JPS6272341A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic diagnostic apparatus that displays a tomographic image of a subject by transmitting and receiving ultrasonic waves.

[Technical background of the invention]

As shown in Figure 6, the ultrasonic diagnostic device transmits a fan beam BM from an ultrasonic transducer (probe), receives reflected echoes, and A/D converts the one-dimensional image data in the distance direction obtained at this time. After converting it into a digital signal through the converter 2, it is stored in one high-speed Batzer memory 3A and the previous data stored in the other high-speed buffer memory 3B is read out, and has a two-dimensional matrix structure that is displayed in XY coordinates. The image data 5 is written into an image memory (frame memory) 4, and the image data 5 stored in the memory 4 is read out and displayed on a television.

Next, a method for writing data read from the high-speed buffer memory 3 into the frame memory will be explained using FIG. 7. Generally, all pixels are filled by combining the following three methods, which will be explained in turn.

txt How to write sample data as is 7th method
As shown in Figure (a), when writing data obtained by transmitting and receiving ultrasonic waves in the direction of angle θ, regarding the frame memory address, in the X direction, ΔX = tan θ
Perform cumulative addition of , add the integer part and Xo, and get YJ
For the j direction, cumulative addition of ΔY-1 is performed, and the integer part and Yo are added.

In this way, a vector as shown in FIG. 2(b) can be generated. Data is read from the fast buffer according to its distance from the center point. On the other hand, in the conventional system, if the frame memory is an NXN matrix, the number of sample data to the high-speed buffer is N, so the position accuracy in the distance direction is only 1/2 pixel.

(2) Method of generating 4F interpolation vectors - above (1)
) alone, empty pixels with unfilled values will appear outside of the vicinity of the center point. An interpolation vector is required to fill in the empty pixels.

Basically, any number of interpolation vectors can be generated, but for convenience of explanation, the case of one interpolation vector will be described here.

According to (1) above, one more vector is added in the middle between the adjacent vectors. The data to be written is read from the sofa at high speeds corresponding to the left and right vectors, and then averaged. In this case as well, there will be an error of 1/2 pixels as in (1) above.

(3) Horizontal interpolation method For pixels that could not be filled even with the method of fil and (2) above, interpolation in the horizontal direction is performed. This is a method in which when there is an empty pixel during reading, interpolation is performed from the values of the pixels containing the values on the left and right sides of the empty pixel.

[Problems with conventional technology]

According to the prior art as described above, there are problems such as insufficient positional accuracy in the ill distance direction and (2) loopback due to horizontal interpolation. Each of these problems will be explained in detail below.

The characteristics of the ultrasonic sound field are expressed as shown in FIGS. 8(a) to (C). FIG. 5(a) shows the isolinear characteristics, FIG. 2(b) shows the characteristics in the azimuth direction, and FIG. 2(C) shows the characteristics in the distance direction. As is clear from each figure, the azimuth direction is gradual, but the distance direction is very steep. When a signal with such a characteristic is sampled with a width of one pixel and written with an error of 1/2 pixel allowed, a clear step occurs as shown in FIGS. 9(a) and 9(b). This phenomenon occurs because between adjacent vectors, one has an error of +1/2 pixels and the other has an error of 11/2 pixels.

This is the problem of insufficient position accuracy in the distance direction.

In addition, Fig. 10 shows the sound field at the position of θ-40° (same figure (
Explain the following problem by showing a)), the cross section in each direction, the position of the sample point with respect to it, and the state when linear interpolation is performed using the sample ((b) to (d) in the same figure). . As is clear from each figure, when interpolation is performed in the azimuth direction, the signal change is gradual, so there is little distortion due to interpolation, but in the case of horizontal interpolation, the signal change is sudden, so the original shape cannot be expressed and becomes distorted. This is the problem of folding due to horizontal interpolation.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and provides an ultrasonic diagnostic apparatus that can eliminate the lack of positional accuracy in the distance direction when writing data to a memory, and can solve the problem of aliasing when horizontal interpolation is used. The purpose is to

(Summary of the Invention) The present invention performs finer sampling than the conventional sampling period to obtain several times to several tens of times more data, and also provides sampling data that is located at the same distance from the center point as the writing pixel. By performing filter calculations based on , the position accuracy in the distance direction is improved, and by filling all pixels with the results obtained by filter calculations in the azimuth direction, aliasing due to horizontal interpolation is eliminated. It is characterized by this.

[Embodiments of the invention]

First, the principle of the present invention will be explained using FIGS. 2 and 3.

Conventionally, as shown in Figure 2, sample points (large black circles in the figure) were determined for the beam BM passing through the pixel P at approximately pixel intervals, and the data was written at the writing point (white circles in the figure) at the center of the pixel. , in the present invention, additional sample points (small black circles shown in the figure) are provided to make the sample points even smaller, and the starting point of the beam is the center of the pixel P (within the distance from ☆ to the distance between -). A filter operation is performed based on , and the center (white circle) of the pixel is filled in with the result. The Falta operation in this case is the following formula (1)
carried out by

As is clear from the above fl1 equation, what determines the Falter operation is the form of the Falter function h(x) and the range N of convolution. In this case, the Falta function changes infinitely depending on the design method, so it can be arbitrarily determined without being specified, and the convolution range N also changes infinitely depending on the scale of the scan and heart configuration. Since it is possible, it can be decided arbitrarily. The following will be explained with reference to FIG.

In the figure, for example, pixel P2. p3. p4 is a range through which the beam does not pass. In this case, the center point of each pixel is 0. ．．
03.0. Draw circular arcs, ,L,,l,4 corresponding to the distances from the beam generation point, respectively, and find the sample point S! located at the intersection of the adjacent beam BM, which intersects each line, and BMh, □1. , S2Z"'a -33' , Ss , Sm
A Falta operation is performed based on the data for each combination of ', and the result is calculated at the center position of each pixel, 0. ．． 0. ．． 0. I am trying to write it in. Similarly, for the pixel P1 through which the beam passes, data is written in the same arc at the center position O5 based on the data of the upper sample point S1°Sl'. Also, further external beams such as BMn,... and B
It is also possible to perform calculations on the sample point data of M, . . . and °ζ.

Here, the principle of selection of sample points on which the above-mentioned Falta calculation is based will be explained with reference to FIG.

The interval between adjacent beams BMIl and BM, , is set as ■7,
The writing target pixel is P3, its center position is 03, and the horizontal line passing through Ol and B1. Let the distance to the sample point S0 located at the intersection of BM, , be X, and the center position O
Let 83 be the sample point located at the intersection of the perpendicular lines drawn from 8 to the beam BM,, -)-, and let the deflection angle of the beam be θ, then the sample point S of the beam 11 Mll,,L. The distance AN r from to the other sample point S3 is determined by the following equation (2).

r= =xB ・sin θ ・+21 Note that the sample point S0 is a coordinate determined by cumulative addition in the X direction, and "" shown in the figure is a radius determined by cumulative addition in the radial direction.

The position of the sample point S can be found by adding the r to , which is determined by the above equation (2).

Similarly, sample points S,′ of adjacent beams BM, ,
is calculated, a filter operation is performed based on both data, and the result is written in the center 03 of the pixel P3. The filter coefficient in this case can be determined by inputting the above-mentioned Xa and 1 to determine the positional relationship between the writing point and the adjacent beam, and by providing this and the filter characteristics. As a result, data and coefficients can be output, so a convolution operation can be performed based on both, and the output can be written to the target pixel.

Furthermore, in the present invention, in order to prevent empty pixels from occurring, processing is performed to fill all pixels.

This will be explained with reference to FIG. Here, a case will be described in which everything between the beam BMll of n main ports and the beam BMゎ-1 of n-1 main ports is filled.

First, prepare two systems of vector generators, each with 4-1 in the Y direction and ΔX, 1 and ΔXn-1 in the X direction.
An address is generated by cumulatively adding each bit. After calculating the Y address Y, the X address Xll, and X1l-1, the calculation of Xn Xl-+ is performed to calculate the number of character pixels. After writing to (Y, X,), +1 is added to Xl, and writing is performed to (Y, X, , +1). After performing this operation Xn-X, -1 times, the new address is Y=Y+ 1 X11-Xゎ+ΔXl1 xa-, 4n-, 1ΔXl.

, and by repeating the above operation, the fifth
As shown in the figure, all pixels 1 to 36 in the range surrounded by the beam can be filled.

Next, an embodiment of a circuit for realizing the above principle will be described with reference to FIG. 1.

This circuit includes an A/II converter (AI') C) 12 that converts reflected ultrasound echo signals into digital signals, and a plurality of converters that store digital data of the scanned beam for each I line via a switch SW1. A high-speed sofa memory group 13 comprising high-speed buffer memories 13A to 13N.
and a filter operation unit group 15 comprising a plurality of filter operations '[H] 5A to 15N that multiply the data read out from each high-speed buffer memory via switch SW2 by a coefficient for filter operation, and each filter operation unit group 15. Xunki 15A~15
It has an adder 16 that adds the outputs of N, and a frame memory 14 that stores the output of the adder 16 and creates image data for one frame J. The address when data is written into the frame memory 14 is selected depending on the confidence from each circuit described below.

That is, the clock generator 17 which generates the basic clock signal of each circuit and the clock signal CK of the clock generator 1/-tor 17 are connected to the Y address output circuit which outputs the X address selection signal. The X address (n
) of the two clock signals from the cumulative adder 19 and the clock generator 17.
1 as the clear signal and the second clock signal cK2 as the clear signal.
The force counter 22 generates an output of +α by counting
and an adder 21 that adds the output +α of each counter 22 and the output ΔX of the X address cumulative adder 19 and outputs an X direction selection signal, and the X and X addresses are selected. It looks like this. Here, X −
The cumulative adder for f l'' has two systems, in addition to the aforementioned cumulative adder for the n-th beam,
There is an accumulation adder 20 for the n-th beam, which uses the clock signal CK and the unit selection signal Δ of the n-1th beam.
Cumulative addition with Xn-1 is performed. This is provided to realize the calculation shown in FIG. 4 described above, as will be explained next.

That is, by providing a subtracter 23 for subtracting the outputs of the two X-address cumulative adders 19 and 20, two adjacent beams BMn and BMll- as shown in FIG.

The center of the target pixel P, which intersects with 0. The distance of cotton through ill
, and this output I is sent to the filter calculator 15, which will be described later.
In addition to inputting it as a parameter of the comparator 24 of the next stage,
It is output to. In the comparator 24, the distance #L and the +1
The output flea α of the counter 22 is compared, and when the two match, a clear signal is output to the clock generator 17. As a result, the X addresses are sequentially selected up to the distance I4, but when cleared, they return to the original position and address selection is performed in relation to the next X address selection signal.

Further, the output child α from the +1 counter 22 is sent to the adder 25 together with the output of the cumulative adder 19 for the X address (n).
From this adder 25, the sample point S of the beam BM11 shown in FIG.

The distance Mxs from to the center 03 of the target pixel P3 is output. This output X, together with the beam deflection angle θ, is input to the XY-Rθ converter 26, and this converter 26 converts the distance #rm (sin θ・x , ) is calculated.

Addresses of the high-speed buffers 13A to 13N are selected by signals as described below. First, the clock signal CK from the clock generator 17.

and the sampling interval signal Δr to output the radius signal r shown in FIG.
The sample point S3 is selected based on the output of the adder 28.

Note that the sampling interval Δr is set to be several tenths finer than the conventional one.

On the other hand, the filter calculator 15 (for example, 15N) outputs the output signal L+ of the subtracter 23 and the output signal xB+ of the adder 25.
a coefficient determination circuit 15a whose filter characteristics are made by three people;
The filter coefficient determined thereby and the switch S
W, and a multiplier (convolution/i11γ unit) 15b that multiplies the data obtained through iM.
A filter operation is performed on the sample points subjected to IJe.

Since the operation of the circuit configured as described above has been described in the above explanation of the principle, only the +a essential operation thereof will be explained below.

When writing data to frame memory (FM>14)
The X and X addresses are selected based on the outputs of the address counter 18, the X address counter 19, and the adder 21. At this time, the subtracter 23 calculates the difference between the outputs of the two systems of X address cumulative adders 19 and 20, and the distance 91
, l is sequentially added to the X address until all empty pixels in , are filled.

Then, each time the X address is determined, a ζXY-Rθ converter 26
The value rB is calculated by adding this result and the radius r to the adder 28.
By using the addition result as a high-speed buffer address selection signal, sample data at the same radius as the write point of the target pixel is read out from several (at least two) surrounding high-speed buffer memories and a filter operation is performed. Let's do it. The filter coefficients are the values xB, 1. By inputting , the positional relationship between the target writing point and the adjacent beam can be known, so it can be determined by providing that value and the filter characteristics. A convolution operation is performed based on each filter coefficient and data, and the operation result is written at the center point of the target pixel.

After that, +1 is added to the X address to fill in the empty pixels in the horizontal direction sandwiched between the two beams. After repeating for the same distance, the next operation moves on to fill in empty pixels in the lower row in the vertical direction. In the manner described above, all pixels in the range surrounded by the two beams are filled.

〔Effect of the invention〕

As described in -1- below, in the present invention, all pixels are filled with the results obtained by filter calculation in the azimuth direction, so the signal to be interpolated changes gradually in the azimuth direction, so there is less distortion, and compared to the conventional horizontal interpolation method. This eliminates the problem of wrap-arounds such as those based on . In addition, the high-speed buffer memory can store all of the sample data at a period of a fraction to several tenths of a conventional pixel period, and store all of it. Since a plurality of high-speed buffers are targeted and the data of the sample point located at the same position as the distance of the center point ratio of the writing target pixel from the beam generation point among the buffers is used as sample data, the position accuracy in the distance direction is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIGS.
The figure is an explanatory diagram for explaining the present invention in detail, FIG. 6 is a schematic block diagram of a conventional ultrasonic diagnostic apparatus, and FIG. 7(a)
, (b) is a schematic diagram for explaining the beam scanning and memory writing method using the conventional device, and Fig. 8 (8) to (c)
is a characteristic diagram of the ultrasonic sound field to explain the conventional problems,
Figures 9(a) and (b) are the same (sampling and frame memory write operation diagrams for explaining the problems with the conventional device, and Figures 10 (a) to (d) are the same (problems with the conventional device). FIG. 3 is a diagram of ultrasonic sound field characteristics and a diagram of sampling and interpolation modes to explain the points. l...Ultrasonic probe, BM...Beam, 12...
・A/D converter, 13... High-speed buffer memory group, 14... Frame memory, 15... Filter operation unit group 16... Adder, 17... Clock generator, 18... X Address counter, 19.20.27...Address cumulative adder, 15a
... Filter coefficient determination circuit, 15b... Multiplier, sw, , sw, ... Switch. Funeral diagram 7 (b) 7F1, (Xo・Yo) Mi [-mi Europe, 1゛. To the nose; ゝ＼ ),. Figure 8 (G) East, Japan, Law, G-Yong / Cao Lan (b) Figure 10

Claims (1)

[Claims] In an ultrasonic diagnostic apparatus that transmits and receives an ultrasound beam radially, stores the obtained reflection data in an image storage means via a high-speed buffer storage means, and displays the data stored in the image storage means, a high-speed buffer is used. When data is stored in the storage means, sampling is performed finer than one pixel in the image storage means and stored, and the target pixel in a plurality of beams near the storage target pixel of the image storage means is sampled at the same distance. Ultrasonic diagnosis characterized by performing a filter operation based on data, performing a process of storing the result of this operation in a target pixel, and repeating the same process to store data in all pixels located between beams. Device.