JPH02246958A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To obtain a tomographic image having a high resolution with the same ultrasonic scanning frequency by calculating an interpolation value in including the phase of the echo signal of each scanning line. CONSTITUTION:The echo signal received by an ultrasonic transmitting and receiving means 1 is orthogonally converted with orthogonal signals Rx and Ry by an orthogonal detector 5, and converted orthogonal echo signals Sx and Sy are A/D-converted by A/D converters 7a and 7b. The signals Sx and Sy are stored in the positions indicated by a scanning line number LN and a sample number SN of real part and virtual part frame memories 10a and 10b, respectivley. Next, a real part interpolating means 11a obtains an interpolation scanning line from a row corresponding to the adjoining scanning line stored in the memory 10a and obtains it in the same way at virtual part interpolating means 11b. An absolute value arithmetic means 11C obtains the absolute value of a pair of complex image data to exist in the sam address of the memories 10a and 10b and the absolute value of a complex interpolation value interpolated by the interpolating means 11a and 11b. The scanning line of a real value and the scanning line of the interpolation value obtained by the arithmetic means 11c are read synchronizing to a display means 13 with a synchronizing signal generated by a display synchronizing signal generator 14.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasonic diagnostic apparatus used in the medical field, which scans while transmitting and receiving ultrasonic pulses to obtain tomographic images of a living body, which is a subject. .

BACKGROUND OF THE INVENTION Conventionally, ultrasonic diagnostic apparatuses have been widely used as means for non-invasively measuring tomographic information inside a living body.

This ultrasonic diagnostic device transmits ultrasonic pulses into the living body, receives echo signals reflected at points with different acoustic impedances, and when it reaches a predetermined depth, changes the ultrasonic transmitting/receiving position and direction and sequentially scans the body. By doing so, a two-dimensional tomographic image of the inside of the living body can be obtained. Generally, a television is used to display tomographic images, and the images are scan-converted to match the shape inside the living body, and the brightness is modulated according to the intensity of the echo signal.

Recently, the resolution has been improved by increasing the density of ultrasonic scanning lines, making it possible to obtain finer tomographic information. However, by increasing the scanning line density, the number of ultrasound transmissions and receptions increases, it takes time to obtain one tomographic image, and the frame rate decreases. In particular, when diagnosing a fast-moving object such as a heart, the movement cannot be observed unless a high frame rate is ensured. In addition, in electronic scanning diagnostic equipment, it is necessary to increase the arrangement density of minute ultrasonic transducers, and a large number of multiple ultrasonic transducers are required to transmit and receive at the same time. The ultrasonic probe is required to have even higher precision, and the transmitter/receiver circuit of the ultrasonic diagnostic apparatus itself that controls the ultrasonic probe also becomes large-scale.

Therefore, in general, an image is constructed using as few scanning lines as possible, and gaps between scanning lines are compensated for by interpolation processing to prevent deterioration of image quality.

As such a conventional ultrasonic diagnostic device, Japanese Patent Application Laid-Open No. 57
A configuration described in, for example, Japanese Patent No. 108681 is known.

This conventional ultrasonic diagnostic apparatus will be described below with reference to a schematic block diagram shown in FIG.

In the figure, 101 is an ultrasonic transmitting/receiving means for transmitting and receiving ultrasonic waves, and 102 is a scanning control means, which controls the source position and direction of the ultrasonic waves transmitted and received by the ultrasonic transmitting/receiving means 101. Reference numeral 103 denotes an ultrasonic scanning synchronization signal generator, which generates a frame synchronization signal FS which is a synchronization signal for starting ultrasonic scanning.
Then, a scanning synchronization signal LS, which is a synchronization signal that starts each transmission/reception, is generated. Reference numeral 104 denotes a drive circuit, which drives the ultrasonic transmitting/receiving means 1o1 with a pulse signal in synchronization with the scanning synchronization signal LS. 105 is a detector, which performs envelope detection (
AM detection). A sampling clock generator 106 generates a sampling clock SC in synchronization with the scanning synchronization signal LS. 107 is an A/D converter which samples the detected signal of the echo signal outputted by the detector 106 using a sampling clock SC and converts it into a digital value. A scanning line counter 108 is reset by a frame synchronization signal FS, counts the scanning synchronization signal LS, and outputs a scanning line number LN. 109 is a sample counter, which is reset by the scanning synchronization signal LS, counts the sampling clock SC, and calculates the sample number SN.
Output.

1fO is a frame memory, and A/D converter 10
The digital value obtained in step 7 is stored at the address indicated by the scanning line number LN and sample number SN.

Reference numeral 111 denotes an interpolation means, which interpolates between scanning lines of the tomographic image stored on the frame memory 110. A scan converter 112 converts the ultrasound scan format into a scan format for displaying a tomographic image. 113 is a display means for displaying a tomographic image, and 114 is a synchronization signal generator for generating a synchronization signal for the display means 113.

Next, the operation of the conventional ultrasonic diagnostic apparatus described above will be explained.

The ultrasonic scan synchronization signal generator 103 generates a frame synchronization signal FS at the scan start time, and thereafter generates a scan synchronization signal LS with a preset cycle and number of times. The scanning line counter 10B counts the scanning synchronization signal LS from the frame synchronization signal FS, and determines the scanning line number LN for which transmission/reception should be performed.
Output. The scanning control means 102 sets necessary setting values so that transmission and reception are performed on the scanning line corresponding to the scanning line number LN. As described above, the drive circuit 104 generates a pulse signal every time the scan synchronization signal LS is generated, and the ultrasonic transmitting/receiving means 101 driven by this pulse signal transmits ultrasonic waves onto the scanning line designated by the scan control means 102. Send. This pulse signal is reflected by the living tissue on the scanning line and returns as an echo signal, which is received by the ultrasonic transmitting/receiving means 101. This echo signal carries deep information over time from the time of transmission, and the reflected intensity becomes the amplitude of the echo signal.

FIG. 4(a) illustrates the scanning line format of ultrasound transmitted and received by the ultrasound transmitting/receiving means 101. In the figure, 1o1 is an ultrasound transmitting/receiving means, 301 is a living body as a subject, and 302 and 302 are two ultrasound reflectors included in the living body 301.

Arrows L1 to L8 indicate ultrasonic scanning lines, and transmission and reception are performed for each scanning line. The amplitude of the echo signal received by the ultrasonic transmitting/receiving means 101 is detected by the detector 105, and is input to the A/D converter 107 and converted into a digital value. This conversion in A/D converter 107 is performed by sampling clock SC. The sampling clock SC is a scanning line synchronization signal L from the sampling clock generator 106.
The count value counted by the sample counter 109, which is output continuously at a constant period in synchronization with S, is the sample number 8N, and serves as information in the depth direction. The amplitude information of the echo signal converted into a digital value is stored in the position indicated by the scanning line number LN and sample number SN of the frame memo 1J110 configured in a two-dimensional array.

FIG. 4(b) shows a tomographic image stored in the frame memory 11o in the ultrasonic scanning format shown in FIG. 4(a). The echo signal obtained on the scanning line L1 in FIG.
Similarly, the second to eighth rows of the frame memory 110 几2 to R
8 are sequentially written. The interpolation means 111 corresponds to each scanning line L1.
An interpolated scanning line for interpolating between -L8 is determined from adjacent scanning lines. For example, interpolated scan line L between scan lines L1 and L2
12, select the first row R1 and the second row R2 in which the scanning line L1 and scanning line L2 of the frame memory 110 are stored, and calculate the average,
or by weighted average.

The tomographic information on the frame memory 110 and the interpolation information obtained by the interpolation means 111 based on the tomographic information are first stored in the scan converter 112 and synchronized with the display means 113 using a synchronization signal generated by the display synchronization signal generator 114. and read it out. FIG. 4(C) is a tomographic image of the subject visualized on the display means 113. Arrows L1 to L8 in the figure are scanning lines of true values obtained by actually transmitting and receiving ultrasonic waves, and arrow L1
2, L23, . . . , L7B are scanning lines generated by interpolation, and scanning lines L12, . . .
..., L7B are the true value scanning lines L1~ that sandwich each of them.
This is calculated from L8.

As described above, by performing interpolation between scanning lines, even if the number of scanning lines is small, it is possible to eliminate missing scanning lines on the displayed tomographic image.

Problems to be Solved by the Invention However, in the conventional ultrasonic diagnostic apparatus described above, as shown in FIG.
Even though the number is 2,302, due to the interpolation process, it is displayed as if it is continuous as shown in FIG. 2(c). This occurs because the phase of the echo signal in each ultrasonic scanning line is not considered.
Particularly in the case of a fan-shaped method such as sector scanning, the scanning line density decreases as the distance increases, so the tomographic image projected in this area is not suitable for diagnosis.

The present invention solves the above-mentioned problems of the prior art, and by calculating an interpolated value including the phase of the echo signal of each scanning line, it is possible to interpolate an echo signal close to that obtained when actually transmitting and receiving. It is an object of the present invention to provide an ultrasonic diagnostic apparatus that can obtain tomographic images with high resolution while using the same number of ultrasonic scans.

Means for Solving the Problems The technical solution of the present invention for achieving the above object is as follows:
An ultrasonic transmitting/receiving means for transmitting and receiving ultrasonic waves, a scanning control means for controlling the direction and position of the ultrasonic waves transmitted and received by the ultrasonic transmitting/receiving means and scanning them, and an orthogonal transform for the echo signals received by the ultrasonic transmitting/receiving means. , orthogonal transformation means for outputting complex values of echo signals, and complex interpolation means for calculating interpolated values between scanning lines from echo signals converted into a plurality of adjacent orthogonal signals.

Further, it is provided with orthogonal signal generation means for generating a pair of orthogonal signals whose frequency is approximately equal to that of the echo signal and whose phases are different from each other by 90 degrees, and a quadrature detector is used as the orthogonal conversion means to perform orthogonal detection using the orthogonal signal. This is what I decided to do.

The apparatus also includes storage means for storing the complex values of the real part and imaginary part of the echo signal converted into the orthogonal signal.

Then, the complex interpolation means averages or weights the interpolated value of the desired point with the complex values of a plurality of adjacent echo signals in correspondence with the spatial position of the object on the ultrasound scan. demand.

According to the above structure, the echo signal received by the ultrasonic transmitting/receiving means is orthogonally transformed by the orthogonal transform means to output a complex value of the echo signal, and then converted into a plurality of adjacent orthogonal signals by the complex interpolation means. A complex operation is performed on the received echo signal to generate scanning lines by interpolation, and it is possible to interpolate between actually received scanning lines and display the result.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram showing an ultrasonic diagnostic apparatus in one embodiment of the present invention. In the figure, reference numeral 1 denotes an ultrasonic transmitting/receiving means for transmitting and receiving ultrasonic waves, and 2 denotes a scanning control means, which controls the source position and direction of the ultrasonic waves transmitted and received by the ultrasonic transmitting/receiving means 1. Reference numeral 3 denotes an ultrasonic scanning synchronization signal generator, which generates a frame synchronization signal FS, which is a synchronization signal that starts ultrasonic scanning, and a scan synchronization signal LS, which is a synchronization signal that starts each transmission and reception. Reference numeral 4 denotes a drive circuit, which drives the ultrasonic transmitting/receiving means 1 with a pulse signal in synchronization with the scanning synchronization signal LS. 16 is a quadrature signal generator, which is synchronized with the scanning synchronization signal LS and whose frequency is approximately equal to the echo signal frequency;
Orthogonal signals x and Ry whose phases differ by 90 degrees are output. Reference numeral 6 denotes a quadrature detector, which orthogonally detects the ultrasonic echo signal received by the ultrasonic transmitting/receiving means 1 using orthogonal signals Rx and Ry. A sampling clock generator 6 generates a sampling clock SC in synchronization with the scanning synchronization signal LS. 7a, 7t) are A/D converters that sample each of the real part and imaginary part detection signals output by the quadrature detector 6 using the sampling clock SC and convert them into digital values; 8 is a scanning This is a line counter, which is reset by the frame synchronization signal F8, counts the scan synchronization signal LS, and outputs the scan line number LN. 9
A sampling counter is reset by the scanning synchronization signal LS, counts the sampling clock SC, and outputs a sample number SN. A real part frame memory 10a stores the real part of the echo signal converted into a digital value obtained by the A/D converter 7a at an address indicated by a scanning line number LN and a sample number SN. Reference numeral 10b denotes an imaginary part frame memory, which stores the imaginary part of the echo signal converted into a digital value obtained by the A/D converter 7b at an address indicated by a scanning line number LN and a sample number SN. These real part and imaginary part frame memories 10a and 10b
Both have the structure of a two-dimensional array. 11a is a real part interpolation means, which interpolates between scanning lines of the tomographic image stored on the real part frame memory 10a. Reference numeral 11b denotes an imaginary part interpolation means, which interpolates between scanning lines of the tomographic image stored on the imaginary part frame memory 10b. 11c is an absolute value calculating means for calculating the absolute value of a complex tomographic image; 12 is a scan converter for converting an ultrasonic scanning format into a scanning format for displaying a tomographic image; 13 is a display means for displaying a tomographic image; 14 is a synchronization signal generator that generates a synchronization signal for the display means 13.

The operation of the above configuration will be described below.

The ultrasonic scan synchronization signal generator 3 generates a frame synchronization signal FS at the scan start time, and thereafter generates a scan synchronization signal LS with a preset cycle and number of times. The scanning line counter 8 counts the scanning synchronization signal LS from the frame synchronization signal F8, and outputs the scanning line number LN to be transmitted and received. The scanning control means 2 sets necessary setting values so that transmission and reception are performed on the scanning line corresponding to the scanning line number LN.

As described above, the drive circuit 4 generates a pulse signal every time the scan synchronization signal LS is generated, and the ultrasonic transmitting/receiving means 1 driven by this pulse signal transmits ultrasonic waves onto the scanning line specified by the scan control means 2. Send. This pulse signal is reflected by the living tissue on the scanning line and returns as an echo signal, which is received by the ultrasound transmitting/receiving means 1. This echo signal carries deep information over time from the time of transmission, and the reflected intensity becomes the amplitude of the echo signal.

FIG. 2(a) illustrates the scanning line format of ultrasound transmitted and received by the ultrasound transmitting/receiving means 1. In FIG. In the figure, 1 is an ultrasonic transmitting/receiving means, 201 is a living body as a subject, and 202 and 202 are two ultrasound reflectors included in the living body 201. Arrows L1 to L8 indicate ultrasonic scanning lines, and transmission and reception are performed for each scanning line. The echo signal received by the ultrasonic transmitting/receiving means 1 is orthogonally transformed by the orthogonal signals Rx and Ry in the orthogonal detector 6, and the transformed orthogonal echo signal S is obtained.
x and Sy are A/D converters 7a and 7b, respectively.
D-convert. Conversion in the A/D converters 73 and 7b is performed using a sampling clock SC.

The sampling clock SC is continuously outputted from the sampling clock generator 6 at a constant period in synchronization with the scanning line synchronization signal LS, and the count value counted by the sample counter e is the sample number SN, which is information in the depth direction. The A/D converted orthogonal echo signals Sx and SY are stored in the positions indicated by the scanning line number LN and sample number SN of the real part frame memory 11a and the imaginary part frame memory 11b, respectively, which are configured in a two-dimensional array.

FIG. 2(b) shows a tomographic image stored in the real part frame memory 10ax and the imaginary part frame memory 10b according to the ultrasonic scanning format shown in FIG. 2(a). Note that the rows R1 to R in the frame memories 10a and 10b
8 is specified by the scanning line number LN, and columns C1 to On are specified by the sample number SN. The real part of the echo signal obtained on the scanning line L1 in FIG. They are sequentially written in the second to eighth lines R2 to R8 of frame memo 'J10a.

On the other hand, the imaginary part of the echo signal is stored in the imaginary part frame memory 10b.
is written in the first row R1 of , and the subsequent scanning lines L2 to L
8, similarly, the second part of the imaginary part frame memory 1ob
The data is sequentially written in rows 2 to 8 of rows 8 to 8. The real part interpolation means 11a obtains interpolated scanning lines for interpolating between each scanning line L1 to L8 from the rows stored in the real part frame memo 1J10a and corresponding to adjacent scanning lines. For example, in order to obtain the interpolated scanning line L12 between the scanning lines L1 and L2, select the first row R1 and the second row R2 in which the scanning lines L1 and L2 of the real part frame memo IJ10a are stored, and Calculated by averaging or weighted average from the values stored in the same column. Similarly, in the imaginary part interpolation means 11b, each scanning line L1~
The interpolated scanning line interpolated between L8 is stored in the imaginary part frame memory 1.
0b and is determined from the row corresponding to the adjacent scanning line. The absolute value calculation means 11C is the real part frame memory 10a.
and the absolute value of a set of complex image data at the same address in the imaginary part frame memory 10b, and the real part and imaginary part interpolation means 11.
a, the absolute value of the complex interpolated value interpolated in 11b. The calculation process in the real part and imaginary part interpolation means Lfa, fib and the absolute value calculation means 11C is expressed as follows.

5xi=(al ・Sx1 +a2-8x2+-+an
jSxn)/n...(1) Syi = (al ・Syl +a2・Sy2+...+a
n+5yn)/n (2) Equation (1) shows the arithmetic expression of the real part interpolation means 11a,
8x1 to Sxn are the true values of the real parts of the echo signals near the point to be interpolated, and Sxi is the real part interpolated value. (2)
The formula shows the calculation formula of the imaginary part interpolation means 11b, and Sy1
~Syn is the true value of the imaginary part of the echo signal near the point to be interpolated, and Syi is the interpolated value of the imaginary part. In addition, n is the number of true values used for interpolation calculation, an integer of 2 or more, a1 to an
is the weighting factor.

Further, the absolute value calculating means 11c calculates the absolute value S of the complex true value and the complex interpolated value through the process of equation (3).

S = f four masters L〒shi ...... (3) To find the absolute value of the true value, use the real part and imaginary part of the echo signal actually obtained in equation (3) Sx and Sy. To find the absolute value of the interpolated value by substituting the value of
, Syi.

The scanning line of the true value and the scanning line of the interpolated value obtained by the absolute value calculation means 11c are then stored in the scanning converter 12 and synchronized with the display means 13 by the synchronization signal generated by the display synchronization signal generator 14. and read it out. FIG. 2(c) is a tomographic image of the subject visualized on the display means 13. Arrows L1 to L8 in the figure are scanning lines of true values obtained by actually transmitting and receiving ultrasonic waves, and arrows L12, L23, ..., L7B are scanning lines generated by interpolation. The scan lines L12, L23, . . . , L7B are calculated from the true value scan lines L1 to L8 that sandwich them.

By the complex interpolation method explained above, as shown in FIG. If the phase differs due to the difference in the properties of the
3) As is clear from the formula, the interpolated value Si becomes a small value,
As shown in FIG. 4(c), the two reflectors 202 and 202 can be separated at the interpolated scanning line L45. That is, an interpolated scanning line is created that is very close to the echo signal obtained when ultrasonic waves are actually transmitted and received on the scanning line indicated by arrow L45. The same applies to other scanning lines, and the resolution of tomographic images can be improved without increasing the number of ultrasound scans.

Effects of the Invention As described above, according to the present invention, the echo signal received by the ultrasonic transmitting/receiving means is orthogonally transformed by the orthogonal transform means to output the complex value of the echo signal, and then the complex value of the echo signal is output by the complex interpolation means. performs complex operations on the echo signal converted into an orthogonal signal, generates an interpolated scanning line that is very close to the scanning line obtained when actually transmitted and received, and interpolates between the actually received scanning lines and displays it. I can do it. Therefore, it is possible to display a tomographic image with a high resolution equivalent to that obtained by increasing the ultrasonic scanning line density.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention, FIG. FIG. 4 (a) is a block diagram schematically showing the ultrasonic diagnostic apparatus of
) to c) are explanatory diagrams of the interpolation processing operation in the above conventional example. 1... Ultrasonic transmitting/receiving means, 2... Scanning control means, 3
... Ultrasonic scanning synchronization signal generator, 4... Drive circuit,
5... Quadrature detector, e... Sampling clock generator, 7a, 7b... A/D converter, 8... Scanning counter, 9... Sample counter, 10a...
Real part frame memory, 10b... Imaginary part frame memory, 11a... Real part interpolation means, 11b... Imaginary part interpolation means, 11c... Absolute value calculation means, 12... Scan converter, 13 . . . display means, 14 . . . synchronization signal generator,
16...Orthogonal signal generator. Name of agent: Patent attorney Shigetaka Awano and one other person

Claims (4)

[Claims] (1) An ultrasonic transmitting/receiving means for transmitting and receiving ultrasonic waves, a scanning control means for controlling the direction and position of the ultrasonic waves transmitted and received by the ultrasonic transmitting/receiving means and scanning them, and an echo signal received by the ultrasonic transmitting/receiving means. An ultrasonic diagnostic device comprising orthogonal transformation means for performing orthogonal transformation and outputting a complex value of an echo signal, and complex interpolation means for calculating an interpolated value between scanning lines from the echo signal converted into a plurality of adjacent orthogonal signals. . (2) A claim comprising orthogonal signal generation means for generating a pair of orthogonal signals whose frequency is approximately equal to that of the echo signal and whose phases differ by 90 degrees from each other, and where the orthogonal transformation means is an orthogonal detector that performs orthogonal detection using the orthogonal signals. Item 1. Ultrasonic diagnostic device according to item 1. (3) The ultrasonic diagnostic apparatus according to claim 1 or 2, further comprising storage means for storing complex values of the real part and imaginary part of the echo signal converted into the orthogonal signal. (4) The complex interpolation means averages or weights the interpolated value of the desired point with the complex values of a plurality of adjacent echo signals in correspondence with the spatial position of the subject on the ultrasound scan. An ultrasonic diagnostic apparatus according to claim 1.