JP3043862B2 - Ultrasound diagnostic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining blood flow information in a subject based on a reception signal obtained by receiving an ultrasonic wave transmitted into the subject and reflected in the subject. ,
The present invention relates to an ultrasound diagnostic apparatus that displays the blood flow information as a blood flow image by adding persistence to the blood flow information by a persistence circuit.

[0002]

2. Description of the Related Art In recent years, imaging of the inside of a living body using ultrasound has been popular in the field of medical diagnosis, and the state of blood flowing through an organ, that is, The flow is required as information for diagnosis, and an ultrasonic diagnostic apparatus is provided for this purpose.

A conventional ultrasonic diagnostic apparatus visually displays the state of blood flow by displaying an average flow velocity, flow velocity dispersion, and flow velocity power of a blood flow flowing through an organ such as a heart in a subject as a blood flow image. It can be caught. this is,
Changes in blood flow in an organ can be closely observed, which is very convenient for grasping hemodynamics in the organ.

[0004]

Recently, there has been an increasing demand for observing blood flow (micro blood flow) in fine blood vessels. The importance of how the current travels is important.

However, the blood vessels in the tumor are, for example, 1 m in diameter.
It is very thin, less than mφ, and it may be difficult to detect the blood flow flowing through the blood vessel within the spot of the ultrasonic beam, and even if the blood flow is once captured, the spot of the ultrasonic beam may be slightly In many cases, it will be missed just because of deviation.

[0006] In addition, one of the problems is that it is difficult to observe the micro blood flow because the flow velocity power is small. In order to overcome the above-mentioned problems, a conventional ultrasonic diagnostic apparatus is provided with a persistence circuit that realizes afterglow, and the entire blood flow image is made to have afterglow so that the blood flow detected instantaneously can be obtained. Even so, the display is made such that the luminance gradually decreases gradually, and observation of blood flow is facilitated.

However, the conventional persistence circuit is configured so that its time constant can be changed by operating the panel of the ultrasonic diagnostic apparatus, and if the necessary blood flow information is adjusted to have a proper afterglow, it becomes one to one. Even noise appearing on the image in a lump with about two pixels becomes afterglow and obstructs image observation. Also,
If the probe itself is moved during diagnosis, a large fake blood flow image appears on the screen due to the movement of the probe itself.In such a case, if conventional persistence is performed, even the fake blood flow image will be persisted Had taken on sex.

[0008] Further, when a minute blood flow is observed on a certain tomographic plane in an actual diagnosis, if there is a thick blood vessel near the blood flow, it is possible to observe only the minute blood flow. The large blood flow flowing through the thick blood vessels is detected at a low level by the side rope of the ultrasonic beam, and the minute blood flow and the large blood flow are displayed as if they were on the same tomographic plane. There is a phenomenon. In such a case, if conventional persistence is performed, a large blood flow image due to a large blood flow is displayed for a long time, and observation of a minute blood flow may not be possible in some cases.

Here, the basic configuration of a conventional ultrasonic diagnostic apparatus will be described with reference to specific examples of the above problems. FIG.
FIG. 1 is a block diagram showing a basic configuration of a conventional ultrasonic diagnostic apparatus.

In FIG. 1, a pulse signal is transmitted from a transmission circuit 11 to a plurality of transducers (not shown) constituting an ultrasonic probe 12 at predetermined timings, thereby transmitting a pulse signal to a subject (not shown). An ultrasonic pulse beam is transmitted. Here, for example, sector scanning is performed. The ultrasonic pulse beam is reflected by a substantial part of blood cells flowing through the subject, internal muscles, and the like, and is received by a number of transducers in the ultrasonic probe 12 to obtain a received signal. Input to the receiving circuit 13. The receiving circuit 13 is a circuit for delay-adding each received signal obtained by a number of transducers in the probe 12 so as to realize so-called dynamic focus. The reception signal subjected to the delay addition in the reception circuit 13 is input to the detection circuit 14 and the blood flow information detection circuit 15. In the detection circuit 14, envelope detection is performed, and thereafter, the signal is converted into a digital signal in the A / D conversion circuit 16, whereby a reflected signal from a substantial part such as a muscle is converted into an image in black and white gradation corresponding to the reflection level. Be transformed into This image is called a B-mode image, and this B-mode image is stored in the B-mode frame memory 17. Since the generation of the B-mode image is a known technique and is not the subject of the present invention, further detailed description will be omitted.

On the other hand, in the blood flow information detecting circuit 15, blood flow information is detected based on the received signal subjected to the delay addition in the receiving circuit 13. As a typical example of the blood flow information detection circuit, a color Doppler unit is widely used as a known technique. This color Doppler unit performs quadrature detection on an input received signal, removes a stationary echo (clutter component), performs an autocorrelation operation to obtain, for example, an average velocity of a blood flow for each portion, and obtains this on a visible image. The average velocity is represented by luminance, and the flow approaching the ultrasonic probe 12 is displayed in red, and the flow moving away from the ultrasonic probe 12 is displayed in blue.

A blood flow image obtained by the blood flow information detecting circuit 15 (hereinafter, this blood flow image is referred to as an “original image”) is temporarily recorded in a blood flow image frame memory 18 and then stored in the blood flow image frame memory 18. Data (pixel data) for each pixel is read out serially for each pixel from the frame memory 18, and is passed through a persistence circuit 19 to be described below.
0, the image is combined with the B-mode image recorded in the B-mode frame memory 17 and sent to the display circuit 21, where the combined image is displayed on a CRT display device (not shown). Here, the persistence circuit 19 is connected to a time constant setting means 22 for setting and changing the time constant.

FIG. 14 is a block diagram showing the basic configuration of a conventional persistence circuit, FIG. 15 is a diagram showing an example of original images successively input to the persistence circuit and having successive times, and FIG. 14, an operation explanatory diagram of the persistence circuit shown in FIG. 14, that is, a diagram showing a method of generating an image output from the persistence circuit (hereinafter referred to as "display image") when an original image is sequentially input It is. 15 and 16, each cell represents each pixel,
The number in each cell represents the value of the pixel data corresponding to that pixel. The value of the pixel data of the pixel in which no numeral is written in the cell is zero.

Although an actual ultrasonic diagnostic apparatus displays an image obtained by synthesizing a B-mode image and a blood flow image, a display operation of only a blood flow image will be described here for the sake of simplicity. The original image 1 has three massive patterns 1, 2, 3; the massive pattern 1 is a large blood flow, the massive pattern 2 is noise, and the massive pattern 3 is a minute blood flow of interest as an observation target. .

At this time, first, the pixel data of the original image 1 is sequentially read out from the blood flow image frame memory 18 shown in FIG. 13 for each pixel, input to the persistence circuit 19, and passed through the selector 191. Is input to the display image frame memory 192 and recorded as the display image 1.

Thereafter, the display image 1 (original image 1) recorded in the display image frame memory 192 is read out from the display image frame memory 192 and displayed on a CRT display device (not shown) via the display synthesizing circuit 20. However, together with this, each pixel data of the display image 1 (original image 1) read from the display image frame memory 192 is also sent to the multiplier 193. In the multiplier 193, the display image 1 read from the display image frame memory 192 is displayed.
Each pixel data of the (original image 1) is multiplied by a time constant (here, 0.4) set by the time constant setting means 22, and the multiplied pixel data is input to the selector 191 and the comparator 194. You. In synchronization with this, each pixel data of the original image 2 is sequentially input from the blood flow image frame memory 18 to the selector 191 and the comparator 194.

The comparator 194 displays the display image 1 (original image 1) read from the display image frame memory 192.
Is compared with the pixel data of the original image 2 for each pixel of which size is greater than or equal to 0.4 times the pixel data of the original image 2.
The display image 2 shown in FIG. 16 is recorded in the display image frame memory 192. Next, in the same manner as above, each pixel data of the display image 2 is multiplied by 0.4, and each pixel data of the original image 3 is compared with the size of each pixel corresponding to each other. The selected display image 3 is generated.

Here, in the case of the example shown in FIG.
The clumpy pattern 1 (see FIG. 15) in the (original image 1) has the afterglow property continuing to the display image 3 and thereafter, whereas the clumpy pattern 3 corresponding to the minute blood flow still remains in the display image 2 The light has disappeared. In addition, the block-shaped pattern 2 has persistence up to the display image 3 irrespective of noise.

For the above-described reasons, it is difficult to observe the blood flow flowing through a thin blood vessel with a conventional ultrasonic diagnostic apparatus, and it is often observed instantaneously but missed. .

The present invention has been made in view of the above circumstances, and has as its object to provide an ultrasonic diagnostic apparatus capable of easily observing a minute blood flow.

[0021]

According to the present invention, blood flow information in a subject is obtained based on a reception signal obtained by receiving an ultrasonic wave transmitted into the subject and reflected in the subject. The present invention relates to an ultrasonic diagnostic apparatus which obtains the blood flow information and displays the blood flow information as a blood flow image by adding persistence to the blood flow information by a persistence circuit. (1) Constituting the blood flow image A block pattern detecting unit that detects a block pattern representing a blood flow composed of one or a plurality of pixels adjacent to each other by extracting pixels having a pixel value equal to or greater than a predetermined threshold value from a large number of pixels; ) Total number of pixels calculating means for calculating the total number of pixels constituting each of the block patterns for each of the block patterns; and (3) the parser for each of the block patterns in accordance with the total pixel number of each of the block patterns. Characterized by comprising a constant changing unit when changing the time constant of afterglow chest circuit.

Here, a first setting means for setting a first predetermined number is provided, and the time constant changing means sets the time constant when the total number of pixels of each block pattern is equal to or more than the first predetermined number. Is preferably set to zero. A second setting unit that sets a second predetermined number, wherein the time constant changing unit sets the time constant to zero when the total number of pixels of each block pattern is equal to or less than the second predetermined number. It is also a preferred embodiment to configure so that

The time constant setting means for setting a function form of the time constant with respect to the total number of pixels is provided. The time constant changing means sets each block pattern according to the function form set by the time constant setting means. It is also a preferable embodiment that the time constant is changed in advance.

[0024]

In order to facilitate observation of the minute blood flow, the minute blood flow needs to be displayed on the screen for a longer time.
Therefore, a block pattern on the blood flow image is detected, and a time constant corresponding to the total number of pixels of each block pattern is given to the persistence circuit.For example, a block pattern with a small total number of pixels has a long afterglow time and a total pixel count. The large block pattern can display the minute blood flow for a long time by shortening the afterglow time.

The present invention has been completed on the basis of the above findings, detects each block pattern, obtains the total number of pixels constituting each block pattern, and obtains the persistence in accordance with each total pixel number. Since the time constant of the afterglow of the circuit is changed, it is possible to display a block pattern corresponding to a minute blood flow for a long time and other block patterns only for a short time. An ultrasonic diagnostic apparatus for obtaining a blood flow image suitable for observation of a micro blood flow such as a flow is realized.

Here, if the time constant is set to zero when the total number of pixels for each block pattern is equal to or larger than the first predetermined number, a large false blood flow image or the like that appears when the probe itself is moved is obtained. The blood flow disappears immediately, and a more easily viewable blood flow image can be obtained.

The total number of pixels for each block pattern is the second
If the time constant is set to zero in the case of the predetermined number or less, it is possible to eliminate a spot-like noise that is smaller than the minute blood flow, and to obtain a blood flow image that is more easily viewable.

Further, by providing a time constant identifying means for setting a time constant of afterglow of the persistence circuit with respect to the total number of pixels for each block pattern, the observation target can be set in accordance with the micro blood flow to be observed. By changing the time constant so that the blood flow can be most easily observed, an easy-to-use ultrasonic diagnostic apparatus having more excellent observation suitability can be realized.

In the above description, the time constant is changed so that the block pattern having a small total number of pixels corresponding to the minute blood flow has a longer time constant than the block pattern having a large total number of pixels corresponding to the large blood flow. However, the function form of the time constant with respect to the total number of pixels in the present invention is not limited to the function form in which the time constant becomes smaller as the total number of pixels becomes larger. For example, when observing a minute blood flow, when the massive pattern of the large blood flow and the massive pattern of the minute blood flow are adjacent to each other to form one massive pattern, the larger the total number of pixels of the massive pattern, the larger the size. A function form that is a constant is effective, and thus the present invention is not limited to a function form having a predetermined tendency.

[0030]

Embodiments of the present invention will be described below. FIG.
1 is a block diagram showing a basic configuration of an ultrasonic diagnostic apparatus according to one embodiment of the present invention. In this figure, components corresponding to the respective components of the above-described conventional ultrasonic diagnostic apparatus (see FIG. 13) are assigned the same numbers and symbols as the numbers and symbols shown in FIG. Is omitted.

FIG. 2 is a view showing an example of an original image in which time is continuous with each other, FIG. 3 is a view showing the total number of pixels for each block pattern shown in FIG. 2, and FIG. FIG. 6 is a diagram illustrating an example of a constant function.

In the ultrasonic diagnostic apparatus shown in FIG.
The pixel data sequentially read out for each pixel from the blood flow image frame memory 18 is input to the persistence circuit 23 and also to the block pattern detecting means 24.
As shown in FIG. 2, the block pattern detection means 24 detects each block pattern A, B, C, D,... For each of the original images 1, 2, 3,. Information on each of the block patterns A, B, C, D,... Is input to the total pixel number calculating means 25.
Then, as shown in FIG. 3, each block pattern A, B, C,
The total number of pixels for each D,. Information on the total number of pixels for each of the block patterns A, B, C, D,... Is input to the time constant changing means 26. The time constant changing means 26 obtains a time constant according to the total number of pixels according to a function as shown in FIG. 4, for example.
According to the obtained time constant, a display image in which the afterglow time constant is changed for each block pattern is obtained. Here, by providing the time constant characteristic as shown in FIG. 4, it is possible to display a block pattern having a small total number of pixels for a long time and display a block pattern having a large total number of pixels for a short time.

Hereinafter, embodiments of the characteristic components of the present invention will be described in detail. FIG. 5 is a circuit block diagram showing an embodiment of the block pattern detecting means shown in FIG. 1, and FIG. 6 is an explanatory diagram of the operation of the block pattern detecting means shown in FIG.

The original image is sequentially read out from the blood flow image frame memory 18 for each pixel and input to the binarization circuit 241 constituting the block pattern detecting means.

In the binarization circuit 241, the binary image is binarized to "1" when the value of each pixel data of the input original image is equal to or greater than a predetermined value, and to "0" otherwise. The binary image generated and stored in the binary image frame memory 2
42. Next, the binary image frame memory 242
, A binary image is raster-scanned for each image by a labeling circuit 243, and a so-called labeling process shown in FIG. 6 is performed by the following algorithm.

Step 1) The starting point of raster scanning is set to the upper left of the image. Step 2) The raster scanning is continued to find a pixel (i, j) whose value on the binary image is “1”, and the process proceeds to Step 3. If the pixel has reached the lower right pixel of the image, the process proceeds to step 6.

Step 3) If no label has been added to all the adjacent pixels of the pixel (i, j) of '1', a new label is assigned to the pixel (i, j) on the label frame memory 244. And return to step 2.

Step 4) If all the labeled pixels adjacent to the pixel (i, j) of “1” have the same label, the same label as the label is stored in the label frame memory 244. The process returns to step 2 for the pixel (i, j).

Step 5) If two or more different labels are attached to the labeled pixels adjacent to the pixel (i, j) of '1', the label with the smallest number is labeled. (I, j) on the frame memory 244. At this time, the different labels are originally the same label.
Record as shown in (c) and return to step 2.

Step 6) As shown in FIGS. 6 (b) to 6 (d), raster scanning is performed again according to the recording that the different labels recorded in step 5 are originally the same label. Rewrite the label.

The above operation is performed on each original image.

FIG. 7 is a circuit block diagram showing one embodiment of the total pixel number calculating means and the time constant changing means shown in FIG. 1, FIG. 8 is an explanatory diagram of the operation, and FIG. FIG. 5 is a diagram illustrating conversion characteristics.

The images obtained as described above and having different labels for each block pattern are sequentially read out from the label frame memory 233 for each pixel.
It is input to the label / total pixel number replacement circuit 251. In this label / total pixel number replacement circuit, based on the sequentially input label for each pixel, as shown in FIG. Calculated for each value. When the total number of pixels of each label value is calculated, as shown in FIG. 8C, the total number of pixels is written in all of the pixels having each label value, and the total pixel number frame memory 252 is written. Will be recorded.

The total pixel count / time constant conversion ROM 261
For example, a characteristic function shown in FIG. 9A is written in advance in the ROM. The total pixel count / time constant conversion ROM 261 stores the total pixel count frame memory 2 as shown in FIG.
The image in which the total number of pixels is written for each pixel, which is recorded in the pixel 52, is converted into an image in which each time constant is written and recorded in the time constant frame memory 262. Frame memory for time constant 26
Persistence according to the time constant of each pixel of the image recorded in 2 is performed. The total number of pixels in the pattern is converted to a time constant.

In the specific function as shown in FIG. 9 (b), the total pixel range W where the time constant is 0 and the time constant specific slope D can be varied from the panel of the ultrasonic diagnostic apparatus with a knob or the like. Alternatively, the relationship between the time constant and the total number of pixels may not be a straight line but may be a curve as shown in FIG.

FIG. 10 is a circuit block diagram showing an example of the persistence circuit according to the present invention. In this figure, the above-mentioned conventional persistence circuit (see FIG. 14)
The same reference numerals as in FIG. 14 denote constituent elements corresponding to the respective constituent elements, and a description of common points will be omitted.

The time constant for each pixel sequentially read from the time constant frame memory 262 is recorded in the second time constant frame memory 232 via the selector 231. The time constant of each pixel corresponding to the next original image is input to the selector 231 from the time constant frame memory 262, and the time constant of each pixel corresponding to this pixel is changed to the second time constant second time constant. The data is read from the frame memory 232 and input to the multiplier 193 and the selector 231. The multiplier 193 multiplies the image data read from the display image frame memory 192 by a time constant, as in the case of the conventional persistence circuit (see FIG. 14).
In this persistence circuit, the time constant read from the second frame memory for time constant 232 and changed for each block pattern is multiplied.

In the selector 231, the selector 191
When the pixel data input from the blood flow image frame memory 18 is selected, the time constant input from the time constant frame memory 262 is selected, and the time constant read out from the display image frame memory 192 by the selector 191 is selected. When the multiplied pixel data is selected, each pixel is switched by the comparator 194 such that the time constant read from the second frame memory for time constant 232 is selected. With the above configuration, in the persistence circuit, a display image is obtained in which a total number of pixels for each block pattern, that is, a time constant according to the size of each block pattern is obtained, whereby the micro blood flow is relatively small. It is possible to display for a long time and the large blood flow for a relatively short time.

FIG. 11 is a circuit block diagram showing a time constant changing means according to another embodiment of the present invention, and FIG. 12 is an operation explanatory diagram thereof. In FIG. 11, blocks corresponding to the respective blocks of the time constant changing means described above (see FIG. 7) are shown in FIG.
The same number as the number given to.

The total pixel count / time constant conversion ROM 261 includes:
As shown in FIG. 12A, when the total number of pixels is x and a predetermined constant is k, a time constant τ according to τ = exp (−kx) (1), that is, an index increases as the total number of pixels x increases. A time constant τ that decreases functionally is stored in advance. Here, a time constant τ for the total number of pixels x when k is fixed to a certain value K (for example, K = 1) is stored in the total pixel number / time constant conversion ROM 261. When it is changed, the function form of the time constant τ changes as shown in FIG. This total number of pixels / time constant conversion RO
From M261, a time constant τ is output for each pixel according to the total number of pixels input from the total pixel count frame memory 252.

The time constant τ output from the total pixel count / time constant conversion ROM 261 is input to the logarithmic operation circuit 263. In this logarithmic operation circuit, a logarithmic value of the input time constant τ, that is, logτ = log · exp (−Kx) = − Kx (2) is obtained.

This logarithmic value -Kx is multiplied by a multiplier 264 by a constant α set by a time constant setting means 265 realized by, for example, a setting dial. Here, since the time constant τ stored in advance in the total pixel count / time constant conversion ROM is for a fixed constant k = K, means for changing the function form as shown in FIG. Is multiplied by the constant α set by the time constant setting means 265. The logarithmic value -αKx multiplied by the constant α is input to the exponential operation circuit 266, where the operation of τ ′ = exp (−αKx) (3) is performed, and the new time constant τ 'Is required. The function form of the time constant τ ′ changes according to the constant α set by the time constant setting means 265, as in FIG. The time constant τ ′ obtained by the exponent calculation circuit 266 is input to the selection circuit 267. 0 is also input to the selection circuit 267.

On the other hand, the total pixel number x read from the total pixel number frame memory 252 is also input to the comparison circuit 268, and the comparison circuit 268 is also supplied to the comparison circuit 268 by a setting dial or the like in the same manner as the time constant setting means 265. FIG. 12 shows the first setting unit 269 and the second setting unit 270 realized.
A first predetermined number W1 and a second predetermined number W as shown in FIG.
2 is input. In this comparison circuit 268, W1 <x <
It is determined whether W2 or x ≦ W1 or W2 ≦ x, and the result of this determination is input to the selection circuit 267, whereby the selection circuit 267 sets W1 <x for each pixel.
If <W2, the time constant τ ′, and if x ≦ W1 or W2 ≦ x, 0 is selected and input to the time constant frame memory 262. Accordingly, as shown in FIG. 12C, the time constant of each pixel recorded in the time constant frame memory 262 is 0 or W when the total number of pixels x is x ≦ W1 or W2 ≦ x.
When 1 <x <W2, the time constant follows the above equation (3).

By configuring the time constant setting means 265 so that the constant α can be varied as described above, it is possible to execute persistence according to the operator's request. In addition, it is preferable to set the time constant to 0 for a granular noise appearing on an image or a large blood flow image appearing on the image by moving the ultrasonic probe itself, as described in the problem of the conventional apparatus. However, here, the operator can arbitrarily set the range of the total number of pixels x for performing persistence by configuring the predetermined numbers W1 and W2 by using a knob on the panel of the ultrasonic diagnostic apparatus, for example. You can do it.

In each of the above embodiments, the time constant becomes shorter as the total number of pixels becomes larger. However, as described above, the large blood flow and the minute blood flow are adjacent to each other to form one block pattern. In some cases, it may be better to increase the time constant as the total number of pixels is larger.In the present invention, the function form of the time constant with respect to the total number of pixels is limited to those having a predetermined tendency. However, various configurations can be made according to the purpose.

[0056]

As described in detail above, the ultrasonic diagnostic apparatus of the present invention detects each block pattern and obtains the total number of pixels constituting each block pattern for each block pattern. Since the time constant of persistence is changed for each pixel according to the total number of pixels, for example, an ultrasonic diagnostic apparatus capable of easily observing even a minute blood flow that is instantaneously detected is provided. Is achieved.

When the range of the total number of pixels for performing the persistence and the function form of the time constant with respect to the total number of pixels can be set from the outside, the persistence changed variously according to the purpose can be obtained. And a more sophisticated and more convenient device.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of an original image in which times are consecutive to each other;

FIG. 3 is a diagram showing the total number of pixels for each block pattern shown in FIG. 2;

FIG. 4 is a diagram illustrating an example of a function of a time constant with respect to the total number of pixels.

FIG. 5 is a circuit block diagram showing an embodiment of a block pattern detecting means shown in FIG. 1;

FIG. 6 is an operation explanatory diagram of the block pattern detecting means shown in FIG. 5;

FIG. 7 is a circuit block diagram showing one embodiment of a total pixel number calculating unit and a time constant changing unit shown in FIG. 1;

8 is an operation explanatory diagram of the circuit shown in FIG. 7;

FIG. 9 is a diagram illustrating conversion characteristics of the total number of pixels and the time constant.

FIG. 10 is a circuit block diagram of a persistence circuit according to the present invention.

FIG. 11 is a circuit block diagram showing a time constant changing unit according to another embodiment of the present invention.

FIG. 12 is an operation explanatory diagram of the time constant changing means shown in FIG. 11;

FIG. 13 is a block diagram showing a basic configuration of a conventional ultrasonic diagnostic apparatus.

FIG. 14 is a block diagram showing a basic configuration of a conventional persistence circuit.

FIG. 15 is a diagram illustrating an example of an original image in which times are consecutive to each other;

FIG. 16 is an operation explanatory diagram of the persistence circuit shown in FIG. 14;

[Explanation of symbols]

 Reference Signs List 18 blood flow image frame memory 23 persistence circuit 24 block pattern detecting means 25 total pixel number calculating means 26 time constant changing means 191 selector 192 display image frame memory 193 multiplier 194 comparator 231 selector 232 second frame memory for time constant 241 2 Value conversion circuit 242 Binary image frame memory 243 Labeling circuit 244 Label frame memory 251 Label / total pixel number replacement circuit 252 Total pixel number frame memory 261 Total pixel number / time constant conversion ROM 262 Time constant frame memory 263 Logarithmic arithmetic circuit 264 Multiplier 265 Time constant setting means 266 Exponent calculation circuit 267 Selection circuit 268 Comparison circuit 269 First setting means 270 Second setting means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-92345 (JP, A) JP-A-2-142545 (JP, A) JP-A-62-14837 (JP, A) JP-A-2-14837 211134 (JP, A) Japanese Utility Model Showa 50-15589 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61B 8/00-8/15

Claims (4)

(57) [Claims] 1. A method for obtaining blood flow information in a subject based on a reception signal obtained by receiving an ultrasonic wave transmitted into the subject and reflected in the subject, and obtaining the blood flow information in the subject. An ultrasonic diagnostic apparatus that adds afterglow to the blood flow information by a persistence circuit and displays the blood flow information as a blood flow image, wherein a pixel value equal to or greater than a predetermined threshold value is determined from a number of pixels forming the blood flow image. A block pattern detecting unit that detects each block pattern representing a blood flow composed of one or a plurality of pixels adjacent to each other by extracting pixels having the block patterns; and a block forming each block pattern for each of the block patterns. Total pixel number calculating means for calculating the total number of pixels; and time constant changing means for changing a time constant of afterglow of the persistence circuit for each of the block patterns according to each of the total number of pixels of each block pattern. An ultrasonic diagnostic apparatus comprising: 2. The apparatus according to claim 1, further comprising: a first setting unit configured to set a first predetermined number, wherein the time constant changing unit determines the time constant when a total number of pixels of each block pattern is equal to or greater than the first predetermined number. The ultrasonic diagnostic apparatus according to claim 1, wherein is set to zero. 3. The method according to claim 1, further comprising a second setting unit for setting a second predetermined number, wherein the time constant changing unit sets the time constant when a total number of pixels of each block pattern is equal to or less than the second predetermined number. The ultrasonic diagnostic apparatus according to claim 1, wherein is set to zero. 4. A time constant setting means for setting a function form of the time constant with respect to the total number of pixels, wherein the time constant changing means sets each of the block patterns in accordance with the function form set by the time constant setting means. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the time constant is changed.