JP2004230200A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus capable of finding only the component of velocity of expansion/contraction of a subject tissue. <P>SOLUTION: A translational velocity operation part 510 calculates the translational velocity V from the displacement of coordinates of the center of inertia of the outline of the subject tissue. An angular velocity operation part 512 calculates the rotational angular velocity ω of the subject tissue from the inclination variation of inertia of the main shaft of the outline of the subject tissue. A rotational speed operation part 514 finds the component of velocity rω of the rotational motion of each point of the subject tissue using the angular velocity ω. A tangential velocity operation part 518 finds the component of velocity vϕ in the tangential direction of each point using the translational velocity V and the component of velocity rω of the rotational motion of each point. A two-dimensional velocity vector operation part 520 finds the two-dimensional velocity vector v of each point from the component of velocity vϕ in the tangential direction and the component of velocity v<SB>k</SB>in the direction of ultrasonic beams of each point. An expansion/contraction velocity operation part 522 calculates the component of velocity v<SB>r</SB>of the expansion/contraction motion of each point based on the two-dimensional velocity vector v and the translational velocity V. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an ultrasonic diagnostic apparatus that detects and displays a movement speed of a subject tissue.

  The ultrasonic Doppler method, which determines the velocity of the blood flow based on the Doppler shift frequency of the ultrasonic echo and displays the distribution in color, has been widely used.In recent years, this ultrasonic Doppler method has been applied to the movement of the tissue of a subject such as a myocardium. Research for use in speed detection is ongoing. In this way, the technique of obtaining the motion velocity of the subject tissue by the ultrasonic Doppler method and displaying it in two dimensions in real time is called tissue Doppler imaging, and quantification of cardiac function such as identification of myocardial infarction site and diagnosis of myocardial contractile function. Is attracting attention as an effective technique for comprehensive diagnosis.

  The motion of the subject tissue can be decomposed into an integral motion component in which the entire subject tissue moves integrally, and a relative motion component between each point of the subject tissue, that is, a motion component due to deformation of the subject tissue. Conceivable. Therefore, when evaluating a specific motor function of the subject tissue, it is necessary to extract only a motor component related to the motor function. For example, the motion of the heart includes the integral motion of the entire heart and the diastolic contraction of the heart muscle.Therefore, when trying to correctly evaluate the diastolic contraction function of the heart muscle, it is detected by the ultrasonic Doppler method. It is necessary to remove the velocity component due to the integral movement of the entire heart from the velocity, and obtain the velocity component solely due to the diastolic contraction movement.

  Therefore, conventionally, for example, Patent Literature 1 and Non-Patent Literature 1 have been proposed as devices or methods for extracting a velocity component of the diastolic contraction movement of the heart. In these techniques, a point which is the center of expansion and contraction of the myocardium is first determined, and the translational speed of the entire heart is determined from the movement of this point. Then, by subtracting the speed of the translational motion from the speed of the myocardial tissue obtained by the ultrasonic Doppler method, the speed component due to the expansion and contraction motion of the myocardial tissue has been calculated.

JP-A-6-114059 "Wall Motion Imaging in Tissue Doppler Method", Transactions of the Japanese Society of Ultrasonics, 1993.11. pp67-672

  However, the integral movement of the entire subject tissue includes not only translational movement but also rotational movement. In the above-described prior art, the influence of the translational movement of the subject tissue can be removed, but no consideration is given to the rotational movement. Therefore, the velocity components obtained by these conventional techniques include the velocity component of the integral rotational movement of the subject tissue, and do not represent the velocity component due to the pure expansion / contraction movement. Therefore, the conventional apparatus has a problem that the velocity component of the pure diastolic contraction movement of the myocardium cannot be accurately obtained. In addition, conventionally, it has not been possible to properly determine the velocity component of the integral rotational movement of the myocardium.

  The present invention has been made to solve the above-described problem, and has as one of its objects to obtain an angular velocity of an integral rotational movement of the entire subject tissue. According to another aspect of the present invention, a velocity component due to the integral translational and rotational movements of the subject tissue is removed from the velocity of the subject tissue detected by the ultrasonic Doppler method. It is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of extracting only components. Still another object of the present invention is to obtain a two-dimensional velocity vector of each part of the subject tissue by using the obtained velocity component of the integral rotational movement of the whole subject tissue.

  In order to achieve the above-described object, a first configuration of the present invention includes a contour detection unit that detects a contour of a subject tissue in an ultrasonic image for each frame, and a main axis of inertia of the contour of the subject tissue in each frame. And an angular velocity calculating means for calculating an angular velocity of an integral rotational movement of the subject tissue from a change in the inclination of the inertial spindle between frames.

  Further, the second configuration of the present invention further includes a motion speed calculating means for calculating a motion speed of each point of the subject tissue based on the ultrasonic echo signal, and a center of inertia of a contour of the subject tissue in each frame, A translation speed calculating means for obtaining the speed of the integral translational movement of the subject tissue from the displacement of the center of inertia between; and a velocity component due to the integral rotational motion of each point of the subject tissue based on the angular speed obtained by the angular speed calculating means. The rotational speed calculation means to be determined and, for each point of the subject tissue, by subtracting the speed of the integral translational motion and the speed component by the integral rotational motion from the motion speed, the expansion and contraction motion of each point of the subject tissue is obtained. Expansion / contraction speed calculating means for obtaining a speed component.

  Further, a third configuration of the present invention, in addition to the first configuration, further includes a Doppler velocity detecting unit that determines an ultrasonic beam direction velocity component of each point of the subject tissue based on the ultrasonic echo signal, A translation speed calculating means for obtaining a center of inertia of the contour of the tissue of the object, a translational speed of the integrated movement of the object tissue from the displacement of the center of inertia between the frames, and an object based on the angular velocity obtained by the angular velocity calculating means. A rotational speed calculating means for obtaining a velocity component of each point of the tissue by the integral rotational movement, and an inertia of each point of the subject tissue based on the velocity of the integral translational movement and the velocity component of each point of the specimen tissue by the integral rotational movement. A tangential velocity calculating means for finding a velocity component around the center; a two-dimensional velocity vector of each point of the subject tissue based on the velocity component of the ultrasonic beam direction at each point of the subject tissue and the velocity component around the center of inertia. And having a speed vector calculation means for obtaining, a.

  Further, by subtracting the radial component of the speed of the integral translational motion from the radial component of the two-dimensional velocity vector with respect to the center of inertia of each point of the subject tissue for each point of the subject tissue, An expansion / contraction speed calculating means for obtaining a speed component by the expansion / contraction movement may be provided.

  In the first configuration of the present invention, first, the contour detecting means detects the contour of the subject tissue for each frame of the ultrasonic image, for example, in the case of the heart, the boundary between the myocardial portion and the blood flow portion. Next, the inertia principal axis calculation means obtains the inclination of the inertia principal axis of the contour detected by the contour detection means. Here, the principal axis of inertia is an orthogonal axis having the maximum and minimum moments of inertia of the contour graphic around each axis among orthogonal axes having the center of inertia (center of gravity) of the contour graphic as the origin. This principal axis of inertia can be said to be an axis indicating the directionality of the contour figure. Even if the subject tissue is slightly deformed, it is considered that the direction of the contour figure hardly changes due to the deformation, so the change in the inclination of the principal axis of inertia may be attributed to the integral rotation of the entire subject tissue. it can. Therefore, by detecting how much the inclination of the principal axis of inertia changes between frames by the angular velocity calculating means, the angular velocity of the integral rotational movement of the subject tissue can be obtained.

  As described above, according to the first configuration of the present invention, the angular velocity of the integral rotational movement of the subject tissue can be obtained, and this angular velocity can be used as a quantitative evaluation value of the movement of the subject tissue. it can.

  In the second configuration of the present invention, only the component due to the pure expansion / contraction movement is extracted from the movement of the subject tissue using the angular velocity of the integral rotational movement of the subject tissue obtained in this manner.

  That is, the motion of the subject tissue is considered to be a superposition of the integral translational motion of the subject tissue, the integral rotational motion of the subject tissue, and the expansion / contraction motion of the subject tissue. Therefore, the velocity at a certain point of the subject tissue is the sum of the velocity component due to the integral translational movement, the velocity component due to the integral rotational movement, and the velocity component due to the expansion / contraction movement. Therefore, by subtracting the velocity component due to the integral translation and the velocity component due to the integral rotational movement from the velocity of each point of the subject tissue obtained using the ultrasonic Doppler method, the velocity due to the pure expansion / contraction movement is obtained. The components can be determined.

  Therefore, in the second configuration of the present invention, the motion velocity calculating means obtains the motion velocity of each point of the subject tissue using the ultrasonic Doppler method, and the translation velocity calculating means calculates the frame at the position of the center of inertia of the contour. The speed of the integral translational movement of the subject tissue is determined based on the displacement between them. Further, the rotational speed calculating means obtains the velocity component of the integral rotational movement of each point of the subject tissue from the angular velocity of the integral rotational movement. Then, the speed component of the expansion / contraction movement is obtained by subtracting the speed component of the integral translational motion and the integral rotation motion from the motion speed of each point of the subject tissue by the expansion / contraction speed calculation means.

  The third configuration of the present invention is a configuration in a case where only the velocity component in the ultrasonic beam direction can be obtained by the ultrasonic Doppler method. The third configuration is based on the integral translational and rotational velocity components of each point of the subject tissue obtained from the contour information and the velocity component in the ultrasonic beam direction obtained by the Doppler method. Calculate the velocity vector. In the fourth configuration, the velocity component of the expansion / contraction movement is calculated based on the two-dimensional velocity vector of each point of the subject tissue.

  That is, when considering a polar coordinate system having the origin at the center of inertia of the subject tissue, the two-dimensional velocity vector of each point of the subject tissue includes the tangential speed component around the center of inertia of the subject tissue and the motion with respect to the center of inertia. It can be decomposed into a velocity component in the radial direction (expansion and contraction direction). Here, the speed of the integral rotational movement of the subject tissue has only a tangential speed component, and the speed of the expansion / contraction movement of the subject tissue has only a radial speed component. Further, the speed of the integral translation of the subject tissue has speed components in both the tangential direction and the radial direction. Therefore, the tangential component of the two-dimensional velocity vector at each point of the subject tissue is the sum of the speed component due to the integral rotational motion and the tangential component of the integral translational motion speed of the subject tissue. On the other hand, the radial component of the two-dimensional velocity vector at each point is the sum of the velocity component due to the expansion and contraction movement at that point and the radial component of the velocity of the integral translational movement of the subject tissue.

  Here, the velocity of the integral translational movement and the integral rotational movement can be obtained from the contour information of the subject tissue independently of the velocity component in the ultrasonic beam direction by the ultrasonic Doppler method. Therefore, the tangential component of the two-dimensional velocity vector of each point of the subject tissue can be obtained based on the velocity components of the integral translational movement and integral rotational movement. By combining this tangential velocity component with the velocity component in the ultrasonic beam direction obtained by the ultrasonic Doppler method, a true two-dimensional velocity vector can be obtained.

  Therefore, in the third configuration of the present invention, the Doppler velocity detecting means determines the ultrasonic beam direction velocity component of each point of the subject tissue, and the translation speed calculating means calculates the displacement between frames of the inertial center position of the contour of the subject tissue. The speed of the integral translational movement of the subject tissue is obtained based on Further, the rotational speed calculating means obtains a velocity component of each point of the subject tissue due to the integral rotational movement from the angular velocity of the integral rotational movement. Then, the tangential velocity calculating means obtains a tangential velocity component of each point of the subject tissue based on the velocity of the integral translational movement and the velocity component of the integral rotational movement. The velocity vector calculation means calculates a two-dimensional velocity vector of each point of the subject tissue based on the tangential velocity component of each point of the subject tissue and the velocity component of the ultrasonic beam direction thus obtained.

  In addition, as described above, the radial component of the two-dimensional velocity vector of each point of the subject tissue is the sum of the velocity component due to the expansion / contraction movement and the radial component of the velocity of the integral translation movement. By subtracting the radial component of the speed of the integral translation from the radial component of the two-dimensional velocity vector, the speed of the expansion / contraction movement at each point of the subject tissue can be obtained.

  Therefore, if the expansion / contraction speed calculation means is provided, for each point of the subject tissue, the radial component of the integral translational motion is subtracted from the radial velocity component of the two-dimensional velocity vector, The rate of expansion and contraction of each point of the subject tissue can be obtained.

  As described above, according to the present invention, the angular velocity of the integral rotational movement of the entire subject tissue can be obtained based on the contour information of the subject tissue. This angular velocity can be used as an evaluation value of the motion of the subject tissue.

  Further, according to another aspect of the present invention, for each point of the subject tissue, a speed component of the integral translational motion and a speed component caused by the integral rotational motion are calculated from the motion speed obtained using the Doppler method. By subtraction, it is possible to extract a velocity component based solely on the expansion / contraction movement from the velocity of the subject tissue on which various movement components are superimposed. The velocity component of the diastolic movement can be used for evaluation of the diastolic function of the heart.

  According to still another aspect of the present invention, even when only the velocity component in the ultrasonic beam direction is obtained by the ultrasonic Doppler method, the contour information of the subject tissue is used to obtain each point of the subject tissue. A two-dimensional velocity vector can be obtained, and a velocity component due to expansion and contraction movement of each point of the subject tissue can be obtained.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  Hereinafter, an embodiment of the ultrasonic diagnostic apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the ultrasonic diagnostic apparatus according to the present invention. In FIG. 1, a scanning control unit 70 controls transmission and reception of ultrasonic waves by the probe 10 via the transmission / reception unit 20 based on a timing signal from a timing signal generation unit 72. At this time, the scanning control unit 70 uses the unit vector [ _ek ] indicating the direction of the ultrasonic beam currently being transmitted and received as an index when displaying the echo information and the Doppler information obtained by the transmission and reception of the ultrasonic wave. The coordinates (x, y) of each point on the ultrasonic beam are sequentially generated and output. In the following description, those enclosed in parentheses [] indicate vector quantities. The coordinates (x, y) generated by the scanning control unit 70 are represented by a predetermined orthogonal coordinate system (hereinafter, referred to as a probe coordinate system) with the probe 10 as an origin.

  The echo signal obtained by the transmission and reception of the ultrasonic wave is input from the probe 10 to the transmission / reception unit 20, and thereafter processed by being divided into two paths. In one route, a process for generating a B-mode tomographic image of the subject is performed, and on the other, a process for generating a Doppler tomographic image is performed. Hereinafter, the flow of each signal processing will be described in detail.

  First, signal processing for B-mode image generation will be described.

  The echo signal output from the transmission / reception unit 20 is first amplified by the amplification unit 22 to a predetermined level. The detection unit 24 detects the amplified echo signal and generates a luminance signal corresponding to the amplitude of the echo signal. This luminance signal is digitized by the A / D converter 26 and then input to a DSC (Digital Scan Converter) 60 to be scan-converted so as to conform to the scanning format of the display 64. The output signal of the DSC 60 is converted to an analog signal by the D / A converter 62 and displayed on the display 64 as a B-mode image.

  Next, signal processing for Doppler image generation will be described.

  The echo signal output from the transmission / reception unit 20 is subjected to quadrature detection by the quadrature detection unit 28. At this time, the quadrature detector 28 performs quadrature detection by multiplying the echo signal by reference signals having a phase difference of 90 degrees output from the timing signal generator 72. From the quadrature detector 28, a Doppler signal composed of two signals, a real part and an imaginary part, is output.

  The Doppler signal output from the quadrature detector 28 is digitized by the A / D converter 30 and then input to the low-pass filter 32. The low-pass filter 32 extracts only a low frequency band Doppler signal from the input digital signal. For example, when the subject is a heart, the blood flow in the heart cavity has a high velocity, so that the Doppler signal in the blood flow portion has a relatively high frequency, while the tissue such as the myocardium has a lower motion velocity than the blood flow. Generates a low frequency Doppler signal. Therefore, the low-pass filter 32 removes the Doppler signal in the high frequency band of the blood flow portion, and extracts the Doppler signal of the tissue portion such as the myocardium. The Doppler signal of the subject tissue extracted by the low-pass filter 32 is input to the autocorrelation unit 34, and the autocorrelation is obtained by a known correlation calculation process.

Then, based on the correlation signal obtained by the autocorrelation unit 34, the Doppler velocity calculation unit 36 determines the velocity (Doppler velocity) v _k of each point of the subject tissue in the ultrasonic beam direction. The variance calculator 38 also calculates the variance σ ^{2 of the} Doppler signal indicating the state of the velocity distribution of the subject tissue based on the correlation signal.

  In a normal ultrasonic Doppler diagnostic apparatus, the Doppler velocity and variance obtained in this manner are displayed. In the apparatus of this embodiment, in addition to this, two points of each point of the subject (for example, myocardium) tissue are further displayed. A process is performed to obtain a dimensional velocity vector and a velocity component due to the expansion / contraction movement.

  As described above, in order to obtain the velocity component due to the expansion and contraction movement of the subject tissue, it is necessary to obtain the integral translation and rotation velocity components of the entire subject tissue, and to remove these components. Therefore, in the present embodiment, the velocity components of the integral translational movement and the integral rotational movement of the subject tissue are obtained using the B-mode information.

  In this embodiment, the center of inertia of the contour of the subject tissue is determined for each frame, and the speed of the integral translational movement of the subject tissue is determined based on the displacement of the center of inertia between the frames. Further, the inclination of the principal axis of inertia of the contour of the subject tissue is determined for each frame, and the angular velocity of the integral rotational movement is determined based on the change in the inclination between the frames.

  First, the center of inertia calculation unit 40 detects the contour of the subject tissue based on the luminance signal output from the A / D conversion unit 26, and obtains the coordinates of the center of inertia of the contour.

  That is, the inertial center calculation unit 40 detects the contour of the subject tissue based on the echo signal data for one frame provided from the A / D conversion unit 26. For example, in the case of the heart, there is a large difference in the intensity (amplitude) of the echo signal between the myocardial tissue and the blood flow portion. That is, the contour of the myocardial tissue can be obtained.

The detection of the contour is performed for each ultrasonic beam (that is, for each scanning line). Therefore, as shown in FIG. 3, for each ultrasonic beam 100 that is sector-scanned from the probe 10, the echo signal data is viewed in the direction along the ultrasonic beam, and the echo level exceeds the threshold value. The edge portion is detected as a contour point (that is, a boundary point between the blood flow region 110 and the subject tissue 120) P ₁ ,... P _i , P _{i + 1} ..., P _N (N is the total number of obtained contour points). Then, the coordinates P _i (x _i , y _i ) are obtained. Here, the coordinates of each contour point P _i are expressed in a probe coordinate system. The outline 115 of the blood flow region is represented by the outline points thus obtained. For example, 1 if the number of ultrasonic beams in the frame of the scan is 64, the coordinates of the contour point P _i of about 100 points is obtained.

Based on the contour point coordinate data obtained in this way, the inertia center calculating unit 40 calculates the coordinates (x _g , y _g ) of the inertia center G of the contour point according to the following equation (1). The coordinates (x _g , y _g ) of the center of inertia G are shown in the probe coordinate system.

The obtained inertia center G of the coordinates (x _g, y _g) the coordinates (x _i, y _i) of each contour point is input together with the inertial main axis computing section 42. Note that the coordinates (x _g , y _g ) of the center of inertia G are also input to the velocity calculation processing unit 50 in order to determine the translational movement velocity of the subject tissue.

Next, based on the coordinates of each contour point and the coordinates of the center of inertia G, the inertial principal axis calculation unit 42 calculates the inclination φ of the principal axis of inertia of the contour in the image of the frame. For this purpose, first, the inertia principal axis calculation unit 42 sets the coordinates of each contour point to a coordinate system having the center of inertia G (x _g , y _g ) as an origin (hereinafter referred to as an inertia center coordinate system) according to the following equation (2). Coordinate).

  The inertial center coordinate system (XY coordinate system) is a coordinate system parallel to the probe coordinate system (xy coordinate system).

In this manner, when the coordinate conversion is completed, the further principal axis of inertia calculating unit 42, the moment of inertia M _X and M _Y each axis of inertia around the center coordinate system (i.e. X-axis and Y-axis), products of inertia M _XY is _{calculated according} to the following equations (3), (4) and (5).

The principal axis of inertia calculating unit 42 calculates the inclination of the principal axis φ according to the following equation (6) using the M _X, M _Y and M _XY.

  The inclination φ of the principal axis of inertia determined in this manner is input to the speed calculation processing unit 50.

The velocity calculation processing unit 50 calculates the expansion / contraction movement of each point of the subject tissue from the inertia center coordinate and the inclination of the inertia main axis determined in this way and the Doppler velocity v _k determined in the Doppler velocity calculation unit 36. Find the velocity component. FIG. 2 is a block diagram showing the internal configuration of the speed calculation processing unit 50. Hereinafter, the calculation process in the speed calculation processing unit 50 will be described with reference to FIG.

  First, the process of obtaining the integral translational movement speed [V] (vector amount) of the entire subject tissue will be described.

The coordinates (x _{g (m)} , y _{g (m)} ) of the center of inertia G _m obtained by the center of inertia calculation unit 40 are input to the translation speed calculation unit 510 and the memory 502 of the speed calculation processing unit 50. Here, G _m indicates the center of inertia of the contour of the subject tissue in the m-th frame of the ultrasonic image, and the coordinates (x _{g (m)} , y _{g (m)} ) are the coordinates of the center of inertia G _m. . These coordinates are shown in a probe coordinate system. The memory 502 holds the input coordinate data of the center of inertia for one frame. The translation speed calculation unit 510 calculates the coordinates (x _{g (m)} , y _{g (m)} ) of the input inertia center G _m of the m-th frame and the inertia center of the immediately preceding frame stored in the memory 502. Using the coordinates (x _{g (m-1)} , y _{g (m-1)} ) of G _m−1, the translational motion speed [V] is obtained according to equation (7).

  Here, Δt is a time interval between successive frames.

  The integrated translation speed [V] obtained in this way is input to the dilation / contraction speed calculation unit 522 and the tangential speed calculation unit 518.

Next, a process of obtaining an integral angular velocity ω of the subject tissue will be described. The inclination φ _m of the inertia main shaft obtained by the inertia main shaft calculation unit 42 is input to the angular velocity calculation unit 512 and the memory 504 in the speed calculation processing unit 50. Here, the inclination φ _m indicates the inclination of the principal axis of inertia of the subject tissue contour in the m-th frame. The memory 504 holds the input inclination φ _m for one frame. Then, the angular velocity calculation unit 512 uses the input inclination φ _m of the principal axis of inertia of the m-th frame and the inclination φ _m-1 of the principal axis of inertia of the immediately preceding frame held in the memory 504 to calculate the next The angular velocity ω of the integral rotation of the subject tissue is obtained according to the equation (8).

  The angular velocity ω of the integral rotation of the subject tissue obtained in this manner can be used as a feature amount relating to the motion state of the subject tissue. For example, the state of rotation of the subject tissue can be known by displaying the state of the change of the angular velocity ω on the display of the ultrasonic diagnostic apparatus. Further, the inclination φ of the main inertia axis itself is displayed on a display, which can be used for diagnosis.

  When the velocity [V] of the integral translation and the angular velocity ω of the integral rotation of the subject tissue are obtained in this manner, the velocity [V] of the integral translation and the angular velocity of the integral rotation are then determined. Using ω, the two-dimensional velocity vector and the speed of the expansion-contraction movement at each point of the subject tissue are determined. Hereinafter, the principle of this method will be described.

FIG. 4 is a diagram showing a relationship between a probe coordinate system (xy coordinate system) and an inertial center coordinate system (XY coordinate system). The position vector of an arbitrary point P in the subject tissue in the center of inertia coordinate system is [r], the position vector of the same point P in the probe coordinate system is [x], and the center of inertia G is in the probe coordinate system. Assuming that the position vector is [R], as shown in FIG. 4, these vectors satisfy the following relational expression.

In this case, considering the minute displacement d [x] of the point P, the minute displacement d [x] is a minute displacement d [R] of the center of inertia and a minute displacement d caused by rotation of a small angle around the center of inertia. [Φ] × [r] and a minute displacement d [r] in the radial direction connecting the center of inertia G and the point P are added.

  In the equation (10), the vector d [φ] is a vector indicating a minute rotation, that is, a minute change in the inclination φ of the principal axis of inertia. FIG. 5 shows the relationship between the vectors d [φ], [r], d [φ] × [r] in an inertial center coordinate system (however, expanded to three dimensions to introduce a rotation vector). As shown in this figure, the vector d [φ] indicating the minute rotation is a vector in the Z-axis direction. Then, since the minute displacement d [φ] × [r] of the point P due to the rotation is a vector product of d [φ] and [r], it is a vector perpendicular to both d [φ] and [r]. is there. Therefore, as shown in FIG. 5, d [φ] × [r] is a tangential vector at the point P in the XY plane.

Here, assuming that a minute time during which the minute displacement occurs is dt, the following relational expression is derived from the expression (10).

  In the equation (11), d [R] / dt is a vector indicating the velocity of the center of inertia G, which is equal to the velocity [V] of the integral translation described above. Further, d [φ] / dt indicates a change per unit time of the inclination φ of the principal axis of inertia, which is equal to the angular velocity [ω] of the integral rotational movement of the subject tissue. Note that the angular velocity vector [ω] has the magnitude of the angular velocity ω obtained by the above equation (8), and its direction is equal to the direction of d [φ].

Here, d [x] / dt is a two-dimensional velocity vector of the point P, which is represented as [v]. Furthermore, the magnitude of the velocity of the expansion and contraction movement of the point P and v _r, the unit vectors of the radial and [e _r] (see FIG. 5), d [r] / dt = v r [e r] It becomes. Therefore, by using these relationships, the above equation (11) can be expressed as the following equation.

  [V] in this equation is obtained by the translation speed calculation unit 510.

となる。（１３）式において、ｒはベクトル［ｒ］の大きさであり、この値は慣性中心Ｇの座標と点Ｐの座標から求めることができる。また、ωは、角速度演算部５１２で求められ、［ｅφ］は慣性中心Ｇの座標と点Ｐの座標が分かれば求めることができる。従って、（１２）式において、［Ｖ］及び［ω］×［ｒ］は被検体組織の輪郭についての幾何学的情報から求めることができる。 If the unit vector in the tangential direction at the point P is [eφ] (see FIG. 5),

It becomes. In the expression (13), r is the magnitude of the vector [r], and this value can be obtained from the coordinates of the center of inertia G and the coordinates of the point P. Further, ω can be obtained by the angular velocity calculation unit 512, and [eφ] can be obtained by knowing the coordinates of the center of inertia G and the coordinates of the point P. Therefore, in equation (12), [V] and [ω] × [r] can be obtained from geometric information on the contour of the subject tissue.

Here, the tangential component vφ of the velocity [v] at the point P satisfies the relation vφ = [v] · [eφ]. This can be obtained by using the relations of the equations (12) and (13). It can be simplified like an equation.

  Since [V], [eφ], r and ω on the right side of the equation (14) can be obtained as described above, the tangential component vφ of the speed of the point P can be obtained from these.

となる。この（１５）式の両辺のベクトルについて、それぞれ［ｅ_r ］との内積をとれば、

となる。ここで、［ｅ_r ］は、慣性中心Ｇの座標と点Ｐの座標が分かれば求めることができるので、（１６）式の右辺においては［ｖ］のみが未知のベクトルとなる。 Further, when the above equation (12) is modified,

It becomes. By taking the inner product of each vector on both sides of this equation (15) with [ _er ],

It becomes. Here, [ _er ] can be obtained if the coordinates of the center of inertia G and the coordinates of the point P are known, so only [v] is an unknown vector on the right side of the equation (16).

Therefore, in this embodiment, the tangential component vφ of the speed of the point P obtained from the equation (14) and the ultrasonic beam direction speed component v _{k of the} point P obtained by the Doppler method are used to calculate the point P. A two-dimensional velocity vector [v] is calculated.

That is, the following relational expression holds between the two-dimensional velocity vector [v] and the ultrasonic beam direction velocity component v _k .

[ _Ek ] is a unit vector indicating the ultrasonic beam direction, and is a vector in the direction toward the probe. Θ is the angle between [e _k ] and [v].

FIG. 6 illustrates the relationship between the velocity vector [v] of the point P in the subject tissue and each velocity component. The angle γ is the angle between the tangential direction at the point P and the ultrasonic beam direction. As can be seen from FIG. 6, the tangential component vφ of the two-dimensional velocity vector [v] satisfies the following equation.

となる。この式の右辺において、ｖ_k はドプラ法で検出でき、ｖφは（１４）式から算出でき、γは超音波ビームの方向と慣性中心Ｇ及び点Ｐの座標から一意的に決まるので、この式によってcos θを求めることができる。 By eliminating v from equation (18) using equation (17) and solving for θ,

It becomes. On the right side of this equation, v _k can be detected by the Doppler method, v φ can be calculated from equation (14), and γ is uniquely determined from the direction of the ultrasonic beam and the coordinates of the inertia center G and the point P. Cos θ can be obtained by

  Then, by using the obtained cos θ, the absolute value v of the velocity vector [v] can be calculated by Expression (17). When v and cos θ are obtained in this manner, the velocity vector [v] of the point P is specified from the relationship with the ultrasonic beam direction.

  As described above, in the present embodiment, the velocity vector [v] of the point P in the subject tissue is obtained from the Doppler speed and the velocity components of the integral translational movement and the rotational movement obtained from the contour information of the subject tissue. be able to.

By using the speed determined vector [v] in (16), the velocity component v _r by expansion and contraction movement of the point P is determined.

Or at speed calculation processing unit 50, a velocity vector of a point in the subject tissue [v], the principle for obtaining the velocity component v _r of the expansion and contraction movement of the point.

In accordance with this principle, the speed arithmetic processing section 50 shown in FIG. 2, obtaining the velocity component v _r of the two-dimensional velocity vector of the object tissue points [v] and expansion and contraction movement.

  As described above, the translational speed [V] of the integral translational motion of the subject tissue and the angular velocity ω of the integral rotational motion necessary for this computation are used as the translational speed calculation units 510 and 510 using the contour information of the subject tissue, respectively, as described above. It is determined by the angular velocity calculation unit 512.

  Then, the rotation speed calculation unit 514 uses the angular speed ω obtained by the angular speed calculation unit 512 to obtain a speed component of the rotation around the center of inertia caused by the integral rotation.

That is, the rotational speed calculation unit 512 from the radius vector calculation unit 506, the radius vector length r from the inertial center G _m to the subject tissue points are given. The radial length r is determined by the coordinates (x _{g (m)} , y _{g (m)} ) of the center of inertia G _m obtained by the center of inertia calculation unit 40 and the subject tissue output from the scan control unit 70. The radius calculation unit 506 calculates the coordinates based on the coordinates (x, y) of each point. Therefore, the rotation speed calculation unit 514 sequentially calculates the rotational speed rω of the rotational movement of each point around the center of inertia by multiplying the radial length r by the angular velocity ω for each point of the subject tissue. The obtained rotational speed rω of each point is input to the tangential speed calculator 518.

The tangential speed calculator 518 calculates the rotational speed rω of each point of the subject tissue thus determined, the translational motion speed [V] determined by the translational speed calculator 510, and the unit vector generator 508. Using the given tangential unit vector [eφ] for each point of the subject tissue, a tangential component vφ of the velocity of each point of the subject tissue is determined. Among them, tangential unit vector [E?] In the subject tissue each point, the inertial center calculation unit coordinates of the inertial center G _m obtained in 40 _{(x g (m), y} g (m)), the scan control The unit vector generation unit 508 obtains the coordinates based on the coordinates (x, y) of each point of the subject tissue obtained by the unit 70. Accordingly, the tangential velocity calculation unit 518 obtains the tangential direction component vφ of the velocity of each point of the subject tissue by substituting these [V], rω, and [eφ] into the equation (14). The obtained tangential velocity component vφ is input to the two-dimensional velocity vector calculation unit 520.

  The two-dimensional velocity vector calculation unit 520 determines a two-dimensional velocity vector [v] of each point of the subject tissue based on the tangential velocity component vφ of each point of the subject tissue thus determined.

That is, the two-dimensional velocity vector calculation unit 520 includes, for each point of the subject tissue, the tangential velocity component vφ, the Doppler velocity v _k determined by the Doppler velocity calculation unit 36, and the sin calculated by the trigonometric function generation unit 516. γ and cos γ are input. Here, the angle γ is an angle between the tangential direction about the point P and the ultrasonic beam direction. Trigonometric function generating unit 516, a cos gamma by the inner product operation between the ultrasound beam direction unit vector [e _k] inputted from the tangential unit vector [E?] And the scanning control unit 70 which is input from the unit vector generating unit 508 Then, sin γ is obtained using this cos γ. Therefore, the two-dimensional velocity vector calculation unit 520 uses the sin γ and cos γ determined in this way, the tangential velocity component vφ and the Doppler velocity v _k that have already been determined, and calculates the equation (19). To calculate cos θ. Is the angle between the ultrasonic beam direction and the two-dimensional velocity vector [v], and the direction of the two-dimensional velocity vector [v] is determined by calculating cos θ. Further, the two-dimensional velocity vector calculation unit 520 calculates the absolute value v of the two-dimensional velocity vector [v] based on the above equation (17), using the obtained cos θ and the Doppler velocity v _k . The two-dimensional velocity vector [v] of each point of the subject tissue is specified by the cos θ and v thus obtained.

  The two-dimensional velocity vector [v] thus obtained for each point of the subject tissue is input to the multiplexer 524.

The data of the two-dimensional velocity vector [v] for each point of the subject tissue is input to the expansion / contraction speed calculation unit 522, and is used for calculating the velocity component v _r by the expansion / contraction movement of each point of the subject tissue. Can be

That is, in addition to the two-dimensional velocity vector [v] data for each point of the subject tissue, the expansion / contraction speed calculation unit 522 calculates the speed [V] of the integral translational movement of the subject tissue and the motion for each point of the subject tissue. Using the radial unit vector [e _r ], the velocity component v _r due to the expansion / contraction movement is calculated based on the equation (16). Note that radial unit vector [e _r] are coordinates of the inertial center G _m and _{(x g (m), y} g (m)), based on the of the subject tissue each point coordinates (x, y) , Are obtained by the unit vector generator 508.

The velocity component v _r of the expansion / contraction movement at each point of the subject tissue thus obtained is input to the multiplexer 524.

Multiplexer 524, in response to a control signal from the display switching control unit (not shown), and outputs either one of the two-dimensional velocity vector [v] and expansion and contraction movement of the velocity component v _r, or both data to DSC 60.

Then, DSC 60 is thus two-dimensional velocity vector obtained in the [v] and the expansion and contraction movement of the velocity component v _r, superimposed to form a display image on the B mode information and variance (sigma ²⁾ information. The display image thus formed is converted into an analog signal by the D / A converter 62 and displayed on the display 64. In the display, for example, the two-dimensional velocity vector [v] is represented as an arrow. The velocity component v _r of the expansion / contraction movement represents the direction of expansion or contraction in different colors, as in the case of the Doppler image, and the magnitude of the velocity component is represented by luminance. At this time, the coordinates of the inertia center G obtained by the inertia center calculation unit 40 may be displayed at the same time. Of course, the expression format of each information is not limited to this.

As described above, according to the present embodiment, based on the velocity component of the ultrasonic beam direction obtained by the ultrasonic Doppler method and the velocity component of the integral translational motion and the rotational motion obtained from the contour information of the subject tissue, the object is obtained. The two-dimensional velocity vector of each point of the specimen tissue and the velocity component of the expansion and contraction movement of each point of the specimen tissue can be obtained and displayed. Expansion and contraction movement velocity component v _r of, for example, in the diagnosis of heart are useful for accurately assess the extension contractile function. This embodiment can be used for diagnosis of arteries and the like in addition to the heart.

  In the present embodiment, the B-mode information is used to determine the integral translational and rotational motion velocity components of the subject tissue. However, the present invention is not limited to this, and the contour of the subject tissue is obtained from Doppler information. A configuration in which the integral translation and rotational speed components are obtained from the contour may be used. In this case, the subject tissue and the blood flow portion can be determined based on the power of the Doppler signal or the magnitude of the Doppler speed.

  Further, in this embodiment, since only the velocity component in the ultrasonic beam direction is obtained from the Doppler information, the velocity component of the dilation / contraction movement is obtained after calculating the two-dimensional velocity vector using the contour information of the subject tissue. However, if the two-dimensional velocity vector can be obtained from the Doppler information using, for example, the two-beam method, the velocity component of the expansion-contraction movement can be directly obtained from the above equation (15).

It is a block diagram showing the whole composition of the example of the present invention. FIG. 3 is a block diagram illustrating an internal configuration of a speed calculation processing unit. FIG. 3 is a diagram illustrating a relationship between a subject tissue and a contour point. FIG. 3 is a diagram illustrating a relationship between a probe coordinate system and an inertial center coordinate system. It is a figure showing relation of various vectors. FIG. 4 is a diagram illustrating a relationship between a two-dimensional velocity vector [v] of a point P in a subject tissue and each velocity component.

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 10 probe, 20 transmission / reception part, 22 amplification part, 24 detection part, 26, 30 A / D conversion part, 28 quadrature detection part, 32 low-pass filter, 34 autocorrelation part, 36 Doppler velocity operation part, 38 dispersion operation part , 40 inertia center operation unit, 42 inertia spindle operation unit, 50 speed operation processing unit, 60 DSC (digital scan converter), 62 D / A conversion unit, 64 display unit, 502, 504 memory, 506 radial operation unit, 508 Unit vector generator, 510 translation speed calculator, 512 angular speed calculator, 514 rotation speed calculator, 516 trigonometric function generator, 518 tangential speed calculator, 520 two-dimensional speed vector calculator, 522 extended contraction speed calculator, 524 Multiplexer.

Claims (3)

In an ultrasonic diagnostic apparatus that transmits and receives an ultrasonic beam to and from an object and generates and displays an ultrasonic image based on an ultrasonic echo signal,
Contour detection means for detecting the contour of the subject tissue in the ultrasonic image for each frame,
Inertia spindle calculation means for determining the inclination of the inertia spindle of the contour of each frame,
An angular velocity calculating means for calculating an angular velocity of an integral rotational movement of the subject tissue from a change between frames of the inclination of the inertia main axis,
An ultrasonic diagnostic apparatus comprising: The ultrasonic diagnostic apparatus according to claim 1,
A movement speed calculating means for calculating a movement speed of each point of the subject tissue based on the ultrasonic echo signal,
Translation speed calculating means for determining the center of inertia of the contour in each frame, and calculating the speed of the integral translational movement of the subject tissue from the displacement of the center of inertia between frames;
A rotation speed calculation unit that calculates a speed component of the respective points of the subject tissue due to the integrated rotation motion based on the angular speed obtained by the angular speed calculation unit;
For each point of the subject tissue, by subtracting the velocity of the integral translational movement and the velocity component of the integral rotational movement from the movement velocity, the velocity component of the subject tissue at each point due to the expansion / contraction movement is calculated. Expansion and contraction speed calculating means to be obtained;
An ultrasonic diagnostic apparatus comprising: The ultrasonic diagnostic apparatus according to claim 1,
Doppler velocity detecting means for determining an ultrasonic beam direction velocity component of each point of the subject tissue based on the ultrasonic echo signal,
Translation speed calculating means for determining the center of inertia of the contour in each frame, and calculating the speed of the integral translational movement of the subject tissue from the displacement of the center of inertia between frames;
A rotation speed calculation unit that calculates a speed component of the respective points of the subject tissue due to the integrated rotation motion based on the angular speed obtained by the angular speed calculation unit;
A tangential velocity calculating means for calculating a velocity component around the center of inertia of each point of the subject tissue based on the velocity of the integral translational movement and the velocity component of each point of the specimen tissue due to the integral rotational movement;
Velocity vector calculating means for obtaining a two-dimensional velocity vector of each point of the subject tissue based on the ultrasonic beam direction velocity component of each point of the subject tissue and a velocity component around the center of inertia,
An ultrasonic diagnostic apparatus comprising:

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