ultrasound and a wider bandwidth, resulting in finer image granularity and images with high distance resolution.

[0066] Next, with reference to FIGS. 9(a) to 20, specific comparative examples 1 to 4 and examples 1 to 3 of the ultrasound probe 2 according to this embodiment and transmission conditions such as the drive signal and the transmitted ultrasound will be described. FIG. 9(a) is a diagram showing the time characteristics of the signal strength of the drive signal of drive waveform 1. FIG. 9(b) is a diagram showing the time characteristics of the signal strength of the transmitted ultrasound corresponding to the drive signal of drive waveform 1. FIG. 10(a) is a diagram showing the time characteristics of the signal strength of the drive signal of drive waveform 2. FIG. 10(b) is a diagram showing the time characteristics of the signal strength of the transmitted ultrasound corresponding to the drive signal of drive waveform 2. FIG. 11(a) is a diagram showing the time characteristics of the signal strength of the drive signal of drive waveform 3. FIG. 11(b) is a diagram showing the time characteristics of the signal strength of the transmitted ultrasound corresponding to the drive signal of drive waveform 3. FIG. 12(a) is a diagram showing the time characteristics of the signal strength of the drive signal of drive waveform 4. FIG. 12(b) is a diagram showing the time characteristics of the signal strength of the transmitted ultrasound corresponding to the drive signal of drive waveform 4. FIG. 13(a) is a diagram showing the time characteristics of the signal strength of the drive signal of drive waveform 5. Fig. 13(b) is a diagram showing the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to a drive signal of drive waveform 5. Fig. 14(a) is a diagram showing the time characteristics of the signal strength of a drive signal of drive waveform 6. Fig. 14(b) is a diagram showing the time characteristics of the signal strength of a transmitted ultrasonic wave corresponding to a drive signal of drive waveform 6.

[0067] FIG. 15(a) is a diagram showing the time characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals of drive waveforms 1 and 2. FIG. 15(b) is a diagram showing the frequency characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals of drive waveforms 1 and 2. FIG. 16(a) is a diagram showing the time characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals of drive waveforms 3 and 4. FIG. 16(b) is a diagram showing the time characteristics of combined waveform 1 of transmitted ultrasonic waves corresponding to drive signals of drive waveforms 3 and 4. FIG. 17 is a diagram showing the frequency characteristics of the signal strength of the combined signal of transmitted ultrasonic waves and combined waveform 1 corresponding to drive signals of drive waveforms 3 and 4. FIG. 18 is a diagram showing the frequency characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals of drive waveforms 5 and 4. FIG. 19(a) is a diagram showing the time characteristics of the signal strength of transmitted ultrasonic waves corresponding to drive signals of drive waveforms 6 and 4. FIG. 19(b) is a diagram showing the time characteristics of combined waveform 2 of transmitted ultrasonic waves corresponding to drive signals of drive waveforms 6 and 4. FIG. 20 is a diagram showing frequency characteristics of the signal intensity of the transmitted ultrasonic waves corresponding to the drive signals of the drive waveforms 6 and 4 and the combined signal of the combined waveform 2. In FIG.

[0068] The present invention will be explained below using comparative examples and examples. Note that the vertical axis of the transmitted ultrasonic wave time characteristics in the comparative examples and examples is originally sound pressure (Pa), but for convenience, it is expressed as voltage value (mV) measured with a hydrophone under the same conditions and with the same measurement system. <Comparative Example 1> Comparative Example 1 will be described with reference to Figures 9(a) to 10(b), 15(a), and 15(b). In Comparative Example 1, the transducers 2a of the transmission aperture of the ultrasound probe 2 are not divided into a first transducer group located inside the center of the transmission aperture and a second transducer group located outside the periphery of the transmission aperture, but a first drive signal of drive waveform 1 and a second drive signal of drive waveform 2 are output in sequence from the transmitter 12 to each transducer 2a of the transmission aperture, and imaging signals obtained by the pulse inversion method are visualized based on the obtained reception signals.

[0069] The ultrasound probe 2 used was a transvaginal probe with a radius of curvature of 10 mm and an element pitch of the transducer 2a of 0.15 mm. The transmission frequency band of the ultrasound probe 2 used is shown by the two-dot chain line in FIG. 7(b). As will be described later, image evaluation was performed with the transmission focus set to 30 mm. This ultrasound probe 2 and the transmission focus for image evaluation were common to Comparative Examples 1 to 4 and Examples 1 to 3. The number of elements in the transducer 2a of the transmission aperture of the ultrasound probe 2 of Comparative Example 1 was 46.

[0070] The waveform of the first drive signal in Comparative Example 1 is referred to as drive waveform 1. Fig. 9(a) shows the signal strength [V] of the drive signal of drive waveform 1 versus time [ns]. Fig. 9(b) shows the signal strength [mV] of the transmitted ultrasonic wave (transmitted ultrasonic wave emitted by inputting the drive signal to ultrasonic probe 2) corresponding to the drive signal of drive waveform 1 versus time [μs]. In Fig. 9(b), the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 1 is indicated by a dashed line.

[0071] The waveform of the second drive signal in Comparative Example 1 is referred to as drive waveform 2. Fig. 10(a) shows the signal strength [V] of the drive signal of drive waveform 2 versus time [ns]. Fig. 10(b) shows the signal strength [mV] of the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 2 versus time [μs]. In Fig. 10(b), the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 2 is indicated by a dashed dotted line.

[0072] Figure 15(a) shows the superposition of the signal strength [mV] of the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 1 and the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 2 over time [μs]. Figure 15(b) shows the superposition of the signal strength [dB] (frequency power spectrum) of the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 1 and the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 2 over frequency [MHz]. In Figures 15(a) and 15(b), the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 1 is shown by a dashed line, and the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 2 is shown by a dashed line. In Figure 15(b), the frequency characteristics of drive waveform 1 and drive waveform 2 are the same, so they are shown superimposed.

[0073] As shown in Figure 15(a), the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 2 has the opposite voltage polarity to the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 1. For this reason, as shown in Figure 15(b), the frequency power spectra of the transmitted ultrasonic waves corresponding to drive waveforms 1 and 2 match. Therefore, by adding the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 1 and the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 2, they are completely canceled out, and no cancellation residue occurs.

[0074] 9(a) and 10(a), the drive signals of drive waveforms 1 and 2 are generated using three common values: GND (0 [V]), +HV, and -HV, which simplifies the configuration and control of the transmitter 12. This is true not only for drive waveforms 1 and 2, but also for drive waveforms 3 to 6.

[0075] The imaging signal of Comparative Example 1 is a sum signal (first / second transmission and reception result sum signal) of a reception signal (first transmission and reception result signal) generated by the reception unit 13 by ultrasonic transmission and reception corresponding to the first drive signal of the drive waveform 1 output from the transmission unit 12, and a reception signal (second transmission and reception result signal) generated by the reception unit 13 by ultrasonic transmission and reception corresponding to the second drive signal of the drive waveform 2 output from the transmission unit 12. The harmonic component extraction unit 14a extracts harmonic components of the first / second transmission and reception result sum signal, and the image generation unit 14 generates ultrasound image data using the harmonic components. Because only harmonic components are used, Cyst is well visualized, but shadows are strongly visualized in areas where sound pressure is reduced due to obstructions because insufficient harmonics are generated.

[0076] <Comparative Example 2> Comparative Example 2 will be described with reference to Figures 12(a) to 13(b) and 18. In Comparative Example 2, the transducers 2a of the transmission aperture of the ultrasound probe 2 are divided into a first transducer group that is inside the transmission aperture and a second transducer group that is outside the transmission aperture, and as a first drive signal, a third drive signal of drive waveform 1 is output from the transmitter 12 to the first transducer group that is inside the transmission aperture, and a fourth drive signal of drive waveform 2 is output from the transmitter 12 to the second transducer group that is outside the transmission aperture, and then, as a second drive signal, a fifth drive signal of drive waveform 5 is output from the transmitter 12 to the first transducer group that is inside the transmission aperture, and a sixth drive signal of drive waveform 4 is output from the transmitter 12 to the second transducer group that is outside the transmission aperture, and an imaging signal obtained by the pulse inversion method is visualized based on the obtained received signals.

[0077] The ultrasonic probe 2 of Comparative Example 2 has 16 transducer elements 2a in the first transducer group located inside the transmission aperture, and 30 transducer elements 2a in the second transducer group located outside the transmission aperture.

[0078] Of the first drive signals in Comparative Example 2, the waveform of the third drive signal output to the first transducer group located inside the transmission aperture is referred to as drive waveform 1. Of the second drive signals in Comparative Example 2, the waveform of the fifth drive signal input to the first transducer group located inside the transmission aperture is referred to as drive waveform 2.

[0079] Of the first drive signals in Comparative Example 2, the waveform of the fourth drive signal output to the second group of transducers outside the transmission aperture is designated drive waveform 5. Fig. 13(a) shows the signal strength [V] of the drive signal of drive waveform 5 versus time [ns]. Fig. 13(b) shows the signal strength [mV] of the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 5 versus time [μs]. In Fig. 13(b), the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 5 is indicated by a dashed line.

[0080] Of the second drive signals in Comparative Example 2, the waveform of the sixth drive signal output to the second group of transducers outside the transmission aperture is designated drive waveform 4. Figure 12(a) shows the signal strength [V] of the drive signal of drive waveform 4 versus time [ns]. Figure 12(b) shows the signal strength [mV] of the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 4 versus time [μs]. In Figure 12(b), the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 4 is indicated by a dashed dotted line.

[0081] In the case of the addition of the transmitted ultrasonic waves of the third drive signal of the drive waveform 1 and the fifth drive signal of the drive waveform 2 in the comparative example 2, no cancellation residue occurs, as in the case of the comparative example 1. 4 The drive signal and drive waveform 4 6 When the driving signal is added to the transmitted ultrasonic wave, no cancellation residue occurs.

[0082] Fig. 18 shows the superposition of the signal strength [mV] of the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 5 and the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 4 over time [μs]. In Fig. 18, the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 5 is shown by a dashed line, and the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 4 is shown by a dashed line.

[0083] 18, the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 4 has the opposite voltage polarity to the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 5. For this reason, the frequency power spectra of the transmitted ultrasonic waves corresponding to drive waveforms 5 and 4 match. Therefore, by adding the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 5 and the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 4, they are completely canceled out, and no cancellation residue occurs.

[0084] The imaging signal of Comparative Example 2 is a sum signal (first transmission and reception result signal) of a reception signal (first transmission and reception result signal) generated by the receiving unit 13 through transmission and reception of ultrasound waves corresponding to the third drive signal of drive waveform 1 output from the first transducer group inside the transmission aperture of the transmitting unit 12 and ultrasound waves corresponding to the fourth drive signal of drive waveform 5 output from the second transducer group outside the transmission aperture, and a reception signal (second transmission and reception result signal) generated by the receiving unit 13 through transmission and reception of ultrasound waves corresponding to the fifth drive signal of drive waveform 2 output from the first transducer group inside the transmission aperture of the transmitting unit 12 and ultrasound waves corresponding to the sixth drive signal of drive waveform 4 output from the second transducer group outside the transmission aperture. The harmonic component extracting unit 14a extracts harmonic components of the first and second transmission and reception result sum signal, and the image generating unit 14 generates ultrasound image data using the harmonic components. The frequency power spectrum of the ultrasound waves output from the first transducer group is as shown in Figure 15(b), and the frequency power spectrum of the ultrasound waves output from the second transducer group is as shown by the dashed line in Figure 17. Drive waveform 4 and drive waveform 5 are polarity-inverted symmetric and have the same frequency power spectrum, so they have the preferable relationship shown in Figure 8. Therefore, compared to Comparative Example 1, the transmission efficiency is improved, and in addition to good Cyst imaging, penetration is also improved. However, since only harmonic components are still used, sufficient harmonics are not generated in areas where sound pressure is reduced due to obstructions, and shadows are strongly imaged.

[0085] <Comparative Example 3> Comparative Example 3 will be described. Comparative Example 3 is a comparative example in which first and second drive signals (third to sixth drive signals) are output from the transmitter 12 to the transducer 2a of the transmission aperture of the ultrasound probe 2 under the same transmission conditions as Comparative Example 2, and an imaging signal obtained by the pulse inversion method based on the obtained reception signal and an imaging signal obtained by the second transmission reception signal are synthesized to form an image.

[0086] The imaging signal of Comparative Example 3 is a composite image obtained from a 50% image obtained using the sum signal (first / second transmission and reception result sum signal) of the first transmission and reception result signal and the second transmission and reception result signal of Comparative Example 2 as an imaging signal, and a 50% image obtained using the second transmission and reception result signal as an imaging signal. That is, the harmonic component extraction unit 14a extracts harmonic components using the first / second transmission and reception result sum signal, and the image generation unit 14 generates an image by combining, with a weight of 50%, ultrasound image data generated using the harmonic components and image data generated from the second transmission and reception result signal without performing harmonic component extraction processing. In addition to harmonic components, imaging is performed using the fundamental wave component used as the second transmission. This means that imaging components can be obtained using the fundamental wave component even in shadow areas where sound pressure is reduced, and although shadows are reduced, the contrast improvement effect of harmonics is not obtained, and the impact of acoustic noise is greater in low-brightness areas, so that the gradation change at the boundary of shallow Cyst imaging becomes gradual, deteriorating visibility, and the area also shrinks and decreases.

[0087] <Comparative Example 4> Comparative Example 4 will be described with reference to Figures 11(a), 11(b), and 16(a) to 17. In Comparative Example 4, the transducers 2a of the transmission aperture of the ultrasound probe 2 are not divided into a first transducer group on the inside and a second transducer group on the outside, but a first drive signal of drive waveform 3 and a second drive signal of drive waveform 4 are output in sequence from the transmitter 12 to each transducer 2a of the transmission aperture, and an imaging signal obtained by a reception signal addition calculation conforming to the pulse inversion method is visualized based on the obtained reception signals.

[0088] The waveform of the first drive signal in Comparative Example 4 is referred to as drive waveform 3. Fig. 11(a) shows the signal strength [V] of the drive signal of drive waveform 3 versus time [ns]. Fig. 11(b) shows the signal strength [mV] of the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 3 versus time [μs]. In Fig. 11(b), the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 3 is indicated by a dashed line.

[0089] The waveform of the second drive signal in Comparative Example 4 is referred to as drive waveform 4.

[0090] FIG. 16(a) shows the signal strength [mV] of the superposition of the transmitted ultrasonic waves corresponding to the drive signal of drive waveform 3 and the transmitted ultrasonic waves corresponding to the drive signal of drive waveform 4 over time [μs]. FIG. 16(b) shows the signal strength [mV] of the combined signal of the transmitted ultrasonic waves corresponding to the drive signal of drive waveform 3 and the combined signal of the combined waveform 1 corresponding to the drive signal of drive waveform 4 over time [μs]. FIG. 17 shows the signal strength [dB] (frequency power spectrum) of the transmitted ultrasonic waves corresponding to the drive signal of drive waveform 3 and the combined signal of the combined waveform 1 over frequency [MHz]. In FIGS. 16(a) to 17, the signal strength of the transmitted ultrasonic waves corresponding to drive waveform 3 is shown by a dashed line, the signal strength of the transmitted ultrasonic waves corresponding to drive waveform 4 is shown by a dashed line, and the signal strength of the combined signal of the combined waveform 1 is shown by a solid line.

[0091] As shown in Fig. 16(a), the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 4 is roughly the opposite in voltage polarity to the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 3, but is not completely opposite. For this reason, as shown in Fig. 16(b), the combined signal of combined waveform 1 of the transmitted ultrasonic waves corresponding to drive waveforms 3 and 4 does not become 0, but cancels out and remains. Furthermore, as shown in Fig. 17, the frequency power spectra of the transmitted ultrasonic waves corresponding to drive waveforms 3 and 4 and the combined signal of combined waveform 1 do not match.

[0092] The imaging signal of Comparative Example 4 is a sum signal (first / second transmission and reception result sum signal) of a reception signal (first transmission and reception result signal) generated by the reception unit 13 by ultrasonic transmission and reception corresponding to the first drive signal of the drive waveform 3 output from the transmission unit 12, and a reception signal (second transmission and reception result signal) generated by the reception unit 13 by ultrasonic transmission and reception corresponding to the second drive signal of the drive waveform 4 output from the transmission unit 12. The harmonic component extraction unit 14a extracts the harmonic components of the first / second transmission and reception result sum signal and also extracts the cancellation residual components, and the image generation unit 14 generates ultrasound image data using the harmonic components and cancellation residual components. In addition to harmonic components, imaging is performed using linear offset residual components. Therefore, imaging components can be obtained using fundamental wave components even in shadow areas where sound pressure has decreased, and although shadows are reduced, the contrast improvement effect of harmonics is not obtained, and the impact of acoustic noise is greater in low-brightness areas, so that the gradation change at the boundary of shallow Cyst imaging becomes gradual, deteriorating visibility, and the area also shrinks and decreases.

[0093] Example 1 Example 1 will be described. Example 1 is an example in which the transducers 2a of the transmission aperture of the ultrasound probe 2 are divided into a first transducer group on the inside and a second transducer group on the outside, and as a first drive signal, a third drive signal of drive waveform 1 is output from the transmitter 12 to the first transducer group on the inside, and a fourth drive signal of drive waveform 3 is output from the transmitter 12 to the second transducer group on the outside, and then, as a second drive signal, a fifth drive signal of drive waveform 2 is output from the transmitter 12 to the first transducer group on the inside, and a sixth drive signal of drive waveform 4 is output from the transmitter 12 to the second transducer group on the outside, and an imaging signal obtained by a received signal addition operation based on the obtained received signals in accordance with the pulse inversion method is visualized.

[0094] The ultrasonic probe 2 of Example 1 has 16 transducer elements 2a in the first transducer group located inside the transmission aperture, and 30 transducer elements 2a in the second transducer group located outside the transmission aperture.

[0095] Of the first drive signals in the first embodiment, the waveform of the third drive signal output to the first transducer group on the inside is referred to as drive waveform 1. Of the second drive signals in the first embodiment, the waveform of the third drive signal output to the first transducer group on the inside is referred to as drive waveform 2. 5 The waveform of the drive signal is referred to as drive waveform 2.

[0096] Of the first drive signals in Example 1, the waveform of the fourth drive signal output to the second outer transducer group is referred to as drive waveform 3. Of the second drive signals in Example 1, the waveform of the sixth drive signal output to the second outer transducer group is referred to as drive waveform 4.

[0097] When the transmitted ultrasonic waves are added together with the third drive signal of the drive waveform 1 in Example 1 and the fifth drive signal of the drive waveform 2, no offset residual occurs, as in Comparative Example 1. When the transmitted ultrasonic waves are added together with the fourth drive signal of the drive waveform 3 in Example 1 and the sixth drive signal of the drive waveform 4, an offset residual occurs in the composite signal of the composite waveform 1.

[0098] The imaging signal of Example 1 is a sum signal (first transmission and reception result signal) of a reception signal (first transmission and reception result signal) generated by the receiving unit 13 by transmission and reception of ultrasound waves corresponding to the third drive signal of drive waveform 1 output from the first transducer group located inside the transmitting unit 12 and ultrasound waves corresponding to the fourth drive signal of drive waveform 3 output from the second transducer group located outside, and a reception signal (second transmission and reception result signal) generated by the receiving unit 13 by transmission and reception of ultrasound waves corresponding to the fifth drive signal of drive waveform 2 output from the first transducer group located inside the transmitting unit 12 and ultrasound waves corresponding to the sixth drive signal of drive waveform 4 output from the second transducer group located outside. The harmonic component extraction unit 14a extracts harmonic components of the first and second transmission and reception result sum signal and also extracts cancellation residual components, and the image generation unit 14 generates ultrasound image data using the harmonic components and cancellation residual components. The proportion of the first transducer group, which does not generate cancellation residual components, is high, and there is almost no effect from shallow acoustic noise, so shallow Cyst imaging is good, and for deep shadow areas, image signals are obtained from the cancellation residual components obtained by the second transducer group, which is sufficiently improved. For shallow shadow areas, the image signal from the second transducer group is somewhat weak, but is improved to a level that is not a problem in practical use. Furthermore, the frequency power spectrum of the ultrasonic waves output from the first transducer group is as shown in Figure 15(b), and the frequency power spectrum of the ultrasonic waves output from the second transducer group is as shown by the dashed and dotted lines in Figure 17, which is in the preferred relationship shown in Figure 8. Therefore, penetration is also good.

[0099] <Example 2> Next, Example 2 will be described. Example 2 uses the same drive signals (third to sixth drive signals) as Example 1, and the total number of elements in the transmission aperture is also the same, but the number of elements in the transducers 2a of the first transducer group on the inside of the transmission aperture is 10, and the number of elements in the transducers 2a of the second transducer group on the outside is 36. Compared to Example 1, the proportion of the first transducer group that does not generate offset residual components is reduced, and although there is some influence from shallow acoustic noise, shallow Cyst imaging is achieved at a level that is not problematic for practical use, and shallow shadows are improved because more image signals are obtained from the second transducer group. For deep shadow regions, the same improvement effect as in Example 1 is obtained, and the relationship between the frequency power spectrum of the ultrasound output from the first transducer group and the frequency power spectrum of the ultrasound output from the second transducer group is the preferred relationship shown in Figure 8, as in Example 1, so penetration is also good.

[0100] Example 3 Example 3 will be described with reference to Figures 14(a), 14(b), and 19(a) to 20. Example 3 is an example in which the transducers 2a of the transmission aperture of the ultrasound probe 2 are divided into a first transducer group on the inside and a second transducer group on the outside, and as a first drive signal, a third drive signal of drive waveform 1 is output from the transmitter 12 to the first transducer group on the inside, and a fourth drive signal of drive waveform 6 is output from the transmitter 12 to the second transducer group on the outside, and then, as a second drive signal, a fifth drive signal of drive waveform 2 is output from the transmitter 12 to the first transducer group on the inside, and a sixth drive signal of drive waveform 4 is output from the transmitter 12 to the second transducer group on the outside, and an imaging signal obtained by a reception signal addition operation based on the obtained reception signals in accordance with the pulse inversion method is visualized.

[0101] The ultrasonic probe 2 of Example 3 has 10 transducer elements 2a in the first transducer group located inside the transmission aperture, and 36 transducer elements 2a in the second transducer group located outside the transmission aperture.

[0102] Of the first drive signals in Example 3, the waveform of the third drive signal output to the first transducer group on the inside is referred to as drive waveform 1. Of the second drive signals in Example 3, the waveform of the fifth drive signal output to the first transducer group on the inside is referred to as drive waveform 2.

[0103] Of the first drive signals in Example 3, the waveform of the fourth drive signal output to the outer second transducer group is designated drive waveform 6. Fig. 14(a) shows the signal strength [V] of the drive signal of drive waveform 6 versus time [ns]. Fig. 14(b) shows the signal strength [mV] of the transmitted ultrasonic wave corresponding to the drive signal of drive waveform 6 versus time [μs]. In Fig. 14(b), the signal strength of the transmitted ultrasonic wave corresponding to drive waveform 6 is indicated by a dashed line.

[0104] Of the second drive signals in the third embodiment, the waveform of the sixth drive signal output to the second transducer group on the outside is designated as drive waveform 4.

[0105] In the case of adding the transmitted ultrasonic waves of the third drive signal of the drive waveform 1 and the fifth drive signal of the drive waveform 2 in the third embodiment, no cancellation residue occurs, as in the case of the comparative example 1. 4 The drive signal and drive waveform 4 6 When the driving signal is added to the transmitted ultrasonic wave, a cancellation residue occurs.

[0106] FIG. 19(a) shows the signal strength [mV] of the superposition of the transmitted ultrasonic waves corresponding to the drive signal of drive waveform 6 and the transmitted ultrasonic waves corresponding to the drive signal of drive waveform 4 over time [μs]. FIG. 19(b) shows the signal strength [mV] of the combined signal of the transmitted ultrasonic waves corresponding to the drive signal of drive waveform 6 and the combined signal of the combined waveform 2 corresponding to the drive signal of drive waveform 4 over time [μs]. FIG. 20 shows the signal strength [dB] (frequency power spectrum) of the transmitted ultrasonic waves corresponding to the drive signal of drive waveform 6 and the combined signal of the combined waveform 2 over frequency [MHz]. In FIGS. 19(a) to 20, the signal strength of the transmitted ultrasonic waves corresponding to drive waveform 6 is shown by a dashed line, the signal strength of the transmitted ultrasonic waves corresponding to drive waveform 4 is shown by a dashed line, and the signal strength of the combined signal of the combined waveform 2 is shown by a solid line.

[0107] As shown in FIG. 19(a), the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 4 is roughly the opposite in voltage polarity to the signal intensity of the transmitted ultrasonic wave corresponding to drive waveform 6, but is not completely opposite. For this reason, as shown in FIG. 19(b), the combined signal of combined waveform 1 of the transmitted ultrasonic waves corresponding to drive waveforms 6 and 4 does not become 0, but remains due to cancellation. Furthermore, as shown in FIG. 20, the frequency power spectrum of the transmitted ultrasonic waves corresponding to drive waveforms 6 and 4 and the combined signal of combined waveform 2 do not match. Furthermore, from the frequency power spectrum of combined waveform 2 shown by the solid line in FIG. 20, it can be seen that the frequency bandwidth and center frequency of the combined waveform are almost the same as the frequency power spectrum of combined waveform 1 shown by the solid line in FIG. 17, but the component intensities are low overall, and the cancel-out residual component intensity of combined waveform 2 is weaker than that of combined waveform 1.

[0108] The imaging signal of Example 3 is a sum signal (first / second transmission and reception result sum signal) of a reception signal (first transmission and reception result signal) generated by the receiving unit 13 by transmission and reception of ultrasound waves corresponding to the third drive signal of drive waveform 1 output from the first transducer group located inside the transmitting unit 12 and ultrasound waves corresponding to the fourth drive signal of drive waveform 6 output from the second transducer group located outside, and a reception signal (second transmission and reception result signal) generated by the receiving unit 13 by transmission and reception of ultrasound waves corresponding to the fifth drive signal of drive waveform 2 output from the first transducer group located inside the transmitting unit 12 and ultrasound waves corresponding to the sixth drive signal of drive waveform 4 output from the second transducer group located outside. The harmonic component extraction unit 14a extracts harmonic components of the first / second transmission and reception result sum signal and also extracts cancellation residual components, and the image generation unit 14 generates ultrasound image data using the harmonic components and cancellation residual components. Compared to Example 2, in which the first and second transducer groups have the same number of elements, the second transducer group produces fewer offset residual components, which virtually eliminates the impact of shallow acoustic noise and improves the visualization of shallow Cysts. As with Example 2, the shadow reduction effect is sufficient in shallow shadow areas because the proportion of the first transducer group that does not produce offset residuals is low, but the total offset residual components are reduced, resulting in a slight decrease in the level of ultrasound in deep areas, although this is still practically acceptable. The relationship between the frequency power spectrum of the ultrasound output from the first transducer group and the frequency power spectrum of the ultrasound output from the second transducer group is the preferred relationship shown in Figure 8, as with Example 1, resulting in good penetration.

[0109] The transmission conditions (transmitted ultrasonic waves) in Examples 1 to 3 satisfy conditions (a) to (e).

[0110] <Image evaluation> Ultrasound image data was generated by the ultrasound diagnostic device S based on the transmission conditions and imaging signals of the above-mentioned Comparative Examples 1 to 4 and Examples 1 to 3, and image evaluation of the generated ultrasound image data was performed. The transmission conditions, imaging signals, and image evaluation of Comparative Examples 1 to 4 and Examples 1 to 3 are shown in the following Table II. [Table 2]

[0111] Next, image evaluation of ultrasound images will be described with reference to FIGS. 21(a) to 24(b). FIG. 21(a) is a diagram showing an ultrasound image of a first subject in Comparative Example 4. FIG. 21(b) is a diagram showing an ultrasound image of a first subject in Example 1. FIG. 22(a) is a 3D graph of the brightness values ​​of partial region P1 in FIG. 21(a). FIG. 22(b) is a 3D graph of the brightness values ​​of partial region P2 in FIG. 21(b). FIG. 23(a) is a diagram showing an ultrasound image of a second subject in Comparative Example 4. FIG. 23(b) is a diagram showing an ultrasound image of a second subject in Example 1. FIG. 24(a) is a 3D graph of the brightness values ​​of partial region P3 in FIG. 23(a). FIG. 24(b) is a 3D graph of the brightness values ​​of partial region P4 in FIG. 23(b).

[0112] First, ultrasound image data was generated by scanning the same first subject using the ultrasound diagnostic device S under the transmission conditions and imaging signal conditions of Comparative Examples 1 to 4 and Examples 1 to 3. As the first subject, a custom-made phantom (Cyst depth 1 to 2 cm) was used, which was based on Gammex 404GS as a matrix portion (scatterer material portion) and added with a Cyst portion (small-diameter cyst target (a homogeneous material portion with anechoic components simulating a cyst)).

[0113] In the image evaluation of Table II, "Shallow Cyst Representation" was assigned an X level for the degree of Cyst area reduction and the degree of boundary brightness change in the Cyst area in the ultrasound image of Example 4, and an O level for the degree of Cyst area reduction and the degree of boundary brightness change in Example 1, with the range from X to O being equally divided, and results were assigned based on the results of both items for each.

[0114] The results of cyst visualization were good in Comparative Examples 1 and 2 and Examples 1 to 3, but poor in Comparative Examples 3 and 4.

[0115] 21(a), an ultrasound image of the ultrasound image data of the first subject in Comparative Example 4 was obtained. In this ultrasound image, a region consisting of 80 × 80 pixels including the Cyst region (the black circle in the figure) is defined as partial region P1.

[0116] 21(b), an ultrasound image was obtained based on the ultrasound image data of the same first subject in Example 1. In this ultrasound image, a region consisting of 80 × 80 pixels including the same Cyst region was designated as partial region P2.

[0117] Here, as shown in FIG. 22(a), the brightness values ​​of each pixel in partial region P1 were plotted as a 3D graph. The partial region P1 was set as an XY plane, and the X, Y, and Z axes (all not shown) were set so that the brightness values ​​were plotted on the Z axis. In this way, to improve shape visibility, the brightness values ​​were plotted as a 3D graph with low brightness areas being at high values ​​on the Z axis. Furthermore, as shown in FIG. 22(b), the brightness values ​​of each pixel in partial region P2 were plotted as a 3D graph in the same manner as in FIG. 22(a).

[0118] As shown in the 3D graph of brightness in Fig. 22(a), in partial region P1 of Comparative Example 4, in which asymmetric PI drive signals were output to transducers 2a of all transmitting apertures, the area of ​​low-brightness parts in the Cyst section was reduced and the brightness change at the boundary was also gradual. In contrast, as shown in the 3D graph of brightness in Fig. 22(b), in partial region P2 of Example 1, in which symmetric PI drive signals were output to the first transducer group on the inside of the transmitting aperture and asymmetric PI drive signals were output to the second transducer group on the outside, the area of ​​low-brightness parts was maintained and the brightness change at the boundary was also steep, resulting in clear contrast.

[0119] Next, the same second subject was scanned to generate ultrasound image data using the transmission conditions and imaging signal conditions of Comparative Examples 1 to 4 and Examples 1 to 3 in the ultrasound diagnostic device S. As the second subject, a phantom was used, which was made by solidifying a matrix portion (scatterer material portion) in which 500 μmΦ acrylic particles were dispersed in dissolved agar, and a 1 mmΦ nylon wire was embedded as a shadow source (acoustic shielding material that causes the shadow portion).

[0120] For the "shadow reduction effect" in the image evaluation of Table II, the brightness uniformity (shallow and deep areas) of the matrix and shadow areas of Comparative Example 1 was rated as an × level, the brightness uniformity (shallow area) of Example 1 was rated as an 〇△ level, and the brightness uniformity (deep area) was rated as an 〇 level, with the range from × to 〇 being equally divided and results assigned based on the results of both items for each.

[0121] The shadow reduction effect was good in both shallow and deep areas in Comparative Examples 3 and 4 and Examples 1 to 3, but poor in Comparative Examples 1 and 2 in both shallow and deep areas.

[0122] 23(a), an ultrasound image of the ultrasound image data of the first subject in Comparative Example 4 was obtained. In this ultrasound image, a region consisting of 170 × 120 pixels including a shadow portion (black portion in the figure) is defined as partial region P3.

[0123] 23(b), an ultrasound image was obtained from the ultrasound image data of the same second subject as in Example 1. In this ultrasound image, a region consisting of 170 × 120 pixels including the same shadow portion was designated as partial region P4.

[0124] Here, as shown in FIG. 24(a), the brightness values ​​of each pixel in partial region P3 were plotted as a 3D graph. The partial region P3 was set as an XY plane, and the X, Y, and Z axes (all not shown) were plotted so that the brightness value was plotted on the Z axis. In this way, similar to the Cyst region, in order to improve shape visibility, the brightness values ​​were plotted as a 3D graph with low brightness areas being at high values ​​on the Z axis. Furthermore, as shown in FIG. 24(b), the brightness values ​​of each pixel in partial region P4 were plotted as a 3D graph in the same manner as in FIG. 24(a).

[0125] As shown in the 3D graph of brightness in Fig. 24(b), in partial region P1 of Comparative Example 4, in which asymmetric PI drive signals were output to transducers 2a of all transmission apertures, two streaky shadow portions are recognized as clear brightness differences from shallow to deep regions. In contrast, as shown in the 3D graph of brightness in Fig. 24(b), in partial region P2 of Example 1, in which symmetric PI drive signals were output to the first transducer group on the inside of the transmission aperture and asymmetric PI drive signals were output to the second transducer group on the outside, the brightness difference with the surroundings is greatly reduced in the shallow region (rear of the 3D graph), and it can be seen that the brightness is generally uniform in the deep region (front of the 3D graph).

[0126] For the "Penetraton (rating)" in the image evaluation of Table II, two different frames of ultrasound image data were acquired without time averaging, and the depth at which the image correlation was maintained at 0.5 or more was defined as the Penetraton depth. Results that were roughly equivalent to Example 1 were rated as ◯, results that were roughly equivalent to Comparative Example 1 (inferior to Example 1) were rated as △, and results that were inferior to Comparative Example 1 were rated x. However, there were no results that were rated as x.

[0127] In Examples 1 to 3, the image evaluations of shallow cyst visualization, shadow reduction effect, and penetraton were all satisfactory, reaching practically acceptable levels (good or better). In Examples 1 to 3, high-resolution image visualization was achieved by designing the offset residual components to satisfy conditions (d) and (e). In contrast, in Comparative Example 3, in which the received signals obtained from the transmitted ultrasound were directly imaged to cover the shadow areas, the shadow areas were covered, but were strongly affected by acoustic noise, and the image signal resulting from the low-frequency, narrow-band second transmission and reception result was visualized with a weighting of 50%. This resulted in coarse image granularity and components with poor resolution adversely affecting the entire image, resulting in degradation of, for example, cyst visualization (shallow cyst visualization).

[0128] Furthermore, in Comparative Example 4, which did not separate the transmit aperture into an inner first transducer group and an outer second transducer group and used first and second drive signals that generated cancellation residuals, the shallow Cyst imaging was strongly affected by acoustic noise due to cancellation residual components from shallow areas, resulting in poorer shallow Cyst imaging than in Examples 1 to 3. Furthermore, when the same transmit aperture was set and Example 1 and Example 2, which had a smaller number of elements in the first transducer group that was more inner than Example 1, were compared, Example 1, which was less affected by cancellation residual components of the outer second transducer group, performed better than Example 2 in terms of shallow Cyst imaging. Similarly, Example 2 performed better in terms of shadow reduction effect (shallow areas) than Example 1 because the transmitted ultrasound from the outer second transducer group was more likely to wrap around to the shadow area. In addition, in Example 3, in which the number of elements in the first inner vibration element group and the number of elements in the second outer vibration element group were the same, and the drive waveform of the second outer vibration element group was changed to change the strength of the offset residual component, shallow Cyst imaging improved, but in terms of shadow reduction effect (deep area), Example 2 was better than Example 3 because the proportion of offset residual components to the entire imaging signal decreased.

[0129] As described above, according to this embodiment, an ultrasound diagnostic device S generates ultrasound image data based on reception signals obtained by an ultrasound probe 2 that transmits transmission ultrasound to a subject and receives reception ultrasound from the subject. The ultrasound probe 2 has a transmission aperture composed of multiple transducers 2a. The transmission aperture has multiple transducer groups including at least a first transducer group arranged inside the transmission aperture and a second transducer group arranged outside the first transducer group. The ultrasound diagnostic device S includes a transmission unit 12 that generates drive signals and outputs them to the multiple transducer groups, a control unit 18 that causes the transmission unit 12 to output multiple drive signals, including at least a first drive signal and a second drive signal, to the multiple transducer groups for one acoustic line, a reception unit 13 that receives multiple reception signals corresponding to the multiple drive signals from the ultrasound probe 2, and an image generation unit 14 that generates ultrasound image data by calculating the multiple reception signals. The first drive signal includes a third drive signal and a fourth drive signal. The second drive signal includes a fifth drive signal that cancels out when added to the third drive signal, and a sixth drive signal that generates a cancel-out residue when added to the fourth drive signal. The control unit 18 causes the transmitter 12 to impart a time delay to the first drive signal and the second drive signal so that the transmitted ultrasonic waves are focused at the same focal point, and to output the third drive signal and the fifth drive signal to the first transducer group on the inside, and the fourth drive signal and the sixth drive signal to the second transducer group on the outside.

[0130] Therefore, when an acoustic obstruction is present, the deterioration of the visualization of dark areas due to acoustic noise can be eliminated, and good ultrasound images with high shadow resistance can be obtained. In addition, the third drive signal and the fifth drive signal of the asymmetric PI can improve penetration while maintaining resolution.

[0131] Furthermore, the image generator 14 generates ultrasound image data by adding up the received signals, so that an ultrasound image with high resolution, few artifacts, and good contrast can be obtained due to the harmonic components.

[0132] In addition, the drive voltages of the first drive signal and the second drive signal are the same, which prevents a complex configuration in which drive voltages are set differently for the first drive signal and the second drive signal, and for the first transducer group on the inside and the second transducer group on the outside, thereby simplifying the configuration of the ultrasound diagnostic device S and reducing costs.

[0133] Furthermore, the center frequency of the frequency power spectrum (signal component OTx of asymmetric PI) of the transmitted ultrasound of the fourth drive signal and the sixth drive signal is smaller than the center frequency of the frequency power spectrum (signal component ITx of symmetric PI) of the transmitted ultrasound of the third drive signal and the fifth drive signal. Furthermore, the bandwidth of the frequency power spectrum (signal component OTx of asymmetric PI) of the transmitted ultrasound of the fourth drive signal and the sixth drive signal is smaller than the bandwidth of the frequency power spectrum (signal component ITx of symmetric PI) of the transmitted ultrasound of the third drive signal and the fifth drive signal. Furthermore, in a frequency range higher than the center frequency of the ultrasound probe 2, the signal intensity of the frequency power spectrum (signal component OTx of asymmetric PI) of the transmitted ultrasound of the fourth drive signal and the sixth drive signal is smaller than the signal intensity of the frequency power spectrum (signal component ITx of symmetric PI) of the transmitted ultrasound of the third drive signal and the fifth drive signal. Therefore, it is possible to improve the imaging of shallow aechoic to hypoechoic regions.

[0134] Furthermore, the center frequency of the frequency power spectrum of the transmitted ultrasonic waves of the third drive signal and the sixth drive signal is smaller than the center frequency of the cancellation residual component. Furthermore, the bandwidth of the frequency power spectrum of the transmitted ultrasonic waves of the third drive signal and the sixth drive signal is smaller than the bandwidth of the cancellation residual. Therefore, for shadow areas, the bandwidth is wide, making it possible to obtain images with fine image granularity and high resolution.

[0135] The description of the above embodiment is an example of a suitable ultrasonic diagnostic apparatus according to the present invention, and the present invention is not limited to this.

[0136] For example, in the above embodiment, the transducers 2a of the transmission aperture of the ultrasonic probe 2 are divided into a first transducer group on the inside and a second transducer group on the outside, but this is not limited to this. The transducers 2a of the transmission aperture of the ultrasonic probe 2 may be divided into three or more transducer groups including a first transducer group on the inside and a second transducer group on the outside. Furthermore, in the above embodiment, one transducer group is described as having a plurality of transducers 2a, but this is not limited to this and may be a configuration having at least one transducer 2a.

[0137] Furthermore, the detailed configurations and operations of the components constituting the ultrasonic diagnostic apparatus S in the above-described embodiment may be modified as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0138] S Ultrasound diagnostic equipment 1. Ultrasound diagnostic device 11 Operation input section 12 Transmitter 121 Clock generation circuit 122 Pulse Generator Circuit 123 Time and voltage setting unit 124 Delay Circuit 13 Receiving unit 14 Image generation unit 14a Harmonic component extraction section 15 Image processing section 15a Image memory section 16 DSC 17 Display section 18 Control Unit 19 Memory section 2,2L ultrasonic transducer 21 Ultrasonic probe body 2a Oscillator 22 Cable 23 Connector

Claims

1. An ultrasound diagnostic apparatus that generates ultrasound image data based on a reception signal obtained by an ultrasound probe that transmits transmission ultrasound to a subject and receives reception ultrasound from the subject, the ultrasonic probe has a transmission aperture formed by a plurality of transducers, the transmission aperture has a plurality of transducer groups including at least a first transducer group arranged inside the transmission aperture and a second transducer group arranged outside the first transducer group, The ultrasonic diagnostic device includes: a transmitter that generates a drive signal and outputs it to the plurality of transducer groups; a control unit that causes the transmission unit to output a plurality of drive signals including at least a first drive signal and a second drive signal to the plurality of transducer groups along one acoustic line; a receiving unit that receives a plurality of reception signals corresponding to the plurality of drive signals from the ultrasonic probe; an image generating unit that generates ultrasound image data by calculating the plurality of received signals, the first drive signal includes a third drive signal and a fourth drive signal; the second drive signal includes a fifth drive signal that is canceled when added to the third drive signal, and a sixth drive signal that generates a canceling residual of a linear component when added to the fourth drive signal, the fourth drive signal and the sixth drive signal are asymmetric PI drive signals, the transmitted ultrasonic waves corresponding to the fourth drive signal and the sixth drive signal are low frequency; The control unit causes the transmission unit to apply a time delay to the first drive signal and the second drive signal so that the transmitted ultrasonic waves are focused at the same focal point, and to output the third drive signal and the fifth drive signal to the first group of transducers, and to output the fourth drive signal and the sixth drive signal to the second group of transducers.

2. The ultrasound diagnostic apparatus according to claim 1 , wherein the image generator generates the ultrasound image data by adding up the received signals.

3. 3. The ultrasonic diagnostic apparatus according to claim 1, wherein the first drive signal and the second drive signal have the same drive voltage.

4. 4. The ultrasonic diagnostic device according to claim 1, wherein a center frequency of the frequency power spectrum of the transmitted ultrasonic waves of the fourth drive signal and the sixth drive signal is smaller than a center frequency of the frequency power spectrum of the transmitted ultrasonic waves of the third drive signal and the fifth drive signal.

5. 5. The ultrasonic diagnostic device according to claim 1, wherein a bandwidth of a frequency power spectrum of the transmitted ultrasonic waves of the fourth drive signal and the sixth drive signal is smaller than a bandwidth of a frequency power spectrum of the transmitted ultrasonic waves of the third drive signal and the fifth drive signal.

6. 6. The ultrasound diagnostic device according to claim 1, wherein in a frequency region higher than a center frequency of the ultrasound probe, the signal strength of the frequency power spectrum of the transmitted ultrasound of the fourth drive signal and the sixth drive signal is smaller than the signal strength of the frequency power spectrum of the transmitted ultrasound of the third drive signal and the fifth drive signal.

7. 7. The ultrasonic diagnostic apparatus according to claim 1, wherein the center frequencies of the frequency power spectra of the transmitted ultrasonic waves of the fourth drive signal and the sixth drive signal are smaller than the center frequency of the cancellation residual component.

8. The ultrasonic diagnostic apparatus according to claim 1 , wherein the bandwidth of the frequency power spectrum of the transmitted ultrasonic waves of the fourth drive signal and the sixth drive signal is smaller than the bandwidth of the cancellation residual component.

Images