JPS61176331A - 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 transmits ultrasound waves to a living body, detects changes due to differences in physical properties of the living body in response to ultrasound waves, and diagnoses the physical properties of the living body. It is related to the device.

[Technical background of the invention and its problems] Conventional ultrasonic diagnostic devices emit pulsed ultrasonic waves at a predetermined l!
JV4 was transmitted, and the reflected waves based on them were received and used for image processing.

However, since it is a pulse wave, there is a problem that if the pulse interval is widened to increase the depth of field, the number of images per second decreases and the temporal resolution deteriorates.Also, even if the pulse amplitude is increased, the problem of biological abnormalities Because of the linearity, there is a limit to the improvement of S/N, and historically there was a problem that it was difficult to generate a single pulse and the distance resolution deteriorated because several waves were continuous.

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is possible to improve distance resolution, increase the number of scanning lines on the screen, transmit multiple beams at the same time, and improve S/ It is an object of the present invention to provide an ultrasonic diagnostic apparatus that can improve N.

[Summary of the Invention 1 To achieve the above object, the present invention provides sequence code generation means for generating sequence codes with low autocorrelation and low cross-correlation;
a reference wave generation means for generating a reference wave; a sequence modulation means for modulating the reference wave with the sequence code; a plurality of imagers that transmit ultrasonic waves based on the modulated signal; and echoes from the subject. a plurality of receiving transducers that receive the signal; and echo demodulation means that demodulates the echo signal in relation to the sequence code;
The apparatus is characterized by comprising an image display means for displaying an ultrasound image based on the demodulated signal.

[Embodiments of the invention] The present invention will be specifically explained below using examples.

FIG. 1 is a block diagram showing an embodiment of the apparatus of the present invention. Reference numeral 1 denotes an M-sequence code generation unit, the details of which will be described later, which generates sequence codes with low autocorrelation and cross-correlation. 2 is a continuous wave generator that generates a continuous wave as a reference wave; 3 is an M-sequence modulator that modulates the continuous wave with the M-sequence code and outputs the modulated wave; 4 is a transducer driver that drives the transducer based on the modulated output. circuit, 5
6 is a plurality of transmitting transducers that transmit ultrasonic waves to the subject 11;
7 is a plurality of receiving transducers that receive ultrasound reflected signals obtained from the subject 11, and 7 is a device that demodulates the received signal (hair wave) obtained from the receiving transducer using the M-sequence code and outputs it.
8 is a scan converter for storing the echo demodulated signal in a subsequent room memory; 9 is a frame memory for storing image data; and 10 is an image display section for displaying an ultrasound image. Note that each of the vibrators 5 and 6 can be replaced with a single vibrator by shifting the transmission and reception timing.

Here, the M-sequence code generation section will be explained.

For information on how to generate M-sequence codes, please refer to "Spread Spectrum Communication System J (written by R, CQixon, Jatich Publishing)"
Although it is described in detail in Chapter 3, pages 56 to 99, the present invention focuses on utilizing the basic concept, so an outline will be explained below.

M sequence is the longest sequence (Maximal Linear
It is also called a coder and refers to the longest code sequence generated by a shift register or delay element of a certain length. Here, if we limit ourselves to binary shift register code sequence generators, if n is the number of stages of the digital register, then 2n
-1 bit is the length of the longest sequence.

Shift register code sequence generator (SRG, shirt)
register re(luence genira
tor) is composed of several stages of shift registers and a logic circuit that feeds back a logical combination of the states of the plural stages to the input of the shift register. A table of retrace connections for M-sequence generators with 3 to 100 stages has already been created. The autocorrelation of the M sequence is 2n-1 for O bit shifts, and -1 for other size transport shifts except for O±1 bit shifts.

An example of such a code sequence generator is shown in FIG. If a large number of code sequences are required, multiple feedback taps may be set. In that case, a combination with as little cross-correlation as possible is selected. For this purpose, the JPL distance measurement code, which is basically generated from the M sequence but cannot be called an M sequence in itself, and the Gold code are also effective.

Next, a specific example of the echo demodulator 7 that modulates the echo by W using the M-sequence code will be described.

The echo signal is converted into a digital signal by the A/D converter 13 and input to the buffer 14.

The plurality of polarity selection circuits 15a to 15m are controlled by a control circuit 18. The control circuit 18 sequentially shifts the M-sequence codes. Therefore, control circuit 1
If the signal from the control circuit 18 is "1", the polarity selection circuit transmits the output from the buffer 14 as is, and if the signal from the control circuit 18 is "O", it inverts the sign and transmits it. Cumulative 16a-16m connected to each stage
For example, as shown in FIG.
Therefore, it performs the function of adding the input and the value in the memory at that time and recording the output in the memory (accumulation). After sending out a series of M-sequence codes in this way, and after the echo signals from the required depth of the object disappear, the plurality of switch circuits 178 to 17m connected to each stage are sequentially switched. An echo signal similar to that of pulsed ultrasound but with high distance resolution can be obtained. If the analog signal is to be demodulated without A/D conversion, a CR integration circuit as shown in FIG. 5 is used instead of the accumulator. In this case, it is possible to change the degree of amplification of the integral by changing the value of the resistor R to lower the gain from a short distance and increase the gain from a long distance.

Next, the operation of the device will be explained.

The continuous wave generator 2 generates ultrasonic waves, and the continuous waves having the same frequency as JJ are phase-modulated in the M-sequence modulator 3 according to the M-sequence. That is, when the code sequence is "1", it is sent out as is, and when the code sequence is "0", it is phase-shifted by 180 degrees (the relationship between NJ and rol may be reversed).

The continuous wave modulated by the M-sequence modulator 3 is transmitted to the vibrator drive circuit 4.
The transmitting transducer 5 transmits the ultrasonic wave to the subject (for example, a living body) 11. After the echo signal is received by the receiving transducer 6, the echo demodulator 7 converts the beam direction as described above. Separate the reflected waves at each depth.

Thereafter, the beam is recorded in the room memory 9 by the scan converter 8 and displayed on the display section 10.

In the above operation, the ultrasonic waves modulated in the M sequence are reflected at each point and modulated into the M sequence. Therefore, they are @ in the receiving section. Therefore, if the polarity is switched and added using the M sequence code at a timing corresponding to each depth, only the echoes at that depth will be extracted because the autocorrelation of the M sequence has a large ratio between the shift amount O and other things. It will be. Furthermore, since they are added, even if the average output is small, the output after addition is large, so the same S/N can be obtained with a smaller average output than in pulsed ultrasound. Therefore, if the output is the same as that of pulsed ultrasound, the S/N will be improved.

Although the above explanation was about a method for obtaining an image, it goes without saying that the present invention can also be applied to measuring the sound velocity or attenuation characteristic of a subject using a single beam.

Furthermore, although the above description deals with the case where one beam is generated at a certain time, a plurality of beams may be generated at the same time. In other words, in a linear probe, by using different M-sequence codes from different transducers and code sequences with low cross-correlation, it is possible to increase the number of scanning lines with less mutual interference. On the other hand, in a sector probe, slightly different delay signals are given to each vibrator in order to give the beam a certain directionality, but if two or more combinations of these are created and each is given an M-sequence code with low cross-correlation, it is possible to The number of scanning lines in a sector can be increased.

In the above embodiment, the continuous wave was modulated with a digital code, but the DC signal may be modulated with a digital code.

In addition, other code sequences may be used instead of the M sequence as long as they satisfy autocorrelation and cross-correlation.

[Effects of the Invention] According to the present invention detailed above, since the number of scanning lines can be increased, the azimuth resolution can be improved, and since it is synchronized with the clock of the digital code, no ringing occurs and the distance resolution can be improved. , since the average output power can be increased, S
Accordingly, it is possible to provide an ultrasonic diagnostic apparatus having various advantages such as an improvement in /N and an increase in concentration resolution.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a code sequence generator, FIG. 3 is a block diagram of an embodiment of an echo demodulation section, FIG. 4 is a circuit diagram of an accumulator, and FIG. Figure 5 is a circuit diagram of an analog multiplier. DESCRIPTION OF SYMBOLS 1... Code sequence generation part, 2... Reference wave generation part, 3.
... code sequence modulation section, 4... vibrator drive circuit, 5.6
... Vibrator, 7... Echo demodulator, 8... Scan converter, 9... Frame memory, 10... Image display section, 11... Subject.

Claims (1)

[Claims] a sequence code generation means for generating a sequence code with low autocorrelation and cross-correlation; a reference wave generation means for generating a reference wave;
sequence modulation means for modulating the reference wave with the sequence code;
a plurality of transmitting transducers that transmit ultrasonic waves based on the modulated signal; a plurality of receiving transducers that receive echo signals from the subject; and echo demodulation means that demodulates the echo signals in relation to the sequence code. and an image display means for displaying an ultrasound image based on the demodulated signal.