Ultrasound Imaging Device

Abstract

To provide a noise reduction technology to acquire a hardness image of a biological tissue by a CD-SWI method even in an ultrasonic diagnostic device in which noise is large.SOLUTION: A signal processing device sequentially executes a band pass filtering step for causing only a sine wave signal of a frequency range corresponding to a specific frequency of sine wave oscillation to pass, and a flow velocity estimation step for acquiring an amplified signal obtained by amplifying a pulse repetition frequency of an ultrasonic wave on a specific signal having periodicity and symmetric property in a half period in a received original signal, and on the basis of the amplified signal, estimating a flow velocity by excitation.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an ultrasonic imaging device that uses ultrasonic waves to image the hardness of biological tissue of a living body (human or animal), and in particular to an ultrasonic imaging device having a noise reduction effect, and an ultrasonic imaging system equipped with the ultrasonic imaging device. [Background technology]

[0002] There is a demand for quantitative measurement of skeletal muscle stiffness and changes in a physical therapy room for rehabilitation, a treatment room for massage, a training room for sports medicine, etc. In other words, there is a demand for quantitative evaluation of skeletal muscle stiffness, which was difficult with conventional technology, and for the results to be linked to rehabilitation, massage, and training effectiveness evaluation, effective treatment, and the formulation of training plans. To meet such demands, it is considered that the use of CD-SWI, a biological stiffness imaging method, is an option, but in this case, it is necessary to incorporate the CD-SWI method into a small, portable echo device that can be used in the field (tablet echo: a device that performs ultrasonic diagnosis by incorporating electronic circuits and a CPU in a probe and connecting it to a tablet or PC) rather than a large ultrasonic diagnostic device. Conventionally, WO2015 / 151972 (see Patent Document 1) has been disclosed as an ultrasonic imaging method for imaging the stiffness of biological tissues of a living body (human body or animal) using ultrasonic waves. However, such tablet echo devices have higher noise levels than large ultrasound diagnostic devices, and even if the above-mentioned skeletal muscle stiffness measurement method is incorporated, the images obtained are often unclear and poorly quantitative due to the significant influence of noise.

[0003] 2. Description of the Related Art Conventionally, WO2015 / 151972 (see Patent Document 1) has disclosed an ultrasound imaging method for imaging the hardness of biological tissue of a living body (human or animal) using ultrasound. Another conventional method disclosed is to use an ultrasound contactor to scan a subject in three dimensions with ultrasound, and then insert a double-structured puncture needle into the subject and cause the inner needle to protrude from the outer needle, thereby inserting it into the subject and collecting tissue from the tissue to be collected. The method is equipped with an image generation means for generating an image of the subject based on ultrasound scan data and an image of the puncture needle being inserted into the subject, and a display means for displaying the image of the subject generated by the image generation means and the image of the puncture needle (see Patent Document 2).

[0004] In this device, an exciter that applies minute vibrations is installed in the puncture needle, and the probe receives an echo signal influenced by the Doppler effect of the puncture needle vibrated by this exciter, thereby recognizing the movement of the inner needle protruding from the outer needle of the puncture needle. Here, the image generating means displays, on the display means, an image of tissue that is expected to be collected from the sampled portion if the inner needle were to protrude from the outer needle just before the inner needle of the puncture needle is inserted into the sampled portion. According to the document, it is possible to predict which part of the sampled portion will be collected by simply looking at the display means prior to collecting tissue from the sampled portion, and it is possible to reliably collect the desired tissue.

[0005] Furthermore, a conventional ultrasonic imaging method has been disclosed that generates an image of a vibrating puncture needle based on the Doppler signal of an ultrasonic echo from the needle, and is characterized in that the Doppler signal is obtained by MTI processing of an echo signal with a packet length of 2 obtained by two ultrasonic transmissions and receptions per sound ray (see Patent Document 3).

[0006] This method finds the Doppler shift by performing MTI processing between echo signals with a packet length of 2 obtained by two ultrasound transmissions per acoustic ray. According to the document, the Doppler shift can be found with the minimum number of ultrasound transmissions per acoustic ray, which speeds up imaging and widens the imaging field of view. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2015 / 151972A1 publication [Patent Document 2] Patent No. 5274854 [Patent Document 3] Patent No. 4030644 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when the tablet echo device described in the above-mentioned document 1 is miniaturized or made into a device, it has a higher noise than a large ultrasonic diagnostic device, and even if the above-mentioned skeletal muscle stiffness measurement method is incorporated, it is often the case that only a blurred image with low quantitativeness is obtained due to the large influence of noise. In other words, when the device is miniaturized or made into an application that can be operated on a simple control program, only a noisy original signal can be received due to problems with processing accuracy, and a clear image of the stiffness of biological tissue cannot be obtained.

[0009] In particular, when noise reduction processing is performed based on the original signal generated by ultrasonic excitation, it is assumed that the excitation for exciting shear waves in biological tissue is performed with a continuous sine wave of a specific frequency, which is a characteristic of the original signal. Therefore, if the ultrasonic excitation to the biological object or the positional relationship with the receiver is not stable, the excitation wave will be disturbed, and a large amount of noise will be mixed in, or processing based on the assumption of a continuous sine wave may not be possible.

[0010] The devices described in the above documents 2 and 3 are based on the premise that a puncture needle is inserted into a living body to perform measurements, and have the problem that the captured images are limited depending on the puncture position or depth, and therefore on the technique of the person performing the puncture. The reason for this is that it is difficult to correctly place the indwelling needle in the vein.

[0011] Therefore, an object of the present invention is to develop a noise reduction technique that enables the acquisition of images of tissue stiffness using the CD-SWI method even in ultrasonic diagnostic equipment with high noise levels. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention provides the following means: However, in the following description, the numbers or letters following the names of the components are symbols added for the sake of convenience in understanding the drawings, and are not intended to limit the concept, shape, or structure of the components.

[0013] (1) (Filtering and flow velocity estimation using sinusoidal excitation) a vibrator that applies a sinusoidal vibration of a specific frequency in a specific direction within the living body while being in contact with the epidermis of the living body; A probe in which multiple ultrasonic transducers are arranged two-dimensionally with the same arrangement for both transmitters and receivers. a signal processing device that generates and outputs an ultrasonic image signal of a shear wave from the original signal received by the probe; A display device that displays an ultrasonic image signal from the signal processing device, The signal processing device includes a step of band-pass filtering for passing only a sinusoidal signal in a frequency range corresponding to a specific frequency of a sinusoidal vibration; a flow velocity estimation step of estimating a flow velocity value due to excitation based on an amplified signal obtained by amplifying an ultrasonic pulse repetition frequency for a specific signal having periodicity and symmetry in a half cycle in a received original signal, and

[0014] (2) The flow velocity estimation step derives an autocorrelation value (Is) by performing an addition process based on autocorrelation for each of a plurality of specific signals in one period obtained by orthogonal detection of the received ultrasonic wave, The flow velocity value is calculated by averaging the multiple autocorrelation values ​​(Is) obtained. A flow velocity calculation step is performed to obtain a flow velocity value based on the vibration based on the amplified signal obtained by oversampling.

[0015] (3) The vibrator excites a specific signal having multiple periods, The signal processing device derives an autocorrelation value (Is) by performing an addition process based on autocorrelation for each specific signal of each excitation period, and calculates an autocorrelation value corresponding to each of the specific multiple periods; It is preferable to compare average values ​​of the autocorrelation values ​​corresponding to each of a plurality of periods to obtain an estimated flow velocity value.

[0016] (4) (Map display of two-dimensional array) In any one of the ultrasonic imaging devices described above, It is preferable that the display device continuously detects the state of blood flow (the flow of foreign matter in the blood flow) within a predetermined detection surface range and continuously displays it as a moving image. By displaying the passing of a foreign object as a video at the corresponding position on the two-dimensional map, it is possible to easily obtain not only the presence or absence of a passing foreign object, but also information about the passing object (size, speed, position, etc.).

[0017] (5) (Connecting jig) In any one of the ultrasonic imaging devices described above, a transmitting / receiving unit of a probe and Excitation Vessel Excitation The transmitter and receiver of the probe are aligned parallel to each other and maintain a constant distance and angle within a certain range. Excitation Vessel Excitation The device further includes a connecting jig for connecting the portion.

[0018] (6) Furthermore, it is preferable that the propagation velocities detected by the detection signals of each of the two-dimensionally arranged receivers are displayed on a two-dimensional map of a two-dimensional detection image area arranged two-dimensionally on a display device, and that the values ​​of the propagation velocities detected by the detection signals of some of the two-dimensionally arranged receivers are colored and displayed at corresponding positions on the two-dimensional map. By displaying a two-dimensional array map aligned with the detection surface, an image of the stiffness of biological tissue on the map can be obtained intuitively.

[0019] (7) (Doppler focusing with time delay correction term) In any of the ultrasonic imaging devices described above, it is preferable to further store data of reflected waves from a plurality of receivers arranged two-dimensionally as a sequence of propagation velocity values ​​for each coordinate for each time base, and based on a data group of the propagation velocity value sequences, continuously create a difference image of the propagation velocity for each time base, and continuously display a moving image of the propagation velocity in the two-dimensional region together with information on the detection depth on a display device based on the initially stored two-dimensional image of the propagation velocity and the data of the difference image continuously created. In addition, the spatial time delay is geometrically analyzed and formulated, and then replaced with a simple formula that takes into account the sound field characteristics of the ultrasonic element itself and the sound field characteristics of the entire array, thereby correcting the time delay. This allows for continuous Doppler focusing, which is a simple discrimination method but also carries a lot of information.

[0020] (5) (Identification of type of foreign matter) In any of the ultrasonic imaging devices described above, it is preferable that the ultrasonic signals received by each transducer are further analyzed as information including a time axis, and the hardness of the biological tissue is classified into one of a plurality of pre-classified object models based on discrimination criteria based on the hardness, size, and flow speed of the foreign object, and the determined object model is displayed on the display screen in a color or shape that corresponds one-to-one to the determined object model at a corresponding position on the two-dimensional map over the predetermined continuous time period. (6) Ultrasonic imaging device method The ultrasonic imaging method of the present invention includes a detection step of arranging a plurality of ultrasonic transducers in two dimensions with the same arrangement of transmitters and receivers, and detecting ultrasonic waves in a detection surface range formed by this two-dimensional array; A step of correcting data of reflected waves by receivers of the plurality of ultrasonic transducers arranged two-dimensionally using a correction term that corrects a time delay from transmission to reception in either a time domain or a frequency domain; A display step is performed in which the difference in the object model of the biological tissue detected by the receivers of a plurality of ultrasonic transducers arranged in a two-dimensional array is overwritten and displayed at a corresponding position on the two-dimensional map corresponding to a specific receiver that received the detection signal of some of the receivers in a display area corresponding to the detection surface range of the detection step on the display screen of the display device, and each step is executed continuously over a continuous time. Effect of the Invention

[0021] As described above, the ultrasonic imaging device and ultrasonic imaging method provided by the present invention adopt a configuration in which ultrasonic transmitting elements and receiving elements are arranged in the same two-dimensional array, ultrasonic detection is performed over a predetermined continuous period of time over the detection surface area formed by this two-dimensional array, and the same array is also arranged in two dimensions on the display device to display a map.Therefore, it is possible to obtain information regarding the status of passing foreign objects (number, size, shape, passing position) with high accuracy without having to adopt a complex structure due to the incorporation of other ultrasonic imaging devices, etc. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is an explanatory diagram showing the device configuration of an ultrasonic imaging device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing the configuration of a detection device of the ultrasonic imaging apparatus according to the first embodiment shown in FIG. [Diagram 3] 1A and 1B are a plan view and a front view showing an ultrasonic transducer mounting jig for a detection device of an ultrasonic imaging apparatus according to a first embodiment of the present invention. [Figure 4] 5A and 5B are explanatory diagrams showing a third example of a detection surface range and a display screen of the ultrasonic imaging device of the present invention. [Diagram 5] FIG. 1 is a conceptual diagram of flow velocity measurement specialized for sinusoidal excitation in the ultrasonic image processing of the present invention (when the oversampling rate is n=4). [Figure 6]FIG. 1 is a conceptual diagram of flow velocity measurement specialized for sinusoidal excitation in the ultrasonic image processing of the present invention (when the oversampling rate is n=2). [Figure 7] 1 is a comparison of the principles and effects of noise reduction technology using ultrasonic image processing according to the present invention. [Figure 8] 1 is a diagram comparing the effect of the noise reduction method using ultrasonic image processing of the present invention (lower row) with the conventional method (upper row). [Figure 9] 4 is a graph showing an evaluation of noise resistance according to the ultrasound image processing of the present invention; [Figure 10] 1A and 1B are a plan view and a front view showing an ultrasonic transducer mounting jig for a detection device of an ultrasonic imaging apparatus according to a first embodiment of the present invention. [Figure 11] FIG. 2 is an explanatory diagram showing a first example of a detection surface range (a) and a display screen (b) of the ultrasonic imaging device of the present invention. [Figure 12] 13 is a graph showing changes in stiffness of the trapezius muscle due to exercise load, taken using the ultrasonic imaging device of the present invention. [Figure 13] 13 is a graph comparing the probing depth of the stiffness of the trapezius muscle due to exercise load, using the ultrasound imaging device of the present invention. [Figure 14] 13 is a correlation graph showing the difference in propagation velocity immediately after the first exercise load and the difference in propagation velocity between shallow and deep areas, obtained by the ultrasonic imaging device of the present invention. [Figure 15] 4 is a graph showing an example of the change in the propagation velocity of shear waves before and after injection of saline into painful fascia using the ultrasonic imaging device of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The ultrasonic imaging device of the first embodiment of the present invention shown in FIG. 1 is composed of a first detection device P1 and a second detection device P2 in which a plurality of ultrasonic transducers are arranged two-dimensionally with the same arrangement for both transmitters and receivers, a control device 2 that controls ultrasonic vibrations by each of these detection devices P1 and P2 and transmits and receives signals, a processing device 1 that corrects and amplifies data of reflected waves received by the control device 2, and a display device having a display area M1 that displays information regarding the data of reflected waves processed by the processing device 1.

[0024] The purpose of this study is to develop a noise reduction technology that can obtain images of biological tissue stiffness using the CD-SWI method even with ultrasound diagnostic equipment with high noise. In noise reduction processing, it is important to focus on the time and frequency characteristics of the original signal obtained by the ultrasound diagnostic equipment, which are specific to the CD-SWI method, and to extract and emphasize only the signals that have these characteristics. This invention actively utilizes the characteristic of the original signal in the stiffness image obtained by the CD-SWI method, that is, "the excitation to excite shear waves in biological tissue is performed with a continuous sine wave of a specific frequency." By introducing a noise reduction technology specialized for sine wave excitation, which includes two methods: 1) MTI Filter (Moving Target Indicator) specialized for sine wave excitation, and 2) flow velocity estimation specialized for sine wave excitation, stiffness images can be obtained even with ultrasound imaging equipment with high noise, such as tablet-type ultrasound imaging equipment, and quantitative measurement of stiffness can be performed.

[0025] In the first embodiment, a control device 2 connected in parallel to two detection devices P1, P2 by wire includes a memory unit R, a display device M2, and an input device I2, and signals corresponding to the channels of each receiver are connected to a processing device 1 by a cable C. The processing device 1 is provided with a switch S, an adjustment device V, a speaker, and a locking unit for the detection devices P1, P2, and is connected to the display device M1 and the input device I by wire or wirelessly.

[0026] figure 10As shown in the figure, shear waves are excited in biological tissue from the vibrator (S) vibrating with a sine wave, and these shear waves propagate through the biological tissue. At this time, if ultrasonic waves are simultaneously transmitted from the ultrasonic probe (P), the ultrasonic waves reflected from the biological tissue and received by the ultrasonic probe have a Doppler effect due to the vibration, resulting in a signal with a slightly modulated frequency. 10 (AM) (OW) is the amplifier for excitation, Excitation Equipment, and Excitation It is a control device that determines the frequency. The signal obtained by the ultrasonic probe is subjected to quadrature detection and then input as an IQ signal to a shear wave imaging system (AW) consisting of a signal processing device such as a PC or tablet. The present invention relates to a noise reduction technology incorporated into this imaging system. The final image obtained is displayed on a display device (W).

[0027] 3, an ultrasonic imaging device according to a second embodiment of the present invention includes a third detection device P3' or a fourth detection device R3 in which a plurality of ultrasonic transducers are arranged two-dimensionally with the same arrangement of transmitters and receivers, a control device 2 connected to either the third detection device P3' or the fourth detection device R3 by a cable C, and a server device S that receives and processes data of reflected waves received and transmitted by the control device 2. In the second embodiment, a processing device 1 and control device 2 connected by cable C to either of the two detection devices P3', R3 includes an electrostatic display device M3 that also serves as an input device I3, and the processing device 1 and control device 2 transmits and receives wireless signals to and from the server device S.

[0028] (Detection Device) The detection device may have a rectangular detection surface shape like the first detection device P1, or may have a circular detection surface shape like the second detection device P2. The ultrasonic imaging device of the first embodiment has detection devices with two types of detection surface shapes, the first detection device P1 and the second detection device P2, which can be connected in parallel. The ultrasonic imaging device of the second embodiment has detection devices with two types of detection surface shapes, the third detection device P3' / fourth detection device R3, which can be connected independently by replacing them.

[0029] Fig. 4 shows a flow chart of signal processing of the shear wave imaging system of the present invention. The signal processing of this shear wave imaging system will be explained. First, when excitation is performed with a sine wave of a certain fixed frequency fv, the I and Q signals obtained after quadrature detection have two characteristics: "signal periodicity (hereinafter referred to as periodicity)" in which the same waveform is repeated with a period T = 1 / fv, and "signal symmetry (hereinafter referred to as symmetry)" in which the signs are different in the first half and the second half of one period but the absolute values ​​are the same. This characteristic cannot be obtained by conventional blood flow measurement, and the signals having these characteristics are extracted and emphasized to reproduce the shear wave image using the CD-SWI method.

[0030] Two methods are used to extract and emphasize signals with periodicity and symmetry. These are the main points of the present invention. These two methods are an MTI filter specialized for sinusoidal excitation that focuses on 1-periodicity, and flow velocity estimation specialized for sinusoidal excitation that focuses on 2-symmetry and periodicity. First, as shown in Fig. 2, an "MTI filter specialized for sinusoidal excitation" that passes only signals near frequency fv is applied to each of the quadrature detection signals I and Q, and then a "flow velocity estimation specialized for sinusoidal excitation" is performed that focuses on the periodicity of the signal and the symmetry of the signal over a half cycle (signs are different but the absolute value has the same width).

[0031] In order to explain the operation of the present invention, we will first show oversampling in the CD-SWI method (extension to oversampling of frequency conditions), and then show the noise reduction technology specialized for sinusoidal vibration, which is the main feature of the present invention.

[0032] (Oversampling in the CD-SWI method (extension of frequency conditions to oversampling)) The frequency condition for the CD-SWI method is shown in Equation 1. This condition is required for the wavefront of the shear wave to appear on the color flow image in the CD-SWI method. However, f ν :Excitation frequency, f prf : ultrasonic pulse repetition frequency, m: 0 or an integer.

[0033]

number

[0034] Equation 1 can be rewritten as follows:

[0035]

number

[0036]

number

[0037] Equation 3 can also be written as Equation 4 below.

[0038]

number

[0039] At this time, the number of ultrasonic pulses in one period is given by the reciprocal of the excitation frequency, N s is given by the following Equation 5.

number

[0040] (Noise reduction specialized for sine wave excitation) Next, we will explain noise removal specialized for sinusoidal vibration. For stiffness images, sinusoidal vibration is performed at a frequency expressed by the above formula 4. Therefore, the obtained signal has unique characteristics, and by extracting or emphasizing only the signal with this characteristic, the noise component can be effectively suppressed. Specifically, we introduce two methods: an MTI filter specialized for sinusoidal excitation and flow velocity estimation specialized for sinusoidal excitation.

[0041] ((b-1) MTI (Moving Target Indicator) Filter specialized for sinusoidal excitation) First, we used MTI (Moving Target Induction) which is specialized for sine wave excitation. This section explains the Moving Target Indicator (MTI) filter, a commonly used blood flow measurement filter. The MTI filter (Moving Target Indicator Filter) is a high-pass filter with a cutoff frequency of, for example, 50 Hz, in order to suppress signals caused by body movement and pulsation, which are very low frequency components.

[0042] However, for stiffness imaging using the CD-SWI imaging method, the excitation frequency is close to an integer multiple frequency (formula 4) synchronized with the PRF (pulse repetition frequency). For example, if the PRF is 1000Hz, the excitation frequency will be around 62.5Hz (at this time, the excitation frequency is 1 / 16 of the PRF). Because of this, the spectrum of the excitation frequency components of the I and Q signals becomes large, so if a bandpass filter with the excitation frequency as the passband is used as the MTI filter, the noise components contained in the signal can be effectively suppressed.

[0043] ((b-2) Flow velocity estimation specialized for sinusoidal excitation) Next, (b-2) flow velocity estimation specialized for sinusoidal excitation will be explained. Since excitation in the CD-SWI method is performed with a sine wave, the recorded signals (I, Q signals) have periodicity (period Tv, which is the inverse of the excitation frequency) and signal symmetry with respect to the signal within one period (within the signal of one period, the signs of the excitation signals in the front 1 / 2 period and the rear 1 / 2 period are reversed, but the absolute values ​​are the same). Therefore, noise components can be suppressed by emphasizing a signal that has a period Tv and is symmetric within Tv to estimate the flow velocity. To emphasize such a signal, we introduce a two-step flow velocity estimation method consisting of step 1: deriving the autocorrelation of the I and Q signals, and step 2: estimating the flow velocity.

[0044] (Step 1: Derive the autocorrelation of I and Q signals) First, in step 1, the signal is enhanced by deriving the autocorrelation of the I and Q signals. As shown in the above formula 5, N s Since two ultrasonic waves can be received, the autocorrelation Is is calculated using the following formulas 6 and 7 for the signals I(i) and Q(i) (i is the reception number) obtained by quadrature detection of the received ultrasonic waves.

[0045]

number

[0046]

number

[0047] (Step 2: Estimating flow velocity) Next, in step 2, the signal is enhanced by estimating the flow velocity. The flow velocity value caused by the excitation is calculated from Is using the following formulas 8 and 9.

[0048]

number

[0049]

number

[0050] In this method, the signal averaging shown in Equation 7 above contributes to suppressing the noise component.

[0051] The above formulas 6, 7, 8, and 9 describe the signal processing for one cycle of the excitation frequency. When a signal with multiple cycles can be used, noise can be reduced by applying the addition process of formula 7 to the signal within each cycle and then estimating the flow velocity using formulas 8 and 9.

[0052] The averaging process taking into consideration the sign shown in Equation 7 is shown in Fig. 5 and Fig. 6. Fig. 5 shows the case where the oversampling rate in Equation 7 is n=4, and Fig. 6 shows the case where n=2.

[0053] (Principles and Effects of Two Noise Reduction Methods) The principles and effects of the two methods introduced for noise reduction are summarized in Figure 7.

[0054] (Numerical Simulation) A numerical simulation was performed to evaluate the effect of the noise reduction technology of the present invention. In the numerical simulation, Gaussian white noise was added independently to the quadrature detection signals (I, Q signals) obtained from an ultrasound diagnostic device, and flow velocity maps were obtained using a conventional method without noise reduction processing and a method with noise reduction processing. The shear wave was assumed to propagate horizontally across the screen, and the wavelength was set to a value at which four areas with high velocity values ​​(vertical stripes) appeared horizontally across the screen. The results are shown in Figure 8.

[0055] The top three figures in Figure 8 are images obtained using the conventional method without noise reduction, while the bottom three figures show the results when noise reduction specialized for sinusoidal vibration according to the present invention is introduced, with a comparison made by changing the signal to noise power ratio to 0.25, 1, and 4. Comparing the top and bottom figures, regardless of the signal to noise power ratio, when noise reduction specialized for sinusoidal vibration is introduced, the four vertical stripes caused by the phase change of the shear wave appear more clearly, confirming the effectiveness of this method.

[0056] Fig. 9 shows an evaluation graph quantitatively evaluating the effectiveness of the noise reduction technology (ultrasonic image processing) of the present invention. The propagation velocity of the shear wave (quantitative value of stiffness) was specified as the evaluation quantity. The vertical axis of Fig. 9 is the coefficient of variation (standard deviation divided by average value) of the propagation velocity estimation value, and the smaller this value, the more stable the velocity estimation can be performed. On the other hand, the horizontal axis of Fig. 9 is the noise power normalized by the signal power, and the larger this value, the larger the added noise. The processing method of the present invention exhibits higher noise resistance than conventional methods. For example, when comparing the coefficient of variation of the velocity estimates at 5%, the conventional method can tolerate a noise power normalized by the signal power of only 2.6, whereas the processing method of the present invention can tolerate a noise power of up to 60. This represents a 23-fold improvement in noise resistance.

[0057] Figures 10 and 11 show examples of output images from dual excitation of the biological trapezius muscle of subjects A and B. In this analysis, I and Q signals were extracted from a tablet-type ultrasound imaging device, and the wavefront of the shear wave was reconstructed from these signals. The ultrasound repetition frequency was 1000 Hz, and the excitation frequency was 62.2 Hz, which corresponds to an oversampling rate of n=4. Strictly speaking, an excitation frequency of 62.5 Hz meets the condition of n=4, but since the CD-SWI method has a tolerance of about 5 Hz above and below the excitation frequency suitable for imaging, imaging is possible even with the frequency used in the experiment.

[0058] Specifically, when vibrations were applied to the trapezius muscles of two subjects using a small vibrator, the ultrasound signals received from the shallow (0-24 mm) and deep (24-48 mm) areas were output to a tablet-type ultrasound imaging device shown in the photograph and recorded. Each of the 8 figures This is the B-mode image at this time. do.

[0059] In the conventional method, due to the influence of noise, very fine high-frequency patterns were generated as artifacts in the shear wave propagation diagram. On the other hand, the processing method of the present invention effectively suppresses noise, and no artifacts are generated as in the conventional method. The shear wave propagating in the trapezius muscle can be clearly output and recorded as a two-dimensional image.

[0060] (Action and effect) When attempting to visualize shear waves propagating inside a biological tissue using the CD-SWI method, an imaging system for biological stiffness, it can be difficult to obtain an image of the shear waves due to the influence of noise, such as noise from the biological tissue, such as pulsation and body movement, noise from ultrasound speckle, and noise from the ultrasound receiving device.

[0061] Since the CD-SWI method uses a sine wave excitation, the obtained ultrasound signal exhibits characteristics that are not seen in general blood flow imaging. These characteristics are periodicity with a period equal to the inverse of the excitation frequency, and symmetry of the signal within one period.

[0062] By using an imaging device incorporating a method for suppressing noise by focusing on the periodicity and symmetry of this signal, clear images of shear waves can be obtained using the CD-SWI method even in high-noise environments.

[0063] (6)(Other) In addition to the above, the ultrasonic signal received by each transducer is spectrally analyzed, and the foreign object is classified into one of multiple object spectrum models with different sizes or hardness by a multi-layer neural network analysis after learning, and is displayed on a map in a color or shape that corresponds one-to-one to the classified object spectrum model. The map is displayed according to the detection surface, and each of the multiple receivers arranged two-dimensionally and the adjacent receivers detect signals by overlapping, so that the general shape and thickness (depth) of the foreign object can be clearly recognized.

[0064] (Ultrasound Imaging Method) The ultrasonic imaging method of the present invention includes any one of the ultrasonic imaging devices described above for acquiring non-contact probe data by the ultrasonic imaging device, and an analysis device for analyzing the acquired probe data. The ultrasonic imaging device in the ultrasonic imaging method is used for muscle separation tests as well as for detecting tumors or hardening in internal organs (FIG. 12). Fig. 12 is a graph showing the change in stiffness of the trapezius muscle due to exercise load, as measured by the ultrasonic imaging device of the present invention. When the exercise load was applied by performing 10 rounds of dumbbell shrugs with a weight of 5 kg each time, the propagation velocity of the shear wave was examined, and it was found that the stiffness of the trapezius muscle had increased to about twice the propagation velocity before the load was applied. Fig. 13 shows a comparison graph of the exploration depth of the stiffness of the trapezius muscle due to exercise load using the ultrasonic imaging device of the present invention. The vertical axis indicates the propagation velocity before the load and immediately after the first exercise, and the horizontal axis indicates the propagation velocity difference Vt between the shallow and deep parts. Even for the same part of the trapezius muscle of the same subject, it is confirmed that the propagation velocity tends to decrease in the shallow part, while the propagation velocity increases at a nearly constant rate in the deep part. It is also confirmed that there is variation in the change in the propagation velocity in the deep part. Figure 14 is a correlation graph between the difference in propagation velocity immediately after the first exercise load and the difference in propagation velocity between the shallow and deep parts. Vt = (propagation velocity in the shallow part) - (propagation velocity in the deep part), and the difference in propagation velocity from before loading to immediately after the first exercise is defined on the vertical axis, and the difference in propagation velocity Vt between the shallow and deep parts is defined on the horizontal axis. The correlation coefficient is 0.83, confirming that there is a certain correlation. Figure 15 is a graph showing an example of the change in shear wave propagation velocity when saline is injected into painful fascia under ultrasound echo guidance. It can be seen that the shear wave propagation velocity increases at a constant rate over time by injecting saline.

Claims

1. a vibrator that applies a sinusoidal vibration of a single specific frequency in a specific direction within the living body while being in contact with the epidermis of the living body; A probe in which multiple ultrasonic transducers are arranged two-dimensionally with the same arrangement for both transmitters and receivers; a signal processing device that generates and outputs an ultrasonic image signal of a shear wave from the original signal received by the probe; A display device that displays an ultrasonic image signal from the signal processing device, The signal processing device includes: An ultrasonic imaging device characterized in that only sine wave signals of the same frequency as a specific frequency of the sinusoidal vibration and the bands surrounding the specific frequency are extracted and emphasized, and a shear wave propagation velocity is estimated for the extracted and emphasized sine wave signals based on the periodicity of the signal and the symmetry of the absolute value of the signal in a half cycle, and a shear wave propagation diagram image consisting of the estimated shear wave propagation velocity at each point within a predetermined two-dimensional region corresponding to the two-dimensional arrangement of a probe in contact with the epidermis of a living body is continuously generated as a reconstructed image of the shear wave.

2. The signal processing device performs band pass filtering to pass only sinusoidal signals having a frequency range corresponding to the specific frequency, the sinusoidal signals having a frequency that is an integer multiple of the specific frequency and a frequency range before and after the specific frequency; a flow velocity estimation step of estimating a flow velocity value of a shear wave propagation velocity due to the amplified signal, which is obtained in response to a sinusoidal signal caused by vibration excitation in a living body, based on the amplified signal, for a specific signal having periodicity and symmetry in a half cycle in the received original signal, by amplifying the pulse repetition frequency of the ultrasound by deriving the autocorrelation of the specific signal having symmetry, and

3. The signal processing device includes: A B-mode image of the two-dimensional region obtained by converting the original signal into brightness in response to the acquisition time of the original signal of the probe is generated in real time for a predetermined number of buffers, and is continuously stored and output; generating shear wave propagation diagrams corresponding to the acquisition times of the original signals of the probe in real time in a number equal to or less than the predetermined number of buffers, and continuously or intermittently storing and outputting the shear wave propagation diagrams; 2. The ultrasonic imaging device according to claim 1, wherein said display device continuously displays a B-mode image of a predetermined two-dimensional region and a shear wave propagation diagram as a superimposed image, in synchronization with each other in accordance with acquisition times.

4. The vibrator excites a specific signal having a plurality of periods, The signal processing device derives an autocorrelation value by performing an addition process based on autocorrelation for each specific signal of each excitation period, and calculates an autocorrelation value corresponding to each of the specific multiple periods; 3. The ultrasonic imaging apparatus according to claim 1, wherein the estimated flow velocity value is obtained by comparing average values ​​of the autocorrelation values ​​corresponding to each of a plurality of periods.

5. 5. The ultrasonic imaging device according to claim 1, further comprising a connecting tool for connecting the transmitting and receiving parts of the probe and the excitation part of the excitation device so that the transmitting and receiving parts of the probe and the excitation part of the excitation device are oriented in parallel directions and are maintained at a constant distance and at an angle within a constant range.

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