JP2024054939A - Ultrasonic diagnostic apparatus, ultrasonic image generation method, and program - Google Patents

Abstract

To visualize a scattering component of a variable scattering body, and to prevent deterioration in a frame rate and suppress a scattering component of a fixed scattering body.SOLUTION: An ultrasonic diagnostic apparatus 100A includes: an acoustic ray signal generation unit 14A for generating an acoustic ray signal on the basis of a reception signal obtained from an ultrasonic probe 2 for transmitting/receiving an ultrasonic wave to/from a subject; imaging signal extraction units 15a1-15an for performing filtering passing through a plurality of different bandwidths and generating a plurality of imaging signals from the acoustic ray signal; an imaging signal arithmetic unit 15b for performing mutual calculation for the plurality of imaging signals and generating a mutual calculation imaging signal; and an image signal analysis unit 15c for subtracting the mutual calculation imaging signal from a normal imaging signal generated from the acoustic ray signal to generate a first difference imaging signal, calculating frame correlation in a time direction of the first difference imaging signal, and determining a low correlation part in which the frame correlation is low.SELECTED DRAWING: Figure 2

Description

The present invention relates to an ultrasound diagnostic device, an ultrasound image generation method, and a program.

Ultrasound diagnosis is a simple procedure of placing an ultrasound probe on the surface of the patient's body or inside a body cavity to obtain ultrasound images of the heart or fetus, and is highly safe, so the examination can be performed repeatedly. Ultrasound diagnostic devices used to perform such ultrasound diagnosis are known.

Ultrasound images are usually displayed without distinguishing between echo signal components of reflected ultrasound (echoes) obtained by reflection from structures larger than the ultrasound wavelength and echo signal components obtained by scattering from structures smaller than the ultrasound wavelength. Reflector echo signals from reflectors larger than the ultrasound wavelength are signals that correspond to the shape and structure of the reflector, and are obtained directly as its shape. In contrast, scatterer echo signals from scatterers smaller than the ultrasound wavelength do not directly reflect its shape, since they are smaller than the ultrasound wavelength. Scatterers include scatterers that are fixed in time (referred to as fixed scatterers) contained in fixed tissues such as muscle and fat, and scatterers that fluctuate in time (referred to as variable scatterers) such as blood cells.

Also, B (Brightness) mode and color Doppler mode (color flow mode) are known as image modes for generating ultrasound image data. B mode is a mode in which ultrasound is emitted to the subject and the strength of the received signal is expressed as a B mode image in terms of brightness. Color Doppler mode is a mode in which multiple ultrasound waves are emitted to the same position on the subject and the flow velocity of moving blood flow, etc. is imaged as a color Doppler image based on the received signals. In color Doppler mode, a color Doppler image is displayed superimposed on the ROI (Region Of Interest) of the B mode image. For this reason, color Doppler mode has a lower frame rate than B mode because it transmits and receives ultrasound for B mode and for color Doppler mode.

An ultrasound diagnostic device is also known that synthesizes and displays B-mode image data and B-flow image data that depicts blood flow in B-mode (see Patent Document 1). A B-flow image is an ultrasound image that visualizes blood flow in B-mode by enhancing minute signals from the blood flow. The ultrasound diagnostic device of Patent Document 1 transmits and receives ultrasound for the B-mode image, and transmits and receives ultrasound multiple times for the B-flow image.

JP 2012-19917 A

The ultrasound diagnostic device of Patent Document 1 can visualize blood flow. However, because the ultrasound diagnostic device of Patent Document 1 transmits and receives ultrasound for B-mode images and multiple ultrasound waves for B-flow images, the frame rate of the displayed image is low. Furthermore, in addition to the scattering components of blood cells as variable scatterers, B-flow images also contain scattering components from fixed scatterers. Due to the scattering components from fixed scatterers, B-mode flow images are unclear in subjects with strong intra-tissue scattering, such as elderly people.

The objective of the present invention is to visualize the scattering components of variable scatterers while preventing a decrease in frame rate and suppressing the scattering components of fixed scatterers.

In order to solve the above problems, the ultrasonic diagnostic apparatus according to the present invention comprises:
a first generator that generates a sound ray signal based on a reception signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject;
a second generation unit that performs filtering to pass a plurality of different bands from the sound ray signal to generate a plurality of imaging signals;
a calculation unit that performs a mutual calculation on the plurality of imaging signals to generate a mutual calculation imaging signal;
and an analysis unit that subtracts the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates a frame correlation in the time direction of the first differential imaging signal, and determines low correlation parts where the frame correlation is low.

The ultrasonic diagnostic apparatus according to the second aspect of the present invention comprises:
A first generation unit that performs delay-and-sum under a plurality of different delay-and-sum conditions on a received signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to a subject to generate a plurality of sound ray signals;
a calculation unit that performs a mutual calculation on a plurality of imaging signals based on the plurality of sound ray signals to generate a mutual calculation imaging signal;
and an analysis unit that subtracts the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates a frame correlation in the time direction of the first differential imaging signal, and determines low correlation parts where the frame correlation is low.

The present invention relates to an ultrasonic diagnostic apparatus comprising:
The second generating unit generates a plurality of imaging signals by filtering the plurality of sound ray signals through a plurality of different bands.

The invention according to claim 4 provides the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The analysis section calculates the frame correlation from the first differential imaging signals of a plurality of frames.

The invention according to claim 5 provides the ultrasonic diagnostic apparatus according to claim 4,
The analysis unit calculates the frame correlation from the first difference imaging signal using a threshold determined by machine learning.

The invention described in claim 6 is the ultrasound diagnostic apparatus according to any one of claims 1 to 3,
The first generating unit generates an electrical noise sound ray signal when no ultrasonic waves are transmitted, and subtracts the electrical noise sound ray signal from the sound ray signal.

The invention described in claim 7 is the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The analysis section subtracts the first differential imaging signal from which the low correlation portion has been removed, from the first differential imaging signal to generate a second differential imaging signal.

The invention according to claim 8 provides the ultrasonic diagnostic apparatus according to claim 7,
The image processing unit adds identification information to the second differential imaging signal, and superimposes the second differential imaging signal to which the identification information has been added on the mutual operation imaging signal to generate a superimposed imaging signal.

The invention according to claim 9 provides the ultrasonic diagnostic apparatus according to claim 8,
The image processing device further includes a display control unit that simultaneously and in parallel displays a normal image based on the normal imaging signal and a superimposed image based on the superimposed imaging signal on a display unit.

The invention according to claim 10 provides the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The calculation unit multiplies the plurality of imaging signals as the mutual calculation.

The invention according to claim 11 provides the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The calculation section performs a power root calculation process on the mutual calculation imaging signal in accordance with the plurality of imaging signals.

The invention according to claim 12 provides the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The calculation section performs LUT conversion processing on the mutually calculated imaging signal.

The invention according to claim 13 provides the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The ultrasonic probe has a -20 dB frequency band ratio of 100% or more.

The invention according to claim 14 provides the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
a transmission unit that generates a drive signal including a plurality of fundamental waves having different frequencies and outputs the drive signal to the ultrasonic probe;
The first generating unit generates a sound ray signal having harmonic components of the plurality of fundamental waves.

The invention according to claim 15 provides the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The calculation section sets the luminance value of the mutual calculation imaging signal below a certain value to be zero.

The invention according to claim 16 provides the ultrasonic diagnostic apparatus according to any one of claims 1 to 3,
The imaging signal is image data.

The ultrasonic image generating method according to the seventeenth aspect of the present invention comprises the steps of:
A first step of generating a sound ray signal based on a received signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject;
a second step of filtering the sound ray signals through a plurality of different bands to generate a plurality of imaging signals;
a third step of cross-operating the plurality of imaging signals to generate a cross-operated imaging signal;
and a fourth step of generating a first differential imaging signal by subtracting the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal, calculating a frame correlation in the time direction of the first differential imaging signal, and determining a low correlation portion where the frame correlation is low.

The invention according to claim 18 provides an ultrasonic image generating method, comprising:
A first step of performing delay-and-sum under a plurality of different delay-and-sum conditions on a received signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to a subject to generate a plurality of sound ray signals;
a second step of performing a mutual operation on a plurality of imaging signals based on the plurality of sound ray signals to generate a mutual operation imaging signal;
and a third step of generating a first differential imaging signal by subtracting the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal, calculating a frame correlation in the time direction of the first differential imaging signal, and determining a low correlation portion where the frame correlation is low.

The program of the invention according to claim 19,
Computer,
a first generator that generates a sound ray signal based on a reception signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject;
a second generation unit that performs filtering to pass a plurality of different bands from the sound ray signals to generate a plurality of imaging signals;
a calculation unit that performs a mutual calculation on the plurality of imaging signals to generate a mutual calculation imaging signal;
an analysis unit that subtracts the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates a frame correlation in a time direction of the first differential imaging signal, and determines a low correlation portion where the frame correlation is low;
Function as.

The program of the invention according to claim 20,
Computer,
a first generation unit that performs delay-and-sum under a plurality of different delay-and-sum conditions on a reception signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to a subject, thereby generating a plurality of sound ray signals;
a calculation unit that performs a mutual calculation on a plurality of imaging signals based on the plurality of sound ray signals to generate a mutual calculation imaging signal;
an analysis unit that subtracts the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates a frame correlation in a time direction of the first differential imaging signal, and determines a low correlation portion where the frame correlation is low;
Function as.

The present invention makes it possible to visualize the scattering components of variable scatterers, prevent a decrease in frame rate, and suppress the scattering components of fixed scatterers.

1 is a diagram showing the external configuration of an ultrasonic diagnostic apparatus according to a first embodiment of the present invention; 1 is a block diagram showing a functional configuration of an ultrasound diagnostic apparatus according to a first embodiment; FIG. 2 is a block diagram showing a functional configuration of a transmission unit. 1A is a diagram showing frequency characteristics of the signal strength of a transmitted ultrasonic wave, and FIG. 1B is a diagram showing frequency characteristics of the signal strength of a reflected ultrasonic wave. FIG. 13 is a diagram showing frequency characteristics of signal intensity of first to fourth bands of reflected ultrasound. FIG. 1 shows ultrasound images before and after electrical noise removal. 1A and 1B are diagrams showing ultrasound images before and after scattering component extraction. FIG. 1 shows frame-correlated ultrasound images. 11 is a flowchart showing a first ultrasound image display process. (a) is a diagram showing a normal image before electrical noise removal, (b) is a diagram showing an electrical noise image, (c) is a diagram showing a normal image after electrical noise removal, (d) is a diagram showing a mutual operation image, (e) is a diagram showing a first difference image, and (f) is a diagram showing a first difference image after removal of low correlation parts. 13A is a diagram illustrating the generation of a second difference image, and FIG. 13B is a diagram illustrating the generation of a superimposed image. FIG. 11 is a block diagram showing the functional configuration of an ultrasound diagnostic apparatus according to a second embodiment. 13 is a flowchart showing a second ultrasound image display process. FIG. 13 is a block diagram showing the functional configuration of an ultrasound diagnostic apparatus according to a third embodiment. 13 is a flowchart showing a third ultrasound image display process. 13 is a flowchart showing a fourth ultrasound image display process.

The first to third embodiments of the present invention will be described in detail in order with reference to the attached drawings. Note that the present invention is not limited to the illustrated examples.

(First embodiment)
A first embodiment of the present invention will be described with reference to Figs. 1 to 11(b). First, the device configuration of an ultrasound diagnostic device 100A according to the present embodiment will be described with reference to Figs. 1 to 5. Fig. 1 is a diagram showing the external configuration of the ultrasound diagnostic device 100A according to the present embodiment. Fig. 2 is a block diagram showing the functional configuration of the ultrasound diagnostic device 100A. Fig. 3 is a block diagram showing the functional configuration of the transmission unit 12. Fig. 4(a) is a diagram showing the frequency characteristics of the signal strength of a transmitted ultrasound. Fig. 4(b) is a diagram showing the frequency characteristics of the signal strength of a reflected ultrasound. Fig. 5 is a diagram showing the frequency characteristics of the signal strength of bands B1 to B4 of the reflected ultrasound.

The ultrasound diagnostic device 100A of this embodiment is installed in a medical facility such as a hospital, and generates and displays ultrasound image data (B-mode image data) of a tomographic image of a subject such as a patient. In particular, the ultrasound diagnostic device 100A displays a B-mode image depicting blood cells (blood flow) as variable scatterers in the subject.

As shown in Figs. 1 and 2, the ultrasound diagnostic device 100A includes an ultrasound diagnostic device main body 1A, an ultrasound probe 2, and a puncture needle 3. The ultrasound probe 2 transmits ultrasound (transmitted ultrasound) to a subject such as a living body (not shown), and receives the reflected waves of the ultrasound reflected by the subject (reflected ultrasound: echo). The ultrasound probe 2 has an ultrasound probe main body 21, a cable 22, and a connector 23. The ultrasound probe main body 21 is a header part of the ultrasound probe 2 that transmits and receives ultrasound. The cable 22 is connected between the ultrasound probe main body 21 and the connector 23, and is a cable through which a drive signal for the ultrasound probe main body 21 and a reception signal of ultrasound flow. The connector 23 is a plug connector for connecting to a receptacle connector (not shown) of the ultrasound diagnostic device main body 1A.

The puncture needle 3 is a treatment tool that has a hollow long needle shape and is inserted into a subject such as a patient at an angle determined by a user such as a doctor or technician. The puncture needle 3 can be replaced with one having an appropriate thickness, length, and tip shape depending on the part (target) of the subject to be sampled or the type and amount of medicine to be injected. The puncture needle 3 may be configured to be attached to the ultrasound probe 2 by an adapter. The user inserts the puncture needle 3 into the subject while observing an ultrasound image including blood cells (blood flow) displayed by the ultrasound diagnostic device 100A. Insertion is easy and accurate, especially when there is blood flow near the target. However, the ultrasound diagnostic device 100A is used not only for examinations using the puncture needle 3, but also for examinations without using the puncture needle 3.

The ultrasound diagnostic device main body 1A is connected to the ultrasound probe main body 21 via a connector 23 and a cable 22. The ultrasound diagnostic device main body 1A transmits an electrical drive signal to the ultrasound probe main body 21, causing the ultrasound probe main body 21 to transmit ultrasound to the subject. The ultrasound diagnostic device main body 1A then obtains a reception signal, which is an electrical signal generated by the ultrasound probe 2 in response to the reflected ultrasound from within the subject received by the ultrasound probe main body 21. The ultrasound diagnostic device main body 1A images the internal state of the subject as ultrasound image data based on the reception signal. The communication between the ultrasound diagnostic device main body 1A and the ultrasound probe 2 (ultrasound probe main body 21) may be performed by wireless communication such as UWB (Ultra Wide Band) instead of wired communication via the cable 22.

As shown in FIG. 2, the ultrasonic probe body 21 includes a plurality of transducers 2a made of piezoelectric elements. The transducers 2a are arranged in a one-dimensional array in the azimuth direction, for example. In this embodiment, an ultrasonic 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 electronic scan probe of a linear scanning type is used for the ultrasonic probe 2, but either an electronic scanning type or a mechanical scanning type may be used. Any of a linear scanning type, a sector scanning type, or a convex scanning type may be used.

The ultrasonic probe 2 of this embodiment is not limited in frequency value, but it is preferable that the band characteristic is wideband. In a narrow band, when performing mutual calculation of band division image signals, the correlation difference between the high correlation image signal due to reflecting tissue and the low correlation image signal due to tissue scattering and interference becomes small. For this reason, a sufficient low correlation signal suppression effect cannot be obtained. As a specific bandwidth, it is preferable that the fractional bandwidth is at least 100% or more, and preferably 120% or more, in the -20 dB frequency fractional bandwidth, which is the realistic effective transmission and reception band of the image signal.

As shown in FIG. 2, the ultrasound diagnostic device main body 1A includes, for example, an operation input unit 11, a transmission unit 12, a reception unit 13, a sound ray signal generation unit 14A as a first generation unit, a signal processing unit 15A, a DSC (Digital Scan Converter) 16, an image processing unit 17A, a display unit 18, and a control unit 19A.

The operation input unit 11 has operation elements such as various switches, buttons, a trackball, a mouse, a keyboard, a touchpad, and a multifunction switch for inputting commands from users such as doctors and technicians to start a diagnosis and data such as personal information of the subject. The operation input unit 11 accepts operation inputs from the user via each operation element and outputs the operation signal to the control unit 19A.

The transmission unit 12 is a circuit that, under the control of the control unit 19A, supplies a drive signal, which is an electrical signal, to the ultrasound probe body 21 via a cable 22 and a connector 23 to generate transmitted ultrasound waves in the ultrasound probe 2. 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 124.

The clock generating circuit 121 is a circuit that generates a clock signal that determines the transmission timing and transmission frequency of the drive signal. The pulse generating circuit 122 is a circuit for generating a pulse signal as a drive signal at a predetermined cycle. The pulse generating circuit 122 can generate a drive signal by switching and outputting, for example, three-value (+HV/0 (GND)/-HV) or five-value (+HV/+MV/0 (GND)/-MV/-HV) voltages. 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 and five-value voltages, but is not limited to three and five values and can be set to an appropriate value, but five values or less are preferable. This makes it possible to improve the degree of freedom in controlling the frequency components at low cost, and to obtain a transmission ultrasound with higher resolution.

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 at the same voltage level. That is, the pulse generating circuit 122 outputs a drive signal with a pulse waveform according to 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 made variable, for example, by input operations using the operation input unit 11.

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 2a, and delays the transmission of the drive signal by the set delay time. The transmission beam formed by the transmitted ultrasound based on the delayed drive signal is focused.

The transmitter 12 configured as described above sequentially switches between the multiple transducers 2a to which the drive signal is supplied, shifting them by a predetermined number for each transmission and reception of ultrasound, in accordance with the control of the controller 19A. The transmitter 12 then performs scanning by supplying drive signals to the multiple transducers 2a whose outputs have been selected.

In addition, the transmission unit 12, under the control of the control unit 19A, does not generate a drive signal at each predetermined frame period of a predetermined number of frames for generating ultrasound image data. By not generating a drive signal, the transmission unit 12 does not cause the ultrasound probe 2 to emit a transmission ultrasound (no transmission of ultrasound). In order to remove the electrical noise components contained in the ultrasound image data, an electrical noise sound ray signal containing only electrical noise components is generated by not transmitting ultrasound. Electrical noise is noise generated by thermal noise of the ultrasound diagnostic device 100A, etc., and is depicted as a noise component on the ultrasound image of the ultrasound image data. In this embodiment, an example in which electrical noise removal by not transmitting ultrasound is always performed will be described, but the electrical noise removal may be performed as needed.

In addition, in this embodiment, a pulse inversion method can be implemented to extract harmonic components, which will be described later. That is, when implementing the pulse inversion method, the transmitting unit 12 transmits a first pulse signal and a second pulse signal, which is the polarity inverted first pulse signal, on the same scanning line at a time interval. At this time, the second pulse signal, which is the polarity inverted first pulse signal, may be transmitted by making at least one of the multiple duties of the first pulse signal different. Also, the second pulse signal may be time-inverted from the first pulse signal.

The receiver 13 is a circuit that receives an electrical reception signal from the ultrasonic probe 2 (from the ultrasonic probe body 21 via the cable 22 and connector 23) in accordance with the control of the controller 19A. The receiver 13 generates a reception signal even when ultrasonic waves are not being transmitted in accordance with the control of the controller 19A.

The sound ray signal generating unit 14A is a circuit that generates a sound ray signal from the reception signal received by the receiving unit 13 under the control of the control unit 19A. The sound ray signal generating unit 14A includes, for example, a noise removing unit 14a, a memory 14b, a harmonic component extracting unit 14c, an amplifier, an A/D conversion circuit, and a phasing addition circuit.

The amplifier is a circuit for amplifying the reception signal received by the receiving unit 13 at a predetermined amplification factor set in advance for each individual path corresponding to each transducer 2a. The A/D conversion circuit is a circuit for analog-to-digital conversion (A/D conversion) of the amplified reception signal. The phasing addition circuit is a circuit for generating a digital sound ray signal (sound ray data) from the A/D converted reception signal. The phasing addition circuit adjusts the time phase by giving a delay time to the A/D converted reception signal for each individual path corresponding to each transducer 2a, and adds these (phasing addition) to generate a sound ray signal. The sound ray signal generated by the phasing addition circuit is a sound ray signal containing an ultrasonic image component and an electrical noise component when ultrasonic waves are transmitted, or a sound ray signal containing an electrical noise component when ultrasonic waves are not transmitted. In addition, the sound ray signal generation unit 14A stores and updates the generated electrical noise sound ray signal in the memory 14b at each predetermined frame period.

The noise removal unit 14a is a circuit that removes the electrical noise sound ray signal stored in the memory 14b when ultrasonic waves are not being transmitted from the sound ray signal when ultrasonic waves are being transmitted, in accordance with the control of the control unit 19A. The memory 14b is a volatile storage unit that stores the electrical noise sound ray signal when ultrasonic waves are not being transmitted.

The harmonic component extraction unit 14c extracts harmonic components by performing a pulse inversion method on the sound ray signal from which the electrical noise sound ray signal has been removed, in accordance with the control of the control unit 19A. In this embodiment, the harmonic component extraction unit 14c can extract signal components mainly composed of second harmonics. First, the first and second sound ray signals obtained from the reflected ultrasonic waves corresponding to the two transmitted ultrasonic waves generated from the first pulse signal and the second pulse signal, respectively, are added (combined). Then, the fundamental wave components contained in the added first and second received signals are removed and then filtered, so that the second harmonic components can be extracted. In addition, odd-order harmonic components such as third-order harmonics can be extracted by subtracting the first and second sound ray signals described above and then removing the fundamental wave components with a filter or the like. Furthermore, both the even-order harmonic components obtained by addition and the odd-order harmonic components obtained by subtraction can be used. In this case, the odd-order harmonic received signal may be phase-matched with the even-order harmonic received signal as necessary. Specifically, the odd-order harmonic reception signal and the even-order harmonic reception signal are phase-adjusted using an all-pass filter or the like, and then added (combined) before envelope detection at the sound ray signal stage. This combines the frequency bands of the even-order harmonic reception signal and the odd-order harmonic reception signal, making it possible to obtain a sound ray signal with a wider bandwidth.

For example, the transmitter 12 generates a drive signal for transmitting ultrasonic waves including fundamental waves f1, f2, and f3 as shown in FIG. 4(a). In FIG. 4(a), the horizontal axis indicates frequency, the vertical axis indicates the signal strength (sensitivity) of the transmitted ultrasonic waves, and the thick solid line indicates the frequency band of the ultrasonic probe 2. The same is true for the diagram of the signal strength of the reflected ultrasonic waves in FIG. 4(b).

The harmonic components of the reflected ultrasound corresponding to the transmitted ultrasound of fundamental waves f1, f2, and f3, which are frequency components of the received signal obtained by the receiving unit 13 and the sound ray signal generating unit 14A, are as shown in FIG. 4(b). In other words, the harmonic components of the reflected ultrasound are frequency components of f3-f2, f2-f1, f3-f1, 2f1, f1+f2, and 3f1, which are derived from at least one of the fundamental waves f1, f2, and f3. The sound ray signal generating unit 14A generates a sound ray signal that includes all the frequency components shown in FIG. 4(b).

The signal processing unit 15A has imaging signal extraction units 15a1 to 15an (n: natural number of 2 or more) as a second generation unit, an imaging signal calculation unit 15b as a calculation unit, an image signal analysis unit 15c as an analysis unit, and a memory 15d. The signal processing unit 15A generates first to nth imaging signals extracted in n frequency bands from the sound ray signal input from the sound ray signal generation unit 14A according to the control of the control unit 19A. The signal processing unit 15A also performs calculations such as mutual calculation on the first to nth imaging signals to generate mutual calculation imaging signals. The signal processing unit 15A also performs analysis processing using normal imaging signals of normal images (images before mutual calculation is performed) that do not undergo mutual calculation, and mutual calculation imaging signals.

The imaging signal extraction units 15a1 to 15an are circuits equipped with first to nth band pass filters that transmit reception signals of the first to nth frequency bands, respectively. The imaging signal extraction units 15a1 to 15an extract the first to nth imaging signals from the sound ray signals input from the harmonic component extraction unit 14c under the control of the control unit 19A. The first to nth imaging signals are sound ray signals for imaging into B-mode images. For example, the imaging signal extraction unit 15a1 outputs a first imaging signal that has passed through the frequency components of the frequency band (full band) of the ultrasound probe 2 by the first band pass filter. The imaging signal extraction units 15a2 to 15an output second to nth imaging signals that have passed through the frequency components of a frequency band smaller than the full band by the second to nth band pass filters, respectively. The first imaging signal has the highest content of high frequency components. The conditions for extracting the first to nth imaging signals from the sound ray signal are designated as the first to nth imaging conditions.

The blocking characteristics of the multiple different band pass filters of the imaging signal extraction units 15a1 to 15an are appropriately determined for each type of ultrasound probe 2 depending on its acoustic characteristics and the object of observation. However, multiple combinations of blocking characteristics may be prepared. The blocking characteristics may be selected from the multiple combinations in a manner that automatically selects the blocking characteristics in conjunction with the selection of the object of observation (such as a part of the subject) by the user via the operation input unit 11, that detects features from the imaging signal and automatically selects adaptively based on the evaluation value, or that the user selects and inputs the blocking characteristics via the operation input unit 11 as necessary. In this way, the blocking characteristics may be selected automatically or manually. Furthermore, these band pass filters may not be fixed filters, but may be so-called dynamic filters whose blocking characteristics change continuously depending on the depth.

For example, n = 4. In the imaging signal extraction unit 15a1, filtering is performed from the input sound ray signal by a first band pass filter of band B1 shown in FIG. 5 to generate a first imaging signal. Band B1 shown by a thick solid line in FIG. 5 is a band (full band) that passes all frequency components of the frequency band of the ultrasound probe 2. Here, the imaging signal corresponding to band B1 of the full band extracted by the imaging signal extraction unit 15a1 corresponds to a normal image (normal B-mode image) and is called a normal imaging signal. However, the imaging signal generated by the sound ray signal generation unit 14A when filtering is not performed by the imaging signal extraction units 15a1 to 15an may be called a normal imaging signal.

The imaging signal extraction unit 15a2 filters the input sound ray signal with a second band pass filter of band B2 shown in FIG. 5 to generate a second imaging signal. Band B2 is shown by a dotted line in FIG. 5 and is a low frequency band. The imaging signal extraction unit 15a3 filters the input sound ray signal with a third band pass filter of band B3 shown in FIG. 5 to generate a third imaging signal. Band B3 shown by a dotted line in FIG. 5 is a band with a higher frequency than band B2. The imaging signal extraction unit 15a4 filters the input sound ray signal with a fourth band pass filter of band B4 shown in FIG. 5 to generate a fourth imaging signal. Band B4 shown by a dotted line in FIG. 5 is a band with a higher frequency than band B3.

The imaging signal calculation unit 15b performs a mutual calculation on the first to n-th imaging signals generated by the imaging signal extraction units 15a1 to 15an according to the control of the control unit 19A. The imaging signal calculation unit 15b generates a mutual calculation imaging signal by the mutual calculation. The mutual calculation is a calculation that uses the difference in correlation when the frequency changes for multiple ultrasound images to suppress the scattered components corresponding to the ultrasound scattered by the scattering source (microscatterer) of the subject. In addition, in the mutual calculation, the reflected components corresponding to the ultrasound reflected by the tissue (reflector) of the subject are left. In addition, when the brightness correlation of the same point (same position) of multiple ultrasound images is high, the reflected components of the high brightness part appear, and when the brightness correlation of the same position is low, the scattered components of the low brightness part appear. For this reason, the mutual calculation utilizes this to suppress the scattered components of the low brightness part, and suppression by "multiplication" with a light processing load is a preferable mode. The multiplication of the first to n-th imaging signals is a process of multiplying the brightness values corresponding to the pixels at the same position of each B-mode image of the first to n-th imaging signals. Therefore, if even one of the luminance values corresponding to a pixel at the same position in the first through nth imaging signals is 0 (corresponding to black), the multiplication result will be 0.

The imaging signal calculation unit 15b also performs a gradation adjustment restoration process on the generated mutual operation imaging signal according to the control of the control unit 19A. The gradation adjustment restoration process is, for example, a power root calculation process or a LUT (Look Up Table) conversion process. When multiplication is used for the mutual operation, if the multiplication value is directly converted to a luminance value, only the high luminance part is emphasized, resulting in an image with deteriorated tissue visibility, so it is preferable to perform the gradation adjustment restoration process. Specifically, it is possible to perform a relatively simple gradation reduction by performing a power root calculation process according to the number of mutual operation images. For example, the power root calculation process is a cube root calculation on the multiplication value if the number of multiplication images is 3, or a fourth root calculation if n=4 and the number of multiplication images is 4 as shown in FIG. 5. The gradation adjustment restoration process may also be a method in which a gradation adjustment restoration process is performed by applying a corresponding LUT without performing sequential calculations and performing a LUT conversion process. This LUT is assumed to be generated in advance and stored in a storage unit (not shown) such as the ROM (Read Only Memory) of the control unit 19A, or a hard disk drive (HDD) or solid state drive (SSD) of the ultrasound diagnostic device 100A.

The LUT is, for example, a table showing the output signal [%] relative to the input signal [%]. As a specific example, the LUT converts an input signal of 0-4 [%] into an output signal of 0 [%], and 4-100 [%] into an output signal of 0-100 [%]. This LUT sets any brightness value of the mutually-operated imaging signal below a certain value (4%) to 0.

The image signal analysis unit 15c analyzes the mutual operation imaging signal calculated by the imaging signal calculation unit 15b according to the control of the control unit 19A. This analysis includes a process of taking the difference between the normal imaging signal (full-band first imaging signal) and the mutual operation imaging signal to generate a first differential imaging signal of a differential image. This process of taking the difference of the imaging signals is a process of subtracting the brightness value corresponding to the pixel at the same position of the mutual operation image of the mutual operation imaging signal from the brightness value of each pixel of the normal image of the normal imaging signal. The first differential image of the first differential imaging signal is an image that depicts the scattered components.

The above analysis also includes a process of calculating the correlation (frame correlation) in the time direction between multiple frames of the first differential imaging signal and removing scattered components in low-correlation parts with low frame correlation. Here, the frame correlation (correlation coefficient) in this embodiment will be described. The correlation coefficient refers to the pixel-by-pixel, 1D, or 2D correlation or cross-correlation (as a whole) between two or more frames of collected ultrasound information. For example, the discrete time signals of two or more frames are captured and cross-correlated, and the correlation coefficient is calculated. The number of frames required is two or more consecutive frames. There is no upper limit to the number of frames, but in order to reduce the influence of body movement, it is preferable to set it to 10 frames or less, and at most the number of frames acquired per second or less. In other words, if the frame rate is 30 fps, it is preferable to set it to 30 frames or less.

There is no particular limitation on the method of calculating the correlation, and any suitable application and/or algorithm well known in the art can be used. For example, see Proakis and Manolakis, Digital Signal Processing, 4th Edition, Pearson 2007, Oppenheim, Alan V. and Ronald W. Schafer. Discrete-time signal processing. Pearson Higher Education, 2010, and MIT OpenCourseWare, 2.161 Signal processing: Continuous and Discrete, https://ocw.mit. edu/courses/mechanical-engineering/2-161-signal-processing-continuous-and-discrete-fall-2008/lecture-notes/lecture_22.pdf (Fall 2008) may be utilized. If necessary, the correlation coefficient between frames may be determined by evaluating the lag or difference between two or more signals of the frames using an existing multiplication and addition correlation method. The threshold value set for the correlation coefficient is appropriately selected depending on the calculation method of the correlation coefficient and the observation site to be applied. However, it may be set in advance in association with the observation site, etc., or may be selectable by the user. When it is set in advance in association with the observation site, etc., a method of determining these threshold values using machine learning may be used.

In addition, when calculating the correlation coefficient using many frames, a method of using displacement calculation in combination may be used to reduce the influence of positional deviation due to body movement. For example, one-dimensional or two-dimensional correlation calculation processing is performed on two frames (two frame data) consisting of a pair of a current frame and each past frame. As a result, a displacement vector indicating the displacement of the tissue at each measurement point in the frame (in the frame data), i.e., in the tomographic image, is derived, i.e., a one-dimensional or two-dimensional displacement vector related to the direction and magnitude of the displacement. As a result, a displacement frame indicating the distribution of displacement vectors at multiple measurement points in the frame (in the tomographic image) is formed. In deriving the displacement vector, for example, a block matching method or the like is used. In the block matching method, first, the frame, i.e., the tomographic image, is divided into multiple blocks, each block consisting of several pixels vertically and several pixels horizontally. Then, for each block, a block most similar to the block in one frame is searched for in the other frame. As a result, the displacement between time phases (between two frames) is calculated for each measurement point (each block) in each frame, and, for example, a two-dimensional displacement vector is obtained. In addition, the search results for multiple blocks may be referenced and predictive coding, i.e., processing to determine sample values based on differences, may be performed to obtain displacement vectors for each measurement point.

The machine learning used as necessary in this embodiment refers to that performed using a so-called neural network. A neural network is composed of three layers: an input layer, an output layer, and an intermediate layer (also called a hidden layer, a layer between the input layer and the output layer). Neural network learning can be divided into supervised learning, in which the network is optimized for a problem by inputting teacher data (correct answers), and unsupervised learning, which does not require teacher data. Either method may be used in this embodiment, but supervised learning is preferred in terms of learning efficiency, etc.

The scattering components of the low correlation portion are scattering components that vary over time, and include scattering components of fluctuating scatterers such as blood cells. Of the first differential imaging signals as collected ultrasound information, a predetermined number of consecutive frames including the latest frame are stored in memory 15d. Then, frame correlation of the first differential imaging signals is calculated from the predetermined number of frames of the first differential imaging signals stored in memory 15d. As described above, the predetermined number of frames is the number of image frames required for calculating frame correlation. Low correlation portions with low frame correlation are determined from the predetermined number of frames of the first differential imaging signals. Note that when machine learning is used for the frame correlation calculation, low correlation portions are determined from the predetermined number of frames of the first differential imaging signals using a correlation coefficient threshold determined in advance by machine learning.

Then, the determined low correlation portion is removed from the latest first differential imaging signal. The first differential imaging signal from which the low correlation portion has been removed contains scattering components from fixed scatterers such as fixed tissue, but does not contain scattering components from variable scatterers such as blood cells. Furthermore, the first differential imaging signal from which the low correlation portion has been removed is subtracted from the latest first differential imaging signal to generate a second differential imaging signal. The second differential imaging signal does not contain scattering components from fixed scatterers, but does contain scattering components from variable scatterers.

The above analysis may include a process of generating an index value based on a first difference image of the generated first difference imaging signal. The index value based on this difference image is, for example, information for diagnosing the subject patient. A specific example of the index value based on the difference image is, for example, statistical information such as the difference average value and difference value variance of the difference values in a region of interest (ROI) set by the user via the operation input unit 11. A plurality of regions of interest (ROI) may be set, and the ratio of the statistical values (difference average value, difference value variance) in the plurality of regions of interest (ROI) may be used. By displaying this index value, the user can know the amount and ratio of the scattered components in the region of interest. In addition, this index value is expected to be used as information such as the amount of intramuscular fat for each part of skeletal muscle, and may be used to evaluate the effectiveness of rehabilitation by tracking the progress of the same part.

Memory 15d is a volatile storage unit that stores the first differential imaging signal for at least a predetermined number of frames.

The method of transmitting and receiving ultrasound to generate a B-mode image to which the present invention is applied is not particularly limited to the harmonic imaging mode described above, but is preferably a method capable of receiving a wide band with high contrast. Specifically, it is preferable to use harmonic imaging, which is less likely to generate artifacts such as side lobes due to the sound pressure dependence of harmonic generation and can obtain a high-contrast image signal. In particular, it is preferable to use the methods described in Patent Publication Nos. 6326716, 6443217, and 6540838, which can obtain a wide band of received signals from shallow to deep areas. This makes it possible to obtain a wide band of received signals from shallow to deep areas, and maintain a high low-correlation signal suppression effect by mutual calculation of multiple images obtained by band division.

The DSC 16 generates B-mode image data for display from the imaging signal input from the signal processing unit 15A according to the control of the control unit 19A. First, the DSC 16 performs envelope detection processing, logarithmic compression, etc. on the input normal imaging signal, first differential imaging signal, and second differential imaging signal, and adjusts the dynamic range and gain to convert the luminance. Then, the DSC 16 performs polar coordinate conversion and display pixel interpolation calculation as necessary on the image data generated by the luminance conversion to generate B-mode image data for display. The B-mode image data for display is normal image data corresponding to the normal imaging signal, first differential image data corresponding to the first differential imaging signal, and second differential image data corresponding to the second differential imaging signal.

The image processing unit 17A is a circuit that performs image processing on the normal image data, the first differential image data, and the second differential image data input from the DSC 16 under the control of the control unit 19A. The image processing unit 17A has a display image processing unit 17a that functions as a processing unit and a display control unit.

The display image processing unit 17a, under the control of the control unit 19A, colors the second differential image data input from the DSC 16 with a predetermined color as identification information. The display image processing unit 17a also superimposes the colored second differential image data on the second differential image data input from the DSC 16 to generate superimposed image data. The display image processing unit 17a further displays a superimposed image of the generated superimposed image data on the display unit 18. The display image processing unit 17a can also display the superimposed image and a normal image of the normal image data input from the DSC 16 side by side on the display unit 18.

The display unit 18 can be a display device such as an LCD (Liquid Crystal Display), a CRT (Cathode-Ray Tube) display, an organic EL (Electronic Luminescence) display, an inorganic EL display, or a plasma display. The display unit 18 displays display information input from the control unit 19A according to the control of the control unit 19A, and also displays ultrasound images and the like on the display screen according to a display signal of image data input from the image processing unit 17A.

The control unit 19A includes, for example, a CPU (Central Processing Unit), a ROM, and a RAM (Random Access Memory). The control unit 19A reads out various processing programs such as a system program stored in the ROM, expands them in the RAM, and controls each part of the ultrasound diagnostic device 100A according to the expanded programs. The ROM is composed of non-volatile memory such as a semiconductor, and stores the system program corresponding to the ultrasound diagnostic device 100A, various processing programs that can be executed 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 according to the program code. The ROM stores, in particular, a first ultrasound image display program for executing a first ultrasound image display process described later. The RAM forms a work area that temporarily stores various programs executed by the CPU and data related to these programs.

For each part of the ultrasound diagnostic device main body 1A, some or all of the functions of each functional block can be realized as a hardware circuit such as an integrated circuit. An integrated circuit is, for example, an LSI (Large Scale Integration), and an LSI can be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. In addition, the method of integration is not limited to an LSI, and may be realized by a dedicated circuit or a general-purpose processor, or may use an FPGA (Field Programmable Gate Array) or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI. In addition, some or all of the functions of each functional block may be executed by software. In this case, the software is stored in one or more storage media such as a ROM, an optical disk, or a hard disk, and the software is executed by a processor.

Now, referring to Figs. 6 to 8, an overview of the processing performed on the ultrasound image signals (sound ray signals, imaging signals) in this embodiment will be described. Fig. 6 is a diagram showing ultrasound images I11, I12, and I13 before and after electrical noise removal. Fig. 7 is a diagram showing ultrasound images I21, I22, and I23 before and after scattering component extraction. Fig. 8 is a diagram showing ultrasound images I31, I32, and I33 for which frame correlation is performed.

As described above, the sound ray signal generating unit 14A removes electrical noise from the sound ray signal. As shown in FIG. 6, first, an ultrasound image of the ultrasound image data generated by the sound ray signal generating unit 14A and visualized using the sound ray signal before electrical noise removal is defined as ultrasound image I11. The subject in FIG. 6 is a patient, and the black circles correspond to blood cells (blood flow, blood flow).

Ultrasound image I11 is a B-mode image of B-mode image data obtained by ultrasound transmission and reception to and from the subject by ultrasound probe 2. Ultrasound image I11 includes fixed acoustic scattering components, variable acoustic scattering components, and electrical noise components. Fixed acoustic scattering components are scattering components rendered by acoustic scattering of fixed scatterers contained in fixed tissues such as muscle and fat of the subject. Fixed acoustic scattering components are scattering components rendered by acoustic scattering of scattering components rendered by variable scatterers such as blood cells of the subject. Electrical noise components are noise components rendered due to the generation of electrical noise.

Ultrasound image I12 is a B-mode image of B-mode image data obtained by ultrasound non-transmission and reception of ultrasound by ultrasound probe 2 at approximately the same time as the ultrasound transmission and reception of ultrasound image I11. More specifically, ultrasound image I12 is a B-mode image obtained at a time corresponding to within a predetermined number of frames from the ultrasound transmission and reception of ultrasound image I11. Ultrasound image I12 includes electrical noise components.

Ultrasound image I13 is a B-mode image obtained by subtracting ultrasound image I12 from ultrasound image I11. Therefore, ultrasound image I13 includes a fixed acoustic scattering component and a variable acoustic scattering component. One of the objectives of this embodiment is to extract and visualize the variable acoustic scattering component (scattering component of variable scatterers) corresponding to blood cells. Therefore, a process is required to further extract the scattering component from the sound ray signal of ultrasound image I13 and remove the variable acoustic scattering component (scattering component of variable scatterers).

As shown in FIG. 7, ultrasound image I21 is a B-mode image of the subject corresponding to the full-band first imaging signal generated by the imaging signal extraction unit 15a1 of the signal processing unit 15A. The subject in FIG. 7 is pork. Furthermore, ultrasound image I21 and ultrasound images I22 and I23, which will be described later, are not subjected to electrical noise removal in the sound ray signal generation unit 14A.

The ultrasound image I22 is a B-mode image of the subject corresponding to the mutual operation imaging signal generated by the imaging signal calculation unit 15b of the signal processing unit 15A. This mutual operation imaging signal is generated using the first to nth imaging signals including the first imaging signal of the ultrasound image I21. Compared to the ultrasound image I21, the scattered components of the ultrasound image I22 are suppressed.

Ultrasound image I23 is a B-mode image of the subject corresponding to the first differential imaging signal generated by image signal analysis unit 15c. More specifically, ultrasound image I23 is a B-mode image corresponding to the first differential imaging signal obtained by subtracting the mutual operation imaging signal of ultrasound image I22 from the first imaging signal of ultrasound image I21. Compared to ultrasound image I21, ultrasound image I23 depicts only scattered components.

Ultrasound image I23 includes a fixed acoustic scattering component, a variable acoustic scattering component, and an electrical noise component. If the electrical noise component can be removed from ultrasound image I23 as shown in FIG. 6, and the fixed acoustic scattering component can also be removed, the variable acoustic scattering component can be extracted and depicted.

As shown in FIG. 8, ultrasound image I31 is a B-mode image of the subject corresponding to the first differential imaging signal generated by image signal analysis unit 15c. However, for clarity of explanation, it is assumed that the annular dotted line portion contains blood flow (blood vessels) containing blood cells of the subject. Furthermore, it is assumed that ultrasound image I31 and ultrasound images I32 and I33 described below have not been subjected to electrical noise removal in sound ray signal generation unit 14A.

Ultrasound image I31 includes fixed acoustic scattering components, fluctuating acoustic scattering components, and electrical noise components. The fixed acoustic scattering components do not fluctuate in the time direction and have high frame correlation. The fluctuating acoustic scattering components and electrical noise components fluctuate in the time direction and have low frame correlation. As shown in Figure 6, if the electrical noise components can be removed from ultrasound image I31 and the low frame correlation components can be suppressed, it is possible to first visualize only the fixed acoustic scattering components.

Ultrasound image I32 is a B-mode image of the same subject corresponding to the first differential imaging signal generated one frame before ultrasound image I31. Ultrasound image I33 is a B-mode image of the same subject corresponding to the first differential imaging signal generated two frames before ultrasound image I31. The frame correlation of ultrasound images I31 to I33 is calculated, and low correlation parts of the image of ultrasound image I31, where the frame correlation is low, are determined and removed. This generates a first differential imaging signal of an ultrasound image that depicts only the fixed acoustic scattering components, excluding the electrical noise components.

Furthermore, by subtracting the first differential image signal depicting only the fixed acoustic scattering components from the first imaging signal of ultrasound image I31 from which the electrical noise components have been removed, a second differential imaging signal of an ultrasound image depicting only the variable acoustic scattering components is obtained. The variable acoustic scattering components (blood cells) depicted in the second differential imaging data of the second differential imaging signal are colored with a predetermined color other than grayscale (e.g., light pink). By coloring, the blood cells (blood flow) can be more clearly identified. Furthermore, the colored second differential image data is superimposed on the mutual operation image data of the mutual operation image signal after the gradation adjustment recovery process. By this superposition, image data in which the blood cells (blood flow) are clear and the scattering components are suppressed can be generated.

Next, the operation of the ultrasound diagnostic device 100A will be described with reference to Figs. 9 to 11(b). Fig. 9 is a flowchart showing the first ultrasound image display process. Fig. 10(a) is a diagram showing a normal image I41 before electrical noise removal. Fig. 10(b) is a diagram showing an electrical noise image I42. Fig. 10(c) is a diagram showing a normal image I43 after electrical noise removal. Fig. 10(d) is a diagram showing a mutual operation image I44. Fig. 10(e) is a diagram showing a first difference image I45. Fig. 10(f) is a diagram showing a first difference image I46 after removal of low correlation parts. Fig. 11(a) is a diagram showing the generation of a second difference image I47. Fig. 11(b) is a diagram showing the generation of a superimposed image I49.

First, the first ultrasound image display process executed by the ultrasound diagnostic device 100A will be described with reference to FIG. 9. The first ultrasound image display process is a process for generating a mutual operation imaging signal or the like from imaging signals of multiple ultrasound images with different imaging conditions, and displaying a mutual operation image depicting blood flow.

The control unit 19A accepts in advance various setting information for ultrasound image display from users such as doctors and engineers via the operation input unit 11. The input setting information is stored in the RAM or memory unit (not shown) of the control unit 19A. The input setting information includes content information of the gradation adjustment restoration process to be performed on the mutual operation image (mutual operation imaging signal), setting information on whether or not to remove electrical noise from the ultrasound image, and setting information on whether or not to display a normal image and a superimposed image, which will be described later, in parallel. Note that here, the setting information for removing electrical noise is stored in the RAM or memory unit, and a first ultrasound image display process for removing electrical noise is described. However, in the first ultrasound image display process, if electrical noise removal is not necessary, a step related to electrical noise removal may not be executed.

In the ultrasound diagnostic device 100A, for example, a user inputs an instruction to execute the first ultrasound image display process via the operation input unit 11. The execution instruction triggers the control unit 19A to execute the first ultrasound image display process according to the first ultrasound image display program stored in the ROM.

As shown in FIG. 9, first, the control unit 19A determines whether the next frame for generating a sound ray signal is a predetermined frame period (step S11). The predetermined frame period is a period of a predetermined number of frames that indicates the timing for generating an electrical noise sound ray signal. If it is a predetermined frame period (step S11; YES), the control unit 19A causes the receiving unit 13 to generate a received signal (for one frame) (step S12). In step S12, the control unit 19A further causes the sound ray signal generating unit 14A to amplify, A/D convert, and phase-match and add the generated received signal to generate an electrical noise sound ray signal. In step S12, since no ultrasonic wave is transmitted, only electrical noise components are included in the electrical noise sound ray signal.

Then, the control unit 19A stores (updates) the electrical noise sound ray signal generated in step S12 in the memory 14b (step S13). The control unit 19A then determines whether or not to end the first ultrasound image display process based on the presence or absence of an end instruction input from the user via the operation input unit 11 (step S14). The end instruction input is, for example, an input to end the first ultrasound image display process or to freeze. In the case of a freeze input, the cine data at the time of freezing (for example, superimposed image data of multiple frames displayed in steps S31 and S32 described later) is displayed, selected, held, etc.

If the process is not to be terminated (step S12; NO), the process proceeds to step S11. If the process is to be terminated (step S12; YES), the first ultrasound image display process is terminated.

If it is not the specified frame period (step S11; NO), the control unit 19A causes the transmission unit 12 to generate a drive signal for tissue harmonic imaging (for one frame) (step S15). The drive signal is a drive signal for pulse inversion, and includes the three fundamental wave components shown in FIG. 4(a). The drive signal in step S15 causes the ultrasound probe 2 to transmit ultrasound waves corresponding to the drive signal to the subject.

Then, the control unit 19A causes the receiving unit 13 to receive the reflected ultrasound that is the ultrasound transmitted in step S15 and reflected and scattered by the subject, and generate a received signal (step S16). In step S16, the control unit 19A further causes the sound ray signal generating unit 14A to perform amplification, A/D conversion, and phasing addition on the generated received signal. The sound ray signal that has been subjected to phasing addition contains three fundamental wave components and a harmonic component.

Then, the control unit 19A causes the noise removal unit 14a to remove the electrical noise sound ray signal stored in the memory 14b from the sound ray signal generated in step S16 (step S17). The control unit 19A then causes the harmonic component extraction unit 14c to extract harmonic components from the sound ray signal generated in step S17 using the pulse inversion method (step S18). Step S18 generates a sound ray signal from which the harmonic components have been extracted.

Then, the control unit 19A causes the imaging signal extraction unit 15a1 to generate a first imaging signal (normal imaging signal) from the sound ray signal generated in step S18 (step S19). In step S19, the imaging signal extraction unit 15a1 passes the sound ray signal through a first band-pass filter that passes a predetermined frequency band (full band) as the first imaging condition.

In parallel with step S19, the control unit 19A causes the imaging signal extraction unit 15a2 to generate a second imaging signal from the sound ray signal generated in step S18 (step S20). In step S20, the imaging signal extraction unit 15a2 passes the sound ray signal through a second band pass filter that passes a predetermined frequency band as the second imaging condition. Similarly, in parallel with step S19, the control unit 19A causes the imaging signal extraction units 15a3 to 15a(n-1) to generate third to (n-1)th imaging signals. In parallel with step S19, the control unit 19A causes the imaging signal extraction unit 15an to generate an nth imaging signal from the sound ray signal generated in step S18 (step S21). In step S21, the imaging signal extraction unit 15an passes the sound ray signal through an nth band pass filter that passes a predetermined frequency band as the nth imaging condition.

Then, the control unit 19A causes the imaging signal calculation unit 15b to perform mutual calculation on the first to nth imaging signals generated in steps S19 to S21 (step S21). In step S21, a mutual calculation imaging signal is generated. The mutual calculation here is assumed to be a multiplication of the first to nth imaging signals.

Then, the control unit 19A causes the imaging signal calculation unit 15b to perform a gradation adjustment restoration process corresponding to the setting information on the mutual calculation imaging signal generated in step S22 (step S23). This setting information is setting information stored in the RAM or memory unit (not shown) of the control unit 19A. This gradation adjustment restoration process is a gradation adjustment restoration process using a power root calculation process, a LUT conversion process, etc.

Then, the control unit 19A causes the image signal analysis unit 15c to subtract the mutual operation imaging signal generated in step S23 from the first imaging signal generated in step S19 (step S24). This subtraction generates a first differential imaging signal from which the scattered components are extracted. In step S24, the control unit 19A further causes the image signal analysis unit 15c to store the generated first differential imaging signal in the memory 15d. The first differential imaging signals for at least the immediately preceding predetermined number of frames are stored in the memory 15d in a FIFO (First In First Out) manner.

Then, the control unit 19A causes the image signal analysis unit 15c to calculate the frame correlation of the first differential imaging signal of the predetermined number of frames read out from the memory 15d (step S25). The first differential imaging signal of the predetermined number of frames includes the new first differential imaging signal generated in the immediately preceding step S24. In step S24, the control unit 19A further causes the image signal analysis unit 15c to determine low correlation parts of the frame correlation of the first differential imaging signal and remove the low correlation parts from the first differential imaging signal.

Then, the control unit 19A causes the image signal analysis unit 15c to subtract the first differential imaging signal after removing the low correlation portion generated in step S25 from the first differential imaging signal (step S26). This subtraction generates a second differential imaging signal in which the scattering components of fixed scatterers are suppressed and the scattering components of variable scatterers are extracted.

Then, the control unit 19A causes the DSC 16 to generate image data from the first imaging signal, the mutual operation imaging signal after the gradation adjustment recovery process, and the second difference imaging signal (step S27). The first image data (normal image data) is generated from the first imaging signal generated in step S19. The mutual operation imaging signal after the gradation adjustment recovery process generated in step S23 generates mutual operation image data. The second difference image data is generated from the second difference imaging signal generated in step S26.

Then, the control unit 19A causes the display image processing unit 17a to color the second difference image data generated in step S27 with a predetermined color (step S28). The control unit 19A then causes the display image processing unit 17a to superimpose the second difference image data, which has also been generated after coloring, on the mutual calculation image data generated in step S27 (step S29). This superimposition generates superimposed image data in which the scattered components (blood flow) of the fixed scatterers are colored on the mutual calculation image from which the scattered components have been extracted.

Then, the control unit 19A determines whether or not to display the normal image of the normal image data and the superimposed image of the superimposed image data side by side based on the setting information (step S30). This setting information is setting information stored in the RAM or memory unit (not shown) of the control unit 19A. If displaying side by side (step S30; YES), the control unit 19A arranges the normal image and the superimposed image side by side and displays them on the display unit 18 (step S31), and proceeds to step S14. In step S31, the normal image of the normal image data generated in step S27 and the superimposed image of the superimposed image data generated in step S29 are arranged side by side. In addition, the normal image and the superimposed image are arranged side by side, for example, in the left-right direction or the up-down direction.

If parallel display is not required (step S30; NO), the control unit 19A causes the display unit 18 to display the superimposed image of the superimposed image data generated in step S29 (step S32), and proceeds to step S14.

Next, with reference to Figs. 10(a) to 11(b), examples of images of each image data generated in the first ultrasound image generation and display process will be described. As shown in Fig. 10(a), the ultrasound image corresponding to the sound ray signal generated in step S16 is a normal image I41 before electrical noise removal. The normal image I41 before electrical noise removal is a full-band B-mode image. In the normal image I41 before electrical noise removal, the subject is a specified patient, and the approximately elliptical black portion is the blood vessel portion.

As shown in FIG. 10(b), the ultrasound image corresponding to the electrical noise sound ray signal generated in step S12 immediately before the generation of normal image I41 is electrical noise image I42. As shown in FIG. 10(c), the ultrasound image corresponding to the first imaging signal after electrical noise removal generated in step S19 is normal image I43 after electrical noise removal. Normal image I43 after electrical noise removal is an ultrasound image obtained by subtracting electrical noise image I42 from normal image I41 before electrical noise removal.

As shown in FIG. 10(d), the ultrasound image corresponding to the mutual operation imaging signal after the step-adjustment restoration process generated in step S23 is the mutual operation image I44. The mutual operation image I44 is an ultrasound image that has been subjected to the step-adjustment restoration process (power root) after mutual operation (multiplication) between the normal image I43 and the ultrasound images of the second to nth imaging signals (not shown).

Then, as shown in FIG. 10(e), the ultrasound image corresponding to the first differential imaging signal generated in step S24 becomes the first differential image I45. The first differential image I45 is an ultrasound image obtained by subtracting the mutual operation image I44 from the normal image I43. Note that the first differential image I45 in FIG. 10(e) is assumed to have been subjected to contrast enhancement and binarization. Similarly, in step S24, the first differential imaging signal may be configured to be subjected to contrast enhancement and binarization.

Then, as shown in FIG. 10(f), the ultrasound image corresponding to the first difference imaging signal from which the low correlation parts have been removed, generated in step S25, becomes the first difference image I46 after the low correlation parts have been removed. The first difference image I46 after the low correlation parts have been removed is an ultrasound image from which the low correlation parts have been calculated and removed from a plurality of first difference images I45 of a predetermined number of frames.

Then, as shown in FIG. 11(a), the ultrasound image corresponding to the second difference imaging signal generated in step S26 becomes the second difference image I47. The second difference image I47 is an ultrasound image obtained by subtracting the first difference image I46 after removing the low correlation portion from the first difference image I45. In the first difference image I46, only the blood flow portion including blood cells as variable scatterers is depicted.

As shown in FIG. 11(b), the ultrasound image corresponding to the second difference image data after coloring generated in step S28 becomes the second difference image after coloring I48. In the second difference image after coloring I48, the second difference image I47 is colored in light pink. In FIG. 11(c), the light pink colored portion of the second difference image after coloring I48 is shown by hatching.

The ultrasound image corresponding to the superimposed image data generated in step S29 becomes superimposed image I49. Superimposed image I49 is an ultrasound image in which the colored second difference image I48 is superimposed on the mutual operation image I44. For example, the user performs puncture on the subject using the puncture needle 3 while observing superimposed image I49.

Next, with reference to the following Table I, a comparison of display performance between the example of this embodiment and a comparative example will be described.

Comparative example 1 is an example of normal B-mode ultrasound image data generation and display. In other words, it is a comparative example that displays a normal image (full-band B-mode image) of this embodiment. Comparative example 2 is a comparative example of normal B-mode and color Doppler mode ultrasound image data generation and display. In other words, it is a method of superimposing and displaying an image in which a color Doppler image in color Doppler mode is superimposed on the ROI portion on the B-mode image of the B-mode image data. Comparative example 3 is a comparative example that displays a mutual calculation image of mutual calculation image data.

Example 1 is an example in which superimposed image data is generated and displayed by a first ultrasound image display process including electrical noise removal. Example 2 is an example in which superimposed image data is generated and displayed by a first ultrasound image display process excluding steps S11 to S13 and S17 (steps related to electrical noise removal). Note that the subject is the patient's blood vessels and the surrounding area, which are common to each comparative example and example.

In Table I, "B-mode transmission" in "Transmission signal" of "(ultrasound) transmission and reception conditions" indicates whether or not ultrasound transmission for B mode is performed. Note that the presence of "B-mode transmission" includes the harmonic component extraction process by the harmonic component extraction unit 14c. Similarly, "Flow imaging transmission" in "Transmission signal" indicates whether or not ultrasound transmission for color Doppler mode is performed.

In addition, "non-transmitted sound ray signals and cancellation" in "transmission and reception conditions" is an item that indicates whether or not pre-processing for removing (cancelling) electrical noise is performed. In other words, "non-transmitted sound ray signals and cancellation" refers to whether or not electrical noise sound ray signals without ultrasonic transmission are generated and removed in steps S11 to S13 and S17 of the first ultrasound image display processing.

The "scatter suppression image calculation" in the "transmission and reception conditions" is an item that indicates whether or not the process of suppressing the scattered components is performed. In other words, the "scatter suppression image calculation" indicates whether or not the mutual calculation imaging signal is generated in steps S19 to S22 of the first ultrasound image display process.

The "scattered component frame correlation calculation" in the "transmission/reception conditions" is an item that indicates whether or not to perform frame correlation calculation of the B-mode image. In other words, the "scattered component frame correlation calculation" is whether or not to remove low correlation parts of the frame correlation and generate a second differential imaging signal in steps S25 and S26 of the first ultrasound image display processing.

In Table I, "Frame rate" under "Display performance (of ultrasound image)" is an item indicating the frame rate [fps] of the ultrasound image generated under the "Transmission and reception conditions". In addition, "Image resolution" under "B mode" in "Display performance" is an item indicating the distance resolution [μm]/lateral resolution [μm] of the ultrasound image generated under the "Transmission and reception conditions". Similarly, "Scattered component suppression" in "B mode" is an item indicating "A" indicating that there is an effect of suppressing scattered components on the ultrasound image generated under the "Transmission and reception conditions" or "B" indicating that there is no effect.

Similarly, "Blood flow detection" under "Display performance" is an item that indicates whether "A" indicates that blood flow (blood cells) detection is effective on the ultrasound image generated under the "Transmission and reception conditions" or "B" indicates that it is not effective. Similarly, "Electrical noise suppression" under "Display performance" is an item that indicates whether "A" indicates that electrical noise suppression is effective on the ultrasound image generated under the "Transmission and reception conditions" or "B" indicates that it is not effective.

Comparative Example 1 only generates B-mode image data, so the "frame rate" and "image resolution" of the "display performance" are also high. However, Comparative Example 1 is not effective for detecting blood flow in normal B-mode images, and is not suitable for observing blood flow.

Comparative Example 2 is effective for "blood flow detection" because it generates B-mode image data and color Doppler image data. However, Comparative Example 2 has low lateral resolution values for "frame rate" and "image resolution," and further has no "scattered component suppression" effect. For this reason, Comparative Example 2 is not suitable for observing blood flow when the frame rate is increased or when the resolution is increased.

Comparative Example 3 generates B-mode image data with the scattered components suppressed, so the same "frame rate" and "image resolution" values as Comparative Example 1 are obtained, and the "scattered component suppression" is also effective. Therefore, Comparative Example 3 is appropriate for observing B-mode images that suppress scattered components, but is not appropriate for observing blood flow, because the scattered components of variable scatterers (blood cells) are also suppressed. Note that Comparative Examples 1 to 3 do not have the effect of suppressing electrical noise.

Example 1 generates superimposed image data as B-mode image data of a correlation calculation image in which the scattered components are suppressed and the scattered components of fixed scatterers (blood cells). Therefore, Example 1 obtains the same "frame rate" and "image resolution" values as Comparative Example 1, is effective in "scattered component suppression" and "blood flow detection," and is suitable for observing blood flow in B-mode images when the scattered components are suppressed. However, it is not effective in "electrical noise suppression."

The second embodiment provides the same "display performance" effect as the first embodiment, and is also effective in "electrical noise suppression."

As described above, according to this embodiment, the ultrasound diagnostic device 100A includes a sound ray signal generating unit 14A that generates a sound ray signal based on a received signal obtained from the ultrasound probe 2 that transmits and receives ultrasound to the subject, imaging signal extracting units 15a1-15an that perform filtering through a plurality of different bands from the sound ray signal to generate first to nth imaging signals, an imaging signal calculating unit 15b that performs mutual calculation on the first to nth imaging signals to generate mutual calculation imaging signals, and an image signal analyzing unit 15c that subtracts the mutual calculation imaging signal from the normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates the frame correlation in the time direction of the first differential imaging signal, and determines low correlation parts where the frame correlation is low.

Therefore, a first differential imaging signal in which the scattering components of the scatterers are extracted can be generated, and a low correlation portion of the first differential imaging signal corresponding to a variable scatterer such as blood cells (blood flow) can be determined. In addition, by generating an ultrasound image (second differential imaging signal) that depicts the determined low correlation portion, variable scatterers such as blood cells can be depicted. In addition, ultrasonic transmission and reception in color Doppler mode and multiple ultrasonic transmission and reception for B-flow images are not performed. This makes it possible to prevent a decrease in the frame rate of the display of an ultrasound image (superimposed image data) depicting a low correlation portion. In addition, by subtracting the first differential imaging signal from which the low correlation portion has been removed from the first differential imaging signal, the scattering components of fixed scatterers such as fixed tissue can be suppressed from the first differential imaging signal. In particular, in the case of a puncture procedure using a puncture needle 3 under ultrasound guidance, flow velocity information of blood flow is not necessary. In this case, by displaying a superimposed image without displaying flow velocity information, there is no decrease in the frame rate in color Doppler mode, and it is clinically useful that the user can recognize blood vessels (blood cells).

The image signal analysis unit 15c also calculates frame correlation from the first differential imaging signals of multiple frames. This makes it possible to easily calculate frame correlation without determining a threshold value in advance.

The image signal analysis unit 15c can also be configured to calculate frame correlation from the first differential imaging signal using a threshold determined by machine learning. This makes it easy to calculate frame correlation.

The sound ray signal generating unit 14A also generates an electrical noise sound ray signal when no ultrasound is being transmitted, and subtracts the electrical noise sound ray signal from the first sound ray signal. This makes it possible to remove electrical noise components from the low correlation parts of the frame correlation, and to accurately determine the low correlation parts that correspond only to the variable scatterers.

The image signal analysis unit 15c also subtracts the first differential imaging signal from which the low correlation portion has been removed from the first differential imaging signal to generate a second differential imaging signal. Therefore, the second differential imaging signal can depict the scattering components of the variable scatterers while suppressing the scattering components of the fixed scatterers.

The ultrasound diagnostic device 100A also colors the second difference image data with a predetermined color as an addition of identification information, and generates superimposed image data by superimposing the colored second difference image data on the mutual operation image data. Therefore, the colored second difference image portion of the superimposed image data makes it possible to clearly identify the scattered components of the variable scatterers and increase their visibility. At the same time, the mutual operation image makes it possible to suppress the scattered components of parts other than the scattered components of the variable scatterers. Therefore, even in a subject with many scatterers in the tissue, the tissue (reflectors) can be depicted with high resolution, and acoustic scattering noise can be suppressed.

The ultrasound diagnostic device 100A also includes a display image processing unit 17a that simultaneously and in parallel displays on the display unit 18 a normal image based on normal image data that has not undergone mutual calculation, and a superimposed image based on superimposed image data. This allows the user to easily compare and visually recognize the normal image and the superimposed image, and can be used for diagnosis.

The imaging signal calculation unit 15b also multiplies the first to nth imaging signals as a mutual calculation. This allows the tissue (reflector) to be visualized with high resolution while reducing the processing load without using complex image processing through multiplication, and suppresses scattered acoustic noise.

The imaging signal calculation unit 15b also performs a power root calculation process of n on the first to nth imaging signals that have been mutually calculated, where n corresponds to the first to nth imaging signals. Therefore, the power root calculation process of n allows for relatively simple and appropriate level adjustment and restoration, and prevents an ultrasound image in which only high luminance areas are emphasized by multiplication alone, resulting in poor tissue visibility.

The imaging signal calculation unit 15b also performs LUT conversion processing on the first to nth imaging signals that have been mutually calculated. Therefore, the gradation adjustment restoration processing using the LUT conversion processing can prevent sequential calculations and perform appropriate gradation adjustment restoration processing, and can prevent an ultrasound image in which only high-brightness areas are emphasized by multiplication alone and tissue visibility is deteriorated.

In addition, the ultrasonic probe 2 has a -20 dB frequency band ratio of 100% or more. If the -20 dB frequency band ratio of the ultrasonic probe 2 is reduced, it becomes difficult to obtain the difference between high brightness areas and low brightness areas in multiple ultrasonic images with different imaging conditions (frequency bands). This makes it possible to improve the effect of high resolution of the mutual calculation image and tissue recognition due to the suppression of scattered acoustic noise.

The ultrasound diagnostic device 100A also includes a transmission unit 12 that generates a drive signal including multiple fundamental waves with different frequencies and outputs the drive signal to the ultrasound probe 2. The sound ray signal generation unit 14A generates a sound ray signal that includes harmonic components of multiple fundamental waves. This allows the resolution of the mutual calculation image to be further improved.

The imaging signal calculation unit 15b also sets the luminance value of the imaging signal before the mutual calculation to 0 if it is below a certain value, for example using an LUT. This makes it possible to enhance the suppression of low-correlation signal parts (scattering components) in the mutual calculation image, and makes it easier to visually recognize high-correlation signal parts (reflection components).

Second Embodiment
A second embodiment of the present invention will be described with reference to Fig. 12 and Fig. 13. Fig. 12 is a block diagram showing the functional configuration of an ultrasound diagnostic device 100B according to the present embodiment. Fig. 13 is a flowchart showing a second ultrasound image display process.

First, the device configuration of this embodiment will be described with reference to FIG. 12. As shown in FIG. 12, an ultrasound diagnostic device 100B is used as the device configuration of this embodiment. Here, the same reference numerals are used to designate parts of ultrasound diagnostic device 100B that are similar to those of ultrasound diagnostic device 100A of the first embodiment, and their description will be omitted, with the differences being mainly described.

The ultrasound diagnostic device 100B includes an ultrasound diagnostic device main body 1B and an ultrasound probe 2. The ultrasound diagnostic device main body 1B includes an operation input unit 11, a transmission unit 12, a reception unit 13, a sound ray signal generation unit 14A, a signal processing unit 15B, a DSC 16, an image processing unit 17B, a display unit 18, and a control unit 19B.

The signal processing unit 15B has imaging signal extraction units 15a1, 15a2 to 15an. The DSC 16 generates the first to nth image data from the first to nth imaging signals input from the imaging signal extraction units 15a1 to 15an in accordance with the control of the control unit 19B. In particular, the first image data (normal image data) is generated from the first imaging signal (normal imaging signal).

The image processing unit 17B is a circuit that processes image data input from the DSC 16. The image processing unit 17B has an image calculation unit 17b as a calculation unit, an image analysis unit 17c as an analysis unit, a display image processing unit 17d as a processing unit and display control unit, and a memory 17e.

The image calculation unit 17b performs a multiplication as a mutual calculation on the first to nth image data input from the DSC 16 in accordance with the control of the control unit 19B to generate mutual calculation image data. In addition, the image calculation unit 17b performs a gradation adjustment recovery process on the generated mutual calculation image data in accordance with the control of the control unit 19B.

The image analysis unit 17c analyzes the mutual calculation image data calculated by the image calculation unit 17b according to the control of the control unit 19B. This analysis includes a process of generating first differential image data, a process of determining and removing low correlation parts of the frame correlation, and a process of generating second differential image data. The process of generating first differential image data is a process of subtracting the mutual calculation image data from the first image data to generate the first differential image data. The process of determining and removing low correlation parts of the frame correlation is a process of calculating the frame correlation of the first differential image data for a predetermined number of frames, and determining and removing low correlation parts from the first differential image data. The process of generating second differential image data is a process of subtracting the first differential image data from which the low correlation parts have been removed, from the first differential image data to generate the second differential image data.

The display image processing unit 17d performs a process of coloring the second differential image data, a process of generating superimposed image data, and a process of displaying image data, under the control of the control unit 19B. The process of coloring the second differential image data is a process of coloring the image of the two differential image data generated by the image analysis unit 17c with a predetermined color. The process of generating superimposed image data is a process of generating superimposed image data by superimposing the colored second differential image data on the mutual calculation image data. The process of displaying image data is a process of displaying a normal image of the first image data (normal image data) and a superimposed image of the superimposed image data side by side on the display unit 18, or displaying the superimposed image.

Memory 17e is a volatile memory that stores at least a predetermined number of frames of the first differential image data generated by image analysis unit 17c.

The control unit 19B has a configuration similar to that of the control unit 19A in the first embodiment, and centrally controls the operation of each unit of the ultrasound diagnostic device 100B. The ROM of the control unit 19B stores a second ultrasound image display program for executing a second ultrasound image display process described below, instead of the first ultrasound image display program.

Next, the operation of ultrasound diagnostic device 100B will be described with reference to FIG. 13. Specifically, the second ultrasound image display process executed by ultrasound diagnostic device 100B will be described with reference to FIG. 13. The second ultrasound image display process is a process of generating mutual calculation image data, etc. from image data of multiple ultrasound images with different imaging conditions, and displaying a mutual calculation image depicting blood flow.

In the ultrasound diagnostic device 100B, the control unit 19B accepts in advance various setting information for ultrasound image display from the user via the operation input unit 11. The control unit 19B stores the input setting information in the RAM or memory unit (not shown) of the control unit 19B. The input setting information includes content information of the gradation adjustment restoration process to be performed on the mutual calculation image (mutual calculation image data), setting information on whether or not to remove electrical noise from the ultrasound image, and setting information on whether or not to display the normal image and the superimposed image in parallel. Note that here, the setting information for removing electrical noise is stored in the RAM or memory unit, and a second ultrasound image display process for removing electrical noise is described. However, in the second ultrasound image display process, if electrical noise removal is not necessary, the step related to electrical noise removal may not be executed.

In the ultrasound diagnostic device 100B, the control unit 19B executes the second ultrasound image display process according to the second ultrasound image display program stored in the ROM. Execution of the second ultrasound image display process is triggered, for example, by a user inputting an instruction to execute the second ultrasound image display process via the operation input unit 11.

As shown in FIG. 13, steps S41 to S51 are similar to steps S11 to S21 of the first ultrasound image display process in FIG. 9. Then, the control unit 19B causes the DSC 16 to generate the first to nth image data from the first to nth imaging signals generated in steps S49 to S51 (step S52). In step S52, the control unit 19B further causes the image calculation unit 17b to perform a mutual calculation on the generated first to nth image data to generate mutual calculation image data. The mutual calculation here is assumed to be a multiplication of the first to nth image data (multiplication of the brightness values of each pixel at the same position in the image data image).

Then, the control unit 19B refers to the setting information stored in the RAM or memory unit (not shown) and causes the image calculation unit 17b to perform a gradation adjustment recovery process corresponding to the setting information on the mutual calculation image data generated in step S52 (step S53).

Then, the control unit 19B causes the image analysis unit 17c to subtract the mutual calculation image data generated in step S53 from the first image data generated in step S49 (step S54). This subtraction generates first difference image data in which the scattered components are extracted. In step S54, the control unit 19B further causes the image signal analysis unit 15c to store the generated first difference image data in the memory 17e. The first difference image data for at least the immediately preceding predetermined number of frames is stored in the memory 17e in FIFO.

Then, the control unit 19B causes the image analysis unit 17c to calculate the frame correlation of the first differential image data of the predetermined number of frames read out from the memory 17e (step S55). The first differential image data of the predetermined number of frames includes the new first differential image data generated in the immediately preceding step S54. In step S55, the control unit 19A further causes the image analysis unit 17c to determine and remove low correlation parts of the frame correlation from the first differential image data.

Then, the control unit 19B causes the image analysis unit 17c to subtract the first differential image data after removing the low correlation parts generated in step S55 from the first differential image data (step S56). This subtraction generates second differential image data in which the scattering components of fixed scatterers are suppressed and the scattering components of variable scatterers are extracted.

Steps S57 to S61 are similar to steps S28 to S32 in Figure 9.

As described above, according to this embodiment, the imaging signal in the first embodiment is image data. In other words, the ultrasound diagnostic device 100B includes a sound ray signal generating unit 14A that generates a sound ray signal based on a received signal obtained from the ultrasound probe 2 that transmits and receives ultrasound to the subject, imaging signal extracting units 15a1 to 15an and a DSC 16 that perform filtering through a plurality of different bands from the sound ray signal to generate first to nth image data, an image calculation unit 17b that performs mutual calculation on the first to nth image data to generate mutual calculation image data, and an image analysis unit 17c that subtracts the mutual calculation image data from normal image data generated from the sound ray signal to generate first difference image data, calculates the frame correlation in the time direction of the first difference image data, and determines low correlation parts with low frame correlation.

Therefore, as in the first embodiment, it is possible to determine low correlation parts of the first difference image data that correspond to variable scatterers such as blood cells (blood flow). In addition, by generating an ultrasound image (second image data) that depicts the determined low correlation parts, variable scatterers such as blood cells can be depicted. In addition, it is possible to prevent a decrease in the frame rate of the display of the ultrasound image (superimposed image data) depicting the low correlation parts. In addition, by subtracting the first difference image data from which the low correlation parts have been removed from the first difference image data, it is possible to suppress the scattering components of fixed scatterers such as fixed tissue from the first difference image data.

Third Embodiment
A third embodiment of the present invention will be described with reference to Fig. 14 to Fig. 16. Fig. 14 is a block diagram showing the functional configuration of an ultrasound diagnostic device 100C according to this embodiment. Fig. 15 is a flowchart showing a third ultrasound image display process. Fig. 16 is a flowchart showing a fourth ultrasound image display process.

First, the device configuration of this embodiment will be described with reference to FIG. 14. As shown in FIG. 14, an ultrasound diagnostic device 100C is used as the device configuration of this embodiment. Here, the same reference numerals are used to designate parts of the ultrasound diagnostic device 100C that are similar to those of the ultrasound diagnostic device 100A of the first embodiment, and descriptions thereof will be omitted, with differences being mainly described.

The ultrasound diagnostic device 100C includes an ultrasound diagnostic device main body 1C and an ultrasound probe 2. The ultrasound diagnostic device main body 1C includes an operation input unit 11, a transmission unit 12, a reception unit 13, a sound ray signal generation unit 14C, a signal processing unit 15C, a DSC 16, an image processing unit 17A, a display unit 18, and a control unit 19C.

The receiver 13 receives electrical reception signals corresponding to the first to Nth (N: a natural number equal to or greater than 2) phasing and summing conditions from the ultrasonic probe 2 in accordance with the control of the controller 19C. The first to Nth phasing and summing conditions are conditions related to the phasing and summing of the reception signals, and include the reception aperture (reception aperture width), set sound speed, apodization, etc., corresponding to the number of reception channels of the transducer 2a of the ultrasonic probe 2. The drive signals generated by the transmitter 12 correspond to the first to Nth phasing and summing conditions.

The sound ray signal generating unit 14C has sound ray signal generating units 14d1 to 14dN, a noise removing unit 14a, a memory 14b, and a harmonic component extracting unit 14c. The sound ray signal generating units 14d1 to 14dN each have an amplifier, an A/D conversion circuit, and a phasing and summing circuit. The sound ray signal generating units 14d1 to 14dN each perform amplification, A/D conversion, and phasing and summing of the received signal received by the receiving unit 13 under the control of the control unit 19C. The first to Nth sound ray signals (first to Nth sound ray data) are generated by the phasing and summing. The first to Nth sound ray signals are generated according to the first to Nth phasing and summing conditions, respectively. For example, when the first delay-and-sum condition is a full-aperture receiving numerical aperture, the sound ray signal generator 14d1 generates a first sound ray signal (a normal image sound ray signal for a normal image corresponding to the full-aperture receiving numerical aperture) from the receiving signal in accordance with the first delay-and-sum condition. Note that the sound ray signal generator 14d1 may be configured to generate a normal image sound ray signal in accordance with the normal delay-and-sum condition.

In addition, when no ultrasonic waves are transmitted, the sound ray signal generating units 14d1 to 14dN each perform phasing addition and the like on the received signal input from the receiving unit 13 in accordance with the first to Nth phasing addition conditions. Through this phasing addition and the like, first to Nth electrical noise sound ray signals indicating electrical noise under the first to Nth phasing addition conditions are generated for each predetermined frame period. In addition, the sound ray signal generating units 14d1 to 14dN each store the generated first to Nth electrical noise sound ray signals in the memory 14b and update them.

The noise removal unit 14a removes the first to Nth electrical noise sound ray signals when ultrasonic waves are not being transmitted from the first to Nth sound ray signals when ultrasonic waves are transmitted, respectively, in accordance with the control of the control unit 19B. The first to Nth electrical noise sound ray signals are read from the memory 14b. For example, the noise removal unit 14a removes the first electrical noise sound ray signal from the first sound ray signal. The memory 14b stores the first to Nth electrical noise sound ray signals.

The harmonic component extraction unit 14c extracts harmonic components from the first to Nth sound ray signals from which the first to Nth electrical noise sound ray signals have been removed, in accordance with the control of the control unit 19B. In other words, the noise removal unit 14a applies the pulse inversion method to the first to Nth sound ray signals from which the first to Nth electrical noise sound ray signals have been removed, in order to extract harmonic components.

The signal processing unit 15C has imaging signal extraction units 15a1 to 15an, imaging signal calculation unit 15b, image signal analysis unit 15c, and memory 15d. In the fourth ultrasound image display process described later, the imaging signal extraction unit 15a1 passes the first to Nth sound ray signals after the harmonic component extraction through a first band pass filter. By passing through, the 1-1 to N-1th imaging signals are extracted from the first to Nth sound ray signals after the harmonic component extraction input from the harmonic component extraction unit 14c. The 1-1 imaging signal becomes a normal imaging signal. Similarly, the imaging signal extraction units 15a2 to 15an extract the 1-2 to N-2th imaging signals, ..., the 1-n to N-nth imaging signals, respectively, from the first to Nth sound ray signals after the harmonic component extraction in the fourth ultrasound image display process described later.

The imaging signal calculation unit 15b performs a mutual calculation on the 1-1th to N-nth imaging signals in accordance with the control of the control unit 19C in the fourth ultrasound image display process described later. Through this mutual calculation, a mutual calculation imaging signal is generated from the 1-1th to N-nth imaging signals generated by the imaging signal extraction units 15a1 to 15an. Note that, in the third ultrasound image display process described later, the imaging signal calculation unit 15b performs a mutual calculation on the 1st to Nth sound ray signals after harmonic component extraction input from the harmonic component extraction unit 14c. Through this mutual calculation, a mutual calculation imaging signal is generated from the 1st to Nth imaging signals after harmonic component extraction. Also, the imaging signal calculation unit 15b performs a step adjustment recovery process on the generated mutual calculation imaging signal in accordance with the control of the control unit 19C.

The image signal analysis unit 15c analyzes the mutually calculated imaging signal calculated by the imaging signal calculation unit 15b according to the control of the control unit 19C. Through this analysis, a first differential imaging signal and a second differential image signal are generated.

The control unit 19C has a configuration similar to that of the control unit 19A of the first embodiment, and controls each unit of the ultrasound diagnostic device 100C. Instead of the first ultrasound image display program, the ROM of the control unit 19C stores a third ultrasound image display program for executing a third ultrasound image display process described below, and a fourth ultrasound image display program for executing a fourth ultrasound image display process described below.

Next, the operation of the ultrasound diagnostic device 100C will be described with reference to Figures 15 and 16. First, the third ultrasound image display process executed by the ultrasound diagnostic device 100C will be described with reference to Figure 15. The third ultrasound image display process is a process that generates a mutual operation imaging signal from the imaging signals of multiple ultrasound images with different matching addition conditions, and displays a mutual operation image that depicts blood flow.

In the ultrasound diagnostic device 100C, the control unit 19C accepts in advance various setting information for ultrasound image display from the user via the operation input unit 11. The control unit 19C stores the input setting information in the RAM or memory unit (not shown) of the control unit 19C. The input setting information includes content information of the gradation adjustment restoration process to be performed on the mutual operation image (mutual operation imaging signal), setting information on whether or not to remove electrical noise from the ultrasound image, and setting information on whether or not to display the normal image and the superimposed image in parallel. Note that here, the setting information for removing electrical noise is stored in the RAM or memory unit, and a third ultrasound image display process for removing electrical noise is described. However, in the third ultrasound image display process, if electrical noise removal is not necessary, the step related to electrical noise removal may not be executed.

In the ultrasound diagnostic device 100C, the control unit 19C executes a third ultrasound image display process according to a third ultrasound image display program stored in the ROM. Execution of the third ultrasound image display process is triggered, for example, by a user inputting an instruction to execute the third ultrasound image display process via the operation input unit 11.

As shown in FIG. 15, step S71 is the same as step S11 of the first ultrasound image display process in FIG. 9. If it is a predetermined frame period (step S71; YES), the control unit 19C causes the receiving unit 13 to generate a received signal (step S72). In step S72, the control unit 19C further causes the sound ray signal generating units 14d1 to 14dN to perform amplification, A/D conversion, and phasing addition on the generated received signal under the first to Nth phasing addition conditions. The first to Nth electrical noise sound ray signals are generated by the phasing addition and the like. In step S72, ultrasonic transmission is not performed.

Then, the control unit 19C stores (updates) the first to Nth electrical noise sound ray signals generated in step S72 in the memory 14b (step S73). Steps S74 and S75 are the same as steps S14 and S15 in FIG. 9.

Then, the control unit 19C causes the receiving unit 13 to receive the reflected ultrasound that is the ultrasound transmitted in step S75 and reflected and scattered by the subject, and generate a received signal (step S76).

Then, the control unit 19C causes the sound ray signal generating unit 14d1 to generate a first sound ray signal from the reception signal generated in step S76 under the first phasing and summation condition (step S77). The first sound ray signal includes three fundamental wave components and a harmonic component. The control unit 19C then causes the noise removing unit 14a to remove the first electrical noise sound ray signal stored in the memory 14b from the first sound ray signal generated in step S77 (step S78).

Then, the control unit 19C causes the harmonic component extraction unit 14c to extract harmonic components from the first sound ray signal generated in step S78 using the pulse inversion method (step S79).Then, the control unit 19C causes the signal processing unit 15C to generate the first sound ray signal from which the harmonic components generated in step S79 have been extracted as a first imaging signal (step S80).

In parallel with steps S77 to S80, the control unit 19C causes the sound ray signal generating unit 14d2 to generate a second sound ray signal from the reception signal generated in step S76 (step S81). The second sound ray signal is generated based on the second delay-and-sum condition. Then, the control unit 19C causes the noise removing unit 14a to remove the second electrical noise sound ray signal stored in the memory 14b from the second sound ray signal generated in step S71 (step S82).

Then, the control unit 19C causes the harmonic component extraction unit 14c to extract harmonic components from the second sound ray signal generated in step S81 using the pulse inversion method (step S83).Then, the control unit 19C causes the signal processing unit 15C to generate the second sound ray signal generated in step S83 as a second imaging signal (step S84).

Similarly, the control unit 19C causes the sound ray signal generating units 14d3 to 14d(N-1), the noise removing unit 14a, the harmonic component extracting unit 14c, and the signal processing unit 15C to generate the third to (N-1)th imaging signals. In parallel with steps S77 to S80, the control unit 19C causes the sound ray signal generating unit 14dN to generate the Nth sound ray signal from the reception signal generated in step S76 (step S85). The Nth sound ray signal is generated based on the Nth phase adjustment and addition condition. Then, the control unit 19C causes the noise removing unit 14a to remove the Nth electrical noise sound ray signal stored in the memory 14b from the Nth sound ray signal generated in step S75 (step S86).

Then, the control unit 19C causes the harmonic component extraction unit 14c to extract harmonic components from the Nth sound ray signal generated in step S86 using the pulse inversion method (step S87).Then, the control unit 19C causes the signal processing unit 15C to generate the Nth sound ray signal generated in step S87 as the Nth imaging signal (step S88).

Then, the control unit 19C causes the imaging signal calculation unit 15b to perform mutual calculation on the first to Nth imaging signals generated in steps S80, S84, S88, etc. (step S89). A mutually calculated imaging signal is generated in step S89. The mutual calculation here is assumed to be a multiplication of the first to Nth imaging signals. Steps S90 to S99 are similar to steps S23 to S32 in FIG. 9.

Next, the fourth ultrasound image display process executed by the ultrasound diagnostic device 100C will be described with reference to FIG. 16. The fourth ultrasound image display process is a process in which a mutual operation imaging signal is generated from the imaging signals of multiple ultrasound images having different imaging conditions and delay-and-sum conditions, and a mutual operation image depicting blood flow is displayed.

In the ultrasound diagnostic device 100C, the control unit 19C accepts in advance, via the operation input unit 11, various setting information for ultrasound image display from users such as doctors and engineers. The input setting information is stored in the RAM or memory unit (not shown) of the control unit 19C. The input setting information includes content information of the gradation adjustment restoration process to be performed on the mutual operation image (mutual operation imaging signal), setting information on whether or not to remove electrical noise from the ultrasound image, and setting information on whether or not to display the normal image and the superimposed image in parallel. Note that, here, the setting information for removing electrical noise is stored in the RAM or memory unit, and a fourth ultrasound image display process for removing electrical noise is described. However, in the fourth ultrasound image display process, if electrical noise removal is not necessary, the step related to electrical noise removal may not be executed.

In the ultrasound diagnostic device 100C, the control unit 19C executes a fourth ultrasound image display process according to a fourth ultrasound image display program stored in the ROM. Execution of the fourth ultrasound image display process is triggered, for example, by a user inputting an instruction to execute the fourth ultrasound image display process via the operation input unit 11.

As shown in FIG. 16, steps S101 to S109 are similar to steps S71 to S79 of the third ultrasound image display process in FIG. 15. The control unit 19C then causes the imaging signal extraction unit 15a1 to generate a 1-1 imaging signal (normal imaging signal) from the first sound ray signal generated in step S109 (step S110). In step S110, the imaging signal extraction unit 15a1 passes the first sound ray signal through a first band pass filter that passes a predetermined frequency band (full band) as the first imaging condition.

Similarly, in parallel with step S110, the control unit 19C causes the imaging signal extraction units 15a2 to 15a(n-1) to generate 1-2-th to 1-(n-1)-th imaging signals. Also, in parallel with step S110, the control unit 19C causes the imaging signal extraction unit 15an to generate 1-n imaging signals from the first sound ray signal generated in step S109 (step S111). In step S111, the imaging signal extraction unit 15an passes the first sound ray signal through an n-th band pass filter that passes a predetermined frequency band as the n-th imaging condition.

Similarly, in parallel with steps S107 to S111, the control unit 19C causes the sound ray signal generating units 14d2 to 14d(N-1), the noise removing unit 14a, the harmonic component extracting unit 14c, and the imaging signal extracting units 15a1 to 15an to generate the 2-1st to 2-nth imaging signals to the (N-1)-1st to (N-1)-nth imaging signals.

Steps S112 to S114 are the same as steps S85 to S87 in FIG. 15. Then, the control unit 19C causes the imaging signal extraction unit 15a1 to generate the N-1 imaging signal from the N sound ray signal generated in step S114 (step S115). In step S115, the imaging signal extraction unit 15a1 passes the sound ray signal through a first band pass filter that passes a predetermined frequency band (full band) as the first imaging condition. Similarly, in parallel with step S115, the control unit 19C causes the imaging signal extraction units 15a2 to 15a(n-1) to generate the N-2 to N-(n-1) imaging signals. Also, in parallel with step S115, the control unit 19C causes the imaging signal extraction unit 15an to generate the N-n imaging signal from the N sound ray signal generated in step S114 (step S116). In step S116, the imaging signal extraction unit 15an passes the Nth sound ray signal through an nth band-pass filter that passes a predetermined frequency band as the nth imaging condition.

Then, the control unit 19C causes the imaging signal calculation unit 15b to perform mutual calculation on the 1-1th to N-nth imaging signals generated in steps S110 to S111 to S115 to S116 (step S117). A mutually calculated imaging signal is generated in step S117. The mutual calculation here is assumed to be the multiplication of the 1-1th to N-nth imaging signals. Steps S118 to S127 are similar to steps S90 to S99 in FIG. 15.

As described above, according to this embodiment, the ultrasound diagnostic device 100C includes a sound ray signal generating unit 14C that performs phasing addition under a plurality of different phasing addition conditions on the received signal obtained from the ultrasound probe 2 that transmits and receives ultrasound to the subject to generate first to Nth sound ray signals, an imaging signal calculating unit 15b that performs mutual calculation on the first to Nth imaging signals based on the first to Nth sound ray signals to generate mutual calculation imaging signals, and an image signal analyzing unit 15c that subtracts the mutual calculation imaging signal from the normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates the frame correlation in the time direction of the first differential imaging signal, and determines low correlation parts where the frame correlation is low.

The ultrasound diagnostic device 100C also includes imaging signal extraction units 15a1 to 15an that perform filtering on the 1st to Nth sound ray signals to pass through a plurality of different bands, thereby generating 1-1th to N-nth imaging signals. The imaging signal calculation unit 15b performs mutual calculation on the 1-1th to N-nth imaging signals based on the 1st to Nth sound ray signals, thereby generating mutual calculation imaging signals.

Therefore, as in the first embodiment, it is possible to determine low correlation parts of the first differential imaging signal that correspond to variable scatterers such as blood cells (blood flow). Furthermore, by generating an ultrasound image (second differential imaging signal) that depicts the determined low correlation parts, variable scatterers such as blood cells can be depicted. Furthermore, it is possible to prevent a decrease in the frame rate of the display of the ultrasound image (superimposed image data) depicting the low correlation parts. Furthermore, by subtracting the first differential imaging signal from which the low correlation parts have been removed, it is possible to suppress the scattering components of fixed scatterers such as fixed tissue from the first differential imaging signal.

In the above explanation, an example has been disclosed in which a ROM is used as a computer-readable medium for the program according to the present invention, but this is not limiting. As other computer-readable media, non-volatile memory such as a flash memory, and portable recording media such as a CD-ROM can be applied. In addition, carrier waves can also be applied to the present invention as a medium for providing data for the program according to the present invention via a communication line.

Note that the description in the above embodiment is an example of a suitable ultrasound diagnostic device, ultrasound image generating method, and program according to the present invention, and is not limited thereto. For example, at least two of the above first to third embodiments may be appropriately combined. As a specific example, the second and third embodiments are combined to configure the ultrasound diagnostic device 100C in such a manner that the image processing unit 17A has an image calculation unit 17b, an image analysis unit 17c, a display image processing unit 17d, and a memory 17e. The control unit 19C causes the sound ray signal generation unit 14C to generate the 1st to Nth imaging signals, and causes the imaging signal extraction units 15a1 to 15an to generate the 1st-1st to N-nth imaging signals. Then, the control unit 19C causes the image calculation unit 17b to perform mutual calculation on the 1st-1st to N-nth image data obtained via the DSC 16 to generate mutual calculation image data. The control unit 19C then causes the image analysis unit 17c to generate first differential image data and second differential image data, and causes the display image processing unit 17d to generate superimposed image data.

In addition, in the first to third embodiments described above, the processing in the signal processing units 15A, 15B, and 15C and the image processing units 17A and 17B may be performed on a frame-by-frame or sound ray-by-sound ray basis.

In the first to third embodiments, the mutual calculation is performed by multiplying a plurality of ultrasound images (imaging signals (sound ray signals) or image data). However, the present invention is not limited to this configuration. For example, the mutual calculation of ultrasound images may be performed by a method other than multiplication, which utilizes the correlation difference in image brightness to obtain a post-calculation brightness value. Specifically, in m (m: a natural number of 2 or more) ultrasound images with different image formation conditions and delay-and-sum conditions, the variation in the brightness values (L1, L2, ..., Lm) of each image at each pixel coordinate position (x, y) is obtained as a variance value V. Then, a mutual calculation image (imaging signal, image data) of the mutual calculation brightness values reflecting the magnitude of the variation can be obtained by a method such as multiplying the average brightness value LA by the reciprocal of this variance value V.

In the first to third embodiments, the ultrasound diagnostic device generates drive signals and sound ray signals for the pulse inversion method, and targets the harmonic imaging mode. However, this is not limited to the configuration. The ultrasound diagnostic device may target the harmonic imaging mode, which does not use the pulse inversion method, but extracts harmonics from the sound ray signal by a so-called filter method. Also, the configuration may target the fundamental imaging mode without performing harmonic extraction processing.

Furthermore, the detailed configurations and detailed operations of the components constituting the ultrasound diagnostic devices 100A, 100B, and 100C in the first to third embodiments described above may be modified as appropriate without departing from the spirit of the present invention.

100A, 100B, 100C Ultrasonic diagnostic apparatus 1A, 1B, 1C Ultrasonic diagnostic apparatus main body 11 Operation input section 12 Transmission section 121 Clock generation circuit 122 Pulse generation circuit 123 Time and voltage setting section 124 Delay circuit 13 Reception section 14A, 14C, 14d1 to 14dN Sound ray signal generation section 14a Noise removal section 14b Memory 14c Harmonic component extraction section 15A, 15B, 15C Signal processing section 15a1 to 15an Imaging signal extraction section 15b Imaging signal calculation section 15c Image signal analysis section 15d Memory 16 DSC
17A, 17B Image processing units 17a, 17d Display image processing unit 17b Image calculation unit 17c Image analysis unit 17e Memory 18 Display units 19A, 19B, 19C Control unit 2 Ultrasonic probe 21 Ultrasonic probe body 2a Transducer 22 Cable 23 Connector 3 Puncture needle

Claims (20)

a first generator that generates a sound ray signal based on a reception signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject;
a second generation unit that performs filtering to pass a plurality of different bands from the sound ray signal to generate a plurality of imaging signals;
a calculation unit that performs a mutual calculation on the plurality of imaging signals to generate a mutual calculation imaging signal;
an analysis unit that subtracts the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates a frame correlation in a time direction of the first differential imaging signal, and determines a low correlation portion where the frame correlation is low. A first generation unit that performs delay-and-sum under a plurality of different delay-and-sum conditions on a received signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to a subject to generate a plurality of sound ray signals;
a calculation unit that performs a mutual calculation on a plurality of imaging signals based on the plurality of sound ray signals to generate a mutual calculation imaging signal;
an analysis unit that subtracts the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates a frame correlation in a time direction of the first differential imaging signal, and determines a low correlation portion where the frame correlation is low. The ultrasound diagnostic device according to claim 2, further comprising a second generator that performs filtering on the sound ray signals to pass through a plurality of different bands to generate a plurality of imaging signals. The ultrasound diagnostic device according to any one of claims 1 to 3, wherein the analysis unit calculates the frame correlation from the first differential imaging signals of multiple frames. The ultrasound diagnostic device of claim 4, wherein the analysis unit calculates the frame correlation from the first differential imaging signal using a threshold determined by machine learning. The ultrasound diagnostic device according to any one of claims 1 to 3, wherein the first generator generates an electrical noise sound ray signal when no ultrasound is transmitted and subtracts the electrical noise sound ray signal from the sound ray signal. The ultrasound diagnostic device according to any one of claims 1 to 3, wherein the analysis unit subtracts the first differential imaging signal from which the low correlation portion has been removed, to generate a second differential imaging signal. The ultrasound diagnostic device according to claim 7, further comprising an image processing unit that adds identification information to the second differential imaging signal, and superimposes the second differential imaging signal to which the identification information has been added on the mutual operation imaging signal to generate a superimposed imaging signal. The ultrasound diagnostic device according to claim 8, further comprising a display control unit that simultaneously and in parallel displays a normal image based on the normal imaging signal and a superimposed image based on the superimposed imaging signal on a display unit. The ultrasound diagnostic device according to any one of claims 1 to 3, wherein the calculation unit multiplies the multiple imaging signals as the mutual calculation. The ultrasound diagnostic device according to any one of claims 1 to 3, wherein the calculation unit performs a power root calculation process on the mutual calculation imaging signal according to the plurality of imaging signals. The ultrasound diagnostic device according to any one of claims 1 to 3, wherein the calculation unit performs LUT conversion processing on the mutual calculation imaging signal. An ultrasound diagnostic device according to any one of claims 1 to 3, wherein the ultrasound probe has a -20 dB frequency band ratio of 100% or more. a transmission unit that generates a drive signal including a plurality of fundamental waves having different frequencies and outputs the drive signal to the ultrasonic probe;
The ultrasonic diagnostic apparatus according to claim 1 , wherein the first generator generates a sound ray signal having harmonic components of the plurality of fundamental waves. The ultrasound diagnostic device according to any one of claims 1 to 3, wherein the calculation unit sets luminance values of the mutual calculation imaging signal below a certain value to 0. The ultrasound diagnostic device according to any one of claims 1 to 3, wherein the imaging signal is image data. A first step of generating a sound ray signal based on a received signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject;
a second step of filtering the sound ray signals through a plurality of different bands to generate a plurality of imaging signals;
a third step of cross-operating the plurality of imaging signals to generate a cross-operated imaging signal;
and a fourth step of subtracting the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculating a frame correlation in the time direction of the first differential imaging signal, and determining a low correlation portion where the frame correlation is low. A first step of performing delay-and-sum under a plurality of different delay-and-sum conditions on a received signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to a subject to generate a plurality of sound ray signals;
a second step of performing a mutual operation on a plurality of imaging signals based on the plurality of sound ray signals to generate a mutual operation imaging signal;
and a third step of subtracting the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculating a frame correlation in the time direction of the first differential imaging signal, and determining a low correlation portion where the frame correlation is low. Computer,
a first generator that generates a sound ray signal based on a reception signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject;
a second generation unit that performs filtering to pass a plurality of different bands from the sound ray signals to generate a plurality of imaging signals;
a calculation unit that performs a mutual calculation on the plurality of imaging signals to generate a mutual calculation imaging signal;
an analysis unit that subtracts the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates a frame correlation in a time direction of the first differential imaging signal, and determines a low correlation portion where the frame correlation is low;
A program to function as a Computer,
a first generation unit that performs delay-and-sum under a plurality of different delay-and-sum conditions on a reception signal obtained from an ultrasonic probe that transmits and receives ultrasonic waves to a subject, thereby generating a plurality of sound ray signals;
a calculation unit that performs a mutual calculation on a plurality of imaging signals based on the plurality of sound ray signals to generate a mutual calculation imaging signal;
an analysis unit that subtracts the mutual operation imaging signal from a normal imaging signal generated from the sound ray signal to generate a first differential imaging signal, calculates a frame correlation in a time direction of the first differential imaging signal, and determines a low correlation portion where the frame correlation is low;
A program to function as a

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