JPH08131436A - Ultrasonic diagnostic system - Google Patents

Abstract

PURPOSE: To automatically set a region of interest(ROI) suitable for the area of an atrium, etc., in an ultrasonic diagnostic system. CONSTITUTION: The contour point detecting part 42 of an automatic ROI setting part 40 detects the contour point of a bloodstream area along each ultrasonic beam of sector scan. A centroid coordinate arithmetic part 44 finds the centroid of contour point groups from the coordinates of detected contour points. A moment of inertia arithmetic part 46 performs the coordinate transformation of the coordinate of each contour point to a centroid coordinate system setting the centroid as an origin, and finds the moment of inertia and products of inertia of the contour point group around each coordinate axis. An inertia main spindle arithmetic part 48 finds the inclination of an inertia main spindle for the centroid coordinate system based on the moment of inertia and the products of inertia. A ROI arithmetic part 50 finds the inertia main spindle based on the inclination, and decides the length of the major axis and minor axis of an elliptical ROI from the coordinate of the contour point in the neighborhood of the inertia main spindle, and sets the ROI so as to align the major axis and the minor axis with each inertia main spindle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to an ultrasonic diagnostic apparatus having a function of detecting movements of the heart, blood vessel wall and the like.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus is widely used for diagnosing a heart or a blood vessel such as a B-mode tomographic image or a blood flow image by Doppler.

In recent years, as one of the diagnostic methods of the heart and the like using such ultrasonic waves, changes in the cross-sectional area of the heart and blood vessels are detected from ultrasonic images, and the abnormalities of the heart and the like are detected from the state of these changes. A method of diagnosing has been devised. As an apparatus using such a method, for example, Japanese Patent Laid-Open No. 4-28
There is a device shown in 2144. This device automatically traces the endomyocardium (that is, the boundary between the blood flow and the myocardium) and changes the area of the traced closed region (that is, the heart chamber) with time or the time derivative of the area of this closed region. Display the waveform. This function is expected to be applied to diagnosis of myocardial infarction and diagnosis of heart pump functions such as diastole and contraction.

This conventional apparatus has a region of interest (hereinafter referred to as ROI) in the ultrasonic image region in order to ensure the accuracy of the area measurement of the closed region obtained by automatic tracing.
An area called "gionOf Interest" is provided, and this R
The area was calculated only inside the OI. That is, when the area between the blood flow and the myocardium is automatically traced to calculate the area, if the boundary is not properly detected, a part of the boundary may be missing. In ultrasound images, boundary detection does not always work well in all frames, and in frames where boundary detection does not work well, the area calculation result becomes a very large value that is far from the true value (extremely large value). In such a case, the area including the end portion of the screen of the ultrasonic image is included in the area, resulting in a very large value. Therefore, in the conventional device, R is surrounded by surrounding the target area.
By setting the OI and limiting the area calculation range to the inside of the ROI (that is, the part outside the ROI is not calculated), the calculation result that is far from the true value even in the frame in which the boundary detection is not successful I was trying not to come out.

[0005]

The ROI used for such a purpose is less effective if the shape and area are too far from the closed region such as the heart chamber whose area is to be measured.
Therefore, in the above-mentioned conventional device, the user manually sets an appropriate ROI with a trackball or the like. However, the manual setting complicates the operation of area measurement, and there is a problem that the inspection takes time. Further, not limited to the above-mentioned conventional device, there has been no device capable of automatically setting the ROI suitable for the area to be the area measurement target.

The present invention has been made to solve such a problem, and is suitable for a measurement target region when measuring an area change of a region of a fluid such as a blood flow in a subject. An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of automatically setting a ROI.

[0007]

In order to achieve the above-mentioned object, an ultrasonic diagnostic apparatus according to the present invention comprises a contour detecting means for detecting a contour of a subject tissue in an ultrasonic image region from an ultrasonic echo signal. An inertial principal axis calculation means for obtaining an inertial principal axis of the contour, and a region of interest that automatically includes the contour inside and has a predetermined positional relationship with the principal axis of inertia within the ultrasonic image region. And means.

The contour detecting means detects a contour point of the subject tissue for each ultrasonic beam in the ultrasonic beam scanning, and the inertial principal axis calculating means detects the contour point of the contour point detected by the contour detecting means. The feature is that the principal axis of inertia is obtained based on the coordinates.

[0009]

The present invention has the above-described structure. First, the contour detecting means determines the contour of the subject tissue in the ultrasonic image of the designated frame (for example, the boundary between the blood flow and the subject tissue). Line) is detected.

Next, the inertial principal axis calculating means finds the principal axis of inertia of the figure indicated by this contour. Here, the principal axis of inertia is the same as that generally used in mechanics, among the orthogonal axes whose origin is the center of gravity of the contour figure, so that the moments of inertia of the contour figure around each axis are respectively the maximum and the minimum. It can be said that this is an axis that indicates the directionality of the contour figure.

The apparatus of the present invention determines the directionality of the contour figure by thus determining the principal axis of inertia of the contour of the subject tissue. Then, by setting the ROI having a predetermined shape according to its directionality, it is possible to automatically set the ROI with less waste. That is, the region-of-interest automatic setting means associates the ROI having a predetermined shape with the obtained principal axis of inertia in the ultrasonic image region so as to have a predetermined positional relationship and to include a contour figure inside. Set automatically. The method of associating the ROI with the principal axis of inertia is RO
Various methods can be adopted depending on the shape of I. For example, when a symmetrical ROI such as an ellipse is adopted, the ROI
The ROI may be set so that the axis of symmetry of the contour coincides with the principal axis of inertia of the contour. As the shape of the ROI, the user presets a desired shape.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ultrasonic diagnostic apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of the ultrasonic diagnostic apparatus according to the present invention, and FIG. 2 is a diagram showing the configuration of the automatic ROI setting unit 40 of FIG.

In FIG. 1, the scanning control unit 70 controls transmission / reception of ultrasonic waves in the probe 10 via the transmission / reception unit 20 according to the timing signal from the timing signal generation unit 72. The quadrature detection unit 28 performs quadrature detection on the ultrasonic echo signal input via the transmission / reception unit 20 in order to obtain the Doppler signal. At this time, the quadrature detection unit 28 performs quadrature detection by multiplying the ultrasonic echo signal by the reference signals output from the timing signal generation unit 72 and having a phase difference of 90 degrees. The quadrature detection unit 28 outputs a Doppler signal composed of two signals, a real number part and an imaginary number part.

The Doppler signal output from the quadrature detector 28 is digitized by the A / D converter 30 and then input to the clutter removal filter 32.

The clutter removing filter 32 is a high-pass filter (high-pass filter) for extracting only a high speed (high frequency band) Doppler signal from the input digitized Doppler signal. For example, if the subject is a heart, it is the blood that fills the heart chamber that generates the Doppler signal in the high frequency band, so the clutter removal filter 32 causes a low velocity (low frequency band) due to the motion of the myocardium. The Doppler signal is removed and the signal of the blood flow region in the heart chamber is extracted.

The clutter removing filter 32 is connected to an autocorrelation unit 34 which performs a known correlation calculation process on the extracted Doppler signal in the high frequency band to obtain an autocorrelation.

The autocorrelation unit 34 has a velocity calculation unit 36 for obtaining the motion velocity of the subject from the correlation signal obtained by the autocorrelation unit 34, and similarly for obtaining the dispersion (velocity distribution state) of the Doppler signal from the correlation signal. The distributed computing unit 38 of is connected. The velocity signal V output from the velocity calculation unit 36 and the dispersion signal σ ² output from the dispersion calculation unit 38 are the DSC.
(Digital scan converter) 60. D
The SC 60 determines color and brightness according to the velocity signal V and the dispersion signal σ ² , converts the scanning format, and generates image data. The image data output from the DSC 60 is converted into an analog signal by the D / A converter 62 and displayed on the display unit 64.

The amplification unit 22, the detection unit 24, and the A / D converter 26 display a predetermined tomographic image of the subject in black and white (B
This is a configuration for performing mode display), and by using these, a predetermined tomographic image can be displayed on the display unit 64 as necessary, like the motion velocity signal and the dispersion signal.

In addition to the above configuration, as a characteristic configuration of this embodiment, the output side of the speed calculation unit 36 is
An automatic ROI setting unit 40 that performs processing such as automatic setting of OI is provided.

The automatic ROI setting unit 40 has a structure as shown in FIG. 2 and has an R value suitable for the blood flow region to be the object of area measurement.
The OI is calculated and output to the DSC 60.
Hereinafter, the internal configuration and operation of the automatic ROI setting unit 40 will be described in detail.

In the automatic ROI setting section 40, the contour point detecting section 42 first detects the contour of the blood flow region (that is, the blood flow region and the myocardium surrounding the blood flow region) which is the target of ROI setting based on the velocity signal V. (Tissue boundary) is detected. In the present embodiment, the contour is obtained by subjecting the velocity signal V obtained by the velocity calculator 36 to threshold processing. Since the velocity of the subject tissue such as myocardium is considerably lower than the velocity of the blood flow region, the boundary between the subject tissue and the blood flow region can be detected by examining the change in the velocity signal. More specifically, in this embodiment, as shown in FIG.
For each ultrasonic beam that is sector-scanned from, the velocity signal data is viewed in the direction along the ultrasonic beam, and the edge of the velocity change is determined by the contour point (that is, the boundary between the blood flow region 110 and the subject tissue 120). Point) P ₁ , ... P _i , P _{i + 1} ...
It is detected as P _N (N is the total number of obtained contour points), and its coordinates P _i (x _i , y _i ) are obtained. Blood region contour 1
15 is represented by the contour points thus obtained. For example, if the number of ultrasonic beams in scanning for one frame is 64, the coordinates of about 100 contour points can be obtained.

Hereinafter, based on the coordinate data P _i (x _i , y _i ) of the contour points obtained in this way, the barycentric coordinate calculation unit 44, the moment of inertia calculation unit 46, and the inertial spindle calculation unit 4
By the function of 8, the principal axes of inertia of these contour points are obtained.

First, the barycentric coordinate calculation unit 44 uses the following equation (1).
Then, the coordinates (x _g , y _g ) of the center of gravity G of the contour point are obtained.

[0025]

[Equation 1] Next, the inertia moment calculation unit 46 calculates the coordinates P _{i of} each contour point obtained by the contour point detection unit 42 according to the following equation (2).
The coordinates of (x _i , y _i ) are converted into a coordinate system having the center of gravity G (x _g , y _g ) as the origin (called a center of gravity coordinate system).

[0026]

## EQU2 ## X _i = x _i -x _g , Y _i = y _i -y _g (2) The center of gravity coordinate system is a coordinate system parallel to the coordinate system before the coordinate conversion.

When the coordinate conversion is completed in this way, the inertia moment calculation unit 46 further uses the coordinates of each contour point in the barycentric coordinate system to rotate around each axis of the barycentric coordinate system (that is, around the X axis and the Y axis). ) Moment of inertia M _X and M _Y
And the product of inertia M _XY are obtained according to the following equations (3), (4) and (5).

[0028]

(Equation 3)

[Equation 4]

(Equation 5) Then, the inertial principal axis calculation unit 48 uses M _X , M _Y, and M _XY to obtain the inclination φ of the inertial principal axis according to the following equation (6).

[0029]

(Equation 6) Based on the inclination φ of the principal axis of inertia thus obtained, the ROI calculation unit 50 obtains an ROI suitable for the contour shape by the procedure shown below. For example, in the case of targeting a heart chamber, the contour of the heart chamber in the ultrasound image is a shape close to an ellipse, although it slightly changes depending on how the tomographic plane is taken. Can be reduced. Therefore, in this embodiment, a case of setting an elliptical ROI will be described.

First, the coordinates (X _i , Y _i ) of each contour point in the barycentric coordinate system are converted into the coordinates (X _pi , Y _pi ) in the inertial spindle coordinate system rotated by the angle φ according to the following equation (7). Convert coordinates. This coordinate conversion is performed to simplify subsequent calculations.

[0031]

(Equation 7) FIG. 4 shows the inertial principal axis coordinate system (X _p
Axis, Y _p axis) and center coordinates system (X-axis, shows the relationship between the Y-axis). In the figure, the X _p axis and the Y _p axis are the principal axes of inertia of the contour.

After the coordinate conversion is performed in this manner, RO
The I calculation unit 50 searches for contour points included in the vicinity of each principal axis of inertia (X _p axis, Y _p axis) and finds the maximum absolute value of the X _p and Y _p coordinates. Specifically, as shown in FIG.
_From the coordinates of the contour points included in the angular range ± δφ from the _p- axis and the Y _p- axis, the maximum value of each coordinate is calculated based on the following equation (8). It should be noted that the value of δφ can be appropriately set by the user or the like.

[0033]

| X _pmax | = Max {| X _pi |}, | Y _pmax | = Max {| Y _pi |} (8) where Max {} is the maximum of the set of values in {}. It is an operator that asks for a value.

These | X _pmax | and | Y _pmax | are elliptical shapes R
It is used as a reference for obtaining the lengths of the major axis and the minor axis of the OI. For example, in the case of a shape close to an ellipse such as the contour of a heart chamber, the contour can be approximated to some extent by an ellipse having | X _pmax | and | Y _pmax | as major and minor axes. However, if this ellipse is used as it is as the ROI, the contour shape is biased, and therefore, some parts may be out of the ROI. Therefore, in the present embodiment, | X _pmax | and | Y _pmax
By enlarging | to a major axis and a minor axis of the elliptical ROI by a predetermined ratio, all regions such as the heart chamber are included in the ROI.

That is, the ROI calculator 50 determines the lengths of the major axis and the minor axis of the elliptical ROI according to the following equation (9).

[0036]

A = α | X _pmax |, b = α | Y _pmax | (9) In the above equation (9), α is a constant greater than 1, and a specific value is set by a user or the like as appropriate. (For example, α =
1.5).

Then, the ROI calculator 50 calculates an elliptical R based on the lengths of the major axis and the minor axis thus obtained.
Set the OI. This ROI is represented by the following expression (10) in the inertial principal axis coordinate system.

[0038]

[Equation 10] FIG. 5 shows an example of the ROI thus obtained. The calculated ROI is used for limiting the range when calculating the area as described above. The ROI is also used when the processing range is limited when interpolation processing of pixel data is performed in order to make an ultrasonic image fine, or when the calculation range is limited when various data other than the area is obtained. Is used. Therefore, such RO
In order to reduce the amount of processing by a computer or the like, it is desirable that I includes the target blood flow region and has the smallest possible area. In the present embodiment, as described above, an area having an oval shape close to the shape of the heart chamber, which has a directivity that matches the direction of the principal axis of inertia, is calculated, and this area is adopted as the ROI. This makes it possible to automatically obtain the ROI that has less waste in area.

The signal indicating the ROI thus obtained is input to the display unit 64 via the multiplexer 56, the DSC 60, etc., and is superimposed and displayed on the ultrasonic image.

Further, in this embodiment, the area of the contour figure (that is, the area of the blood flow region) is calculated as follows using the ROI thus obtained.

At this point in time, the contour points that define the contour of the blood flow region are only obtained for each ultrasonic beam, so that the data is rough as it is and a highly accurate value can be obtained even if the area calculation is performed. I can't. Therefore, in the present embodiment, first, the contour point interpolation calculation unit 52 interpolates the contour points by a known method. At this time, the contour point interpolation calculation unit 52 determines that the ROI
Using the ROI data provided from the calculation unit 50, the RO
Interpolation of contour points is performed only in the area inside I.

Then, the area calculator 54 obtains the area of the contour figure using the dense contour point data obtained by the interpolation. This area calculation is performed only inside the ROI.

The area signal (AREA) output from the area calculator 54 is combined with the ROI signal by the multiplexer 56 and output to the DSC 60 as a multiplexed signal. Among these, the AREA signal is used when displaying the area change of the blood flow region in a waveform display (graph display). The multiplexer 56 is controlled by a control signal and
Mode for outputting only OI signal, ROI signal and AREA
It is possible to switch to a mode in which a signal multiplexed with the signal is output.

As described above, according to the present embodiment, it is possible to obtain the ROI without waste in accordance with the shape / area of the blood flow region to be subjected to the area measurement, and automatically set the ROI. In addition, although the case where the inclination φ of the principal axis of inertia is obtained in the calculation of the above equation (6) has been described above, the inclination of the principal axis of inertia is not necessarily obtained in that way depending on the shape of the contour. When the inclination of the principal axis of inertia cannot be obtained in this way, it is necessary to perform an exceptional process different from the above-mentioned process. The exception processing will be described below.

First, when the above equation (6) is calculated, the determination processing is performed using the following equation (11).

| M _Y −M _X | <δ (δ is an extremely small predetermined value) (11) When the condition of this equation (11) is satisfied (that is, M _X
And M _Y is very small), the inclination of the principal axis of inertia cannot be obtained. Therefore, in this case, the contour shape is regarded as a circle, and a circular ROI centered on the center of gravity G is set. In this case, the size (radius) of the ROI is, for example,
The maximum absolute value of the coordinates of each contour point in the barycentric coordinate system may be obtained, and this may be obtained by multiplying it by a constant.

When examining the temporal change of the area of the heart chamber using this embodiment, the contour of the heart chamber when the heart chamber reaches the maximum area at one heartbeat (that is, diastole) is detected in the ultrasonic image. Then, the ROI may be automatically set based on this contour. In this way, the area of the heart chamber does not extend beyond its ROI during all phases. Of course, if the ultrasonic diagnostic apparatus has a sufficient computing capacity, the area may be calculated by performing automatic ROI setting for each frame.
By doing so, the accuracy of area calculation is further improved.

As described above, according to the present embodiment,
It is possible to obtain an ROI that is suitable for the shape and area of the blood flow region that is the target of the area measurement and has a small area waste, and automatically set the ROI. Further, in the above-mentioned conventional device,
If the detected boundary has a "void", a large error is caused in the calculated value of the area.However, in this embodiment, even if the detection of the outline point is partially unsuccessful, the outline point is generally detected. If so, an appropriate ROI can be obtained, and by limiting the area calculation range by the ROI, the error in area calculation can be reduced.

In this embodiment, the case where the elliptical ROI is used has been described, but the shape of the ROI is not limited to this.
The method of the present embodiment can be applied to any shape of ROI. In this case as well, the principal axis of inertia of the contour can be used as a reference for the ROI setting position.
The specific positional relationship with I depends on the shape of the ROI. For example, when using a symmetric ROI such as a rectangle, RO
The axis of symmetry of I may be matched with the principal axis of inertia.

Further, in the present embodiment, the contour detection of the blood flow region which is the target of the area measurement is performed based on the velocity data obtained by the Doppler method, but the present invention is not limited to this, and the contour detection is performed by B
It can also be performed based on the amplitude of the ultrasonic echo in the modal method. That is, there is a large difference in the amplitude of the ultrasonic echo between the liquid part such as blood flow and the tissue part such as myocardium, and the contour can be detected by discriminating this difference by threshold processing.

In the present embodiment, the case of sector scanning has been described, but the method of this embodiment can be applied to other scanning methods such as linear scanning.

Although the ROI setting mainly for the heart chamber has been described above, the method of the present embodiment is effective for the cross section of the blood vessel and other regions where the liquid flows inside. .

[0052]

As described above, according to the present invention,
ROI suitable for the target area and less wasteful in area
Can be automatically set in the ultrasonic image area. Therefore, the time required for the inspection can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is a block diagram showing an internal configuration of an automatic ROI setting unit of the ultrasonic diagnostic apparatus according to the present invention.

FIG. 3 is a conceptual diagram showing a relationship between a blood flow region and contour points.

FIG. 4 is an explanatory diagram showing a relationship between an inertial principal axis coordinate system and a barycentric coordinate system.

FIG. 5 is an explanatory diagram showing an example of an ROI that is automatically set in the embodiment.

[Explanation of symbols]

 10 probe 20 transmitting / receiving unit 22 amplifying unit 24 detecting unit 26 A / D converter 28 quadrature detecting unit 30 A / D converter 32 clutter removing filter 34 autocorrelation unit 36 velocity calculating unit 38 dispersion calculating unit 40 automatic ROI setting unit 42 contour point detection unit 44 barycentric coordinate calculation unit 46 inertia moment calculation unit 48 inertial spindle calculation unit 50 ROI calculation unit 52 contour point interpolation calculation unit 54 area calculation unit 56 multiplexer

Claims (2)

[Claims] 1. An ultrasonic diagnostic apparatus which transmits and receives an ultrasonic beam into and from a subject, generates an ultrasonic image based on the ultrasonic echo signal, and displays the ultrasonic image. Contour detection means for detecting the contour of the subject tissue, inertial principal axis calculation means for determining the principal axis of inertia of the contour, and a region of interest having a predetermined positional relationship with the principal axis of inertia which includes the contour therein, A region of interest automatic setting means for automatically setting in a sound wave image region, and an ultrasonic diagnostic apparatus. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the contour detection unit detects a contour point of a subject tissue for each ultrasonic beam in ultrasonic beam scanning, and the inertial principal axis calculation unit An ultrasonic diagnostic apparatus, characterized in that the principal axis of inertia is obtained based on the coordinates of the contour points detected by the contour detecting means.