JPH10127634A - Ultrasonic diagnostic system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an unwanted side lobe contained in a beam pattern. SOLUTION: In a beam pattern 100 where a main beam A is directed in a prescribed observation azimuth, in addition to the 1st beam pattern 100, a 2nd beam pattern 102 is formed for removing a specified side lobe (a) contained in that pattern. The azimuth of a main beam B is made coincident with the specified side lobe (a) and its size is made coincident as well. By overlapping two beam patterns, namely, by operating difference between received signals provided by both the beam patterns, signal components caused by the specified side lobe (a) can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus and, more particularly, to reduction of side lobes (unwanted radiation) contained in an ultrasonic beam pattern.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus is an apparatus that forms, for example, a tomographic image or a blood flow image of a living body based on echo data (received signal) obtained by transmitting and receiving ultrasonic waves. In order to improve the image quality of such an ultrasonic image, it is necessary to improve the shape of the ultrasonic beam (transmitting beam and receiving beam).

However, in the normal beam pattern, unnecessary side lobes appear around the main beam (main pole). The side lobe is a set of sub-poles, and the grating lobe corresponding to the second main pole is one of the main causes of artifacts (false images). Therefore, in ultrasonic diagnosis, there is a strong demand to reduce specific side lobes such as grating lobes in order to improve the accuracy of disease diagnosis. Therefore, in a conventional ultrasonic diagnostic apparatus, it is performed to reduce the size of the ultrasonic vibration elements constituting the array transducer and increase the number of the elements.

[0004]

However, miniaturization of the vibrating element is accompanied by various restrictions, and an increase in the number of vibrating elements causes a problem of complicating the structure of the device and increasing the cost of the device. It is difficult to sufficiently reduce the side lobe even with a simple structural measure.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to effectively reduce side lobes inevitably present in an ultrasonic beam pattern.

Another object of the present invention is to generate a beam pattern for canceling a specific side lobe separately from a normal beam pattern, and to apparently reduce the specific side lobe by signal processing.

Another object of the present invention is to reduce specific side lobes without increasing the number of transmissions.

Another object of the present invention is to reduce specific side lobes, particularly in electronic sector scanning.

[0009]

To achieve the above object, the present invention provides an ultrasonic diagnostic apparatus for forming an ultrasonic image based on a reception signal obtained by transmitting and receiving an ultrasonic wave. Means for forming a first beam pattern while directing the main beam and obtaining a first received signal; and forming a second beam pattern while directing the main beam in the direction of a specific side lobe included in the beam pattern, Means for acquiring a received signal, and side lobe reducing means for subtracting the second received signal from the first received signal, wherein a specific side lobe of the first beam pattern and a main beam of the second beam pattern are It is characterized in that specific side lobes are reduced by using cancellation by virtual superposition.

According to the above configuration, when the first beam pattern is formed, the second beam pattern is formed simultaneously or at another time. Then, by the signal processing of subtracting the second reception signal from the first reception signal, the specific side lobe of the first beam pattern and the main beam of the second beam pattern are virtually superimposed and canceled, and the first beam pattern is Are canceled or reduced. That is, the signal component due to the specific side lobe is reduced. If this specific side lobe reduction processing is performed for each direction, as a result, artifacts can be reduced over the entire capturing area, and an ultrasonic image with good image quality can be constructed.

By the way, the specific side lobe of the second beam pattern is usually directed to the main beam direction of the first beam pattern, but the specific side lobe itself is very small, and the azimuth is originally intended. Since the observation azimuth is high, the influence of the side lobe of the second beam pattern does not substantially matter.

Note that the concept of the means for acquiring the first or second received signal includes a transmission control means and a reception control means (particularly, a phasing addition means).

In a preferred aspect of the present invention, the first received signal and the second received signal and the second received signal and the second received beam and the second received beam are arranged so that the size of the specific side lobe of the first beam pattern and the size of the main beam of the second beam pattern are made equal. At least one of the received signals is weighted.

As a result, it is only necessary to reduce the signal component due to the side lobe. Therefore, various methods for adjusting the size of the two beam patterns can be considered. According to the method of adjusting the level of the received signal, the adjustment at the time of transmission can be made unnecessary, and two beam patterns can be obtained by one transmission. Of course, transmission may be performed for each beam pattern, and two beam patterns may be acquired in a time-division manner. In a preferred aspect of the present invention, an array vibrator including a plurality of vibrating elements and a plurality of received signals from the plurality of vibrating elements are input, and the first beam pattern is formed by phasing addition of the received signals. First phasing addition means for generating the first reception signal, and a plurality of reception signals from the plurality of vibrating elements are input, and the second beam pattern is formed by phasing addition of each reception signal; And second phasing addition means for generating the second reception signal.
The first reception signal and the second reception signal are obtained in one transmission.

If simultaneous two-way reception is performed as described above, it is not necessary to perform a special transmission to reduce a specific side lobe, and a reduction in frame rate can be prevented. In this case, the transmission beam pattern is shared, and a transmission beam pattern in which the main beam is directed to the observation direction is usually formed. Then, after transmission, two reception beam patterns are virtually formed by the two phasing addition means, and signal processing for reducing specific side lobes is performed. In the transmission beam pattern, since ultrasonic waves having a certain intensity are radiated in the specific side lobe direction, there is no problem in forming the second beam pattern (second reception beam pattern).

In a preferred aspect of the present invention, the above-described specific side lobe reduction processing is executed according to electronic sector scanning. In a preferred aspect of the present invention,
A table is stored in which a relationship between the first beam pattern and the second beam pattern is stored, and electronic scanning is performed according to the table.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

First, the principle of the present embodiment will be described with reference to FIGS. FIG. 1A shows a first beam pattern 100 formed for a desired observation direction. This is an array vibrator 1 composed of a plurality of vibrating elements.
This is formed by electronically controlling 0, for example, and is a normal beam pattern. The first beam pattern 100 includes a main beam A and side lobes,
In particular, a specific side lobe a as a second main pole of the side lobes is shown. The specific side lobe a is a main cause of the artifact as described above, and it is required to remove it by some method.

Therefore, in the present embodiment, as shown in FIG. 1B, a second beam pattern 102 in which the main beam is directed in the same direction as the direction of the specific side lobe a is formed.
The second beam pattern includes a main beam B and a specific side lobe b, as in the second beam pattern. Here, it is desirable that the form of the main beam B, particularly its size, is made to match the side lobe a as much as possible.

As shown in FIG. 2, when the first beam pattern and the second beam pattern are virtually superimposed and the difference is obtained, the side lobe a is canceled by the main beam B, and as a result, Only the signal component in the main beam A direction can be extracted. Specifically, the first beam pattern 1
00 from the first received signal obtained by forming
The second reception signal obtained by forming the beam pattern is subtracted, and thereby, the difference between the beam patterns shown in FIG. 3 is virtually realized.

The first beam pattern 100 and the second beam pattern 102 can be formed in a time division manner. That is, each of them can be considered as a transmission / reception beam pattern. However, in this case, two transmissions are required for each observation direction, and the frame rate is reduced to half. Therefore, it is desirable to form two beam patterns in one transmission by providing two processing systems for the received signal. In this case, the beam pattern 100 shown in FIG. 1A corresponds to the transmission beam pattern and the first reception beam pattern, and the beam pattern 102 shown in FIG. 1B corresponds to the second reception beam pattern. Become. During transmission, a relatively large ultrasonic power is radiated also in the direction of the specific side lobe a, so that the second reception beam pattern can be formed without any problem. Regardless of which method is adopted, the reception sensitivity and the signal amplification are adjusted so that the level of the signal component due to the specific side lobe a and the level of the signal component due to the main beam B match as much as possible when the transmission and reception of the ultrasonic wave are comprehensively performed. Adjust the degree, etc., and weight the beam patterns.

Next, a specific configuration of an ultrasonic diagnostic apparatus to which a method of forming the first reception beam pattern and the second reception beam pattern in one transmission is described with reference to FIG.

FIG. 3 shows a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention. In this ultrasonic diagnostic apparatus, so-called electronic sector scanning is performed.

The ultrasonic probe 12 is provided with an array transducer 10. The array vibrator 10 includes a plurality of vibrating elements arranged in parallel, and performs the electronic sector scanning as described above. The transmission controller 14 controls the transmitter 1
6, transmission control for the array vibrator 10 is performed. Specifically, by setting a predetermined delay time to a transmission drive signal for each vibrating element, for example, as shown in FIG.
Is formed as a transmission beam pattern.

As described above, in the ultrasonic diagnostic apparatus of this embodiment, two beam patterns are formed by one transmission / reception, in other words, the transmission beam pattern is shared.

The received signals output from the respective vibrating elements constituting the array vibrator 10 are subjected to processing such as amplification in a receiver 18 and then input to a phasing adder 20 and a phasing adder 22, respectively. You. The phasing adders 20 and 22 are
The reception beam pattern is formed by setting a predetermined delay time for each reception signal. Here, the phasing adder 20 forms a reception beam pattern similar to the beam pattern 100 shown in FIG. 1A, while the phasing adder 22 produces the beam pattern shown in FIG. This forms a reception beam pattern similar to the pattern 102. Each of the phasing adders 20 and 22 includes a delay unit provided for each received signal and an adder for adding the delayed received signal.

The reception controller 23 controls the phasing adder 2 according to the beam pattern forming conditions stored in the table 25.
0 and 22 are controlled, and specifically, a delay amount is set for each received signal. Further, the reception controller 23 has a function such as weight control for each received signal.

The table 25 stores reception beam pattern setting conditions for each observation direction, that is, beam pattern setting such that the specific side lobe a and the main beam B as shown in FIG. Stores conditions.

The first received signal 200 output from the phasing adder 20 and the second received signal 202 output from the phasing adder 22 are input to the adder 24, respectively. Then, the second reception signal 202 is subtracted from the first reception signal 200, whereby the reception signal component is canceled or reduced by the target side lobe. That is, the adder 24 functions as substantial side lobe reduction means.

The received signal output from the adder 24 after the addition is detected by a detector 26 and then input to a digital scan converter (DSC) 28 to form, for example, a tomographic image. Then, the tomographic image is displayed on the TV monitor 38.

In the above embodiment, the difference between the first received signal 200 and the second received signal 202 is calculated before detection, but such a difference calculation can be performed after detection. If the difference calculation is performed before the detection, the difference calculation can be performed at a stage where the phase information is still included, so that a side lobe reduction effect can be expected.

In the above embodiment, a two-dimensional tomographic image is displayed on the TV monitor 38. However, signal processing for a two-dimensional Doppler image may be performed using the above-described configuration. Even in such a case, the same effect as described above can be obtained. When Doppler signal processing is performed, a configuration such as a quadrature detector or an autocorrelator may be provided after the adder 24.

Although the above embodiment is suitable for electronic sector scanning that is easily affected by grating lobes, the above principle can be applied to other electronic scanning methods. For example, the side lobe reduction processing described above may be applied to electronic linear scanning, convex scanning, and the like.

[0034]

As described above, according to the present invention,
Side lobes contained in the ultrasonic beam pattern can be effectively reduced. Further, according to the present invention, a beam pattern for canceling a specific side lobe can be formed separately from a normal beam pattern, and unnecessary signal components caused by the specific side lobe can be removed by signal processing. Further, according to the present invention, specific side lobes can be reduced without increasing the number of transmissions.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first beam pattern and a second beam pattern.

FIG. 2 is a diagram showing superposition of a first beam pattern and a second beam pattern.

FIG. 3 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention.

[Explanation of symbols]

10 array transducer, 14 transmission controller, 20, 22
Phasing adder, 23 reception controller, 24 adder, 26
Detector, 100 first beam pattern, 102 second beam pattern.

Claims (5)

[Claims] 1. An ultrasonic diagnostic apparatus for forming an ultrasonic image based on a reception signal obtained by transmitting and receiving an ultrasonic wave, comprising: forming a first beam pattern while directing a main beam in a desired direction; Means for acquiring a signal; means for forming a second beam pattern while directing a main beam in a direction of a specific side lobe included in the first beam pattern; and means for acquiring a second received signal; And a side lobe reducing means for subtracting the second received signal, wherein a specific side lobe of the first beam pattern and the second side lobe are reduced.
An ultrasonic diagnostic apparatus characterized in that specific side lobes are reduced by using cancellation by virtual superposition of main beams of a beam pattern. 2. The apparatus according to claim 1, wherein the first reception signal and the first reception signal are arranged so that a size of a specific side lobe of the first beam pattern is equal to a size of a main beam of the second beam pattern. An ultrasonic diagnostic apparatus, wherein at least one of the second received signals is weighted. 3. The device according to claim 1, wherein an array vibrator including a plurality of vibrating elements, and a plurality of reception signals from the plurality of vibrating elements are input,
A first phasing addition unit that forms the first beam pattern by phasing addition of the respective reception signals and generates the first reception signal; and a plurality of reception signals from the plurality of vibrating elements are input;
A second phasing addition means for forming the second beam pattern by phasing addition of each received signal and generating the second received signal; and wherein the first reception signal and the second reception signal are transmitted in one transmission. An ultrasonic diagnostic apparatus for acquiring a reception signal. 4. The ultrasonic diagnostic apparatus according to claim 1, wherein said specific side lobe reduction processing is executed in accordance with electronic sector scanning. 5. The ultrasonic diagnostic apparatus according to claim 1, further comprising a table storing a relationship between the first beam pattern and the second beam pattern, wherein electronic scanning is performed according to the table. .