JP2008073279A - Ultrasonic diagnostic apparatus and ultrasonic image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To display ultrasonic images of the condition of the blood in vivo flows in an easily understandable fashion. <P>SOLUTION: The flow of the blood is displayed in a particulate image as a dynamic image. The particulate image has a group of particles 61 and the group of particles 61 is composed of a plurality of particles 62. A plurality of novel particles are generated in a prescribed spawning line. The two-dimensional velocity vectors referred at the respective display positions determines the moving destinations of the individual particles. As prescribed finishing requirements are met, the display is finished for the particles involved. It is possible to vary the size, hue (brightness), shape and the like of the particles, for example, according to the magnitude, large or small, of the velocity. The adoption of the particles peripherally blurred is also possible. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus and an ultrasonic image display method, and more particularly to display of a blood flow changing with time.

  The ultrasonic diagnostic apparatus has a function of displaying a blood flow image on a two-dimensional tomographic plane. The blood flow image is a color image, which is synthesized and displayed on a two-dimensional tissue image (B-mode tomographic image) as a black and white image. The blood flow image is conventionally called a color Doppler image or a color flow image. As described in Patent Document 1, in a typical blood flow image, for example, blood that flows in a direction approaching the ultrasound probe is expressed in red, and blood that flows in a direction away from the ultrasound probe. Is displayed in blue. The speed in each direction is associated with the luminance. Blood flow that moves at high speed is expressed with high brightness, and blood flow that moves at low speed is expressed with low brightness. Note that dispersion information may be displayed together with the speed information, and in this case, the magnitude of the dispersion is expressed by a change in hue. A conventional blood flow image is an image that simply displays the velocity distribution of the blood flow on the scanning plane in color, and represents only the velocity component in the beam direction, so it recognizes the actual flow from the blood flow image. It is very difficult to do.

  Several techniques for calculating a two-dimensional velocity vector for blood flow have already been proposed (Patent Documents 2-8). Patent Documents 2-4 describe calculating a two-dimensional velocity vector (or information corresponding thereto) from two velocity components obtained on two beams having different deflection angles. Patent Documents 5-6 describe that a two-dimensional velocity vector is calculated from two velocity components obtained on two beams that intersect on a target. Patent Document 7 describes that a two-dimensional velocity vector is calculated from a beam direction velocity component distributed on a scanning plane based on a certain assumption about the flow. Patent Document 8 describes that two-dimensional vector information is displayed using a change in hue.

JP 59-20820 A Japanese Patent Laid-Open No. 62-152436 Japanese Patent Laid-Open No. 62-152437 JP-A-3-4842 JP-A-3-47241 JP-A-7-204204 JP 2005-110939 A JP 62-152439 A

  It is difficult to intuitively understand the state of blood flow from a conventional blood flow image, or skill is required for this purpose. Further, details of blood flow cannot always be displayed in a conventional blood flow image.

  An object of the present invention is to realize a new blood flow display method that replaces the conventional blood flow display method.

  Another object of the present invention is to provide a blood flow image capable of intuitively and specifically recognizing the state of blood flow.

  An ultrasonic diagnostic apparatus according to the present invention includes a calculation unit that calculates a plurality of pieces of motion information for a plurality of points in a living body based on a reception signal obtained by transmitting and receiving ultrasonic waves to and from a living body, And an image forming unit that forms an image expressing blood flow in the living body as motion of a plurality of display elements based on a plurality of motion information.

  According to the above configuration, a specific state of the blood flow can be observed by observing a plurality of display elements that move on the screen. For example, eddy currents, turbulent flows, stagnation, etc. can be specified on the screen. Thereby, for example, if the target organ is the heart, it is possible to identify an abnormal flow (for example, short-circuit flow, reverse flow) occurring in the heart. Although it is possible to display only one display element, it is desirable to display a plurality of display elements at the same time, which makes it easier to understand the state of the spatially expanding flow. The number of display elements can be increased or decreased in consideration of the purpose of observation and the amount of calculation.

  Preferably, each display element is a particle, and the image forming unit is a particle image forming unit that forms a particle image as the image. The particle image is a completely new image that directly represents a state in which a plurality of blood elements (for example, red blood cells) are moving in a tissue such as a heart or a blood vessel. The virtual particles as display elements are preferably artificially generated computer graphic elements that can be displayed in various forms. The outline may be clearly displayed, but may be intentionally blurred. Or it is good also as a pseudo-indefinite shape like a fluid. The size and color can also be determined arbitrarily. The particle image is usually displayed as a moving image, and a plurality of particles move while simulating a specific state of flow. For example, if the target organ is the heart, it is possible to observe in detail the state of flow near the valve. If the target organ is the carotid artery, the flow disturbance due to the plaque present in the blood vessel can be observed as the movement of the particles. Desirably, the plurality of particles move independently of each other on the screen. When calculating the display position of a certain particle, in addition to the movement information corresponding to the particle, movement information or display position corresponding to another particle may be considered. The display position of each particle may be calculated in consideration of the dispersion state of the particle group or the flow tendency.

  Preferably, the motion information is a two-dimensional or three-dimensional velocity vector. The velocity vector can be calculated by the method described in Patent Documents 1-7, the inter-frame pattern matching method, the method using the spatial gradient of motion information, and the like. That is, two velocity components that are orthogonal (or intersecting) may be actually measured, or only a velocity component in one direction is measured and a velocity vector (or information corresponding thereto) is obtained from a spatial distribution of the velocity components. ) May be calculated. A three-dimensional velocity vector may be calculated to form a three-dimensional particle image, or a two-dimensional particle image reflecting the three-dimensional velocity vector may be formed. According to such an image, for example, it is possible to represent a flow orthogonal to the scanning plane. The exercise information is usually calculated from the Doppler information, but the exercise information may be calculated from the luminance information of the blood flow portion.

  Preferably, the calculation unit generates a velocity vector matrix as the plurality of motion information, and the particle image forming unit, for each particle, based on a kth (where k is an integer) velocity vector matrix. A velocity vector corresponding to the k-th particle position is specified, and the (k + 1) -th particle position is determined based on the specified velocity vector. The velocity vector matrix is composed of a plurality of velocity vectors arranged spatially. The velocity vector corresponding to the kth particle position is selected from the velocity vector matrix or is generated by interpolation processing. Interpolation processing may be applied at the generation stage of the velocity vector matrix. The velocity vector matrix is composed of a plurality of velocity vectors measured at a plurality of positions (a plurality of sample points) in the transmission / reception space. Here, the intervals between the plurality of positions may be equal or non- It may be even. The above k corresponds to the number of display times or the display position serial number for each particle.

  Preferably, the calculation unit generates a velocity vector matrix as the plurality of motion information for each frame, and the particle image forming unit generates a current particle based on a current velocity vector matrix for each of the particles. A specifying unit that specifies a velocity vector corresponding to the position; and a determining unit that determines a next particle position based on the specified velocity vector for each of the particles. By repeatedly referencing the velocity vector corresponding to the current particle position and determining the movement destination (next display position) based on it (by relaying or updating the display position), the particles can be moved on the screen. it can. When a particle reaches the position of zero velocity, the particle will stop on the screen. At that time, the particles may disappear once from the screen, or the display may be continued. After that, if a velocity vector occurs at that position, the particles will move again accordingly. If there is a possibility of generating particles that are stopped for a long time, individual or collective time management may be applied as described later. Error processing may be applied when the calculated display position exceeds an appropriate range. The above-described frame corresponds to a transmission / reception frame, a display frame, or a data array constituting an operation unit.

  Preferably, the particle image forming unit includes a generating unit that causes a plurality of new particles to appear on the screen at predetermined time intervals. Preferably, the predetermined time interval is a time interval corresponding to m (where m is an integer) frames. One or a plurality of new particles may be generated for each frame, or one or a plurality of new particles may be generated for each frame. Preferably, the predetermined time interval is a time interval corresponding to n (where n is an integer) heartbeats. One or a plurality of new particles may be generated for each heartbeat, or one or a plurality of new particles may be generated for a plurality of heartbeats. Alternatively, one or a plurality of new particles may be generated when a predetermined condition is satisfied. Preferably, the generation unit causes the plurality of new particles to appear on the basis of a particle generation line defined in the screen. The particle generation line is preferably set on the upstream side in the bloodstream, but if there is a particularly focused part, the particle generation line may be set immediately before that. A plurality of particle generation lines may be set simultaneously. Preferably, the generation unit causes the plurality of new particles to appear in a generation area defined in the screen. Generation areas are user-specified areas, discriminated heart chamber areas, and the like.

  Preferably, the particle image forming unit includes an updating unit that hides the particle displayed at the previous particle position and displays the particle at the current particle position for each frame. Preferably, the particle image forming unit displays an update unit that displays one or more afterimage particles for one or more past particle positions and displays particles at the current particle position for each frame. Including. If one or a plurality of afterimage particles are displayed, it becomes easy to recognize the movement path of each particle.

  Preferably, the particle image forming unit includes an erasing unit that erases specific particles satisfying a predetermined disappearance condition from the screen. Preferably, the erasing unit individually erases specific particles whose elapsed time from the generation time has reached the end time from the screen. According to this configuration, it is possible to cope with a calculation error. Preferably, the erasing unit individually erases specific particles that have reached the particle extinction line from the screen. Preferably, the erasing unit individually erases specific particles out of the particle display area from the screen. Preferably, the eraser erases all particles that have been displayed on the screen at the same time according to the heartbeat. For example, a plurality of particles may appear at the first time phase for each heartbeat, and the particles may disappear at a predetermined time phase thereafter. Further, the particle display may be intermittently performed only in the diastole or systole.

  Preferably, the particle image forming unit includes a display processing unit that changes at least one of luminance and hue of each particle continuously or stepwise. Preferably, the particle image forming unit includes a display processing unit that changes the form of each particle continuously or stepwise based on motion information corresponding to each particle.

  Preferably, each particle is a computer graphic element having a clear outline or a blurred shape. Preferably, in the real-time display mode, the particles move at the same speed as the blood flow, and in the regeneration mode, the particles move at a speed according to the regeneration speed. In the case of flow regeneration, the speed of blood flow is apparently slow and the movement of each particle is slow, so that the state of the flow can be recognized more clearly. Preferably, the locus of each particle is displayed together with each particle. When displaying the locus, interpolation processing may be applied so that the locus becomes a smooth curve. If the trajectory display is adopted in the case of still image display, the movement of particles can be recognized even on the still image. Preferably, the particle image is a color image, and the particle image is displayed so as to be superimposed on a black and white tomographic image. A black and white tomographic image is a monotone background image, and if a particle image expressed in color is displayed there, the blood flow can be raised and clearly shown.

  The method according to the present invention includes a step of calculating a plurality of velocity vectors for a plurality of points in a two-dimensional or three-dimensional living space based on Doppler information obtained by transmitting / receiving ultrasonic waves to / from a living body. Forming a particle image representing the motion of the fluid in the living body as a two-dimensional motion or a three-dimensional motion of a plurality of virtual particles based on the plurality of velocity vectors; and moving the particle image into a moving image And a step of displaying as The method according to the present invention can be realized not only on an ultrasonic diagnostic apparatus having an ultrasonic transmission / reception function and an image processing function, but also on an information processing apparatus that processes data output from the ultrasonic diagnosis. It is.

  Preferably, the step of forming the particle image includes a step of identifying a velocity vector corresponding to a current particle position, a step of determining a next particle position from the obtained velocity vector, and a step of determining the next particle position. Displaying the particles. According to this, paying attention to each particle, the display position is sequentially updated. For example, the particle density can be non-uniform in the heart chamber, but such spatial density change is also useful information that can be considered as diagnostic information.

  As described above, according to the present invention, it is possible to recognize the state of the blood flow intuitively and specifically.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the overall configuration of the ultrasonic diagnostic apparatus according to this embodiment. As will be described in detail below, this ultrasonic diagnostic apparatus has a function of forming a particle image representing blood flow in a living body.

  The probe 10 has an array transducer. The array transducer is composed of a plurality of transducer elements, and an ultrasonic beam is formed by the array transducer. The ultrasonic beam is scanned electronically. As an electronic scanning method, electronic linear scanning, electronic sector scanning, and the like are known. A 2D array transducer may be provided for the probe 10, and a 3D echo data capturing space may be formed by the 2D array transducer. The probe 10 is used in contact with the surface of a living body in the present embodiment, but may be used by being inserted into a body cavity. As will be described later, in order to measure a velocity vector as motion information, a plurality of probes or a plurality of array transducers can be used simultaneously as necessary.

  The transmission unit 12 functions as a transmission beam former. The transmission unit 12 supplies a plurality of transmission signals to the plurality of vibration elements. As a result, a transmission beam is formed by the array transducer. Reflected waves from the living body are received by a plurality of vibration elements, whereby a plurality of received signals are output from the probe 10 to the receiving unit 14. In the present embodiment, the organ to be subjected to ultrasonic diagnosis is the heart. The reflected wave from the living body includes a Doppler shift frequency component corresponding to the blood flow velocity.

  The reception unit 14 functions as a reception beam former. A phasing addition process is performed on a plurality of reception signals input to the reception unit 14, thereby forming a reception beam electronically. The reception signals corresponding to the respective reception beams are output to the tomographic image forming unit 16 and the vector calculation unit 18 in the present embodiment. A plurality of reception beams may be simultaneously formed for one transmission beam. Usually, in order to improve the measurement accuracy of Doppler information, transmission / reception is performed a plurality of times for one beam address.

  The tomographic image forming unit 16 generates a tomographic image as a B-mode image based on echo data groups (that is, a plurality of received signals corresponding to a plurality of ultrasonic beams) on the scanning surface formed by electronic scanning of the ultrasonic beam. Form. The image data is sent to the display processing unit 22. The tomographic image forming unit 16 includes a module such as a digital scan converter (DSC).

  On the other hand, the vector calculation unit 18 calculates a two-dimensional velocity vector for each point (each coordinate) on the scanning plane based on the reception signal output from the reception unit 14. In this embodiment, the vector calculation unit 18 converts a received signal into a complex signal by quadrature detection processing, an autocorrelator that performs an autocorrelation operation on the complex signal, and a beam direction velocity component from the autocorrelation result. It includes a speed calculator for calculating. Further, for each position (coordinates as sample points) on the scanning plane, a vector calculator that calculates two orthogonal velocity components as a two-dimensional velocity vector is provided. A plurality of two-dimensional velocity vectors calculated for a plurality of positions on the scanning plane constitute a vector matrix (vector set or vector array). This vector matrix is generated for each frame. The vector calculation unit 18 also includes a DSC and other modules. In order to calculate the velocity component, it is also possible to use an FFT calculator and other calculators. All or some of the functions of the vector calculation unit 18 may be realized as software functions.

  The two-dimensional velocity vector can be calculated using various methods such as the method described in Patent Documents 1-7, the inter-frame pattern matching method, and the method using a spatial velocity gradient. is there. The vector matrix information output from the vector calculation unit 18 is output to a vector image forming unit 26, a locus image forming unit 28, and a particle image forming unit 30 described later. Here, the vector image is an image representing a blood flow by a plurality of arrows as will be described later with reference to FIG. The trajectory image is an image representing the blood flow by a plurality of lines as will be described later with reference to FIG. Instead of the two-dimensional velocity vector, a three-dimensional velocity vector may be calculated. Further, instead of the velocity vector, other motion information indicating the direction and magnitude of the flow may be calculated. Furthermore, exercise information may be obtained from echo information (luminance information) of the blood portion without using Doppler information. For example, between two tomographic image frames, pattern matching processing may be applied to a plurality of sample points in the blood flow portion, and temporal changes of individual sample points may be observed for each frame. In forming a particle image, it may be considered to use dispersion information, power information, acceleration information, and other information.

  The particle image forming unit 30 is a module that forms a blood flow image in which blood flow in a living body is expressed as movement of a plurality of display elements. In the present embodiment, a plurality of virtual particles are used as a plurality of display elements. ing. The particle image will be described in detail later with reference to FIG. 2 and the like. Each of the plurality of particles is a computer graphic element and moves independently of each other on the screen. The particle image corresponds to an image representing a state in which a plurality of blood elements (for example, red blood cells) flow in the heart. The direction and speed of movement of each particle are determined based on the vector matrix described above. The image data of the particle image formed by the particle image forming unit 30 is output to the display processing unit 22.

  The display processing unit 22 has a color calculation function, an image composition function, and the like. In the present embodiment, a vector image, a trajectory image, and a particle image can be selectively displayed as a blood flow image. In that case, a tomographic image is displayed as the background image. In particular, in the present embodiment, a color-processed particle image is synthesized on a black and white tomographic image (luminance image, monotone image), and such a synthesized image is displayed on the display 32. Both tomographic images and particle images are moving images, and temporal changes in the structure of the heart and temporal changes in blood flow motion can be observed through such synthesized images. In the present embodiment, the composite image can be displayed on the display device 32 in real time, but a reproduced image can be displayed on the display device 32 based on the data stored in the storage unit 20. . In this case, the playback speed of the composite image can be arbitrarily set. The particle image, the vector image, and the trajectory image may be displayed as still images, or an image obtained by combining them may be displayed.

  The controller 34 controls the operation of each component shown in FIG. The control unit 34 includes a CPU and an operation program. Incidentally, the particle image forming unit 30 is realized by a function of dedicated hardware or software. The control unit 34 may have a particle image forming function. An operation panel 36 having a keyboard and a trackball is connected to the control unit 34. The electrocardiograph 38 is a unit that measures an electrocardiogram signal from a subject that is an object of ultrasonic diagnosis. An electrocardiogram signal or information corresponding thereto is sent to the particle image forming unit 30 and the display processing unit 22. Such information may be output to the control unit 34 as necessary.

  A display example is shown in FIG. Reference numeral 40 represents a display screen. On the display screen 40, a composite image 42 as an ultrasonic image is displayed, and an electrocardiogram waveform 44 is displayed. The composite image 42 is composed of a tomographic image and a particle image. Preferably, the former is a background image as a black and white image, and the latter is an overlay image as a color image. However, the particle image may be a background image and the tomographic image may be an overlay image. It is also possible to form a composite image by selecting any image data in units of pixels. In FIG. 2, the r direction indicates the ultrasonic beam direction, that is, the depth direction. The θ direction indicates the electronic scanning direction of the ultrasonic beam. In this embodiment, the electronic sector method is adopted.

  In this example, Doppler information is measured for a part of the region 56 in the entire scanning plane, that is, the region 56 corresponds to a region of interest where blood flow is observed. Of course, you may make it observe Doppler information over the whole area | region which forms a B-mode tomographic image. Or you may restrict | limit the magnitude | size of the area | region which observes a blood flow in the depth direction. In the present embodiment, the region 56 is defined as a region surrounded by the lines 58 and 60. The positions of the lines 58 and 60 can be arbitrarily set by the user.

  The tomographic image shown in FIG. 2 is a tomographic image centered on the left ventricle of the living body (human body) in the present embodiment. Reference numeral 46 indicates the left ventricle, reference numeral 48 indicates the left atrium, reference numeral 50 indicates the mitral valve, and reference numeral 52 indicates the aortic valve. Reference numeral 54 represents a part of the aorta. Reference numeral 202 represents a myocardium (heart wall), and reference numeral 200 represents a heart chamber filled with blood. The particle image according to the present embodiment is displayed as a moving image, and a particle group 61 is represented on each frame. The particle group 61 includes a plurality of particles 62 whose display positions change with time. That is, by sequentially updating the display position of each displayed particle in each frame, it is possible to realize a visual expression as if the particle actually moved. Of course, the particles that have entered the region where the blood flow does not substantially move are expressed as if they stopped on the screen, and thereafter, when a flow occurs in the region, the particles start to move accordingly. In the case of a healthy person, a plurality of particles enter the left ventricle 46 from the left atrium 48 via the mitral valve 50 according to the heartbeat, and a plurality of particles pass from the left ventricle 46 via the aortic valve 52 to the aorta 54. To flow. In that case, some of the particles are temporarily stored in the left ventricle 46 and are mixed with a particle group that later enters the left ventricle 46 in the next heartbeat. If such a process is repeated for each heartbeat, the pumping action of the heart can be observed as a moving image.

  Thus, if a particle image is displayed as a moving image, it becomes possible to easily grasp the blood flow visually by moving the particle group. The individual particles can be generated, for example, as computer graphic elements expressed in red, so that the display of the individual particles is clear. Conventionally, when the level of the received signal is low or when the blood flow velocity is low, there has been a problem that the display of blood flow information is unclear due to them, but according to the display of the particle image, The problem can be solved or reduced. In addition, for example, when a vortex is generated in the left chamber 46, the particles reflect the vortex motion. There is an advantage that a specific aspect of a flow that is difficult to express in a conventional color Doppler image can be expressed visually and clearly. As will be described later, various parameters such as the number, density, size, and hue of the particles can be arbitrarily set by the user. For example, only a few particles may be displayed to reduce the amount of computation, or tens or hundreds of particles may be displayed to express the flow state at each point in detail. .

  In FIG. 2, reference numeral 204 represents a line as a margin crossing the left atrium, and similarly, reference numeral 206 represents a line as a margin crossing the aorta. However, in the illustrated example, the line 206 does not cross the entire aorta and extends to the line 60 corresponding to the end of the region 56. As will be described later, for example, the line 204 may be defined as a particle boiling line (particle generation line), and the line 206 may be defined as a particle suction line (particle disappearance line). In addition, about the particle | grains exceeding the line 58 and the line 60, the deviation of a display area is determined and it does not display. Therefore, in the present embodiment, these lines 58 and 60 also function as particle extinction lines.

  In forming a particle image, it is desirable to limit the particle movement region so that each particle does not enter the myocardium by mistake. Therefore, the boundary 200A between the myocardium 202 and the heart chamber 200 may be detected, and the inside (that is, the heart chamber 200) may be defined as a particle display area, that is, a particle motion region. In addition to the region 56, a region of interest having a predetermined shape such as a circle or an ellipse may be set, and display of each particle may be allowed in the region of interest. That is, particles that deviate from the region of interest may be deleted from the screen. Various conditions can be defined for the particle generation condition, the extinction condition, and the position update condition, which will be described in detail later.

  The particle image is configured as a moving image, and a particle group 61 is newly displayed for each frame. That is, all of the particle groups displayed on the previous frame are erased in the current frame, and a new particle group is displayed in the current frame. On the other hand, an afterimage of particles may be displayed at one or more past particle positions. For example, as indicated by reference numerals 63-1 to 63-4, afterimage particles may be displayed on the past movement trajectory of a certain particle. In that case, it is desirable to apply a process for reducing the particle luminance as it goes in the opposite direction of the time axis. Further, a line as indicated by reference numeral 64 may be displayed along the particle movement trajectory. Such a line display has an advantage that the movement locus can be understood more intuitively.

FIG. 3 shows a method for updating the particle display. In the present embodiment, the display position is sequentially calculated on each frame for each particle that appears on the screen. Thus, when a particle image is observed as a moving image, an image as if the particles are actually moving can be constructed. In FIG. 3, (A) shows a display coordinate system, and (B) shows a vector matrix 72 calculated for each frame. For example, when the current display position is P ₀ and the two-dimensional velocity vector associated therewith is v ₀ , the x-direction component and the y-direction component of the two-dimensional velocity vector v ₀ are specified, By multiplying each component by Δt, which is the time between frames, the next display position p ₁ can be specified. That is, the coordinate x ₁ in the x direction at the next display position is obtained by (x ₀ + v _x0 × Δt), and y ₁ is obtained by (y ₀ + v _y0 × Δt). Subsequently, even when the next display position P ₂ is calculated based on the display position P ₁ , the same calculation is executed. That is, for each frame, the two-dimensional velocity vector corresponding to each particle is referenced on the vector matrix 72, and the particle display position on the next frame is calculated based on the reference result. This is repeated for each frame, and the display position of the particles is sequentially updated.

  Incidentally, when the two-dimensional velocity vector corresponding to the current display position does not exist on the vector matrix 72, a plurality of two-dimensional velocity vectors existing in the vicinity of the display position are referred to, and vector interpolation processing based on them is performed. A two-dimensional velocity vector can be obtained. Alternatively, a high-density two-dimensional velocity vector matrix may be configured by obtaining a plurality of two-dimensional velocity vectors for a plurality of sample points and then applying an interpolation process. According to this method, a two-dimensional velocity vector corresponding to a display position can be immediately selected from a high-density two-dimensional velocity vector matrix for each frame. In the present embodiment, the above display position update process is executed for each particle. In this case, when the display positions calculated for a plurality of particles are the same, these particles may be displayed as they are at the same display position, or any one of the particles may be displayed as a representative. Also good. Alternatively, a merge process in which a plurality of particles are regarded as one particle may be applied. On the other hand, when the dispersion is large, one particle may be divided into a plurality of particles during the movement. Various display forms can be selectively employed according to the flow state at each point.

  Next, generation | occurrence | production of particle | grains is demonstrated using FIG.4 and FIG.5. FIG. 4 shows a particle generation line 74. On this generation line 74, a plurality of particles (new particle row 76) are generated at a predetermined timing. At that time, the two-dimensional velocity vector corresponding to each particle position is referred to, and each particle starts to move according to the above-described process. In many cases, each particle will flow from the left atrium through the mitral valve into the left ventricle. As shown in FIG. 4, the particle generation line 74 is set in the upstream portion of the blood flow in the illustrated example, and specifically, is set in the left atrium. In particular, it is set near the most upstream line 204. A new new particle array may be generated for each frame, or a new particle array may be generated for each of a plurality of frames. The user may variably set m (where m is an integer) that defines the generation cycle in units of frames. Alternatively, a new particle train may be generated only in a representative frame within one heartbeat, or a new particle train may be generated in a representative frame within a plurality of heartbeats. The user may variably set n (where n is an integer) that defines the generation cycle in units of heartbeats. The position, length, and shape of the particle generation line 74 can be arbitrarily determined by the user. Instead of the one-dimensional particle generation line, a two-dimensional particle generation region may be set. Further, the line 204 constituting the edge of the scanning surface may be defined as a particle generation line. In this case, both ends 80A and 80B of the line 204 may be input by the user, and new particle arrays may be sequentially generated in the section 80 between them. In the case of observing the function of the mitral valve and the backflow, it is desirable to generate particles inside the left atrium which is upstream as shown in FIG.

  Also shown in FIG. 4 is a particle extinction line 78. Each particle is erased from the screen when it reaches the particle extinction line 78. Accordingly, the particle annihilation line 78 is desirably set so as to traverse the entire path through which the particle passes. In this embodiment, the particle annihilation line 78 includes both ends inside the heart wall on both sides of the aorta. An extinction line 78 is set. Instead of the particle annihilation line 78, the line 206 may be defined as a particle annihilation line. In this case, for example, the points 82A and 82B which are both ends of the aorta are designated by the user, the section 82 crossing the aorta is defined, and the section 84 is automatically set as a range in which particles can substantially flow. It may be defined as follows. Alternatively, the image display of particles may be stopped using a condition of deviation from the particle display area.

  Note that, as described above, the boundary between the heart wall 202 and the heart chamber 200 may be detected, or the entire outer edge of the heart chamber 202 may be extracted to allow movement of particles only within the heart chamber. Alternatively, since the heart wall itself is a low-speed moving body, the heart wall region may be automatically recognized and the display of particles entering the region may be stopped. However, in order to reliably display the particles passing through the septal defect hole or the like, it is desirable that the display of particles representing an abnormal flow passing through the heart wall is not interrupted. Similarly, it is desirable that the particles representing the reverse flow generated by the mitral valve or the like be expressed with a display mode different from the particles representing the other normal flows.

  In the generation method shown in FIG. 5, a plurality of lattices 86 are defined in the heart chamber 200, and particle groups are generated on the plurality of lattice points in a frame of a predetermined time phase in one heartbeat. Of course, a particle group may be generated for each frame. In the example shown in FIG. 5, the particle groups regularly arranged in the vertical direction and the horizontal direction are generated, but it is also possible to generate the particle groups at random.

  In addition, in the generation method shown in FIGS. 4 and 5, since new particle arrays repeatedly appear at the same position, when a sense of incongruity occurs in image observation, a state of dissociation is formed by a fade-in method. It is desirable to make a plurality of new particles appear after being made. According to such a configuration, each particle can be gradually lifted on the screen, so that the problem of unnatural particle boiling can be solved. However, in order to accurately specify the display position of each particle sequentially, it is necessary to continuously perform the calculation of the particle movement destination from the first frame without interruption.

  In the above description, the particles are not displayed or the display position update process is stopped with the condition to reach a certain part, but the individual particles are referred to by the elapsed time from the generation for each particle. Forcibly extinguishing timing may be determined. For example, even when a specific particle stays in the heart chamber due to some problem in computation, such a particle can be naturally extinguished by using the timeout method. Alternatively, conversely, for example, particles staying in the heart can be highlighted and used for disease diagnosis.

  Depending on where the particles are generated, most of the particles may flow into a part of the heart and not so much into other parts. In such a case, the generation site and the new particle density may be adjusted as appropriate. Or you may make it set a particle | grain boiling place in the vicinity about the site | part where particle | grain deficiency produces regularly.

  In the present embodiment, an electrocardiogram signal is acquired. For example, particles can be generated in synchronization with the electrocardiogram signal, and particles can be extinguished in synchronization with the electrocardiogram signal. Further, a different hue for each heartbeat may be given to the particles so that the replacement state of blood flow between heartbeats can be clearly observed.

  FIG. 6 shows a display operation as a timing chart. (A) represents an electrocardiogram signal, and each heartbeat and time phase can be specified by this electrocardiogram signal. (B) shows a frame synchronization signal, which defines the timing of each frame. As shown in (C), a new particle group may be repeatedly generated for each frame. Here, reference numerals 210, 212, and 214 represent new particle groups generated in the respective frames. Each of these particle groups is composed of a plurality of new particles, and each particle is erased from the screen when one of the extinction conditions is met. That is, each individual line 210a represents the lifetime of each particle from generation to disappearance. Further, (D) shows another generation method. In this example, a new particle group is generated for each heartbeat in synchronization with an electrocardiogram signal. This is indicated by reference numerals 216 and 218. It is desirable to give different hues to these new particle groups. Incidentally, in the operation shown in (C), it is desirable to automatically change the number of new particles generated for each frame. For example, the number of new particles generated may be varied based on the average velocity on the particle generation line. For example, since the instantaneous flow rate increases when the mitral valve is open, the number of new particles generated is increased, and when the mitral valve is closed, the instantaneous flow rate decreases, so the number of new particles generated is reduced. You may make it make it. In any case, it is desirable to form a particle image that faithfully simulates the actual blood flow as much as possible.

  FIG. 7 shows a particle display method as a flowchart. The operation shown in FIG. 7 is executed for each particle. Hereinafter, one particle to be described is referred to as a target particle. In S101, the current frame number i corresponding to the initial frame is recognized. In S102, the initial coordinates of the target particle on the particle generation line are specified in the i-th frame, and the corresponding two-dimensional velocity vector is referred to. In S102, the target particle is displayed at the initial coordinates. However, the above-described fade-in method may be applied so that the target particle gradually appears on the screen. In S102, a timer for managing a timeout for the target particle starts a timing operation.

  In S103, the movement destination (next display position) of the target particle in the k (= i + 1) th frame is determined. That is, it is estimated to which position a certain minute part in the bloodstream moves after one frame. This estimation is performed based on the two-dimensional velocity vector and the time between frames.

  In S104, it is determined whether or not the elapsed time by the timer has reached a predetermined time (disappearance time). In S105, it is determined whether or not the target particle has moved out of the particle display area (particle motion area). In S106, it is determined whether or not other termination conditions are met. If any termination condition is satisfied, the display of the target particle is terminated in S107. In this case, the target particle may gradually disappear from the screen by applying a fade-out method.

  On the other hand, when none of the end conditions is satisfied, the target particle is displayed at the destination determined in S103 above in S108. That is, the display position of the target particle is updated. In S109, the two-dimensional velocity vector corresponding to the current display position is specified based on the vector matrix corresponding to the kth frame, and in S110, the movement destination of the target particle on the (k + 1) th frame is determined. . In S111, a numerical value represented by k + 1 is newly substituted for k. Such processing is repeatedly executed. Incidentally, the kth frame means the current frame, and the (k + 1) th frame means the next frame.

  According to the operation shown in FIG. 7, the next display position is specified from the current particle position, and this is repeated. As a result, the target particle moves on the screen. In the process, when any termination condition is satisfied, the display of the target particle is terminated. The above processing is applied to all the particles appearing on the screen, that is, the operation shown in FIG. 7 is executed by the number of particles. Therefore, the number of particles to be displayed on the screen may be determined in consideration of the calculation amount and the calculation capability of the apparatus. For example, even if two or three particles are displayed, if the particles are repeatedly displayed on the screen, the whole blood flow can be easily imaged in the head. Alternatively, if hundreds or thousands of particles are displayed at the same time, an expression that is very close to the actual blood flow can be obtained. However, when the number of particles to be displayed is excessively large, it becomes difficult to recognize the position and movement of each particle, particularly when there is almost no gap between the particles. Therefore, it is desirable to appropriately determine the number of particles to be displayed in consideration of the overall purpose of diagnosis, computing ability, user preference, and the like. Alternatively, when a large number of particles are displayed at a high density, it is desirable to adopt a display form in which individual particles can be clearly recognized.

  As shown in FIGS. 8A to 8C, it is desirable that the size, hue (luminance), and shape of the particles can be freely changed. In this case, the user may select a desired parameter, or the parameter may be automatically varied based on speed or other information. (A) shows a plurality of particles having different sizes by 90a-90e, (B) shows particles having different hues by 92a-92e, and (C) shows 94a-94c. Particles with different shapes are shown. For example, when the speed increases, the particle size may be increased, and the luminance of the particle may be increased at the same time. Moreover, in order to improve visibility, you may make it bring about the hue change from red to orange according to the speed of particle | grains. Further, when the speed of the particles is increased, the shape may be changed stepwise such as a circle, an ellipse, or a tear drop shape.

  FIG. 9 shows various functions for varying the luminance of the particles according to the speed or the like. First, D indicates a function that does not change the luminance according to the speed or the like, and A and B indicate functions that linearly change the luminance according to the speed or the like. C represents a function for changing the luminance in a non-linear manner according to the speed or the like. It is possible to select and use an appropriate function according to the user's desire or measurement conditions. For example, a portion with a higher flow velocity may be expressed with higher luminance on the screen. In the low-speed region or the region where there is almost no velocity component, the particles can be hidden once, but since there is actually blood flow there, the particles also have a certain brightness. It is desirable to assign From such a viewpoint, it is desirable to select the function B or the function C shown in FIG. Although the luminance function is shown in FIG. 9, the number of color correlations or the saturation function may be used. In addition, the attribute of the particle may be changed continuously or stepwise according to other motion information, for example, dispersion or power, instead of changing the attribute of the particle depending on the speed.

  FIG. 10 shows one of the particle extinction conditions. In this example, a determination line 96 is defined on the heart chamber side along the boundary 100A between the heart chamber and the heart wall. When the center coordinate 100 of the particle 98 exceeds the determination line 96 and reaches the heart wall side, the particle is not displayed. That is, in the example shown in FIG. 10, since the center 100A of the particle 98A that has advanced forward is located on the heart cavity side of the determination area 96, the particle 98A is displayed as it is, and the particle further advances forward, When the center 100B of the particle 98B reaches the heart wall side with respect to the determination line 96, the particle 98B is not displayed. This makes it possible to prevent the problem that particles enter the heart wall or the problem that particles stick to the surface of the heart wall. However, it is desirable to determine the extinction conditions so that the blood flow passing through the septal defect hole is displayed. Specifically, it is desirable to set display conditions so that particles having a certain speed are positively displayed.

  FIG. 11 shows an example of vortex flow. That is, the particles 102a to 102j represent the display positions of the particles over a plurality of frames. In this example, the particles are moved like a spiral, and finally the display of the particles is terminated by a timeout. This is represented by reference numeral 102j. For example, when blood flow occurs in the depth direction perpendicular to the scanning plane, it is impossible to observe the accurate speed by observing the two-dimensional velocity vector. In such a case, if particles are kept on the screen as they are, It becomes a display mode different from the flow of. Therefore, in this embodiment, time-out processing is used, and particles that unnaturally stay in the heart chamber are erased as much as possible from the screen. However, if the flow is restored at the site, the particles will start to move again. Therefore, it is desirable to determine the staying particles when the movement has stopped for a certain period of time and eliminate them. .

  As shown in FIG. 12, the ultrasonic diagnostic apparatus shown in FIG. 1 can selectively adopt various display methods according to the operation state. Examples of the operating state include real-time measurement 104, freeze / still image display 106, normal playback 108, slow playback (or reverse slow playback) 110, and the like. The real-time measurement 104 indicates a normal measurement state, and a freeze or still image display state 106 is obtained by a freeze operation, and then normal reproduction 108 or slow reproduction 110 is performed by reading data from the cine memory. On the other hand, as a display method, a vector display 114, a particle display 116, a trajectory display 118, and a composite display 120 can be selected in addition to the conventional color Doppler display 112. The composite display 120 applies the plurality of displays described above simultaneously.

  FIG. 13 shows an example of a trajectory image. A trajectory image 124 is shown together with the tomographic image on the display screen 122, and the trajectory image 124 is composed of a plurality of lines 126 representing the flow state. In this example, a plurality of lines 126 extend from a plurality of positions on the spring line 128, and in this case, the direction in which the front ends of the respective lines can be determined by the above-described calculation method of the particle movement destination. According to the trajectory image, how each minute part in the bloodstream flows can be expressed by a plurality of lines. In that case, a plurality of particles may be displayed together on each line as indicated by reference numeral 127.

  FIG. 14 shows an example of a vector image. A vector image 126 is displayed on the display screen 124, and its background image is a black and white tomographic image. The vector image 126 includes a plurality of particles 128 and a plurality of arrows (symbols) 130 set for each particle. Each arrow represents a two-dimensional velocity vector at the point. If a vector image is directly combined with a real-time moving image, the arrow 130 moves violently at a site where the flow changes drastically, and it cannot be observed. For this reason, it is desirable to display the vector image 126 as a still image. Alternatively, it is desirable to display such a vector image in the slow playback mode.

  In the present embodiment, a plurality of attribute information is managed for each particle. A specific example is shown in FIG. Incidentally, FIG. 14 shows a state in which specific particles in a vector image are designated by a pointing device and attribute information is displayed. Of course, also in the particle image shown in FIG. 2, attribute information can be displayed for each particle by the same method. In this example, the attribute information 132 includes particle identifier (ID), particle coordinates (display coordinates), vector information (direction, size), elapsed time since generation, graphic information (size, form, color), variance value. , Power values, etc. If necessary, other information may be added to the attribute information.

  In the above-described embodiment, the two-dimensional velocity vector is acquired, but a three-dimensional velocity vector may be observed instead. It is also possible to construct a particle image as a three-dimensional image. For example, as shown in FIG. 15, the blood flow inside the blood vessel 134 can be displayed three-dimensionally and the blood flow inside the blood vessel 134 can be displayed as a particle image 136 composed of a plurality of particles. According to such an expression, when there is a plaque on the inner surface of the blood vessel and local turbulence is generated thereby, the turbulence can be captured from the movement of the particles. Incidentally, it is also possible to construct a two-dimensional particle image by observing a three-dimensional velocity vector for each of a plurality of sample points on a certain plane and using those three-dimensional velocity vectors. In that case, there is an advantage that the particle image can be formed in consideration of the velocity component in the depth direction.

  FIG. 16 shows another display example of the particle image. The same components as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. In the particle image shown in FIG. 16, the particle group 140 is composed of a plurality of particles 142, and each particle 142 is configured such that its outer edge is vague and blurred. Incidentally, the center coordinate of the particle is indicated by reference numeral 143. That is, the outer edge of each particle constituting the particle image does not need to be clear, and it is sufficient if the position (that is, movement) can be visually identified. For example, as shown by reference numeral 142A in FIG. 17, a mode in which the concentration is gradually reduced from the central part to the peripheral part is adopted as the basic form of the particles, and as shown by reference numerals 142C and 142D, The particle morphology may be varied according to the direction of the velocity vector. Alternatively, the particle size can be varied as indicated by reference numeral 142B in accordance with the magnitude of the velocity. Incidentally, reference numeral 143 indicates the center coordinates. In addition, you may make it employ | adopt an amorphous liquid form as a form of particle | grains.

  In forming the particle image, the density of the ultrasonic beam can be reduced as compared with the conventional method as long as the particle image can be accurately configured. In the conventional method, for example, about 10 transmissions / receptions per beam direction are necessary. However, according to the present embodiment, even if the number of transmissions / receptions is reduced, it does not immediately blur the particles. When the heart is affected by the translational motion of the heart itself or the hand shaking of the probe, such an overall motion is detected between frames, and such motion components are canceled and individual two-dimensional velocity vectors are detected. May be requested. In the above-described embodiment, the display on the heart is mainly described. However, the above-described particle image may be used for displaying the carotid artery and other blood vessels. In the above embodiment, the display of the blood of the living body has been described. Of course, the same technique can be applied to the case of displaying the blood flow of an animal other than a human.

  According to the above-mentioned embodiment, the advantage that the details of a flow can be recognized rather than the conventional method is acquired. That is, in the conventional method, the velocity distribution is simply displayed in color in each time phase, but in this embodiment, the actual flow state can be visually represented by a plurality of particles that move independently. There is an advantage that various flows such as turbulent flow or vortex flow can be displayed in detail. Further, according to the present embodiment, since the two-dimensional velocity information is reflected on the image, it is possible to perform disease diagnosis more accurately than the conventional method. In the conventional method, the blood flow display is interrupted when the blood flow velocity decreases, but according to the present embodiment, it is also possible to continuously display particles even at a low speed region. Even when the blood flow stops and then moves again, it is possible to express it clearly as the movement of particles.

  In the present embodiment, the speed information calculated based on the received signal is not expressed by hue or luminance as in the conventional method, but the obtained speed information is used in the calculation of the display position of the particles. . Moreover, since the particles are configured as graphic elements, even if the measurement sensitivity of Doppler information is not so good, the shape of each particle itself can be clearly displayed. And since the whole state of a flow can be imaged easily, without displaying many particles, the advantage that the amount of calculations can be reduced in that case is acquired. In addition, the number of beams constituting one frame can be reduced as compared with the conventional method, and the number of transmission repetitions in the same beam direction can be reduced. As a result, the frame rate may be improved. Further, according to the present embodiment, even if the tomographic image is unclear, the blood flow display itself is clear, so that there is an advantage that the structure recognition of the tissue can be indirectly supported. For example, if there is an unclear aneurysm in the heart, it can be indirectly captured from the shape of the particle motion trajectory, and even if the valve is unclear, the motion is indirectly detected as particle motion. It is also possible to specify.

1 is a block diagram showing a preferred embodiment of an ultrasonic diagnostic apparatus according to the present invention. It is explanatory drawing which shows an example of a particle image. It is a figure for demonstrating the calculation method of a particle | grain display position. It is a figure for demonstrating the spring and disappearance of particle | grains. It is a figure for demonstrating the production | generation of particle | grains. It is a figure showing from production | generation of a particle | grain to extinction. It is a flowchart for demonstrating the display processing method of particle | grains. It is a figure for demonstrating the various display aspects about particle | grains. It is a figure which shows various brightness | luminance functions. It is a figure for demonstrating the display process with respect to the particle | grains which go to a heart wall. It is a figure for demonstrating eddy current and disappearance of a particle. It is a figure for demonstrating various operation states and various display methods. It is a figure which shows an example of a line display. It is a figure which shows an example of a vector display. It is a figure which shows an example of a three-dimensional particle image. It is explanatory drawing which shows another particle image. It is a figure for demonstrating the particle | grains with which the periphery was blurred, and its shape change.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Probe, 12 Transmission part, 14 Reception part, 16 Tomographic image formation part, 18 Vector calculation part, 22 Display processing part, 26 Vector image formation part, 28 Trajectory image formation part, 30 Particle image formation part, 38 Electrocardiograph, 46 left ventricle, 48 left atrium, 50 mitral valve, 52 aortic valve, 54 aorta, 61 particles, 62 particles.

Claims (25)

Based on a reception signal obtained by transmitting and receiving ultrasonic waves to and from a living body, a calculation unit that calculates a plurality of motion information for a plurality of points in the living body,
An image forming unit that forms an image representing blood flow in the living body as movements of a plurality of display elements based on the plurality of movement information;
An ultrasonic diagnostic apparatus comprising: The apparatus of claim 1.
Each display element is a particle,
The ultrasonic diagnostic apparatus, wherein the image forming unit is a particle image forming unit that forms a particle image as the image. The apparatus of claim 1.
The ultrasonic diagnostic apparatus, wherein the motion information is a two-dimensional or three-dimensional velocity vector. The apparatus of claim 2.
The arithmetic unit generates a velocity vector matrix as the plurality of motion information,
The particle image forming unit identifies a velocity vector corresponding to the kth particle position based on a k (where k is an integer) velocity vector matrix for each particle, and sets the identified velocity vector to the identified velocity vector. An ultrasonic diagnostic apparatus characterized in that a k + 1-th particle position is determined on the basis thereof. The apparatus of claim 2.
The calculation unit generates a velocity vector matrix as the plurality of motion information for each frame,
The particle image forming unit includes:
A specifying unit for specifying a velocity vector corresponding to a current particle position based on a current velocity vector matrix for each particle;
A determination unit for determining a next particle position based on the identified velocity vector for each particle;
An ultrasonic diagnostic apparatus comprising: The apparatus of claim 2.
The ultrasonic diagnostic apparatus, wherein the particle image forming unit includes a generation unit that causes a plurality of new particles to appear on a screen at predetermined time intervals. The apparatus of claim 6.
The ultrasonic diagnostic apparatus, wherein the predetermined time interval is a time interval corresponding to m (where m is an integer) frames. The apparatus of claim 6.
The ultrasonic diagnostic apparatus, wherein the predetermined time interval is a time interval corresponding to n (where n is an integer) heartbeats. The apparatus of claim 6.
The ultrasonic diagnostic apparatus characterized in that the generation unit causes the plurality of new particles to appear on the basis of a particle generation line defined in a screen. The apparatus of claim 6.
The ultrasonic diagnostic apparatus, wherein the generation unit causes the plurality of new particles to appear in a particle generation area defined in a screen. The apparatus of claim 5.
The particle image forming unit includes an updating unit that hides the particles displayed at the previous particle position and displays the particles at the current particle position for each frame. Ultrasonic diagnostic equipment. The apparatus of claim 5.
The particle image forming unit includes an updating unit that displays one or a plurality of afterimage particles for one or a plurality of particle positions in the past and displays a particle at a current particle position for each frame. A characteristic ultrasonic diagnostic apparatus. The apparatus of claim 2.
The ultrasonic diagnostic apparatus, wherein the particle image forming unit includes an erasing unit that erases specific particles satisfying a predetermined disappearance condition from the screen. The apparatus of claim 13.
The ultrasonic diagnostic apparatus according to claim 1, wherein the erasing unit erases the specific particles whose elapsed time from the generation time has reached the end time from the screen. The apparatus of claim 13.
The ultrasonic diagnostic apparatus, wherein the erasing unit individually erases specific particles that have reached the particle disappearance line from the screen. The apparatus of claim 13.
The ultrasonic diagnostic apparatus, wherein the erasing unit individually erases specific particles that are out of the particle display area from the screen. The apparatus of claim 13.
The ultrasonic diagnostic apparatus, wherein the erasing unit erases all particles that have been displayed on the screen all at once according to a heartbeat. The apparatus of claim 2.
The ultrasonic diagnostic apparatus, wherein the particle image forming unit includes a display processing unit that changes at least one of luminance and hue of each particle continuously or stepwise. The apparatus of claim 2.
The ultrasonic diagnostic apparatus, wherein the particle image forming unit includes a display processing unit that continuously or stepwise changes the form of each particle based on motion information corresponding to each particle. The apparatus of claim 2.
The ultrasonic diagnostic apparatus, wherein each particle is a computer graphic element having a clear outer shape or a blurred shape. The apparatus of claim 2.
In the real-time display mode, each particle moves at the same speed as the blood flow,
An ultrasonic diagnostic apparatus, wherein each particle moves at a speed according to a reproduction speed in a reproduction mode. The apparatus of claim 2.
An ultrasonic diagnostic apparatus, wherein a trajectory of each particle is displayed together with each particle. The apparatus of claim 2.
The particle image is a color image;
An ultrasonic diagnostic apparatus, wherein the particle image is displayed superimposed on a black and white tomographic image. Calculating a plurality of velocity vectors for a plurality of points in a two-dimensional or three-dimensional living space based on Doppler information obtained by transmitting and receiving ultrasonic waves to and from a living body;
Forming a particle image representing the motion of the fluid in the living body as a two-dimensional motion or a three-dimensional motion of a plurality of virtual particles based on the plurality of velocity vectors;
Displaying the particle image as a moving image;
An ultrasonic image display method comprising: The apparatus of claim 24.
The step of forming the particle image includes:
Identifying a velocity vector corresponding to the current particle position;
Determining a next particle position from the determined velocity vector;
Displaying a particle at the next particle position;
An ultrasonic image display method comprising: