JP2023084300A - Ultrasound diagnostic apparatus, control method for ultrasound diagnostic apparatus, and control program of ultrasound diagnostic apparatus - Google Patents

Abstract

To provide an ultrasound diagnostic apparatus capable of generating a color Doppler image of high image quality without lowering a frame rate when a transmission/reception condition of an ultrasonic wave is changed by a user.SOLUTION: An ultrasound diagnostic apparatus causes an ultrasonic probe to perform a first ultrasonic scan related to a B mode and a second ultrasonic scan related to a C mode, and generates a color Doppler image with a blood flow image superimposed on a B mode image. When generating the blood flow image, an ensemble number acquired in one-time second ultrasonic scan is determined to be an ensemble number suited for performing a target frame rate on the basis of a transmission/reception condition of ultrasonic waves in the first ultrasonic scan and the second ultrasonic scan designed by a user, and a group of time serial reflection wave data which combine time-serial ensemble data obtained in a plurality of second ultrasonic scans in a temporal direction and increases the ensemble number.SELECTED DRAWING: Figure 4

Description

The present disclosure relates to an ultrasonic diagnostic apparatus, an ultrasonic diagnostic apparatus control method, and an ultrasonic diagnostic apparatus control program.

An ultrasonic diagnostic apparatus transmits ultrasonic waves into the inside of a subject using an ultrasonic probe, and receives reflected ultrasonic waves (echoes) caused by differences in acoustic impedance of the tissue of the subject. Furthermore, based on the electrical signals obtained from this reception, an image showing the internal tissue structure of the subject is generated and displayed on the monitor. An ultrasonic diagnostic apparatus is widely used for morphological diagnosis of a living body because it is less invasive to a subject and can observe the state of body tissues in real time using tomographic images or the like.

An ultrasonic diagnostic apparatus is equipped with a color flow mapping (CFM) method. In the CFM method, the Doppler shift (frequency shift) generated in the echo due to the movement of body tissues such as blood flow is detected, and the velocity information and power information are converted into a two-dimensional tomographic image (that is, a B-mode image). Perform superimposed display.

In general, the CFM method involves imaging information obtained from blood flow. Therefore, an MTI (Moving Target Indicator) filter is used to extract blood flow information components (hereafter referred to as “blood flow components”) contained in echoes, and the movement of tissues and stationary tissues are extracted from echoes. (hereinafter referred to as "clutter component") is removed.

As this MTI filter, for example, in addition to an FIR filter using the difference in average velocity between a blood flow component and a clutter component, an adaptive MTI filter that changes coefficients according to an input signal is used. The adaptive MTI filter obtains the velocity of the tissue from the signal before the MTI filter input and obtains a signal whose phase difference has been canceled.

In recent years, as this type of adaptive MTI filter, principal component analysis is performed using a correlation matrix from the Doppler signal before input to the MTI filter, and based on the principal component (i.e., eigenvector) of each order, the blood flow component and clutter An eigenvector-type MTI filter that discriminates between blood flow components and thereby obtains a blood flow image from which clutter components are removed (see, for example, Patent Document 1). The eigenvector MTI filter is more useful than an FIR filter or the like in that it can remove clutter components even when the frequency bands of the blood flow component and the clutter component overlap.

FIG. 1 is a diagram for explaining processing of a general eigenvector type MTI filter. In FIG. 1, a blood flow image in which only the eigenvectors of the 0th order component are reduced, a blood flow image in which the eigenvectors of the 0th to 1st order components are reduced, a blood flow image in which the eigenvectors of the 0th to 2nd order components are reduced, . Blood flow images with reduced eigenvectors of the next to n-th order components (the 0th to 13th order components in FIG. 1) are shown in order from the upper left to the lower right.

In this type of eigenvector MTI filter, for example, an appropriate rank-cut order (eigenvector to be reduced) is determined based on the eigenvalue of each order eigenvector (that is, principal component) obtained by principal component analysis, and the clutter component is Techniques have been taken to obtain an ablated blood flow image.

Specifically, in this type of eigenvector MTI filter, the orders of the eigenvectors are set so that the orders of the multiple eigenvectors calculated by the principal component analysis increase in descending order according to the magnitude of the eigenvalues. Since the clutter signal usually has a higher signal strength (that is, eigenvalue) than the blood flow signal, the low-order eigenvector is the eigenvector related to the clutter signal, and the high-order eigenvector is the eigenvector related to the blood flow component. Orders are assigned to the eigenvectors such that In the eigenvector-type MTI filter, for example, eigenvectors of orders whose eigenvalues are equal to or greater than a threshold value are regarded as clutter components, and rank-cut orders are determined. For example, FIG. 1 shows a mode in which the 4th order component is determined as the rank cut order, and here, the blood flow image with the eigenvectors of the 0th to 4th order components reduced is the blood flow image to be displayed. .

JP 2014-158698 A

By the way, in this type of ultrasonic diagnostic apparatus, there is a demand that the user himself/herself can change the transmission/reception conditions of ultrasonic waves when generating a color Doppler image in consideration of the examination object and examination conditions at that time. .

Such ultrasonic transmission/reception conditions include, for example, transmission/reception line density and transmission/reception depth in ultrasonic scanning for generating a B-mode image (hereinafter referred to as "B-mode scanning" or "first ultrasonic scanning"), and , transmission/reception line density, transmission/reception depth, and region of interest (ROI) width in ultrasonic scanning (hereinafter referred to as “C mode scanning” or “second ultrasonic scanning”) for generating a blood flow image , and flow velocity range.

However, when the transmission/reception conditions of such ultrasonic waves are changed, the frame rate for generating a color Doppler image may be slowed down or the image quality of the color Doppler image may be degraded unintentionally by the user. It's becoming

For example, a user may want to obtain a clearer C-mode image by increasing the transmission/reception line density during C-mode scanning. However, in this case, the transmission/reception time required for one C-mode scan becomes long, and this slows down the frame rate greatly.

Further, for example, the user may set a small flow velocity range during C-mode scanning in order to observe blood flow at a low flow velocity. However, even in this case, since the pulse repetition frequency is reduced by reducing the flow velocity range (that is, the pulse repetition interval is increased), the transmission/reception time required for one C-mode scan becomes long. , and the frame rate will drop significantly.

A decrease in the frame rate of such color Doppler images leads to a decrease in the visibility of tissue and blood flow movement, and hinders accurate ultrasound examination. That is, in this type of ultrasonic diagnostic apparatus, there is generally a trade-off relationship between the frame rate and the image quality, and either the frame rate or the image quality of the color Doppler image may be sacrificed according to the user's settings. It may become

The present disclosure has been made in view of the above problems, and generates a high-quality color Doppler image without lowering the frame rate when the user changes the transmission/reception conditions of ultrasonic waves. It is an object of the present invention to provide an ultrasonic diagnostic apparatus, a method for controlling the ultrasonic diagnostic apparatus, and a control program for the ultrasonic diagnostic apparatus.

The main disclosure that solves the above-mentioned problems is
A color Doppler image obtained by alternately performing a first ultrasonic scan in B mode and a second ultrasonic scan in C mode with respect to the ultrasonic probe and superimposing a blood flow image on the B mode image is obtained. An ultrasound diagnostic apparatus that generates
The C-mode image generating unit that generates the blood flow image,
Based on the ultrasonic transmission and reception conditions in the first ultrasonic scan and the second ultrasonic scan specified by the user, the number of ensembles to be acquired in one second ultrasonic scan to achieve the target frame rate an ensemble number determination unit that determines the number of ensembles suitable for
an ensemble data combining unit that combines temporally continuous ensemble data obtained by a plurality of the second ultrasound scans in the time direction to generate a time-series reflected wave data group in which the number of ensembles is increased;
an MTI filter generator that performs principal component analysis on the time-series reflected wave data group and calculates filter coefficients of the MTI filter based on a plurality of eigenvectors obtained by the principal component analysis;
an MTI filter processing unit that applies the MTI filter to the time-series reflected wave data group to extract a blood flow signal for generating the blood flow image;
An ultrasonic diagnostic apparatus comprising:

Also, in other aspects,
A color Doppler image obtained by alternately performing a first ultrasonic scan in B mode and a second ultrasonic scan in C mode with respect to the ultrasonic probe and superimposing a blood flow image on the B mode image is obtained. A control method for an ultrasonic diagnostic apparatus that generates
When generating the blood flow image, based on the ultrasonic transmission and reception conditions in the first ultrasonic scan and the second ultrasonic scan specified by the user, the ensemble acquired in one second ultrasonic scan A first process of determining the number of ensembles suitable for achieving the target frame rate;
A second process of generating a time-series reflected wave data group in which the number of ensembles is increased by combining temporally continuous ensemble data obtained by a plurality of the second ultrasonic scans in the time direction;
a third process of performing principal component analysis on the time-series reflected wave data group and calculating filter coefficients of an MTI filter based on a plurality of eigenvectors obtained by the principal component analysis;
a fourth process of applying the MTI filter to the time-series reflected wave data group to extract a blood flow signal for generating the blood flow image;
is a control method for an ultrasonic diagnostic apparatus that executes

Also, in other aspects,
A color Doppler image obtained by alternately performing a first ultrasonic scan in B mode and a second ultrasonic scan in C mode with respect to the ultrasonic probe and superimposing a blood flow image on the B mode image is obtained. A control program for an ultrasonic diagnostic apparatus that generates
When generating the blood flow image,
Based on the ultrasonic transmission and reception conditions in the first ultrasonic scan and the second ultrasonic scan specified by the user, the number of ensembles to be acquired in one second ultrasonic scan to achieve the target frame rate A first process of determining the number of ensembles suitable for
A second process of generating a time-series reflected wave data group in which the number of ensembles is increased by combining temporally continuous ensemble data obtained by a plurality of the second ultrasonic scans in the time direction;
a third process of performing principal component analysis on the time-series reflected wave data group and calculating filter coefficients of an MTI filter based on a plurality of eigenvectors obtained by the principal component analysis;
a fourth process of applying the MTI filter to the time-series reflected wave data group to extract a blood flow signal for generating the blood flow image;
is a control program for an ultrasonic diagnostic apparatus that executes

According to the ultrasonic diagnostic apparatus according to the present disclosure, even when the user changes the transmission/reception conditions of ultrasonic waves when generating a color Doppler image, high image quality can be obtained without causing a decrease in the frame rate. It is possible to generate color Doppler images.

A diagram explaining the processing of a general eigenvector type MTI filter 1 is a schematic block diagram showing the configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention; FIG. 1 is a block diagram showing the functional configuration of a C-mode image generator according to an embodiment of the present invention; FIG. 1 is a diagram showing the internal configuration of an MTI filter according to an embodiment of the present invention; FIG. Diagram showing the relationship between the input and output of the MTI filter FIG. 4 is a diagram showing a method of calculating MTI filter coefficients of an MTI filter; FIG. 4 is a diagram showing the data structure of ensemble data used to obtain a C-mode image of one frame; FIG. 2 is a diagram for explaining basic color Doppler image generation processing in an ultrasonic diagnostic apparatus according to an embodiment of the present invention; FIG. 5 is a diagram for explaining data combining processing in the ensemble data combining unit according to one embodiment of the present invention; A diagram schematically showing the data combination processing of FIG. 9 FIG. 2 is a diagram showing an overview of the operation of the ultrasonic diagnostic apparatus according to one embodiment of the present invention; A diagram showing an example of a display screen of the user interface for the user to set the target frame rate A diagram showing the relationship between the number of ensembles acquired in one C-mode scan and the filter performance in the MTI filter (eigenvectors obtained in the MTI filter). 4 is a flow chart showing processing for updating transmission/reception conditions of ultrasonic waves in an ultrasonic diagnostic apparatus according to an embodiment of the present invention; A blood flow image (lower figure) obtained when filtering in the MTI filter 73 is performed using the ensemble data data-coupled by the ensemble data coupling unit according to one embodiment of the present invention, and the ensemble data coupling unit A diagram showing a comparison of a blood flow image (upper figure) obtained when filtering is performed by the MTI filter using ensemble data obtained by one C-mode scan without data combination. A diagram explaining general filter characteristics of an eigenvector type MTI filter

Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functions are denoted by the same reference numerals, thereby omitting redundant description.

[Overall Configuration of Ultrasound Diagnostic Apparatus]
First, referring to FIGS. 2 to 4, the overall configuration of an ultrasonic diagnostic apparatus 1 according to one embodiment will be described.

FIG. 2 is a schematic block diagram showing the configuration of the ultrasonic diagnostic apparatus 1 according to this embodiment. FIG. 3 is a block diagram showing the functional configuration of the C-mode image generator 7 according to this embodiment.

An ultrasonic diagnostic apparatus 1 is installed in a medical institution such as a hospital, and is an apparatus that generates an ultrasonic image of a subject such as a living body of a patient, which is an object to be measured. The ultrasonic diagnostic apparatus 1 is configured by connecting an ultrasonic probe 101 to an ultrasonic diagnostic apparatus main body 100 .

The ultrasonic diagnostic apparatus main body 100 includes an operation unit 2, a transmission unit 3, a reception unit 4, a B (Brightness) mode image generation unit 5, an ROI (Region Of Interest) setting unit 6, a C mode An image generation unit 7 , a display processing unit 8 , a control unit 9 , a storage unit 10 and a display unit 11 are provided.

The ultrasonic probe 101 has a plurality of transducers (piezoelectric transducers) 101a arranged in a one-dimensional direction. It converts it into sound waves and produces an ultrasound beam. Therefore, the user can irradiate the inside of the subject with an ultrasound beam by placing the ultrasound probe 101 on the surface of the subject. The ultrasonic probe 101 receives reflected ultrasonic waves from the inside of the subject, converts the reflected ultrasonic waves into received electric signals with a plurality of transducers 101a, and supplies the received electric signals to the receiving unit 4, which will be described later.

In the present embodiment, a linear ultrasonic probe 101 in which a plurality of transducers 101a are arranged in a one-dimensional direction will be described as an example, but the present invention is not limited to this. For example, a convex type or sector type ultrasonic probe 101 in which a plurality of transducers 101a are arranged in a one-dimensional direction, an ultrasonic probe 101 in which a plurality of transducers 101a are arranged two-dimensionally, It is also possible to use an ultrasonic probe 101 or the like in which a plurality of transducers 101a arranged in a one-dimensional direction oscillate. Under the control of the control unit 9, the transmission unit 3 selects the transducer 101a used by the ultrasonic probe 101, and individually changes the timing and voltage value to apply voltage to the transducer 101a. , the transmission depth position and transmission direction of the ultrasonic beam transmitted by the ultrasonic probe 101 can be controlled.

Also, the ultrasound probe 101 may include a part of the functions of the transmitting unit 3 and the receiving unit 4, which will be described later. For example, the ultrasonic probe 101 is driven within the ultrasonic probe 101 based on a control signal for generating a drive signal output from the transmission unit 3 (hereinafter referred to as a “transmission control signal”). This drive signal is converted into ultrasonic waves by the transducer 101a, the received reflected ultrasonic waves are converted into received electric signals, and the received signals described later are generated based on the received electric signals in the ultrasonic probe 101. is generated.

Further, the ultrasonic probe 101 is generally electrically connected to the ultrasonic diagnostic apparatus main body 100 via a cable, but is not limited to this. The child 101 may be configured to transmit and receive transmission signals and reception signals to and from the ultrasonic diagnostic apparatus main body 100 by wireless communication such as UWB (Ultra Wide Band). However, in the case of such a configuration, it goes without saying that the ultrasonic diagnostic apparatus main body 100 and the ultrasonic probe 101 are provided with communication units capable of wireless communication.

The operation unit 2 receives input from the user and outputs commands based on the user's input to the control unit 9 . The operation unit 2 displays an image (B-mode image) in which the amplitude of the reflected ultrasound is represented by brightness (luminance), or displays a color flow mode image (C-mode image) superimposed on the B-mode image. Allow the user to select which of the modes to run. The operation unit 2 also includes a function of accepting a user's designation input of the position of the ROI on which the C-mode image is to be displayed on the B-mode image. Further, as the C-mode image to be displayed, a V-mode for color-displaying the flow velocity and direction of the blood flow by a blood flow velocity V as a blood flow signal indicating the state of the blood flow, and a blood flow signal as the blood flow signal. P mode for color display of blood flow power by power P, and VT mode for color display of blood flow velocity and dispersion by blood flow velocity V and dispersion T as a blood flow signal. Suppose you have an image. It is assumed that when the operation unit 2 receives an input of the C mode from the user, it also receives an input of that display mode. Note that the display mode of the C-mode image may include a T (dispersion) mode, a dP (directed power) mode, and the like. Thus, C mode includes color Doppler mode (V mode, VT mode, etc.) and power Doppler mode (P mode, etc.).

Further, the operation unit 2 may include a touch panel that is provided on the display screen of the display unit 11 and receives touch input from the user.

The transmission unit 3 generates at least a drive signal and performs transmission processing for causing the ultrasound probe 101 to transmit an ultrasound beam. As an example, the transmission unit 3 performs transmission processing to generate a drive signal for transmitting an ultrasonic beam from the ultrasonic probe 101 having the transducer 101a, and transmits the signal to the ultrasonic probe 101 based on this drive signal. By supplying a high-voltage drive signal generated at a predetermined timing, the transducer 101a of the ultrasonic probe 101 is driven. Accordingly, the ultrasound probe 101 can irradiate the subject with an ultrasound beam by converting the drive signal into ultrasound.

Under the control of the control unit 9, when the color Doppler image display is turned on, the transmission unit 3 performs transmission processing for displaying a B-mode image, and also performs C-mode processing for displaying a blood flow image. Transmission processing is performed. At this time, the transmission unit 3 alternately performs B-mode scanning and C-mode scanning, for example. In C-mode scanning, ultrasonic beams are repeatedly transmitted in the same direction (same line) n times (n is 16, for example, 10-odd times) (the number of repetitions is called the number of ensembles), and the ultrasonic beams are transmitted to the ROI. The ROI set by the setting unit 6 is transmitted in all directions (all lines). Further, the transmission unit 3 designates additional information for transmission processing for B-mode images or transmission processing for C-mode images at the time of transmission processing, and supplies this additional information to the reception unit 4 .

Under the control of the control unit 9, the reception unit 4 performs reception processing to generate a reception signal as an electrical RF (Radio Frequency) signal based on reflected ultrasonic waves. For example, the receiving unit 4 receives the reflected ultrasonic waves with the ultrasonic probe 101, and amplifies the received electric signals converted based on the reflected ultrasonic waves, A/D converts them, and phases them. A reception signal (sound ray data) is generated by performing addition.

The receiving unit 4 acquires additional information from the transmitting unit 3, and if the acquired additional information is additional information for a B-mode image, supplies a received signal to the B-mode image generating unit 5, and the acquired additional information is C mode. If it is additional information for an image, the received signal is supplied to the C-mode image generator 7 . Hereinafter, the received signal for generating a B-mode image will be referred to as a "B-mode received signal", and the received signal for generating a C-mode image will be referred to as a "C-mode received signal".

In the present embodiment, the reception unit 4 selects whether the received signal associated with the generated image frame is for a B-mode image or for a C-mode image and supplies it to each block. For example, the B-mode image generation unit 5 and the C-mode image generation unit 7 may select received signals related to the generated image frames.

Under the control of the control unit 9, the B-mode image generation unit 5 performs envelope detection, logarithmic compression, etc. on the B-mode reception signal input from the reception unit 4, adjusts the dynamic range and gain, and performs luminance conversion. By doing so, B-mode image data is generated and output to the display processing unit 8 .

Under the control of the control unit 9, the ROI setting unit 6 sets the region of interest (ROI) of the C-mode image to the transmission unit 3 and the display processing unit 8 according to the ROI designation information input by the user via the operation unit 2. set.

The C-mode image generation unit 7 generates C-mode image data according to the C-mode reception signal input from the reception unit 4 under the control of the control unit 9 and outputs the C-mode image data to the display processing unit 8 .

The C-mode image generation unit 7 includes a quadrature detection circuit 71, a corner turn control unit 72, an MTI filter 73, a correlation calculation unit 74, a data conversion unit 75, a noise removal spatial filter 76, and an inter-frame filter 77. , and a C-mode image converter 78 (see FIG. 3).

The quadrature detection circuit 71 performs quadrature detection on the C-mode reception signal input from the reception unit 4 under the control of the control unit 9, thereby calculating the phase difference between the acquired C-mode reception signal and the reference signal, and ( Acquire the complex) Doppler signals I,Q.

Under the control of the control unit 9, the corner turn control unit 72 converts the Doppler signals I and Q input from the quadrature detection circuit 71 into depth signals from the ultrasonic probe 101 to the subject for each same acoustic line. and the ensemble direction of the repetition number n of ultrasound transmission and reception (hereinafter abbreviated as "repetition number"), and stored in a memory (not shown), Doppler signals I and Q for each depth are read in the ensemble direction.

The received signals (Doppler signals I and Q) contain not only signal components of blood flow necessary for C-mode image generation, but also unnecessary information (clutter components) such as blood vessel walls and tissues. Under the control of the control section 9, the MTI filter 73 filters the Doppler signals I and Q input from the corner turn control section 72 to remove clutter components.

Next, the internal configuration of the MTI filter 73 will be described with reference to FIGS. 4 to 11. FIG. The MTI filter 73 according to the present embodiment is the eigenvector type MTI filter described above.

FIG. 4 is a diagram showing the internal configuration of the MTI filter 73 according to this embodiment. FIG. 5 is a diagram showing the input/output relationship of the MTI filter 73. As shown in FIG. FIG. 6 is a diagram showing a method of calculating the MTI filter coefficients of the MTI filter 73. As shown in FIG. FIG. 7 is a diagram showing the data configuration of ensemble data used to obtain a C-mode image of one frame.

The MTI filter 73 has a principal component analysis execution unit 731 , a filter coefficient calculation unit 732 , a filtering processing unit 733 , an ensemble data number determination unit 734 and an ensemble data combination unit 735 . The principal component analysis execution unit 731 and filter coefficient calculation unit 732 correspond to the "MTI filter generation unit" of the present invention.

First, basic processing of the MTI filter 73 will be described with reference to FIGS. 4 to 7. FIG.

The basic processing of the MTI filter 73 is realized by a principal component analysis execution unit 731, a filter coefficient calculation unit 732, and a filtering processing unit 733, and these basic calculation methods themselves are similar to the processing of the MTI filter according to the prior art. It is the same. However, in the MTI filter 73 according to the present embodiment, the ensemble data Sp obtained during one C-mode scan output from the corner turn control unit 72 is combined by the ensemble data combining unit 735 for a plurality of C-mode scans. are combined to form ensemble data with a large number of ensembles (described later with reference to FIG. 10). It is characterized in that the process can be executed by the unit 733 (details will be described later).

Generally, in the color Doppler method, ultrasonic waves are scanned in a region of interest while transmitting and receiving ultrasonic waves in the same direction a plurality of times. Extract the flow signal. A data string of reflected wave signals (reflected wave data) obtained by transmitting and receiving ultrasonic waves in the same direction during one ultrasonic scan is called ensemble data. Also, the number of repetitions of ultrasonic wave transmission/reception performed in the same direction during one ultrasonic scan is called the ensemble number. The number of ensembles in a general color Doppler method is about 5 to 16.

The Doppler signals I and Q output from the corner turn control unit 72 for the number of times of repetition n (the number of ensembles n) are assumed to be ensemble data Sp. At this time, the ensemble data Sp is expressed as time-series n pieces of input data x(0), x(1), . . . , x(n-1) obtained from the same position. It is assumed that x(0), x(1), .

The corner turn control section 72 outputs the ensemble data Sp to the ensemble data combining section 735 . Here, when the ensemble data combining unit 735 does not perform data combining processing, which will be described later, the ensemble data Sp input from the corner turn control unit 72 to the MTI filter 73 is directly processed by the principal component analysis executing unit 731 and filtering processing. It is sent to section 733 .

The input/output of the MTI filter 73 is represented by the following equation (1), for example (see FIG. 5).
y=A _reg ×x (1)
where y: output vector indicating ensemble _data y(0), y(1), . x: an input vector representing input data x(0), x(1), . . . , x(n-1).

The MTI filter 73 is represented, for example, by MTI filter coefficients A _reg (n×n filter matrix) as shown in the following equation (2) (see FIG. 6).
_Areg =b×G× ^bH (2)
However, b: orthonormal basis (n×n matrix), G: gain matrix (n×n matrix), b ^H : orthonormal basis of b and Hermitian transpose (n×n matrix).

The orthonormal bases b, b ^H for calculating the MTI filter 73 consist of a plurality of eigenvectors obtained by principal component analysis. The orthonormal bases b and b ^H are expressed such that the eigenvector with the largest eigenvalue is of the 0th order, and the order increases in descending order according to the magnitude of the eigenvalue. That is, in the orthonormal basis b, the degree increases as the column number increases. In the orthonormal basis b ^H , the order increases as the row number increases.

_The diagonal components G ₀ , G ₁ , . A diagonal component of 0 corresponds to a reduction rate of 100%, and a diagonal component of 1 corresponds to a reduction rate of 0%. _The diagonal components G ₀ , G ₁ , . The diagonal components G ₀ , G ₁ , _. As the clutter reduction rate of the MTI filter 73 increases, the number of 0s increases in the diagonal components G ₀ , G ₁ , . . . , G _n-1 . However, the diagonal components G ₀ , G ₁ , _.

The gain matrix G (diagonal components G ₀ , G ₁ , _. set.

The principal component analysis execution unit 731, the filter coefficient calculation unit 732, and the filtering processing unit 733 execute the above arithmetic processing, for example.

A principal component analysis execution unit 731 executes principal component analysis on a group of time-series reflected wave data within the region of interest obtained during C-mode scanning, and calculates a plurality of eigenvectors forming orthonormal bases b and b ^H . Calculate

Specifically, the principal component analysis execution unit 731 first receives ensemble data (hereinafter referred to as “ensemble data group Sp1”) of each observation point within the region of interest set in the ROI setting unit 6 from the corner turn control unit 72. ) are acquired, and a matrix C (see equation (3) below) related to the ensemble data group Sp1 and a matrix C ^H of Hermitian transpose of the matrix C are generated. The ensemble _data group Sp1 includes input data x ₀ , x ₁ , . A matrix of M (see FIG. 7). In the ensemble data group Sp1, the ensemble data of each observation point at the k-th observation point out of n repetitions is grouped in units of frames as F1(k−1).

Note that the ensemble data group Sp1 referred to by the principal component analysis execution unit 731 is an ensemble data group obtained by one C-mode scan when the ensemble data combination unit 735 does not perform data combination processing. When the ensemble data combining unit 735 performs data combining processing, an ensemble data group obtained by a plurality of temporally continuous C-mode scans is combined in the time direction to form an ensemble data group with an increased number of ensembles. (described later with reference to FIG. 10).

Next, the principal component analysis execution unit 731 calculates a covariance matrix R from the matrices C and C ^H using Equation (4).
R=C×C ^H (4)

Then, the principal component analysis execution unit 731 solves an eigenvalue problem (ie, Rb=λb) related to the covariance matrix R to calculate eigenvalues and eigenvectors (ie, orthonormal bases b, b ^H ). At this time, the principal component analysis execution unit 731 typically calculates eigenvalues and eigenvectors for n orders corresponding to the number of ensembles. The principal component analysis execution unit 731 then sends the calculated eigenvalues and eigenvectors to the MTI filter coefficient calculation unit 732 .

At this time, the principal component analysis execution unit 731 sets the order of the calculated eigenvectors so that the eigenvector with the largest eigenvalue is the 0th order and the order increases in descending order according to the magnitude of the eigenvalue. Since the clutter signal usually has a higher signal strength (that is, eigenvalue) than the blood flow signal, the low-order eigenvector is the eigenvector related to the clutter signal, and the high-order eigenvector is the eigenvector related to the blood flow component. Orders are assigned to the eigenvectors such that

The MTI filter coefficient calculator 732 calculates the filter coefficients of the MTI filter 73 (that is, the MTI filter coefficient A _Reg ) is calculated.

Note that the gain matrix G referred to by the MTI filter coefficient calculation unit 732 is based on, for example, the rank-cut order specified by the user or the rank-cut order calculated by threshold processing based on the eigenvalue, as described above. , is set. However, considering that there are eigenvectors representing frequency components including both clutter signals and blood flow signals, the gain matrix G is defined by the reduction rate of the eigenvectors of each order (that is, each diagonal component G ₀ , G ₁ , _.

For example, the MTI filtering processing unit 733 applies the input filter coefficient of the MTI filter 73 (that is, the MTI filter coefficient A _Reg ) to the input ensemble data x to obtain the formula (1) Then, ensemble data y after clutter signal removal (that is, Doppler signals I and Q related to blood flow components after clutter signal removal) is calculated. Then, the MTI filtering processor 733 outputs the calculated ensemble data y to the correlation calculator 74 .

Here, the ensemble data x referred to by the MTI filtering processing unit 733 is the ensemble data obtained by one C-mode scanning when the ensemble data combining unit 735 does not perform the data combining processing described later. However, when the ensemble data combining unit 735 performs a data combining process to be described later, the ensemble data obtained by a plurality of temporally continuous C-mode scans are combined in the time direction to create an ensemble with an increased number of ensembles. data (described later with reference to FIG. 10).

Next, with reference to FIGS. 8 to 16, the configuration of the ensemble number determining unit 734 and the ensemble data combining unit 735, and the operation mode of the MTI filter 73 when the ensemble data combining unit 735 performs the data combining process, explain.

FIG. 8 is a diagram for explaining basic color Doppler image generation processing in the ultrasonic diagnostic apparatus 1 . In FIG. 8, the length of the bar in the direction of the time axis represents the time required for one B-mode scan or one C-mode scan.

FIG. 9 is a diagram for explaining data combining processing in the ensemble data combining unit 735. As shown in FIG. FIG. 10 is a diagram schematically showing the data combining process of FIG. 9. FIG. In FIG. 10, the fan mark with a "B" symbol represents one B-mode scan, and the fan mark with a "C" symbol represents one C-mode scan. Also, CF(t) represents a blood flow image obtained when a certain C-mode scan is performed, and CF(t+1) is obtained when the next C-mode scan is performed. represents a blood flow image.

FIG. 11 is a diagram showing an overview of the operation of the ultrasonic diagnostic apparatus 1. As shown in FIG. A specific flowchart for executing the operation of FIG. 11 will be described later with reference to FIG.

Under the control of the control unit 9, the ultrasonic diagnostic apparatus 1 causes the ultrasonic probe 101 to perform B-mode scanning (ultrasonic scanning according to B mode) and C mode scanning (ultrasonic scanning according to C mode). ) are alternately executed, and a color Doppler image is generated by superimposing a blood flow image obtained by C-mode scanning on a B-mode image obtained by B-mode scanning.

At this time, in the normal operation (that is, the operation when the data combining processing by the ensemble data combining unit 735 is not performed), the ultrasonic diagnostic apparatus 1 converts the reflected wave data group obtained by one B-mode scan to the B A mode image is generated, a blood flow image is generated from a group of reflected wave data obtained by one C-mode scan, and these are superimposed to generate a single color Doppler image. Note that one ultrasonic scan (B mode scan, C mode scan) means that the transducer 101a on one end side of the ultrasonic probe 101 and the transducer 101a on the other end side are sequentially driven along the scanning direction. It refers to acquisition of reflected wave data for one frame by one ultrasonic scan.

As shown in FIG. 8, the frame rate of the color Doppler image in the ultrasonic diagnostic apparatus 1 is the transmission/reception time of ultrasonic waves required for executing one B-mode scan and the time required for executing one C-mode scan. It is determined by the sum of the ultrasonic wave transmission/reception time required for The ultrasonic transmission/reception time required for one B-mode scan typically means the density of the transmission/reception line and the display depth of the transmission/reception wave in the B-mode scan (meaning the depth of the object to be measured in the subject). the same). In addition, the transmission and reception time of ultrasonic waves for one C-mode scan is typically the density of transmission and reception lines in C-mode scanning, the display depth of transmission and reception waves, the size of the region of interest, the flow velocity range of the observation target, and the ensemble Determined by number.

In addition, since the density of the transmission/reception line and the size of the region of interest define the number of times of transmission/reception of ultrasonic waves to be executed in one ultrasonic scan, the ultrasonic transmission/reception time required for one ultrasonic scan is affected. give. In addition, since the display depth of the transmission/reception line and the flow velocity range of the observation object define the pulse repetition frequency of the ultrasonic waves, they affect the transmission/reception time of the ultrasonic waves required for one ultrasonic scan. Further, as described above, the number of ensembles determines the number of transmission/reception times of ultrasonic waves in the same direction during C-mode scanning, and thus affects the transmission/reception time of ultrasonic waves for one ultrasonic scanning.

As described above, in general, in the ultrasonic diagnostic apparatus 1, the user can set the density of transmission/reception lines or the display depth of transmission/reception waves in B-mode scanning, the density of transmission/reception lines, the display depth of transmission/reception waves, and the region of interest in C-mode scanning. , or the flow velocity range of the observation target, the frame rate of the color Doppler image changes accordingly (see FIG. 9). In this case, the user changes the transmission/reception conditions of these ultrasonic waves in order to photograph a specific observation target more clearly. frame rate may drop.

In the ultrasonic diagnostic apparatus 1 according to the present embodiment, in order to solve this problem, the target frame rate is secured by automatically adjusting the number of ensembles during C-mode scanning, and then the filter performance of the MTI filter 73 is improved. In order to ensure this (that is, to suppress image quality deterioration of blood flow images due to compression of the number of ensembles), ensemble data is combined. The ensemble number determining unit 734 and the ensemble data combining unit 735 perform such processing.

In FIGS. 9 and 10, as an example, the number of ensembles acquired by the ensemble number determining unit 734 in one C-mode scan is changed from 15 to 5 in accordance with the user's operation to change the transmission/reception conditions of ultrasonic waves. Then, the ensemble data combining unit 735 combines the ensemble data of the three C-mode scans that are temporally continuous in the time direction, and the combined ensemble data is used to obtain a blood flow image for one frame. It shows a mode of ensemble data to be used.

More specifically, the ensemble number determination unit 734 determines the number of ensembles to be acquired in one C-mode scan based on the ultrasonic transmission/reception conditions in the B-mode scan and C-mode scan specified by the user, at the target frame rate. Determine the number of ensembles suitable for realizing

As described above, the number of ensembles acquired in one C-mode scan affects the transmission and reception time of ultrasonic waves for one C-mode scan, so the number of ensembles acquired in one C-mode scan is reduced. By increasing the frame rate of the color Doppler image, it is possible to increase the frame rate. That is, the ensemble number determination unit 734 adjusts the number of ensembles acquired in one C-mode scan, thereby reducing the first transmission/reception time required for performing one B-mode scan and the one C-mode scan. The frame rate of the color Doppler image, which is determined by the sum of the second transmission/reception time required for executing the above, approaches the target frame rate.

In the ultrasonic diagnostic apparatus 1, the user can specify the transmission/reception conditions for ultrasonic waves in B-mode scanning and the transmission/reception conditions for ultrasonic waves in C-mode scanning by performing an input operation using the operation unit 2. there is Here, the ultrasonic transmission/reception conditions in B-mode scanning are, for example, the density of transmission/reception lines and the display depth of transmission/reception waves. Further, the ultrasound transmission/reception conditions in C-mode scanning are typically the density of transmission/reception lines, the display depth of transmission/reception waves, the size of the region of interest, the flow velocity range of the observation target, and the number of ensembles. Note that the number of ensembles in C-mode scanning cannot be specified by the user as a parameter for the ensemble number determination unit 734 to automatically change the settings.

The ensemble number determining unit 734 uses, for example, a B-mode data table (not shown) obtained in advance by experiments or simulations to perform one B-mode scan based on the transmission/reception conditions of ultrasonic waves in the B-mode scan. Estimate the first transmit/receive time required to execute. Further, the ensemble number determining unit 734 uses, for example, a C-mode data table (not shown) obtained in advance by experiments or simulations, from the transmission/reception conditions of ultrasonic waves in C-mode scanning, one C-mode Estimate a second transmit/receive time required to perform the scan. Then, the ensemble number determining unit 734 adds, for example, the first transmission/reception time and the second transmission/reception time, and calculates the reciprocal thereof as the frame rate of the color Doppler image.

In this embodiment, in order to obtain one frame of blood flow image, ensemble data of a plurality of C-mode scans are required. At this time, as shown in FIG. 10, the ensemble data combining unit 735 duplicates the ensemble data obtained by the C-mode scanning performed at a certain timing as the ensemble data for obtaining the blood flow image at the next timing. to use. Therefore, the frame rate of a color Doppler image is defined by the sum of the first transmission/reception time required to perform one B-mode scan and the second transmission/reception time required to perform one C-mode scan. .

At this time, the target frame rate referred to by the ensemble number determination unit 734 may be a value specified by the user, or may be a preset appropriate value. Also, the target frame rate may be the frame rate that was set before the user changed the setting of the transmission/reception conditions of ultrasonic waves.

Note that FIG. 12 is a diagram showing an example of a display screen of a user interface for the user to set the target frame rate. FIG. 12A shows an example of an icon R1 for switching between "ON" (that is, set) and "OFF" (that is, not set) for user setting of "target frame rate". Also, FIG. 12B shows an example of an icon R2 for the user to set the "target frame rate". Note that the user can set the "target frame rate" to a desired value by pressing the "+" sign or "-" sign on the icon R2 in FIG. 12B.

For example, as shown in FIG. 11, the ensemble number determination unit 734 updates the number of ensembles when the user changes the transmission/reception conditions of ultrasound for B-mode scanning or C-mode scanning. At this time, the ensemble number determination unit 734 selects one B-mode scan among the number of ensembles that can be set and changed according to the device specifications so that, for example, the target frame rate before changing the ultrasonic transmission/reception conditions is maintained. The estimated frame rate of the color Doppler image determined by the sum of the first transmission/reception time required to perform the and the second transmission/reception time required to perform one C-mode scan is the ensemble closest to the target frame rate Adjust to numbers. However, the determination method can be changed in various ways. For example, the number of ensembles may be adjusted under the condition that the frame rate of color Doppler images is higher than the target frame rate.

In this way, by the processing of the ensemble number determining unit 734, the number of ensembles acquired in one C-mode scan is automatically determined based on the ultrasonic wave transmission/reception conditions in the B-mode scan and C-mode scan specified by the user. Finally, the number of ensembles suitable for achieving the target frame rate is determined.

However, reducing the number of ensembles acquired in one C-mode scan causes deterioration in the filter performance of the MTI filter 73, resulting in image quality deterioration of the blood flow image.

FIG. 13 is a diagram showing the relationship between the number of ensembles acquired in one C-mode scan and the filter performance of the MTI filter 73 (eigenvectors obtained by the MTI filter 73).

In the eigenvector type MTI filter 73, each eigenvector (that is, each order eigenvector) is a spatio-temporal vector expressed on the eigenspace obtained by the principal component analysis, and represents a characteristic frequency change in the time direction. It is a composite vector of multiple frequency components. In the MTI filter 73, the eigenvectors are calculated by executing principal component analysis on the time-series reflected wave data group obtained during C-mode scanning, as described with reference to FIG. Yes, and the number of eigenvectors that can be expressed by the MTI filter 73 is typically the number of ensembles acquired in one C-mode scan.

Therefore, as shown in FIG. 13, when the number of ensembles acquired in one C-mode scan is T, the number of eigenvectors that can be expressed by the MTI filter 73 is T. At this time, the smaller the number of eigenvectors that can be represented by the MTI filter 73, the more the clutter component (ie, the frequency band of the clutter component) and the blood flow component (ie, the frequency band of the blood flow component) are mixed in one eigenvector. state. Therefore, with such an MTI filter 73, it becomes difficult to completely separate the clutter component and the blood flow component.

From this point of view, the ensemble data combining unit 735 combines temporally continuous ensemble data obtained by multiple C-mode scans in order to secure the number of ensembles necessary for realizing a predetermined filter performance in the MTI filter 73. are combined in the time direction to generate a time-series reflected wave data group in which the number of ensembles is increased. In other words, the ensemble data combining unit 735 combines temporally continuous ensemble data obtained by a plurality of C-mode scans with B-mode scans interposed therebetween, thereby increasing the number of ensembles in a time-series reflected wave data group. (see FIG. 10).

Specifically, the ensemble data combining unit 735 sequentially transfers the ensemble data (ensemble data group Sp1 shown in FIG. 7) of each observation point within the region of interest set in the ROI setting unit 6 from the corner turn control unit 72. get. The ensemble data combining unit 735 is configured to temporarily hold the ensemble data group Sp1 for several times (that is, for several times of C mode scanning) acquired from the corner turn control unit 72, and the data combining number determined by itself. is combined with the ensemble data group Sp1 obtained at the current time. The ensemble data combining unit 735 sends the ensemble data group Sp1 with the increased number of ensembles in this manner to the principal component analysis execution unit 731 and the filtering processing unit 733 . Each time the ensemble data combining unit 735 acquires a new ensemble data group Sp1 from the corner turn control unit 72, the ensemble data combining unit 735 executes such data combining processing.

Thus, by increasing the number of ensembles of the time-series reflected wave data group, the number of eigenvectors that can be represented by the MTI filter 73 also increases. In the examples of FIGS. 9 and 10, by combining the ensemble data of three C-mode scans, the number of eigenvectors that can be represented by the MTI filter 73 is determined by the number of ensembles acquired in one C-mode scan of "5". can be expanded to "15".

Here, the ensemble data combination unit 735 determines the number of ensembles acquired by the C-mode scanning determined by the ensemble number determination unit 734, and the preset MTI filter 73 necessary for realizing a predetermined filter performance. Based on the number of ensembles, the number of ensemble data connections is determined.

At this time, the ensemble data combining unit 735, for example, combines temporally continuous ensemble data obtained by a plurality of C-mode scans so that the total number of ensembles is determined by the preset MTI filter 73. The number of ensemble data connections is determined so that the number of ensemble data is greater than or equal to the number of ensembles required to achieve the filter performance of . However, if the number of combinations of ensemble data is excessively large, it becomes difficult to accurately extract the blood flow component due to the influence of the movement of blood flow that changes from moment to moment. The necessary minimum number of ensembles to be summed by combining temporally continuous ensemble data obtained by C-mode scanning is close to the number of ensembles necessary for realizing a predetermined filter performance in the MTI filter 73. is preferable.

The examples of FIGS. 9 and 10 show a mode in which the number of ensembles necessary for realizing a predetermined filter performance in the MTI filter 73 is set to "15" in advance. Since the unit 734 has determined the number of ensembles to be acquired in one C-mode scan to be “5” from the relationship with the target frame rate, the ensemble data combining unit 735 sets the number of ensemble data to be combined for the C-mode scan to “3 times. ” has been decided.

It is preferable that the number of ensembles necessary for realizing a predetermined filter performance in the MTI filter 73 is, for example, 8 or more. However, the user may arbitrarily set the number of ensembles necessary for realizing a predetermined filter performance in the MTI filter 73 .

In the MTI filter 73 according to the present embodiment, the principal component analysis execution unit 731, the filter coefficient calculation unit 732, and the filtering processing unit 733 described above combine time-series reflected waves combined by the ensemble data combining unit 735. Each arithmetic processing is performed using the data group. This makes it possible to generate high-quality color Doppler images in real time without lowering the frame rate when the user changes the ultrasound transmission/reception conditions when generating color Doppler images. becomes.

Returning to FIG. 3, processing of the C-mode image generation unit 7 (correlation calculation unit 74, data conversion unit 75, noise removal spatial filter 76, inter-frame filter 77, C-mode image conversion unit 78) subsequent to the processing of the MTI filter 73 will be explained.

Under the control of the control unit 9, the correlation calculation unit 74 calculates the average value S ( A real part D and an imaginary part N of the phase difference vector mean value) are calculated.

Under the control of the control unit 9, the data conversion unit 75 converts the Doppler signals I and Q filtered by the MTI filter 73, the real part D and the imaginary part N of the average value S of the autocorrelation calculation of the Doppler signal into the blood flow velocity. Calculate V, power P, and variance T. More specifically, the data converter 75 calculates the blood flow velocity V from the real part D and the imaginary part N of the average value S of the autocorrelation calculation of the Doppler signal by the following equation (6).

The data converter 75 also calculates the power P as the average value of the intensity of the Doppler signals from the Doppler signals I and Q (complex Doppler signal z) according to the following equation (7).

Further, the data conversion unit 75 calculates the ratio of the magnitude of the phase difference vector to the power (however, from 1 to The variance T is calculated by subtracting and reversing the magnitude).

The noise removal spatial filter 76 filters the power P, the blood flow velocity V, and the variance T calculated by the data conversion unit 75 . The noise elimination spatial filter 76 has, for example, a keyhole filter and a spatial filter (both not shown).

The keyhole filter removes noise by filtering the power P, blood flow velocity V, and variance T that form the frame of the C-mode image. In the V mode and the VT mode, the keyhole filter removes the blood flow velocity V in the area to be removed set by the blood flow velocity V calculated by the data conversion unit 75 and the power P, and obtains the blood flow velocity V to filter. In the V mode and VT mode, the blood flow velocity V is used for image display (coloring). In the P mode, the keyhole filter filters the power P by removing the power P of the area to be removed set by the blood flow velocity V and the power P calculated by the data conversion unit 75 . In P mode, power P is used for image display (coloring).

More specifically, in the V mode and the VT mode, the keyhole filter regards the blood flow signal in the region where the blood flow velocity V is smaller than a predetermined threshold as clutter noise, and the blood flow signal in the region where the power P is smaller than the predetermined threshold. Considering the blood flow signal as background noise, the blood flow velocity V in these regions is removed. In the P mode, the keyhole filter regards the blood flow signal in a region where the blood flow velocity V is less than a predetermined threshold as clutter noise, and regards the blood flow signal in a region where the power P is less than a predetermined threshold as background noise. to remove the power P in these regions.

The spatial filter is a two-dimensional weighted average filter for smoothing the data of blood flow velocity V, power P, and variance T that constitute the C-mode image frame. In the V mode or VT mode, the spatial filter filters the blood flow velocity V filtered by the keyhole filter and the variance T calculated by the data converter 75 . In P mode, the spatial filter filters the power P filtered by the keyhole filter.

The inter-frame filter 77 selects a C-mode image from among the blood flow velocity V, power P, and variance T filtered by the noise removal spatial filter 76, corresponding to the display mode input by the operation unit 2. The blood flow component of each frame is filtered so as to smooth the change between frames and leave an afterimage.

The C-mode image conversion unit 78 performs color mapping on the blood flow velocity V, power P, and variance T filtered by the inter-frame filter 77, and converts and generates C-mode image data.

Returning to FIG. 2, the display processing unit 8 constructs display image data to be displayed on the display unit 11 and performs processing for causing the display unit 11 to display the display image data. In particular, when the B mode is selected, processing is performed to include the B mode image of the B mode image data generated by the B mode image generation unit 5 in the display image data as the ultrasonic image. When the C mode is selected, the C mode image generated by the C mode image generation unit 7 is placed at the position of the ROI selected on the B mode image generated by the B mode image generation unit 5 as an ultrasound image. Synthetic image data is generated by superimposing the C-mode image of the image data, and processing for including this in the display image data is performed.

The control unit 9 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). , and controls the operation of each part of the ultrasonic diagnostic apparatus 1 according to the developed program. The RAM forms a work area that temporarily stores various programs executed by the CPU and data related to these programs. The ROM is composed of a nonvolatile memory such as a semiconductor, and stores a system program for the ultrasonic diagnostic apparatus 1, various processing programs executable on the system program, various data, and the like. These programs are stored in the form of computer-readable program codes, and the CPU sequentially executes operations according to the program codes.

The storage unit 10 includes, for example, a large-capacity recording medium such as a HDD (Hard Disk Drive), and includes ultrasound image data (B-mode image data, C-mode image data, composite image data), gain matrix, frame rate, and so on. etc. to remember.

The display unit 11 is a so-called monitor such as an LCD (Liquid Crystal Display) or an EL (Electro Luminescence) display that displays image data output from the display processing unit 8 .

A part or all of the functions of each functional block of each unit included in the ultrasonic diagnostic apparatus 1 can be realized as a hardware circuit such as an integrated circuit. An integrated circuit is, for example, an LSI (Large Scale Integration), and LSIs are also called ICs (Integrated Circuits), system LSIs, super LSIs, and ultra LSIs depending on the degree of integration. In addition, the method of circuit integration is not limited to LSI, and it may be realized with a dedicated circuit or a general-purpose processor, and it is possible to reconfigure the connection and setting of circuit cells inside FPGA (Field Programmable Gate Array) and LSI. A reconfigurable processor may be used. Also, a part or all of the functions of each functional block may be executed by software. In this case, this software is stored in one or more storage media such as ROMs, optical discs, hard disks, etc., and this software is executed by the arithmetic processor.

[Updating processing of ultrasonic transmission/reception conditions in ultrasonic diagnostic apparatus]
FIG. 14 is a flowchart showing processing for updating the transmission/reception conditions of ultrasonic waves in the ultrasonic diagnostic apparatus 1 . The operation flow shown in FIG. 14 is processing executed by the ensemble number determining unit 734 and the ensemble data combining unit 735 when a user inputs a command to change the transmission/reception conditions of ultrasonic waves.

In step Sa1, the ensemble number determining unit 734 first determines whether or not a command to change the transmission/reception conditions of ultrasonic waves for B-mode scanning or C-mode scanning has been input from the user. At this time, if the user inputs a command to change the transmission/reception conditions of ultrasonic waves (step Sa1: YES), the ensemble number determination unit 734 advances the process to step Sa2. On the other hand, if the user has not input an instruction to change the transmission/reception conditions of ultrasonic waves (step Sa1: NO), the process of the series of flowcharts in FIG. 14 is terminated without executing any particular process.

In step Sa2, the ensemble number determination unit 734 calculates the transmission/reception time required for one B-mode scan.

In step Sa3, the ensemble number determination unit 734 calculates the transmission/reception time required for one C-mode scan.

In step Sa4, the ensemble number determining unit 734 sums the transmission/reception time required for one B-mode scan calculated in step Sa2 and the transmission/reception time required for one C-mode scan calculated in step Sa3, Based on the total time, the frame rate of the color Doppler image is calculated.

In step Sa5, the ensemble number determination unit 734 compares the frame rate of the color Doppler images calculated in step Sa4 with the target frame rate, and compares the frame rate of the color Doppler images calculated in step Sa4 with the target frame rate. is equal to or less than a first threshold value (the first threshold value is a threshold value for determining whether the frame rate difference value is sufficiently small) or less. At this time, if the difference between the frame rate of the color Doppler image calculated in step Sa4 and the target frame rate is equal to or less than the first threshold (step Sa5: YES), the ensemble number determining unit 734 determines the number of ensembles in C-mode scanning. is set to the currently set value, and the process proceeds to step Sa7. On the other hand, if the difference between the frame rate of the color Doppler image calculated in step Sa4 and the target frame rate is greater than the first threshold (step Sa5: NO), step Sa6 is performed to change the number of ensembles in C-mode scanning. proceed to

In step Sa6, the ensemble number determination unit 734 decrements the number of ensembles in the C-mode scanning by one from the current set value, returns to step Sa3, and repeats one C-mode scanning under the transmission/reception conditions. Calculate the required transmit and receive time.

In step Sa7, the ensemble data combining unit 735 determines that the number of ensembles in the C-mode scanning determined in step Sa5 is a second threshold value (the second threshold value is set to Required number of ensembles) or less. At this time, if the number of ensembles in the C-mode scanning determined in step Sa5 is equal to or less than the second threshold (step Sa7: YES), the ensemble data combining unit 735 advances the process to step Sa8. On the other hand, if the number of ensembles in C-mode scanning determined in step Sa5 is greater than the second threshold (step Sa7: NO), the process proceeds to step Sa9.

In step Sa8, the ensemble data combining unit 735 calculates the necessary number of ensemble data to be combined in order to combine the ensemble data obtained by the multiple C-mode scans. At this time, the ensemble data combining unit 735, for example, combines the number of ensembles (for example, 15) necessary for realizing a predetermined filter performance with the preset MTI filter 73 into the C mode determined in step Sa5. Divide by the number of ensembles in scanning (eg, 5) to calculate the number of combinations of ensemble data.

In step Sa9, the ensemble number determination unit 734 and the ensemble data combination unit 735 transmit the information related to the determined ultrasonic wave transmission/reception conditions (that is, the ensemble number in C-mode scanning) to the control unit 9, and the transmission unit 3 , to change the number of ensembles when performing C-mode scanning.

In the ultrasonic diagnostic apparatus 1 according to the present embodiment, through such a series of processes, the ultrasonic transmission/reception conditions for B-mode scanning and the ultrasonic transmission/reception conditions for C-mode scanning specified by the user are reflected. In this case, it is possible to provide high-quality color Doppler images in which clutter components are highly suppressed while maintaining the target frame rate.

FIG. 15 is obtained when filtering in the MTI filter 73 is performed using ensemble data (here, ensemble data obtained by three C-mode scans) combined by the ensemble data combiner 735. The blood flow image (lower diagram) and the ensemble data obtained by one C-mode scan without data combination by the ensemble data combination unit 735 are used to perform the filtering process in the MTI filter 73 . FIG. 10 is a diagram showing a comparison with a flow image (upper diagram).

The upper diagram of FIG. 15 (data not combined by the ensemble data combining unit 735) and the lower diagram (data combined by the ensemble data combining unit 735) show the same ultrasound image subjected to filtering by the MTI filter 73. It is a blood flow image obtained after. Here, blood flow images obtained under the same conditions as in FIGS. 9 and 10 are shown, and the number of ensembles in one C-mode scan is 5, and the number of data couplings in the ensemble data coupling unit 735 is 3. The conditions are as shown below.

The image with "2/5", the image with "3/5", and the image with "4/5" in the upper diagram of FIG. , the blood flow image when set to "3", and the blood flow image when set to "4". In the upper diagram of FIG. 15, the ensemble data obtained by one C-mode scan is used to perform filtering in the MTI filter 73, so there are only five eigenvectors.

Image with "7/15", image with "9/15", image with "11/15", image with "12/15", image with "13/15" in the lower diagram of FIG. and "14/15" are the blood flow image when the rank cut order is set to "7", the blood flow image when the order is set to "9", and the blood flow image when "11". , a blood flow image when set to "12", a blood flow image when set to "13", and a blood flow image when set to "14". In the lower diagram of FIG. 15, the combined data of the ensemble data obtained by three C-mode scans is used to perform filtering in the MTI filter 73, so there are 15 eigenvectors.

Comparing the lower diagram of FIG. 15 (data merging performed by the ensemble data merging unit 735) and the upper diagram of FIG. In comparison, the blood flow component and the clutter component can be separated more appropriately, and as the rank cut order increases, the clutter component is selectively suppressed in the image, leaving only the blood flow component. It is understood that In other words, in the upper diagram of FIG. 15, only five eigenvectors express the blood flow component and the clutter component in the blood flow image, so the blood flow component and the clutter component cannot be clearly separated. However, even if the rank-cut order increases, both the blood flow component and the clutter component remain.

Also, in the lower diagram of FIG. 15, as a result of the increase in the number of samples in the time direction compared to the upper diagram of FIG. 15, the effect of noise smoothing in the image can also be seen. That is, in the blood flow image obtained by the ultrasonic diagnostic apparatus 1, there is flickering caused by, for example, thermal noise of an electronic circuit, and acoustic noise caused by scattering, multiple reflection, or reverberation in the subject. As included, performing data combining by ensemble data combining unit 735 can reduce this type of flicker.

FIG. 16 is a diagram illustrating general filter characteristics of an eigenvector-type MTI filter. FIG. 16A represents the entire measurement signal (for example, pixel values of a blood flow image) that change from moment to moment, FIG. 16B represents a continuous signal extracted from the measurement signal of FIG. 16A, and FIG. Represents the discontinuous signal extracted from the measured signal.

As described above, the MTI filter 73 according to the present embodiment combines temporally continuous ensemble data obtained by a plurality of C-mode scans in the time direction to increase the number of ensembles. is used to filter. Since the time-series reflected wave data group is combined data of the ensemble data of each C-mode scanning obtained when the B-mode scanning and the C-mode scanning are alternately performed, the time-series reflected wave data group , a temporally discontinuous portion is generated in the coupling portion (see region R3 in FIG. 16C).

MTI filters, such as HPF, commonly used in the prior art decompose the measurement signal into its respective frequency components and remove clutter. When the measurement signal is a continuous signal (FIG. 16B), such an MTI filter functions normally in frequency resolution and can accurately remove clutter. However, when the measurement signal is a discontinuous signal obtained by combining a plurality of continuous signals (FIG. 16C), the MTI filter expresses the discontinuous combined portion by decomposing it into each frequency component. noise is mixed in each frequency component expressing , and a lot of noise is also mixed in the blood flow signal after clutter removal.

On the other hand, unlike frequency filters, eigenvector-type MTI filters generally use eigenvectors (multiple frequency components representing characteristic frequency changes in the time direction) expressed in the eigenspace obtained by principal component analysis. composite vector). Therefore, in the eigenvector-type MTI filter, even when the measurement signal is a discontinuous signal obtained by combining a plurality of continuous signals (FIG. 16C), the measurement signal is added to the blood flow component, the clutter component, and the discontinuous signal. It is possible to extract the component corresponding to the signal change of the binding portion. As a result, the eigenvector-type MTI filter can prevent the filtered blood flow signal from including noise caused by the discontinuous portion.

In the MTI filter 73 according to the present embodiment, an eigenvector type MTI filter is applied based on such filter characteristics. In other words, the MTI filter 73 according to the present embodiment can generate a high-quality blood flow image that does not contain noise components despite the presence of discontinuous portions in the combined portions of the ensemble data of each C-mode scan. It becomes possible.

As described above, according to the ultrasonic diagnostic apparatus 1 according to the present embodiment, even when the user changes the transmission/reception conditions of ultrasonic waves when generating a color Doppler image, the frame rate can be reduced. It is possible to generate a high-quality color Doppler image in real time with highly suppressed clutter components.

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

According to the ultrasonic diagnostic apparatus according to the present disclosure, even when the user changes the transmission/reception conditions of ultrasonic waves when generating a color Doppler image, high image quality can be obtained without causing a decrease in the frame rate. It is possible to generate color Doppler images.

1 Ultrasound diagnostic device 2 Operation unit 3 Transmission unit 4 Reception unit 5 B-mode image generation unit 6 ROI setting unit 7 C-mode image generation unit 8 Display processing unit 9 Control unit 10 Storage unit 71 Quadrature detection circuit 72 Corner turn control unit 73 MTI filter 731 principal component analysis execution unit 732 filter coefficient calculation unit 733 filtering processing unit 734 ensemble number determination unit 735 ensemble data combination unit 74 correlation calculation unit 75 data conversion unit 76 noise removal spatial filter 77 inter-frame filter 78 C-mode image conversion unit 100 Ultrasound diagnostic apparatus body 101 Ultrasound probe 101a Transducer

Claims (9)

A color Doppler image obtained by alternately performing a first ultrasonic scan in B mode and a second ultrasonic scan in C mode with respect to the ultrasonic probe and superimposing a blood flow image on the B mode image is obtained. An ultrasound diagnostic apparatus that generates
The C-mode image generating unit that generates the blood flow image,
Based on the ultrasonic transmission and reception conditions in the first ultrasonic scan and the second ultrasonic scan specified by the user, the number of ensembles to be acquired in one second ultrasonic scan to achieve the target frame rate an ensemble number determination unit that determines the number of ensembles suitable for
an ensemble data combining unit that combines temporally continuous ensemble data obtained by a plurality of the second ultrasound scans in the time direction to generate a time-series reflected wave data group in which the number of ensembles is increased;
an MTI filter generator that performs principal component analysis on the time-series reflected wave data group and calculates filter coefficients of the MTI filter based on a plurality of eigenvectors obtained by the principal component analysis;
an MTI filter processing unit that applies the MTI filter to the time-series reflected wave data group to extract a blood flow signal for generating the blood flow image;
Ultrasound diagnostic device comprising. The ensemble data combining unit uses the number of ensembles acquired in one second ultrasound scan determined by the number of ensemble determination unit as a reference, and the MTI filter is required to achieve a predetermined filter performance. Determining the number of connections of the ensemble data that are continuous in time to ensure the number of ensembles,
The ultrasonic diagnostic apparatus according to claim 1. The ensemble number determining unit, based on the transmission and reception conditions of the ultrasonic waves in the first ultrasonic scan and the second ultrasonic scan, a first transmission and reception time required to perform one of the first ultrasonic scans and , estimating the frame rate of the color Doppler image from the total time of the second transmission and reception time required to perform one of the second ultrasound scans,
Determining the number of ensembles to be acquired in one second ultrasound scan so that the frame rate of the color Doppler image approaches the target frame rate,
The ultrasonic diagnostic apparatus according to claim 1 or 2. When the user changes the ultrasonic wave transmission/reception conditions in the first ultrasonic scan or the ultrasonic wave transmission/reception conditions in the second ultrasonic scan, the ensemble number determination unit determines the target frame rate before the change Update the number of ensembles acquired in one second ultrasound scan so that is maintained,
The ultrasonic diagnostic apparatus according to any one of claims 1 to 3. The ultrasound transmission/reception conditions in the first ultrasound scan referred to by the ensemble number determination unit include transmission/reception linear density and transmission/reception depth in the first ultrasound scan,
The ultrasonic diagnostic apparatus according to any one of claims 1 to 4. The ultrasound transmission/reception conditions in the second ultrasound scan referred to by the ensemble number determination unit include transmission/reception line density, transmission/reception depth, size of the region of interest, and flow velocity range of the observation target in the second ultrasound scan.
The ultrasonic diagnostic apparatus according to any one of claims 1 to 5. Having a setting unit that receives designation of the target frame rate by the user;
The ultrasonic diagnostic apparatus according to any one of claims 1 to 6. A color Doppler image obtained by alternately performing a first ultrasonic scan in B mode and a second ultrasonic scan in C mode with respect to the ultrasonic probe and superimposing a blood flow image on the B mode image is obtained. A control method for an ultrasonic diagnostic apparatus that generates
When generating the blood flow image, based on the ultrasonic transmission and reception conditions in the first ultrasonic scan and the second ultrasonic scan specified by the user, the ensemble acquired in one second ultrasonic scan A first process of determining the number of ensembles suitable for achieving the target frame rate;
A second process of generating a time-series reflected wave data group in which the number of ensembles is increased by combining temporally continuous ensemble data obtained by a plurality of the second ultrasonic scans in the time direction;
a third process of performing principal component analysis on the time-series reflected wave data group and calculating filter coefficients of an MTI filter based on a plurality of eigenvectors obtained by the principal component analysis;
a fourth process of applying the MTI filter to the time-series reflected wave data group to extract a blood flow signal for generating the blood flow image;
A control method for an ultrasonic diagnostic apparatus that performs A color Doppler image obtained by alternately performing a first ultrasonic scan in B mode and a second ultrasonic scan in C mode with respect to the ultrasonic probe and superimposing a blood flow image on the B mode image is obtained. A control program for an ultrasonic diagnostic apparatus that generates
When generating the blood flow image,
Based on the ultrasonic transmission and reception conditions in the first ultrasonic scan and the second ultrasonic scan specified by the user, the number of ensembles to be acquired in one second ultrasonic scan to achieve the target frame rate A first process of determining the number of ensembles suitable for
A second process of generating a time-series reflected wave data group in which the number of ensembles is increased by combining temporally continuous ensemble data obtained by a plurality of the second ultrasonic scans in the time direction;
a third process of performing principal component analysis on the time-series reflected wave data group and calculating filter coefficients of an MTI filter based on a plurality of eigenvectors obtained by the principal component analysis;
a fourth process of applying the MTI filter to the time-series reflected wave data group to extract a blood flow signal for generating the blood flow image;
A control program for an ultrasonic diagnostic apparatus that executes

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